B. Michiels, M. Steenackers, V. Steenackers, and J. Van Slycken
Institute of Forestry and Game Management, Geraardsbergen, Belgium
In the framework of an IUFRO program (R. Koster-collection, NL), IBW began in 1973 a P. trichocarpa provenance trial with about 2,000 seedlings from 64 different seed sources in British Columbia, Oregon, Washington, and California. After frequent observations to study susceptibility to rust, form, and vigor, the original number was reduced to 337 seedlings at the end of the 1980s.
In the same year, in the context of a long-term planned P. trichocarpa breeding program, 27 intraspecific crossings were realised (2 F1 and 25 F2). The selection of the parent trees was based partly on the photoperiodic adaptation to the latitude, stem form and straightness, Melampsora larici-populina tolerance, and Xanthomonas populi resistance. Various combinations of both resistant and susceptible parents were used. The reaction of the 1-year-old seedlings to Xanthomonas populi was tested by artificial infections. One year after infection, the percentage of field-resistant clones within the different families ranged from 10 to 99%. In total, 2,310 seedlings of a total of 9,225 showed a sufficiently high resistance to bacterial canker.
Recently the remaining seedlings (about 220 in the provenance trial and 375 in the intraspecific breeding trial) were evaluated again. Data for the different provenances/crossings regarding survival, rust resistance, canker resistance, growth, form, and other characteristics are given and discussed in detail. Vegetative propagation of selected trees has begun, and where already possible trees have been tested again for rust and canker resistance. All results will give more information concerning different important characteristics for further breeding work, choice of parents for controlled intraspecific and interspecific crossings, and elimination of non-selected trees to create a seed orchard based on strongly selected trees. Meanwhile, these trials became very productive seed plantations, allowing further steps in the breeding program. A special goal of the trial will be to demonstrate the domestication possibility of an introduced species and the value of the use of seedlings in west European poplar plantations. Seedlings of the best families or synthetic populations can be used at different spacing, i.e., 3 x 3 m up to 8 x 8 m, for biomass production or for timber production.
T.M. Mills, B. Robinson, S. Green, and B. Clothier
Environment and Risk Management Group, HortResearch, Private Bag 11030, Palmerston North, New Zealand
Potentially, poplars and willows may be used for the in situ decontamination of soils polluted with Cadium (Cd), such as pasturelands fertilised with Cd-rich superphosphate fertiliser. Poplar clones, Kawa (Populus deltoides x P. yunnanensis NZ 5006) and Argyle (P. deltoides x P. nigra NZ 5015) and Tangoio willow (Salix matsudana x S. alba NZ 1040) were grown in soils containing a range (0.6 to 60.6 mg/kg dry soil) of Cd concentrations. The willow clone accumulated significantly more Cd (9 to 167 mg/kg dry matter) than the two poplar clones (6 to 75 mg/kg), which themselves were not significantly different. As Cd uptake from the soil is reportedly influenced by transpiration rate, a more detailed study into the differences in water-use characteristics between the species was initiated using one poplar (Kawa) and one willow (Tangoio). Lysimeter experiments allowed measurement of the daily water-use differences between the two species. Periodic measurements of stomatal conductance were also made. The area of the plant where Cd accumulates was also investigated for poplar and willow. Willow showed consistently higher daily water use than poplar when given on a per leaf-area basis and stomatal conductance (gs) values were consistently higher for the willow compared to the poplar. Leaf age has a profound influence on Cd concentration in both species indicating water-use history as a contributor. Despite similar distribution patterns between species, the old leaves of willow (high water use) had higher concentrations of Cd than poplar (low water use). This study indicates that although biomass production is a key contributor to bioaccumulation, water-use characteristics and stomatal response function also play a key role.
A. Jafari Mofidabadi and A.R. Modir-Rahmati
Research Institute of Forests and Rangelands, Genetic and Plant Physiology Department, P.O. Box 13185-116, Tehran, Iran
An in vitro method was used to produce hybrid poplar plants between Populus alba L. and P. euphratica Oliv. in two directions. Developed ovaries and ovules were isolated from P. alba L. female branches, that had been pollinated with P. euphratica pollen grains by using twig and pot breeding techniques. The same procedures were carried out for isolation of developed P. euphratica Oliv. ovaries and ovules that had been pollinated with Populus alba L. pollen grains on mature trees.
Isolated ovaries and ovules of both crosses were then transferred to growth regulator free, half concentrated MS agar medium for embryo germination. Fourteen-days-old Populus alba L. ovary and ovule embryos produced the highest number of plantlets, while 45-days-old ovary and ovule embryos of P. euphratica Oliv. were necessary to obtain hybrid plants. A maximum of two to three plantlets were observed in both Populus alba L. and P. euphratica Oliv. ovary culture. Ninety percent of pollinated P. euphratica Oliv. and Populus alba L. ovules successfully produced plantlets, whereas the efficiency of pollinated ovaries in producing plantlets was 70% for Populus alba L. and 67% for P. euphratica Oliv. Plantlets were cultured in the same medium in jars before being transferred to potting soil. Seventy-five interspecific P. alba L. x P. euphratica Oliv. plants and 26 P. euphratica Oliv. x Populus alba L. hybrid plants were successfully acclimatised in the greenhouse.
S. Molnár, I. Peszlen, K. Szojákné Török, and P. Göbölös
University of West Hungary, Sopron, Bajcsy-Zs. 4., Hungary 9400
Besides the better known Populus x euramericana clones, there is an increasing interest in some of the native Hungarian Leuce hybrids (Populus canescens), the so-called "grey poplars" for timber production in Hungary. They are natural hybrids of Populus alba and Populus tremula, and the trees have a wide range of morphological characteristics. One of their advantages is that they have a high tolerance to adverse environments, such as dry site conditions. Therefore, the planting of grey poplars is currently preferred over Pinus species in the arid Hungarian Great Plain. The Wood Science Institute launched an extensive investigation on wood properties of grey poplars 2 years ago. The main goal of this research is to explore and identify hybrids of the best wood quality. Some results of this still ongoing project are presented in this paper. From the Kelebia Forestry Company, a total of 20 sample trees from three stands were selected and harvested for the assessment of macroscopic, microscopic, and physical properties. The following characteristics were measured: percentage of bark, sapwood, and heartwood; growth ring width; radial changes of fibre length; moisture content, density, and dimensional changes of sapwood and heartwood. In general, the investigated grey poplar hybrids from all the three stands produced wood with favourable properties that could be converted to lumber and utilised in the production of pallets.
B.D. Moltzan1, B. Thomas1, A. Robertson2, and B. Ward2
1Department of Renewable Resources, University of Alberta, Edmonton, AB T6G 2H1, Canada
2Alberta Pacific Forest Industries Inc., Box 8000, Boyle, AB T0A 0M0, Canada
Melampsora leaf rust is an important foliar disease of hybrid poplar and aspen in nurseries and young plantations. Early season defoliation can reduce productivity and increase susceptibility to other pathogens or environmental stress. Resistance has been identified and attempts to exploit natural resistance genes in the poplar genome may lead to improved stock of high yielding trees for fibre. Infection type (IT) rating was evaluated on 10 hybrid poplars and 12 superior aspen clones under controlled conditions using two Melampsora species indigenous to Alberta. A range of IT was observed in response to each species including the hypersensitive response (0), necrotic fleck (1), necrotic fleck with pustule (2), chlorotic halo with pustule (3), and pustule only (4). Other parameters such as size of uredinia and day to pustule formation (slow rusting) will also be evaluated. Results from this investigation will assist in selection of improved hybrid poplar and aspen for use in north-eastern Alberta.
Brian W. Moser
Wildlife and Pest Management Co-ordinator, Potlatch Corporation, Hybrid Poplar Program, P.O. Box 38, Boardman, OR 97818, USA
Studies of wildlife use of hybrid poplar plantations in North America are limited. I documented raptor use of a 7,050 ha complex of hybrid poplar plantations during the winter of 1999-2000. Diurnal and nocturnal raptors were surveyed in the interiors and along the edges of various-aged plantations, as well as in surrounding agriculture and shrub-steppe habitat. A total of 11 species of diurnal raptors and 5 species of nocturnal raptors were observed during this study. In 1999, relative abundance (#birds/km) of diurnal raptors was greater (P<0.01) along the edges of 5-year-old stands in comparison with surrounding shrub-steppe habitat, the interiors of the 1- to 4-year-old stands, and the edges of 1- to 3-year-old stands. Owl detections in the surrounding shrub-steppe habitat were lower (P<0.034) than along the edges of 5- year-old, 4-year-old, and 1-year-old stands. In addition, owl detections on the edges of the 5-year-old stands were greater (P<0.048) than along the edge of the 3-year-old stands, as well as inside the 5- and 1-year-old stands. During 2000, relative abundance of diurnal raptors was greater (P<0.033) along the edges of 6-year-old stands in comparison to the interiors of 3- to 5-year-old stands. No differences (P>0.05) were observed for owl detections among treatment means during 2000. No difference (P>0.05) in overall abundance of diurnal raptors was detected between 1999 and 2000. However, overall owl detections were significantly lower (P<0.05) during the winter of 2000. The differences in owl detections between 1999 and 2000 surveys could be a result of disturbance due to harvesting activities during 2000. Annual variation in owl abundance might also be explained by environmental factors such as temporal variation in prey abundance. The results of this study suggest that industrial-sized hybrid poplar plantations may be important habitat for wintering raptors in this region, especially along the edges of older trees. Consideration should be given to wintering raptor populations when scheduling harvest activities in industrial plantations. Long-term monitoring may be needed to accurately interpret trends in winter raptor use of hybrid poplar plantations.
Marie-Josée Mottet and Pierre Périnet
Direction de la recherche forestière, Forêt Québec, 2700 rue Einstein, Sainte-Foy, Québec, G1P 3W8, Canada
Septoria canker causes severe damage on susceptible clones in hybrid poplar trials in Québec. The pathogen Septoria musiva is found in natural stands, causing only leaf spots on Populus deltoides. Its distribution is limited to the southern part of Québec where only resistant clones are now planted. With the extension of intensive poplar cultivation, the possible expansion of this stem canker disease in Septoria-free zones is presently under investigation. Both standard artificial inoculation procedure and field test monitoring in the canker-conducive area allow efficient canker resistance screening of large populations. Since 1986, an inoculation method has been carried out for preliminary screening of clones. The method consists of placing mycelium plugs on fresh leaf scars on stump sprouts. Clone responses observed 3 months later are comparable to ratings of canker damage in field tests. A new selected population, developed for the southern Québec breeding region, is now under evaluation. After a preliminary screening in a nursery trial, a high-density farm-field test of 2,693 selected clones, representing 92 families and 20 hybrid types, was planted in 1997 in Saint-Ours, near Sorel, for Septoria evaluation. After 3 years, 70% of the clones were infected by S. musiva. The hybrids MB (P. maximowiczii x P. balsamifera), MN (P. maximowiczii x P. nigra), DM (P. deltoides x P. maximowiczii), EM (P. x euramericana x P. maximowiczii), and IM (P. x interamericana x P. maximowiczii) had the highest ratio of resistant clones to total number of clones per hybrid. The ratio was 63% for the MB hybrid and varied from 39 to 44% for the others. The MT (P. maximowiczii x P. trichocarpa) hybrid was the most susceptible (7% resistant) followed by MI (P. maximowiczii x P. x interamericana), MM, and MJ (P. maximowiczii x P. x jackii). In 1999, after two growing seasons, 408 resistant clones were selected from the Saint-Ours trial for artificial inoculation according to standard procedure. Approximately 80% of the 408 clones were still resistant after Septoria inoculation. In addition to Aigeiros hybrids, the MB, MN, EM, IM, and DM hybrid types have a high potential for vigor and canker resistance in southern Québec. In the future, the breeding program will continue to be largely oriented towards selection for Septoria resistance.
Hans-J. Muhs
Institute of Forest Genetics, Grosshansdorf, Germany
The Council Directive of the European Union (66/404 EEC) for the marketing of forest reproductive material has been amended and was put into force recently. This directive regulates the production and the marketing of forest reproductive material within the European Community. It contains a great number of revisions and new aspects, some of which are also relevant for poplars as far as they are covered by this Directive. The main new aspects can be summarised as follows:
While the Directive 66/404 EEC is valid only in the European Community, the OECD-Scheme (1974) for the control of forest reproductive material moving in international trade is a scheme optional for all countries. This scheme has also been amended (but not adopted yet), and the draft version is congruent in main features with the revised EU-Directive. Thus international trade will be facilitated. All amended regulations will bring more bureaucracy for breeders, traders, and users, but also much more clarity and certainty of the rules. Breeders will profit from them because their products from advanced breeding methods can be marketed easily.
Hans-J. Muhs, M. Kaldorf, and M. Fladung
Institute of Forest Genetics, Grosshansdorf, Germany
In 1996 a field trial was established using eight transgenic lines derived from two aspen clones Brauna 11 (female) and W52 (male) of Populus tremula and one hybrid aspen clone Esch5 (female) of P. tremula x tremuloides. Six transgenic lines contain the 35S-rolC-construct and two transgenic lines contain the rbcS-rolC-construct. The field trial is designed as a block model consisting of 4 replications x 8 plots (transgenic lines) x 8 plants per plot including controls. The rolC-construct affects several phenotypic traits such as small growth habit small leaves increased number of internodes, and early flushing with 35S-rolC, and normal growth habit and leaves, but light green colour of the leaves with rbcS-rolC. The 35S-promoter is a constitutive one, while the rbcS-promoter is light inducible. This system is used to analyse the expression of the phenotypic traits during 4 years and the stability/instability of the transgenes. First results show a normal variation of phenotypic traits within a line, but differences between lines in some cases. While most lines seem to be expressing stability, some reversions have been found in two lines, which occurred in different frequencies (6[line #1] resp. 26 [line #4] out of 32). Twigs or leaves had reverted to the wild-type character. Reverted parts of the plant found in the previous year remained in the reverted phase in the following year. Molecular analysis of all plants and especially of the reverted parts of the plant followed on different levels, using PCR, southern, and northern experiments. Preliminary results give evidence that the status of the inserted construct in reverted parts can be absent, inactive, or partly lost or inactive. The next step was to investigate the T-DNA structure and features of the flanking region to find reasons for instability. There is evidence for rearrangements at the insertion-region causing the gene silencing in line #1 by using inverse-PCR and sequencing techniques. This would explain the frequently observed reversions resulting in instability in that line due to intrachromosomal base-pairing leading to double-stranded loops of single-stranded DNA during unitotic cell divisions. In line #2, the reason for the observed instability is unknown so far. Additional investigations deal with the status of mycorrhiza (types and degree of colonisation). Four types occur frequently, while 10 further types are rare. There was found a widely homogenous distribution among transgenic and control plants except for one type, which showed differences between transgenic lines. Furthermore, this model will be used to analyse a possible horizontal gene transfer from the host plant to the mycorrhiza-fungus.
T. Evan Nebeker1, Michael D. Warriner1, and Elwood R. Hart2
1Department of Entomology & Plant Pathology, Mississippi State University
2Department of Entomology, Iowa State University, Ames, IA 50011, USA
Within the industry of fibre farming, a key insect pest, the cottonwood leaf beetle (CLB) Chrysomela scripta F, is of concern. The CLB is considered to be the most widespread defoliator of Populus in the United States and can act as a limiting factor in the establishment of plantations or in the economic accumulation of biomass in the first few years of growth. In the south-eastern United States where Populus is intensively cultivated, one or more insecticide applications are applied annually in an attempt to control the CLB. Yet, guidelines for monitoring CLB populations at the landscape level have not been developed.
To assist in the timing of this monitoring effort, we assessed the developmental rate of the CLB in terms of degree-days. To do this, we compiled developmental rate estimates from our own work as well as from others. To calculate degree-days for the CLB population in Mississippi, USA, we used a lower developmental threshold (LDT) of 53°F or 11.8°C. During the 1999 field season in Mississippi, observations were made on the emergence of overwintered adults and the progression of stages from egg to first generation adult (preimaginal development) for testing our prediction system. Diapausing adults emerged after accumulating approximately 136 degree-days, from December 1998 to March 1999. The first egg masses appeared after 162 degree-days (March 18-25, 1999). First generation adults appeared after 443 degree-days (April 29, 1999). To determine the developmental time from egg to adult for the first generation in the field, we adjusted the degree-day estimates by subtracting degree-days accumulated prior to oviposition of egg masses. Total preimaginal development was determined to be 281 degree-days. Therefore, the generalisation can be made that first generation adults appeared approximately 281 degree-days after oviposition of egg masses. This model and associated data will be used to predict overwintering emergence and population development at the Mississippi site as well as at a fibre farm in Missouri during 2000. Results will be presented in the poster along with subsequent generation predictions.
G. Newcombe
University of Idaho, Moscow, ID 83844-1133, USA
Sphaerellopsis filum is thought to be a "nonspecific fungal hyperparasite of rust" that occurs on most of the thousands of rust fungi in temperate zones and the tropics alike. Sphaerellopsis filum is the subject of biocontrol efforts directed at leaf rust in intensive willow plantations in the UK, and yet how it obtains nutrients and causes senescence is unknown. By providing insight into whether S. filum obtains its nitrogen from Melampsora or from Populus, nitrogen isotope ratios (δ15 N values) may allow us to confirm that S. filum is a hyperparasite rather than an opportunistic necrotrophic pathogen of Populus. The specificity and omnipresence of S. filum are also at issue. The author has collected S. filum on Melampsora on Populus on the coastal plain in the south-eastern U.S., for the past 3 years. However, its occurrence elsewhere in North America on Populus is unrecorded and dubious. Even in western Kentucky and nearby states, S. filum is absent although other putative hyperparasites are present. Could it be that some populations of Melampsora are resistant to S. filum from Populus deltoides from the coastal plain? Could this explain its restricted distribution? This hypothesis is being tested with Melampsora isolates from across North America using a newly developed co-inoculation assay.
Tom Nichols
Boise Cascade, Minnesota Fibre Farm Assessment Project Manager, International Falls, MN, USA
Mechanical and chemical weed control treatments were compared in a 4 x 2 x 2 factorial experiment replicated three times on each of two sites. Pre-emergent herbicide comparisons were trifluralin, oxyfluorfen, linuron, and a trifluralin + imazaquin mix. Post-emergent strategies compared separately the effects of treatment within rows (herbicides) and treatment between rows (discing and herbicides). Each sub-sub-plot included 30 trees of each of three clones: DN34, DN182, and NM6. Weed height and cover were estimated every 2 weeks for each plot, and for the area around each tree in October, when tree height and diameter were measured.
A midseason weed measurement, around August 1, provided the best relationship between weed levels and growth. Comparisons suggest little effect of weeds until a threshold was reached, and then growth dropped off geometrically. All of the pre-emergent herbicide treatments kept weeds below this threshold through mid-August. Following this, the weed levels increased in the linuron and trifluralin treatments. Both within-row and between-row treatments, separate or combined, kept weed levels well below the threshold throughout the season when used with any of the pre-emergent herbicides. Very few weeds grew into the trifluralin + imazaquin plots, but tree growth in these plots was severely reduced from apparent phytotoxicity. The benefits from the within-row treatment to tree growth varied; growth improved on one site, but results were mixed on the other site. The between-row treatments stunted tree growth significantly (but was not apparent in the field), apparently from soil compaction.
Nils-Erik Nordh
Department of Short Rotation Forestry, Swedish University of Agricultural Sciences, P.O. Box 7016, S-750 07 Uppsala, Sweden
The future use of willow (Salix spp.) as a source of bioenergy in Sweden depends on a high and sustainable yield. Dense plantations of short-rotation forests are bound to undergo different stages of development as a result of varying intensity of competition for light both between individual stools and between shoots within individual stools. If competition is intense, there is an enhanced risk of stool mortality. The timing of harvest in relation to stand development, therefore, is of great importance to maintain a vital stand.
A field trial with 12 willow clones was established on a clay soil in central Sweden (59º N) in spring 1990. A double-row spacing system was used and 20,000 cuttings per hectare were planted manually. The trial contains four replications, each with 12 monoclonal 10 x 10 m subplots. Measurements of living standing biomass (i.e., stem diameter) were performed annually with non-destructive methods on individual stools from 1991 to 1997. A coarse estimation of dead biomass was performed in 1997. Annual assessments of survival were carried out from 1990 to 1997. The trial has been coppiced twice; the first time in winter 1993/94 and the second in winter 1997/98. On both occasions a commercial harvester was used.
The initial average stool survival after the establishment season differed among the clones and varied between 72% and 99%. During the subsequent 3 years in the first cutting cycle, almost no stool mortality was recorded and shoot mortality was low. At the end of the second cutting cycle, the average stool survival of the different clones varied between 53% and 88%. High stool mortality was observed from 1996 to 1997. During the first cutting cycle, increased annual production of living biomass was observed every year and the standing biomass in 1993 varied between 25 and 38 t dry-matter per hectare (tDM/ha). During the second cutting cycle, the annual production peaked in the second year in all except two clones. In 1997, the standing living biomass of the different clones varied between 31 and 39 tDM/ha . Eight of the twelve clones had a higher production in the second cutting cycle. The average standing dead biomass for all clones was 8 tDM/ha in 1997.
The results show that during the first cutting cycle the competition between stools was low and stool survival was therefore high, mainly depending on cutting quality. In the later part of the second cutting cycle, both stool and shoot mortality increased as a result of competition. This mortality also affected biomass production through a decrease of annual increment at the end of the second cutting cycle. To maintain a high sustainable yield, high stool survival is important. The relatively high mortality between 1996 and 1997 indicates that the harvest was carried out too late. The expected increase of production during the second cutting cycle was verified by measuring and including standing dead biomass.
Phanuel O. Oballa
Kenya Forestry Research Institute, P.O. Box 20412, Nairobi, Kenya
Populus ilicifolia (Eng.) Rouleau is a tree species endemic to Kenya. The species marks the southernmost natural distribution of the genus. It is distributed along the Ewaso Nyiro, Tana, and Athi Rivers, from latitudes 1o N to 3o S, longitudes 37o E to 41o E, and from sea level to about 1,200 m. The geographic range of the species is in arid and semi-arid areas of the country, where the mean annual rainfall ranges from 200 to 800 mm. Rainfall is bimodal with peaks in March - May and in October - December. The mean diurnal temperatures vary between 17o o and 35o C.
The species is typically riverine, but its existence is highly threatened by direct exploitation, agropastoral activities, and other development projects such as dam construction that take place along the rivers. The last survey conducted on the species indicated an immediate need to determine the genetic diversity, collect germplasm, and identify other matching sites for ex-situ conservation.
Isoenzyme studies conducted using samples from seven widely separated sites along the three main river systems indicate that there is low genetic diversity within and among populations. Within its natural range, the species regenerates poorly naturally. Studies conducted on propagation techniques indicate that with some improvement in growth conditions the species can be raised successfully both from seeds and cuttings. Mature seeds collected and sown within 1-2 days germinated well under hot and humid conditions. A rooting success of up to 60% on stem cuttings was realised under hot glasshouse conditions. With identification of good matching sites, plantations can be established to conserve the species and to increase its economic use.
Sasa Orlovic, Vojislav Guzina, and Branislav Kovacevic
Agricultural Faculty, Poplar Research Institute Novi Sad, Antona Cehova 13, P.O. Box 117,
21000 Novi Sad, Yugoslavia
This paper presents the results of research on physiological characters of rooted cuttings of eight black poplar clones (four Populus x euramericana and four Populus deltoides) in three field experiments on different soil types (humofluvisol, fluvisol f. loamy, and fluvisol f. sandy). Physiological characters measured were net photosynthesis, dark respiration, and leaf area. At the end of the vegetation period, the main plant growth elements measured were diameter, height, and biomass. The results of the research on physiological processes of poplar clones showed a high interclonal variability of most elements and processes of species under study. Statistically significant differences between clones and insignificant differences between repetitions, medium and high coefficients of heritability in a broad sense, indicate that the majority of study characters are controlled by genetic factors that result in considerable specificity of some clones. The statistically significant interaction genotype x environment, in the greatest number of characters, indicates the different reactions of clones to the site, i.e., soil type. Also, the rank of the clones in three experiments was not the same, so the interaction clone x environment existed in all the characters under study.
The quotient of variance of genotype x environment and variance of genotype, for dark respiration, and rooted-cutting diameters and heights was higher than 0.5, and therefore the interaction genotype x environment must be considered during selection. A strong genetic correlation with the elements of growth and biomass was shown especially for leaf area. Further, primarily experimental research will be directed to define the variability of these characters within species and in later ontogenetic stages. The results indicate that it could be possible to introduce a desirable level of physiological processes to the hybrids by which the effects of hybridisation can be enhanced.
Faruk S. Özay
Poplar and Fast Growing Forest Tree Species Research Institute,
41001-Izmit, Turkey
Willows have been cultivated on the borders of fields and on stream banks since ancient times. These trees have been used both as construction wood and fuel. As demand for wood has increased, willow plantations on large areas have been established as in poplar cultivation. In recent years, several experiments have been performed on willow cultivation.
In this study, the harmful insects that attack the native or exotic willows in the Marmara region were determined. Sixty-seven insect species that attack willows in this region were identified. These species belong to 28 different families and 5 orders. The ecological conditions that increase the effect of insect damages were also determined.
Pan Mingjian, Tu Zhongyu, Guo Qun, and Wang Baosong
Forestry Academy of Jiangsu, Nanjing, Dongshanqiao, 211153, China
Willows (Salix L.) are very important forest species in China for various purposes. They are rich in species and gene resources, and they are easy to cross and vegetatively propagate. In nearly 40 years, remarkable progress has been made in the selection of excellent clones for timber production, osier clones for coppice as wicker work material, and ornamental trees. Willows are typical short-rotation species because of early fast growth. Their wood is white and has even structure. According to our study, willow wood would be of excellent for pulp. Although its wood is light and soft, it has relatively high mechanical intensity. In particular the impact toughness and the bend strength are fairly high, so it could be used as qualified pitwood. Our breeding practices illustrate that by developing interspecific/intraspecific hybridisation among the species of Salix and clone breeding, excellent clones could be selected for high quality pulpwood or pitwood.
The weeping varieties of S. babylonica, S. matsudana, and S. alba are often planted as ornamental trees, specially S. babylonica, which is much more important than the others in China. Five excellent clones with "golden weeping" branches have been successfully selected from the artificial hybrids of S. babylonica x S. alba. Five excellent "silver bud" clones have also been selected from shrub or bush artificial hybrids. Willow has wide adaptation. Its heterosis from hybridisation is obvious. The F1 progenies, of these artificial hybrids whose parents come from different provenance, would have strong heterosis and wider ecological adaptability. Willows have strong tolerance, such as high tolerance to dampness, and drought and moderate tolerance to salt. They also have the ability to absorb pollution substances. As a result, in willow genetic improvement programs from now on, fast-growing clonal selection should be put forward continually for intensive culture and industrial use. On the other hand, tolerance should become the main genetic improvement goal in selecting those clones that could be extensively cultured and achieve a certain economical income. These clones will be useful in establishing various ecological forests, protecting plantations, conserving water controlling soil erosion, and in providing environmental afforestation and ornamental forests. The benefits of willow plantation shall finally be clear.
Margaret M. Payne and Lawrence K. Miller
Boise Cascade Corporation, Cottonwood Fibre Farm, P.O. Box 500, Wallula, WA 99363, USA
Boise Cascade Corporation (BCC) established intensively managed fibre farms in eastern Oregon and Washington (USA) in 1991, and currently operates 7,350 ha on five locations in the region. Plantations are maintained in a stress-free condition including irrigation, pest and weed control, and fertilisation. Rotation length is 6-7 years. The trees are utilised to provide high quality short fibre furnish to BCC's Wallula, Washington, Pulp and Paper Mill, where the chips are used in the manufacture of uncoated freesheet. The fibre farm cottonwood tree improvement program started in 1993. At the outset, trees were selected based solely on growth rate. More recently emphasis has been placed on wood properties such as wood density, pulp yield, lignin content, fibre length, and fibre dimensions. The breeding program is composed of both intraspecific breeding for parental line improvement and interspecific breeding for F1 hybrid generation. Parental line improvement starts with breeding within Populus trichocarpa, P. deltoides, and P. nigra according to a positive assortative mating scheme. Pure species progeny are evaluated for 2 years, and the top 1% based on diameter and height growth are selected for placement in a breeding archive. Some of these selections will flower at age 3, allowing additional intraspecific and interspecific crosses to be made. Production of elite F1 hybrids begins with interspecific crosses between primarily these same three taxa. Selections are made from the hybrid progeny at age 1 and 2, which are placed in a replicated clone test. Elite hybrids are selected for commercial deployment based on the evaluation of age 2 height and diameter growth, followed by wood and fibre quality determination. Clones selected for commercial deployment are then serially propagated to create sufficient plants for a stoolbed. Using this approach, new hybrid clones are established 6 years after the initial cross is made. Thus far, 5 new clones have been released for commercial deployment. To date, significant genetic improvement has been achieved in wood density and several fibre characteristics.
Pierre Périnet1 and Daniel Robert1
Ministère des Ressources naturelles, Forêt Québec
1Direction de la recherche forestière, 2700 rue Einstein, Sainte-Foy, PQ, G1P 3W8, Canada
2Direction de la production des semences et des plants, 880 Chemin, Sainte-Foy, PQ, G1S 4X4, Canada
With the world-wide increase in demand for fibres, hybrid poplar is now recognised as an alternative source of wood supply. In 2001, the expected volume of poplar planting stock produced annually in Québec will be around 1.8 million plants and should exceed 2.5 million by 2005. Bareroot plants show improved initial height growth, quickly get out of reach of browsers, and are easily planted (30 cm depth) when sites are adequately prepared. Successful plantations could also be established with cuttings, using plastic mulch strips and protection against browsers. Although, in that case, site selection and preparation requirements are very high (plowing, discing, and cultivation to allow successful unrolling of the mulch). In addition to environmental concerns, the costs of plastic mulch and installation took us away from that scenario. As bareroot plants are used for poplar planting stock in Québec, operational production of 1-0 rooted cuttings was developed involving five provincial nurseries: Berthier, Grandes-Piles, Normandin, Saint-Modeste, and Trécesson. Both stoolbeds and cutting-donor plants are used as sources of cutting material. Stoolbeds are established in each nursery for 8 to 10 years. One-year-old sprouts are harvested in late fall, cut into cuttings, and stored for winter at -2ºC. Cutting donors grown for 1 or 2 seasons in nursery beds are also used as an alternative source of material. They could yield a second crop after being cut back in fall. Cutting donors allow a rapid build-up of new clones but require larger bed areas compared to stoolbeds. For the regular cutting production, 12- to 15-cm-long cuttings with a 5-15 mm diameter are mechanically planted in nursery beds in May, at the rate of four cuttings per metre and five rows per bed (1,5 m wide), for a total of 20 plants per bed metre. Cuttings are irrigated in the first weeks and later on if needed, according to soil moisture data. Basic fertilization (N-P-K-Mg- Ca) is applied at a rate varying from 25 to 75 kg N/ha/yr. Weed control is achieved through the use of herbicides combined with hand weeding. We use a mix of Dual® and Lorox® (pre-emergence), Fusilade® against grasses, and Gallery® 4 weeks after planting. No undercutting or wrenching are done, but vertical root pruning is done between the rows in the beginning of August to promote root development closer to the stem. Plants are lifted by machine (Fobro) late in the fall at a height of 80 to 200 cm. Plants are then processed indoors for grading, culling, root trimming, counting, packaging, labelling, and storage (-2ºC). Against all expectations, customers are pleased with the plant size and become rapidly accustomed to the logistics of poplar planting.
Ilona Peszlen1, Béla Marosvölgyi2 and Róbert Tamás2
1Iowa State University, Department of Forestry, Ames, IA 50011, USA
2University of West Hungary, Department of Energetics, Sopron, Pf 132, 9401 Hungary
Both wood quality and biomass production are of interest in relation to the growing and utilisation of poplars, especially in countries, such as in Hungary, where timber and biomass resources are limited. The forest land is relatively small in area and most of the forests are situated on marginal sites, outside their ecological optimum. Quality of the overall timber resource is poor, and its utilisation for traditional wood products is influenced by the high incidence of wood defects, such as the percentage and characteristics of juvenile wood and the incidence of reaction wood. On the other hand, presently more than 90% of Hungary's energy demand is supplied by fossil fuel and nuclear sources and only about 3% is from bioenergy. Roughly 55% of the energy for consumption must be imported; meanwhile, the potential for solar energy in the region is quite high, far above the European average. In this presentation, some results and conclusions of long-term investigations of wood quality and the feasibility of energy plantations of selected poplar clones are discussed. Clonal differences of wood properties for the Populus x euramericana clones included in these studies are often statistically significant but very small and may be negligible from a practical point of view. Characteristics of juvenile wood and reaction wood have to be considered for specific utilisation scenarios. Silvicultural methods could affect wood quality, maybe more so than breeding and selection. Besides environmental benefits, high-yield poplar energy plantations may become economically feasible in Hungary with harvesting on a 3-to 4-year rotation. Thus, the potential energy yield of energy plantations is quite high, 240-310 GJ/ha/yr resulting in 700-1,250 GJ/ha at the time of the harvest, especially if the most suitable clones are selected.
Ruben Petrosyan
Armenian Forest Service, Yereuan, Armenia
Armenia is a sparsely wooded country. About 98% of the forests are hard woods, (oak, beech, hornbeam, etc.) and only 2% are soft woods (pine, poplar, etc.). Due to the energy crisis since 1992, the forests of Armenia were damaged by the illegal harvests of about 30,000 ha. The suburban green forest mass of about 5,000 ha was cut down almost completely. To soften the after effects of the energy crisis, re-establish the ecological balance, and fill the demand for softwood, AESA provided assistance for establishing 53 hybrid poplar clones in 1994.
In 1997 an experimental-industrial plantation was established in Armavir marz of Armenia, where 14 selected clones were used (50-194, 49-177, 50-197, DN-70, DN-1, 55-260, NM-6, etc.). Plantations were established in Armavir cut-over forest areas in 1997 (15 ha), 1998 (19 ha), 1999 (29 ha and 1 ha of nursery), and 25 ha of plantations are foreseen for year 2000. The plantations were established mainly by the spacing schemes 3.2 m, 3.3 m, and 3.4 m. The best dendrometric indices were displayed in Armavair by the clones 50-194, 55-260, 49-177, 184-411, and 50-197. About 10,000 ha of the damaged forest areas of Armenia could be used for growing hybrid poplars, thus improving the ecological conditions of the damaged areas on one hand and filling the demand for soft wood and firewood in Armenia on the other hand.
Leopold Poljakovic-Pajnik1, Olivera Petrovic2, and Sasa Orlovic1
1Agricultural Faculty, Poplar Research Institute Novi Sad, Antona Cehova 13, P.O. Box 117, 21000 Novi Sad, Yugoslavia
2Agricultural Faculty, Belgrade, Yugoslavia
In the course of the last few years in poplar growing regions in Serbia, an increased presence of aphids as well as a higher number of aphid species were observed. The increased presence of aphids caused significantly more conspicuous consequences of aphid attack, such as chlorosis, leaf deformation, different forms of galls on the leaves, retarded shoot and plant development, and in extreme cases, plant death. The differences in aphid species' predilection for various poplar species and clones were observed. The most endangered clones were those of autochthonous black poplar and white poplar.
The represented aphid species were collected and determined by inspection. During our research and after Petrovi, the following aphid species were identified: Chaitophorus longisetosus Szel., Chaitophorus populialbae (B.d.F.), Chaitophorus leucomelas Koch, Chaitophorus nassonowi Mordv., Chaitophorus populeti (Panz.), Chaitophorus tremulae, Pterocoma populeum (Kalt.), Pachypappa spp., Pemphigus bursarius (L.), Pemphigus immunis (Buckt.), Pemphigus phenax, Pemphigus populinigrae (Schr.), Pemphigus protospireae Licht., Pemphigus spyrotheca Pass., Phloeomyzus passerinii (Sign.), Pterocoma populeum (Kalt.), Thecabius lysimachiae.
Along with the study of aphids, the following physiological parameters were analysed: transpiration, photosynthesis, stomata conductivity, and A and B chlorophyll contents in attacked and unattacked plants. The study results point to significant differences between attacked and unattacked plants. The study will continue in further detailed research of aphid fauna on poplars, more detailed research of the relation between aphids and physiological parameters of the host plant, predilection of various aphid species for poplar species and clones, as well as potential control measures.
Marcelo Ponce, Sergio Iraira, and Luis Angulo
Centro Regional de Investigaciones Remehue, Instituto de Investigaciones Agropecuarias, Casilla 24-0, Osorno, Chile
To obtain low cost rations for cattle, economically successful perennial ryegrass intercropping will mainly depend on pasture productivity and its dry matter (DM) unitary cost. However, dry matter production decreases across time due to the effect of tree shadow. The objective of this research was to determine the cost of forage dry matter obtained from Lolium perenne sown intercropped with 3-, 5-, and 8-year-old poplar trees. The study was done in San José de la Mariquina (39o 36' S.L.), Chile, on a volcanic ash soil with 1,700 mm of annual rainfall and average temperatures of 16.9o C maximum and 1.7oC minimum.
The experimental design used included poplar plots at a density of 277 trees ha-1 (6 x 6 m); ryegrass production was evaluated for 3-, 5-, and 8-year-old poplar trees. Cover index was 3.2 m, 4.5 m, and 5.8 m wide, respectively. The DM costs are expressed in U.S. dollars.
Twenty-five kilograms of Lolium perenne per hectare were sown in March 1999; the fertilisation was 50 kg N/ ha, 147 kgP2O5/ha and 96 kg K2O/ha. After the first and second cut, 50 kg N/ha was added.
Annual dry matter accumulation reached 7,137; 6,234; and 1,851 kg/ha (P<0.05) for 3-, 5-, and 8-year-old poplar trees, respectively. Unitary costs were 0.014, 0.016, and 0.031 U.S. $/kg DM, respectively. The reference cost of the dry matter in a normal situation is 0.015 U.S. $/kg DM.
The results obtained indicate that ryegrass intercropping with 3- and 5-year-old poplar trees permitted the achievement of a satisfactory unitary cost of DM for cattle production. In these cases the cost of DM was similar to a normal pasture. However, for the 8-year-old trees, ryegrass production was severely affected and increased its unitary cost; therefore, it would not be economically feasible for cattle feeding.
Simon Potter
Pulp and Paper Research Institute of Canada, Vancouver, BC, Canada
The utilisation of species of the Populus genus of forest trees, particularly aspen and cottonwoods, as the cornerstone for the development of short-rotation intensive culture (SRIC) sustainable plantation forestry in the Northern Hemisphere has been promoted recently for a number of reasons. The primary driving force behind the implementation of SRIC Populus plantations, however, is their potential to alleviate the shortfall in world fibre supplies projected for 2010. This threat has provided an impetus for the examination of alternative fibre sources. Many non-wood sources have been characterised, but the most logical and industrially expedient solution to the problem is likely to lie in fast-growth hardwood tree species. In the Southern Hemisphere (and some parts of Europe), eucalyptus species are the hardwood of choice, for their high growth rates, inherent adaptability, and excellent papermaking properties. In the Northern Hemisphere, poplars represent a similar opportunity, having high growth rates- up to 30m3/ha/yr, producing pulps of high natural brightness, and offering the potential for genetic improvement of wood quality traits. If Populus species plantations are to be commercially successful, therefore, it is critical that they produce marketable pulps with desirable papermaking properties.
A number of research groups have previously noted that certain poplar species have an inherent tendency to accumulate mineral deposits, particularly calcium salt crystals, in their wood. Evidence described in these papers suggests that these crystals do not represent abnormalities but rather are consistently present in some Populus lineages (particularly the sections Aigeros and Tacamahaca). The crystals were found to accumulate in the stem, branches, roots, and within vessels and fibres frequently occluding them completely. The present study confirms that certain poplar species, including some of the hybrid poplars examined here, are prone to localised calcium crystal accumulation within vessel elements. The study expands on this previous observation in two major respects. First, at least in the kraft process, these calcium deposits are carried through the pulping regime and appear as hard, localised "bumps" in handsheets made from the pulp. If carried through cleaning, screening, and bleaching, such surface deformations would adversely affect paper quality.
The implications of these observations for kraft pulping are apparent. The fact that the deformation-causing deposits are present even after extensive pulp beating is cause for concern. Surface deformations of the kind seen here may seriously affect the quality of such pulps produced from poplars of these species. In the standard handsheet testing undertaken in this study, the presence of the deformations caused manifold problems when performing caliper tests (to determine apparent density and apparent specific volume) and roughness tests. Furthermore, calcium ions are known to cause a number of costly problems for pulp mills. Calcium ions introduced into pulping systems in wood can combine with carbonate, oxalate, and sulphate ions to form complexes that are capable of causing blockages at all pulping stages. Calcium oxalate scaling is one of the most trying problems experienced in modern bleach plants and can affect evaporators and pulp digesters. At lower pulping temperatures, resin and fatty acid soaps can precipitate with calcium ions, making it more difficult to wash the pulp free of those soaps. The results of this study may, therefore, be regarded as a caveat for the use of certain species of poplars in pulping - if poplars are harvested from calcium-rich soils, there may be problems during processing and papermaking due to the accumulation of calcium salts in those trees.
Jyothi Rajagopal1, D.K. Khurana2, P.S. Srivastava3, and Malathi Lakshmikumaran4
1Department of Biological Sciences, Hansen Building, Purdue University, West Lafayette, IN 47907, USA
2Department of Tree Improvement, Dr. Y.S. Parmar University of Horticulture & Forestry, Solan 173 230, Himachal Pradesh, India
3Centre for Biotechnology, Faculty of Science, Jamia Hamdard, Hamdard Nagar, New Delhi 110 062, India
4Plant Molecular Biology Division, Tata Energy Research Institute, Habitat Place, Lodhi Road, New Delhi 110 003, India
The genus Populus is made up of nearly 35 species classified into five sections. The major rationale for poplar plantations is their potential use in industry, agroforestry, landscaping, and as animal feed. In India, however, plantations are largely dominated by Populus ciliata and Populus deltoides. Populus ciliata (also known as the Himalayan poplar) is endemic to the Himalayan belt and is important silviculturally because it serves as a nursery crop for regeneration of silver fir. Populus deltoides, on the other hand, is found in the plains and is grown both as a plantation and as an agroforestry species. A number of hybrids are being developed in the genus to obtain diverse planting material showing varied adaptability and improved tolerance to biotic and abiotic stresses.
A major prerequisite for such improvement programs is the development of marker systems that may be used for clonal/hybrid identification. Repetitive DNA elements that are known to constitute a major part of the nuclear genome are powerful tools to study phylogeny. Besides this, species-specific repetitive DNA elements have been used in a wide range of plant genera for germplasm characterisation. Keeping this in view and considering the limited knowledge on the genome organisation in the genus, the isolation of repetitive DNA elements from the genus was attempted. A total of 400 clones were screened for presence of repeat sequences from a genomic library of Populus deltoides digested simultaneously with four blunt-end cutting enzymes. A number of repetitive elements were identified, and these belonged to two classes, namely tandem and dispersed repeats. Two tandemly organised repetitive sequences, namely the 145bp and the 110bp, were identified as these produced a classical ladder pattern with HaeIII. The 145bp family is widespread across most species analysed except P. euphratica. The 110bp tandem repeat was organised as large clusters and was present in a number of species except P. trichocarpa and P. euphratica. One family of dispersed repeats identified was characterised in P. deltoides. This member was absent in a number of species such as P. alba, P. davidiana, P. euphratica, and P. tomentosa.
Repeated DNA elements are an ideal tool to study the phylogenetic relationship between species. We have observed that the repeat elements identified in P. deltoides that are widespread across the species are strikingly absent in P. euphratica. This clearly indicates that P. euphratica is a distant member of the genus and may belong to another genus. Our data employing the sequence comparison of the 5S rDNA spacer region also substantiates the genetically distant nature of P. euphratica. Another application of the repeat elements is in the analysis of wide hybrids. The 110bp and dispersed elements, which are prevalent in some species and absent in other species, have been utilised for screening of interspecific hybrids in this genus. The chromosomal localisation of these repeat elements by in situ hybridisation is in progress and will be discussed.
Rao Hongyu1, Wu Ningfeng2, Chen Ying1, Huang Minren1, Fan Yunliu2, and Wang Mingxiu1
1Laboratory of Forest Genetics and Gene Engineering, Nanjing Forestry University, Nanjing, 210037, China
2Institute of Biotechnology, Chinese Academy of Agricultural Sciences, Beijing, 100081,China
Insect-resistant poplar (Populus deltoides Bartr. x Populus simonii Carr) plants have been produced by infecting leaf disks with Agrobacterium tumefaciens strain LBA4404 carrying a binary vector pFWZ10 containing an artificially modified Bacillus thuringiensis toxin gene (Bt gene) under a duplicated CaMV 35S promoter and omega enhancer, and npt II, a selected marker gene. Seventy kanamyacin (km)-resistant clones have been regenerated from the selected medium with km 60 mg/L. PCR analysis showed that 31 clones produced the same band as the Bt gene did. PCR-southern blotting showed there were 8 clones into whose genome the Bt gene has been inserted. Bioassays with the larvae of Lymantria dispar on the leaves of 31 PCR-analysed clones showed different levels of insecticidal activity compared with the control. Four clones showed higher than 80% death rate of larvae fed with the leaves of the selected plants on the tenth day, except that six clones showed no insect resistance compared with the control, which may show gene silencing in the transgenic plants and will be analysed. The clones showing insect resistance have been moved to the field. Molecular and insect-resistance analysis of the field plants will be done in the future.
Drusilla Riddell-Black
WRC, Marlow, SL7 2HD, United Kingdom
A series of studies undertaken at WRC have employed willow and to a lesser extent, poplar, for the novel, sustainable, and cost-effective management of waste. These have included application of sewage biosolids, polishing of sewage effluent and industrial wastewaters rich in plant nutrients, onsite management of landfill leachates, and rehabilitation of heavy metal contaminated land. All these techniques place specific demands on the varieties used and hence fitness for purpose is an important criterion for variety selection. Equally, it may be possible to optimise the efficacy of the approach by selection of varieties that have pertinent traits, such as high heavy metal accumulation, high tolerance of saline soil solution, low nutrient use efficiency, and so on.
Drusilla Riddell-Black1, Richard Marshall2, and Rachel Ferguson1
1WRC, Marlow, SL7 2HD, United Kingdom
2RMC Aggregates (Greater London), Ltd.
Landfill leachate management is an ongoing cost after a landfill has ceased to generate income. Leachate contains components beneficial to plant growth as well as those that may be toxic in excessive quantities. Onsite treatment by irrigation onto contained areas can eliminate the need for sewer discharge and thereby reduce aftercare costs. Liquor volumes are reduced through evapotranspiration, and soil chemical and physical processes combined with plant nutrient uptake can be effective at reducing the potential impact of the leachate on receiving waters.
Short-rotation forest plantations of willow and poplar have high evaporative potential and low management requirements and hence are an attractive crop for landfill leachate management. Systems are in operation in Sweden (willow) and the U.S. (poplar). Studies in the UK are investigating more aggressive leachates with high ammonium-nitrate concentrations and high electrical conductivity. Two long-term trials were established in May 1998 following a successful pilot trial the previous August, aimed at determining the capacity of Salix to tolerate and assimilate leachate components.
Drusilla Riddell-Black1 and Nils-Ove Bertholdsson2
1WRC, Marlow, SL7 2HD, United Kingdom
2S valöf Weibull AB, SE-268 81, Svalöf, Sweden
Land on the urban fringe can be contaminated with heavy metals as a result of industrial activity, posing a risk both to human health and to the environment, restricting the use of such land and thereby its value. Remediation may be possible by chemical means, or by burial of the contaminated area, but this is expensive and is seldom undertaken for large areas suffering from low level contamination. The production of biomass fuel crops on such land can bring it into economic use, result in an aesthetic improvement, and potentially lead to long-term remediation through heavy metal removal in the harvested crop. The production of biomass fuel crops on degraded land has several advantages as a site remediation measure. Some, such as Salix and Populus, are pioneer species and hence are adapted to the harsh growing conditions that typify derelict land. Establishment and management costs are low compared with chemical washing. The contamination is contained onsite unlike a conventional dig and cart approach. Energy conversion of the fuel offers a method for the concentration of metal contained in the biomass. Production of a low risk, non-food crop on otherwise unproductive land brings that land back into the local economy.
Don Riemenschneider1, Jerry Tuskan2, Carl Mohn3, Richard Hall4, Glen Stanosz5, Don Dickmann6 and J.G. Isebrands1
1USDA Forest Service, North Central Research Station, Rhinelander, WI 54501, USA
2Oak Ridge National Laboratory, Oak Ridge, TN 37831-6422, USA
3University of Minnesota, Department of Forest Resources, St. Paul, MN 55108, USA
4Iowa State University, Department of Forestry, Ames, IA 50011, USA
5University of Wisconsin, Department of Plant Pathology, Madison, WI 53706-1598, USA
6Michigan State University, Department of Forestry, East Lansing, MI 48824-1222, USA
The breeding and selection of poplar clones suited to fibre and biofuel feedstock production requires simultaneous attention to all elements of the production system. Selection criteria need to be chosen wisely because they determine the characteristics, i.e., growth rate, pest resistance, rooting ability, wood quality, etc., of the resulting cultivars: characteristics that further determine whether any industrial production system can succeed biologically and economically. Too few criteria can leave some important traits unimproved, while too many criteria can frustrate a breeding program logistically, especially when traits are negatively correlated within the same population. Selection is further complicated because the ability to produce large populations of hybrids, coupled with the ability to practice clonal propagation, mean that some multistage selection strategy must be developed. Selection can be imposed among seedlings prior to propagation, among remaining clones in short-term tests, and, ultimately, among a few clones after large block yield testing. The choice of which selection criteria to impose at each stage, and at what intensity, determines the cost and probable success of any breeding effort. In addition, selection criteria may be subject to genotype x environment interactions, depending on the range of environments found within the zone of commercial deployment and on the kind of populations under test. We will discuss the effects of different breeding and testing strategies on the likely outcome of poplar improvement programs. We will also discuss reasons why the information needed to optimise breeding and testing strategies has remained mostly inadequate and suggest methods that might be used to obtain that information.
We will use, as a case study, data from the Regional Testing Program we have been conducting in Minnesota, Iowa, Wisconsin, and Michigan. Our objectives have been to: 1) identify highly productive, disease-resistant clonal selections and 2) understand any patterns of genotype x environment interactions within the Region that would, logically, govern commercial deployment of new clones. Clones were selected from breeding programs at Iowa State University, the University of Minnesota, and the USDA Forest Service for experiments established in 1995 and 1997. The 1995 test included 43 clones of P. deltoides, 10 clones of P. deltoides x P. maximowiczii F1 hybrids, 2 clones of P. deltoides x P. nigra F1 hybrids (including the DN-34 [a.k.a. NC-5326, cv. Eugenii] control), 1 clone of P. nigra x P. maximowiczii (NM-6 control), and 4 clones of aspen hybrids. The 1997 test included 75 clones of P. deltoides, 12 clones of P. deltoides x P. maximowiczii F1 hybrids, and the same commercial controls. We will report results of analyses of variance and principal component analyses of tree heights, diameters, estimated aboveground biomass, Septoria canker incidence, and Melampsora rust incidence that have demonstrated both significant genotype main effects and significant genotype x environment interactions. We will use these and other data to demonstrate how multiple selection criteria might be allocated among stages of testing, and how selection for wood quality might be superimposed on our existing program.
Christopher Rog 1, J.G. Isebrands2
1SandCreek Consultants, Rhinelander, WI 54501, USA
2USDA Forest Service, Forestry Sciences Laboratory, Rhinelander, WI 54501, USA
Phytoremediation is an emerging technology that is a cost-effective and environmentally sound approach for many municipal landfill cleanups. Two of the most common tree species used in phytoremediation are poplars (Populus spp.) and willows (Salix spp.); both exhibit rapid growth rates and ease of vegetative propagation. More information is needed on the proper choice of tree clones for phytoremediation because soils, climate, and contaminants vary with sites. In this study we examined the phytoremediation potential of 10 northern poplar and willow clones in response to applications of Rhinelander, WI municipal landfill leachate in a replicated factorial experiment.
Our objectives were to compare seasonal: 1) plant growth, 2) hydrological uptake, 3) volatile organic compound (VOC) removal, and 4) inorganic macro- and micro-ion removal for the 10 clones growing across four experimental treatments (i.e., with and without contaminated water, and with and without trees).
Trees were grown from cuttings in landfill soil in 600 litre plastic tanks, and watered weekly with applications of either municipal water (control), or leachate ground water (contaminated) during the 1999 growing season; other tanks were treated similarly without trees. VOC's of the influent and effluent were monitored periodically, leaves were collected in October, and plant components (i.e. stems and roots) harvested in December for micro- and macro-ion analysis. Our results showed that height and volume growth of the poplar and willow clones growing in contaminated water were not significantly different from the controls. There were growth differences among the clones 2 poplar and 2 willow clones performed the "best". Tanks with trees took up 3 times the quantity of water when compared to tanks without trees indicating significant hydrologic uptake. Contaminant VOC's from the Rhinelander landfill were removed at a rate similar to the evapotranspiration rate including 1,1 DCA, tetrahydrofuran, benzene, and vinyl chloride. Significant quantities of some trace metal ions were removed by the trees; e.g., boron and zinc were found in leaves of some clones at concentrations much higher than most northern plants. Moreover, there were significant differences among clones in leaf concentrations of macro-ions such as magnesium and calcium that often contribute to ion toxicity in receiving waters near landfills. Our overall results suggest that certain poplar and willow clones have much potential for successful phytoremediation at our Rhinelander landfill.
S. Roncevic, P. Ivanisevic, and S. Andrasev
Agricultural Faculty, Poplar Research Institute Novi Sad, Antona Cehova 13, P.O. Box 117, 21000 Novi Sad, Yugoslavia
The productivity of nine selected poplar clones was researched in the floodplain of the river Sava, on fluvisol with a fossil horizon. The test was established with three replicates with nine clones of which seven clones are Populus deltoides (cl. S6-20, 721, S6-36, 618, 450, 55/65, and 457) and two clones Populus euramericana (cl. I-214 and Ostia). The standard (normal) planting technique was applied, planting stock 1/1, spacing 4.25 x 4.25 m or 555 plants/ha. Nine years after test plantation establishment, 50% of the trees were felled by regular geometrical thinning, so that after thinning 278 trees/ha remained. At the time of thinning, wood volume amounted to between 68 m3/ha (cl. S6-20) and 145.6 m3/ha (cl. 457). After 9 years of test plantation development, at the time of thinning, clone 450 had the highest current increment with 30.3 m3/ha and clone S6-20 with 17.7 m3/ha had the lowest current increment.
At the end of the 20th growing season, the total produced timber volume, with thinned wood volume, was between 356.8 m3/ha for clone S6-20 and 461.5 m3/ha for clone 450. In this period, current increment ranged between 14.9 m3/ha (cl. 457) and 22.9 m3/ha (cl. S6-36).
The culmination of current annual increment of all clones occurred during the ninth year, the year of thinning. After thinning, current increment had a more moderate course, which leads to the conclusion that clone reaction to the increased growing space was not significant and that the results of thinning were not significant. The results presented in the paper show that, in addition to the correct choice of plantation establishment technology and the correct clone selection, one of the most significant factors of successful plantation development is the maximum utilisation of soil potential.
R. Rousseau
Westvaco Corporation, Wickliffe, KY, USA
The focus of both Populus research and operational deployment in the Southern United States has been on eastern cottonwood (Populus deltoides Bartr.). Eastern cottonwood research efforts were the primary undertaking of the USDA Forest Service Southern Hardwoods Laboratory at Stoneville, MS. Research efforts included the fields of genetics, silviculture, biometrics, pathology, and entomology, which were all aimed at providing growers with a product that was both cost-effective and high yielding. Both sawtimber and pulpwood industries quickly embraced this highly intensive new program. One significant problem was that the best sites for cottonwood production were either unprotected alluvial land or highly productive protected alluvial agricultural land.
Westvaco, like a number of pulp and paper companies, owns suitable cottonwood sites in the lower Mississippi River Valley. Westvaco began operational deployment of eastern cottonwood clones in the early 1970s based on the results of cottonwood clone tests established in the mid- 1960s by the Stoneville group. At that time, research at Westvaco's Central Forest Research Center was primarily focused on loblolly pine rather than cottonwood, and it was not until 1980 that the company became interested in developing an in-house hardwood plantation research effort. This new direction included a variety of species as well as eastern cottonwood. In the mid-1980s the research efforts at Westvaco's Central Forest Research Center, now located at Wickliffe, KY, began to focus on eastern cottonwood. Clonal testing efforts increased dramatically at the centre as a means of constructing a suitable breeding population. This effort was also supported by co-operative work between Westvaco and the University of Kentucky with the development of a Disease Resistant Eastern Cottonwood Breeding Population. In addition, a cooperative effort among Westvaco, the Forest Service, and Crown Zellerbach was initiated to investigate the performance of pure clonal blocks and clonal mixtures. In addition, we began investigating breeding techniques in anticipation of our next effort in cottonwood genetics. However, in 1989 our cottonwood research was discontinued as a moratorium was placed on the operational plantation program at the Central Center.
In 1995, Westvaco reinitiated its hardwood research efforts, but this time the effort was on a division-wide basis. The knowledge gained in the 1970s and 1980s was used as a starting point for the renewed program in eastern cottonwood. New facilities were constructed and research personnel were hired to push forward the new hardwood plantation initiative. The major difference was that this renewed hardwood effort included both uplands and fibre farm plantations. With these new areas came new challenges not only in the field of genetics, but also in physiology, silviculture, and biometrics. In addition, Westvaco broadened its biotechnology expertise of hardwoods. Although our Populus breeding efforts now include material for upland sites, our primary focus continues to be on alluvial and fibre farm sites of the mid-south. Testing includes control-pollinated progeny tests and various clonal trials. Selections from these trials are being fed into both our biotechnology and plantation productivity research programs as well as our operational deployment population.
Maurizio Sabatti1, Ervedo Giordano1, Naldo Anselmi2, and Giuseppe Scarascia Mugnozza1
1University of Tuscia, Department of Forest Environment and Resources, Via S. C. de Lellis, 01100 - Viterbo, Italy
2University of Tuscia, Department of Plant Protection, Via S. C. de Lellis, 01100 - Viterbo, Italy
The European Union foresees that a large amount of land will be withdrawn from agriculture and used for the production of non-food raw materials. The planned utilisation of this land includes afforestation and plantation of woody crops for biomass and timber production using fast-growing species of the Salicaceae family. The choice of the species to be planted could also be oriented toward the use of native poplars, allowing sustainable management of the plantations. The objective is to reduce the agricultural practices and the use of chemicals thanks to the trees' adaptability to the environment. A first type of plantation is aimed at the restoration of agricultural land using a 20-year rotation culture. Mixed plantations established with seedlings of some native (Populus alba, Carpinus betulus, Alnus glutinosa) and non-native species (Robinia pseudoacacia) are under observation for the use of permanent growth plots to evaluate ecological functionality and productive potential. The possible cultural operations will be discussed to define the criteria to be chosen for sustainable management of these plantations.
The second kind of plantation focuses on biomass production using a short-rotation culture. It will obtain subsidies from EU only if the plantation will be coppiced several times in a 20-year rotation. However, it is well known that commercial clones available in Italy were selected mainly for timber production. For this reason, we established in 1998 a poplar clonal trial to study and evaluate under short-rotation culture (spacing 3 x 2 m) the performance of some poplar species and hybrids in growth and adaptation to the main biotic and abiotic stresses. The trial included 12 clones of P. alba, 3 clones of P. nigra F1 , 1 clone of P. deltoides F1, 2 clones of P. deltoides x P. nigra F1 hybrids, 4 clones of P. deltoides x P. trichocarpa F1 hybrids, 10 clones of P. x interamericana x P. nigra F1 hybrids, 1 clone of P. maximowiczii x P. x interamericana F1 hybrid, 1 clone of P. deltoides x P. x euramericana F1 hybrid, and 6 commercial clones (I-214, Boccalari, Luisa Avanzo, San Martino, Beauprè, Villafranca) as control. P. alba clones were selected from a common garden study at the University of Tuscia, and the others were selected from the breeding program of a private company. We will report results of analysis of variance of tree heights, diameters, estimated aboveground biomass, and susceptibility to some pests (Melampsora spp., Marsonnina brunnea, Venturia populina) and insects (Paranthrene tabaniformis, Melasoma populi) that have demonstrated significant genotype main effects. The analysed data showed a very good adaptation of the white poplar clones towards rust and insects, confirming the potential of this species for further genetic improvement.
S. Ebrahim Sadeghi
Research Institute of Forests & Rangelands, P.O. Box 13185-116, Tehran, Iran
This study was carried out during 1998 to 2000 at the Alborz research centre poplar nursery in Karadj, Iran. Poplar leaf beetle is considered a major pest of poplar species in Iran. Adult and larval instars attack young stands (1 to 5 years old) in poplar nurseries and native plantations. During severe infestation, adult and larvae can defoliate host trees. Our field studies, in 1999, showed that the damage rate caused by this insect varied among different poplar species and clones. On the basis of these field observations, a number of field experiments were prepared. The poplar species used in this study included Populus nigra, P. alba, P. simonii, and P. euramericana.
In the spring of 1999, a pair of newly emerged beetles were restricted to a 30-cm branch of each of the above poplar species by a lace tissue cage. These beetles were permitted to feed for a 20-day period, until they died. During this period, deposited egg clusters were collected daily and transferred to the laboratory. The eggs in each cluster were counted and registered. Total leaf area fed by each pair of beetles in their tissue cages was calculated by a digital planimeter. Analyses of variance of total fed leaf area showed a significant difference (p< 0.001) among these four poplar species. Populus nigra and P. euramericana were preferred compared to P. simonii and P. alba. Analyses of variance on total deposited eggs in each species show that P. nigra and P. euramericana were preferred hosts for ovipositing compared to P. simonii and P. alba. The average weight of newly emerged beetles that had completed their immature instars in P. nigra and P. euramericana clones was higher than that of beetles associated with P. alba or P. simonii.
Francesco Sala1, Hu Jianjun2, Yizhi Zheng3, Stefano Castiglione1 and Yifan Han2
1Department of Biology, University of Milano, Via Celoria 26, 20133 Milano, Italy
2Institute of Forestry, Chinese Academy of Forestry, Wan Shou Shan, 100091, Beijing, China
3Department of Biology, Northeast Normal University, Changchun, China
Poplar plantations all around the world frequently experience infestation by leaf-eating insects. Considerable damage is caused by Apochemia cinerarius Erscheff, Lymantria dispar L., and Orthosia incerta Hufnagel. Their pupae survive in the soil thus ensuring cycles of infestation. To face the problem, we have produced transgenic Populus nigra L. plants by infecting leaves with Agrobacterium tumefaciens carrying a Bacillus thuringiensis (Bt)-toxin gene under a duplicated CaMV 35S promoter. After molecular analysis, bioassays on insecticide activity in the laboratory, and greenhouse evaluation, selected transgenic plants are now being evaluated in a field trial in China. A plantation was established in 1994 in Manas (Xinjiang Ulygur Autonomous Region, China) which includes 14 Bt-poplar clones selected for insect tolerance and good silvicultural traits. Control non-transgenic plants were added at random positions in the experimental plot. The plants have now reached sexual maturity.
During peaks of A. cinerarius infection, we observed that: (a) leaves of Bt-poplar plants resist insect attack, (b) leaves of non-transgenic control plants, or of transgenic plants that had low insect resistance, present within the transgenic cultivation, were equally protected, (c) the number of pupae in the soil was far below the danger level. The explanation of this is that the insecticide activity of Bt-poplar trees reduces larval density in the soil, thus protecting all plants in the plantation. Events of somaclonal variation were recorded in the primary poplar transformants. Variation included changes in leaf morphology. Morphological and molecular analysis based on random amplification of genomic DNA sequences (RAPD analysis), showed that both DNA and leaf changes are retained after clonal propagation and growth to maturity in the Manas plantation.
Metin Saribas
Zonguldak Karaelmas University, Bartýn Orman Fakültesi,
A_daci Köyü 74100 / Bartin-Turkey
Forest resources in Turkey are not sufficient to meet the demand for wood. Therefore, it is necessary to find new alternatives to increase wood production. By means of poplar plantations, it is possible to produce abundant wood within 12 to 15 years. In this study, inner and outer morphologies of naturally growing aspen were investigated. The results obtained may be summarised as follows: vessel member number (mm2) in spring and summer woods at different altitudes. Springwood vessels are larger than those of summer wood. The dimension of vessel decreases systematically toward sea level. A super positioned perforation table exists. In the radial direction, vessel groupings contain 2 to 8 vessels or a maximum of 3 to 10 vessels. Rays are "Uniserite" and "Homocellular" in aspen, and their length varies between 0.656 mm and 2.0 mm. Aspen wood should be utilised in papermaking.
Metin Saribas
Zonguldak Karaelmas University, Bartin Orman Fakültesi,
Adaci Köyü 74100 / Bartin-Turkey
Forests of Turkey are not enough to meet the country's wood needs. The wood deficit started in 1982 and will reach 15 billion m3/yr in 2000 according to predictions. To enhance wood production, new possibilities for expanding wood production must be found. It is possible only poplar growing can supply necessary wood products in the next 12-15 years. Poplar has been grown for a long time in Turkey. Lands of poplar growing have been expanding quickly in Turkey. According to the inventory study done in "Poplar Growing Project" by the Turkish government and FAO before 1968, annual poplar wood production of Turkey was approximately 600,000 m3/yr. Today 3.5 billion m3/yr of poplar wood are produced. Poplar growing studies have been conducted since 1957. Today, there are some problems of poplar growing; poplar growing research must be continued. Exotic clones using production in the world must be grown. Hybridisation studies of indigenous and exotic trees must be continued. New lands must be found for growing poplars.
G. Scarascia Mugnozza1, C. Calfapietra1, M. Sabatti1, P.de Angelis1, R. Ceulemans2, B. Gielen2, and F. Miglietta3
Department of Forest Environment and Resources (DISAFRI), University of Tuscia, Italy
2University of Antwerpen, Belgium
3Inst. of Agrometeorology and Environmental Analysis, CNR, Italy
Awareness has been growing recently that trees and forests not only passively undergo global climatic changes, but also are driving actors that determine the course of climatic changes. As this active role is being emphasised more and more, the scientific community aims to assess and quantify the contribution of forests in the global climate change issue. The increase of atmospheric CO2 concentration is a crucial point in this matter, and many techniques have been adopted to study the behaviour of trees under elevated CO2 concentration conditions. FACE (Free Air Carbon Dioxide Enrichment) technique is turning out to be the most efficient one in the recent years since it allows the study of the forest ecosystem without altering microclimatic conditions and without limiting the dimensions of the plants. This technique has been applied in an experiment on short-rotation, intensive poplar plantations called POPFACE funded by the European Community and participated in by different European research groups. A poplar plantation of about 10 ha was established in spring 1999 in an agricultural region of central Italy, and six experimental areas-three with elevated CO2 (550 ppm) and three with ambient CO2 were selected inside the plantation. Three different genotypes of P. alba, P. nigra, and P. x euramericana are being used to study the effect of elevated CO2 at different levels from leaf physiology to whole canopy activity, from roots and mychorrhizae to interactions of plants with fungi and insects.
During the first growing season, the validity of the FACE facility was tested and preliminary data on tree growth and physiology were collected. An increase in growth parameters was observed in all species and seemed to be rather significant for the P. nigra genotype. Particularly, the number of sylleptic branches and the volume index of the main stem were stimulated by elevated CO2 , together with total leaf area per plant; therefore, total aboveground biomass increased under the elevated CO2 treatment, resulting in an increase in carbon sequestration capacity by plants. In the second growing season, the further expansion of tree crowns and canopy leaf area is causing the onset of a strong, inter-individual competition for light and other resources that will interact with the growth and physiology of the different poplar genotypes growing under ambient versus elevated CO2 . The experimental results of the second year and a comparison with first-year results will be discussed to provide clues to the potential contribution of agroforestry in a future world of elevated CO2.
W. R. Schroeder
PFRA Shelterbelt Centre, Indian Head, Saskatchewan, Canada
In planning for poplar production as with any crop it is important to consider climate, soil, landscape, market, production, social and economic factors before making any decision to grow poplars commercially. Land suitability is defined as the fitness of land for a specified kind of land use. Poplars have specific growing requirements and growers need to know which areas are suitable for economic poplar production. The classification was based on an assessment of land qualities which affect poplar growth. These qualities include biophysical features of soil, topography and climate. The assessment of suitability does not take into account hazards such as fire, pests or diseases, nor does it consider socio-economic factors. This paper evaluates the suitability of landscapes for hybrid poplar production. Our objectives were to identify landscape areas that are potentially suitable for hybrid poplar production in plantations and to develop a hybrid poplar suitability mapping systems that can be adapted at both provincial and regional scales.
The criteria supplied for hybrid poplar development required the evaluation of climatic growth factors including growing season precipitation, annual precipitation, and annual moisture deficits. Soil and landscape factors considered included depth to water table, soil texture, salinity, pH, sodicity or SAR rating, A-horizon depth, slope percentage, slope length and flooding. Criteria for specific ecoregions were also initially considered. Using growth data of hybrid poplar collected from 100 sites selected over a wide geographic area, three suitability classes were established; Excellent or the most suitable areas for poplar growth, Good - while still suitable for poplar production, conditions were less favourable than the top class, and Poor - soil, landscape and or climate conditions are not favourable for strong growth of hybrid poplars.
Using Global Information Systems (GIS) we generated suitability maps at both regional and provincial scales. The provincial map considers growing season precipitation and dominant surface texture and utilised the Soil Landscapes of Canada Database (1:1 million scale). A more detailed regional map was derived from the 1:100,000 soil attribute database. Two methods were used to create regional and provincial maps. The first utilised the method of most limiting factor in which the most limiting factor affecting growth determined the growth potential for the area, While this method was simple to apply it does not recognise the importance of each growth factor being rated. Therefore, a second method of creating a final rating based on the relative importance of each the factors was applied
Provincial ratings reflect the dominant effect of climate in determining the most suitable location for the growth of hybrid poplars. Thus climate was considered 60 % of the total suitability while soils are considered as 40%. Regional ratings reflect a more detailed mapping of soil conditions thus a greater emphasis of portraying differences in soils and landscapes in the final poplar suitability ratings. Climate ratings were adjusted depending on the location in the region and reflect the provincial rating of the area. For the regional area used in the study, the climate rating on the provincial map was considered excellent, therefore the regional area receives the top climatic rating in the provincial rating as well. In regional studies, soils receive 70% of the total suitability rating, while climate receives 30 %.
Using GIS technology we were able to accurately map hybrid poplar suitability at the provincial and regional levels. The maps can be used by researchers, landowners and foresters to identify areas suitable for commercial production of hybrid poplars on agricultural land.
