BELA KERESTESI is Director of the Hungarian Forest Research Institute.
Forest tree improvement plays an important role in the development of modern Hungarian forest management. It was started in Hungary about 1930 and was expanded in 1950, following the reorganization of the Forest Research Institute (ERTI). Within the Institute, the Sárvár Experiment Station is the center of tree improvement research. Research on improvement is also carried out at the University of Forestry and Wood Industry and the School of Forestry, Sopron. Fifteen scientific workers are engaged in forest tree improvement. The main target of this research is the increase of yield (in terms of absolute dry matter) per unit area. Further important aims are resistance to disease, regular seed production and improved wood quality. Closely connected to the research on improvement are forest trials. The cultivars produced by selection or crossbreeding are put into large-scale cultivation trials in those forest regions where they will be grown. The introduction of these various cultivars into forest practice is based on the trial results. The results of poplar breeding have been used in practical work for many years. Since 1960 poplar plantations have been established almost exclusively with planting stock raised from improved propagating stock. The research results attained in conifer breeding are still to be introduced into forest practice.
Hungary is situated in the zone of central European broadleaved forests. About 70 percent of Hungarian forests are natural and 30 percent are secondary and plantation forests. Forest tree improvement is concentrated chiefly on the fast-growing broadleaved species of the secondary and plantation forests. The most important of these species are poplar and willow, while black locust has the widest distribution. Site conditions in Hungary are generally favorable for poplar cultivation. Aspen occurs naturally in the mountain and hill regions while black, white and gray poplars grow on the bottomlands and sands of the plains. The need for poplar and willow arose only after the first world war when the country lost much of its former forested areas under the terms of the peace treaty. In the course of plantings done An the great Hungarian plain (Alföld) which was almost totally devoid of trees 150 to 200 years ago, the spread of black locust was so great that it now occupies 15.9 percent of the country's total forest area. By 1957 the poplar area had risen to 35,000 hectares and that of black locust to 200,000 hectares. From 1958 to 1965, new poplar plantations were established on some 65,000 hectares. In the present five-year plan, from 1966 to 1970, poplar plantations on a further 50,000 hectares ate envisaged. On the other hand, a further significant increase of the black locust area is not expected.
The tasks of tree improvement are derived from the afforestation policy. Within the large-scale poplar program the main objective is to produce poplar cultivars suitable for pulp, paper and panel production. In black locust breeding the objectives are high yield, quality, increase of flower nectar content and extension of the flowering period.
In Hungary, 231 plus trees of poplar, 43 of tree willows and 40 of black locust have been selected. Clonal collections created from propagation material of plus trees of exotic species, varieties and cultivars include 912 poplar, 424 willow and 150 black locust clones.
Crossings have been made with poplar (Kopecky), tree willow (Kopecky and Tompa) and black locust (Kerestesi and Kopecky). According to observations so far, hybrids of the Leuce and Aigeiros sections exceed their parent species in height growth and especially in diameter growth. This hybrid vigor can be exploited commercially. Among the interspecific hybrids obtained, the most outstanding results were produced by the following combinations: P. tremula x P. tremuloides, P. alba x P. grandidentata and P. deltoides x P. nigra. In the latter combination several interspecific hybrids were produced and these proved resistant to injury by both Marssonina and Melampsora.
The basic material of breeding for resistance is produced with induced mutants. In Hungary, two radiation orchards are available, each with a source of 120 Curie 60Co. Black locust, poplar and willow planting stock is raised from irradiated cuttings and seeds.
Large-scale research is also undertaken in polyploid breeding. This method is very suitable for improving the performance of fast-growing trees, which can be propagated easily by vegetative means. Since in treating seed the radicle and roots suffer such severe injury that only a small proportion of treated seed survives, a method for treating seedlings has been developed. When the first pair of leaves appears the root extremities of black locust, aspen and white poplar are placed in' a 0.1 percent colchicine solution and held at constant light to keep growth constant. After treatment for 48 to 96 hours the roots are washed by soaking for the same time in well water. The number of tetra and mixoploids produced by this method exceeds 20 percent.
The number of polyploids produced is 136 black locusts and 11 poplars. These have been propagated and a polyploid seed orchard has been established at Bajti.
The best clones in the varietal collection, and the outstanding interspecific and interracial hybrids selected by early test methods in the course of progeny tests, are evaluated in short-term (6 to 10 years) and long-term (15 to 20 years) forest experiments.
Short-term clonal tests in populeta are carried out by the Sárvár Experiment Station on eight different forest enterprises over a total area of 120 hectares. The long-term comparative varietal trials connected with a detailed investigation of site requirements are managed by the Department for Site Survey and Poplar Growing of the Forest Research Institute, in collaboration with scientific workers at the experiment stations of Püspökladany, Kecslkemet and Sárvár, over a total area of 300 hectares. These latter trials are established with sufficient numbers of trees to form a stand. In addition to studies of site requirements, investigations include spacing, pruning, thinning, soil cultivation, fertilization and irrigation (Adorján, Babos, Halupa, Járó, Kerestesi, Palotás and Tóth).
On several forest enterprises, the growing of poplars at wide spacing in combination with agricultural crops is being investigated (Kopecky). On sandy soils the suitability of deep planting to reach the water table is also being examined (Simon).
The populeta and other poplar clonal and varietal trials have proven the superior growth of Populus x euramericana 1.214 among all the cultivars grown at present. It is followed by P. x euramericana Gelrica and P. euramericana H. 381. From poplars of the Leuce section, the growth of Euramerican poplars is approached only by the Hungarian P. alba x P. grandidentata hybrids.
On dry sites, Schreiner's hybrid P. x euramericana OP. 229 exceeds the growth of I.214. On alkaline soils, however, P. x euramericana Robusta takes the lead.
The cultivars proved site-hardy in these clonal and varietal trials are readily used by forest enterprises.
Full safety in the choice of cultivars is ensured by varietal control, the introduction of which is planned in the near future for fast-growing species.
Black locust improvement was begun in Hungary in 1930 by Fleischmann, with the aim of producing, by individual selection and crossing, fast-growing cultivars which flower abundantly at different times. His trials were destroyed during the second world war and the improvement work began anew in 1959. As a result of selection the following cultivars of silvicultural and apicultural interest were delimited in the form of small tree groups: Robinia pseudoacacia Jászkiséri, Zalai, Kiskunsági, Nyirségi, Császártöltési, Semperflorens, Tardiflora, Üllöl, Röjtökmuzsaji, Góri (Kerestesi).
The cultivars selected for their silvicultural qualities excel in comparison with the common black locust of the same age on identical sites by one site class in total yield, and by more than double gross financial yield per hectare.
The importance of the cultivars selected for bee-keeping lies in the fact that 80 percent of the honey bought and sold in Hungary (about 1,000 wagons per year) is yielded by black locust. The annual honey yield per hectare of black locust forests may be estimated at nearly U.S. $80.
FIGURE 1. - Poplar varietal collection in springtime.
Within the large-scale poplar program the main objective is to produce poplar cultivars suitable for pulp, paper and panel production.
According to trials in Hungary, the vegetative propagation of selected cultivars is possible with root cuttings excised from young plants, both in nurseries established under a plastic greenhouse and outdoors. The establishment of a black locust seed orchard is in progress.
FIGURE 2. - Location of poplar trials in Hungary. Long-term comparative varietal trials involvinq detailed investigation of site requirements cover a total area of 300 hectares.
I Western Transdanubia
II South Transdanubia
III The plain in northwestern Hungary
IV Central range of mountains in western Transdanubia
V Central range of mountains in northern Hungary
VI The great Hungarian plain
· Research stations for the comparison of growth of poplars
Because Hungary lies in the zone of broadleaved forests, the area of coniferous woods is low. Only 8.5 percent of the forest area is covered with conifers. The first significant deviation from the natural state occurred during the intense plantation activity in the 1920s. On the extremely dry and sandy soils of the great Hungarian plain and on eroded and stony slopes, Scots pine and Austrian black pine were the sole species that tolerated the sites. Significant conifer plantings originated in the postwar years but still did not represent a considerable extension of the area under conifers.
A rapid change was brought about by the forest site survey in the early 1960s. In the course of that survey, the forest enterprises determined, on the basis of productivity, those sites on which conifers could produce the highest sustained yield per hectare. Conifers were used in the conversion of stands degraded because of bad management and to improve the growing stock of highly productive broadleaved forests. The growth of conifers contributes to a rational use of site and a reduction in coniferous wood imports. According to current plans, the present 80,000-hectare area of coniferous species is to be raised within 30 to 35 years to 180,000 hectares. The most significant rise can be expected in Scots pine, Norway spruce and Austrian black pine.
The conversion of degraded stands and the planting of areas assigned by land-use planning to forestry require increasing numbers of coniferous plants. Formerly forest enterprises collected seed from unclassified stands. Soon a demand arose for planting materials from identified sources. Forest managements attempted to solve this problem by designating seed stands, and from 1963 to 1964 2,878 hectares of coniferous seed stands were designated (Mátyás). However, because of-the hazards of seed collection from standing trees taller than 25 or 30 meters, practically no seeds were collected from seed stands. The preservation of aging seed stands also did not seem to make biological sense and in 1964 and 1965 the area of conifer seed stands was reduced to 383 hectares or 13 percent of the area originally designated. Nevertheless, the stands canceled in the register are not harvested until their perpetuation has been assured. For this purpose, seedlings are raised from seed taken from seed trees constituting at least 10 percent of the parent stand. The seedlings are planted out in units of at least 5 hectares on neighboring sites with similar site conditions, with the aim of preserving for the future the promising genetical potential of these stands.
To assure the coniferous seed supply, seed production in seed orchards was started in the same period, on an experimental scale and principally for Scots pine. In 1951 the first plus trees were selected and in 1954 the establishment of experimental seed orchards was started (Bánó). At the present time about 30 hectares of Scots pine seed orchards are available and the results obtained so far are highly encouraging.
The plan for Hungarian seed orchards was from the beginning based on the idea that the most promising trees from the best forest stands growing in characteristic conifer regions should be thoroughly examined, and that large-scale seed orchards should be established from those trees which proved appropriate on the basis of a range of tests. According to the test method adopted, the seed production value of clones (defined as the net full seed weight per graft) is of first importance. As auxiliary indices, cone number and weight and full seed number are also considered. A clone can be proposed for introduction into a large-scale seed orchard only when, at the age of 10 to 15 years, it produces 10 grams of full seeds per graft. This is equivalent to 30 kilograms of net seed yield per hectare of seed orchard spaced at 4 by 8 meters. In Hungarian seed orchards there are several clones whose net full seed weight at 10 to 15 years of age exceeds 20 grams per graft. These convincing results made it possible to establish large-scale seed orchards.
In 1966, the establishment of a coniferous seed plantation was started, and the final area of 196 hectares will be developed in 70 years as three stages on almost equal areas. A similar seed plantation will be established from 1969 in the sandy region of the great Hungarian plain and, later on, another in the north central mountains (Gelföld) to meet the seed demands of that region.
Hungarian Scots pine seed orchards produce remarkably high seed yields in comparison with those reported from other countries situated to the north of Hungary. This seems to be due either to the good, genetically founded seed production of Hungarian stands or to favorable site conditions. To elucidate this problem, the Hungarian Forest Research Institute, jointly with the Forest Tree Improvement Institute of the Academy of Agricultural Sciences at Graupa (Eastern Germany), established in 1964 an international trial with Scots pine, Norway spruce, larch and Douglas fir clones.
It is planned that 30 to 40 clones will be planted in the first large-scale conifer seed orchard, established in 1967. So far these clones have been examined only for their seed yield but there is in progress an assessment of their yield improvement value, taking account of the heritable properties of their progenies. For this purpose the clones are examined in controlled crosses with four tester clones (Bánó and Retkes). The final assessment of clonal value is made on the basis of seed production value and yield improvement value. This value can be determined after 25 to 30 years for the clones recommended now for seed orchard planting. The first results of these progeny tests will be used in the selection of clones to be planted in the second stage of seed farm establishment. In the second and third stages of the large-scale seed plantation program the selection of clones will be based on their economic value (that is, seed production and yield improvement).
The three-stage assessment system developed in Hungary for testing clones seems promising for the selection of clones producing elite seed. In Hungary, establishment of large-scale seed orchards without such clonal testing is considered undesirable.
The first stage of the seed plantation program also permits recognition and development of techniques for treating seed orchards, especially mechanization and practices aiming at increasing yield by fertilization and pruning.
Besides Scots pine, large-scale larch seed orchards are to be established at a similar rate but on a more modest scale (Tuskó). The program for Austrian black pine, Norway spruce and Douglas fir is at the first stage of clonal testing.
Cross-breeding has begun with Scots pine and larch (Bánó and Retkes). Using four tester clones selected for their good seed production, floral biology, growth rate and resistance to disease, 4,000 crosses are being carried out annually with each Scots pine clone. Spontaneous larch hybrids in a seven-year old trial show 150 to 170 percent superiority in height and 200 percent superiority in breast height diameter when compared with the controls. Preliminary experiments are in progress on controlled crosses between provenances.
Hungarian forest tree improvement work and the experimental seed production in orchards were studied in September 1966 by a working group of Section 22 of IUFRO led by Mr. Max Hagman of Finland. During a two-day scientific session and four days of touring, 36 guests from 17 countries visited Hungary. The Hungarian Forest Research Institute has been a member of IUFRO since 1903. The idea of seed production in orchards was first raised by Syrach Larsen at the 9th Congress of IUFRO held at Budapest in 1936. It was a great pleasure that after 30 years representatives of IUFRO could be shown how the original idea has been developed in Hungary. It is considered that forest tree improvement is of outstanding importance. Work in this field may result in a rapid development of forest management.
FIGURE 3. - Aerial view of the Bajti center, part of the Sárvár Experiment Station.