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PROVENANCE TRIALS ON PINUS PONDEROSA DOUGLAS EX LAWSON IN ARGENTINA'S ANDEAN PATAGONIA 1

by

J. A. Enricci, N.M. Pasquini and O.A. Picco2, and V. Mondino3

Seeds of 25 provenances of Pinus ponderosa Douglas ex Lawson were procured in 1980 from the US and Canadian Forest Services for provenance trials to be conducted on this species at five representative sites in western Chubut and Río Negro. Local seeds from the plantations "Isla Victoria" in Neuquén and "Trevelin" in Chubut were used as controls. Traditional local seedling production and final planting techniques were used, and, 18 years later, survival rates were very high with no anomalies detected. The final observations on these trials, which were established in 1982, showed that, in general, provenances from the Cascades area of Washington State performed better on the most favourable sites, and that seeds from the Blue Mountains in eastern central Oregon did better on the less favourable sites. On all sites, the imported seed out-performed the local provenances, though only significantly so on one site. In conclusion, the health and growth species response of these seeds was excellent, and they are recommended for plantations planned in the region.

INTRODUCTION
The introduction of forest exotics in Argentina's central Andean-Patagonian region dates back to the early twentieth century with the arrival of Welsh immigrants from the east and from Río Chubut who distributed Salix fragilis L. Immigrants from northern and central Argentina introduced broadleaf and conifer species of US and European origin. From 1930 to 1950, forest exotics were intensively planted on nearly one thousand hectares by the National Forestry Administration at its forest stations "Cerro Chapelco" in Neuquén, "General San Martín" in Río Negro, and "Trevelin" in Chubut, and by the National Parks Administration at Nahuel Huapi National Park in Isla Victoria, Lanin National Park in Pucará, and Los Alerces National Park in Villa Futalaufquen. Today, these stands of Pinus, Pseudotsuga, Tsuga, Picea, Larix, Abies, Sequoiadendron, Cupressus. Libocedrus, Thuja, Juniperus, Chamaecyparis, Salix, Populus, Betula, Quercus, Fraxinus, Acer, Ulmus and Robinia etc. constitute a veritable showcase for the excellent performance of most of these introductions (Enricci, 1994).

Unfortunately, the seeds used were generic seeds, and there are almost no exact data on their origins, even though they were used to produce non-genetically improved seed. Standing plantations of Pinus ponderosa in the region should therefore not be considered as base populations suitable for selection and crosses, as the material is highly heterogeneous, and no comparisons have been made with other provenances which might perform better on specific sites, quite apart from the unknown origin of this local seed. Two lots of seed from these plantations were used , however, as controls in the trials reviewed in this paper.

The main objective of this experiment was to establish with some exactitude those provenances which best met the main objectives in each region, (generally concerning health and behaviour).

MATERIALS AND METHODOLOGY
The trial methodology was that recommended by the experts. According to Kemp in J. Burley et al (1979), the purpose of species and provenance trials should be to reduce a great many possible genotype/environmental combinations to a few proven species or provenances suitable for the production of desired forest products on relevant sites.

Table 1 characterizes the provenances of those Pinus ponderosa var ponderosa seeds which produced a sufficient number of seedlings in the nursery to qualify for use in trials (excepting lot 8, which concerns var. scopulorum). Of the 25 seed lots imported, 18 met this requirement. Lots C 25 and C26 were used as local controls, in accordance with Burley et al, 1979. Figure 1 illustrates the natural distribution of P. ponderosa and the locations of the provenances used in the trial.

Table 1. Seeds of Pinus ponderosa var. ponderosa used in trials (provenances and controls)

The seedlings were produced at INTA's "Trevelin" Forest Station, using methods traditional in the region. As recommended by Patiño Valera and R. Garzón (1976), the following data were recorded: seeding and emergence dates, total number of seedlings, height, eventual anomalies, health status. The seeds were sown in the spring (13 October 1980) in nursery beds at densities of 70gr/m2. The resulting seedlings (1 + 0) were transplanted on 1 October 1981 into nursery borders at spacings of 0.1 m x 0.1 m.

The final site selection followed the indications of Greaves A. and Hughes J.F. (1979) for representative sites in terms of geomorphology, soil, climate, and existing natural vegetation. Both Table 2 and Figure 1 illustrate the characteristics and location of the four sites chosen for the establishment of the trial plots.

Table 2: Site characteristics of trial locations:

Sites I and III are characterized as "more favourable" and sites II and IV as "less favourable" for the growth of this species in accordance with relief and soil characteristics.

Figure 1: Natural distribution of Pinus ponderosa Douglas ex Lawson and original locations of provenances tested (the broken line separates v. ponderosa (West) from v. scopulorum (East) (US Forest Service, 1965)
Note: Provenances with the same geographical location but at different altitudes:
A. Includes provenances No. 2 and 14
B. Includes provenances No. 15, 18 and 19
C. Includes provenances No. 4 and 16.
D. Includes provenances No 11 and 13

In September 1982 the final planting was done in accordance with traditional local methods. Holes were first dug with a sharp-edged spade at spacings of 3 m x 3 m. A randomized block design with four repetitions was used (each block containing plots with 9 plants replicating the provenances). A square plot shape was selected, in accordance with Barret, W. (1973), Wright, J. (1976) and Burley, J. et al, for areas of 81 m2 each.

The following data were recorded: survival (measured every two years after planting), total mean height of the two dominant trees in each plot (every four years), diameter at breast height (each time height was measured once the trees reached 12 years of age), stem and branch characteristics, and health status. The last measurements were made in 1999, given the fact that as of 16 years from the date of planting, at standard plantation spacings, competition was very heavy among individual trees on the plots, with trees one third again as big as in a normal cutting cycle for this species on these sites. The data-processing software used was SPSS/PC + Statistics. The relative significance of the different provenances was arrived at through variance analysis as interpreted by the Rango test, 5% Duncan multiple, as recommended by Burley, J. et al, (1979) and Ditlevsen, B. (1980).

Figure 2: Site location of the trial plots1

RESULTS
At the nursery stage (1980-81):

The dates of emergence were 6-20 November 1980. The number of plants obtained at transplant on 1 October 1981 was 12,831, with a mean aboveground height of 5.1 cm., and no observed anomalies. The following year 12,128 plants were left for the final planting, with a very high survival rate of 95% for all provenances. The mean aboveground height of var. ponderosa was 7.8 cm with average values per provenance ranging from 6.2 to 9.4 cm, whereas for the scopulorum variety it was 3.5 cm.

CONCLUSIONS
Concerning a possible juvenile/adult size ratio, in comparing the nursery data (two years) to the plantation data (16 years), a very high and significant correlation was observed for the "Black Hills" provenance (No. 8) for the scopulorum variety. The same can not be said of the other provenances.

Survival rates in the nursery as at the various plantation stages were very high, ranging from 95% at the time of final planting to 83% 11 years later, with a final figure of 78% after 16 years in the plantation. The failure rate was also similar for all provenances, though the rate of failure was higher on Sites II and IV due to the less favourable conditions, and to the incidence of attacks by the "European hare" (Lepus europaeus) on Site II (Mallín Grande) and by "European red deer" (Cervus elaphus) on Site IV (Lago Fontana).

No health problems were observed for any provenance at any of the four test sites.

Generally speaking, the trends for all parameters observed in 1994 when the plantation was 11 years old held true five years later when the plantation was 16 years old. This plus the heavy competition between trees rules out the need for new measurements.

Concerning the height and DBH data, there was a discontinuous variation among the provenances, with a general trend toward better performances by the Washington State provenances from the eastern slopes of the Cascades on the more favourable sites of Mallín Cumé and Río Pico.

Provenances from the central western Blue Mountains area of Oregon State performed better on the less favourable sites of Mallín Grande and Lago Fontana. There were some exceptions for both situations, with more variation between sites than between provenances.

On all sites, the imported provenances were observed to outperform the best response of the local control, though the difference was statistically significant only in Río Pico.

At 16 years from final planting, var. scopulorum development was observed to be significantly poorer at all sites, and it is therefore not recommended that local tree nurseries import seeds of this variety.

1Received July 2000. Original language: Spanish
2National University of Patagonia (UNPSJB), Esquel, Chubut, Argentina
3National Institute of Agricultural Technology (INTA), Trevelin, Chubut, Argentina

BIBLIOGRAPHY
Barret, W. (1973): Variación geográfica en Pinus elliottii Engelm. y Pinus taeda L. In: Suplemento Forestal Nº 7: 3-8. IDIA. INTA. Buenos Aires. Argentina.

Ditlevsen, B. (1980): Experimental Designs. In: Forest Tree Improvement. FAO Forestry Paper Nº 20. FAO. Rome. Italy.

Enricci, J. (1994): Posibilidades para la forestación en la subregión central del ecosistema andino-patagónico. P.T. Nº 14. Ed. CIEFAP. Chubut. Argentina.

Greaves, A. and Hughes, J. F. (1979): Site Assessment in Species and Provenance Research. In: A Manual on Species and Provenance Research with particular reference to the Tropics Tropical Forest Papers Nº 10. Commonwealth Forestry Institute. University of Oxford. U.K.

Kemp, R.H. (1979): Seed Procurement for Species and Provenance Research. In: A Manual on Species and Provenance Research with particular reference to the Tropics, pp. 32-48. Compiled by Burley, J. and Wood, P.J. Tropical Forest Papers Nº 10. Commonwealth Forestry Institute. University of Oxford. U.K.

Patiño Valera and Garzón, R. (1976): Manual para el establecimiento de ensayos de procedencias. INIF. México.

U.S. Forest Service (1965): Silvics of Forest Trees of the United States. In: Agriculture Handbook Nº 271. U.S. Department of Agriculture. Forest Service. Washington D.C. USA.

Wright, J. (1976): Introduction to Forest Genetics. Academic Press Inc. USA.

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