Effect of test environment on expression of clines and on delimitation of seed zones in Douglas-fir

Abstract

Clinal models of population structure in an indigenous tree species can be used to delineate seedcollection zones and breeding zones, and to devise transfer rules. Models may be developed by growing populations in test environments; however, a clinal description may be a function of test environments as well as of population genotypes. This possibility was studied by growing seedlings from 40 populations of northwestern U.S. Douglas-fir (Pseudotsuga menziesii var. 'menziesii' [Mirb.] Franco) in eight nursery-bed treatments which contrasted air and soil temperatures and nutrition. Growth traits measured were stem diameter, top height, and dry weight; phenological traits were bud-burst and bud-set dates, extension period, and extension period midpoint. Population samples interacted significantly with soil temperature for growth traits, and with soil and air temperatures combined for phenological traits. Interactions were at least partly explained by complex clinal associations of seedling performance with elevation, with latitude, and with distance from the ocean of the populations sampled. Both the complexity and the gradient of the clinal pattern depended on the trait and on the specific test environment.The clinal patterns of greatest complexity were expressed in warm air and soil treatments. Dry top-weights of population samples were associated with latitudes for samples grown in warm soils, but this relationship was not apparent in cool soils. A discrepancy in bud-burst dates between extreme coastal and more inland populations was greatest in warm soil-warm air treatments and was negligible in cool soil-cool air treatments. Populations X temperature interactions were attributed to the differential response of population samples to spring temperature and photoperiod. It is proposed that first attempts at devising a model can be based on nursery or growthchamber tests, and that test environments should stress contrasting photo- and temperature-regimes.The estimate of clinal structure in Douglas-fir suggests that there is more risk within northwestern U.S. in moving provenances east-west than north-south, that this risk increases with elevation of provenances, and that north-south transfers are more critical near the coast than inland.

Geographic Variation and Local Growth Superiority for Coastal Douglas-fir – Rotation-age Growth Performance in a Douglas-fir Provenance Test

“…High-elevation provenances grew poorly at low-elevation sites in general. Such macro-geographic variation pattern generally follows the results revealed by juvenile traits (e.g., CAMPBELL and SORENSEN, 1978;GRIFFIN, 1978;ST CLAIR et al, 2005). Based on the empirical equations in Table 6, moving a provenance away from its original sites 500 m in elevation or 800 km in latitude would cause on average 9 % loss in total volume per plot at rotation.…”

“…The potential problems with "local is best" recommendations are: (1) there is a risk of encouraging the establishment of populations that do not harbor sufficient genetic variation and evolutionary potential, and therefore reduce the potential genetic gains though long-term breeding; and (2) it increases the cost of tree improvement beyond the level necessary. While results from several nursery or short-term provenance or genecology studies led to conclusions of local adaptation in coastal Douglas-fir (e.g., CAMPBELL and SORENSEN, 1978;GRIFFIN, 1978;SILEN and MANDEL, 1983;ST CLAIR et al, 2005), early reports on the longterm provenance studies suggested that maladaptation was not a big problem unless seed transfer involved large altitudinal distances. Several tree breeders (WOODS, 1993;STONECYPHER et al, 1996) advocated using far larger breeding zones in this region than the original IFA-progressive plan.…”

“…Results from short-term field tests (e.g., HERMANN and LAVENDER, 1968;GRIFFIN and CHING, 1977;CAMPBELL and SORENSEN, 1978;CAMP-BELL, 1979;SILEN and MANDEL, 1983;ST CLAIR et al, 2005) showed that genetic variation in growth and several adaptive traits is apparently patterned along geographic gradients described by elevation, latitude, and distance from the ocean. However, these short-term tests estimated only the immediate and dramatic effects of maladaptation at seedling or juvenile stage, but could not estimate the cumulative effect over long growth periods (ADAMS and CAMPBELL, 1981).…”

Ecological adaptations in Douglas-fir (Pseudotsuga menziesii var. glauca) populations

“…According to Campbell and Sorensen (1978), the need for seed zones in artificial afforestation was recognized long ago. In seed zoning, forest lands are stratified into units within which interactions between genotype and environment approach zero.…”

Estimation of population structure in coastal Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco var. menziesii] using allozyme and microsatellite markers

“…level of phenotypic variation that is strongly associated with geographic, topographic, and climatic features (Campbell and Sugano 1975;Campbell and Sorensen 1978;Steiner 1979;Li and Adams 1993;Aitken and Adams 1997;Anekonda et al 2000;St. Clair et al 2005;St.…”