Seed production of western larch in seed-tree systems in the southern interior of British Columbia

Abstract

A series of surveys and experiments were conducted on four sites to identify constraints to seed production and natural regeneration in western larch seed-tree systems in the southwestern interior of British Columbia, Canada. These surveys included pollen monitoring, a cone analysis to evaluate seed production potential, seed trapping to estimate seed rain and the installation of field germination trials to assess the effects of germination substrate and seed losses due to bird and rodent predators. Pollen shedding was found to be adequate for moderate seed production with filled seed counts ranging from 9 to 30 per cone (10–34% of all seeds/cone). No significant differences in seed yields per cone and cone characteristics were observed between uncut control stands and seed-tree stands. Seed rain was generally good in 1995, ranging from 70,000 to 4.6 million seed/ha. For the four seed-tree stands, the average filled seed percentage of the trapped seeds ranged from 9–30%. Seed rain and seed quality were much reduced in 1996. Field germination trials showed western larch seeds germinated and survived best (15–70%) on mineral soil but rodent and/or bird predation reduced germination success significantly. Germination/germinant survival on undisturbed forest floor, covered with predator exclusion screens, was intermediate.