Abstract:

Aims Seedfall of woody plants often fluctuates considerably from year to year and from site to site. These variations may have strong effects not only on the recruitment of the plant populations themselves, but also on the community composition and structure. Our objective was to elucidate seasonal, annual and spatial variations of seedfall in broad-leaved evergreen forest in Gutianshan Nature Reserve of Zhejiang Province over four years.
Methods Seed rain was censused weekly since June 2006, using 130 seed traps set along 2.3 km of trails within the Gutianshan 24 hm² subtropical evergreen forest plot. Each seed trap consisted of a square, 0.5 m² Poly Vinyl Chloride (PVC) frame supporting a shallow, open-topped, 1-mm nylon mesh bag suspended 0.8 m above the ground. Because of heavy snowfall in February 2008, seed traps were damaged, and all seed traps were reset. Therefore, seed rain data were absent from February to April 2008. We summarized four years of seed rain data from June 2006 to August 2010.
Important findings There were a total of 124 227 seeds over the four years, belonging to 63 species, 51 genera and 29 families, and the Pearson correlation between adult tree basal area and seed production was significant. There was a marked peak in the number of seeds and species in each year in the dry season (autumn), but there were also ten species that dispersed their seeds in the wet season. Different species had different fruiting dates. Based on four years of seed rain data, annual variation in seedfall (CV_years) on Gutianshan was substantial (CV_years > 75% for almost all species), and the median coefficient of variation of annual seedfall was 1.72. Spatial variation was also great, and the median coefficient of spatial variation in seedfall among traps was 8.06. Spatial variation in seedfall density was greater than annual variation for almost all species. The rarity of seed-bearing adults, variation in seed deposition with distance, and different topography might be the most important sources of this spatial variation. Comparing with Barro Colorado Island tropical forest seed rain, Gutianshan data supported the hypothesis that annual variation in seedfall is lower in the tropics than at higher latitudes.

Key words: annual variation, seasonal variation, seed production, spatial variation, subtropical trees