米心水青冈幼苗对光照和养分的响应

在模拟郁闭林下(L1,大约1%~2%的全日照)、林窗(L2,大约18%的全日照)、开阔地(L3,全日照)3个光照水平和每个光照水平下进行施肥(F1)和不施肥(F0)对照的6个实验处理条件下,研究了2年龄米心水青冈(FagusenglerianaSeem)幼苗在随后的两个生长季里的生长对光照和土壤养分的响应。结果显示:光照和养分对幼苗高度、基径和生物量有显著的影响。经过两个生长季,L1处理下幼苗高度增量极显著地小于L2和L3处理下幼苗高度增量。L1处理下基径和生物量的增量在处理当年秋就极显著地小于L2和L3处理下的增量,并在第二年差异继续扩大。L2和L3处理下的幼苗间的生长没有显著差异。施肥明显地促进了L2和L3处理下的幼苗的生长,但对L1处理下的幼苗没有明显的作用。这些结果说明,虽然2年龄米心水青冈幼苗能够在林下的弱光条件下生存,但生长受到了极大的抑制。幼苗在林窗的中等光照条件下能够与在开阔地全日照条件下生长的一样好或更好,这与许多耐阴的落叶树的响应一样。在比林内光照强度较高的条件下施肥或较高的土壤养分才对米心水青冈幼苗的生长和生存起作用。

Responses of Fagus engleriana Seedlings to Light and Nutrient Availability

The responses of field-grown Fagus engleriana Seem. seedlings to light and soil nutrientavailability were investigated. Two-year-old seedlings were grown for two growing seasons under sixtreatment conditions, including three light levels (L1: 1%-2% of full sunlight; L2: 18% of full sunlight; L3:100% of full sunlight), with and without fertilizer addition (F1 and F0) for each light level. The results showedthat light and nutrients had significant effect on seedling growth as measured in terms of shoot height,stem basal diameter and biomass; the mean increments of shoot height over two growing seasons weresignificantly less in L1 than in L2 and L3 (P <0.001), and in L3 than in L2 (P <0.01), but the incrementsduring the first growing season were not significantly different among the treatments; the increments ofstem basal diameter and biomass components were significantly less in L1 than in L2 and L3 (P <0.001);the increments of stem basal diameter and whole plant biomass were not statistically different between L2and L3; adding fertilizer did not affect the seedling growth under closed forest canopy, but had effect in theenvironments with more sunlight. The results suggest that (1) two-year-old F. engleriana seedlings couldsurvive the conditions of closed forest canopy, but their growth might be severely inhibited; (2) theseedlings could grow as well as or even better in small forest gaps than in open sites; and (3) fertile soilmight enhance seedling growth in forest gaps and open sites, but not under closed forest canopy.