花楸树种子散布、萌发与种群天然更新的关系

Sorbus pohuashanensis seed dispersal and germination and their relationships with population natural regeneration

花楸树是我国东北林区重要的非木质资源树种,其实生天然更新不良.本文通过研究花楸树种子散布、土壤种子库及种子萌发出土过程,分析花楸树实生天然更新的影响因素.结果表明:自然散落的花楸树果实96.1%分布于母株2 m范围内,凋落物层和土壤表层(0～2 cm)的种子数占土壤种子库总数的97.0%;不同季节花楸树土壤种子库种子数量差别很大,当年11月上旬种子数量最多,达(257.7±69.2)粒.m-2;翌年7月下旬种子数量最少,仅为(2.9±2.9)粒.m-2;温度不是花楸树种子萌发出土过程的限制因子,0℃～5℃时幼苗出苗率达(67.5±6.6)%,但对其出苗速率影响显著.土壤含水量为50%时,花楸树出苗率最高,达(74.7±4.2)%;含水量为60%时,幼苗死亡率最低,为(32.6±0.6)%.花楸树种子的散布格局和土壤种子库的时空分布格局影响种子的萌发出土过程,进而影响其种群的天然更新.

Sorbus pohuashanensis is an important non-timber tree species in Northeast China,but poor in natural regeneration via seed dispersal.In this paper,a field observation was made on the seed dispersal of S.pohuashanensis,its seedling emergence,and soil seed bank,aimed to study the factors affecting the natural regeneration of this tree species.There were 96.1% of naturally dispersed S.pohuashanensis seeds distributed within the range of 2 m around the stock tree,and 97.0% of the seeds in soil seed bank distributed in litter layer and 0-2 cm surface soil.The seed quantity in soil seed bank differed greatly with seasons,being the maximum [（257.7 ± 69.2） seeds per square meter]in early November in the year of seed dispersal,and the minimum [only（2.9 ±2.9） seeds per square meter]in next July.Temperature was not the limiting factor affecting the seedling emergence of S.pohuashanensis [at 0 ℃-5 ℃,the seedling emergence percentage could reach（67.5 ± 6.6） % ],but strongly affected the seedling emergence rate.The most proper soil moisture content for the seedling emergence was 50%,under which,the seedling emergence percentage could reach（74.7 ± 4.2） %.When the soil moisture content was up to 60%,the seed-ling mortality was the lowest（32.6% ± 0.6%）.All the results suggested that the seed dispersal pattern of S.pohuashanensis and the spatiotemporal dynamics of soil seed bank could affect the seedling emergence of the tree species,and further,affect the population natural regeneration of S.pohuashanensis via seed dispersal.