Soil Seed Bank And Natural Regeneration Of Fragmented Evergreen Broad-Leaved Forest

The soil seed banks and natural regeneration are the main constructive parts of the forestry ecosystem,which make an indispensable part to the vegetation regeneration,succession and diffusion,playing a very important role for human's learning more about the natural regeneration ability and approach.The evergreen broad-leaved forest (EBLF),located in the subtropical area of East China,is one of China's unique vegetation types,and also an important center of global biodiversity.However,because of human activities such as urban development,highway construction and land reclamation,most of the formerly continuous EBLFs have been damaged and become fragmented. To understand the characteristics of soil seed bank and patterns of natural regeneration in the fragmented EBLFs,we selected six isolated fragments of the typical EBLFs in the mountain ranges at the boundary of Zhejiang, Fujian,Jiangxi and Anhui Provinces in East China.Methods such as field investigation,physical separation,greenhouse germination and natural germination were all used in this study.The result shows:1.Significant differences were found among fragments in seed densities with values ranging from 207±38 to 1332±337 ind./m~2,corresponding to 29～57 species.However,the seed density was 1776±344 ind,/m~2 in the continuous forest which located in Gutian Mountain National Nature Reserve,and corresponding to 46 species.The seed banks were mainly composed of tree species and shrub species,and there were rare herb species.In general,the plant species composition of the soil seed banks did not closely reflect the composition of the above-ground communities.2.The mean proportion of the upper layer(0-5cm)seeds density was 3.6 times higher than that of the lower layer(5-10cm)in the five fragments, which was higher than the continuous forest's 2.5 times.It suggested that the continuous forest was more suitable for seeds to sink down and could storage more kinds of seeds.3.There was a season variation in the soil seed bank.The continuous forest had a density peak in winter,however,which was in spring of next year for fragmented forest.4.Seedling regeneration appeared to be quite sensitive to seed bank species richness rather than seed density(P=0.005,0.159,respectively). Besides,it was affected by edge effect.4.Seed-seedling conflicts had occurred during some of these habitats if conditions or traits that were favorable for seeds were unfavorable for seedlings.Habitat fragmentation had reduced the density and species richness of seeds,however,because of more and more gaps caused by fragmentation and the following lower canopy coverage,it had positive effects on seedling establishment.