Heterogeneity in Soil Seed Banks in a Mediterranean Coastal Sand Dune

Characteristics of total soil seed banks and permanent soil seed banks in three microhabitats in a Mediterranean coastal sand dune were investigated by using natural germination method combined with physically scanning separation method. The composition and structure of soil seed banks were analyzed between the microhabitats by using functional group method. The distribution patterns of soil seed bank were also analyzed between the microhabitats. We also analyzed the relationship between seed size and seed persistence in soil. The results show greatly spatial heterogeneity existed in soil seed bank of the Mediterranean coastal sand dune, even in the same microhabitats seed distribution was uneven. Sometimes a great difference occurred between them. Microhabitats significantly affected the distribution patterns of total soil seed banks and seed banks of the functional groups. The open area generally had the greater densities of seeds, but the seed densities under shrub and in trail were lower than that in the open area. Legumes seeds accounted for 76.0% total persistent seed banks. Annual and perennial grasses produced transient seed banks as no seeds were retrieved from the sieved soils. Seed persistence of legumes, umbeliferaes, perennial forbs, compositaes, annual forbs, crucifer decreased gradually. They were 50.1%, 45.6%, 40.6%, 6.3%, 5.6% and 0.6% respectively in the soil. There was a positive relationship between seed size and seed persistence. Bigger seeds had higher persistence, and vice versa.

Effects of degradation and species composition on soil seed density in the alpine grasslands, China

Grassland degradation can alter the structure and function of ecosystem and soil seed bank.Therefore,estimating the role of soil seed bank in vegetation regeneration of degraded grasslands is crucial.We selected grasslands with three levels of degradation,namely non-degraded(ND),mildly degraded(MD),and heavily degraded(HD)to analyze the effect of grassland degradation on soil seed bank,as well as the role of soil seed bank on vegetation regeneration of the alpine grasslands,China.Soil samples from each level were collected in May,before seedling emergence,in August,after completion of transient seed bank germination,and in December,after seed dispersal,to determine the seed density and species composition through germination experiment.Result showed that a total of 35 plant species was identified,including 15 species observed in both soil seed bank and above-ground vegetation.A total of 19,15,and 14 species of soil seed bank were identified in December,May,and August,respectively.The most abundant species in soil seed bank were Compositae(5 species),followed by Poaceae(4 species),and Cyperaceae(3 species).Degradation level has no significant impact on species richness and Shannon-Wiener index of soil seed bank.In addition,sampling month and grassland degradation affected soil seed bank density,in which December>May>August,and ND>MD>HD,indicating that density of transient seed bank was greater than persistent seed bank.Soil seed bank density of surface layer(0–5 cm)accounting for 42%–72%of the total density,which was significantly higher than that of deep layer(5–10 cm).Similarity of species composition between vegetation and soil seed bank was low,and it increased with degradation level(ranged from 0.14 to 0.69).We concluded that grassland degradation affects soil seed bank density more than species diversity,and soil seed bank contributed slightly to vegetation regeneration of degraded alpine grassland.Therefore,it is unlikely that degraded alpine meadow can be restored solely through soil seed bank.