作 者 ：赵丽娅, 李兆华, 赵锦慧, 赵哈林, 赵学勇
期 刊 ：植物生态学报 2006年 30卷 4期 页码：617-623
Keywords:Sandy grassland, Grazed, Enclosed, Soil seed bank, Standing vegetation,
摘 要 ：该文研究了科尔沁沙质草地在放牧和围封条件下土壤种子库密度、组成及其与地上植被的关系。结果表明：1）放牧草地植物种数22种，围封草地植物种数30种，围封使土壤种子库植物种数增加了36%；2）放牧草地土壤种子库密度为16 149±1 900有效种子数•m－2, 围封草地土壤种子库密度为20 657±3 342有效种子数•m－2，比放牧草地增加了28%。放牧和围封草地种子库组成密度均以一年生植物为主（分别占99%和98%的比例），多年生植物所占的比例很小；3）放牧草地种子库的Shannon-Wiener指数和丰富度指数分别为0.836 3和4.954 9，明显小于围封草地的0.968 2和7.226 0，表明自由放牧导致物种多样性下降；4）放牧和围封草地土壤种子库密度与地上植被密度均存在显著的相关性（p＜0.001）。表明了随着土壤种子库密度的增加, 地上植被密度随之增加,放牧草地地上植被密度78%的变异可归结为土壤种子库密度的变异, 而围封草地地上植被密度58%的变异可由土壤种子库密度的变异来解释。
Abstract:Background and Aims In Horqin sandy land, vegetation degradation usually occurs in improper
management regimes under fragile conditions, e.g. clearing and grazing. However, few
information is available about the effects of grazing and enclosing on the structure and
performance of soil seed banks in the semi-arid desert environment. Therefore, a field
experiment was conducted in grazed and enclosed grasslands to examine the structure and
performance of soil seed banks.
Methods In late March 2003, three parallel 200-m line transects (20 m apart) were
established in two experimental sites, grazed and enclosed grasslands. For each transect,
20 sampling points were set up at 10-m intervals, and a soil sample o f 5 cm in depth and
20 cm × 20 cm in dimension was collected from each sampling point. All soil samples were
transported to the laboratory in open plastic bags and chopped and sieved (mess width is
0.2 mm) soon. The sieved soil samples were placed in plastic germination pots (33 cm in
diameter and 12 cm in depth) and spread evenly to form an approximately 1 cm thick layer in
individual pots. Pots were placed in an unheated greenhouse for seed germination. Pots were
watered daily with a very fine nozzle in the afternoon. Emergent seedlings were identified
to species and carefully removed from the pots. Seed germination and seedling
identification were carried out continuely in the following three months. However, some
unidentifiable seedlings remained longer in the pots until they were identified. The
density of the existing seed bank was expressed as the number of viable seeds per square
meter. At each site, the frequency of species in the soil seed bank was determined in terms
of the 60 sampling points or the 60 quadrats.
Key Results The study was conducted in grazed and enclosed grasslands to examine the
relationship between density and composition of soil seed bank and vegetation in Horqin
sandy land, Inner Mongolia. The results showed that there were 22 and 30 plant species in
seed banks in the grazed and enclosed grasslands, respectively. In the grazed and enclosed
grasslands, the seed bank density were 20 657±3 342 and 16 149±1 900 viable seeds•m-2,
respectively, with annual herbaceous plants dominating in both sites (occupied 99% and 98%,
respectively) Shannon-Wiener index and richness of the grazed grassland were 0.836 3 and
4.954 9, respectively, which were distinctly lower than those in the enclosed grassland
(0.968 2 and 7.226 0), suggesting negative impacts of grazing on seed bank diversity. Seed
bank density strongly related to the standing vegetation density in both grazed and
enclosed grasslands (p＜0.001), indicating the standing vegetation density increased with
the increase of seed bank density. Differences in seed bank density accounted for 78% and
58% of the variance of standing vegetation density in grazed and enclosed communities,
respectively.
Conclusions Our results showed that adoption of enclosure management practice significantly
increased density and species diversity of the seed bank, compared with the grazed
grassland. Therefore, reseeding, enclosure and other management steps should be used to
speed up the restoration process of the degraded grassland.