荒漠草原区4种植物群落土壤种子库特征及其土壤理化性质

土壤种子库作为地上植被更新的潜在种源，在植被自然恢复和演替过程以及生态系统建设中起着重要作用。以宁夏盐池县荒漠草原区4种植物群落为研究对象，通过对封育16年后植物群落土壤理化性质的变化与其土壤种子库的特征之间的关系的探讨，揭示荒漠草原植物群落的土壤种子库分布特征和演替趋势，以及土壤质量的改变如何影响土壤种子库特征。研究结果表明：（1）不同植物群落土壤种子库物种组成及种子密度不同，同一物种在不同植物群落土壤种子库中出现时种子密度也存在差异；禾本科、菊科、藜科植物种在4种植物群落土壤种子库中出现比例均较高，分别占到26.19%、21.43%和19.05%，占总物种数的66.7%；灰绿藜、冰草、碱蓬在4种植物群落土壤种子库中均有出现。（2）4种植物群落土壤种子库中多年生植物和一年生植物种子居多，灌木、半灌木植物种较少。（3）4种植物群落土壤种子库中物种数和种子密度均表现为：芨芨草群落 > 苦豆子群落 > 油蒿群落 > 盐爪爪群落；且随着土层的加深，4种植物群落土壤种子库中物种数和种子密度均呈递减趋势。（4）4种植物群落土壤种子库中Shannon-Wiener指数、Simpsin指数、Pielou指数和Patrick指数均表现为芨芨草群落 > 苦豆子群落 > 油蒿群落 > 盐爪爪群落。此外，芨芨草群落土壤种子库与油蒿群落土壤种子库相似性最高，油蒿群落与盐爪爪群落的最低。（5）土壤种子库物种多样性特征指数与土壤pH、含水量、碱解氮呈正相关，与土壤电导率呈负相关，其中土壤pH和电导率对种子库物种多样性的影响较大。荒漠草原封育以后，土壤种子库中植物种数、种子密度和物种多样性均呈增加趋势，且以多年生植物和一年生植物种子居多；禾本科和豆科植物的物种数和种子密度大于菊科和藜科，这表明围封后牧草品质改善，植物群落正向演替。

Analysis of soil seed bank characteristics and soil physical and chemical properties of four plant communities in a desert steppe region

The soil seed bank (SSB), as a potential provenance, plays an important role in the natural recovery and succession of vegetation and ecological restoration. In this study, four plant communities were evaluated in a desert steppe area in Yanchi County, Ningxia. We investigated the relationship between soil physical and chemical properties of plant communities fenced for 16 years to reveal the SSB distribution characteristics of the desert grassland community and succession trend and how changes in soil quality affect SSB characteristics. The results showed that (1) the species composition and seed density of SSBs in various plant communities were different, and the seed density of the same species was different in various plant communities. Moreover, the species proportion of four types of plant communities in SSB included Gramineae, Compositae, and Chenopodiaceae (26.19%, 21.43%, and 19.05%, respectively), accounting for 66.7% of the total species. (2) Many perennial and annual plant seeds, and few shrub and semi-shrub seeds were found in the SSBs of the four communities. (3) The species number and seed density in the SSBs of the four plant communities were as follows:Achnatherum splendens community > Sophora alopecuroides community > Artemisia ordosica community > Kalidium foliatum community; the species number and seed density showed a decreasing trend with soil depth. (4) Four indexes (Shannon-Wiener, Simpson, Pielou, and Patrick) indicated the same tendency, that is, A. splendens community > S. alopecuroides community > A. ordosica community > K. foliatum community. In addition, the SSB of A. splendens community had the highest similarity to that of A. ordosica community, but the SSB of A. ordosica community had the lowest similarity to that of K. foliatum community. (5) The soil species diversity index of SSB was positively correlated with soil pH, water content, and available nitrogen and negatively correlated with soil electrical conductivity. Soil pH and electrical conductivity had a significant effect on species diversity in the SSBs. After enclosure, the species number, seed density, and biodiversity of SSB increased, especially, those of the perennials and annuals; the species number and seed density of Gramineae and Leguminosae were both greater than those of Compositae and Chenopodiaceae. All the results indicated that fencing improved not only the grasses but also positive succession.