Bistable-state of vegetation shift in the desert grassland-shrubland anthropogenic Mosaic area

以柠条锦鸡儿（Caragana korshinskii）灌丛引入形成荒漠草原-灌丛地镶嵌体为研究对象，选择其内部荒漠草地（DG）、草地边缘（GE）、灌丛边缘（SE）、灌丛地（SL）为试验样地，开展荒漠草原向灌丛地人为稳态转变过程土壤水分与植被变化特征研究。结果如下：各样地0-200 cm土层水分含量随着转变过程呈显著降低趋势（P<0.05），其中荒漠草地、草地边缘和灌丛边缘样地的土壤水分均在秋季雨水补充期增加，灌丛地由于深层土壤水分过度消耗而愈加降低，且灌丛边缘和灌丛地深层水分显著低于荒漠草地、草地边缘（P<0.05），垂直动态不显著；地上植被随样地转变除优势度指数表现为灌丛地多样性、均匀度、丰富度指数均显著低于各样地（P<0.05），多年生优势草本蒙古冰草（Agropyron mongolicum）、短花针茅（Stipa breviflora）逐渐被一年生草本刺藜（Dysphania aristata）、猪毛蒿（Artemisia scoparia）所代替；土壤种子库萌发种类随样地转变逐渐减少，种子库密度则显著升高（P<0.05），灌丛地以一年生草本植物为主（占总密度的97.51%），荒漠草地则以多年生草本萌发为主，且各样地土壤萌发种子库及多年生草本多集中于0-5 cm土层（P<0.05）；转变过程荒漠草原和灌丛地植被地上地下相似度分别为0.14和0.19，均显著低于两边缘样地0.35，较两边缘样地群落更为稳定，呈现草原灌丛化过程中草地-灌丛共存的植被双稳态特征。;In this paper, desert grassland, grassland edge, shrub and shrubland were selected as four transition sites in a typical anthropogenic grassland-shrubland mosaic steppe of eastern Ningxia, China. The soil moisture, above-vegetation seed bank investigated to understand the response vegetation state transition. results showed that moisture 0-200 cm layer each site presented significant downward trend with (P<0.05), edge increased autumn rain supplement, while decreased due depletion deep water by shrubs. significantly lower than those there no vertical distribution dynamics these two sites. Except for dominance index, diversity, uniformity, richness indexes other three (P<0.05),and perennial dominant herbs Agropyron mongolicum, Stipa breviflora gradually replaced annual Dysphania aristata Artemisia scoparia. germination species number gradually, however, density banks germinated dominated (accounting 97.51% total density), which mainly herb. And herb concentrated 0-5 (P<0.05); similarity coefficient (SC) between above-ground underground 0.14 0.19, respectively, SC (0.35), relatively stable sites, occurring bistable shift process