荒漠草原灌丛沃岛的结构特征和生态效应

Structural characteristics and ecological effects of a shrub-fertile island in a desert steppe

荒漠草原地区草地的灌丛化使得草地资源空间分布具有异质性,并且灌丛的自持能力也逐渐得到了增加。荒漠草原灌丛沃岛是荒漠草原地区灌木灌丛下限制性土壤资源的显著聚集现象,其中的资源为土壤水分、养分、微生物、动物以及由灌丛带来的非生物环境等的总和。沃岛集聚养分,改善土壤构造,在养分的空间和养分循环中发挥着重要的生态和水文效应,成为许多生物物种,包括草本植物和小型动物的庇护所,这种效应被称之为"沃岛"效应。"沃岛"效应的发生很可能促进了灌丛化草地的形成和维持,同时也加速了草原的荒漠化过程。"沃岛"效应的存在是荒漠草原受损生态恢复与重建的重要基础和依据。学者对于"沃岛"效应引起的土壤资源的异质性分布研究较深,但对于养分在灌木植物下土壤表层的积累研究较浅。如何把握"沃岛"效应各个复杂过程中植物、土壤和土壤生物扮演的确切角色,还亟待解决。本文从"沃岛"的概念和形成机制出发,对"沃岛"的结构特征和生态效应以及土壤与植被系统的关系进行了总结,对于深入了解"沃岛"效应的机理具有重要的意义,也对荒漠草原地区的植被演替和恢复重建具有重要的生态学意义,同时也为荒漠草原地区的水土治理提供基础理论。

The conversion from grasslands to shrubberies in desert and grassland areas makes the spatial distribution of grassland resources possess heterogeneity with an increase in the self-sustainability of bushwood.Desert steppe scrub islands are significant aggregations of restricted soil resources under shrubs in desert steppes,among which the resources are the sum of soil moisture,nutrients,microorganisms,animals,and abiotic environment brought by shrubs.“Fertile islands”gather nutrients,improve soil structure,and have important ecological and hydrological effects on the space and circulation of nutrients.They are a shelter for many biological species,including herbaceous plants and small animals;this effect is called“fertile islands”effect.The occurrence of the“fertile island”effect probably promotes the formation and maintenance of thicketed grasslands and also accelerates the desertification process of grasslands.The existence of the island effect is an important basis for the restoration and reconstruction of damaged ecology in desert steppes.Scholars have fully studied the heterogeneity distribution of soil resources caused by the island effect,but the study of the accumulation of nutrients in the soil surface layer under shrubs is relatively little.The exact roles played by plants,soil and soil organisms in the complex process of“fertile island”effect need to be elucidated.Starting from the concept and formation mechanism of a“fertile island”,this paper summarizes the structural features and ecological effects of fertile islands,as well as the relationship between the soil and vegetation systems.It is important to understand the mechanism of“fertile islands”;they have great ecological significance in the vegetation succession,restoration,and reconstruction in desert steppes.Meanwhile,it also provides the basic theory for soil and water control in desert steppes.