短期极端干旱事件干扰下退化沙质草地群落抵抗力稳定性的测度与比较
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甘肃省自然科学基金资助项目(0809RJZA009);兰州理工大学科研发展基金资助项目(SB05200410);国家973资助项目(G2000048704)


An example for study on vegetation stability in sandy desertification land: determination and comparison of resistance among communities under a short period of extremely aridity disturbance
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    摘要:

    利用对不同沙漠化程度的6个沙质草地群落样地在经历时间尺度约为0.5个生长季、强度约为正常降雨量15%的短期干旱事件干扰前后2a同期进行的植被调查资料,从抵抗力概念出发构建抵抗力指数,尝试性地对沙漠化过程退化沙质草地群落在短时间尺度极端干旱事件干扰下的抵抗力稳定性进行了量化测定与比较。结果表明:6个不同沙漠化程度沙质草地群落以活生物质盖度计算的抵抗力指数,除群落4由于其组成以差吧嘎蒿为主而抵抗力指数较高为0.8615,其余5个群落抵抗力指数较小,在0.1760-0.0217之间,且随沙漠化程度的提高,群落抵抗力指数减小,即群落稳定性下降;而以立枯和地面枯落物等非活生物质组分计算的抵抗力指数较高,分别在0.4394-2.4128和0.7983-5.3810之间,且在群落之间的变化与群落沙漠化程度并无一致性,这恰当地反映了立枯和地面枯落物等非活生物质受干旱影响较小、对维持群落功能稳定起着重要作用的事实。对群落抵抗力来源与构成进行的分析表明,群落抵抗力主要由多年生植物构成。通过本研究对群落抵抗力以群落内部生态过程为基础进行的数量测定与比较,证明生物多样性的损失,特别是多年生植物的严重缺失,是沙漠化过程植被抵抗力稳定性降低的主要机理和根本原因。研究结果从相反方面说明生物多样性促进退化沙质草地群落对短期极端干旱事件干扰的抵抗力稳定性,这一结论是对“多样性的生态系统功能”、“多样性与稳定性”等生态学基本问题给出的以所研究的特定生物气候带内退化沙质草地群落为例证的回答。

    Abstract:

    Ecological stability, changes of eco-system under natural and human-induced disturbances such as fire, grazing, cultivation etc., involved in how and to what extent human can utilize natural resources but without inducing eco-system degradation or collapse, is a problem worthy of study. From the reaction of an eco-system to disturbances, it has been concluded that ecological stability could be defined as resistance and resilience. Because of many complicated factors such as the type, the intensity, the temporal scale and spatial scale of disturbances, it has been difficult to make qualified measurements for a real community. Therefore, researches related to resistance and resilience has been stopped at concepts, and studies on qualified resistance and resilience about a real community were scarce. In order to make an tentative example for study on this topic, 6 communities in different desertification stage were sampled in a sandy desertified region, and community investigation was done one time for every half month from the beginning to the end of growth season. With the investigation data made at the same time in continual two years before and during a special period when climate was extremely arid, an resistance index, which indicates the resistance stability of the 6 communities, were defined and calculated as the ratio of vegetation data at the same time in two years. It could be expressed as: resistance index = the vegetation data at the same time in the year during which the aridity event took place / the vegetation data in the year before aridity event took place. Results showed that, the resistance indexes of the other 5 communities calculated with living biomass coverage were between 0.1760 and 0.0217, decreasing with enhanced desertification except for community 4, of which the resistance index was higher with a value of 0.8615 because of Artemisia halodendron Turcz. ex Bess, an semi-shrub species which was dominated in the community. While the resistance indexes calculated with standing litter coverage and ground litter coverage were between 0.4394-2.4128 and 0.7983-5.3810 respectively, showing no consistent trend with the desertification level of the 6 communities, but be in line with the fact that standing litter and ground litter was less affected by drought and more stable in this extremely arid disturbance event. By further regression analysis made between living biomass coverage and each part of its components such as annual plants coverage and perennial plants coverage, showing that the correlationship between living biomass coverage and annual plants coverage was lower and weak, while that between living biomass coverage and perennial plants coverage was higher and significant, the source and constituents of the resistance could be understood and it could be concluded that living biomass was mainly consisted of perennial plants under this extremely aridity event. Therefore, it could be concluded that the resistance was mainly from perennial plants. Through the quantitative definition of vegetation stability with resistance, it could be concluded that, loss of biodiversity, especially loss of perennial plants, was the main mechanism and fundamental reasons for decreased community stability in desertification. The results could be explained from a reverse aspect as that biodiversity promoted the 6 desertified communities′ resistance stability under the short period of aridity disturbance, and also could be seen as an answer to the ecological questions such as “biodiversity′s function in ecological system” and “biodiversity and stability”.

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张继义*,赵哈林.短期极端干旱事件干扰下退化沙质草地群落抵抗力稳定性的测度与比较.生态学报,2010,30(20):5456~5465

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