【作者】 容丽；

【导师】 王世杰；

【作者基本信息】 中国科学院研究生院（地球化学研究所） ， 地球化学， 2006， 博士

【摘要】 喀斯特石漠化是在90年代末期才受到普遍重视。它代表了独特的湿润区石质荒漠化生态系统。荒漠化是生态系统退化的过程和结果，破坏了系统结构，导致生态机能障碍。本论文试图通过植物群落和个体对环境梯度的反应，结合稳定同位素技术和植物生理生态学方法，针对喀斯特地区植物生长的限制因子——水分因子，认识石漠化过程对植物结构功能造成的改变，及植物在干旱环境中维持水分平衡的能力，探讨在喀斯特石漠化生境中植物对水分的竞争和利用策略。 通过对花江喀斯特低热河谷小流域典型石漠化样区的环境、植物指标分析，得出以下认识： 1 石漠化等级对环境背景的影响 （1）小气候梯度响应研究数据表明，石漠化一旦发生，植被覆盖率的下降，植被的生态调节作用也会严重退化，依次顺序为：潜在石漠化（L）＞轻度石漠化（SL）＞中度石漠化（M）＞强度石漠化（ST）。 （2）在群落组成结构上，群落各层片内层次差异不显著，不同石漠化等级间群落盖度存在差异。无论是否发生石漠化，优势种都不明显。同一等级中相似性系数均值最高的是潜在石漠化，从潜在至强度石漠化间呈现轻微下降趋势，但差异不显著。群落所有物种共有度的几个谷值分别出现于L-SL、L-M之间。各石漠化等级间生物量及生物量年增长量总体上均具显著差异。各等级生物量变异系数为L＞M＞ST＞SL，表明潜在石漠化植物群落稳定性最高，轻度最低。不同等级石漠化群落间多样性指数、均匀度指数、优势度和丰富度指数总体差异显著。多种多样性指数均表明随石漠化等级的加重有下降的趋势，丰富度指数表现为L＞SL＞ST＝M；均匀度指数表明，轻度石漠化均匀度程度最低，群落稳定性低。从L—SL—M间βw多样性增加，且变化幅度很大，表明相邻群落类型间物种组成差异明显。 2 石漠化地区乔灌植物的水分来源 （1）干季末期（4月）的δD／δ¹⁸O值明显低于降水集中的季节（7／8月），各因素对氢氧同位素的影响表现为石漠等级差异＞石漠等级与季节交互效应＞季节效应。雨季植物叶片黎明前水势与植物木质部水分的δD值成负相关关系。利用表土夏季降水的植物水势低于利用土壤下层水的植物。 （2）在干旱的4月，喀斯特皮下水成为强度石漠化样地植物水分的主要贡献者，野桐利用了高达76％皮下水，而清香木也利用了53％的皮下水；在雨季的7、8月，土壤下层水分成为植物水分的主要贡献者，尤其是常绿种土壤下层水均达更多还原

【Abstract】 The problem of karst rocky desertification was attached importance in 1990’s, which represents a unique rocky desertification ecosystem in humid area. Desertification often results in a dysfunctional system in which the mean residence time is reduced for resources entering the ecosystem or being produced by it. The degraded process of the vegetation structure and functions changed by the rocky desertification were in relation with water, the key limiting factor. The plant water use strategies were examined by stable isotope and plant ecophysiology techniques. Along a water gradient, the competitive and adaptive strategies of plant were discussed.By the analysis of the characters of plants and environment of a small drainage basin in the hot valley of Huajiang area, we get the conclusions as bellow:1. Implication of karst rocky desertification on the environmental background(1) On the basis of measurement for microclimatic parameters, once the desertification occurring, followed the order of strong (ST)> medium (M) > slight (SL) > latent (L), owing to the decrease of the coverage and degeneration of adjustment of vegetation.(2) The layers of the synusia were no significantly different in the community. The coverage of the vegetation is different in the degree of desertification. There were no dominant species in all the community. Co-occurrence of plant species among communities at different grade desertification was analyzed, for species of trees or all the species as a whole, co-occurrence of plant species between the plots of latent desertification was the highest. The valley values of co-occurrence of plant species among communities along environment gradient were between the L-SL and SL-M, the results showed that turning point of plant species compositions at the types. The above ground biomass and the gross per annum were significantly different. The coefficient of variability of biomass in different degrees followed the order of L>M>ST>SL, showed the highest stable community was the latent one contrast with the unstable slight plots. Species abundance, species richness, total diversity and species evenness were significantly different. In general, most of the diversity index showed a decrease trend. The abundance takes the order of L>SL >ST=M. The lowest equitability (species evenness) occurred in the slight community, which can describe the low community stability. The β _W diversity in plant communities along the更多还原