塔里木荒漠河岸林植物多样性格局、动态与维持机制

Desert riparian forest is a special ecosystem in arid Region in Northwest China. It has an important role in maintaining ecological balance of Tarim desert area and protect the sustainable development of the oasis, moreover, can provide various natural resources for human and protect biodiversity. Desert riparian forest in Tarim River as the research object, and the sample strips and permanent large-scale plots were be established with field investigation, long-term monitoring, mathematical model analysis and soil chemical analysis to understand the underlying mechanisms of species coexistence. The pattern dynamics of structure and species composition, species distribution, interspecific association,niche characteristics and α, β diversity of desert riparian forest along environment gradient, and spatial associations among different age classes and species, spatial distribution of adult individual,dead individual and seedling of desert plant across scales , and the dynamics relationship between spatial pattern of plant diversity and sample size,different age,different habitats were studied. Furthermore, the spatial variation of species diversity(species richness and abundance) across spatial scales and fitted different models to species-abundance distribution in desert riparian forest were analyzed. The relationship between spatial pattern of plant diversity and its environment,space,biotic factors, and the formation mechanism of plant diversity gradient pattern and relative contribution of niche differentiation, neutral theory for species coexistence were interpreted.According to the analyses above, this research is to elucidate the limiting factors of desert plant community stability and species coexistence, Ultimately, to reveal the forming mechanism and ecological process of species abundance distribution and spatial distribution pattern of plant diversity, and the maintainence mechanisms of species diversity of desert riparian forest in Tarim River.This research will provide the theoretical basis to help planning for biodiversity protection and degraded ecosystem restoration,reconstruction of desert ecosystem.

荒漠河岸林是维护塔里木荒漠区生态平衡、保护生物多样性和保障绿洲可持续发展的生态屏障。项目以塔里木荒漠河岸林为研究对象，采用固定大样地监测与野外群落调查（样带法）、室内化验及生态数学分析，研究植物群落结构组成、植物多样性（α、β）、空间分布、种间联结性与生态位沿环境梯度的动态格局；成年个体与幼苗空间格局及与异、同种各龄级间的空间关联；植物多样性空间格局随取样尺度与龄级、生境变化的动态格局；物种多度、丰富度格局随尺度动态及其分布模型拟合，解译植物多样性格局与环境、空间、生物因子之间关系及其尺度效应，探讨植物多样性梯度格局的形成机制与中性理论、生态位分化理论对群落构建的贡献，阐明制约荒漠河岸林植物群落稳定和物种共存的限制因素，揭示荒漠河岸林植物多样性空间格局、多度格局形成机理和生态学过程及植物多样性的维持机制，为塔里木荒漠河岸林生物多样性保护与退化生态系统恢复重建提供理论依据。

受全球气候变暖与区域水土资源开发利用的影响，塔里木荒漠河岸林生态系统退化、植物多样性受损，生态服务功能降低。主要研究荒漠河岸林群落植物多样性(α、β)、种间联结性、生态位沿环境梯度及植物多样性空间格局随取样尺度与龄级、生境变化的动态格局，探讨植物多样性梯度格局的形成机制与中性理论、生态位理论对群落构建的贡献作用，揭示荒漠河岸林群落形成和植物多样性维持机制。塔里木荒漠河岸林共有15科32属34种植物，乔灌少、群落分层明显，群落最小抽样面积400m2，重要值作指标表征群落多样性最优。α多样性随地下水位下降而降低，β多样性则增大。群落大多种对间呈负联结，生态位重叠大且竞争激烈。优势种空间格局、多样性与物种多度格局随发育进程与尺度增大由聚集趋向随机分布，种间多呈空间负关联。随地下水位下降土壤沙化、养分含量降低，乔灌与草本多度、丰富度主要分别受深层、浅层土壤水分的决定。群落物种多样性开始受损的地下水位为4.0m；优势种半致死地下水位(GWD50)为5.5m，水位阈值在7—8m。地下水位是限制群落多样性分布的主要因素，其次为土壤养分。环境因素在群落构建与物种共存中的作用大于生物因素。环境筛选是影响荒漠河岸林群落形成与限制物种共存的关键作用力，种间竞争起次要作用。生态位理论可较好解释荒漠河岸林群落形成和物种多样性的维持机制。维持塔里木荒漠河岸林物种多样性和群落稳定的合理生态地下水位为4.0m。研究结果为塔里木荒漠河岸林生物多样性保护、退化生态系统恢复重建及生态输水工程提供科学依据。