藏北高寒沼泽湿地冻胀草丘微生境对植物群落特征的影响

Frozen grassy hillock is an important microtopography characteristic of alpine marsh wetlands in Qinghai-Tibet Plateau, and special hillock microtopography could bring the heterogeneous microhabitat. As one of the basic components of wetland ecosystems, plant community structures are the aggregation of responses to many habitat factors. So microhabitat heterogeneity would inevitably lead to the changes of plant community structures and ecosystem succession. However, it was deficient to study the response mechanism of plant community to special microhabitat in alpine region up to now..The proposed research is to be conducted in a typical alpine marsh wetland, which located at the permafrost region of the Northern Tibetan Plateau, and frozen grassy hillock spreads all over of this marsh area. Three main themes in the research would be designed to: a) investigate spatial heterogeneity of main microhabitat factors in the hillock region, while water level, soil nutrients, morphology of hillock as main factors; b) analyze the changes of structure indices (diversity and biomass) of plant community in microhabitat scale and niche characteristics of dominant species in factors gradients; c) explore the response mechanism and adaption modes of plant community to hillock microhabitat in alpine marsh wetlands. Furthermore, the proposed research will provide significant approaches and monitoring details to the ecological rule of alpine plant communities in microhabitat scale, and benefit the stability of alpine marsh ecosystems.

冻胀草丘是青藏高原高寒沼泽湿地重要的微地貌特征，微地貌的改变是产生异质性生境的重要因素。湿地植物群落作为植物对环境梯度响应的集合体，微生境异质性导致了植物群落结构的变化和演替，但目前相关高寒沼泽湿地植物群落对特殊微生境响应和适应的研究极为缺乏。本项目以藏北高原申扎地区多年冻土区丘沼相间的湖滨湿地为研究区域，研究微生境尺度下植物群落结构的空间分布特征，分析冻胀草丘形态特征、冻土活动层水热条件、土壤养分等微生境因子的空间异质性，阐明植物群落结构指标与微生境因子的关系，揭示高寒沼泽植被群落结构对草丘斑块状微生境的响应规律；分析优势植物种群在微生境因子梯度上的生态位特征，探讨冻胀草丘微生境对于植物群落结构的影响机制和优势植物种群的适应模式。本项研究对于探索特殊微地貌下高寒湿地植物群落的生态规律和保护高寒湿地生态系统的稳定结构提供研究实例和数据依据，具有重要生态学价值。

冻胀草丘是青藏高原高寒沼泽湿地重要的微地貌特征，微地貌的改变是产生异质性生境的重要因素。目前相关高寒沼泽湿地植物群落对特殊微生境响应和适应的研究极为缺乏。本项目以藏北高原申扎地区多年冻土区丘沼相间的湖滨湿地为研究区，研究微生境尺度下高寒嵩草植物群落结构与冻胀草丘的关系。结果表明：冻胀草丘的存在增强了微生境的空间异质性，提高了土壤温度波动性，降低了土壤湿度，改变了植物的生存环境；导致了嵩草类优势种的改变和嵩草群落的演替显著，提高了丘体植物群落的多样性及生物量；并显著增加了区域土壤有机质含量和碳密度。本项目又进一步探讨了藏北嵩草和矮生嵩草种群在丘体和丘间微生境因子梯度上的生态位特征和种间关系，讨论了土壤湿度和有机质等关键生境因子与优势种群矮生嵩草和藏北嵩草密度变化趋势的相关性的同时，发现土壤水分的空间异质性决定了藏北嵩草密度的空间异质性，而两种嵩草密度的空间异质性决定土壤有机质的空间异质性。同时，两种嵩草的集群分布使得其密度与土壤湿度、有机质空间异质性之间的关系增强，这从一定程度上说明了藏北嵩草和矮生嵩草之间的竞争替代关系。藏北草丘类微地貌的改变是区域嵩草群落演替的基础，这种空间异质性的存在对植物群落的更新和稳定以及区域碳源汇功能均有重要影响。