洪泛作用削弱下退化沼泽土壤动物格局与其分解功能演变及机制

Flooding is a decisive factor for the structure and process of marsh wetlands in floodplain. The periodical effects of the floods lead to the alternate drying-wetting habitats which adjust the soil fauna patterns. The floodplain marshes have significantly degraded to great extent due to the river floods gradually decreasing or absent by global change and human activity in recent years, i.e. separating by dams. Comparing to the many studies on the response of plants on flooding, few research was done on soil fauna distribution patterns and their decomposition function, and also the corresponding mechanisms. However, this is critically important for explaining the coupling relationship among water regime-habitat-biological pattern-ecological process. This program will select the Wusuli River-Bielahong River Basin in the Sanjiang Plain, Northeast China, as the filed research site. Through the methods of field investigation and space-time substitution, we will investigate the dynamics of soil fauna community composition and distribution pattern under situations of flooding decreasing. Using the methods of 13C and 15N stable isotope analysis, in situ control and laboratory simulation to elucidate the soil fauna effects and contributions to litter and soil organic matter decomposition. In addition, the coupling relationship will also be revealed between soil fauna structures and their decomposition function with flooding regimes, soils and plants characteristics. Basing on the above studies, we will construct an successive mechanism model including the typical pattern and core ecological processes.

洪泛作用是洪泛沼泽结构和过程的决定性驱动因子。洪水的周期性作用造就了洪泛沼泽干湿交替的生境，调控着土壤生物的格局。全球变化和人类活动影响下，河流洪泛作用不断削弱，或被堤坝所阻隔，洪泛沼泽退化严重。与沼泽植物对洪泛波动响应的深入研究相比，沼泽地下土壤动物格局及其功能的演变及机制研究才刚刚起步；而这是阐明洪泛沼泽"水-生境-生物格局-生态过程"耦合关系的关键之一。选择三江平原乌苏里江-别拉洪河流域作为研究区，运用野外调查和时空替代方法，明确洪泛作用削弱下沼泽土壤动物组成与时空分布动态；采用13C和15N示踪、原位控制和室内模拟等方法，阐明土壤动物对植物残体和土壤有机质分解的影响和贡献演变；揭示沼泽土壤动物格局与其分解功能与水文情势、土壤和植物特征的耦合关系，构建融合典型格局和核心生态过程的演变机制模型。项目将有助于深入对沼泽生物格局与生态过程的维持机制、土壤生物多样性与沼泽系统功能关系的认识。

针对全球变化和人类活动影响下，河流洪泛作用不断削弱，或被堤坝所阻隔，洪泛区沼泽退化严重，沼泽湿地结构发生明显变化。其中，随着沼泽湿地退化，陆生土壤动物大量入侵，与沼泽植物对洪泛波动响应的深入研究相比，沼泽地下土壤动物格局及其功能的演变及机制研究才刚刚起步。选择三江平原乌苏里江-别拉洪河流域作为研究区，主要开展了沼泽土壤动物群落结构和分布格局对洪泛作用削弱的响应；洪泛削弱下沼泽土壤动物对植物残体分解的影响及贡献变化；沼泽土壤动物格局与其分解功能对洪泛作用削弱的响应机制等三方面的研究。结果表明，蚯蚓、蚂蚁等大型土壤动物，跳虫等中小型土壤动物和水生螺类为代表类群，随着洪泛作用削弱下其组成与时空分布动态发生显著时空变化，深入揭示了不同淹水情势变化土壤动物群落组成差异，并筛选了指示性类群。表现为洪泛区沼泽湿地的水文连通性改变后，沼泽湿地土壤动物群落组成和优势物种发生显著变化；分布格局表现为随着淹水的减弱和湿地旱化，陆生土壤动物大量“入侵”且种类组成和密度增加；而河流源的水生无脊椎动物显著减少，或部分物种缺失。采用原位控制和室内模拟等方法，揭示了蚂蚁、蚯蚓等大型土壤动物土壤有机质分解和含碳温室气体排放的重要影响和贡献及其对干湿交替的响应；野外原位实验，研究揭示了不同淹水下有机质分解的动态及土壤动物对分解速率、营养元素含量及其比值的影响；以蚯蚓对温室气体排放的调控为代表，构建融合典型格局和核心生态过程的调控机制模型。项目研究成果加深了对沼泽生物格局与生态过程的维持机制、土壤生物多样性与沼泽系统功能关系的认识。