The Role of Natural Legacy on Ecosystem Structure and Function in a Polar Desert: The McMurdo Dry Valley LTER Program

里昂麦克默多干谷（MCM）地区是世界上最极端的沙漠之一；比任何其他长期生态研究（LTER）地点都要冷得多，也干燥得多。MCM内的生物系统相对简单，没有维管植物和脊椎动物。在LTER项目的头六年里，为了评估生态系统结构和功能的物理限制因素，对常年被冰覆盖的湖泊、短暂的溪流和大面积的土壤进行了调查。很明显，在这一环境的陆地和水生部分，液态水的产生是生态系统动力学的主要驱动力。因此，当今气候变化的作用是极其重要的。然而，最重要的发现之一是，过去的气候遗产在MCM中强烈地叠加了当前的生态条件。在LTER的第二阶段，研究将通过MCM作为“末端成员”系统的继续调查来扩展，目的是更好地确定过去气候遗产对生态系统结构和功能的作用。概念模型现在包括遗产作为MCM的一个重要规则。在三个主要重点领域：水文学、生物活性和多样性以及生物地球化学过程的一系列八个假设将通过持续的监测计划和长期实验进行测试。了解MCM生态系统的结构和功能需要了解现在和过去对气候的水文响应。当前的生物活动和多样性模式反映了过去和现在的水、营养物质、有机碳和生物群的分布。负责营养物质和其他化学物质的运输、固定和矿化的生物地球化学过程提供了MCM生物群与物理环境之间的联系。过去和现在的生物地球化学过程的时间、持续时间和位置受水的可用性控制。将继续努力集中于整合构成海洋生态系统景观的湖泊、河流和陆地生态系统内部和之间的生物过程。跨学科研究小组计划继续使用建模和其他综合研究来综合数据，并检查MCM生态系统的知识。

9810219LYONSThe McMurdo Dry Valleys (MCM) region is among the most extreme deserts in the world; far colder and drier than any other Long Term Ecological Research (LTER) site. The biological systems within the MCM are relatively simple with no vascular plants and vertebrates. During the first six years of this LTER project, the perennially ice-covered lakes, ephemeral streams and extensive areas of soils were investigated in order to assess the role of physical constraints on the structure and function of the ecosystem. It is clear that the production of liquid water in both terrestrial and aquatic portions of this environment is a primary driver in ecosystem dynamics. Thus, the role of present day climatic variation is extremely important. However, one of the most significant discoveries was that past climatic legacies strongly overprint the present ecological conditions in MCM. In the second phase of this LTER, the research will be extended through the continuation of the investigation of the MCM as an "end-member" system, with the aim to better ascertain the role of the past climatic legacies on ecosystem structure and function. The conceptual model now includes legacy as an important regular of MCM. A series of eight hypotheses in three major focus areas: hydrology, biological activity and diversity, and biogeochemical processes will be tested through a continuation of monitoring programs and long-term experiments. Understanding the structure and function of the MCM ecosystem requires understanding hydrological response to climate both now and in the past. Current patterns of biological activity and diversity reflect both past and present distributions of water, nutrients, organic carbon and biota. Biogeochemical processes responsible for the transport, immobilization, and mineralization of nutrients and other chemicals provide the linkages between the MCM biota and the physical environment. The timing, duration and location of biogeochemical processes in the past and present are controlled by water availability. Efforts will continue to focus on the integration of the biological processes within and among the lakes, streams and terrestrial ecosystems comprising the MCM landscape. The interdisciplinary research team plans to continue to use modeling and other integrative studies to synthesize data and to examine the knowledge of the MCM ecosystem.