LTER: The Niwot Ridge LTER Research Program 1998-2004: Controls on the Structure, Function & Interactions of Alpine & Subalpine Ecosystems of the Colorado Front Range

9810218 SeastedtThe尼沃特岭LTER采用了一个长期和短期的操纵实验和长期监测方案，以研究生物和生态系统对气候和大气输入年际变化的响应和反馈。45年的气候记录表明，尼沃特岭的高山苔原正在经历降水量的增加; 20世纪80年代初开始的对大气氮输入的类似测量表明大气氮沉降增加。风对积雪的再分布放大和衰减了高山冻原、亚高山森林和草甸的这些输入。描述性和操纵性的研究，旨在了解这些现象的后果，生态系统的结构，功能和通量的建议。同时，还提出了树线对氮素再分配和生态系统响应的影响以及树线控制假说的检验问题。生物对变化的输入的反应的解释需要一个层次的观点，明确承认生物群的进化历史，古生态记录，以及当前生态系统组成部分之间的相互作用。包括亚高山不仅提供了新的生态系统比较，但也产生了一个单独的问题，关于生态交错带的生物和地球化学意义。在树线，植被结构似乎控制积雪，而不是反之亦然，因此，增强积雪和伴随的N沉积的后果是根据生物以及地形控制。在本质上，中尺度积雪模式是由一个高阶约束，控制树线。拟议的研究概述了一系列描述性和操纵性研究，以确定这些控制。尼沃特海岭是该大陆唯一的多学科、长期高山和亚高山研究地点。因此，该网站是衡量生态现象和生物对人类引起的气候和大气化学变化的反应的地方，区域和国家网络的基本基准。因此，重点放在为当前和未来的科学家记录研究和存档数据上。这项研究是1981年开始的研究的延续，并以20世纪50年代开始的研究和数据库为基础。对这一长期研究计划的继续支持将使这些研究人员能够在尼沃特岭高山生态系统的重大研究成果的基础上再接再厉。

9810218SeastedtThe Niwot Ridge LTER employs a program of long- and short-term manipulative experiments and long-term monitoring to study biotic and ecosystem responses and feedbacks to interannual variation in climatic and atmospheric inputs. The 45-yr climate record shows that the alpine tundra at Niwot Ridge is experiencing increased amounts of precipitation; similar measurements of atmospheric nitrogen inputs begun in the early 1980's demonstrate increased atmospheric nitrogen deposition. Redistribution of snowpack by wind amplifies and attenuates these inputs across the alpine tundra and subalpine forest and meadows. Descriptive and manipulative studies designed to understand the consequences of these phenomena in terms of ecosystem structure, function and fluxes are proposed. Concurrently, questions on influence of treeline on nitrogen redistribution and ecosystem response, and test of hypotheses on controls of treeline are also presented. Interpretation of biotic responses to changing inputs requires a hierarchical perspective that explicitly acknowledges the evolutionary history of the biota, the paleoecological record, and the current interactions among ecosystem components. The inclusion of the subalpine provides not only new ecosystem comparisons, but also generates a separate line of questions regarding the biotic and biogeochemical significance of ecotones. At treeline, vegetation structure appears to control snowpack rather than vice-versa, and therefore the consequences of enhanced snowpack and accompanying N deposition are under biotic as well topographic controls. In essence, the mesoscale snowpack model is overridden by a higher order constraint, the controls on treeline. The proposed research outlines a series of descriptive and manipulative studies to identify these controls. Niwot Ridge is the only multidisciplinary, long-term alpine and subalpine study site on the continent. As such, the site is an essential benchmark for local, regional and national networks that measure ecological phenomena and biological response to human-induced changes in climate and atmospheric chemistry. Accordingly, emphasis is placed on documenting research and archiving data for current and future scientists. This research is a continuation of studies initiated in 1981, and is based upon research and databases begun in the 1950s. Continued support of this long-term research program will allow these investigators to build upon the significant research accomplishments in alpine ecosystems at Niwot Ridge.