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 seastedt Niwot Ridge LTER采用长期和短期操作实验和长期监测方案，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，尼沃特岭的高山冻土带降水正在增加；1980年代初开始的对大气氮输入的类似测量表明，大气氮沉积增加。在高寒苔原和亚高寒森林和草甸上，风对积雪的重新分配放大和减弱了这些输入。提出了描述性和操纵性研究，旨在从生态系统结构、功能和通量的角度理解这些现象的后果。同时提出了林木线对氮素再分配和生态系统响应的影响，以及对林木线控制的假设检验等问题。解释生物对变化输入的反应需要一个层次的观点，明确承认生物群的进化史、古生态记录和生态系统组成部分之间的当前相互作用。亚高山的纳入不仅提供了新的生态系统比较，而且还产生了关于过渡带的生物和生物地球化学意义的单独问题。在林木线上，植被结构似乎控制积雪量，而不是相反，因此积雪量增加和伴随的氮沉积的后果受到生物和地形的控制。从本质上讲，中尺度积雪模型被一个更高阶的约束所覆盖，即对树线的控制。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。尼沃特岭是该大陆唯一的多学科、长期的高山和亚高山研究地点。因此，该站点是地方、区域和国家网络的重要基准，用于测量生态现象和人类引起的气候和大气化学变化的生物反应。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1950年代开始的研究和数据库为基础。这项长期研究计划的持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要研究成果的基础上进一步发展。

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.