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

Niwot Ridge LTER采用长期和短期操纵性实验和长期监测计划，研究生物和生态系统对气候和大气输入年际变化的反应和反馈。45年的气候记录表明，尼沃特岭的高山苔原正在经历降雨量的增加；从20世纪80年代初开始对大气氮输入的类似测量表明，大气氮沉降增加。风对积雪的重新分布在高山冻土带和亚高山森林和草甸上放大和减弱了这些输入。提出了描述性和操纵性研究，旨在了解这些现象在生态系统结构、功能和通量方面的后果。同时，还提出了树线对氮素再分配和生态系统响应的影响问题，以及树线控制假说的检验。要解释生物对不断变化的输入的反应，需要一个层次化的观点，明确承认生物群的进化历史、古生态记录和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，而且还产生了关于生态交错带的生物和生物地球化学意义的单独一行问题。在树线上，植被结构似乎控制着积雪，而不是相反，因此，积雪增加和伴随的氮沉降的后果受到生物和地形的控制。本质上，中尺度积雪模型被一个更高阶的约束所覆盖，即树线上的控件。这项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。尼沃特岭是非洲大陆上唯一一个多学科的长期高山和亚高山研究地点。因此，该站点是衡量生态现象和对人类引起的气候和大气化学变化的生物反应的地方、区域和国家网络的重要基准。因此，重点放在为当前和未来的科学家记录研究和归档数据上。这项研究是1981年开始的研究的继续，并基于开始于20世纪50年代的研究和数据库。对这一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.