The Arctic LTER Project: Terrestrial and Freshwater Researchon Ecological Controls

在阿拉斯加图利克湖北极LTER的头五年期间，开始了对气候、冻原植物分布和生产力以及湖泊和河流物理、化学和生物学的系统测量。在冻土带、溪流和湖泊上建立了整个系统实验，以考察环境和生物因素的变化对生态的影响，如气温、添加的营养物质以及顶级捕食者和食草动物密度的变化。这些测量和长期实验旨在帮助实现总体目标：了解冻土带、溪流和湖泊在北极的功能，并预测它们如何应对包括气候变化在内的人类引起的变化。在这一大目标下，有三个具体目标：(1)确定这些系统每年的生态可变性，并衡量长期变化。(2)了解资源(自下而上的控制)或放牧和捕食(自上而下的控制)的控制程度。(3)测量速率，了解土壤和水之间养分和有机质交换的控制。长期实验是北极LTER计划的核心。人们发现，北极系统往往多年没有反应，而长期反应往往不能从短期反应中预测出来。9年后，溪流和陆地植被对营养改良剂的反应仍在记录中。湖中的鲑鱼操作需要很多年才能显示出效果，因为当这些长寿的鱼达到一定大小时，它们的饮食可能会从无脊椎动物改变为鱼类。因此，确定生态可变性的大多数长期实验和测量将继续进行。随着更多关于资源和捕食对生态系统的长期控制的发现，长期实验的结果将继续得到衡量。将开始对陆地和水之间营养物质交换的控制进行新的研究。将进行一项重要的分水岭实验，以测量水和溶解气体通过地下水进入溪流的移动情况。

During the first five years of the Arctic LTER at Toolik Lake, Alaska, systematic measurements of climate, of tundra plant distribution and productivity, and of lake and stream physics, chemistry and biology were begun. Whole system experiments were set up on the tundra, in streams, and in lakes to examine the ecological effects of changes in environmental and biological factors such as air temperature, added nutrients, and changes in the density of the top predators and grazers. These measurements and long-term experiments are designed to help reach the overall goal: to understand how tundra, streams and lakes function in the Arctic and to predict how they respond to human-induced changes including climate change. Under this broad goal there are three specific goals: (1) Determine year-to-year ecological variability in these systems and measure long-term changes. (2) Understand the extent of control by resources (bottom-up control) or by grazing and predation (top-down control). (3) Measure rates and understand the controls of the exchange of nutrients and organic matter between land and water. Long-term experiments are the heart of the Arctic LTER program. It has been found that arctic systems often do not respond for many years, and that long-term responses are often not predictable from short-term responses. Changes in the responses of both streams and terrestrial vegetation to nutrient amendments are still being documented after 9 years. Lake trout manipulations take many years to show effects as these long-lived fish may change their diet from invertebrates to fish when they reach a certain size. As a result, most long-term experiments and measurements for determining ecological variability will be continued. The results of the long-term experiments will continue to be measured as more is discovered about long-term ecosystem controls by resources and predation. New research on the controls of the exchange of nutrients between land and water will be started. A major watershed experiment will be carried out to measure the movements of water and dissolved gases through the groundwater and into the streams.