Mechanisms and feedback consequences of shrub expansion following long-term increases in winter snow depth in northern Alaska: a legacy for IPY

为详细的、机械的调查提供了资金，研究灌木是如何在积雪深度增加的情况下成为主导的——这一过程已在阿拉斯加观察到。本研究将定量记录灌木的增加如何改变了阿拉斯加北极地区的非生物环境，并导致了这些系统功能属性的根本变化。该项目的具体目标是：1。定量记录灌木的增加如何影响北极苔原一年的温度和水分状况，以及灌木的增加如何改变系统的能量平衡；2. 描述了控制灌木生长的过程，特别是土壤和植物氮循环以及深雪对灌木分生组织和树枝的物理保护；和3。定量描述灌木密度的增加如何影响地上和地下碳[C]循环[C的获得、损失和分配]、水源和生长的模式和大小。在阿拉斯加北极部分地区观测到的灌木扩张可能会产生重大后果，包括反照率-气候反馈的变化、动物丰度的改变以及碳和氮循环过程的变化。由于阿拉斯加正在快速变暖，如果要做出明智的土地使用决定，如果要开发准确的预测模型，就需要对生物反应有一个机制上的了解。

Welker - 0612534Funds are provided for a detailed, mechanistic investigation of how shrubs become dominant in response to snow depth increases - a process that has been observed to occur in Alaska. This study will quantitatively document how increases in shrubs have altered the abiotic environment and caused a fundamental change in the functional attributes of these systems in arctic Alaska. The specific goals of this project are to: 1. quantitatively document how shrub increases affect the year-long temperature and water regimes of arctic tundra and how shrub increases change the energy balance of the system; 2. delineate the processes controlling shrub increases, especially soil and plant nitrogen cycling and the physical protection of shrub meristems and branches by deeper snow; and 3. quantitively describe how shrub density increases have affected the patterns and magnitudes of carbon [C] cycling [C gain, C loss and C allocation], water sources and growth, both aboveground and belowground.Observed shrub expansion within portions of arctic Alaska may have significant consequences, including shifts in the albedo-climate feedback, altered animal abundances, and changes in carbon and nitrogen cycling processes. As warming is progressing at a rapid rate in Alaska, a mechanistic understanding of the biotic response is needed, if informed land use decisions are to be made and if accurate forecasting models are to be developed.