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

WELKER-0612534Funds用于详细、机械地调查灌木是如何随着积雪深度的增加而成为主导的--这一过程已被观察到发生在阿拉斯加。这项研究将定量记录灌木的增加如何改变了非生物环境，并导致北极阿拉斯加这些系统的功能属性发生了根本性的变化。这个项目的具体目标是：1.定量记录灌木增加如何影响北极冻土带一年的温度和水分状况，以及灌木增加如何改变系统的能量平衡；2.描述控制灌木增加的过程，特别是土壤和植物的氮循环，以及更深的雪对灌木分生组织和枝条的物理保护；3.定量描述灌木密度增加如何影响地上和地下的碳[C]循环[C得、C失和C分配]、水源和生长的模式和程度。观察到的灌木在阿拉斯加部分地区的扩展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。由于阿拉斯加气候变暖的速度很快，如果要做出明智的土地利用决策和开发准确的预测模型，就需要从机制上理解生物反应。

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.