Effects of changing precipitation regimes on high Arctic, tundra, ecosystems in a warming climate

由于气候变暖、海冰减少、永久冻土融化和工业发展的加剧，北极正在发生巨大变化。在过去的40年里，年气温上升了1-4ºC，总降水量增加了40%。冻土带生态系统现在正在显示出过去在变暖实验中看到的变化，例如植物生长和繁殖的增加、生物多样性的变化、系统内外二氧化碳流量的增加、土壤过程和养分有效性的增加。植物高度和覆盖面积的增加，尤其是灌木，已经被测量出来，这将影响野生动物，并可能导致更大的变暖。我们对冻土带生态系统如何对变暖做出反应有了很好的了解；然而，对气候变化的反应将取决于湿度条件以及雪或雨的增加或减少。我们知道，在其他生态系统中，湿度条件的变化比温度的变化更重要。气候变暖和海冰的减少会导致更多的降水，这可能会增加土壤水分。然而，气候变暖也会加深永久冻土层之上的融化层，增加植物和土壤的蒸发。这可能导致土壤干燥，尽管降水增加。如果我们要了解和预测冻土带系统的变化，我们就需要知道它们如何对湿度条件的变化作出反应，这是我提出的研究重点。研究将在北极高极地沙漠进行。预计这些广阔的光秃秃的地区将变得更加茂盛。我们将在极地沙漠地区建立增加雪深（雪栅栏）、土壤湿度（浇水）和温度（敞篷温室）的实验。我们还将研究沙漠中晚卧的雪床的作用，它在整个夏天提供水分。最后，我们将根据矮灌木物种的年生长模式重建过去一个世纪加拿大高北极地区的温度和降水变化。每项研究都将有一名博士生参与，这将大大提高我们预测北极高纬度苔原生态系统变化的能力。

The Arctic is changing dramatically because of the warming climate, loss of sea ice, melting permafrost and increasing industrial development. Annual temperatures have increased by 1-4ºC and total precipitation has increased by up to 40% in the past 40 years. Tundra ecosystems are showing changes now that were seen in warming experiments in the past, such as increased growth and reproduction of plants, shifts in biodiversity, greater flows of CO2 in and out of the systems, and increased rates of soil processes and nutrient availability. Increases in plant height and cover, especially shrubs, have been measured which will impact wildlife and could lead to more warming. We have a good understanding of how tundra ecosystems respond to warming; however, the responses to the changing climate will depend on moisture conditions and whether there will be an increase or decrease in snow or rain. We know change in moisture conditions in other ecosystems is more important than change in temperature. The warming climate and loss of sea ice should result in more precipitation, and this may increase soil moisture. However, the warming will also deepen the melted layer above the permafrost and increase evaporation from the plants and soil. This could cause drier soils, despite increases in precipitation. If we are to understand and predict the changes in tundra systems we will need to know how they respond to changes in moisture conditions, and this is the focus of my proposed research. Studies will be conducted on high Arctic polar deserts. These extensive bare areas are predicted to become more vegetated. We will establish experiments in polar desert sites to increase snow depth (snow fences), soil moisture (watering) and temperature (open top greenhouses). We will also examine the role of late lying snow beds in the deserts, which supply moisture through the summer. Finally, we will reconstruct the changes in temperature and precipitation in the Canadian High Arctic over the past century from patterns in annual growth in dwarf shrubs species. Each of the studies will involve a PhD student and will significantly increase our ability to predict changes in high Arctic tundra ecosystems.