Data logger systems for a field warming experiment

据预测，由温室气体增加引起的气候变化首先在高纬度地区发生，而且发生得最快。在北方森林中，树木生长的记录已经显示出最近气候变暖的迹象。与此同时，每年被烧毁的北方森林数量呈上升趋势，特别是在加拿大西部，那里夏季干燥天气的持续时间有所增加。这些被烧毁的森林将需要在气候条件下进行再生，气候条件可能与以前的森林再生周期非常不同。持续的气候变暖将如何影响这些森林在火灾后重建的能力，特别是在成熟树木已经显示出干旱压力增加迹象的干旱地区？本研究旨在探讨气候变化的一个方面，即土壤温度升高如何影响育空地区南部干燥北方森林地区的森林再生模式。将建立一个土壤升温实验，利用太阳能热水循环在夏季将表层土壤加热2-4°C。这个实验将在1998年烧毁的大片白云杉林的土壤湿度梯度上进行。在大火中自然树苗建立的模式表明，在大火中最干燥的地点，白云杉的再生能力非常差，而在朝北的斜坡和山谷底部较冷和较湿润的地点，树苗数量丰富。白云杉和其他森林共优势植物的种植试验将应用于暖区和对照区，以测试土壤升温和干燥是否可能成为该地区火灾后森林再生的限制步骤。该实验将在干燥、潮湿和潮湿的地点重复进行，以确定地点水分有效性的差异是否会影响森林更新对土壤变暖的响应。实验结果将表明，北方森林干旱地区的变暖如何改变火灾后森林更新的模式。

Climate change caused by increases in greenhouse gasses has been predicted to occur first and fastest at high latitudes. In the boreal forest, records of tree growth are already showing signs of recent climate warming. At the same time, there is an upward trend in the amount of boreal forest that burns each year, especially in western Canada, where there have been increases in the duration of dry summer weather. These burned forests will need to regenerate under climate conditions likely to be very different from what they experienced in previous cycles of forest regeneration. How will ongoing climate warming affect the ability of these forests to re-establish after fire, particularly in drier areas where mature trees are already showing signs of increased drought stress?     This research proposes to investigate how one aspect of a changing climate, increased soil temperature, may affect patterns of forest regeneration in an area of dry boreal forest in southern Yukon Territory. A soil warming experiment will be established that uses circulation of solar-heated water to warm surface soil during the summer by 2-4 °C. This experiment will be set up across a soil moisture gradient within a large area of white spruce forest that burned in 1998. Patterns of natural seedling establishment in the burn indicate that white spruce has regenerated very poorly at the driest sites in the burn, while seedlings are abundant in cooler and moister sites on north-facing slopes and valley bottoms. Planting trials of white spruce and other forest co-dominants will be applied to warmed and control plots to test whether soil warming and drying is likely to be a limiting step in forest regeneration after fire in this area. The experiment will be duplicated across dry, moist, and wet sites to determine if there differences in site moisture availability affect the response of forest regeneration to soil warming. Results of the experiment will indicate how increased warming in dry regions of boreal forest may alter patterns of forest renewal after fire.