Climate warming and permafrost thaw induced land cover change are well documented in much of the circumpolar north. The extensive exposure of Precambrian continental crust in Canada's Taiga Shield ecoregion could mean impacts of land cover change documented in other regions without this feature are not transferable. This study examined energy partitioning with eddy covariance measurements, vegetation water use with stable isotopes and soil water state with time domain reflectometry sensors in conifer stands in the Taiga Shield ecoregion. The goal was to determine how changes in forest density with climate warming could influence water budget response and soil water state. Paired measurements of sensible and latent heat imply evaporative processes in denser canopies are controlled more by radiative than the aerodynamic factors predominant in sparser canopies. As denser canopies become more prevalent on the landscape, this switch in relative importance of evapotranspirative processes will lead to a reduction in inter-annual variability of evapotranspiration. The dominant tree species (black spruce, tamarack and jack pine) were all quick to draw water from shallow soils after spring thaw and rainfall. Stand structural changes resulted in older, more evaporatively enriched water prevalent in soils below dense canopies. While there is evidence for forest infilling, widespread lakes and exposed bedrock restricts extensive expansion of forested land covers. The insufficient difference between sparse and dense canopy evapotranspiration suggest a fundamental change in how water cycles in Taiga Shield catchments is unlikely, which is notably different than previously investigated landscapes in Alaska and the Canadian Taiga Plains.

中文翻译：

---

针叶林盾构生态区稀疏针叶林植树填充对能量分配、植被水分利用和土壤水分状态的影响


气候变暖和永久冻土融化引起的土地覆盖变化在环极地北部的大部分地区都有详细记录。加拿大针叶林地盾生态区前寒武纪大陆地壳的广泛暴露可能意味着在没有这一特征的其他地区记录的土地覆盖变化的影响是不可转移的。这项研究通过涡流协方差测量进行了能量分配，通过稳定同位素对植被用水进行了研究，并通过时域反射计传感器对针叶林针叶林中的土壤水状态进行了研究。目标是确定森林密度随气候变暖的变化如何影响水预算响应和土壤水状态。显热和潜热的配对测量表明，较稀疏的冠层中的蒸发过程更多地受到辐射的控制，而空气动力学因素则更多地受到辐射的控制。随着更密集的树冠在景观中变得更加普遍，蒸散过程相对重要性的这种转变将导致蒸散量的年际变化减少。春季解冻和降雨后，主要树种（黑云杉、落叶松和短叶松）都能迅速从浅层土壤中吸取水分。林分结构的变化导致浓密树冠下土壤中普遍存在较古老、蒸发更丰富的水。虽然有证据表明森林正在被填充，但广泛的湖泊和裸露的基岩限制了森林土地覆盖的广泛扩张。稀疏和密集树冠蒸散量之间的差异不足表明，针叶林地盾集水区的水循环方式不太可能发生根本性的变化，这与之前研究的阿拉斯加和加拿大针叶林平原的景观明显不同。