Root tissue chemistry, mycorrhizal colonization, and uptake of nitrogen-15 tracer in glycine, ammonium, and nitrate form across a tree density gradient in northeastern Siberia. 2017.

Greater tree density and forest productivity at the tundra-taiga ecotone (TTE) are expected with climate warming, with potential feedbacks to the climate system. Yet, competition for nitrogen (N) may impact TTE dynamics. Greater tree density will likely increase N demand, while reducing N supply through soil shading and slower decomposition rates. We explored whether characteristics of roots and root-associated fungi important to N acquisition responded to changes in density at the TTE. We characterized carbon (C) and N tissue concentrations and natural abundance isotope signatures, ectomycorrhizal colonization, along with the uptake of nitrogen-15 (15N) enriched tracers in glycine, ammonium, and nitrate form by excised fine roots of Cajander larch (Larix cajanderi) from 10 stands arrayed across a tree density gradient at the taiga-tundra ecotone in far northeastern Siberia.随着气候变暖，苔原-泰加林交错带（tundra-taiga ecotone, TTE）的树木密度与森林生产力预计将提升，并可能对气候系统产生潜在反馈。然而，氮（nitrogen, N）竞争或会影响TTE的动态变化。更高的树木密度大概率会增加氮需求，同时通过土壤遮阴与更低的分解速率减少氮供应。本研究探究了对氮获取至关重要的根系及根系共生真菌特征是否会随TTE处的树木密度变化产生响应。我们针对西伯利亚东北部泰加林-苔原交错带沿树木密度梯度分布的10个林分，采集了卡氏落叶松（Larix cajanderi）的离体细根，对其碳（carbon, C）与氮组织浓度、自然丰度同位素特征、外生菌根定殖情况，以及甘氨酸、铵态氮、硝态氮形式的氮-15（15N）富集示踪剂的摄取量进行了表征分析。