Root tissue chemistry, mycorrhizal colonization, and uptake of 15N 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 C and N tissue concentrations and natural abundance isotope signatures, ectomycorrhizal colonization, along with the uptake of 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.

气候变暖背景下，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有所提升，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。树木密度升高大概率会增加氮需求，同时通过土壤遮阴与分解速率放缓降低氮供应。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区域的密度变化产生响应。我们针对西伯利亚东北部偏远地区泰加林-苔原交错带内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（C）、氮（N）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、硝态氮形态的15N富集示踪剂摄取量进行了表征分析。