Trees out-forage understorey shrubs for nitrogen patches in a subarctic mountain birch forest
Trees out-forage understorey shrubs for nitrogen patches in a subarctic mountain birch forest
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在亚北极山地白桦林中，树木以林下灌木为食来获取氮斑块
DOI：
10.1111/oik.09567
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发表时间：
2022
期刊：
影响因子：
3.4
通讯作者：
Friggens N
中科院分区：
文献类型：
--
作者：
Friggens N
由根和菌根真菌获得并供应给植物叶片的氮(N)在亚北极树线是一种限制生长的养分。由于这一局限性，种间N的竞争和获取是植物群落组成和分布的重要控制因素。乔木和灌木获取N的能力在经历气候变化驱动的物种范围变化和初级生产力变化的这一交错带形成群落动态。利用15N土壤标记，研究了林线林地土壤无机氮的去向，以及乔木和林下灌木接触土壤N的空间距离。将15N注射到1m2的土壤根区，从距离标记土壤1-50m的乔木和距离标记土壤0.5-11m的乔木和林下灌木采集叶片样本。15N标记在距离标记土壤5米的山桦树和距离标记土壤2米的灌木中被发现。我们估计，1.27%的脉冲源N存在于白桦树的叶中，相比之下，1.16%的脉冲源N存在于林下。然而，山地白桦树只贡献了生态系统叶面积指数(LAI)的31%，因此与其对生态系统叶面积指数(LAI)的贡献相比，白桦树冠上的附加标签分配不成比例。山地桦树和林下灌木在根系和菌根探索距离以及群落N分配上的差异可能赋予树木在氮和营养斑块方面的竞争优势，这可能会改变这些森林中的植物群落结构。考虑到亚北极地区气候驱动的树木和高大灌木的预计扩张，这一点尤其重要，这可能会对生态系统N和碳(C)循环以及群落组成和生物多样性产生影响。
Nitrogen (N), acquired by roots and mycorrhizal fungi and supplied to plant foliage, is a growth‐limiting nutrient at the subarctic treeline. Due to this limitation, interspecific competition and acquisition of N is an important control on plant community composition and distribution. The ability of trees and shrubs to access N shapes community dynamics at this ecotone undergoing species range shifts and changes in primary productivity driven by climate change. Using15N soil labelling we investigate the fate of soil inorganic N, and spatial distances over which trees and understorey shrubs access soil N, in a treeline forest.15N was injected into soil rooting zones in discrete 1 m2patches and foliar samples were collected from trees between 1 and 50 m away, and understorey shrubs between 0.5 and 11 m away from labelled soil. The15N label was found in mountain birch trees up to 5 m, and in understorey shrubs up to 2 m, away from labelled soil. We estimate that 1.27% of pulse‐derived N was found in foliage of birch trees, compared to 1.16% in the understorey. However, mountain birch trees contributed only 31% of ecosystem leaf area index (LAI), thus there was a disproportionate allocation of added label to the birch canopy compared with its contribution to ecosystem LAI. The difference in root and mycorrhizal exploration distances and community N partitioning between mountain birch trees and understorey shrubs may confer competitive advantage to trees with respect to nitrogen and nutrient patches, which may alter plant community structures within these forests. This is particularly important considering predicted climate‐driven tree and tall shrub expansion in subarctic regions, with likely consequences for ecosystem N and carbon (C) cycling, as well as for community composition and biodiversity.