Topographical Controls on Hillslope‐Scale Hydrology Drive Shrub Distributions on the Seward Peninsula, Alaska
Topographical Controls on Hillslope‐Scale Hydrology Drive Shrub Distributions on the Seward Peninsula, Alaska
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地形对山坡的控制——尺度水文驱动阿拉斯加苏厄德半岛的灌木分布
DOI：
10.1029/2020jg005823
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Lara, Mark J.
中科院分区：
文献类型：
--
作者：
Mekonnen, Zelalem A.;Riley, William J.;Grant, Robert F.;Salmon, Verity G.;Iversen, Colleen M.;Biraud, Sébastien C.;Breen, Amy L.;Lara, Mark J.
观察表明，灌木正在整个北极苔原上扩张，主要是在山坡上，主要是为了应对气候变暖。然而，地形对水文、养分动态和植物生长的影响可能会使灌木扩张背后的机制难以解开。我们研究了地形在确定灌木扩张中的作用，通过应用一个耦合的横断面版本的机械生态系统模型（ecosys）在阿拉斯加州苏厄德半岛的苔原山坡网站。模拟的主要植物功能类型的生物量同意与实地测量（R2= 0.89），并准确地代表了灌木扩张，在过去的30年中推断从卫星观测。在排水良好的顶部位置，冠层水势和植物氮（N）吸收模拟为植物和微生物水分胁迫低。中坡位土壤含水量适中，促进了土壤矿化和植物对氮的吸收，增加了灌木生物量。通过增加根系碳分配引发的共生固氮，进一步增强了中坡位置的落叶灌木生长。排水不良的下坡位置的缓坡导致饱和土壤条件，降低土壤O2浓度，导致根系O2吸收降低，养分吸收和植物生物量降低。一个模拟，删除网格单元之间的地形互连导致（1）平均灌木生物量低估了28%，（2）在不同的山坡位置灌木生产力过高或过低。我们的研究结果表明，土地模型需要考虑山坡尺度耦合的地表和地下水文，以准确预测北极生态系统中当前的植物分布和未来的轨迹。
Observations indicate shrubs are expanding across the Arctic tundra, mainly on hillslopes and primarily in response to climate warming. However, the impact topography exerts on hydrology, nutrient dynamics, and plant growth can make untangling the mechanisms behind shrub expansion difficult. We examined the role topography plays in determining shrub expansion by applying a coupled transect version of a mechanistic ecosystem model (ecosys) in a tundra hillslope site in the Seward Peninsula, Alaska. Modeled biomass of the dominant plant functional types agreed well with field measurements (R2= 0.89) and accurately represented shrub expansion over the past 30 years inferred from satellite observations. In the well‐drained crest position, canopy water potential and plant nitrogen (N) uptake was modeled to be low from plant and microbial water stress. Intermediate soil water content in the mid‐slope position enhanced mineralization and plant N uptake, increasing shrub biomass. The deciduous shrub growth in the mid‐slope position was further enhanced by symbiotic N2fixation primed by increased root carbon allocation. The gentle slope in the poorly drained lower‐slope position resulted in saturated soil conditions that reduced soil O2concentrations, leading to lower root O2uptake and lower nutrient uptake and plant biomass. A simulation that removed topographical interconnectivity between grid cells resulted in (1) a 28% underestimate of mean shrub biomass and (2) over or underestimated shrub productivity at the various hillslope positions. Our results indicate that land models need to account for hillslope‐scale coupled surface and subsurface hydrology to accurately predict current plant distributions and future trajectories in Arctic ecosystems.
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影响因子：
3.7
作者：
Swanson DK
通讯作者：
Swanson DK
影响因子：
4.8
作者：
CHAPIN, FS;SHAVER, GR;LAUNDRE, JA
通讯作者：
LAUNDRE, JA
北极苔原景观中基于地形的水文模型与斑块规模植被格局之间的关系
影响因子：
5.2
作者：
B. Ostendorf;J. Reynolds
通讯作者：
J. Reynolds
高大灌木调节针叶林-苔原生态交错带的非生物条件和植物群落
影响因子：
3.7
作者：
Cory A. Wallace;J. Baltzer
通讯作者：
J. Baltzer
影响因子：
3.1
作者：
Z. Mekonnen;R. Grant;C. Schwalm
通讯作者：
Z. Mekonnen;R. Grant;C. Schwalm