Environmental drivers of spatial variation in whole-tree transpiration in an aspen-dominated upland-to-wetland forest gradient
Environmental drivers of spatial variation in whole-tree transpiration in an aspen-dominated upland-to-wetland forest gradient
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DOI：
10.1029/2007wr006272
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发表时间：
2008-02-29
影响因子：
5.4
通讯作者：
Kruger, Eric L.
中科院分区：
文献类型：
--
作者：
Loranty, Michael M.;Mackay, D. Scott;Kruger, Eric L.
假设代表性的中心的立场的测量是典型的输入模型，森林蒸腾量的立场和区域范围。这些输入不考虑林分边界或沿着水分梯度的蒸腾梯度，因此可能会导致大规模估计值出现偏差。在北方威斯康星州的森林湿地和高地森林之间的地形控制的梯度上，我们测量了173棵树的半小时液流（J（S））。我们的分析重点关注该地点的三种优势物种：颤白杨（Populus tremuloides Michx）、斑点桤木（Alnus incana（DuRoi）Spreng）和白色雪松（Thuja occidentalis L.）。边材面积（A（S））用于将J（S）换算为全树蒸腾（E-C）。由于空间格局隐含的过程，地质统计学分析，以量化的空间自相关模式在整个网站。一个简单的Jarvis型模型参数化使用Monte Carlo抽样方法被用来模拟E-C（EC-SIM）。EC-SIM与观测到的E-C（EC-OBS）进行了比较，并发现再现冠层蒸腾的时间趋势和空间变异。EC-SIM然后被用来检查空间自相关作为环境驱动程序的函数。我们没有发现空间自相关的J（S）从森林湿地到森林高地的梯度。E-C的空间自相关，这是由于空间变异的A（S），这表明物种的空间格局是重要的理解空间估计的蒸腾。然而，在EC-SIM的自相关的范围内线性下降，增加蒸汽压赤字，这意味着考虑空间变化的冠层气孔导度的敏感性D也是关键，以准确地按比例增加蒸腾空间。
Assumed representative center-of-stand measurements are typical inputs to models that scale forest transpiration to stand and regional extents. These inputs do not consider gradients in transpiration at stand boundaries or along moisture gradients and therefore potentially bias the large-scale estimates. We measured half-hourly sap flux (J(S)) for 173 trees in a spatially explicit cyclic sampling design across a topographically controlled gradient between a forested wetland and upland forest in northern Wisconsin. Our analyses focused on three dominant species in the site: quaking aspen (Populus tremuloides Michx), speckled alder (Alnus incana (DuRoi) Spreng), and white cedar (Thuja occidentalis L.). Sapwood area (A(S)) was used to scale J(S) to whole tree transpiration (E-C). Because spatial patterns imply underlying processes, geostatistical analyses were employed to quantify patterns of spatial autocorrelation across the site. A simple Jarvis type model parameterized using a Monte Carlo sampling approach was used to simulate E-C (EC-SIM). EC-SIM was compared with observed E-C (EC-OBS) and found to reproduce both the temporal trends and spatial variance of canopy transpiration. EC-SIM was then used to examine spatial autocorrelation as a function of environmental drivers. We found no spatial autocorrelation in J(S) across the gradient from forested wetland to forested upland. E-C was spatially autocorrelated and this was attributed to spatial variation in A(S) which suggests species spatial patterns are important for understanding spatial estimates of transpiration. However, the range of autocorrelation in EC-SIM decreased linearly with increasing vapor pressure deficit, implying that consideration of spatial variation in the sensitivity of canopy stomatal conductance to D is also key to accurately scaling up transpiration in space.