Surface energy exchanges along a tundra-forest transition and feedbacks to climate
Surface energy exchanges along a tundra-forest transition and feedbacks to climate
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DOI：
10.1016/j.agrformet.2005.05.006
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发表时间：
2005-08-31
影响因子：
6.2
通讯作者：
McGuire, AD
中科院分区：
文献类型：
--
作者：
Beringer, J;Chapin, FS;McGuire, AD
地表能量交换的测量序列的五个站点代表的主要植被类型的过渡，从北极苔原森林。这是北方高纬度地区植被结构的主要转变。我们研究了植被结构对感热和蒸散率的影响，以评估高纬度变暖是否会改变这些植被类型的分布对气候的潜在反馈。测量是在理事会的苏厄德半岛，阿拉斯加，在代表苔原，低灌木，高灌木，林地（树线），和北方森林网站。从苔原过渡到森林的结构差异包括叶面积指数（LAI）从0.52增加到2.76，冠层高度从0.1米增加到6.1米，冠层复杂性普遍增加。植被结构的这些变化，导致在一个减少在0.19至0.10，以及在表面的能量分配的变化。体积表面阻力的水蒸气通量几乎保持不变的网站，显然是因为相结合的土壤和苔藓蒸发减少，而蒸腾增加沿着从苔原到森林的样带。在一般情况下，网站变得相对温暖和干燥沿着样带的对流通量越来越占主导地位的显热，明显的增加Bowen比从0.94到1.22。苔原与森林生长季平均日感热之差为21 W m（-2）。通量变化非线性沿着过渡，灌木和树木大大提高了向大气的热传递。这些增加可感热的植被结构变化可以反馈到局部到区域尺度上，从而增强变暖。这些植被对潜在高纬度变暖的影响程度比以前的模拟研究所建议的要大两到三倍。(c)2005 Elsevier B. V.保留所有权利。
Surface energy exchanges were measured in a sequence of five sites representing the major vegetation types in the transition from arctic tundra to forest. This is the major transition in vegetation structure in northern high latitudes. We examined the influence of vegetation structure on the rates of sensible heating and evapotranspiration to assess the potential feedbacks to climate if high-latitude warming were to change the distribution of these vegetation types. Measurements were made at Council on the Seward Peninsula, Alaska, at representative tundra, low shrub, tall shrub, woodland (treeline), and boreal forest sites. Structural differences across the transition from tundra to forest included an increase in the leaf area index (LAI) from 0.52 to 2.76, an increase in canopy height from 0.1 to 6.1 m, and a general increase in canopy complexity. These changes in vegetation structure resulted in a decrease in albedo from 0.19 to 0.10 as well as changes to the partitioning of energy at the surface. Bulk surface resistance to water vapor flux remained virtually constant across sites, apparently because the combined soil and moss evaporation decreased while transpiration increased along the transect from tundra to forest. In general, sites became relatively warmer and drier along the transect with the convective fluxes being increasingly dominated by sensible heating, as evident by an increasing Bowen ratio from 0.94 to 1.22. The difference in growing season average daily sensible heating between tundra and forest was 21 W m(-2). Fluxes changed non-linearly along the transition, with both shrubs and trees substantially enhancing heat transfer to the atmosphere. These changes in vegetation structure that increase sensible heating could feed back to enhance warming at local to regional scales. The magnitude of these vegetation effects on potential high-latitude warming is two to three times greater than suggested by previous modeling studies. (c) 2005 Elsevier B.V. All rights reserved.