Energy partitioning and its biophysical controls above a grazing steppe in central Mongolia
Energy partitioning and its biophysical controls above a grazing steppe in central Mongolia
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DOI：
10.1016/j.agrformet.2006.03.010
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发表时间：
2006-03-01
影响因子：
6.2
通讯作者：
Sugita, Michiaki
中科院分区：
文献类型：
--
作者：
Li, Sheng-Gong;Eugster, Werner;Sugita, Michiaki
本文的目的是探讨蒙古中部典型草原上方的净全波辐射 (R.) 如何划分为三个组成部分：感热 (H)、潜热和土壤热 (G) 通量的季节变化。使用 R-n (E-F) 的蒸发分数和冠层表面电导 (g,) 详细解决了与生物和非生物变量相关的这种分配的季节变化，该系数源自 Penman-Monteith 方程的反演。该草原生态系统的表面能量分配呈现出以下特征：（1）能量分配以H为主，其次是相对较大的G，尽管这种格局在冠层表面湿润和植被充分发育的条件下会暂时改变； (2) 能量分配与冠层发育和土壤湿度条件的相关性解释了 EF 和 g 中观测到的方差的 79%。这两个因素都与叶面积指数 (A(L)) 或土壤含水量 (theta) 呈线性对应关系； (3) 大气蒸气压差 (delta e) 对 g(c) (R-2 = 0.97) 的影响是曲线形的，并且强烈影响能量分配。由于供水的限制，EF和gc均随着Delta e的增加而显着下降； (4) 短波太阳辐射(K-d)对E-F和g(c)的影响很大程度上取决于土壤湿度条件。当土壤湿度较高时，EF仍随Kd的增加而降低，而g对Kd似乎不敏感； (5)在日尺度上，在下午经常观察到冠层与大气的紧密耦合，表现为g(c)在lambda E和E-F中所起的下降作用。然而，在季节尺度上，E-F和g(c)的变化密切关注A(L)的变化以及该地点的降水事件或干湿循环。 (c) 2006 Elsevier B.V. 保留所有权利。
The objective of this paper was to explore the seasonal development of how net all-wave radiation (R.) above a typical steppe in central Mongolia is partitioned into the three components: sensible heat (H), latent heat and soil heat (G) flux. Seasonal variability of this partitioning in association with biotic and abiotic variables was addressed in detail using the evaporative fraction of R-n (E-F) and the canopy surface conductance (g,), which was derived from an inversion of the Penman-Monteith equation. The surface energy partitioning of this steppe ecosystem showed the following characteristics: (1) H dominated the energy partitioning, followed by a relatively large G, although this pattern was temporally altered under conditions when the canopy surface was wet and the vegetation was fully developed; (2) the correlation of the energy partitioning with canopy development and soil moisture conditions explained up to 79% of the observed variance in EF and g,. Both factors exhibited linear correspondences to leaf area index (A(L)) or soil water content (theta); (3) the effect of atmospheric vapour pressure deficit (delta e) on g(c) (R-2 = 0.97) was curvilinear and strongly influenced the energy partitioning. Due to the limitation of water supply, both EF and gc decreased significantly with increasing delta e; (4) the effect of short-wave solar radiation (K-d) on E-F and g(c) depended strongly on soil moisture conditions. When soil moisture was high, EF still showed a decrease with increasing Kd while g, seemed insensitive to Kd; and (5) on the daily scale, close coupling of the canopy with the atmosphere was often observed in the afternoon as represented by the declining role played by g(c) in lambda E and E-F. However, on the seasonal scale, variations in E-F and g(c) closely followed the variation in A(L) and the precipitation events or the dry-wet cycles at the site. (c) 2006 Elsevier B.V. All rights reserved.