Seasonal variation in the energy and water exchanges above and below a larch forest in eastern Siberia
Seasonal variation in the energy and water exchanges above and below a larch forest in eastern Siberia
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DOI：
10.1002/hyp.219
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发表时间：
2001-06
影响因子：
3.2
通讯作者：
T. Ohta;T. Hiyama;Hiroki Tanaka;T. Kuwada;T. Maximov;T. Ohata;Y. Fukushima
中科院分区：
文献类型：
--
作者：
T. Ohta;T. Hiyama;Hiroki Tanaka;T. Kuwada;T. Maximov;T. Ohata;Y. Fukushima
森林中的水和能量交换构成了最重要的水文气象系统之一。与温暖潮湿地区相比，对高纬度森林中的水和热量交换的研究要少得多。在西伯利亚的整个生长季节，包括融雪和落叶季节，几乎没有观测到这个系统。研究了东西伯利亚落叶松林融雪季至落叶季的能量和水分收支特征。潜热通量受落叶松蒸腾活动的影响较大，随着落叶松开始抽叶，潜热通量迅速增大。当时感热有所下降，但净全波辐射有所增加。因此，鲍文比的季节变化呈明显的“U”形，最小值(1.0)出现在6、7月份。早春的波文比很高(10-25)，恰好在开叶前。大叶模型的冠层阻力远远超过空气动力阻力，且波动范围更大。冠层阻力受饱和亏的制约较大，其最小值为10 0 S m−1(10 mm S−1电导)。这一最小树冠阻力高于温暖潮湿地区森林的值，但与其他北方针叶林的测量值相似。叶片衰老对冠层抗性也有影响，落叶季节的冠层抗性高于落叶季节。1998年4月21日至9月7日的平均蒸散速率为1.16 mm/d−1，最大蒸散速率2.9 mm/d−1出现在7月上旬。从6月1日到8月31日的生长季，这一速率为1.5 mm/d−1。森林的总蒸散量(151 Mm)超过降水量(106 Mm)，相当于总输水量(211 Mm)的73%，包括雪水当量。林下蒸散量占总蒸散量的35%，截留蒸发量占总降水量的15%。林冠稀疏，叶面积指数低，林下蒸散量大，截留蒸发量低。版权所有©2001 John Wiley&Sons，Ltd.
The water and energy exchanges in forests form one of the most important hydro‐meteorological systems. There have been far fewer investigations of the water and heat exchange in high latitude forests than of those in warm, humid regions. There have been few observations of this system in Siberia for an entire growing season, including the snowmelt and leaf‐fall seasons. In this study, the characteristics of the energy and water budgets in an eastern Siberian larch forest were investigated from the snowmelt season to the leaf‐fall season. The latent heat flux was strongly affected by the transpiration activity of the larch trees and increased quickly as the larch stand began to foliate. The sensible heat dropped at that time, although the net all‐wave radiation increased. Consequently, the seasonal variation in the Bowen ratio was clearly ‘U’‐shaped, and the minimum value (1·0) occurred in June and July. The Bowen ratio was very high (10–25) in early spring, just before leaf opening. The canopy resistance for a big leaf model far exceeded the aerodynamic resistance and fluctuated over a much wider range. The canopy resistance was strongly restricted by the saturation deficit, and its minimum value was 100 s m−1 (10 mm s−1 in conductance). This minimum canopy resistance is higher than values obtained for forests in warm, humid regions, but is similar to those measured in other boreal conifer forests. It has been suggested that the senescence of leaves also affects the canopy resistance, which was higher in the leaf‐fall season than in the foliated season. The mean evapotranspiration rate from 21 April 1998 to 7 September 1998 was 1·16 mm day−1, and the maximum rate, 2·9 mm day−1, occurred at the beginning of July. For the growing season from 1 June to 31 August, this rate was 1·5 mm day−1. The total evapotranspiration from the forest (151 mm) exceeded the amount of precipitation (106 mm) and was equal to 73% of the total water input (211 mm), including the snow water equivalent. The understory evapotranspiration reached 35% of the total evapotranspiration, and the interception evaporation was 15% of the gross precipitation. The understory evapotranspiration was high and the interception evaporation was low because the canopy was sparse and the leaf area index was low. Copyright © 2001 John Wiley & Sons, Ltd.