兴安落叶松林降雨再分配及其穿透雨的空间异质性

【目的】探究大兴安岭北部兴安落叶松林对降雨的截留再分配及树冠下穿透雨空间分布规律,了解兴安落叶松林生态水文过程。【方法】通过长期定位观测研究的方法,获取了2013年兴安落叶松林19场降雨事件的林外降雨、穿透雨和树干径流的观测数据,采用相关分析,总结了兴安落叶松林降雨再分配规律,比较了树冠下不同位置处穿透雨的变异性。【结果】观测期内兴安落叶松林的林冠截留量、穿透雨量和树干径流量依次为35.14、148.61和0.250 7 mm,分别占大气降雨量的19.10%、80.77%和0.14%; 不同降雨事件中,树冠不同位置处的穿透雨具有空间异质性; 当降雨量、温度等气象因子一致时,3/4树冠半径处的穿透雨变异最小,树冠外缘(4/4树冠半径处)变异最大; 当冠层结构稳定时,穿透雨的变异程度均随降雨量的增加而减小,二者呈一定的负相关性(P<0.01)。【结论】穿透雨是兴安落叶松林降雨再分配的主要水文分量(约占降雨量的81%),选择变异最小、最接近林分穿透雨率(误差约1%)的3/4树冠半径处布设穿透雨收集装置,能够适当减少野外工作量,提高科研观测效率,可为落叶松林区森林水文模型的参数化提供依据。

Rainfall redistribution and the spatial heterogeneity of throughfall in Larix gmelinii forest,northeast China

【Objective】 This study was conducted to gain an understanding of the rainfall distribution, spatial variability of throughfall and eco-hydrological processes in Larix gmelinii forest.【Method】 Data for the gross rainfall, throughfall and stemflow corresponding to 19 rainfall events were measured in L. gmelinii forest during the period of a stable canopy(Jul.-Aug. 2013)by long-term locating observation. Throughfall measurments were obtained from 46 rain gauges. The redistribution of rainfall in L. gmelinii forest was summarized and the variability of throughfall under the tree canopy at different sites was compared using correlation analysis. 【Result】 The results indicated that the canopy interception, throughfall and stemflow were 35.14, 148.61 and 0.250 7 mm during the observation period, which accounted for 19.10%, 80.77% and 0.14% of the rainfall in an open field, respectively. The spatial variability of throughfall under the tree canopy was estimated for different rainfall events. It was found that a 3/4 canopy radius resulted in the lowest spatial variability of throughfall and a 4/4 canopy radius, i.e., canopy edge, contributed to the highest throughfall when the meteorological factors(such as rainfall amounts and temperature)were coherent. Given the stable canopy structure, the variance coefficient of throughfall decreases with increasing rainfall depth significantly(P<0.01). 【Conclusion】 Throughfall is the main hydrology component during redistribution of rainfall in L. gmelinii forest(about 81% of rainfall). The 3/4 radius under the tree’s canopy were choosed to layout throughfall collection devices to reduce the field work and to improve scientific research efficiently because of its minimum variation and closest to throughfall ratio(error of about 1%). This may provide the base for the quarlitative analysis of eco-hydrological model of L. gmelinii forest.