祁连山区甘青锦鸡儿灌丛单株的穿透雨分布特征

Distribution of Throughfall under the Shrub Canopy of Single Caragana tangutica Clump in the Qilian Mountains

【目的】探讨祁连山西水林区甘青锦鸡儿灌丛冠下穿透雨分布特征及其影响因素,为定量评价祁连山区甘青锦鸡儿灌丛的生态水文功能和基于生态过程的灌丛水文模型的参数化提供数据支撑。【方法】基于祁连山甘青锦鸡儿种群特征调查,在坡中位选取3株代表性甘青锦鸡儿灌丛,沿冠层枝条辐散方向选取观测断面,在断面上布设承雨器,对叶量稳定期内12次降雨事件的冠层穿透雨及其空间分布进行测定,分析穿透雨与降雨特征的关系以及冠下穿透雨空间分布格局及其影响因素。【结果】甘青锦鸡儿灌丛冠下穿透雨在不同降雨事件中差异较大,观测期内单株灌丛的平均穿透雨率为45.9%;穿透雨量与降雨量之间呈线性关系（y=0.626 2x-1.018 1,R2=0.983）,穿透雨率与降雨量之间呈二次函数关系（y=-0.033 6x2＋1.806 8x＋34.094,R2=0.575 3）;穿透雨率具有明显的空间异质性,平均穿透雨率沿径向由距灌丛基部10 cm处的28.98%单调递增至距基部90 cm处的62.19%,受冠层结构特征的影响,在距灌丛基部30~50 cm的区间内增加量最大,占总增加量的61%;穿透雨率沿径向的空间变异系数随降雨量的增大而降低,在降雨量小于10 mm的小降雨事件中穿透雨率的空间变异性尤为显著;穿透雨率的空间分布格局还受降雨强度的影响,当降雨强度为0.97和4.27 mm·h-1时,距灌丛基部10~30和50~90 cm的穿透雨率有明显差异,而当降雨强度为25.06 mm·h-1时,穿透雨率沿径向的差异被弱化。【结论】单株甘青锦鸡儿灌丛的穿透雨特征同时受降雨特征和冠层结构特征的影响,其冠下穿透雨量与降雨量及穿透雨率与降雨量间的关系与前人相关研究结果一致。冠层特征决定了冠下穿透雨的空间分布总格局,但穿透雨的空间分布格局也受降雨量和降雨强度的影响,降雨量增大或降雨强度达到一定程度时均会降低冠下穿透雨的空间异质性。

【Objective】In this study,the distribution characteristics of throughfall under the Caragana tangutica shrub canopy and its influence factors were researched. The aims of this paper were to provide the basal data for quantitatively evaluating the eco-hydrology function of Caragana tangutica shrub in the Qilian Mountains as well as parameterized the hydrological model which relying on the ecological process. 【Method 】Based on the investigation of population characteristics,three representative Caragana tangutica shrubs were selected on the middle slope. The measurement radial sections along the branch radial direction were selected. Containers for rain water collection were installed at each radial section. The throughfall and its spatial distribution were measured after 12 rainfall events at the period with stable foliage volume. Then the relationship between throughfall and rainfall,as well as the spatial distribution pattern and its influence factors were analyzed. 【Result】The throughfall under Caragana tangutica canopy exhibited evident differences in different rainfall events. In the observation period,the mean throughfall rate of individual shrub was 45. 9%. There was a linear relationship（ y = 0. 626 2x- 1. 018 1,R2= 0. 983） between throughfall volume and rainfall and a quadratic function relationship between throughfall rate and rainfall（ y =- 0. 033 6x2＋ 1. 806 8x ＋ 34. 094,R2= 0. 575 3）. Thethroughfall rate exhibited an evident spatial heterogeneity and monotonously increased from 28. 98% at 10 cm distance to the shrub base to 62. 19% at 90 cm distance to the shrub base along the radial direction. Influenced by the canopy structure characteristics,the biggest increment was occurred at a distance of 30—50 cm,which accounted for 61% of the total increment. The spatial variable coefficient of throughfall rates along the radial direction were decreased with the increasing rainfall,which expressed more remarkable when the rainfall was less than 10 mm. The distribution pattern was also changed when the rainfall intensity was increased. When the rainfall intensity were 0. 97 or 4. 27 mm·h- 1,there was an evident difference of throughfall rates between 10—30 cm and 50—90 cm,while this difference could be weaken when the rainfall intensity was 25. 06 mm·h- 1.【Conclusion】The throughfall features of individual Caragana tangutica shrub were influenced by characteristics of both rainfall and the canopy structural. The relationships between throughfall volume and rainfall as well as between throughfall rate and rainfall were in accordance with findings of correlational researches that conducted by predecessors. The general spatial distribution pattern of throughfall under the canopy was determined by the canopy features,while this pattern was also influenced by rainfall volume and rainfall intensity. The increase of rainfall or when the rainfall intensity reached a certain extent both can decrease the spatial heterogeneity of throughfall under the canopy.