秦巴山地植被冠层降雨截留时空分异特征及驱动因素

冠层截留研究对于了解区域水资源分配和评估生态水文功能至关重要,山地复杂多样的环境使其存在较大的不确定性,遥感的发展为揭示山地系统冠层截留的特征提供了机遇。以秦巴山地为研究区,基于降雨数据和叶面积指数遥感数据,耦合植被冠层降雨截留模型,定量模拟和分析秦巴山地2003-2020年植被冠层降雨截留能力及其时空变化特征,并验证其精确性;采用地理探测器、相关分析和约束线法探究冠层截留的驱动因素。结果表明:(1) 与PML_V2数据集和实测数据相比,3.5以下的均方根误差和0.75以上的有效系数证实了A.P.J.DE ROO模型模拟的可靠性。(2) 近18年截留量和截留率整体呈上升趋势,截留率在2015年发生逆转,由增(0.08%/a)向减(-0.15%/a)转变。(3) 秦巴山地冠层截留总体上呈西部高山区和东北部边缘低,秦岭和大巴山区高的空间格局,其随海拔上升呈现"上升-稳定-下降"的分布特征;空间变化以上升趋势为主,显著下降的区域主要分布在汉江河谷的中心;低海拔区域变化差异较大,中海拔区域以显著增加为主,高海拔区域无显著变化。(4) 叶面积指数和降雨量是影响冠层截留的主要因子,约束关系分别为正线型和正凸型;阔叶林截留率与小降雨事件的相关性高,针叶林、灌丛截留率与强降雨事件相关性较强,气候因子对冠层截留的影响在类别和解释程度上存在空间差异。研究可为区域尺度冠层截留的估测提供思路,且有助于评估气候变化背景下生态系统对水循环的影响。

Spatio-temporal variations and driving factor analysis of rainfall interception by vegetation canopy in the Qinling-Daba Mountains

Studying canopy interception is crucial in the understanding of regional water resources allocation and evaluating eco-hydrological functions. However, the complex and diverse environment in mountainous regions means that field measurement results about canopy interception can be highly inaccurate. By leveraging the advancements in remote sensing, this study aimed to reveal the spatial and temporal variability of canopy interception in mountain systems. By coupling a canopy interception model with precipitation data and leaf area index remote sensing data, this study quantitatively simulated and analyzed the rainfall interception capacity of vegetation canopy in the Qinling-Daba Mountains from 2003 to 2020, and analyzed its accuracy from the aspects of point scale and surface scale. Factors influencing canopy interception were investigated using geographical detector, sensitivity analysis, and correlation analysis. The results showed that: (1) the A.P.J.DE ROO model simulation had a root mean square error below 3.5 and an effective coefficient above 0.75, which showed that the model was reliable when compared with the canopy interception evaporation raster data and the measured point data. (2) The rainfall interception and interception rate showed an overall upward trend over the past 18 years, except for a reversal in 2015, when the interception rate shifted from an increase of 0.08%/a to a decrease of -0.15%/a. (3) The spatial distribution patterns of rainfall interception and interception rate were generally similar, with local variations. Higher values were observed in the Qinling and Daba Mountains, whereas lower values were found in the western high mountains and northeastern edges. The rainfall interception capacity of vegetation canopy showed a "rise-stability-decline" pattern with the increasing altitude. Spatial change predominantly indicated an upward trend, with a decrease primarily located in the central Hanjiang River Valley. Notably, the low altitude area exhibited distinct changes, with a significant increase in the middle altitude area and no significant change in the high altitude area. (4) Canopy interception was primarily influenced by leaf area index and rainfall, the constraint relations were positively linear and positively convex, respectively. The interception rate of broad-leaved forests showed a high correlation with small rainfall events, whereas coniferous forests and shrubs exhibited a strong correlation with heavy rainfall events. The influence of climatic factors on canopy interception varied spatially in terms of category and interpretation degree. This study could provide ideas for estimating canopy interception at the regional scale, and be used to improve the evaluation of ecosystem impacts on the water cycle when affected by climate change.