近60年来印江河流域极端气候演变及其对净初级生产力和归一化植被指数的影响

Abstract

极端气候事件的发生改变了区域水热条件，并影响着生态环境变化。然而，目前长时间尺度上极端气候的演变规律及其对生态环境的影响尚不明晰。采用Mann-Kendall趋势及突变检验法、连续小波变换和Hurst指数法揭示了喀斯特槽谷印江河流域极端气候的变化趋势、突变时间、周期性特征和未来演变规律，并利用Lindeman-Merenda-Gold模型定量评估了极端气候溶变对生态环境变化的影响。结果表明：（1）印江河流域极端气温显著上升，降雨量增多，呈现湿热多雨的气候特征。未来极端气温事件持续等级将更高，持续强度也更强。（2）同类型极端气候具有潜在的关联性，但不同类型极端气候间的影响较小，且多呈负相关。（3）印江河流域平均净初级生产力（NPP）和归一化植被指数（NDVI）在2000-2015年间呈现相反的变化趋势，NPP平均值为598.53 g C m^-2 a^-1，平均减少速率为-3.32 g C m^-2 a^-1。NDVI平均值为0.59，平均增长速率为0.0013/a。（4）冷持续指数（CSDI）、平均温差（DTR）、系统阈值结冰日数（ID6.4）和生长期长度（GSL）对NPP的贡献较大，贡献率分别12.64%、11.50%、11.05%和7.4%。其中，CSDI、DTR、GSL对NPP变化表现为负贡献，而ID6.4则表现为正贡献。大部分极端气候指数对NPP变化的贡献都不超过5%。ID6.4对NDVI变化的影响最大，暖夜日数（TN90p）、热持续指数（WSDI）和暖昼日数（TX90p）相对次之，贡献率分别为13.67%、13.54%、12.95%和10.02%。总体上看，在2000-2015年间，印江河流域湿热多雨的气候对NDVI增长有促进作用，但是由于气温升高和降雨量增加的原因，对NPP累积产生了较大的负面影响。研究结果可为喀斯特槽谷流域气候预测、水资源管理及生态环境恢复提供参考依据。;The occurrence of extreme climate events has changed the regional hydrothermal conditions and affected the changes of ecological environment. However, at present, the evolution of extreme climate and its impact on ecological environment are unclear. Therefore, the methods of Mann-Kendall test, continuous wavelet transform, and Hurst exponent were applied to analyze the change trend, abrupt time, periodicity and future evolution of extreme climate events in Yinjiang River basin. Then, the Lindeman-Merenda-Gold model was used to quantitatively evaluate the impacts of extreme climate events to ecological environment change. The results were obtained:(1) The extreme temperature events in the Yinjiang River basin increased significantly, and the rainfall also increased, showing a hot and rainy climate. In the future, the level of extreme temperature events will be higher and the intensity will be stronger; (2) The same type of extreme climate had a potential correlation, but the influence of different types of extreme climate was small, and most of them showed negative correlation; (3) The average net primary production (NPP) and normalized difference vegetation index (NDVI) of the Yinjiang River basin showed an opposite trend from 2000 to 2015. The average NPP was 598.53 g C m^-2 a^-1 with the average reduction rate of -3.32 g C m^-2 a^-1 while the average NDVI value was 0.59 with an average growth rate of 0.0013/a; (4) The cold spell duration indicator(CSDI), diurnal temperature range (DTR), icing days defined by system threshold (ID6.4), and growing season length (GSL) contributed significantly to NPP, with contributions of 12.64%, 11.50%, 11.05%, and 7.4%, respectively. Among them, the CSDI, DTR, and GSL showed negative contribution to NPP changes, while ID6.4 showed positive contribution. Most extreme climate indices contributed less than 5% to the NPP changes. ID6.4 had the greatest impact on NDVI, followed by warm nights (TN90p), warm spell duration indicator (WSDI), and warm days (TX90p), with contribution rates of 13.67%, 13.54%, 12.95%, and 10.02%, respectively. On the whole, the study stressed that the hot and rainy climate in the Yinjiang River basin promoted the growth of NDVI during 2000-2015, but caused a significantly negative impact on the accumulation of NPP due to the increase of temperature and rainfall. The results can provide reference for climate prediction, water resources management and ecological environment restoration in a basin of karst trough valley.