Evaluation and Quantitative Attribution Analysis of Water Yield Services in the Peak-cluster Depression Basins in Southwest of Guangxi,China

Karst environmental issues have become one of the hot spots in contemporary international geological research. The same problem of water shortage is one of the hot spots of global concern. The peak-cluster depression basins in southwest of Guangxi is an important water connotation and ecological barrier areas in the Pearl River Basin of China. Thus, studying the spatial and temporal variations and the influencing factors of its water yield services is critical to achieve the sustainable development of water resources and ecological environmental protection in this region. As such, this paper uses the Integrated Valuation of Ecosystem Services and Tradeoffs(InVEST) model to assess the spatial and temporal variabilities of water yield services and its trends in the peak-cluster depression basins in southwest of Guangxi from 2000 to 2020. This work also integrates precipitation(Pre), reference evapotranspiration(ET), temperature(Tem), digital elevation model(DEM), slope, normalized difference vegetation index(NDVI), land use/land cover(LULC) and soil type to reveal the main factors that influence water yield services with the help of Geodetector. Results show that: 1) in time scale,the total annual water yield in the study area show a fluctuating and increasing trend from 2000 to 2020, with a growth rate of 7.3753 × 10^(8)m^(3)/yr, and its multi-year average water yield was 538.07 mm;2) in spatial pattern, with high yield areas mainly distributed in the south of the study area(mainly including Shangsi County, Pingxiang City, Ningming County, Longzhou County and Jingxi County), and low yield areas mainly distributed in Baise City and Nanning City;3) the dominant factor of water yield within karst and non-karst landforms is not necessarily controlled by precipitation, and the explanation degree of DEM factors in karst areas is significantly higher than that in non-karst areas;4) amongst the climatic factors, Pre, ET and Tem are dominant in the spatial pattern of region water yield capacity. among which Pre has the highest explanatory power for the spatial heterogeneity of annual water production, with q values above0.8, and each driver showed a significant interaction on the spatial distribution of water yield, with Pre exhibiting the strongest interaction with LULC.

2000-2021年桂西南峰丛洼地流域植被净初级生产力演变特征及其归因

监测植被净初级生产力的演变特征及其驱动力机制,对于深入了解陆地碳循环机制和促进生态环境可持续发展有着及其重要的作用。文章基于MOD17A3数据集植被净初级生产力(NPP)产品评估了2000−2021年桂西南典型喀斯特峰丛洼地流域植被净初级生产力的时空演变,并借助Theil-Sen Median趋势分析、Mann-Kendall检验方法、Hurst指数以及地理探测器等,研究区域内植被净初级生产力的空间分布、未来趋势、可持续性及驱动机制。结果表明:(1)2000−2021年研究区植被NPP均值为945.23 gC∙m^(−2)∙a^(−1),呈现出上升趋势,增加速率为3.5596 gC∙m^(−2)∙a^(−1)。喀斯特区域(4.5148 gC∙m^(−2)∙a^(−1))>研究区域(3.5596 gC∙m^(−2)∙a^(−1))>非喀斯特区域(2.7219 gC∙m^(−2)∙a^(−1));(2)植被NPP高值区域在防城港市周边,值皆大于1200 gC∙m^(−2)∙a^(−1);低值区散布于水文线附近;(3)Sen变化趋势显示,研究区22年间植被NPP增加区域面积(77.98%)显著大于减少区域面积(22.02%)。Hurst指数显示,区域植被NPP介于0~1之间,平均值为0.65,呈现出向负偏态分布;(4)土地利用/覆被、植被覆盖度与高程因子是本研究区植被NPP的显著控制因子,其次为坡度及土壤类型。

基于DEM的喀斯特峰丛洼地地貌信息提取及形态特征分析

文章以桂西南典型喀斯特地貌--峰丛洼地为研究对象,基于DEM数据采用水文法、鞍座法提取出峰丛洼地,在此基础上借助于空间分析方法、分形理论等对研究区的峰丛洼地结构形态特征、空间分布进行定量分析和研究。结果表明:(1)运用水文分析方法能有效提取鞍部点,有效识别出洼地凹陷,提取鞍部点精度为50.00%,而鞍座法提取鞍部点的精度为79.80%;(2)94%的峰丛洼地形态为盆形,小部分为深锥形和碟状形。研究区洼地斑块周长-面积的关系为y=0.5772x+0.2674,二者的相关系数R2=0.9462,周长-面积的分维数D=1.15,洼地图斑镶嵌结构较稳定;(3)80%的峰丛洼地分布于研究区南部、北部的石灰岩与白云岩互层地区和连续性石灰岩上,中部碎屑岩岩层上峰丛洼地发育不明显。

峰丛洼地流域植被覆盖度时空演变及其归因

采用像元二分模型估算2000~2020年桂西南峰丛洼地流域的植被覆盖度,并借助Theil-Sen Median趋势分析、Mann-Kendall检验方法以及Hurst指数等分析方法对研究区域内植被覆盖度的空间分布、未来趋势和可持续性进行深入解析,最后引入地理探测器对其驱动力因素进行定量化分析.结果表明:(1)年际变化上,流域21a间植被覆盖度呈递增趋势,增速为0.6754a-1.喀斯特区域增长速率(0.774a-1)>非喀斯特区域增长速率(0.5751a-1);(2)空间尺度上,研究区域植被覆盖度整体上呈现出“北高东低”的格局,其中82.68%的区域植被覆盖度显著增加,仅有0.61%区域表现为显著减少;(3)未来变化趋势上,区域植被覆盖度的Hurst指数介于0~1之间,平均值为0.8207,呈现出向右单峰偏斜,即研究区未来植被覆盖度呈现出持续改善的趋势;(4)驱动力机制上,土地利用/覆被(LULC)是整个研究区域植被覆盖度的主导因素;各驱动因子对植被覆盖度空间分布均表现出明显的交互作用,其中土地利用/覆被(LULC)与人口密度(pop)的交互作用最强.