Analysis of the influence of the water balance process on the change of landscape patterns in the upper reaches of the Yangtze River

Abstract

Abstract Based on hydrometeorological data and land-use data (from 1980 to 2015), the effects of water balance on landscape patterns in the upper reaches of the Yangtze River were studied using water balance analysis, the landscape index method, and other methods. Eight appropriate landscape indices (NP, COHESION, LPI, AI, SHDI, CONTAG, SPLIT, and LS) were selected to explore the spatial and temporal characteristics of landscape patterns. From 1980 to 2015, the precipitation in the study area decreased by 6.97%, and the annual precipitation of farmland was maintained at about 1,050 mm. The evapotranspiration (ET) had little change in general, but it varies greatly under different land-use types. Soil water storage variables showed a downward trend, and soil water storage variables of various land-use types changed dramatically during the study period. The total number of patches increased and the patch shape became more complex. At the level of landscape structure, SHDI and SPLIT increased, while CONTAG and COHESION decreased, and the degree of patch fragmentation and landscape heterogeneity improved. Correlation analysis showed that from a time perspective, LSI, SPLIT, and SHDI were significantly negatively correlated with ET, and CONTAG was significantly positively correlated with ET. There was a significant negative correlation between SPLIT and soil water (SW), and a significant positive correlation between COHESION and SW. These results indicated that with the decrease of ET and soil water storage variables, patches became more dispersed and landscape patterns became more fragmented. From the perspective of spatial distribution, the increase of SW increased landscape diversity and decreased landscape connectivity and contagion. The correlation coefficients between SW and the three groups of landscape pattern indexes (SHDI, CONTAG, and COHESION) were higher than those between ET and the three groups of landscape pattern indexes, which meant that soil water is more correlated with landscape pattern characteristics, and the effect of soil water change on landscape heterogeneity is more obvious. The study of the relationship between hydrological processes and landscape pattern characteristics in this paper enriches and expands the theoretical method system of ecological hydrology and ecological environmental protection in arid/semi-arid regions in our country.