Spatial pattern of Land use types and their driving mechanism of watershed lagged effect in Karst drainage basin, Central Guizhou of China*

Abstract

Abstract The occurrence of drought indicates that there is no rainfall or little rainfall within a certain period. Nevertheless, no or little rainfall within a certain time implies that drought may not happen. The drought occurrence in different regions or seasons shows a certain lag to some extent. The lag time and intensity (i.e. the contribution rate of rainfall in previous period to runoff in current period) are deeply affected by watershed water storage capacity. Subsequently, rainfall deficit is a necessary and insufficient for the droughts. To reveal the mechanism of watershed lagged effects and the impact of human activities on droughts, the characteristics of lagged effects and human activities in Central Guizhou of China are analyzed by the Lagged index and Landscape index based on land use data, rainfall and runoff data during the period 1971–2016. The results demonstrate that the impact of the same land use type at different ages 1970s-2010s on watershed lagged intensity has a significant difference (P < 0.001). Among them, the impact of woodland, grassland and cultivated land gradually increases with the passage of time, and the cultivated land reaches the maximum in the 2000s. Nevertheless, the water body and construction land do not change significantly with the increase of years. The influence of land use type transfer on watershed lagged effect is particularly significant (P < 0.001). With the extension of lagged variables (periods), the impact of forest land type transfer on lag intensity gradually increases and reaches the maximum value at the lag-1 variable (Xt−1), and it is not of great significance for the rest of types. The impact of principal components (Zs) for morphological characteristics of land use types at different time scales (1–12 months), different lagged variables (Xt-Xt−3) and different ages (1970s-2010s) on watershed lagged effect is particularly significant (P < 0.001). Among them, this impact of grassland and water body on lagged intensity gradually increases with the time scales increasing and reaches the maximum value at the scale of 9 months, followed by the woodland and cultivated land, with reaching the maximum at the scales of 9 and 6 months respectively. Meanwhile, construction land is the smallest and reaches the maximum at the 9-month scale. As a subsequence, this study enriches the research content of landscape ecology, and it provides a theoretical basis for revealing the mechanism of agricultural and hydrological droughts in Karst drainage basins.