RESUMO
Under climate warming, extreme drought events (EDEs) in southwestern China have become more frequent and severe and have had significant impacts on vegetation growth. Clarifying the influence of soil and meteorological droughts on the vegetation photosynthetic rate (PHR) and respiration rate (RER) can help policymakers to anticipate the impacts of drought on vegetation and take measures to reduce losses. In this study, the frequency and features of EDEs from 1990 to 2021 were analyzed using the standardized precipitation evapotranspiration index, and the longest-lasting and most severe EDE was chosen to assess the effects of drought on vegetation activity. Then, a land surface model was used to simulate the vegetation PHR and RER. Finally, the effects of the EDE on the vegetation PHR and RER were analyzed from the perspectives of soil and meteorological droughts. The results revealed that from 1990 to 2021, a total of 11 EDEs were observed in southwestern China, and the longest-lasting and most severe EDE occurred in 2009-2010 (EDE2009/2010). EDE2009/2010 significantly reduced the monthly mean PHR and RER by 9.82 g C m-2 month-1 and 0.80 g C m-2 month-1, respectively, causing a cumulative reduction of approximately 5.61 × 1013 g C. Soil and meteorological droughts had a driving force of 39 % on the PHR changes and an explanatory force of 42 % on the RER reduction. In particular, the soil drought had an average explanatory force of 25 % on the PHR and made a contribution of 24 % to the RER. The drought affected different types of vegetation differently, and crops were more susceptible than grassland and forests on the monthly time scale. The vegetation exhibited resilience to drought, returning to normal PHR and RER levels 2 months after the end of EDE2009/2010. This research contributes to understanding and predicting the impact of EDEs on vegetation growth in southwestern China.
RESUMO
Soil erosion estimation has attracted considerable attention from the scientific community and governments because of its importance to sustainable regional development. In karst areas, the heterogeneous environment and rocky desertification create difficulties in determining the influencing factors and spatial patterns of soil erosion. A quantitative analysis of karst soil erosion distribution was conducted by applying the revised soil loss equation model and the geographical detector method of attribution identification, which was based on spatial variance analysis. The results show that soil erosion was most severe in areas with an elevation of 1200-1800 m and intense anthropogenic activity. When the vegetation coverage was below 0.5-0.6, soil erosion showed characteristics of a source-limited regime and increased with the increasing vegetation coverage. When the vegetation coverage was higher than 0.5-0.6, soil erosion followed a transport-limited regime and decreased with the increasing vegetation coverage. The factor detector showed land use to be the dominant factor, explaining 51% of soil erosion distribution. Among various land use types, dry land had the greatest vulnerability to soil erosion. Slope served as a controlling factor at large scales, especially when combined with annual precipitation exceeding 1500 mm, and in dry and grassland areas. From the attribution analysis of multiple factors, the combination of land use and slope was the controlling interaction factor explaining 68% of soil erosion distribution. The methods and results of this research could serve as scientific references for decision makers and researchers exploring the characteristics of soil erosion to develop effective measures for its control.
