The driver-pattern-effect connection of vegetation dynamics in the transition area between semi-arid and semi-humid northern China

Abstract

Vegetation is at the nexus of water, soil, and the atmosphere, making it a significant indicator of climatic variability and shifts in human activity. The spatial attribution analysis of vegetation changes may help us to identify and estimate the relationship between variation in vegetation and different erosion types, and their correspondence may be in the antecedents and consequences of vegetation dynamics. Here, based on time series datasets for the Bashang Plateau and northern North China’s mountainous region from 1998 to 2015, we used trend analysis, partial correlation analysis, and univariate linear regression to investigate the sustainability of vegetation variations and to determine the driving mechanisms of climatic and anthropogenic factors in vegetation dynamics at the regional scale. Further, we applied correlation analysis and models (i.e., USLE and RWEQ) to detect the spatial heterogeneity of soil erosion dynamics and the effects of vegetation coverage variation on the dynamics of water erosion, wind erosion, and wind-water erosion. Our results revealed a significant increasing trend in Normalized Difference Vegetation Index (NDVI) and the improved area accounted for more than 80% of the study area. The response of vegetation variation to climatic factors displayed a high correlation with precipitation for a 1-month lag in the semi-humid area, especially in forestland, and with temperature for a 0-month lag in the semi-arid area, particularly in farmland. These results suggest human activity has had a greater effect on vegetation variations than climatic factors during 2011–2015, and that human activity was the dominant factor controlling vegetation changes in terms of the spatial distribution of major drivers; notably, the implementation of the vegetation restoration projects affected the spatiotemporal patterns of vegetation cover. During 1998–2015, the increased vegetation coverage played a dominant role in reducing water erosion of the forestland, and it had a vital impact on lessening wind erosion in open land and sparsely vegetated areas, while the increased fractional vegetation coverage (FVC) may have been a contributing factor to aggravated soil erosion in the wind-water erosion zone of grassland and forestland. Hence, the importance of the implementation of revegetation projects on soil erosion reduction should not be underestimated.