Spatiotemporal variation of forest land and its driving factors in the agropastoral ecotone of northern China

As an important natural resource,forest land plays a key role in the maintenance of ecological security.However,variations of forest land in the agropastoral ecotone of northern China(AENC)have attracted little attention.Taking the AENC as an example and based on remote-sensing images from 2000,2010 to 2020,we explored the spatiotemporal variation of forest land and its driving factors using the land-use transfer matrix,spatial autocorrelation analysis and spatial error model.The results showed that from 2000 to 2020,the total area of forest land in the AENC increased from 75,547.52 to 77,359.96 km^(2) and the changes were dominated by the transformations among forest land,grassland and cropland,which occurred mainly in areas with the elevation of 500-2000 m and slope of 15°-25°.There was obvious spatial agglomeration of forest land in the AENC from 2000 to 2020,with hot spots of forest land gathered in the southern marginal areas of the Yanshan Mountains and the low mountainous and hilly areas of the Loess Plateau.The sub-hot spots around hot spots moved southward,the sub-cold spots spread to the surrounding areas and the cold spots disappeared.The spatiotemporal variation of forest land resulted from the interactions of natural environment,socioeconomic and policy factors from 2000 to 2020.The variables of average annual precipitation,slope,terrain relief,ecological conversion program and afforestation policy for barren mountains affected the spatial pattern of forest land positively,while those of annual average temperature,slope and road network density influenced it negatively.

Spatial distribution of water and wind erosion and their influence on the soil quality at the agropastoral ecotone of North China

In semiarid regions,wind and water erosion are serious environmental and ecological problems around world.They have different impacts on soil quality over a range of spatial scales.Analyzing the spatial distribution of soil erosion and understanding the impacts of wind and water erosion on soil quality at the regional scale is vital for mitigating soil erosion risk.In this study we explore the spatial distributions of water and wind erosion around Zhangjiakou city which suffers both water and wind erosion contemporaneously,and detect the influence of soil erosion on soil quality.We find that annual wind erosion intensities range 4.99-10.05 t ha-1 yr-1,and annual water erosion intensities range 2.92-4.14 t ha-1 yr-1.Areas with higher potential wind and total erosion risk occur mainly in northwest and southeast Zhangjiakou city,whereas potential water erosion risk is highest in the southwest and central regions.The highest erosion rates are concentrated in gentle parts of the landscape,where agriculture has led to low vegetation cover.Steeper portions of the landscape,which remain forested,have lower erosion rates.These spatial patterns are dominated by higher wind erosion,which correlates with sur-face soil coarsening and higher water infiltration,whereas the soil water holding capacity decreases with increasing wind erosion rates.In regions with high water infiltration rates,we find the intensity of water erosion weakened.To mitigate risks of soil degradation,suitable erosion measures should be imple-mented according to the dominant erosion type,which varies in space.