Background Vegetation coverage is an essential factor in monitoring and assessing soil erosion. It is critically impacted by the spatial heterogeneity of vegetation characters such as vegetation types, forest category and tree species. Although remote sensing is considered as an effective way to monitor the dynamic change of vegetation coverage in large area, field survey at fixed monitoring site is still necessary especially for understory vegetation.

Methods The purpose of this study is to localize a set of vegetation coverage monitoring sites in Jiangsu province. Multi-source data was used including map of vegetation regionalization, map of tree species, map of soil and water conservation, remote sensing images and digital elevation model. Spatial heterogeneity of vegetation characters was analyzed by taking the third-level soil and water conservation regions as the control units. On the basis of this, monitoring sites were sampled through stratified sampling and flitted according to observations through field survey.

Results 1) Ⅲ-4-2t, Ⅲ-5-3fn and Ⅲ-5-4nt belongs to the warm-temperate deciduous broad-leaved forest, with oak deciduous forest as zonal vegetation. V-1-2nt, V-1-1ns, V-1-5nr and the north V-1-4sr belongs to north-subtropical mixed evergreen and deciduous broad-leaved forest, the zonal vegetation of which changes from deciduous broad-leaved forest with evergreen shrubs to mixed evergreen and deciduous broad-leaved forest. The south of V-1-4sr belongs to the mid-subtropical evergreen broad-leaved forest, with evergreen broad-leaved forest as zonal vegetation. 2) Timber forests, shelter forests and economic forests are predominant in the study area. However, the proportion of each forest category and tree species varies among different soil and water conservation regions. From the north to the south, the dominant tree species of timber forests and shelter forests change from Populus spp. and Platycladus orientalis to Pinus massoniana, Cunninghamia lanceolata, Cinnamomum camphora and broad-leaved forest, while the dominant tree species of economic forests change from Malus pumila, Pyrus spp., Castanea mollissima and Ginkgo biloba to Camellia sinensis, Amygdalus perisica and Citrus reticulata. 3) Considering the spatial heterogeneity of forest category and tree species among the third level of soil and water conservation regions, 96 monitoring sites were sampled from 17 sampling area. According to field survey, 49 vegetation coverage monitoring sites were located, which including the dominant forest categories and tree species in each soil and water conservation region.

Conclusions Vegetation category, forest category and tree species exhibit significant spatial heterogeneity in Jiangsu Province. The proposed layout of monitoring sites provides a technical support for vegetation coverage monitoring in Jiangsu province. It also provides useful reference for the layout of vegetation coverage monitoring sites in other similar regions.