Vegetation restoration potential and land use change in different geomorphological areas of the Loess Plateau

Abstract: "Grain for Green" program has been implemented in the Loess Plateau of China since 1999, in order to control excessive soil erosion and sediment production. There is a profound impact on the vegetation cover and land use structure in recent years. It is a high demand to analyze the potential of vegetation restoration, plantation suitability areas, and land use change for regional ecosystem restoration planning and ecological protection. Taking the Beiluo River Basin as an example, this work aims to clarify the potential of vegetation restoration, vegetation suitability area, and land use change in various geomorphological areas using the dataset of climate, geography, vegetation cover, and land use. The "similar habitat" was also introduced for the statistical and geographical spatial analysis. Results showed that: 1) The spatial distribution of vegetation cover varied significantly in the study area in 2020. The vegetation cover of the earth-rock mountain area was the highest at 88.8%, followed by the gully area at 84.1%, and the terrace plain area and hilly-gully area at 68.9% and 61.9%, respectively. A spatial distribution pattern of vegetation restoration potential was obtained with the "high in the northwest and low in the southeast", particularly in the hilly-gully area in the upper reaches. The maximum recoverable vegetation cover of the hilly-gully area was 71.1%, where still 9.2% potential for the vegetation cover and the vegetation of 36.4% of the area continued to improve in the next 20-30 years. By contrast, the area with the vegetation to be improved accounted for about 11.5% of the earth-rock mountain area. The maximum recovery potential was achieved in the vegetation cover in the gully and terrace plain areas after 20 years of restoration. Therefore, there was no room to improve in the future. 2) The current land use types were dominated by cropland, forestland and grassland. The land use predictions showed that the land use change was mainly concentrated in the hilly-gully area in the next 20-30 years. The cropland decreased by 47.4% in the hilly-gully area, compared with 2020. The forestland and grassland increased by 0.7% and 15.8%, respectively. Since the cropland decreased by 23.0%, the forestland and grassland increased by 0.2% and 36.0%, respectively, in the earth-rock mountain area. Conversely, there was only a slight change in the future land use in the gully and terrace plain area. 3) The scenarios simulation was conducted to determine the plantation's suitability using the principle of "Matching Tree Species with Site". The suitable planting area in the gully and terrace plain area was 279.16 and 233.73 km2, respectively. A large area of returned cropland in the hilly-gully area was suitable for the natural restoration. There was relatively sporadic suitability for the planting area in the hilly-gully and earth-rock mountain areas. It implied that the hilly-gully area was the key area for future ecological restoration, which was the hotspot for ecological protection and high-quality development in the Yellow River Basin. Considering the limited rainfall and water carrying capacity, the ecological measures of "adaptation to local conditions" were proposed to avoid soil drying for future vegetation restoration in the Loess Plateau.