Potentially toxic elements (PTEs) in Chinese agricultural soils, including those in some heritage protection zones, are serious and threaten food safety. Many scientists think that these PTEs may come from parent rock. Hence, at a karst rice-growing agricultural heritage area, Babao town, Guangnan County, Yunnan Province, China, the concentrations of eight PTEs (As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn) were determined in 148 surface soil, 25 rock, and 52 rice grain samples. A principal component analysis (PCA) and hierarchical cluster analysis were used to divide the surface soil into groups, and inverse distance weighting (IDW) was used to analyze the spatial distribution of PTEs. Soil pollution was assessed with the geoaccumulation index (Igeo). The results show that Cd, Hg, Zn, and Cr were polluting the soil (average Igeo > 0). The highest concentration of PTEs was distributed in the southwest of Babao town in the carbonate rock area, which had the highest pH and soil total organic carbon (Corg), Mn, and TFe₂O₃ contents. PCA biplots of soil samples showed that the carbonate rock area was associated with the most species of PTEs in the study area including Pb, Cd, Hg, As, and Zn. The clastic rock area was associated with Cu and Ni, and the lime and cement plants were associated with CaO, pH, Corg, TC, and aggravated PTE pollution around factories. In high-level PTE areas, rice was planted. Two out of 52 rice grain samples contained Cd and 4 out of 52 rice grain samples had Cr concentrations above the Chinese food safety standard pollutant limit (Cd 0.2 mg/kg; Cr 1 mg/kg). Therefore, the PTEs from parent rocks are already threatening rice safety. The government should therefore plan rice cultivation areas accordingly.

Serious soil and water loss affects the economy and the living quality of the population in faulted basins. Since 2002, China has carried out large-scale ecological restoration projects in karst areas. However, the karst faulted basins have experienced complex climatic changes, which makes it difficult to assess the ecological restoration effects quantitatively. Using the improved Budyko model, basin factor (n) and sediment content factor (C) were divided into climate influence and ecological restoration influence by second-order approximation, and the change ratio of climate influence and ecological restoration on sediment yield and loss was quantitatively calculated in the representative basin of the Nandong Underground River System (NURS). This was carried out in order to effectively distinguish the effects of climate change and ecological restoration on runoff and sediment change in the NURS. Furthermore, this study sought to understand the mechanism of runoff and sediment change and to evaluate the ecological restoration in the faulted basin to provide a scientific basis for the next stage of soil and water conservation policy formulation. The results showed that: (1) Using Pettitt to test the abrupt change of water and sediment in the NURS from 1987 to 2018, we found that 2002 was the abrupt change year of water and sediment in the basin. Before and after the mutation, the runoff and sediment yield decreased significantly, with the change rates of −15.5% and −51.8%, respectively. The decrease in precipitation and the increase in E₀ were not significant, which were −4.5% and 1.4% respectively. (2) By calculating the correlation coefficient and the double logarithm function, it was found that the maximum temperature is the main climatic factor affecting the underlying surface factor n, and precipitation is the main climatic factor affecting the sediment concentration c. (3) Climate change reduced runoff by 77.6%. Ecological restoration has reduced sediment by 51.3 percent. The sensitivity of runoff to maximum temperature was 3.61. The sensitivity of grain yield to precipitation and NDVI was 5.37 and 3.26, respectively. The results show that climate is the main factor of runoff reduction, and ecological restoration is the main factor of sediment reduction. Ecological restoration has greatly reduced sediment production, and ecological engineering has made remarkable progress. However, the reduction of runoff caused by climate change should be paid more attention. The results of these studies will help to better formulate land use management policies for soil and water conservation.

The ongoing modification of precipitation regime highlights the necessity to further investigate underlying vegetation processes. To figure out the key precipitation characteristics that largely affected the biomass and species richness of different plant functional groups in the semiarid sandy land, we compared the 15-year (from 2005 to 2019) variation in the aboveground biomass (AGB), precipitation use efficiency (PUE) and species richness of two typical biotopes (fixed dune and sandy grassland) in Horqin Sandy Land, a semiarid sandy land in northeast China. Results showed that the sandy grassland had higher AGB and PUE, lower species richness than the fixed dune; the annuals contributed 60.16% of the AGB and 60.32% of the species richness in sandy grassland, while contributed 53.40% and 75.77% in fixed dune, respectively; the AGB and species richness in the fixed dune had medium positive correlation with annual precipitation, while that in the sandy grassland had medium positive correlation with the total amount of specific rainfall events in the growing season (e.g. cumulative precipitation of 10–40 mm rain events and number of ≥ 10 mm rain event). There was no significant correlations were detected between PUE and annual precipitation, and weakly positive correlations were detected between PUE and amount and number of medium rainfall events in growing season. Our results suggested that the biomes dominated by annual plants were more responsive to the variability of growing season rainfall pattern rather than annual precipitation. In semiarid sandy grassland communities, the frequent medium rainfall events (5–50 mm) have significant role on the biomass, and the high species richness is likely to depend on the number of larger ones (≥ 10 mm). The AGB and species richness of grassland communities in semi-arid sandy land was the result of the combined effect of amount size, number and interval of rain event.

Karst areas are one of the world's major ecological fragile zones, are prone to influences from human activities and climate change. Although the vegetation cover in karst area of southwest China increased significantly in recent decades, there are obvious spatial differences in vegetation greening. To better elevate the relative importance of the anthropogenic factors and climatic factors to the vegetation greening, and explore the factors leading to the spatial heterogeneity of vegetation greening in karst desertification area where vegetation was seriously degraded, linear regression analysis, correlation analysis and residual analysis were used to evaluate the contribution of anthropic factors and climatic factors to the growth of normalized difference vegetation index (NDVI) from 1998 to 2020, and revealed the correlations between natural factors (proportion of karst areas, elevation and landscape pattern) anthropic factors (change in land use, population density and gross domestic product), climatic factors (annual temperature and annual precipitation) and the spatial-temporal variation of county NDVI in the paper. The results showed that (1) generally, the NDVI value increased by 23.59% from 1998 to 2020 in total area, and the anthropic factor dominated the process of vegetation greening (87.02%). The rapid increase of vegetation coverage occurred from 2011 to 2020, which was jointly promoted by the urbanization, economic development, increasing mean temperature and precipitation, and climate change were the main contributor (67.65%). (2) there were significant spatial heterogeneity in the NDVI, which was mainly caused by the site conditions (e.g. the proportion of karst area, landscapes pattern, mean annual temperature and precipitation) and anthropic factors (e.g. the proportion of construction land, population density and gross domestic product); the county NDVI value was negatively correlated with the proportion of karst area, cropland, grassland and construction land, population density, and gross domestic product, while it was positively correlated with the proportion of woodland, mean annual temperature and mean annual precipitation. (3) Generally, vegetation greening was faster in regions with warm and humid climate or more forestland, and lower in regions with higher average elevation and economic growth. Nevertheless, the effects of environmental factors on the vegetation greening rate varied in the different periods. The land cover pattern, population density, GDP in 2000, and the rate of urbanization and economic growth influenced vegetation growth from 2000 to 2010, while the impact of mean annual temperature and mean annual precipitation became more pronounced since 2010. The results of this study contributed to understand the importance of anthropic factors and climatic factors that affect veg-etation greening in karst rocky desertification areas in different periods, which provided deci-sion-making basis for land managers.