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• Determine soil zinc cycle using isotopic tracing from karst area. • Zinc behaviors strongly controlled by rock weathering and leaching processes. • Cultivation limits δ66Zn fractionation, grazing induces heavier δ66Zn compositions. Stable isotopes are increasingly employed to identify anthropogenic disturbances and geogenic processes of zinc (Zn) in terrestrial ecosystems. To reveal how land use affects the transformation of soil Zn, profile samples were collected from abandoned cropland (AC), grazing shrubland (GS), and natural land (secondary forest land, SF) in a typical karst area, and analyzed the Zn content and isotopic composition. Results exhibited that soil Zn contents in forest (SF: 72.50 ∼ 131.20 mg/kg) were more variable than those in agricultural lands (AC: 74.53 ∼ 112.20 mg/kg; GS: 48.26 ∼ 82.57 mg/kg). Rock weathering was the main contributor to soil Zn in each profile. Differences among profiles arose from partially assimilative Zn returning to the forest through plant debris, whereas leaching processes coupled with the consumption of crop production and livestock led to Zn loss. The δ66Zn varied in the largest range in SF (−0.26 ‰ to 0.04 ‰), and the extremums were both in the upper soil (0 to 80 cm). After the decomposition of plant debris, vegetation preferentially assimilated lighter δ66Zn, while retaining heavier δ66Zn in the surface soil. Moreover, the soil solution also had a lighter δ66Zn composition that leached downward. The narrowest range of δ66Zn composition was in AC (−0.14 ‰ to −0.02 ‰). The assimilation of crops exhausted the lighter δ66Zn fraction during cultivation, and the heavier δ66Zn fraction continued to be lost by leaching after stopping tillage. The δ66Zn composition ranged from −0.18 ‰ to 0.00 ‰ and decreased with depth in the GS. Animal excrement supplied unintentionally heavier δ66Zn compositions during grazing and obviously disturbed soil Zn behavior under the effects of vertical leaching. Both the content and isotopic composition showed that soil Zn dynamics were highly sensitive to agricultural activities. This study reveals a potential feedback mechanism for soil Zn behavior during agricultural disturbances, which is beneficial for optimizing land management in karst areas. [ABSTRACT FROM AUTHOR]

[Display omitted] • Rainfall and temperature both had a significant effect on forest land. • Annual rainfall and grassland area contributed the most to soil conservation. • Land use had a greater direct impact on soil conservation than climate factors. • Land use, rainfall, and temperature had threshold effects on soil conservation. In the Loess Plateau, enhancing the function of soil conservation (SC) is essential for maintaining ecological sustainability. Land use (LU), rainfall, and temperature might all have a big influence on SC. In this study, we applied the InVEST model to assess the SC of a typical city, Yan'an, in 1990, 2000, 2010, and 2020. Effects of LU, rainfall, and temperature changes on SC were examined using correlation analysis, redundancy analysis (RDA), regression analysis, and frequency ratio analysis. The findings indicated that farmland (FC), forest land (FL), and grassland (GL) were Yan'an City's main LU types. The expansion of FL and GL areas has come at the expense of the FC areas, partly due to the "Grain for Green" Project, and this change has accelerated considerably since 2000. The total amount of SC in 1990, 2000, 2010, and 2020 generally showed a decreasing and then increasing trend, which was 0.96, 0.87, 1.22, and 1.39 billion tons respectively. In the research region, temperature, rainfall, and LU changes occurred all at once. The FL region was quite consistent with the geographical distribution of areas with low temperatures and heavy rainfall. The results of correlation analysis and RDA indicated that GL area and annual rainfall (PY) were the main causes of SC (p < 0.01). A strong connection (r = 0.63, p < 0.01) was also seen between the daily temperature range (ΔT) and SC. Increased LU-type area, rainfall, and temperature improved SC with a threshold range. Calculated by regression analysis, it recommended the FL ≤ 11040 km2, GL ≥ 14720 km2, and FC ≤ 7360 km2 in Yan'an City. Rainfall and temperature showed no significant pattern and were difficult to regulate by human intervention. The improvement of SC should focus on adjusting the LU structure under the existing ecological planning. Accepting some degrees of uncertainty, our findings provide insights into how possible LU, rainfall, and temperature will affect SC. It's crucial both for future regional management and ecological sustainability development. [ABSTRACT FROM AUTHOR]

• Classification of flood events into typhoon and non-typhoon rainstorm floods. • Key parameters in HEC-HMS model were systematically different for the two types of floods. • Impact of land use change on typhoon floods was smaller than that of non-typhoon floods. • Frequency distribution of the mixture flood series with the effect of land use change. There are two major types of rainstorms in the Asia-Pacific region –typhoon induced rainstorm and non-typhoon rainstorm. This study investigated and separated the different flood responses to these two types of rainstorms, based on a scheme that combined the classification of typhoon and non-typhoon rainstorm floods, the simulation from a distributed hydrological model, and a method to forward restore the impact of land use change on flood frequency analysis. For flood events in a typical basin on the southeast coast of China, the flood characteristics in response to typhoon and non-typhoon rainstorms were significantly different in three aspects: (1) The key parameters in the HEC-HMS model were systematically different. The initial loss and wave velocity of the model were apparently larger for the typhoon rainstorm flood than for the non-typhoon rainstorm flood. (2) The impacts of land use change were different, with smaller effect on typhoon induced floods than on non-typhoon floods under the same magnitude of flood peak flow. (3) Classification of two types of floods resulted in more reasonable frequency analysis affected with the land use change because the annual maximum flood series is the mixture of typhoon and non-typhoon rainstorms. Frequency analysis for the forward-restored mixture flood series showed that the land use change with the decrease in the area of forest land and the increase of garden and construction land resulted in the increase of the mean maximum flow from 2266.6 to 2510.19 m3/s, but the values of coefficient of variation were slightly altered, the ratio of skewness coefficient to variation coefficient were unchanged. The results provide new ideas and methods for a deeper understanding of the impact of land use change on flooding in typhoon and non-typhoon co-action regions. [ABSTRACT FROM AUTHOR]