Biological soil crusts (BSCs) are often referred to as the “living skin” of arid regions worldwide. Yet, the combined impact of BSCs on soil carbon (C), nitrogen (N), phosphorus (P), and enzyme activities remains not fully understood. This study identified, screened and reviewed 71 out of 2856 literature sources to assess the responses of soil C, N, P and enzyme activity to BSCs through a meta-analysis. The results indicated that BSC presence significantly increased soil C, N, P and soil enzyme activity, and this increasing effect was significantly influenced by the types of BSCs. Results from the overall effect showed that soil organic carbon (SOC), total nitrogen (TN), available nitrogen (AN), total phosphorus (TP), and available phosphorus (AP) increased by 107.88%, 84.52%, 45.43%, 27.46%, and 54.71%, respectively, and four soil enzyme activities (Alkaline Phosphatase, Cellulase, Sucrase, and Urease) increased by 93.65–229.27%. The highest increases in SOC, TN and AN content occurred in the soil covered with lichen crusts and moss crusts, and significant increases in Alkaline Phosphatase and Cellulase were observed in the soil covered with moss crusts and mixed crusts, suggesting that moss crusts can synergistically enhance soil C and N pool and enzyme activity. Additionally, variations in soil C, N, P content, and enzyme activity were observed under different environmental settings, with more pronounced improvements seen in coarse and medium-textured soils compared to fine-textured soils, particularly at a depth of 5 cm from the soil surface. BSCs in desert ecosystems showed more significant increases in SOC, TN, AN, and Alkaline Phosphatase compared to forest and grassland ecosystems. Specifically, BSCs at low altitude (≤500 m) with an annual average rainfall of 0–400 mm and an annual average temperature ≤ 10 °C were the most conducive to improving soil C, N, and P levels. Our results highlight the role of BSCs and their type in increasing soil C, N, P and enzyme activities, with these effects significantly impacted by soil texture, ecosystem type, and climatic conditions. The implications of these findings are crucial for soil enhancement, ecosystem revitalization, windbreak, and sand stabilization efforts in the drylands of China.

Radionuclide tracer technology, as a state-of-the-art tool for quantifying and monitoring soil erosion processes, has attracted much attention in global sustainable land management research in recent years. However, existing studies are fragmented in methodological applications, lack systematic knowledge integration and interdisciplinary perspectives, and lack global research trends and dynamic evolution of key themes. This study integrates Bibliometrix, VOSviewer, and CiteSpace to conduct bibliometric and knowledge mapping analysis of 1692 documents (2000–2023) in the Web of Science Core Collection, focusing on the overall developmental trends, thematic evolution, and progress of convergence and innovation. The main findings of the study are as follows: (1) China, the United States, and the United Kingdom are in a “three-legged race” at the national level, with China focusing on technological application innovation, the United States on theoretical breakthroughs, and the United Kingdom contributing significantly to methodological research; (2) “soil erosion” and “¹³⁷Cs” continue to be the core themes, while “climate change” and “human impact” on soil erosion and its reflection in radionuclide tracing became the focus of attention; and (3) multi-scale radionuclide tracing (watershed, slope), multi-method synergy (radionuclide tracing combined with RS, GIS, AI), and the integration of advanced measurement and control technologies (PGS, ARS) have become cutting-edge trends in soil erosion monitoring and control. This study provides three prospective research directions—the construction of a global soil erosion database, the policy transformation mechanism of the SDG interface, and the iterative optimization of multi-radionuclide tracer technology, which will provide scientific guidance for the realization of the sustainable management of soil erosion and the goal of zero growth of land degradation globally.

        Fallout radionuclides such as 137Cs and 210Pbex have been successfully used to quantify rates of soil and sediment redistribution in many areas of the world in recent years. However, little attention has been given to the assessment of soil erosion rate in the abandoned farmland using the 137Cs and 210Pbex tracer techniques. The artificial derived 137Cs is still basically uniformly distributed in the soil after farmland abandonment, while the depth distribution of the natural derived 210Pbex in the soil of the abandoned farmland will be continuously changed by the combined effects of its continuous atmospheric deposition, infiltration and radioactive decay within 100 years after farmland abandonment. At present, there is no model to represent this change of 210Pbex distribution after the farmland abandonment, and the existing steady-state 210Pbex model is not suitable for soil erosion assessment in the abandoned farmland. It is necessary to develop a model on the changes of 210Pbex depth distribution in the soil of abandoned farmland. In this study, the redistribution process of 210Pbex in the soil after farmland abandonment was decomposed and theoretically deduced on basis of analyzing the physical mechanisms of 210Pbex infiltration and decay in soil. The expression of 210Pbex decay in the plough layer on the initial abandoned farmland and the expression of infiltration of the new fallout 210Pbex in soil after farmland abandonment were incorporated to develop the model on changes in 210Pbex depth distribution for the abandoned farmland. The parameters such as the plow depth and the diffusion coefficient required for the model were obtained according to the measured 137Cs and 210Pbex depth distributions from the typical abandoned farmlands in Sichuan Province, southwest China. The result showed that the modeled curves of 210Pbex depth distribution in the farmland abandoned for 19, 15 and 8 years matched each other with the measured curves. In addition, the Nash-Sutcliffe efficiency coefficient (ENS) test showed that the ENS of the three abandoned farmland were 0.975, 0.961 and 0.889, respectively, indicating the modeled results are reliable. The present study has an important theoretical significance for the development of the models for calculating the soil erosion amount from 210Pbex measurements on the abandoned farmland, and further provides an effective method for the evaluation of the soil erosion response driven by abandonment.