Reactive oxygen species (ROS) are a class of molecules or free radicals with strong oxidizing properties. They have attracted increasing attention in soil research in recent years because of their perceived importance in many soil biochemical processes. Previous reviews of ROS in soil mainly focused on their impacts on carbon emissions and organic pollutant remediation, with few descriptions of the mechanisms responsible for ROS generation, and a comprehensive understanding of their environmental effects is still lacking. Therefore, the present review provides details on the sources and underlying generation mechanisms of ROS in soil. These mechanisms include inputs via atmospheric deposition, metal–mineral reactions, root exudation, microbial metabolism, enzymatic reactions and various organic matter transformations. In contrast to previous reviews, we also discuss mutual conversion between different types of ROS in soil. The impacts of ROS on the soil environment are further explored, such as element cycling, pollutant degradation, and the growth and reproduction of plants and microorganisms, in order to provide a systematic understanding of the various processes involving ROS in soil, thereby guiding better soil management decisions. Finally, we highlight future research trends, suggesting that the advancement of in situ detection methods is crucial for establishing the precise contribution of abiotic ROS processes to global soil carbon and nutrient models.

Shrub encroachment in alpine grasslands alters soil biogeochemical processes, but reported soil responses remain inconsistent and conflicting among studies. We performed a systematic review and meta-analysis to evaluate ten physical and chemical alongside biological soil properties. Evaluated indicators covered soil water content (SWC) and bulk density (BD) alongside soil organic carbon (SOC) and total nitrogen (TN). They also included ammonium (NH₄⁺-N) and total phosphorus (TP) and pH alongside microbial biomass carbon (MBC) and nitrogen (MBN) and phosphorus (MBP). In total, 66 peer-reviewed articles provided 175 paired observations across four continental alpine regions, with most studies conducted in High Mountain Asia. Most compiled studies evaluated topsoil chemical properties, while non-nitrogen-fixing shrubs dominated the dataset. Shrub encroachment significantly stimulated MBC (+7.59%) and MBN (+5.44%) across both functional groups. TN increased significantly (+2.08%) driven entirely by nitrogen-fixing shrubs (+7.57%). Nitrogen-fixing shrubs also induced rhizosphere acidification (−1.87%) and increased MBP (+14.41%). Non-nitrogen-fixing shrubs significantly reduced BD (−5.67%), while bulk SOC (+0.15%) and TP (−0.31%) showed no pooled change. SOC responses diverged sharply at the genus level, increasing under Dasiphora (+6.58%) but declining under Salix (−6.88%) and Vaccinium (−11.62%). Soil sampling depth and shrub genus identity exerted primary controls on soil carbon and nitrogen dynamics. Current evidence concentrates heavily on Qinghai–Tibetan Plateau topsoils, leaving critical geographic and subsoil data gaps across global cold alpine biomes. Given functional divergence and depth stratification, sustainable alpine management must adopt shrub regulation differentiated by functional traits, linking microscale microbial processes with whole ecosystem carbon and nitrogen cycling.