Climate and soil properties shape latitudinal patterns of soil extracellular enzyme activity and stoichiometry: Evidence from Southwest China

Determining the patterns and environmental regulatory conditions of soil extracellular enzyme activity (EEA) across latitudinal gradients is crucial for understanding microbial biogeography and contributes to predicting how soil biogeochemical cycles respond to environmental changes. However, knowledge of the latitudinal patterns in soil EEA and stoichiometry, as well as their drivers, remains limited. In this study, we collected soil samples from 102 xerophytic shrublands along the 23.2-32.3 degrees N latitudinal range in arid valleys of Southwest China at depths of 0-10, 10-20, and 20-30 cm. We determined the activities and major environmental factors of soil EEA involved in C cycling (beta-1,4-glucosidase [BG]), P cycling (acid phosphatase [AP]), and N cycling (leucine aminopeptidase [LAP] and beta-1,4-N-acetylglucosaminidase [NAG]). The activities of BG, AP, and NAG increased with increasing latitude, except for the activity of BG in the 0-10 cm stratum, which did not change significantly. With increasing latitude, LAP activity and enzymatic N:P and C:P ratios decreased and subsequently increased; enzymatic C:N ratios exhibited the opposite trend. Redundancy analysis indicated that mean annual temperature (MAT), soil pH, and total N content contributed the most to altering soil EEA, irrespective of the soil depth. Latitudinal variations in soil EEA stoichiometry at 0-10 cm depth depended primarily on MAT, aridity index, and soil C:P ratio, and those at 10-20 and 20-30 cm depth were tightly linked to MAT, mean annual precipitation, and soil pH. Overall, this study determined the latitudinal patterns of soil EEA and stoichiometry and emphasized that enzyme allocation patterns in the arid valleys of Southwest China were influenced by climate and soil properties.