Changes in soil phosphorus fractions under different land uses in desert grasslands in northwestern China

Humans influence desert ecosystem structure and function by transforming native vegetation into agricultural and non‐agricultural land. However, how different land uses in desert grasslands affect soil phosphorus (P) fractions with varying lability by creating distinct soil physicochemical and microbial properties remains poorly understood. To address this question, a field study was conducted in the arid region of northwestern China, where sites were selected for having an area containing natural desert grassland and three adjacent differently managed land uses converted from desert grassland: 28‐year‐old rainfed shrub (Haloxylon ammodendron) plantation, 35‐year‐old irrigated tree (Populus gansuensis) plantation, and 33‐ to 40‐year‐old irrigated and fertilized croplands. We collected data from four land‐use types for concentrations of soil inorganic and organic P (Pi and Po) fractions of decreasing lability (labile P: resin‐ and NaHCO3‐extractable P; moderately labile P: NaOH‐extractable P; recalcitrant P: HCl‐extractable P and residual P) and edaphic variables as predictors. The relative contributions of individual predictors to variation in P fractions were evaluated using a boosted regression tree analysis. We found significant increases in (1) all P fractions in croplands (77%–418%), with the largest increase in resin‐P; (2) all P fractions except resin‐P in tree plantations (52%–367%), with the largest increase in labile Po; and (3) NaHCO3‐P and HCl‐Pi in shrub plantations (14%–134%), with the largest increase in labile Pi, compared with natural desert grasslands. Edaphic properties dominantly controlled the changes of different P fractions, explaining 51%–93% of the variation in P fractions, but the dominant influential factors differed across P fractions. We conclude that different land uses in desert grassland soil resulted in significant differences in the fractional composition and availability of soil P by affecting edaphic properties differently, informing that soil P cycling can be regulated by altering land‐use types and management levels. Highlights Assessing the impact of different land uses in desert grasslands on soil P fractions. Different land‐use types showed distinct patterns of soil P dynamics and availability. Soil P responses to land‐use changes were mainly mediated by edaphic properties. The importance of edaphic factors in regulating P dynamics differed among P fractions. Soil P cycling can be regulated by altering land‐use type