Abstract: We investigated soil physicochemical properties and the activities of six enzymes related to carbon, nitrogen, and phosphorus cycling under three precipitation treatments (≤350, 350-450, and ≥450 mm) in Pinus sylvestris var. mongolica plantations in the eastern part of the Northern Sand Prevention Belt. We further analyzed soil microbial nutrient carbon, nitrogen, phosphorus limitation characteristics in rhizosphere. The results showed that compared with that under precipitation ≤350 mm, soil water content, organic carbon and total nitrogen contents under precipitation ≥450 mm increased by 38.7%, 64.3% and 58.9%, respectively, while soil pH and total phosphorus content decreased by 23.4% and 40.3%. Activities of β-1,4-glucosidase, β-xylosidase, L-leucine amino-peptidase, and alkaline phosphatase, as well as soil microbial biomass carbon, nitrogen, and phosphorus peaked under the 350-450 mm precipitation condition. The vector model indicated that rhizosphere soil microorganisms were generally co-limited by soil carbon (C) and nitrogen (N) availability. With increasing precipitation, the pattern of microbial nutrient limitation gradually shifted from strong N limitation to the weak limitation by C and N, and eventually to the strong C limitation. Redundancy analysis showed that soil microbial biomass nitrogen was the primary factor influencing enzyme activities and stoichiometric ratios at ≤350 mm precipitation (53.5%), while soil organic carbon became the dominant factor at ≥450 mm precipitation (72.7%). Our results highlighted the variations and driving factors of microbial carbon, nitrogen, phosphorus nutrient limitations in the rhizosphere of P. sylvestris plantations across different precipitations, providing a scientific basis for nutrient regulation in P. sylvestris plantations.

Key words: precipitation, Pinus sylvestris var. mongolica, soil enzyme activity, enzymatic stoichiometry, microbial nutrient limitation