Ecoenzymatic stoichiometry and nutrient limitation under a natural secondary succession of vegetation on the Loess Plateau, China

Soil ecoenzymatic stoichiometry reflects the nutrient flow of ecosystems. While knowledge exists on how the secondary succession of plants affects soil physicochemical properties and soil ecoenzymatic activity, less is known about how soil ecoenzymatics change during this process. We investigated five typical stages of the entire succession process of vegetation on the Loess Plateau, China. These stages included: (1) farmland stage (0 years), (2) grassland stage (30 years), (3) shrub land stage (60 years), (4) the pioneer forest stage (100 years), (5) the climax community stage (160 years). Soil ecoenzymatic activity, microbial biomass, and soil physicochemical properties were measured. Our research showed secondary succession significantly changed soil enzyme activity, and the metabolic activity of soil microorganisms significantly declines as secondary succession progresses. N limitation in the soil microbial community was weak initially and then gained strength. P nutrient limitation was strong initially, and then weakened. Soil ecoenzymatic C : N : P acquisition ratios deviated from 1 : 1 : 1. Thus, secondary succession on the Loess Plateau is nutrient dependent, but not homeostatic. Soil physicochemical properties and plants were important factors for soil enzyme activities. In addition, soil available nutrients were better than soil total nutrients to reveal changes in soil ecoenzymatic activities and stoichiometry. This study demonstrated the regularity of soil nutrient cycling during the secondary succession of vegetation, providing new insights on the mechanisms of nutrient flow. © 2020 John Wiley & Sons, Ltd.