Abstract
Spontaneous vegetation succession after agricultural abandonment is a general phenomenon in many areas of the world. As important indicators of nutrient status and biogeochemical cycling in ecosystems, the stoichiometry of key elements such as carbon (C), nitrogen (N) and phosphorous (P) in soil and microbial biomass, and their responses to vegetation recolonization and succession after agricultural abandonment remain poorly understood. Here, based on a space-for-time substitution approach, surface soil samples (0–15 cm) were collected from four vegetation types, e.g., tussock grassland, shrubland, secondary forest, and primary forest, which represent four successional stages across this region. All samples were examined C, N and P concentrations and their ratios in soil and microbial biomass. The results showed that soil organic C and total N content increased synchronously but total soil P did not remarkably change along a progressive vegetation succession. Consequently, soil C:P and N:P ratios increased while C:N ratio stayed almost unchanged during vegetation succession. Soil microbial biomass C (SMBC) and microbial biomass N (SMBN) concentrations elevated while SMBP did not significantly change during vegetation succession. Unlike the soil C:N:P stoichiometry, however, microbial C:N and C:P ratios were significantly or marginally significantly greater in grassland than in the other three successional stages, while microbial N:P did not significantly vary across the four successional stages. Overall, the present study demonstrated that soil and microbial stoichiometry responded differently to secondary vegetation succession in a karst region of subtropical China.
Highlights
Carbon (C), Nitrogen (N) and Phosphorus (P) are three fundamental elements that constitute living organisms, and the biogeochemical cycles of C, N and P are tightly coupled
C:N:P stoichiometry is generally used as a powerful indicator of biogeochemical cycles and nutrient status in ecosystems [2,3]
No significant variation was observed in soil C:N ratio under different vegetation types (Figure 2D)
Summary
Carbon (C), Nitrogen (N) and Phosphorus (P) are three fundamental elements that constitute living organisms, and the biogeochemical cycles of C, N and P are tightly coupled. Since Redfield reported a relatively consistent atomic ratio of C:N:P (106:16:1) in both planktonic biomass and marine waters [1], ecological stoichiometry, which focuses on the balance of multiple chemical elements in ecological interactions, is of growing interest worldwide. C:N:P stoichiometry is generally used as a powerful indicator of biogeochemical cycles and nutrient status in ecosystems [2,3]. Shifts in the C:N:P stoichiometry may exert strong influences on ecosystem structures, processes, and functioning [4,5,6,7]. The stoichiometry of C, N, and P in the soil could greatly determine aboveground vegetation
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