Soil labile organic carbon impacts C:N:P stoichiometry in urban park green spaces depending on vegetation types and time after planting

Abstract

Soil nutrient stoichiometry, expressed as the ratios of carbon (C), nitrogen (N), phosphorus (P) in soil, determines the biogeochemical processes of elements in terrestrial ecosystems. Soil labile organic carbon (LOC) is that active component of SOC characterized by rapid turnover times, which links soil organic carbon (SOC) sequestration to C emission. Surprisingly, however, the linkage between soil C:N:P stoichiometry and soil LOC components remains unknown, especially in urban park green spaces. To fill this gap, the soils of dominant vegetation (deciduous forest, evergreen forest and lawn) at three different time after planting (5, 10, and 15 years) in three urban parks of Chengdu megacity were collected, and their soil C:N:P ratios and LOC components were analyzed. Results showed that soil C:N:P ratios were significantly influenced by the elapsed time since vegetation planting. The contents of LOC components (dissolved organic carbon (DOC), microbial biomass carbon (MBC), readily oxidizable carbon (ROC)) all decreased with the more time after planting and they were higher in the soils of deciduous and evergreen forests than lawn vegetation. Soil C:N:P ratios were significantly correlated with LOC components instead of soil TOC, suggesting a sensitive response of soil C:N:P stoichiometry to the dynamics of soil LOC components. Overall, different vegetation types and the time of respective plant-soil interactions regulate the dynamics of soil LOC components, thereby promoting the heterogeneity of soil C:N:P stoichiometry.