Abstract
• High-severity fire left significant legacy effects on multiple soil elements. • The average availability and stability of soil elements decreased after fire. • The associations amongst soil elements tended to be uncoupled at the SB site. • Soil CEC, ACP, CP and Aggr directly mediated soil multi-element coupling. • The nature of biogeochemical decoupling was attributed to fire and time. High-severity wildfires may lead to significant impacts on biogeochemical cycling both by burning biomass and by fire legacies. However, the legacy effects of wildfires on multiple soil element cycles across temporal trajectories have rarely been discussed. Here, we evaluated the availability and stability of seven essential soil elements and their stoichiometric ratios, as well as the coupling of multiple and individual elements, over more than two years in a half-mature, severely burnt (SB) artificial Pinus tabuliformis Carr. forest in North China (Beijing) in comparison with the unburnt (UB) control. Despite element concentrations jumped up and down remarkably during the first few months, results showed that the average availability and stability of all elements in soils of the SB site were lower than those of the UB site and legacy effects of fire were consistently significant on available nitrogen (N), phosphorus (P) and sodium. Temporal trajectories (months to years) varied amongst elements, and organic carbon (C) and N depleted more than other elements did. High levels (i.e. above the null model threshold) of multi-element coupling in soils of the UB site were maintained during our monitoring periods. By contrast, a reduction in the degree of element coupling was detected over time in soils of the SB site, which was concomitant with the core role of C and the great variability of P. Fire- and time-induced shifts in cation exchange capacity, acid phosphatase activity, capillary porosity and aggregate fraction dominated the uncoupling of multiple soil elements, implying the critical contributions of fire legacy effects and temporal variations. These responses have important implications for the consideration of additional long-term studies because such biogeochemical decoupling of elements may have unpredicted consequences under global change scenarios. Meanwhile, this work is helpful to predict the direction of ecosystem succession and to provide scientific evidence for management practices.
Published Version
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