Response of ecological stoichiometry and stoichiometric homeostasis in the plant-litter-soil system to re-vegetation type in arid mining subsidence areas

Mining restoration is a key in ecological sustainable development. Ecological stoichiometry and homeostasis in the plant-litter-soil system remain largely unknown but are vital for developing guidelines for vegetation restoration in mining subsidence areas in arid northwest China. Six re-vegetation types comprising stands of Amorpha fruticosa, Hippophae rhamnoides, Xanthoceras sorbifolium, Cerasus humilis, Cerasus szechuanica and Pinus sylvestris were selected for study. We investigated changes in the contents and stoichiometry of C, N and P in roots, stems, leaves, litter and soil in order to understand stoichiometric homeostasis and the factors driving nutrient cycling. The stoichiometry of the plant-soil system varied markedly with different re-vegetation types. The coupling of plant and soil N:P ratios indicates that the concentrations of C, N and P are usually equilibrated. Leave N:P ratios in all re-vegetation types studies indicate that plant growth was N-limited. 1/H only in H. rhamnoides and A. fruticosa (nitrogen-fixing plants) was simultaneously categorized as 'homeostatic' and this might mitigate the N-limitation. Soil easily-extractable glomalin, hyphal density and available phosphorus were key factors shifting the ecological stoichiometry. The study demonstrates that nitrogen-fixing re-vegetation species can promote stoichiometric homeostasis and the results contribute to guidance for vegetation restoration practices in mining subsidence areas.