No abstract

Soil C and N turnover rates and contents are strongly influenced by climates (e.g., mean annual temperature MAT, and mean annual precipitation MAP) as well as human activities. However, the effects of converting natural forests to intensively human-managed plantations on soil carbon (C), nitrogen (N) dynamics across various climatic zones are not well known. In this study, we evaluated C, N pool and natural abundances of δ13C and δ15N in forest floor layer and 1-meter depth mineral soils under natural forests (NF) and plantation forest (PF) at six sites in eastern China. Our results showed that forest floor had higher C contents and lower N contents in PF compared to NF, resulting in high forest floor C/N ratios and a decrease in the quality of organic materials in forest floor under plantations. In general, soil C, N contents and their isotope changed significantly in the forest floor and mineral soil after land use change (LUC). Soil δ13C was significantly enriched in forest floor after LUC while both δ13C and δ15N values were enriched in mineral soils. Linear and non-linear regressions were observed for MAP and MAT in soil C/N ratios and soil δ13C, in their changes with NF conversion to PF while soil δ15N values were positively correlated with MAT. Our findings implied that LUC alters soil C turnover and contents and MAP drive soil δ13C dynamic.

No abstract

Surface mining activities usually devastate the landscape, rendering it unsuitable for plant growth. Organic amendments have been widely applied for the restoration of soil nutrients as well as the soil structure in mine tailings. However, the responses of growth and nutrient uptake among plant species to organic amendments have not been well evaluated. In this study, we conducted a pot experiment to examine the impacts of peat and cattle manure amendments on the total soil C, N, P, K, Ca, and Mg; the available soil P, K, Ca, and Mg; and the growth and nutrient concentrations of re-established Mongolian pine (Pinus sylvestris var. mongolica), lespedeza (Lespedeza daurica), and lyme grass (Elymus dahuricus) in the Guliku placer gold mine area in northeastern China. Organic amendments, especially cattle manure, improved the soil nutrient status and availability compared with those in nonamended mine soils. The plant biomass and nutrients of the 3 species were altered differently by the 2 amendments. Although peat addition increased the total soil C, total N, and available Ca, it had little impact on plant biomass production due to a lesser increase in available soil P, K, and Mg and a decrease in total soil K. Our results highlight that both balanced increase in soil nutrients by applying appropriate soil amendments and the selection of suitable plant species are necessary for the successful reclamation of postmined lands.