Response of litter-soil C,N,and P to grazing disturbance in coniferous plantations in sandy-hilly region of Northwest Shanxi Province,China
This study investigated the nutritional characteristics of litter-soil and their response to understory grazing in coniferous plantations within the sandy-hilly region of Northwest Shanxi,focusing on Pinus tabulaeformis and P.sylvestris var.mongolica plantations with a restoration period of approximately 30 years.We conducted a comparative analysis,examining differences in the levels of carbon,nitrogen,and phosphorus,C∶N,C∶P,and N∶P stoichiometry ratios,enzyme activities,and soil microbial biomass between two types of plantation litter(undecomposed and semi-decomposed layers)-soil(0-20 cm)with or without grazing disturbance.The results showed that the levels of organic carbon,total nitrogen,and total phosphorus in the litter from the four sites were in the range of 338.98-545.95,6.63-11.59,and 1.51-2.19 g/kg,respectively.Their C∶N,C∶P,and N∶P ratios were 31.80-78.93,161.29-361.84,and 3.45-6.58,respectively,and the activities of sucrase,urease,and phosphatase were 26.08-34.52,0.03-0.29,and 0.29-0.97 mg g-1 h-1,respectively.In addition,the levels of soil organic carbon,total nitrogen,and total phosphorus from the four sites were in the range of 4.65-9.54,0.78-1.29,and 0.24-0.47 g/kg,respectively,and the levels of soil nitrate nitrogen,ammonium nitrogen,available phosphorus and microbial biomass C and N were 0.21-0.28,10.90-15.38,1.94-4.00,28.17-83.55,and 5.16-10.18 mg/kg,respectively.The C∶N,C∶P,and N∶P ratios were 6.00-7.40,18.68-24.23,and 2.77-3.62,respectively and the activities of soil sucrase,urease,and phosphatase were 17.90-24.70,1.08-1.71,and 0.46-1.01 mg g-1 h-1,respectively.Grazing disturbance significantly increased the activities of urease and phosphatase in the semi-decomposed litter layer as well as soil organic carbon,total nitrogen,total phosphorus,microbial biomass C,and the activity of phosphatase in P.tabulaeformis and P.sylvestris var.mongolica plantations.In addition,grazing disturbance significantly increased the total nitrogen content and N∶P ratio in the undecomposed layer of litter and soil urease activity in P.tabulaeformis plantation.Moreover,it increased the total phosphorus content in the undecomposed and semi-decomposed layers of litter,urease activity in the undecomposed layer,sucrase activity in the semi-decomposed layer,and soil nitrate nitrogen,available phosphorus,and sucrase activity in P.sylvestris var.mongolica plantation.Furthermore,the soil organic carbon,total nitrogen,and total phosphorus content,especially the microbial biomass C,nitrate nitrogen,and available phosphorus,and the soil sucrase,urease,and phosphatase activities related to C,N,and P in P.sylvestris var.mongolica plantation were significantly higher than in the P.tabulaeformis plantation.Notably,the litter-soil nutrient cycling in this study was limited by the combination of N and P.However,moderate grazing in the plantations can alleviate litter-soil N and P limitation and accelerate litter decomposition and soil C,N,and P transformation especially in the active state.Our findings indicate that P.sylvestris var.mongolica plantation is more conducive for increased availability of soil C,N,and P and should be considered in regional afforestation planning and Populus simonii renovation.
sandy-hilly region of Northwest Shanxiconiferous plantationlittersoilstoichiometrygrazing
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万方数据
