Alteration of carbon, nitrogen, and phosphorus stoichiometry and their related enzymes as affected by increased soil coarseness

Abstract

Soil coarseness decreases ecosystem productivity, ecosystem carbon and nitrogen stocks, and soil nutrient contents in sandy grasslands. To gain insight into changes in soil carbon and nitrogen pools, microbial biomass, and enzyme activities in response to soil coarseness, a field experiment of sand addition was conducted to coarsen soil 5 with different intensities: 0% sand addition, 10%, 30%, 50%, and 70%. Soil organic carbon and total nitrogen decreased with the intensification of soil coarseness across three depths (0-10 cm, 10-20 cm, and 20-40 cm) by up to 43.9% and 53.7%, respectively. At 0-10 cm, soil microbial biomass carbon (MBC) and nitrogen (MBN) declined with soil coarseness by up to 44.1% and 51.9%, respectively, while microbial 10 biomass phosphorus (MBP) increased by as much as 73.9%. Soil coarseness significantly decreased the activities of β-glucosidase, N-acetyl-glucosaminidase, and acid phosphomonoesterase by 20.2%-57.5%, 24.5%-53.0%, and 22.2%-88.7%, respectively. Soil coarseness enhanced microbial C and N limitation relative to P, indicated by the ratios of β-glucosidase and N-acetyl-glucosaminidase to acid 15 phosphomonoesterase (and MBC:MBP and MBN:MBP ratios). As compared to laboratory measurement, values of soil parameters from theoretical sand dilution was significantly lower for soil organic carbon, total nitrogen, dissolved organic carbon, total dissolved nitrogen, available phosphorus, MBC, MBN, and MBP. Phosphorus immobilization in microbial biomass might aggravate plant P limitation in 20 nutrient-poor grassland ecosystems as affected by soil coarseness. We conclude that microbial C:N:P and enzyme activities might be good indicators for nutrient limitation 3 of microorganisms and plants.