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Alteration of soil carbon and nitrogen pools and enzyme activities as affected by increased soil coarseness

Ruzhen Wang, Linyou Lü, Courtney A. Creamer, Feike A. Dijkstra, Heyong Liu, Xue Feng, Guoqing Yu, Xingguo Han, Yong Jiang
2017 Biogeosciences  
<p><strong>Abstract.</strong> Soil coarseness decreases ecosystem productivity, ecosystem carbon (C) and nitrogen (N) stocks, and soil nutrient contents in sandy grasslands subjected to desertification. To gain insight into changes in soil C and N pools, microbial biomass, and enzyme activities in response to soil coarseness, a field experiment was conducted by mixing native soil with river sand in different mass proportions: 0, 10, 30, 50, and 70<span class="thinspace"></span>% sand addition.
more » ... n>% sand addition. Four years after establishing plots and 2 years after transplanting, soil organic C and total N concentrations decreased with increased soil coarseness down to 32.2 and 53.7<span class="thinspace"></span>% of concentrations in control plots, respectively. Soil microbial biomass C (MBC) and N (MBN) declined with soil coarseness down to 44.1 and 51.9<span class="thinspace"></span>%, respectively, while microbial biomass phosphorus (MBP) increased by as much as 73.9<span class="thinspace"></span>%. Soil coarseness significantly decreased the enzyme activities of <i>β</i>-glucosidase, N-acetyl-glucosaminidase, and acid phosphomonoesterase by 20.2–57.5<span class="thinspace"></span>%, 24.5–53.0<span class="thinspace"></span>%, and 22.2–88.7<span class="thinspace"></span>%, used for C, N and P cycling, respectively. However, observed values of soil organic C, dissolved organic C, total dissolved N, available P, MBC, MBN, and MBP were often significantly higher than would be predicted from dilution effects caused by the sand addition. Soil coarseness enhanced microbial C and N limitation relative to P, as indicated by the ratios of <i>β</i>-glucosidase and N-acetyl-glucosaminidase to acid phosphomonoesterase (and MBC<span class="thinspace"></span>:<span class="thinspace"></span>MBP and MBN<span class="thinspace"></span>:<span class="thinspace"></span>MBP ratios). Enhanced microbial recycling of P might alleviate plant P limitation in nutrient-poor grassland ecosystems that are affected by soil coarseness. Soil coarseness is a critical parameter affecting soil C and N storage and increases in soil coarseness can enhance microbial C and N limitation relative to P, potentially posing a threat to plant productivity in sandy grasslands suffering from desertification.</p>
doi:10.5194/bg-14-2155-2017 fatcat:wdvnid5sqrfefal4ke4v7amagy