Is the C:N:P stoichiometry in soil and soil microbial biomass related to the landscape and land use in southern subtropical China?

Abstract

Does the soil microbial biomass (SMB) in terrestrial ecosystems present well- constrained atomic carbon:nitrogen:phosphorus (C:N:P) ratios, analogous to the planktonic biomass in marine ecosystems? How do soil microbes respond to changes in the soil environment in terms of their elemental stoichiometry? Following up on the work of Cleveland and Liptzin (2007), we examined the stoichiometry of C, N and P in the soil and SMB and their relationships at both the landscape and land-use levels in subtropical terrestrial ecosystems. 1,069 soil samples were collected at a depth of 0-20 cm from three typical landscapes (a karst mountain, a low hill and a lowland) in southern subtropical China. The landscapes presented various land-use types (e.g., paddy field, upland, woodland, etc.) and intensities of anthropogenic activity. The samples were analyzed to determine soil organic C, total soil N and total soil P contents as well as SMB C, SMB N and SMB P. On average, atomic C:N:P ratios of 80:7.9:1 in the soil and 70.2:6:1 in the SMB were obtained for the region. A clear descending trend of the soil C:N:P ratios (not the SMB C:N:P ratios) was observed across the three landscapes in the order: karst mountain > low hill > lowland. Although significant variations primarily related to human activities were observed in the soil and SMB atomic C:N:P ratios across the landscapes and land-use types, a significant correlation (r = 0.56, p < 0.001) was found between the soil and SMB C:P ratios in the entire data set; however, the correlation for the comparable N:P ratios was not evident. Significant correlations between the soil and SMB C:N, C:P and even N:P ratios (mainly in the woodland) were also observed variably at the finer level of the landscape or land-use. The tendency for a C:N:P stoichiometric relationship to exist between microbes and the soil environment found in this study might suggest possible non-homeostasis of elemental stoichiometry in the SMB of the terrestrial ecosystems in southern subtropical China. © 2012. American Geophysical Union. All Rights Reserved.