As early as in 1934, American oceanographer Alfred C. Redfield has advanced a startling theory－Redfield ratio, namely, the atomic ratio of carbon(C), nitrogen(N) and phosphorus(P) found in plankton and throughout the deep oceans is found to be 106:16:1. Redfield ratio has led to a deep understanding of the biological processes occurring in ocean ecosystems.
However, whether a similar stoichiometric relationship exists between the organisms and soil environment in terrestrial ecosystems? How do soil microbes respond to changes in the soil environment in terms of their elemental stoichiometry?
Puzzled by these questions, Prof. WU Jinshui, together with other colleagues in Institute of Subtropical Agriculture, Chinese Academy of Sciences(ISA) selected three typical landscapes －a karst mountain in Dacai, Guangxi Province, a low hill in Pantang, Hunan Province and a lowland in Yuanjiang, Hunan Province (Figure 1) for study. 1,069 soil samples, which presented various land-use types (e.g., paddy field, upland, woodland, etc.) and intensities of anthropogenic activity were collected at a depth of 0–20 cm from these three typical landscapes.
Researchers analyzed the samples to determine soil organic C, total soil N and total soil P contents as well as soil microbial biomass (SMB) C, SMB N and SMB P. Through chemical analysis and statistical analysis, They found that on average, the atomic C:N:P ratios in the soil (80:7.9:1 on average) and SMB (70.2:6:1 on average) were both considered constrained 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. Moreover, a significant correlation (r = 0.56, p < 0.001) was found between the soil and SMB C:P ratios in the entire data set despite the influences of human activities; However, the correlation for the comparable N:P ratios was not evident. They also observed that soil and SMB C:N, C:P and even N:P ratios (mainly in the woodland) had significant correlations.
“The results in this study might suggest possible non-homeostasis of elemental stoichiometry in the SMB of the terrestrial ecosystems in southern subtropical China.” said Dr. LI Yong, the first author of this paper. “Still, our data covered only a small proportion of the subtropical region of China, if there were more data associated with various land-use types and large sample sizes are obtained from different climatic zones in countries of all continents around the world and systematically analyzed, the puzzle regarding what is actually regulating SMB elemental stoichiometry can be solved.”
This research was financially supported by the National Basic Research Program of China (2011CB100506) and the Chinese Academy of Sciences (KZCX2-YW-423 and the 100 Talents Program).
The study entitled " Is the C:N:P stoichiometry in soil and soil microbial biomass related to the landscape and land use in southern subtropical China?” has been published in top journal GLOBAL BIOGEOCHEMICAL CYCLES( doi:10.1029/2012GB004399, 2012).