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Partitioning of root respiration and rhizomicrobial respiration in a Robinia pseudoacacia plantation based on 13C natural abundance |
Song Wenchen1, Tong Xiaojuan1, Zhang Jinsong2, Meng Ping2, Li Jun3 |
1.School of Forestry, Beijing Forestry University,100083, Beijing, China; 2.Key Laboratory of Tree Breeding and Cultivation of State Forestry Administration, Research Institute of Forestry, Chinese Academy of Forestry,100091, Beijing, China; 3.Key Laboratory of Water Cycle and Related Land Surface Processes, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, 100101, Beijing, China |
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Abstract Partitioning soil respiration into root respiration, rhizomicrobial respiration and basal microorganism respiration is of important significance in ecological and pedological studies. The method of δ13C natural abundance is an ideal way in microbial biomass research to partition rhizosphere respiration into root respiration and rhizomicrobial respiration; however, it is difficult to be applied under field conditions. In this study, the method of nature 13C abundance was used to partition soil respiration into root respiration, rhizomicrobial respiration and basal micro-organism respiration in a Robinia pseudoacacia plantation in the Yellow River Xiaolangdi Ecology Research Station. The difficulties of separating root respiration and rhizomicrobial respiration by 13C natural abundance in the plantation have been solved in this study, which include: 1) the error caused by damage and disturbance, 2)ruling out δ13C difference caused by C3 and C4 photosynthetic pathways between soil and plant, and 3) the problem of soil CO2 diffusion fractionation. The δ13C value of the soil ranged from - 19‰to - 23‰. It is suggested that carbon isotopic composition of soil organic matters in the deeper soil requires a long time to cycle so that the influence of returning maize cropland to plantation on soil carbon isotope would not vanish completely.The δ13C values of soil organic matters did not change significantly with soil depth, while the δ13C values of rootless soil organic matters had a significantly positive correlation with soil depth. Theδ13C fractionation of CO2 diffusion in the soil was about 2.0‰, suggesting that the root respiration and rhizomicrobial respiration of the R. pseudoacacia plantation has been successfully separated by 13C natural abundance in this study. The results showed that the proportions of root respiration ( fR ) and rhizomicrobial respiration (fM ) were about 43% and 57% in July, 52% and 48% in August,and 27% and 73% in September, respectively. fR and fM were influenced by soil temperature and their standard deviation (SD) was higher under a lower soil conductivity. The method of 13C natural abundance is proved to be a suitable approach for partitioning plantation soil respiration into root respiration, rhizomicrobial respiration and basal microorganism respiration.
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Received: 28 September 2014
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