Interactive Effects of Nitrogen and Phosphorus on Soil Microbial Communities in a Tropical ForestReportar como inadecuado




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Elevated nitrogen N deposition in humid tropical regions may exacerbate phosphorus P deficiency in forests on highly weathered soils. However, it is not clear how P availability affects soil microbes and soil carbon C, or how P processes interact with N deposition in tropical forests. We examined the effects of N and P additions on soil microbes and soil C pools in a N-saturated old-growth tropical forest in southern China to test the hypotheses that 1 N and P addition will have opposing effects on soil microbial biomass and activity, 2 N and P addition will alter the composition of the microbial community, 3 the addition of N and P will have interactive effects on soil microbes and 4 addition-mediated changes in microbial communities would feed back on soil C pools. Phospholipid fatty acid PLFA analysis was used to quantify the soil microbial community following four treatments: Control, N addition 15 g N m−2 yr−1, P addition 15 g P m−2 yr−1, and NandP addition 15 g N m−2 yr−1 plus 15 g P m−2 yr−1. These were applied from 2007 to 2011. Whereas additions of P increased soil microbial biomass, additions of N reduced soil microbial biomass. These effects, however, were transient, disappearing over longer periods. Moreover, N additions significantly increased relative abundance of fungal PLFAs and P additions significantly increased relative abundance of arbuscular mycorrhizal AM fungi PLFAs. Nitrogen addition had a negative effect on light fraction C, but no effect on heavy fraction C and total soil C. In contrast, P addition significantly decreased both light fraction C and total soil C. However, there were no interactions between N addition and P addition on soil microbes. Our results suggest that these nutrients are not co-limiting, and that P rather than N is limiting in this tropical forest.



Autor: Lei Liu, Tao Zhang, Frank S. Gilliam, Per Gundersen, Wei Zhang, Hao Chen, Jiangming Mo

Fuente: http://plos.srce.hr/



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