title: Interactive effects of nitrogen and phosphorus on soil microbial communities in a tropical forest.
abstract: 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 N&P 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.
authors.affiliation: Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Liu
authors.forename: Tao
authors.initials: T
authors.lastname: Zhang
authors.forename: Frank S
authors.initials: FS
authors.lastname: Gilliam
authors.forename: Per
authors.initials: P
authors.lastname: Gundersen
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.forename: Hao
authors.initials: H
authors.lastname: Chen
authors.forename: Jiangming
authors.initials: J
authors.lastname: Mo
mesh_terms: D001419:Bacteria / Q000187:drug effects* / Q000378:metabolism; D018533:Biomass; D002681:China; D005227:Fatty Acids / Q000378:metabolism; D005308:Fertilizers; D009584:Nitrogen / Q000494:pharmacology*; D010743:Phospholipids / Q000378:metabolism; D010758:Phosphorus / Q000494:pharmacology*; D012987:Soil / Q000737:chemistry; D012988:Soil Microbiology; D014197:Trees / Q000187:drug effects* / Q000254:growth & development / Q000382:microbiology*; D014329:Tropical Climate
chemical_list: D005227:Fatty Acids; D005308:Fertilizers; D010743:Phospholipids; D012987:Soil; D010758:Phosphorus; D009584:Nitrogen