Applied Soil Ecology 75 (2014) 181–188 Contents lists available at ScienceDirect Applied Soil Ecology journal h om epage: www.elsevier.com/locate/apsoil Phosphorus enrichment helps increase soil carbon mineralization in vegetation along an urban-to-rural gradient, Nanchang, China Fu-Sheng Chen a,∗ , Joseph Yavitt b , Xiao-Fei Hu c a College of Forestry, Jiangxi Agricultural University, Nanchang 330045, PR China b Department of Natural Resources, Cornell University, Ithaca, NY 14853-3001, USA c College of Life Sciences, Nanchang University, Nanchang 330031, PR China a r t i c l e i n f o Article history: Received 29 July 2013 Received in revised form 14 November 2013 Accepted 15 November 2013 Keywords: Biogeochemistry Forest Soil carbon mineralization Soil phosphorus Urbanization a b s t r a c t We used four vegetation types located along an urban–suburban–rural gradient in Nanchang, China to study how the deposition of nitrogen (N) and phosphorus (P) in the urban area affected soil carbon (C) cycling. We found that total P, nitrate (NO 3 - –N), available P, and the abundances of culturable bacteria, actinobacteria, and nitrifying bacteria in soils, collected to 15 cm depth in August of 2008, decreased along the urban-to-rural gradient (P < 0.05); the C/P and N/P ratios, ammonium (NH 4 + –N), and culturable fungi abundance showed the reverse trends; whereas soil organic C, total N, C/N, mineral N, and the activities of sucrase and neutraland acid phosphatase showed no pattern with gradient and vegetation type. Com- pared to suburban and rural sites, total and available P in soil increased 168% and 131%, 47% and 139%, respectively in urban sites. The cumulative amount of CO 2 emission per gram of soil (C min , incubated from 2 to 43 days) varied little along the urban-to-rural gradient, but showed positive correlations with organic C, total N, total P, nitrate, mineral N concentrations, C/N, bacteria and actinobacteria abundances, sucrase and acid phosphatase activities. In contrast, the cumulative amount of CO 2 produced per gram organic C (C min /OC) within the incubation period was influenced by gradient, vegetation type, and their interaction, and values were about 35% greater in the urban than in suburban and rural sites. The rela- tionship between elevated C min /OC in urban vegetations and the enrichment of P in organic matter (P/C ratio) suggests that P coming from urban household waste can degrade the stability of organic C in urban soils. © 2013 Elsevier B.V. All rights reserved. 1. Introduction Biogeochemical studies in urban and suburban areas often find high nitrogen (N) deposition to soils (Chen et al., 2010a; Groffman et al., 2006; Liu et al., 2011), and the linkages between biogeochemical cycles of N and carbon (C) (Schlesinger et al., 2011) suggest that added N could alter soil C dynamics. How- ever, urban and suburban areas also can experience disturbed phosphorus (P) cycles (Baxter et al., 2002; Chen et al., 2010b), and P also influences soil C dynamics. Here we explore the con- sequences of elevated N and P for soil C mineralization in soil located along an urban-suburban-rural gradient in Nanchang, China. There is evidence that added N in mesic forests and grass- lands leads to an increase in soil C storage (Nave et al., 2009). One reason is that plant growth and litter production (leaf and root) increase with added N (Fornara and Tilman, 2012; Thomas et al., ∗ Corresponding author. Tel.: +86 791 83813243; fax: +86 791 83813243. E-mail address: chenfush@yahoo.com (F.-S. Chen). 2010); although, with no additional P, the increase in plant growth could decrease available P in soil (Lu et al., 2012; Vitousek et al., 2010). Indeed interactions between N and C cycles could account for reports that available P is less (Baxter et al., 2002) or greater (Hu et al., 2011) in urban and suburban areas than in adjoining rural areas, and among other reasons. Moreover, additional N can stabilize soil organic matter (Cusack et al., 2011; Nave et al., 2009), given that N increases rates of litter decomposition only if there is an abundance of decomposable organic compounds with a high C/N ratio. In contrast, experiments with added P in tropical forests suggest enhanced rates of microbial action in litter decomposition (Cleveland et al., 2006; Kaspari et al., 2008), but it is unclear if results from tropical forests could be applied to other ecosystems. China presents a unique opportunity to examine how soil C dynamics are being altered by urbanization. Areas have urban- ized quickly, temporally, and spatially, and thus forests established many years ago in a rural setting now occur within urban and suburban settings (Chen et al., 2010b). Thus changes in ecosys- tem structure and function between urban and rural settings can be attributed to urbanization rather than pre-existing conditions. Urbanization produces multiple environmental effects, including 0929-1393/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.apsoil.2013.11.011