Effects of long-term nitrogen deposition on phosphorus leaching dynamics in a mature tropical forest |
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Authors: | Kaijun Zhou Xiankai Lu Taiki Mori Qinggong Mao Cong Wang Mianhai Zheng Hui Mo Enqing Hou Jiangming Mo |
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Affiliation: | 1.Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, and Guangdong Provincial Key Laboratory of Applied Botany, South China Botanical Garden,Chinese Academy of Sciences,Guangzhou,China;2.University of Chinese Academy of Sciences,Beijing,China |
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Abstract: | Elevated anthropogenic nitrogen (N) deposition is suggested to affect ecosystem phosphorus (P) cycling through altered biotic P demand and soil acidification. To date, however, there has been little information on how long-term N deposition regulates P fluxes in tropical forests, where P is often depleted. To address this question, we conducted a long-term N addition experiment in a mature tropical forest in southern China, using the following N treatments: 0, 50, 100, and 150 kg N ha?1 year?1. We hypothesized that (i) tropical forest ecosystems have conservative P cycling with low P output, and (ii) long-term N addition decreases total dissolved phosphorus (TDP) leaching losses due to reduced litter decomposition rates and stimulated P sorption deriving from accelerated soil acidification. As hypothesized, we demonstrated a closed P cycling with low leaching outputs in our forest. Under experimental N addition, TDP flux in throughfall was significantly reduced, suggesting that N addition may result in a less internal P recycling. Contrary to our hypothesis, N addition did not decrease TDP leaching, despite reduced litter decomposition and accelerated soil acidification. We find that N addition might have negative impacts on biological P uptake without affecting TDP leaching, and that the amount of TDP leaching from soil could be lower than a minimum concentration for TDP retention. Overall, we conclude that long-term N deposition does not necessarily decrease P effluxes from tropical forest ecosystems with conservative P cycling. |
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