Phosphate additions have no effect on microbial biomass and activity in a northern hardwood forest |
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| Institution: | 1. State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Northwest A & F University, Yangling, Shaanxi 712100, PR China;2. Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, Yangling, Shaanxi 712100, PR China;3. University of Chinese Academy of Sciences, Beijing 100049, PR China;1. State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China;2. University of the Chinese Academy of Sciences, Beijing 10049, China;3. Department of Environment and Science, Dutton Park, QLD 4102, Australia;4. Environmental Futures Research Institute, Griffith University, Nathan, QLD 4111, Australia;5. AgResearch Limited, Ruakura Research Centre, Hamilton 3240, New Zealand;6. Agro-Technology Institute, RUDN University, Moscow, Russia;7. Department of Soil Science of Temperate Ecosystems, Department of Agricultural Soil Science, University of Göttingen, Büsgenweg 2, Göttingen 37077, Germany;8. Soil Science Consulting, 37077 Göttingen, Germany;9. College of Urban and Environmental Sciences, Peking University, Beijing 100871, China |
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| Abstract: | High rates of atmospheric nitrogen (N) deposition have raised questions about shifting patterns of nutrient limitation in northern hardwood forests. Of particular interest is the idea that increased supply of N may induce phosphorus (P) limitation of plant and microbial processes, especially in acid soils where P sorption by Al is high. In this study, we established field plots and plant-free laboratory mesocosms with P and Ca additions to test the hypotheses that 1) microbial biomass and activity are limited by P in the northern hardwood forest soils at the Hubbard Brook Experimental Forest in NH USA; 2) elevated Ca increases inherent P availability and therefore reduces any effects of added P and 3) P effects are more marked in the more carbon (C) rich Oie compared to the Oa horizon. Treatments included P addition (50 kg P ha−1), Ca addition (850 kg Ca ha−1) and Ca + P addition (850 kg Ca ha−1 and 50 kg P ha−1). The P treatments increased resin-available P levels and reduced phosphatase activity, but had no effect on microbial biomass C, microbial respiration, C metabolizing enzymes, potential net N mineralization and nitrification in the Oie or Oa horizon of either field plots or plant free mesocosms, in either the presence or absence of Ca. Total, prokaryote, and eukaryote PLFA were reduced by P addition, possibly due to reductions in mycorrhizal fungal biomass. These results suggest that increased N deposition and acidification have not created P limitation of microbial biomass and activity in these soils. |
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