Chronic Nitrogen Enrichment at the Watershed Scale Does Not Enhance Microbial Phosphorus Limitation |
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Authors: | Corianne Tatariw Jean D. MacRae Ivan J. Fernandez Marie-Cécile Gruselle Cayce J. Salvino Kevin S. Simon |
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Affiliation: | 1.School of Biology and Ecology,University of Maine,Orono,USA;2.Civil and Environmental Engineering,University of Maine,Orono,USA;3.School of Forest Resources,University of Maine,Orono,USA;4.Orange County Environmental Protection Division,Orlando,USA;5.School of Environment,University of Auckland,Auckland,New Zealand |
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Abstract: | Increased N inputs through chronic atmospheric deposition has enriched temperate forest ecosystems, altering critical ecosystem functions such as decomposition and potentially resulting in a shift to P limitation. We used a combination of microbial biomass stoichiometry and enzymatic activity analyses to evaluate the potential for microbial nutrient limitation over the course of a growing season in response to multi-decadal, whole-watershed N enrichments and a one time, plot-scale P addition that occurred in the 22nd year of whole-watershed treatments. The one-time P addition increased microbial biomass threefold and reduced N-acetyl-glucosaminidase (NAG) and acid phosphatase (AP) activity 1 week after application, but there was no interaction with long-term experimental N enrichment to indicate a shift to P limitation. However, both N and P treatments increased C limitation independently of each other over the duration of the study based on measured increases in β-1,4-glucosidase (BG) activity relative to NAG and AP. Microbial biomass stoichiometry and enzyme activity indicated that BBWM is P limited regardless of N status. Our findings highlight the complex interactions between C, N, and P use and limitation in a forested ecosystem subjected to long-term N enrichment. |
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