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Phosphorus-nitrogen feedbacks maintain balanced availability in hardwood forest soils

Phosphorus-nitrogen feedbacks maintain balanced availability in hardwood forest soils Tera Ratliff 11-July-2012. US Forest Service. Identifying the processes underlying limitations to productivity help us understand forest ecosystem response to change. Walker and Syers , 1976.

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Phosphorus-nitrogen feedbacks maintain balanced availability in hardwood forest soils

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  1. Phosphorus-nitrogen feedbacks maintain balanced availability in hardwood forest soils Tera Ratliff11-July-2012

  2. US Forest Service Identifying the processes underlying limitations to productivity help us understand forest ecosystem response to change Walker and Syers, 1976 Total Soil Nutrients Time (millions of years)

  3. Resource Optimization

  4. Resource optimization in response to N and P fertilization Response Ratio = Mean outcome of treatment: mean outcome of control • When N is high, organisms allocate to P • Do N and P equilibrate over the long-term? Marklein and Houlton, 2011

  5. Pretreatment (2008 to 2009) soil collection MELNHE plots • Cores divided into Oe and Oa • Resin strips buried in-situ (2010) C9 -1-A PO4-

  6. N and P availability covary in forests of varying ages in the northern hardwoods • N availability appears to promote P availability via phosphatase production.

  7. Conclusions • Tight coupling of N and P could contribute to colimitation at the ecosystem level • Resource optimization could work to prevent P-limitation in the short-term by increasing investment when N is high • Mechanisms of P redistribution from slowly available pools are of interest for understanding long-term effects of anthropogenic changes in N and P availability

  8. Acknowledgments Many people have helped in carrying out this project, so many thanks to KevanMinick, Mark Dempsey, Brittany Coyne, Stephanie Bailey, Carrie Rose Levine, members of the Fisk Lab, and collaborators at HBEF for assistance in the field and laboratory. Questions?

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