phosphorus-nitrogen feedbacks maintain balanced availability in hardwood forest soils
DESCRIPTION
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. - PowerPoint PPT PresentationTRANSCRIPT
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Phosphorus-nitrogen feedbacks maintain balanced availability in hardwood forest
soils Tera Ratliff
11-July-2012
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Time (millions of years)
Tota
l Soi
l Nut
rient
s Walker and Syers, 1976
US Forest Service
Identifying the processes underlying limitations to productivity help us understand forest ecosystem response to change
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Resource Optimization
High C:N:P
High N:PP-limiting
Investment in phosphatse
N:P
Low N:PN-limiting
Investment in decomposition
N:P
Low C:N:PC-limiting
Investment in C-mineralizing
enzymes
C:N:P
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Resource optimization in response to N and P fertilization
• When N is high, organisms allocate to P
• Do N and P equilibrate over the long-term?
Marklein and Houlton, 2011
Response Ratio = Mean outcome of treatment: mean outcome of control
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• Pretreatment (2008 to 2009) soil collection MELNHE plots
• Cores divided into Oe and Oa
• Resin strips buried in-situ (2010)
C9 -1-A
PO4-
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• N and P availability covary in forests of varying ages in the northern hardwoods
• N availability appears to promote P availability via phosphatase production.
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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
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Questions?
AcknowledgmentsMany people have helped in carrying out this project, so many thanks to Kevan Minick, 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.