Does elevated CO2 alter P cycling in a mature Eucalyptus woodland (EucFACE)?
Abstract
Increased CO2 in the atmosphere stimulates ecosystem photosynthesis and the growth of trees, so long as there are sufficient soil nutrients that can be accessed. A large body of work has investigated how nitrogen (N) availability modulates the elevated CO2 response of trees and forest ecosystems, but until recently the constraints of another major plant nutrient, phosphorus (P), on the elevated CO2 response have not been examined in detail, particularly for forested ecosystems. We have found strong constraints of P availability on the aboveground tree growth response to elevated CO2 in a mature Eucalyptus forest ecosystem under free-air CO2 enrichment (EucFACE) in southeastern Australia. As a result, we aimed to assemble biogeochemical information regarding all the major pools and fluxes of P to understand how this limitation is realized, and measure feedbacks from the ecosystem P cycle for the Eucalyptus forest under increased CO2 concentration (+150 ppm). We hypothesized that there would be different mechanisms for how elevated CO2 affects the biogeochemistry of P compared to what is known for N, including a much stronger P retention due to low soil P availability. We describe the effects of elevated CO2 on major P pools for the Eucalyptus forest, including the tree canopy, wood biomass, and belowground pools including soil microbes, soil solution and several soil P fractions , as well as the major transfers amongst these pools. We found a mean residence time for P in the vegetation of ~ 5 years, with a substantial portion of P recycled within the forest canopy. Our findings challenge conventional thinking about the mobility of P as well as its biogeochemical linkages to C cycling, and have implications for how we measure and represent the biogeochemistry of P in ecosystem to biospheric models.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.B12B..01E
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 0470 Nutrients and nutrient cycling;
- BIOGEOSCIENCES;
- 1622 Earth system modeling;
- GLOBAL CHANGE