PARENT SESSION
Oral Session # 19: Biogeochemistry II: Grasslands.
Presiding: JT Lennon
Tuesday, August 5. 8:00 AM to 11:30 AM, SITCC Meeting Room 105.

Phosphorus dynamics under manipulated global change conditions in a California annual grassland.

Menge, Duncan^*,1, Field, Christopher^{1, 2}, ¹ Stanford University, Stanford, CA² Carnegie Institution of Washington, Stanford, CA

ABSTRACT- Global environmental factors changing with anthropogenic influence include increased CO₂, NO₃^- deposition, warming, and precipitation. The Jasper Ridge Global Change Experiment (JRGCE) at Stanford University's Jasper Ridge Biological Preserve manipulates all four of these factors in an annual grassland ecosystem, maintaining all combinations of ambient and elevated treatments for each factor. Phosphorus limitation may influence the extent to which these manipulations affect ecosystem processes such as NPP. This study investigates this biogeochemical feedback in the JRGCE. Extracellular phosphatases, enzymes secreted by plants and microbes, have been shown to indicate phosphorus demand in this system and others. Soil phosphatase activities were measured to assess ecosystem level P demand under these manipulations. Elevated NO₃^- significantly increased phosphatase activity, indicating higher P demand. Elevated precipitation significantly decreased phosphatase activity, indicating lower P demand. CO₂, warming, and all interaction terms were not significant.

Key words: Global change, Phosphorus, Grassland, Elevated CO2