PARENT SESSION
Oral Session #27: Fire Ecology.
Presiding: C. Allen
Tuesday, August 6. 8:00 AM to 11:30 AM. Graham Meeting Room, TCC.

Post-fire effects on ecosystem gas exchange patterns in northern Great Basin communities.

Prater, Margaret^*,1, Obrist, Daniel², Arnone, John², DeLucia, Evan¹, ¹ Department of Plant Biology, Urbana, IL² Division of Earth and Ecosystem Sciences, Reno, NV

ABSTRACT- The transformation from perennial sagebrush to annual invasive plant communities as a result of wildfire will likely alter key ecosystem processes in the Great Basin, including the hydrologic and carbon cycles. Using an open path gas analyzer enclosed in a 1-m³ static chamber, we measured ecosystem water vapor and carbon fluxes in adjacent post-fire and intact sagebrush communities near Reno, NV. Shrub plots provide the major source of water loss and carbon uptake in the intact sagebrush community (mean rates of 0.59–0.75 mmol H₂O m^-2 s^-1 and 1.1–2.8 mol CO₂ m^-2 s^-1). In the dry summer of 2001, shrubs had consistently greater water fluxes than either inter-shrub spaces or the post-fire community (p<0.01), reflecting shrub access to deeper soil moisture reserves that are unavailable to the shallow-rooted burn community. Patterns of carbon fluxes were related to changes in leaf area and phenology in both post-fire and sagebrush communities. No difference was found between carbon fluxes from shrub and burn plots in mid-summer when leaf area in the post-fire community was at its peak and when shrub uptake in intact communities was decreasing; however, carbon uptake of the annual post-fire community decreased as vegetation senesced. Productivity in the Great Basin may be reduced further as lower evapotranspiration from post-fire communities may increase runoff and nutrient losses.

KEY WORDS: sagebrush, evapotranspiration, carbon flux