PARENT SESSION
OOS 5: Restoration Effects of Fire and Thinning Treatments on Mixed-Conifer Ecosystems.
Organized by: M North and J Innes
Monday, August 2, 8:00 AM to 11:30 AM, Meeting Room E 148.

Disturbance effects on spatial variability of soil respiration vary with summer water conditions in an old-growth mixed-conifer forest.

MA, S.^*,1, CONCILIO, A.¹, CHEN, J.¹, NORTH, M.², ¹ University of Toledo, Toledo, OH, USA² University of California, Davis, Davis, CA, USA

ABSTRACT- Soil respiration can vary spatially by vegetation patch type and following disturbance. We examined soil respiration response to prescribed burning and thinning treatments and the influences of interannual climate variability on soil respiration in 2002 and 2003 in an old-growth mixed-conifer forest in California's Sierra Nevada. Soil respiration rate (SRR), soil temperature, and soil moisture were measured along 20-40 m long transects in six treatments: unburned-unthinned (UN), unburned and overstory-thinned (US), unburned and understory-thinned (UC), burned-unthinned (BN), burned and overstory-thinned (BS), burned and understory-thinned (BC). Analysis of variance (ANOVA) was applied to test the hypothesis that SRR were significantly different among treatments and patch types within each year. We compared the pattern of SRR along transects in each treatments using nonparametric test. Within these 6 treatments, we also stratified our SRR samples by three patch types, closed canopy, the dominant shrub ceanothus and open canopy or gap. There were significant differences in SRR between treatments in 2002 (p = 0.0013) but not in 2003. SRR were significantly different between patch types (p < 0.0001) in both years with ceanothus > closed canopy > gap. We found that SRR along the transects in UC and US were significant different between the two years (p = 0.0372 and 0.0023, respectively). The results indicate that disturbance treatments significantly altered SRR in different, post-treatment years. Compared to burning treatments, thinning treatments seemed more sensitive to increases in soil moisture associated with interannual climate variability and fine scale changes in soil microclimatic conditions.

Key words: thinning, spatial distribution, prescribed-burning, interannual climate variability