Document: JEF-3-59-84

Belowground processes in successional Douglas-fir stands.

KLOPATEK, J.M.*

Arizona State University, Tempe, AZ 85287 U.S.A. ¹

Abstract:
Three Douglas-fir Pseudotsuga menzeii forest stands were examined at an near the Wind River Canopy Crane Research Facility (WRCCRF) in the Gifford Pinchot N.F. in southcentral Washington. A twenty, a forty and an old-growth forest were examined to measure belowground carbon and nitrogen storage and soil respiration. In addition nylon mesh bags of homogenized soils were inserted at each site to quantify root ingrowth and potential C sequestration/loss. The forty year old site had a significant mix of red alder within the Douglas-fir and consequently had significantly greater (almost two-fold) concentrations of N in the forest floor and soil than either the 20 year old or old-growth sites. Root ingrowth at the 40 year old site was significantly less than the 20 year old site. Both young stands showed markedly less fine root growth than the old-growth site, which based on this and previous data averaged >10 Mg Yr^-1. The low amount of fine root production at the N rich 40 year old site was accompanied by a corresponding low level of soil CO₂ efflux during the growing season. Peak rates of soil CO₂ efflux at the 40 year old stand were 50% less than the 20 year old stand and 40% less than the old-growth stand. The fine root growth and soil respiration data support the hypothesis that the belowground allocation of carbon decreases in a more productive/fertile environment.

Keywords: Soil Carbon, Soil Respiration, CO2

This abstract is being presented at: 3:30 PM in session:
ROOT PROCESSES