PARENT SESSION
Poster Session #1: Decomposition and Soil Respiration.
Monday, August 5. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC

Drought effects on soil respiration in a temperate forest.

SAVAGE, KATHLEEN^*,1, BORKEN, WERNER¹, DAVIDSON, ERIC¹, TRUMBORE, SUSAN², ¹ Woods Hole Research Center, Woods Hole, MA² University of California at Irvine, Irvine, CA

ABSTRACT- Temperature plays a primary role in the seasonal variation of soil respiration, but precipitation also affects both seasonal and interannual variations in respiration. We present here the first year of results of experimentally induced drought on soil respiration at the Harvard Forest in central Massachusetts. The objective is to quantify the effects of drought in a replicated and controlled experiment. We established three replicate plots (20 m²), in each of two treatments, control and throughfall exclusion. Throughfall was excluded with plastic roofing panels about 1 m above the ground during 84 days from July 2nd through Sept. 24th, 2001, which excluded 168 mm of throughfall. Four collars were placed in each of the 6 plots for weekly measurements of soil respiration using a dynamic chamber system. Concentrations and radiocarbon content of soil atmosphere CO₂ were also measured at 6 soil depths within each plot. Cumulative mean soil respiration was significantly lower in the exclusion plots (241 g C m^-2) compared to the control plots (341 g C m^-2) during the 84 days of treatment. The soil CO₂ concentrations were lower and the radiocarbon contents were higher in the profiles of the exclusion plots compared to the control plots. Root respiration and decomposition of recently fixed C substrates (with low ¹⁴C signatures) was more strongly affected by drought than was decomposition of older, more radiocarbon-rich substrates.

KEY WORDS: respiration, radiocarbon