PARENT SESSION
Oral Session #24: Forests: Carbon allocation, carbon budgets. Presiding: C. Reid.
Tuesday, August 7, 2001. 8:00 AM to 11:15 AM. Hall of Ideas F.

Temperature and moisture dependency of soil respiration in six temperate forests.

Borken, Werner^1,3, Xu, Yun², Davidson, Eric¹, Beese, Fritz³, ^{1 3 2}

ABSTRACT- The objectives of this study were to investigate the temporal variation in soil respiration of six temperate forest sites and to validate a previously developed soil temperature-moisture-model. Soil respiration was measured using chambers over two years under mature beech, spruce and pine stands with distinct climate and soil at Solling and at Unterluess, Germany. Cumulative annual CO₂ fluxes varied from 4.0 to 5.7 Mg C ha^-1 yr^-1, with no statistically significant differences among years or sites. However, soil respiration rates of the sandy sites at Unterluess tended to decrease in the dry and warm summer 1999 while soil respiration at the silty Solling site tended to increase. Although the Solling site was also dry during the summer of 1999, the amount of precipitation was 28% higher than at Unterluess. Soil temperature at 5 cm and 10-cm depth explained 82% of the temporal variation in soil respiration. The correlations were weaker using temperature at 0 cm (r²=0.65) and 2.5 cm depth (r²=0.80). Mean Q₁₀ values for the range from 5 to 15°C were 1.95 at 0 cm and 3.61 at 10-cm depth. Our model results suggest that temporal variation in soil moisture generally had little effect on annual soil respiration rates, except that CO₂ flux from sandy soils may be limited by soil moisture during dry summers.

KEY WORDS: soil respiration, temperate forest, temperature dependency, summer drought