Forest harvesting effects on soil temperature, moisture, and respiration in a bottomland hardwood forest

The effect of forest disturbance on C cycling has become an issue, given co ncerns about escalating atmospheric C content. We examined the effects of h arvest intensity on in situ and laboratory mineral soil respiration in an E ast Texas bottomland hardwood forest between 6 and 22 mo after harvesting. Treatments included a clearcut, a partial cut wherein approximately 58% of the basal area was removed, and an unharvested control. The soda-lime absor ption technique was used for in situ respiration (CO2 efflux) and the wet a lkali method (NaOH) was used for laboratory mineral soil respiration. Soil temperature and moisture content were also measured. Harvesting significant ly (P = 0.05) increased in situ respiration during most sampling periods. T his effect was attributed to an increase in live root and microflora activi ty associated with postharvesting revegetation. In situ respiration increas ed exponentially (Q(10) relationship) as treatment soil temperatures increa sed (mean range 8.3-29.1 degrees C), but followed a parabolic-type pattern through the range of soil moisture measured (mean range 10.4-31.5%). Mean r ates of laboratory mineral soil respiration measured during the study were unaffected by cutting treatment for most sampling sessions. Overall, the me an rate of CO2 efflux in the clearcuts (7.15 g CO2 m(-2) d(-1)) was signifi cantly higher than that in the partial cuts (5.95 g CO2 m(-2) d(-1)), which in turn was significantly higher than that in the controls (4.95 g CO2 m(- 2) d(-1)). Mass balance estimates indicate that these treatment differences will have little or no long-term effect on C sequestration of these manage d forests.