Contrasting responses to drought of forest floor CO2 efflux in a loblolly pine plantation and a nearby Oak-Hickory forest
Abstract
Forest floor C02 efflux (Fff) depends on vegetation type, climate, and soil physical properties. We assessed the effects of biological factors on Fff by comparing a maturing pine plantation (PP) and a nearby mature Oak-Hickory-type hardwood forest (HW). Fff was measured continuously with soil chambers connected to an IRGA during 2001-2002. At both sites, Fff depended on soil temperature at 5cm (T5) when soil was moist (soil moisture, 0> 0.20 m3mm-3)a, nd on both T5 and 0 when soil was drier. A model (Fff( T5,0 )) explained 292% of the variation in the daily mean Fff at both sites. Higher radiation reaching the ground during the leafless period, and a thinner litter layer because of faster decomposition, probably caused higher soil temperature at HW compared with PP. The annual Frt was estimated at 1330 and 1464 g Cm