Factors controlling spatio‐temporal variation in carbon dioxide efflux from surface litter, roots, and soil organic matter at four rain forest sites in the eastern Amazon

Abstract

1] This study explored biotic and abiotic causes for spatio-temporal variation in soil respiration from surface litter, roots, and soil organic matter over one year at four rain forest sites with different vegetation structures and soil types in the eastern Amazon, Brazil. Estimated mean annual soil respiration varied between 13-17 t C ha À1 yr À1 , which was partitioned into 0-2 t C ha À1 yr À1 from litter, 6-9 t C ha À1 yr À1 from roots, and 5-6 t C ha À1 yr À1 from soil organic matter. Litter contribution showed no clear seasonal change, though experimental precipitation exclusion over a one-hectare area was associated with a ten-fold reduction in litter respiration relative to unmodified sites. The estimated mean contribution of soil organic matter respiration fell from 49% during the wet season to 32% in the dry season, while root respiration contribution increased from 42% in the wet season to 61% during the dry season. Spatial variation in respiration from soil, litter, roots, and soil organic matter was not explained by volumetric soil moisture or temperature. Instead, spatial heterogeneity in litter and root mass accounted for 44% of observed spatial variation in soil respiration (p < 0.001). In particular, variation in litter respiration per unit mass and root mass accounted for much of the observed variation in respiration from litter and roots, respectively, and hence total soil respiration. This information about patterns of, and underlying controls on, respiration from different soil components should assist attempts to accurately model soil carbon dioxide fluxes over space and time.

Biogeochemical processes along a nutrient gradient in a tropical ombrotrophic peatland

“…Indeed, potential soil respiration determined on drained samples in the current study showed a clear link to nutrient status. This was not reflected in the pattern of CO 2 flux in the field, however, suggesting that variables other than nutrient status, such as root respiration (Chimner 2004;Metcalfe et al 2007) or water table fluctuations (Jauhiainen et al 2005), regulate the net CO 2 efflux from the peat surface. The CO 2 flux rates were within the range of those measured from lowland forested swamps on deep peat in central Kalimantan, Indonesia (ca.…”

Root oxygen loss from Raphia taedigera palms mediates greenhouse gas emissions in lowland neotropical peatlands

“…Root respiration and elevated respiration rates due to labile C inputs from roots contribute to net soil CO 2 emissions (Davidson and Janssens 2006). For example, root respiration contributed between 40 and 60 % from net soil emissions in forests in the Eastern Amazon during the dry season (Metcalfe et al 2007). Therefore, we attribute the decline in CO 2 emissions to loss of respiration from R. taedigera roots, and to the suppression of root exudates, which are to some extent consumed and converted into CO 2 by rhizosphere microorganisms.…”

Above- and below-ground net primary productivity across ten Amazonian forests on contrasting soils

“…The plot CAX-06, is a tall primary forest (35 m height canopy) situated on a clay ferralsol (oxisol in USDA soil taxonomy) near a flux tower site ). The CAX-03 plot is a sandier site located 2 km to further south, which was the control plot for a drought experiment (Metcalfe et al, 2007a). The Terra Preta site (CAX-08) is a late successional forest on an ArchaeoAnthrosol (this classification was modified from the WRB soil taxonomy by Kampf et al (2003) to encompass the variability of Terra Preta soils in Amazonia).…”