Characteristics of soil CO2 efflux variability in an aseasonal tropical rainforest in Borneo Island

Abstract

Although soil carbon dioxide (CO 2 ) efflux from tropical forests may play an important role in global carbon (C) balance, our knowledge of the fluctuations and factors controlling soil CO 2 efflux in the Asian tropics is still poor. This study characterizes the temporal and spatial variability in soil CO 2 efflux in relation to temperature/moisture content and estimates annual efflux from the forest floor in an aseasonal intact tropical rainforest in Sarawak, Malaysia. Soil CO 2 efflux varied widely in space; the range of variation averaged 17.4 lmol m -2 s -1 in total. While most CO 2 flux rates were under 10 lmol m -2 s -1 , exceptionally high fluxes were observed sporadically at several sampling points. Semivariogram analysis revealed little spatial dependence in soil CO 2 efflux. Temperature explained nearly half of the spatial heterogeneity, but the effect varied with time. Seasonal variation in CO 2 efflux had no fixed pattern, but was significantly correlated with soil moisture content. The correlation coefficient with soil moisture content (SMC) at 30 and 60 cm depth was higher than at 10 cm depths. The annual soil CO 2 efflux, estimated from the relationship between CO 2 efflux and SMC at 30 cm depth, was 165 mol m -2 year -1 (1,986 g C m -2 year -1 ). As this area is known to suffer severe drought every 4-5 years caused by the El Nino-Southern Oscillation, the results suggest that an unpredictable dry period might affect soil CO 2 efflux, leading an annual variation in soil C balance.

Simulated drought reduces soil CO2efflux and production in a tropical forest in Sulawesi, Indonesia

“…Environmental controls regulating temporal soil CO 2 efflux patterns Soil CO 2 efflux observed in the control plots was comparable to soil respiration rates measured in other tropical rainforests in Asia (Ishizuka et al 2005, Ohashi et al 2008, Adachi et al 2009) and in Latin America , Schwendenmann et al 2003, Sotta et al 2006, Davidson et al 2008. The temporal pattern of soil CO 2 efflux at our site was strongly influenced by soil moisture.…”

“…In contrast to temperate and boreal zones where soil temperature is recognized as the main controlling climatic variable regulating temporal CO 2 efflux, this study, like other studies conducted in the tropics , Schwendenmann et al 2003, Ohashi et al 2008, found that soil temperature had a negligible effect on soil respiration. This is not surprising because the temperature fluctuation at the site was only 4.58C during our daytime measurements over the 2.5-year experimental period.…”

Soil fertility controls soil–atmosphere carbon dioxide and methane fluxes in a tropical landscape converted from lowland forest to rubber and oil palm plantations

“…Mean soil CO 2 fluxes from our forest sites (Table 2) were within the range of reported fluxes (123-228 mg C m −2 h −1 ) from tropical rainforests in Asia (Adachi et al, 2005;Ohashi et al, 2008) and Latin America Schwendenmann et al, 2003;Keller et al, 2005;Sotta et al, 2006;Koehler et al, 2009). Compared to measurements conducted in Indonesia, our lowland forests had higher soil CO 2 fluxes than a montane forest in Sulawesi at 1000 m elevation with similar spatially replicated and temporally intensive measurements (127 mg C m −2 h −1 ; van Straaten et al, 2011); fluxes were also higher than in the seven partially logged forest sites in Jambi, where measurements were only made once (162 mg C m −2 h −1 ; Ishizuka et al, 2005).…”

Spatial and temporal effects of drought on soil CO<sub>2</sub> efflux in a cacao agroforestry system in Sulawesi, Indonesia

“…Measured CO 2 efflux rates indicate that the ecosystem is very productive as respiration rates were within or slightly below the range measured in tropical forest ecosystems in Asia (Adachi et al, 2006;Ohashi et al, 2008), and in Latin America (Davidson et al, 2000(Davidson et al, , 2008Schwendenmann et al, 2003;Sotta et al, 2006).…”