Spatial and temporal variation in soil CO2 efflux in an old-growth neotropical rain forest, LA Selva, Costa Rica
Our objectives were to quantify and compare soil CO2, efflux of two doininant soil types in an old-growth neotropical rain forest in the Atlantic zone of Costa Rica, and to evaluate the control of environmental Factors on CO2, release. We measured soil CO2 efflux from eight permanent soil chamhers on six Oxisol sites. Three sites were developed on old river terraces ('old alluvium') and the other three were developed on old lava flows ('residual'). At the same time we measured soil C02 concentrations. soil water content and soil tetnperature at various depths in 6 soil shafts (3 in deep). Between 'old alluvium' sites. the two-year average CO2 flux rates ranged from 117.3 to 128.9 nig C m-2 h-1. Signiticaiitly higher soil CO2, flux occurred on the 'residual' sites (141.1 to 184.2 ing C m-2 h-1). Spatial dil'ferences in CO2, efflux were related to fine root biomziss. soil carbon and phosphorus concentration hut also to soil water content. Spatial variability in CO2 storage was high and the amount of C02 stored in the upper and lower soil profile was different between 'old alluvial' and 'residual' sites. The inajor factor identifed Sot- explaining tetnporal variatiot~s in soil CO, efflux was soil water content. During periods of high soil water content CO2, etnission decreased. plnhahly due to lowet- diffusion and CO2, production rates. Dtiring the 2-year study period inter--annual variation in soil C02 efflux was not detected.
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