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Soil CO fluxes represent a net balance between biological soil CO uptake and abiotic soil and (senescent) plant CO production. Studies largely from temperate and boreal forests indicate that soils serve as a net sink for CO, but to date uncertainty remains about the role of tropical rain forest soils. Here we report the first direct measurements of soil CO fluxes in a tropical rain forest. We compare with estimates of net ecosystem CO fluxes derived from accumulation of CO at night under stable atmospheric conditions. Further, we used laboratory experiments to demonstrate the importance of temperature on net soil CO fluxes. Net soil surface CO fluxes ranged from -0.19 to 3.36 nmol m-2 s-1, averaging ∼1 nmol CO m-2 s-1. Fluxes varied with season and topographic location, with highest fluxes measured in the dry season in a seasonally inundated valley. Ecosystem CO fluxes estimated from nocturnal canopy air profiles, which showed CO mixing ratios that consistently decreased with height, ranged between 0.3 and 2.0 nmol CO m-2 s-1. A canopy layer budget method, using the nocturnal increase in CO, estimated similar flux magnitudes (1.1 to 2.3 nmol CO m-2 s-1). In the wet season, a greater valley ecosystem CO production was observed in comparison to measured soil valley CO fluxes, suggesting a contribution of the valley stream to overall CO emissions. Laboratory incubations demonstrated a clear increase in CO production with temperature that was also observed in field fluxes, though high correlations between soil temperature and moisture limit our ability to interpret the field relationship. At a common temperature (25 ◦C), expected plateau and valley senescent leaf CO production was small (0.012 and 0.002 nmol CO m-2 s-1) in comparison to expected soil material CO emission (∼0.9 nmol CO m-2 s-1). Based on our field and laboratory observations, we expect that tropical rain forest ecosystems are a net source of CO, with thermal degradation-induced soil emissions likely being the main contributor to ecosystem CO emissions. Extrapolating our first observation-based tropical rain forest soil emission estimate of ∼1 nmol m-2 s-1, a global tropical rain forest soil emission of ∼16.0 Tg CO yr-1 is estimated. Nevertheless, total ecosystem CO emissions might be higher, since valley streams and inundated areas might represent local CO emission hot spots. To further improve tropical forest ecosystem CO emission estimates, more in-situ tropical forest soil and ecosystem CO flux measurements are essential. [ABSTRACT FROM AUTHOR]

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Copyright of Global Science & Technology is the property of Global Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The objective was to verify the leaflitter production of the two Cerrado types, one being stricto sensu Cerrado (s.s) and other riparian forests, both areas are located at the E×perimental Farm of the Federal University of Tocantins, Campus of Gurupi-TO. Ten collectors of 1 × 1 m were randomly installed in each of the studied areas, which were monitored monthly during the period of May 2012 to April 2013. The mean litter production showed variation only in the month of October 2012 and February 2013 with an annual output of 1829.31 kg ha-1 in the riparian physiognomy and 1349.01 kg ha-1 in the s.s. cerrado. The most representative fraction of Total litter found in the two physiognomies studied consisted of leaves making up 63.6% of the total material deposited in the traps followed by the timber fraction, flower and propagules respectively. [ABSTRACT FROM AUTHOR]