Nit Kirtibutr

Methane oxidation by termite mounds estimated by the carbon isotopic composition of methane

Emission rates and carbon isotope ratios of CH4, emitted by workers of termites, and of CH4, emitted from their mounds, were observed in a dry evergreen forest in Thailand to estimate the proportion of CH4 oxidized during emission through the mound. The δ13C of CH4 emitted from a termite mound (−70.9 to −82.4‰) was higher than that of CH4 emitted by workers in the mound (−85.4 to −97. l‰). Using a fractionation factor (a = 0.987) for oxidation of CH4 which was obtained in the incubation experiment, an emission factor defined as (CH4 emitted from a termite mound/CH4 produced by termites) was calculated. The emission factor obtained in each termite mound was nearly zero for Macrotermes (fungus-growing termites), of which the nest has a thick soil wall and subterrannean termites, and 0.17 to 0.47 for Termitinae (small-mound-making termites). Global CH4 emission by termites was estimated on the basis of the CH4 emission rates by workers and termite biomass with the emission factors. The calculated result was 1.5 to 7.4 Tg/y (0.3 to 1.3% of total source), which is considerably smaller than the estimate by the IPCC [1994].

Underground passage system of Macrotermes carbonarius (Isoptera, Termitidae) in a dry evergreen forest of northeast Thailand

Summary. The complete underground passage systems of six colonies of the termite Macrotermes carbonarius in a dry evergreen forest within the Sakaerat Environmental Research Station, northeast Thailand, were excavated. We found 4-10 main underground passages radiating out from each mound, with smoothly plastered floors (6-35 cm below the soil surface). All of the underground passages were well built (2.5-13 cm wide) and one of the main passages extended 33 m from the nest. The total length of the passages of each colony varied between 33.8 m and 112.8 m. It was demonstrated that 5 adjacent colonies of M. carbonarius generally segregated their underground passages horizontally. Vertical segregation of the passages of M. carbonarius from a subterranean nest of the neighboring species, Macrotermes annandalei was also found. In contrast to other Macrotermes species, the underground passage system of M. carbonarius only consists of major tracks and lacks a dense network of passages in the terminal part of the system. In the vicinity of their foraging sites, M. carbonarius forages in the open using pavement trackways on the ground, which are considered to be equivalent to a dense network of fine passages of other Macrotermes species.

Stable Isotope Ratios and Uric Acid Preservation in Termites Belonging to Three Feeding Habits in Thailand

Abstract Nitrogen and carbon stable isotope ratios and uric acid concentrations in termites sampled from a dry evergreen forest in Thailand, were determined across three kinds of feeding habits. Feeding habits of Microcerotermes crassus, which is an abundant woodfeeder, and Dicuspiditermes makhamensis, a common soil-feeding termite, were confirmed by isotopic signatures. Lichen feeding termites (Hospitalitermes birmanicus, H. bicolor and H. ataramensis) were characterized by low δ15N values, suggesting that they assimilated nitrogen deposited from the atmosphere. There was also a significant difference in uric acid concentrations between termites representing different feeding habits. No significant relationships were found between uric acid concentrations and δ15N or δ13C in Hospitalitermes. However, δ15N values were correlated with C/N ratios in H. birmanicus, except in one colony of H. ataramensis. δ13C values in both species were negatively correlated with C/N ratios.