Termite Biomass Research Articles

A conversion proposal for biomass estimates in termites

AbstractTermites (Isoptera) constitute a considerable fraction of the global animal biomass. Conventionally, termite dry biomass estimates (g) range between 1:3 and 1:6 of fresh biomass (g). But estimates are often based on a few species or coarse taxonomic resolution. In this study, we (1) calculated the fresh and dry mass of 15 widely distributed Neotropical termite species (three families) and (2) established the conversion ratio for dry mass, which is indispensable for biomass estimates. Workers and soldiers were sampled in their colonies and quickly weighed in the laboratory to obtain the fresh mass. Then, the individuals were placed in 80% alcohol for 5 days and weighed. Finally, the samples were dried at 60°C for 24 h and weighed again. Our results suggest an average ratio of 1:4.2 (dry‐to‐fresh mass), with a mean (±SE) conversion ratio of 0.24 ± 0.06, for estimating termite biomass at local, regional, and global scales. Moreover, our results demonstrate that values from termites preserved in alcohol could still be used to estimate biomass. Specifically, after insertion in alcohol, the termites lost 16.9%–56% of their water content, with an average of 26.5%. While this represents a source of bias in estimates using samples from biological collections, dry mass was significantly related to fresh mass ( = 0.99; dry mass = 0.000055 + 0.22 × fresh mass), and to the mass of termites in alcohol ( = 0.97; dry mass = 0.00014 + 0.26 × mass in alcohol). Applying our results to data from the literature indicates that global termite dry biomass ranges from 89 to 106 Mt.

Effect of farming on the vegetation structure, soil properties and termite assemblages in the northern Congo Basin

AbstractThe growing human population requires vast amounts of supplies that are satisfied by a large agricultural expansion leading to alarming deforestation of tropical forests. Agriculture in the large part now is unsustainable as tropical soils are relatively nutrient poor, the amount of organic matter decreases fast and the soil invertebrates and microorganisms vanish over time. From a socio‐economic point of view, agroforestry is a sustainable alternative to slash‐and‐burn practices, but its impact on termites, major macroinvertebrates responsible for the organic matter turnover, is poorly understood. Furthermore, other vegetation layers besides tree canopy are rarely included in studies despite their strong effect on soil macrofauna. Thus, we investigated the impact of human activities in Southern Cameroon by analysing the biomass of termites, the soil properties, the vegetation structure at three different classes (trees, shrubs and herbs) and the amount of raw vegetal material along a land‐use gradient of primary forest ‐ secondary forest ‐ cocoa agroforestry ‐ maize cropland. Within each of the habitats, two independent areas of 1 ha each were laid out for samples collection. Our results show similar trends for all variables, with a reduction of organic carbon as well as available micronutrients, plant diversity and abundance and dead plant matter stocks along the land‐use intensification. The same trend is shown by the abundance and biomass of termites, best exemplified by the absence of soil‐feeding termites in the maize cropland. We thus recommend for support to nature‐friendly agroforestry systems preserving a large share of the original soil invertebrates.

Production of Activated Carbon Electrode for Energy Storage Application in Supercapacitors via KOH Activation of Waste Termite Biomass

Production of Activated Carbon Electrode for Energy Storage Application in Supercapacitors via KOH Activation of Waste Termite Biomass

The role of termite CH<sub>4</sub> emissions on the ecosystem scale: a case study in the Amazon rainforest

Abstract. The magnitude of termite methane (CH4) emissions is still an uncertain part of the global CH4 budget and current emission estimates are based on limited field studies. We present in situ CH4 emission measurements of termite mounds and termite mound subsamples performed in the Amazon rainforest. Emissions from five termite mounds of the species Neocapritermes brasiliensis were measured by use of a large flux chamber connected to a portable gas analyser measuring CH4 and CO2. In addition, the emissions of mound subsamples were measured, after which the termites were counted so that a termite CH4 and CO2 emission factor could be determined. Mound emissions were found to range between 17.0 and 34.8 nmol mound−1 s−1 for CH4 and between 1.1 and 13.0 µmol mound−1 s−1 for CO2. A termite emission factor of 0.35 µmol CH4 gtermite-1 h−1 was found, which is almost twice as high as the only other reported value for the Amazon. By combining mound emission measurements with the termite emission factor, colony sizes could be estimated, which were found to range between 55–125 thousand individuals. Estimates were similar to literature values, and we therefore propose that this method can be used as a quick non-intrusive method to estimate termite colony size in the field. The role of termites in the ecosystem's CH4 budget was evaluated by use of two approaches. Termite mound emission values were combined with local mound density numbers, leading to an estimate of 0.15–0.71 nmol CH4 m−2 s−1, on average, emitted by termite mounds. In addition, the termite CH4 emission factor from this study was combined with termite biomass numbers, resulting in an estimate of termite-emitted CH4 of ∼1.0 nmol m−2 s−1. Considering the relatively low net CH4 emissions previously measured at this ecosystem, we expect that termites play an important role in the CH4 budget of this terra firme ecosystem.

Digging mammal reintroductions reduce termite biomass and alter assemblage composition along an aridity gradient.

Invasions can trigger cascades in ecological communities by altering species interactions. Following the introduction of cats and foxes into Australia, one tenth of Australia's terrestrial mammal species became extinct, due to predation, while many continue to decline. The broader consequences for Australian ecosystems are poorly understood. Soil-dwelling invertebrates are likely to be affected by the loss of fossorial native mammals, which are predators and disturbance agents. Using reintroductions as a model for ecosystems prior to species loss, we tested the hypothesis that mammal reintroduction leads to reduced vegetation cover and altered termite assemblages, including declines in abundance and biomass and changed species composition. We hypothesised that the magnitude of mammal reintroduction effects would diminish with increasing aridity, which affects resource availability. We compared six paired sites inside and outside three reintroduction sanctuaries across an aridity gradient. We sampled termite assemblages using soil trenches and measured habitat availability. Reintroductions were associated with increased bare ground and reduced vegetation, compared with controls. Aridity also had an underlying influence on vegetation cover by limiting water availability. Termite abundance and biomass were lower where mammals were reintroduced and the magnitude of this effect decreased with increasing aridity. Termite abundance was highest under wood, and soil-nesting wood-feeders were most affected inside sanctuaries. Ecological cascades resulting from exotic predator invasions are thus likely to have increased termite biomass and altered termite assemblages, but impacts may be lower in less-productive habitats. Our findings have implications for reserve carrying capacities and understanding of assemblage reconstruction following ecological cascades.

Termite mounds mitigate half of termite methane emissions

Termites are responsible for ∼1 to 3% of global methane (CH4) emissions. However, estimates of global termite CH4 emissions span two orders of magnitude, suggesting that fundamental knowledge of CH4 turnover processes in termite colonies is missing. In particular, there is little reliable information on the extent and location of microbial CH4 oxidation in termite mounds. Here, we use a one-box model to unify three independent field methods-a gas-tracer test, an inhibitor approach, and a stable-isotope technique-and quantify CH4 production, oxidation, and transport in three North Australian termite species with different feeding habits and mound architectures. We present systematic in situ evidence of widespread CH4 oxidation in termite mounds, with 20 to 80% of termite-produced CH4 being mitigated before emission to the atmosphere. Furthermore, closing the CH4 mass balance in mounds allows us to estimate in situ termite biomass from CH4 turnover, with mean biomass ranging between 22 and 86 g of termites per kilogram of mound for the three species. Field tests with excavated mounds show that the predominant location of CH4 oxidation is either in the mound material or the soil beneath and is related to species-specific mound porosities. Regardless of termite species, however, our data and model suggest that the fraction of oxidized CH4 (f ox) remains well buffered due to links among consumption, oxidation, and transport processes via mound CH4 concentration. The mean f ox of 0.50 ± 0.11 (95% CI) from in situ measurements therefore presents a valid oxidation factor for future global estimates of termite CH4 emissions.

Head width–body mass equation: facilitating worker termite biomass estimates

1. Termites are one of the most important invertebrate ecosystem engineers in tropical regions, which may be quantified using termite biomass data. However, biomass data are particularly difficult to collect as they rely on termites being weighed in the field, which may neither be possible nor convenient. Local scale linear regression models, based on termite head widths (mm) and body masses (mg), have been used in the past to estimate termite biomass using head width and abundance data. However, these models represent very limited numbers of termite taxa from single sites. In the present study, I provide one of the most representative linear regression models available based on 90 samples from three different countries (Peru, Kenya, and Malaysia).2. Although the linear regression model under‐ or overestimated body weights of taxa with characteristic features (e.g. large heads of Odontotermes workers or elongated abdomens of Kalotermitidae) it provides a robust method for estimating termite biomass at the community level. Additionally, while there are limitations related to the general model, which may be solved by focusing on taxa specific data and the use of higher accuracy equipment, it is the first model to facilitate termite biomass estimates using the head with and abundance data only.3. This study encourages the use of termite biomass data to gain a better understanding of termites in ecosystem processes and calls for comparative data to be gathered for the purpose of creating models that may be representative of the variability among termite taxa.

First comparison of quantitative estimates of termite biomass and abundance reveals strong intercontinental differences

Abstract:Termite species and functional groups differ among regions globally (the functional-diversity anomaly). Here we investigate whether similar differences in biomass and abundance of termites occur among continents. Biomass and abundance data were collected with standardized sampling in Cameroon, Malaysia and Peru. Data from Peru were original to this study, while data from Cameroon and Malaysia were compiled from other sources. Species density data were sampled using a standardized belt transect (100 × 2 m) while the biomass and abundance measurements were sampled using a standardized protocol based on 2 × 2-m quadrats. Biomass and abundance data confirmed patterns found for species density and thus the existence of the functional diversity anomaly: highest estimates for biomass and abundance were found in Cameroon (14.5 ± 7.90 g m−2 and 1234 ± 437 ind m−2) followed by Malaysia (0.719 ± 0.193 g m−2 and 327 ± 72 ind m−2) and then Peru (0.345 ± 0.103 g m−2 and 130 ± 39 ind m−2). The biomass and abundance for each functional group were significantly different across sites for most termite functional groups. Biogeographical distribution of lineages was the primary cause for the functional diversity anomaly with true soil-feeding termites dominating in Cameroon and the absence of fungus-growing termites from Peru. These findings are important as the biomass and abundance of functional groups may be linked to ecosystem processes. Although this study allowed for comparisons between data from different regions further comparable data are needed to enhance the understanding of the role of termites in ecosystem processes on a global scale.

Social insects dominate eastern US temperate hardwood forest macroinvertebrate communities in warmer regions.

Earthworms, termites, and ants are common macroinvertebrates in terrestrial environments, although for most ecosystems data on their abundance and biomass is sparse. Quantifying their areal abundance is a critical first step in understanding their functional importance. We intensively sampled dead wood, litter, and soil in eastern US temperate hardwood forests at four sites, which span much of the latitudinal range of this ecosystem, to estimate the abundance and biomass m−2 of individuals in macroinvertebrate communities. Macroinvertebrates, other than ants and termites, differed only slightly among sites in total abundance and biomass and they were similar in ordinal composition. Termites and ants were the most abundant macroinvertebrates in dead wood, and ants were the most abundant in litter and soil. Ant abundance and biomass m−2 in the southernmost site (Florida) were among the highest values recorded for ants in any ecosystem. Ant and termite biomass and abundance varied greatly across the range, from <1% of the total macroinvertebrate abundance (in the northern sites) to >95% in the southern sites. Our data reveal a pronounced shift to eusocial insect dominance with decreasing latitude in a temperate ecosystem. The extraordinarily high social insect relative abundance outside of the tropics lends support to existing data suggesting that ants, along with termites, are globally the most abundant soil macroinvertebrates, and surpass the majority of other terrestrial animal (vertebrate and invertebrate) groups in biomass m−2. Our results provide a foundation for improving our understanding of the functional role of social insects in regulating ecosystem processes in temperate forest.

Xylophagous termites: A potential sink for atmospheric nitrous oxide

To provide a better understanding of soil–atmosphere gas exchange processes, this study describes the atmospheric nitrous oxide (N2O) uptake by xylophagous termites and the biological process involved. The N2O consumption rates of three xylophagous termite species (Hodotermes mossambicus, Nasutitermes voeltzkowi and Hodotermopsis sjoestedti) were determined in incubation vials with ambient, artificially enhanced N2O concentrations in the headspace. Live individuals of the three termite species significantly decreased N2O concentrations (88%) in the headspace of the vials after 24 h incubation in the dark. The acetylene reduction assay method applied to N. voeltzkowi, a xylophagous termite species, showed a decrease in N2O uptake in acetylene-treated individuals, indicating the potential involvement of termite gut denitrifying microbes. The N2 formed is potentially subjected to assimilation via nitrogenase reductase into termite biomass through biological fixation as demonstrated by the reduction of acetylene to ethylene at an average rate of 18.21 ± 1.34 nmol C2H4 g−1 dw d−1. Further studies should focus on measurements of N2O-reductase (nosZ) gene activity in termite guts to gain a better understanding of the N2O reduction process in xylophagous termite species.

Influence of earthworms and termites on runoff and erosion in a tropical steep slope fallow in Vietnam: A rainfall simulation experiment

Earthworms and termites, as soil engineers, play a major role in the regulation of biogeochemical processes and the provision of ecosystem services. They create biogenic aggregates on the soil surface, e.g., earthworm casts and termite sheetings, which can influence soil erosion and the downward transfer of fertility. We assessed the effect of the micro-relief generated by earthworms and termites on soil hydrodynamic properties, and soil and nutrient losses. Eighteen 1m×1m plots were established for rainfall simulation experiments (2 runs of 40min rain, intensity 90mmh−1) in a steep slope fallow in Northern Vietnam. The soil surface of the micro-plots differed in the proportions of earthworm casts and termite sheetings. The results confirmed the importance of soil biostructures in the regulation of pedohydrological properties of soils. Although globular water-stable earthworm casts promote water infiltration in soil and decrease soil and nutrient losses, the unstable termite sheetings break-down rapidly and generate structural crusts which foster water runoff and soil detachment. No relation was observed between the abundance or biomass of earthworms or termites and the pedohydrological properties measured during the rainfall simulations. This therefore suggests that soil engineers can have greater impact on ecosystem functioning through their biogenic structures rather than as a result of their own abundance or biomass.

Termite mound emissions of CH4 and CO2 are primarily determined by seasonal changes in termite biomass and behaviour.

Termites are a highly uncertain component in the global source budgets of CH(4) and CO(2). Large seasonal variations in termite mound fluxes of CH(4) and CO(2) have been reported in tropical savannas but the reason for this is largely unknown. This paper investigated the processes that govern these seasonal variations in CH(4) and CO(2) fluxes from the mounds of Microcerotermes nervosus Hill (Termitidae), a common termite species in Australian tropical savannas. Fluxes of CH(4) and CO(2) of termite mounds were 3.5-fold greater in the wet season as compared to the dry season and were a direct function of termite biomass. Termite biomass in mound samples was tenfold greater in the wet season compared to the dry season. When expressed per unit termite biomass, termite fluxes were only 1.2 (CH(4)) and 1.4 (CO(2))-fold greater in the wet season as compared to the dry season and could not explain the large seasonal variations in mound fluxes of CH(4) and CO(2). Seasonal variation in both gas diffusivity through mound walls and CH(4) oxidation by mound material was negligible. These results highlight for the first time that seasonal termite population dynamics are the main driver for the observed seasonal differences in mound fluxes of CH(4) and CO(2). These findings highlight the need to combine measurements of gas fluxes from termite mounds with detailed studies of termite population dynamics to reduce the uncertainty in quantifying seasonal variations in termite mound fluxes of CH(4) and CO(2).

The Potential and Limits of Termites (Isoptera) as Decomposers of Waste Paper Products

Termites (Isoptera) have often been proposed as decomposers oflignocellulosic waste, such as paper products, while termite biomass could be harvested for food supplements. Groups of Coptotermes formosanus Shiraki and Reticulitermes speratus (Kolbe) were kept for 4 and 8 wk, respectively, in the laboratory and given up to 10 different types of paper as their food source. Paper consumption, survival, caste composition, and lipid content were recorded. Corrugated cardboard was by far the most consumed paper product, although survival on it was not necessarily favorable. In R. speratus, lipid reserves and neotenic numbers were quite high, but no breeding occurred. Cardboard may be the "junk food" equivalent for termites. Within the tested period, termites did not perform well on paper products that form the bulk of waste paper--corrugated cardboard, newsprint, and pamphlets and magazines. On all paper products (except recycled office paper), neotenic reproductives were formed, but larvae were observed only on kraft pulp and tissue paper. That all waste paper products contain lignocellulosic fibers does not automatically make them suitable for decomposition by termites. Each paper product has to be assessed on its own merit to see whether termites can reproduce on this diet, if it were to be a candidate for sustainable "termidegradation" and termite biomass production.

Nitrogen mineralization, denitrification, and nitrate ammonification by soil-feeding termites: a 15N-based approach

Soil-feeding termites are abundant and play important roles in the biogeochemical processes in tropical soils. Previous studies indicated that they preferentially utilize the peptidic components of soil organic matter as a nutrient resource. Here, we determined the corresponding mineralization fluxes and elucidated other N transformation processes that occur during soil gut passage using 15 N tracer tech- niques. Termite-based rates of N mineralization by Cubitermes umbratus and Cubitermes ugandensis in soil microcosms amended with 15 NH4 ? were 6.6 and 9.2 nmol N day -1 (g fresh wt) -1 , which means that the soil peptides fuel about 20 and 40% of the respiratory activity of these insects. Considering the areal biomass of soil-feeding termites in humid savannahs, soil- feeding termites should mineralize about 3% of the total N in their food soil per year. In addition to producing ammonia from ingested 15 NO3 - at approx- imately 10% of the mineralization rate, C. umbratus also formed N2 at similar rates. The formation of labelled N2 in microcosms amended with 15 NH4 ? seems to be at least partially due to nitrification activity in the soil; evidence for the formation of nitrate in the posterior hindgut remains inconclusive. However, the so far unexplained increase of 15 N abundance in the ammonia pools of the posterior hindgut compartments manifests additional hitherto unknown metabolic pro- cesses in this gut region. Collectively, our results not only reinforce the concept of nitrogenous soil compo- nents as an important dietary resource for soil-feeding termites, but also allow us to predict that N mineral- ization and nitrate ammonification activities in the termite gut should positively affect the dynamics of N in tropical soil.

Biomass and abundance of termites in three remnant areas of Atlantic Forest in northeastern Brazil

Termite biomass and abundance were estimated in three remnant areas of Atlantic Forest in northeastern Brazil: Reserva Biológica de Pedra Talhada-RBPT (Alagoas State), Parque Estadual Dois Irmãos-PEDI (Pernambuco State), and Área de Proteção Ambiental Mata do Buraquinho-APMB (Paraíba State). A quantitative sampling of the termite assemblages present on trunks and leaf litter, in nests, and in the soil was undertaken during the months of June and July (rainy season) and November and December (dry season) of 2000. Thirty seven species of termites were encountered and quantified in the three remnant forest areas. The termite biomass varied from 10.09 to 11.30 g (fresh weight)/m² and abundance varied from 4911 to 5663 individuals/m². The subfamily Nasutitermitinae was dominant in terms of the number of species, biomass, and abundance. The soil-feeders were the most abundant at the three sites, while wood-feeders had the largest biomass at least at the PEDI and APMB sites. Among the microhabitats quantified, termites were most frequently encountered in the soil, being most heavily concentrated at depths of 0-20 cm. Two species stood out in terms of their biomass and abundance: Embiratermes parvirostris Constantino, on the soil, and Nasutitermes corniger (Motschulsky), on decomposing trunks and in nests. Estimates of biomass and abundance suggest that termites play an important role in the decomposition of the plant necromass in remnant forest areas of the Atlantic Forest in northeastern Brazil.

The effect of termite biomass and anthropogenic disturbance on the CH4 budgets of tropical forests in Cameroon and Borneo

SummaryThe exchange of CH4 between tropical forests and the atmosphere was determined by simultaneously measuring the net CH4 flux at the soil surface and assessing the flux contribution from soil‐feeding termite biomass, both within the soil profile and in mounds. In Cameroon the flux of CH4 ranged from a net emission of 40.7 ng m–2 s–1 to a net CH4 oxidation of –53.0 ng m–2 s–1. Soil‐inhabiting termite biomass was significantly correlated with CH4 flux. Termite mounds emitted up to 2000 ng s–1 mound–1. Termite‐derived CH4 emission reduced the soil sink strength by up to 28%. Disturbance also had a strong effect on the soil sink strength, with the average rate of CH4 oxidation, at – 17.5 ng m–2 s–1, being significantly smaller (≈ 36%) at the secondary forest site than the –27.2 ng m–2 s–1, observed at the primary forest site. CH4 budgets calculated for each site indicated that both forests were net sinks for CH4 at – 6.1 kg ha–1 y–1 in the near‐primary forest and – 3.1 kg ha–1 y–1 in the secondary forest.In Borneo, three forest sites representing a disturbance gradient were examined. CH4 oxidation rates ranged from 0 to – 32.1 ng m–2s–1 and a significant correlation between the net flux and termite biomass was observed only in an undisturbed primary forest, although the biomass was insufficient to cause net emission of CH4. Rates of CH4 oxidation were not significantly different across the disturbance gradient but were, however, larger in the primary forest (averaging – 15.4 ng m–2 s–1) than in an old‐growth secondary forest (–13.9 ng m–2s–1) and a young secondary re‐growth (– 10.8 ng m–2s–1). CH4 flux from termite mounds ranged from net oxidation in an abandoned mound to a maximum emission of 468 ng s–1 mound–1. CH4 budgets calculated for each site indicated that CH4 flux from termite mounds had an insignificant effect on the budget of CH4 at the regional scale at all three forest sites. Annual oxidation rates were – 4.8, – 4.2 and – 3.4 kg ha–1 y–1 in the primary, secondary and young secondary forests, respectively.

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].

Occurrence, body mass and biomass of Syntermes spp. (Isoptera: Termitidae) in Reserva Ducke, Central Amazonia

The leaf-feeding species Syntermes molestus and S. spinosus are two dominant termite species in Reserva Ducke in Central Amazonia; two other species (S. aculeosus, S. longiceps) exist in the area. All species except S. aculeosus were also found in urban areas. The workers of S. molestus and S. spinosus have average body dry weights of 4.5±0.2 and 13.1±1.4 mg, and the weight of their soldiers is 8.2±0.2 and 51.0±1.7 mg, respectively. Therefore, S. spinosus is among the largest termites of the world. In both species, fresh weight is about 4.7 higher than dry weight (a wider relation than in other termite species). The biomass of the populations of both species amounted to about 1 g m-2 (dry weight; indirect estimate), which rises previous assessments of the total termite biomass by about 36-45%, to a value of 3.0-3.5 g m-2.

Methane emission by termites and oxidation by soils, across a forest disturbance gradient in the Mbalmayo Forest Reserve, Cameroon

AbstractMethane fluxes were measured, using static chambers, across a disturbance gradient in a West African semi‐deciduous humid forest. Soil‐feeding termite biomass was simultaneously determined, in an attempt to examine its influence on the net soil‐atmosphere exchange of CH4. CH4 emission rates from individual termite species were determined under laboratory conditions, permitting the gross production of CH4 to be compared with net fluxes to the atmosphere. Both net CH4 oxidation(‐) and emission were observed, and CH4 fluxes ranged from – 24.6 to 40.7 ng m–2 s–1. A statistically significant relationship between termite biomass and CH4 flux was observed across the forested sites such that: CH4 flux (ng m–2 s–1) = 4.95 × termite biomass (gm–2)–10.9 (P &lt; 0.001). Rates of CH4 oxidation were on average 60% smaller at the clearfelled and Terminalia plantation sites than at the near‐primary forest site. Two of the disturbed sites were net CH4 sources during one of the sampling periods. Disturbance of tropical forests, resulting in a decrease in the CH4 sink capacity of the soil, may therefore increase the contribution of termite‐derived CH4 to the atmosphere. Measurements from the mounds of the soil‐feeding termites Thoracotermes macrothorax and Cubitermes fungifaber from the old plantation site gave a CH4 emission of 636 and 53.4 ng s–1 mound–1, respectively. The forest floor surrounding the mounds was sampled in three concentric bands. Around the mound of T. macrothorax the soil was a net source of CH4 estimated to contribute a further 148 ng s–1. Soil surrounding the mound of C. fungifaber was mostly a net sink. The mounds of soil‐feeding termites are point sources of CH4, which at the landscape scale may exceed the general sink capacity of the soil, to an extent dependent on seasonal variations in soil moisture and level of disturbance.

Biomass of termites and their emissions of methane and carbon dioxide: A global database

A global database describing the geographical distribution of the biomass of termites and their emissions of methane and carbon dioxide has been constructed. Termite biomasses were assigned to various ecosystems using published measurements and a recent high‐resolution (10′ × 10′) database of vegetation categories. The assigned biomasses were then combined with literature measurements of fluxes of methane and carbon dioxide from termites and extrapolated to give global emission estimates for each gas. The global emissions of methane and carbon dioxide are 19.7 ± 1.5 and 3500 ± 700 Mt yr−1, respectively (1 Mt = 1012 g). These emissions contribute approximately 4% and 2%, respectively, to the total global fluxes of these gases. This database gives an accurate distribution of the biomasses and gaseous emissions by termites and may be incorporated into global models of the atmosphere.