Results
Rate of CO2 emissions were directly detected on the mounds of 5 dominant termite species (n = 5) during the dry and wet seasons in the DEF at SERS. The characteristic of the selected termite mounds was described as the size, feeding group, and physical and environmental factors (Table 1). The mound CO2 emissions were widely variable ranging from 0.17 to 55.15 µmol CO2m-2 s-1, while the range of CO2 emissions from their surrounding soil was considerably narrower from 0.68 to 14.86 µmol CO2m-2 s-1. The results showed that the mean of the CO2 emission rate was significantly different between the termite species (F= 49.174 P< 0.001) (Table 2).
The highest average of the mound CO2 emission was fromG. sulphureus that reached up to 37.7 ± 14.7 µmol m-2 s-1 mean± SD, followed byM. crassus , T. comis , T. propinquus and D. makhamensis which were 15.50 ± 7.84, 6.45 ± 2.35, 1.98 ± 1.78, and 1.79 ± 0.99 µmol m-2 s-1 mean ± SD, respectively. In both locations, CO2 emission rate was significantly different between the mound and surrounding soil (F =35.2.10, P < 0.001) (Table 2) (Fig 4). While CO2 emission from the surrounding soil alone was not different between species (P = 0.657) (Fig 4).
The mean of the total CO2 emission from the mounds (12.68 ± 15.41 µmol m-2 s-1 mean± SD) was 2.5 times higher than surrounding soils (5.06 ± 3.29 µmol m-2 s-1 mean± SD). The overall mean of CO2 emissions from the mounds was 3.9 and 2.1 times higher than surrounding soils in the dry and wet seasons, respectively (Fig 5). There was a significant difference for both mounds and surrounding soils between the dry season and wet season (F = 14.957 P < 0.001) (Table 2). In each season, mound CO2 emissions were significantly different among the species and surrounding soils in the dry season and wet season (P < 0.001). The mound CO2 emissions from G. sulphureus and M. crassus mounds were significantly higher than surrounding soils in both dry and wet seasons. In contrast, T. propinquus and D. makhamensis emitted significantly CO2 less than the surrounding soils (Fig 6).
The average rate of CO2 emission from surrounding soils was 3.4 times higher in the wet season (7.83 ± 2.33 µmol CO2 m-2 s-1 mean ± SD) than the dry season (2.29 ± 0.89 µmol CO2m-2 s-1 mean ± SD). The relationship between the soil CO2 emissions, soil temperature, and soil moisture content aids in distinguishing seasonal variations. The CO2 emission rates from surrounding soils were positively correlated with soil moisture contents. (Pearson correlation,r = 0.804, P < 0.001) (Fig 7). The highest CO2 emission rates (more than 10 µmol CO2 m-2 s-1) were found at around 10 to 19% of the soil moisture content. While the relationship between soil temperature and surrounding soil CO2 emission was not significant (Pearson correlation, r = -0.024, P = 0.768). The soil temperature had limited variation from 21.8 to 27.5 °C.