Field experiments
Five dominant species of the epigeal mound-building of non-fungus growing termites were selected for this study, namelyDicuspiditermes makhamensis, Globitermes sulphureus, Microcerotermes crassus, Termes comis, and Termes propinquus . Mound characteristic (e.g. population colony) of the non-fungus growing termites in each species had been preliminarily observed by a cross-section. Morphological characters of termite soldiers and the shape of their mounds were observed (Fig 2).
The five mounds of each termite species were randomly selected with a distance greater than 5 m between each mound. The mound sizes were measured for the height (base to the top) and circular length of the bottom. Three to five PVC collars (10 cm in diameter and ca. 3 cm in height) were placed at the mound and surrounding soils 10 to 30 cm from the mound at least one day before the measurement to avoid the disturbance of soil activities (Fig 3). The CO2emissions of each mound was measured by using a portable infrared gas analyzer (IRGA, EGM-4, PP Systems, Hitchin, UK) with a closed soil CO2 efflux chamber (SRC-1, PP Systems) (10 cm diameter) one time in October 2015 (wet season) and January 2016 (dry season).
After CO2 measurement, soil temperature and soil moisture content of the surrounding soils were measured immediately around each PVC collar at about 10 cm depth with a digital thermometer waterproof probe (type H-1 and H-2, Shinwa Co., Ltd., Japan) and soil moisture sensor (SM150, Delta-T Devices Ltd., Cambridge, UK), respectively. However, soil temperature and soil moisture content of the mounds were not measured because to avoid disturbing mound and termite activity. All measurements began from 9:00 am to 6:00 pm (3 to 5 minutes per location) in the day without rain.