Mound Volume Research Articles

Studies on a population of large termite mounds in Uganda

Abstract Two study‐sites near Kampala were mapped and all of the termite mounds within them were measured. Changes were recorded in the three succeeding years. A method was developed for estimating mound volumes from height and diameter. Macrotermes bellicosus mounds reached a volume of about 2.4 m3 in 3 years after which they grew more slowly to a maximum from 4 to 6 m3. Growth in volume during the first 3 years was approximately linear and its rate did not vary seasonally, probably because growth is related to temperature which was nearly constant throughout the year. M.bellicosus mounds had an average length of life of about 10 years, although colonies survived on average only 4 years. The corresponding figures for Pseudacanthotermes spp. were 5 and 2 1/2 years. Some mounds were recolonized after the death of the original colony. Fresh earth was brought up at a minimum rate of about 10 m3 ha‐1 yr‐1 but more was lost by erosion and destruction and the populations of mounds were decreasing. The number of ventilation shafts in M.bellicosus mounds increased with the volume of the mound. Many mounds, both dead and alive, supported vegetation. Local opinion is that Pseudacanthotermes are harmless but M.bellicosus is regarded as a pest and attempts are made to destroy its mounds.

Ant (Formica exsectoides) Pedoturbation in a Forest Soil

AbstractTwenty‐five active mounds of the common eastern moundbuilding ant (Formica exsectoides) had an average height of 0.37 m and basal diameter of 1.1 m in a long, narrow neverplowed clearing of 1,040 m2 on the edge of a woodland in southern Wisconsin. The mound volume ranged from 0.01 to 0.6 m3 and averaged 0.13 m3. The ant nests, extending at least 160 cm below the soil surface occupied 1.9% of the area of the surface of a Typic Hapludalf (Gray‐Brown Podzolic), Dubuque silt loam, formed in thin loess over reddish cherty clayey residuum on dolomitic limestone. Mounds were virtually bare and were largely composed of silty clay. Detailed studies were made of a soil profile through a large mound and of an intermound soil profile nearby. Calculations indicated that the ants have moved to the surface the equivalent of 1.25% of a plow layer or 2,500 kg of soil (dry wt) per 1,040 m2 and in the process have reduced the bulk density of the material from 1.5 to 0.8 g/cm3 and increased the contents of available nutrients in the soil. Voids 0.2 to 2.3 cm in diameter, on the average occupied 20% by volume of the mound and about 10% of the buried A horizons. The mound contained about 50% silt, 46% clay, 4% sand; 4% free iron oxides, and 3% organic matter. Corresponding figures for the A2 and IIB23 horizons of the Dubuque are: 78, 18, 4; 2 and 3; 15, 83, 2; 6 and 0.3. Disturbance of soil profiles by this species of ant is restricted to small areas, apparently because colonies are established and mounds developed only in temporary openings in forests.