Soil particle accumulation in termite (Macrotermes bellicosus) mounds and the implications for soil particle dynamics in a tropical savanna Ultisol

Abstract

This study investigated the influence of moundbuilding termites on soil particle dynamics on the land surface and in soil-forming processes by examining the amount of soil particles in mound structures of Macrotermes bellicosus in a highly weathered Ultisol of tropical savanna. Soil particle turnover via the mounds was estimated using particle stock data and soil turnover data from previous studies. A 4-ha study plot with six mounds of relatively uniform shape and size was investigated. Soil mass constituting the mounds was 6,166 ± 1,581 kg mound À1 within which the mound wall and nest body accounted for 5,002 ± 1,289 and 1,164 ± 293 kg, respectively. The mound wall contained a significantly larger amount of clay (252 ± 9.97 g kg À1 ) balanced with a lower sand content (676 ± 26.5 g kg À1 ) than in the adjacent surface (Ap1) horizon, (46.4 ± 12.8 g clay kg À1 ; 866 ± 83.2 g sand kg À1 ); the nest body had much higher clay content (559 ± 51.0 g kg À1 ) but less sand (285 ± 79.2 g kg À1 ) than the mound wall. As a result, the mounds of M. bellicosus accumulated clay of 2,874 ± 781 kg ha À1 (corresponding to 2.52% of clay stock in the Ap1 horizon) along with an estimated clay turnover rate of 169 kg ha À1 year À1 . These findings suggest a positive feedback effect from termite mound-building activity on soil particle dynamics in tropical savanna ecosystems: M. bellicosus preferentially use subsoil material for mound construction, resulting in relocation of illuvial clay in the subsoil to the land surface where clay eluviation from the surface soil and its illuviation in the subsoil are major soil-forming processes.

The influence of the mound-building termite (Macrotermes bellicosus) on soil clay mineralogy

“…4) in spite of the large disparity in particlesize distribution (Table 1). We therefore concluded that the mound-building activity of M. bellicosus affects soil clay mineralogical composition as a result of their preferential collection of fine soil particles ( 53 m) (Abe et al 2009b(Abe et al , 2012. These findings may indicate that clay mineralogy is not linked to the ecological requirements of M. bellicosus, although our previous studies (Abe et al, 2009a(Abe et al, , 2009b suggest that soil particle selection by M. bellicosus was based on the mound structures built, which had different ecological requirements such as water-holding capacity and structural stability (Jouquet et al 2002a(Jouquet et al , 2007.…”

“…In particular, species of the genus Macrotermes include mound-builders that construct large epigeal nests and extensive underground gallery systems and have a major influence on soil properties and functions throughout the tropics and subtropics ). Non-random mineral selection and soil-particle transport by termites during the construction and maintenance of mounds and galleries has implications for soil formation (Abe et al 2011(Abe et al , 2012. Although changes in the physical, chemical and biological characteristics of soils handled by termites have been extensively documented (Lobry de Bruyn andConacher 1990, Black andOkwakol 1997), only a limited number of researchers have addressed soil mineralogical alteration as a result of termite activity.…”

Nutrient storage in termite (Macrotermes bellicosus) mounds and the implications for nutrient dynamics in a tropical savanna Ultisol

“…This plot was chosen as representative of the study area in terms of size (3.7 AE 0.4 m in height, 2.4 AE 0.2 m in basal diameter, 5.7 AE 1.5 m 3 estimated volume) and density (1.5 mounds ha À1 ) of M. bellicosus mounds (Abe et al 2012). All mounds of M. bellicosus at the study plot appeared to have reached their maximum size (based on the state of nest mutuality observed) (Abe et al 2012). Few epigeal mounds of any termite species other than M. bellicosus were observed in the plot.…”

“…Nest body indicates the main body of the hive (including the royal chamber and baseplate) but does not include the pillars. This demarcation of the mound structures is reasonable, because soil characteristics vary considerably between the mound wall and the nest body (Abe et al 2009a(Abe et al , 2009bAbe et al 2012). The mound wall and nest body were individually weighed using a counterbalance prior to sampling.…”

“…, respectively (Abe et al 2012). The soil mass accumulated in M bellicosus mounds amounted to 0.26% of that stored in the topmost (Ap1) horizon (Abe et al 2012).…”