Geology drives the spatial patterning and structure of termite mounds in an African savanna

Abstract

Citation: Muvengwi, J, AB Davies, F Parrini, and ETF Witkowski. 2018. Geology drives the spatial patterning and structure of termite mounds in an African savanna. Ecosphere 9(3):e02148. 10.1002/ecs2.2148Abstract. Termite mounds perform important roles in savanna ecosystems, generating heterogeneity and influencing ecosystem processes across multiple trophic levels. However, the influence the environment and neighboring termite colonies have on mound spatial patterning and structure is poorly understood, despite the profound implications such dynamics can have on ecosystems. To better understand these drivers, we mapped the spatial distribution and size of active and inactive Macrotermes mounds in eight 1-km 2 plots on contrasting geologies, nutrient-rich granite and nutrient-poor basalt, in a semi-arid Zimbabwean savanna. Although mound density was not significantly different between basalt (5.5 mounds/ha) and granite (6.1 mounds/ha), termite mound structural attributes and spatial distribution patterns varied greatly between geologies. Mound size distributions differed between the geologies and mounds were 2.6 times taller and 3.9 times wider and had 15 times greater lateral surface area on granite. Subsequently, 6% of the total landscape was covered by mounds on granite compared with only 0.4% on basalt. On granite, large mounds exhibited significant over-dispersion at scales below 30 m, signifying density-dependent thinning. Furthermore, small mounds were clustered around large mounds, likely a result of the budding of new colonies comprising fully fledged castes less vulnerable to competition. In contrast, random patterning was evident on comparably homogenous basalt. Our results demonstrate the powerful influence geological substrate has on mound spatial patterning and structure, suggesting that the importance of termite mounds for ecosystem functioning is more pronounced on nutrient-poor granitic substrates than basalts because of the pronounced over-dispersion, which maximizes mound production per unit area, and much larger mound sizes here.

Termite mound density and distribution patterns across three land‐use types in the Vhembe District of the Limpopo Province, South Africa

“…(1999) and Muvengwi et al. (2018) in Gonarezhou National Park where densities of 0.73/ha and 6.1/ha, respectively, were recorded on granite landscape zones. However, the Macrotermes mound densities from this study are similar to those reported from the natural vegetation by Debelo and Degaga (2014) in the Central Rift Valley of Ethiopia (9.6/moundsha) and Boga et al.…”

“…The distribution and density of termite mounds in an area is influenced by the landscape, termite species, mound activity status, size and ages of colonies (Davies et al, 2014;Grohmann, Oldeland, Stoyan, & Linsenmair, 2010;Korb & Linsenmair, 2001a;Levick et al, 2010;Meyer, Braack, Biggs, & Ebersohn, 1999;Muvengwi, Davies, Parrini, & Witkowski, 2018). Meyer et al (1999) in a study on the mound distribution in a pristine natural area in the Vhembe District, northern Kruger National Park, found that soil type, geography and termite species influenced mound densities.…”

“…The distribution and density of termite mounds in an area is influenced by the landscape, termite species, mound activity status, size and ages of colonies (Davies et al., 2014; Grohmann, Oldeland, Stoyan, & Linsenmair, 2010; Korb & Linsenmair, 2001a; Levick et al., 2010; Meyer, Braack, Biggs, & Ebersohn, 1999; Muvengwi, Davies, Parrini, & Witkowski, 2018). Meyer et al.…”

Environmental controls on Landsat‐derived phenoregions across an East African megatransect

“…Future work could include consideration of other environmental control variables or metrics such as the Compound Topographic Index (Marthews et al 2015) or a combination of variables that can be used to indicate moisture availability or other soil characteristics. Geologic heterogeneity influences vegetation (Cleverly et al 2016, Githumbi et al 2018, Muvengwi et al 2018), so being able to statistically show the impact of geology and geology on variables such as soil moisture at fine resolution could improve inference on phenoregion assignment. This study could also be expanded by continuing the analysis on other national parks in East Africa along the megatransect.…”

Growth, death, and resource competition in sessile organisms

“…In Fig. 1 , we show a small sample from such diversity, including fairy circles in semiarid environments ( 1 ), regular and random tiling of termite mounds ( 2 , 3 ), and more randomly spaced ant nests and trees ( 4 , 5 ). This variation is not limited to between taxa but also varies between different plots in the same region.…”