Termite-induced heterogeneity in African savanna vegetation: mechanisms and patterns

Abstract

Objectives: To (1) assess the strength of evidence for the role of termites in vegetation heterogeneity in African savannas, and (2) identify the mechanisms by which termites induce such heterogeneity. Location: African savannas. Methods: We conducted a review of the literature, a meta-analysis and qualitative systems analysis to identify mechanisms to explain the observed patterns. Results: The review provided evidence for termiteinduced heterogeneity in floristic composition and vegetation patterning in savannas across Africa. Termites induced vegetation heterogeneity directly or indirectly through their nest-building and foraging activities, associated nutrient cycling and their interaction with mammalian herbivores and fire. The literature reviewed indicated that termite mounds essentially act as islands of fertility, which are responsible for ecosystem-level spatial heterogeneity in savannas. This was supported by the meta-analysis, which demonstrated that mounds of Ancistrotermes, Macrotermes, Odontotermes (family Macrotermitinae), Cubitermes (family Termitinae) and Trinervitermes (Nasutitermitinae) are significantly enriched in clay (75%), carbon (16%), total nitrogen (42%), calcium (232%), potassium (306%) and magnesium (154%) compared to the surrounding savanna soil. Conclusions: Termite activity is one of the major factors that induce vegetation patterning in African savannas. The implications of this are discussed and research questions for future studies and modelling efforts are indicated.

Long-term effects of Macrotermes termites, herbivores and annual early fire on woody undergrowth community in Sudanian woodland, Burkina Faso

“…In addition, termites have the ability to draw water from afar a field toward their mounds, thereby improving soil moisture status of their mounds (Turner et al, 2006). As a result, termitaria are safe sites for regeneration of woody plants (Traoré et al, 2008a), that support a greater diversity of plant community compared with surrounding areas and induce local-scale vegetation mosaic in an otherwise uniform savanna landscape (Adekayode and Ogunkoya 2009;Jouquet et al, 2004;Moe et al, 2009a;Okullo and Moe, 2012;Sileshi et al, 2010). Thus, they are considered as biodiversity reservoir (Choosai et al, 2009;Duponnois et al, 2005;Jouquet et al, 2005).…”

“…They modify soil physicochemical and microbial properties through foraging and processing of plant materials, thereby creating "nutrient reservoirs" compared with the surrounding savanna soil (Holt and Lepage, 2000;Joseph et al, 2012;Jouquet et al, 2011;Seymour et al, 2014;Sileshi et al, 2010). In addition, termites have the ability to draw water from afar a field toward their mounds, thereby improving soil moisture status of their mounds (Turner et al, 2006).…”

Modeling Vegetation Lifeforms Abundance based on <i>Epigeal Termitaria</i> Physiography and Altitude in Tropical Savannah of Katolo Sub-Location, Kisumu County

“…In order to explain the moisture retention of soils with distance from termite mound, a regression model was developed which showed declining moisture retention ability of soil with distance from the base of termite mound [11] as given in Equation (3) Accordingly, there has been no attempt in literature to model vegetation lifeforms on termite mounds using various physiographic characteristics of the mounds as predictor variables. Physiography of a termite mound (basal radius and height) as well as its altitudinal location has been surveyed in several studies but none has attempted to use them in explaining abundance of vegetation lifeforms.…”

Importance of bird seed dispersal in the development of characteristic vegetation on termite mounds in north-eastern Namibia

“…Termite mounds support more diverse woody plant assemblages (Loveridge andMoe 2004, Traore et al 2008) and herbaceous layers (Moe et al 2009, Okullo andMoe 2012a, b) than surrounding tracts of savanna. Termite-induced resource heterogeneity, such as soil composition (Sileshi et al 2010, Erpenbach et al 2013) and soil moisture , Konate et al 1999, induces this vegetation pattern. Spatial heterogeneity is also a factor, in that termite mounds act as refugia for plants from fire (Moe et al 2009, Joseph et al 2013) and flooding , Bloesch 2008.…”