Termite mound soil properties in West Bengal, India

Highlights

• Properties of termite mounds are directly proportional to the surrounding surface soil.

• Termites significantly affect the physiochemical properties of soil

• Mound soils are physio chemically and morphologically distinct from surrounding surface soil.

• Termite mounds have greater nutrient concentration than surrounding surface soil.

• Height, mass of material, abundance and regeneration rate of termite mounds are higher in dense vegetation.

Abstract

Termites are ecosystem engineers, they play a major role in the biotransformation and modification of soil physicochemical and morphological properties. This study was conducted to evaluate the explored and compared physicochemical and morphological characteristics of soil between termite mounds and surrounding surface soil. Therefore, this study, especially emphasizes the impacts of the mound soil on the surrounding surface soil properties and also to find out the difference between the mound soil properties and surrounding surface soil properties at different soil depth, and characteristic of termite mounds. This study unveils that mound soil properties are directly proportional to the surrounding surface soil properties except for porosity and dispersion ratio. But mound soil properties are not significantly affecting all surface soil properties. The termites have a significant role to change soil physicochemical and morphological properties and there is a significant difference in soil physicochemical properties between mound and surrounding surface soil. However, relatively greater bulk density, clay content, soil pH, organic carbon, nitrogen, exchangeable calcium, exchangeable magnesium, exchangeable sodium, total exchangeable base cations and cation exchange capacity in mound soil than surrounding surface soil. But the relatively lesser value of porosity, dispersion ratio, exchangeable potassium, phosphorus, exchangeable acidity, and C: N ratio is found in mound soil than surrounding surface soil. Conical shaped mounds have greater nutrient concentration than surrounding surface soil. It also highlighted that most of the termite mound consists of trees and bushes containing 8–21 hole or chamber. The termite mounds have granular structure and particle shape are rounded to subrounded, which make them different from surrounding areas. This study suggests and statistically prove that termites have a significant effect on soil properties, they produce physicochemically more quality soil and have an influence on surrounding soil properties.

Introduction

Termite mounds, a micro landform feature generally found in the lateritic landscapes of the tropical and subtropical regions (Dangerfield et al., 1998; Levick et al., 2010). Termite mounds have distinct morphology compared with the surrounding topsoil (de BRUYN and Conacher, 1990; Abe et al., 2009). Generally, termite mounds are stable, erosion resistant, (Léonard and Rajot, 2001; Jouquet et al., 2004; Ackerman et al., 2007), and increase nutrient concentration and mineral reserves (Kebede, 2004). Diets of termites are based on wood, grasses, litter, and nutrient-rich soil, so most of the termite's nest grows on wood soil interface and high biomass regions (Eggleton et al., 1996; Mora et al., 2006). Termite mound's growth, abundance and volume vary regionally due to variation in climate, vegetation cover, soil properties, biomass abundance, slope and groundwater depth etc. (Gathorne-Hardy and Eggleton, 2001; Cancello et al., 2014; Davies et al., 2014; Jamilu Bala Ahmed et al., 2019). Biological agents like termites are important for pedological processes hence are termed as bioengineers (Holt and Lepage, 2000); Millogo et al., 2011; Whitford and Eldridge, 2013; Jouquet et al., 2016). Termites have great impact on soil properties including redistribution of soil particles with nutrient and minerals, nest building, repacking and cementing, feeding activity, interaction with the organism, organic matter (OM) decomposition, nutrient recycling, foraging behaviour and decaying (Holt and Lepage, 2000). They also effects on soil properties by their chemical secretions (Prestwich, 1979; Hanus et al., 2010) and by bringing up subsoil to the soil surface for construction of mounds (Lee and Wood, 1971; Holt and Lepage, 2000; Jouquet et al., 2011; Mujinya et al., 2014). Termites are the most important soil fauna which help to modify physicochemical properties of soil (de BRUYN and Conacher, 1990; Lee and Foster, 1991; Holt and Lepage, 2000; Millogo et al., 2011; Jouquet et al., 2011; Rückamp et al., 2012; Jouquet et al., 2016; Lavelle et al., 2016), and built stable, microstructural and morphological features which are distinct from surrounding soil (Lee and Wood, 1971; Eschenbrenner, 1986; Lal et al., 1992; Dangerfield et al., 1998; Jungerius et al., 1999; Turner, 2000; Sarcinelli et al., 2009). The effects of termites are not limited to their living area, they also effect inside the mound and surrounding foraging area (Rückamp et al., 2012). Quantifying the distribution of termite mounds, regeneration, volume and mass of mound provide useful information on nutrient and minerals, the good productive capacity of the soil and groundwater resource (Turner, 2000; Kaschuk et al., 2006; Ackerman et al., 2007; Mège and Rango, 2010). Research on termite mounds historically concentrated on physicochemical and geomorphological properties (Lee and Wood, 1971; Wood et al., 1983; Abe et al., 2009; Dowuona et al., 2012), and their stability, erodibility, runoff, infiltration rate (Léonard and Rajot, 2001; Jouquet et al., 2012) and physicochemical properties of termite's mound (as a whole) in relation to adjacent topsoil (Hesse, 1955; Brian, 1978; Asawalam et al., 1999; López-Hernández, 2001; Jouquet et al., 2005; Ackerman et al., 2007; Kawaguchi and Nishi, 2007; Asawalam and Johnson, 2007; Jiménez et al., 2008; Okullo and Moe, 2012). As termites bring up soil not only from topsoil but also from subsoil (Jouquet et al., 2002),mound soils are affected by rainfall and thus eroded materials may also affect associated surface soils surrounding the mounds (Arshad, 1982; Lal et al., 1992).This study emphasizes the effect of the mound soil properties on the surrounding surface soil properties and makes a comparison between physicochemical properties of mound soil (at different depth) and surrounding surface soil (non-mound affected soil at different depth). The hypothesis was whether there is significant difference between mound soil properties and surrounding surface soil properties and the mound soil properties that may affect the surrounding surface soil properties. Therefore, the aims of this study were 1) to assess the effects of the mound soil properties on the surrounding surface soil properties, 2) to find out the difference between termite mound and surrounding surface soil properties in the study area and 3) to analyse the characteristics of mounds with their abundance, mass of materials (mass of termite mounds) and rate of regeneration.