Environmental changes are threatening current and future food security. In this context, it is imperative to design agricultural systems that are resilient to increasing frequent climate shocks, ...losses in biodiversity and soil fertility and to increasing demand from our societies because of population growth and consumption patterns. The emergence of sustainability science reminds us that soil management cannot be successfully approached by the independent actions of individual categories of actors, namely soil researchers or agronomists. Therefore, we advocate for more holistic and transdisciplinary research that takes into account the social, cultural, environmental and economic impacts of agricultural practices. Using examples of agricultural practices that aim to use the activity of termites to improve the services delivered by ecosystems (e.g. the Zai system), rather than considering them pests and trying to eradicate them from lands, we discuss the interest of traditional agricultural practices as sources of inspiration for soil scientists and for the identification of tomorrow's agricultural practices.
Soil macroporosity is a highly dynamic feature driven by numerous physical and biological processes, of which bioturbation, the movement of water in soil and swelling and shrinking cycles are the ...main processes. To date, the interaction between these factors, especially how galleries produced by soil fauna respond to rainwater percolation and wetting–drying (WD) cycles, remains poorly known. A laboratory experiment was carried out to expose soil macrofauna galleries to three different consecutive water flow (simulated rain events of 50, 80 and 110 mm h−1 in 1 h) and drying cycles in a clayey soil. X‐ray computed tomography and image analyses were used prior to and after each exposure to assess the water stabilities of galleries and created cracks. The 3D properties (volume, diameter, specific surface area and density) of the galleries produced by termites or ants were not statistically influenced by rainwater percolation and WD cycles, suggesting a high water stability and life expectancy under natural conditions. Conversely, the crack water stability was variable and was probably influenced by the presence of galleries in the same area. This study emphasizes that the macropores created by soil fauna may persist in clayey soil and that there is a need to better understand how cracks and galleries interact.
Highlights
Evolution of soil porosity was studied by X‐ray computed tomography.
Galleries made by soil fauna were stable and resist to wetting and drying cycles.
Cracks were highly variable and were highly influenced by wetting and drying cycles.
No relationship could be evidenced between galleries and cracks.
This study aimed to understand the relationship between termite foraging activity and the ecological benefits derived from their activity in soil dynamics and water infiltration. A field study was ...carried out for six months, between pre-wet and wet seasons, with different food baits (elephant dung, Acacia auriculiformis leaves, twigs and leaves of Lantana camara as well as Ficus religiosa, Pterocarpus marsupium, Prosopis juliflora, Michelia champaca, Azadirachta indica and Hevea brasiliensis wood stakes) installed on the soil surface in a semi-deciduous forest in southern India. At the end of the experiment we determined bait consumption, water infiltration rate in soil, and the amount of soil sheetings covering the different baits. The initial infiltration rates under the baits were compared to those at the end of the experiment. Three termite species, Odontotermes obesus, O. feae and Microtermes obesi, were found associated with some of the baits in the study area. Among the different baits, elephant dung and Acacia leaves were the most preferred and a positive relationship was observed between the quantity of soil sheetings and the bait consumption rate. Termite preference for elephant dung and Acacia leaves was also associated with higher water infiltration rates. However, this difference was only significant at the beginning of the experiment and no significant difference was measured once the steady state was reached. In conclusion, we showed that resource quality was of primary importance for soil sheeting production but that the influence of termites on water infiltration remained limited, most likely because of the low stability of their tunnels in the soil.
Soil bioturbation is associated with the production of soil macropores that influence numerous ecological functions such as those associated with water infiltration and the generation of runoff ...water. This impact is especially important on sloping lands in the tropics that are highly susceptible to erosion. In this study, we questioned the influence of soil biodiversity on soil macropore properties (> 20 mm3) and saturated hydraulic conductivity (Ksat) on sloping land in northern Vietnam. Biostructures found at the soil surface (casts, sheetings and soil excavated on the ground) were used to identify areas colonized either by earthworms, termites or dung beetles, respectively. The influence of soil macrofauna on Ksat was measured in situ using the Beerkan method below bioturbated zones and compared to the surrounding soil without visible biostructures at the soil surface. Undisturbed soil columns were afterwards sampled and scanned by X-ray computed tomography (X-CT). Properties of macropores below each biostructure depicted a large variability, revealing the complexity of the macropore network. Further, galleries made by termites, dung beetles and earthworms were manually isolated from the rest of macroporosity. Galleries made by beetles, termites and earthworms were clearly differentiated on the basis of their diameter, verticality, sphericity, tortuosity, length and number of branches and the fraction of galleries in the top part of the column and. Ksat was most increased by dung beetles (45-fold), then by termites (30-fold) and to a lesser extent by earthworms (16-fold). Relationships between total macropore properties and Ksat showed that the most important properties explaining Ksat were (i) the volume of percolating macropores, (ii) the diameter, (iii) the critical macropore diameter and (iv) the number of macropores. In conclusion, this study confirmed not only the interest in using X-CT for the quantification of macroporosity but also the absence of a clear relationship between aboveground biostructures and macropore properties and functional impacts.
Termites are undoubtedly amongst the most important soil macroinvertebrate decomposers in semi-arid environments in India. However, in this specific type of environment, the influence of termite ...foraging activity on soil functioning remains unexplored. Therefore, this study examines the link between the quality of litter and the functional impact of termite feeding preferences on soil properties and soil hydraulic conductivity in a deciduous forest in southern India. Different organic resources (elephant dung: "ED", elephant grass: "EG", acacia leaves: "AL" and layers of cardboard: "CB") were applied on repacked soil cores. ED appeared to be the most attractive resource to
, leading to a larger amount of soil sheeting (i.e., the soil used by termites for covering the litter they consume), more numerous and larger holes in the ground and a lower soil bulk density. As a consequence, ED increased the soil hydraulic conductivity (4-fold) compared with the control soil. Thus, this study highlights that the more
prefers a substrate, the more this species impacts soil dynamics and water infiltration in the soil. This study also shows that ED can be used as an efficient substrate for accelerating the infiltration of water in southern-Indian soils, mainly through the production of galleries that are open on the soil surface, offering new perspectives on termite management in this environment.
In the tropics, termites and beetles are considered key soil bioturbators regarding their impacts on many ecosystem services. The aim of this study was to compare the functional impacts of these two ...soil engineers in a seasonally dry tropical forest in southern India. The soil excavated by dung beetles and termite sheeting found at the soil surface were sampled and compared to the surrounding topsoil environment. We showed that soil sheeting had very similar soil particle sizes and C content as the surrounding topsoil while the soil excavated by beetles was enriched in C and gravels in comparison with the topsoil. Bioturbation by dung beetles was also associated with the production of vertical tunnels that significantly decreased soil bulk density and constituted a preferential flow path for water to infiltrate (37-fold increase in comparison with the surrounding topsoil). Termite activity was also associated with the production of macropores. However, termite galleries were narrower and less vertical than dung beetle macropores, consequently leading to a positive but rather limited impact on the water hydraulic conductivity (Ksat) in comparison with that of dung beetles (i.e. from 2 to 8-fold increase). In conclusion, this study showed that soil engineers have different bioturbation impacts, dung beetles having locally a larger impact on soil dynamics and properties than termites. More research is now needed to understand the consequences of these bioturbations on the fate of C in soil and on water dynamics at larger scales.
•We compare the functional impact of termites and beetles on soil and water dynamics.•Termite sheetings have similar properties than the topsoil.•Soil excavated by beetles was enriched in gravels and C.•Soil macroporosity made by beetles and termites were studied using X-ray CT.•Beetles and termites’ burrows impact differently soil macroporosity.•Results suggest different impact of termites and beetles on soil and water dynamics.
Termites are considered soil engineers and key bioturbators in tropical and subtropical soils. A large number of studies have described the specific properties of the aboveground mounds that termites ...construct to protect their colonies from environmental hazards. However, there is a paucity of information on properties of soil sheetings; more temporary but often extensive structures are covering over or inserted within substrates on the ground such as leaves and woody materials or components of arboreal runways. Such sheetings are conspicuously produced not only by the Macrotermitinae but also by many other unrelated taxa. Here, we review the available literature and discuss (i) the relationship between rainfall and soil sheeting production and (ii) how termites affect the clay and C contents in soil sheetings. This reveals that sheeting production is highly variable and site specific. We also found that soil sheetings are always enriched in clay, but their impacts on soil C content are variable and related to the C content of the parent soil and to the quality of the substrates consumed by termites.
•Termites produce subterranean galleries for collecting litter and dung in vertisols.•Termite activity increases Ksat in comparison with the surrounding soil.•Galleries were found beyond 3 cm of ...depth.•C content in soil sheetings was reduced in comparison with the surrounding topsoil.•Termite produce unstable galleries.
In the tropics, termites are key litter decomposers and soil bioturbators. Termite foraging activity involves the production of sheetings and galleries that influence the physical, chemical and hydraulic properties of soils. The functional impacts of these biogenic structures and biopores have been acknowledged for a long time in soils dominated by 1:1 minerals. Less is known, however, on their functional impacts in soils dominated by 2:1 minerals, such as vertisol which represent 22% of the land surface in India. Therefore, an experiment was carried out in a vertisol in southern India where elephant (Elephas maximus) dung pats (ED) and Lantana camara twigs (LT) were applied on the ground and protected (+) or not (−) from termite activity. Termite activity was only measured below ED−, showing a clear preference for organic matter derived from elephant dung. Soil sheetings had similar properties to the surrounding topsoil, with the exception of their C content that was reduced. This result raised the question of the origin of the soil used by termites for covering ED. ED− was also associated with the presence of effective macropores up to 5 cm depth and a significant increase in water hydraulic conductivity (12-fold). However, the utilization of the coefficient of linear extensibility showed that these galleries were unstable and most likely short-lived. In conclusion, this study confirmed that the structure of soils dominated by 2:1 minerals is mainly controlled by physical processes (i.e., the shrinking and swelling of soils). This study also stresses the need to better understand the dynamic of termite galleries in soil and to quantify the origin and fate of organic matter in soil sheetings.
This communication assesses advances in our knowledge of the beneficial influences of termites on ecosystem functioning and services. Termites are amongst the main macroinvertebrate decomposers in ...arid and semi-arid environments and exert additional impacts through the creation of biostructures (mounds, galleries, sheetings, etc.) with different soil physical and chemical properties. Unfortunately, the positive ‘or bright’ role of termites is often overshadowed by their dark side, i.e. their status as pests threatening agriculture in the tropics (635 vs. 164 articles referenced in WoS with termites and either pest or ecosystem engineer as keywords. Source: WoS, April 2019).
Termite impacts on soil properties and water dynamics can be differentiated at four different scales: (i) at the landscape scale, where termites act as heterogeneity drivers; (ii) at the soil profile scale, where termites act as soil bioturbators; (iii) at the aggregate scale, where they act as aggregate reorganizers; (iv) and last, at the clay mineral scale, where they can act as weathering agents 1.
In this communication, two examples of ecosystem services provided by termites are given.
The first describes the positive impact of termites on water infiltration and nutrient guidance at small scale through the production of foraging galleries in soil 2 and how this activity can be used to improve agro-ecosystem functioning in arid and semi-arid environments 3.
The second example deals with the construction of mounds and sheeting by termites in “natural” environments 4 and how these “patches of biodiversity and fertility” can be used in the lower Mekong Basin to reduce food insecurity and to provide a better access to health 5 (Fig. 1).
Finally, the perception of termite mounds in Southern Indian rural environments (Fig. 2) is discussed and used as example of the cultural services that can be provided by termites in some circumstances. The story of Valmiki, the author of the Ramayana, is explained and used as a parable for highlighting the interconnection between the “bright” and “dark” sides of termites, and more generally that to get the bright we also need the dark.
Where do South-Indian termite mound soils come from? Jouquet, Pascal; Caner, Laurent; Bottinelli, Nicolas ...
Applied soil ecology : a section of Agriculture, ecosystems & environment,
September 2017, 2017-09-00, 2017-09, Letnik:
117-118
Journal Article
Recenzirano
•PLSR models were used to measure the origin of the soil used by termites.•The origin of termite mound soil is site and species specific.•Cathedral mound soils are collected at 100 and 50cm deep in ...ferralsol and vertisol.•Lenticular mound soils are collected at 30 and 60cm deep in ferralsol and vertisol.
This study investigated the origin of the soil termites used to build their above-ground mounds. Termite mounds were surveyed in a ferralsol and a vertisol in a dry deciduous forest in Karnataka, southern India. In these environments, two types of above-ground termite mounds are observed which we describe here as CATHEDRAL and LENTICULAR mounds. Partial Least Squares Regression models (PLSR) were computed from the physical and chemical properties of the soil sampled down to 4 and 2.5m in the ferralsol and vertisol, respectively. Soils from CATHEDRAL mounds had the same signatures as soils collected at approximately 100 and 50cm deep in the ferralsol and vertisol, respectively. On the other hand, soil from LENTICULAR mounds had the same signature as soil sampled at 30 and 60cm deep in the ferralsol and vertisol, respectively. In conclusion, this study highlighted that the source of the soil termites use to build their mounds can be soil (ferralsol vs vertisol) and species (CATHEDRAL vs LENTICULAR) specific. In light of these findings, we conclude that the impact of CATHEDRAL mounds on soil dynamics appears to be smaller than that of LENTICULAR mounds in terms of soil volume at the landscape scale but it is higher in terms of soil translocation from deeper soil layers to the surface.
PDF
