Mound Wall Research Articles

Hydrological characteristics and functions of termite mounds in areas with clear dry and rainy seasons

Many species of fungus-feeding termites collectively build massive mound structures that enclose a network of broad tunnels to provide a controlled microclimate in which to raise fungus and brood by managing heat, humidity and respiratory gas exchange. However, the mechanisms by which termites regulate the water content inside the termite mounds are currently unknown in regions in southern Asia with distinctive dry and wet seasons. Here, we investigated the spatio-temporal variations in the water content in the mound structures of O. yunnanensis and then used the dye tracer infiltration method to determine how the existing mound structure and/or termite activities contribute to regulating the moisture inside the mounds. We found that the outer walls could act as a shield to prevent water infiltration into the mound, and the network of broad tunnels could act as a drainage system to eliminate excess water when the outer walls are compromised during heavy rainfall events in the rainy season. Furthermore, the termites could repair or reshape the mound to control water flows inside the mound. During the dry season, the high-density mound wall effectively reduced evaporation, and the termites could actively transport water to maintain favourable microclimatic conditions. Our results demonstrated the internal water spatio-temporal distribution in the mound and its regulation mechanisms and provided clues for understanding mound morphogenesis and the organization of insect societies.

Optimized design for heavy mound venturi

The venturi scrubber is one of the most efficient gas cleaning devices for removal of contaminating particles in industrial flue-gas purification processes. The velocity of the gas entering the scrubber is one of the key factors influencing its dust-removal efficiency. In this study, the shapes of the heavy mound and tube wall are optimized, allowing the girth area to become linearly adjustable. The resulting uniformity of velocity distribution is verified numerically.

Rainfall and soil properties influence termite mound abundance and height: A case study with Odontotermes obesus (Macrotermitinae) mounds in the Indian Western Ghats forests

Several fungus-growing termite species build mounds, or termitaria, that are conspicuous features of African and Asian landscapes. Studies of the genus Macrotermes in Africa have established that their mounds provide an environment buffered against extremes of temperature and humidity, as well as protection from predators, and are correspondingly modified in composition. However, no studies are available in the specific context of the Asian continent where termite mounds are also abundant. Hence this study focused on the abundance and properties of mounds built by Odontotermes obesus in relation to rainfall and parent soil properties in southern Indian forests, in the Western Ghats area. Termite mound densities and sizes were measured in 18 forests along a rainfall gradient from 1160 to 3670mmyr−1. The C and clay contents were analyzed in soil samples collected from mounds and the surrounding topsoil. Mound numerical density was positively correlated with mound height and rainfall had a negative relationship with the abundance. Neither vegetation type nor or rainfall influenced the clay content in the mound walls but a positive linear relation was observed between the clay content in the termite mound wall and that in the surrounding topsoil environment, suggesting a rather low impact of termites on the clay content in the mound soil. The C content in mound walls depended mainly on how much clay the termites used. In conclusion, this study shows that the amount of rainfall affects the abundance of O. obesus mounds in India while the amount of clay in the surrounding topsoil determines mound soil properties.

Accumulation of free oxyhydroxides in termite (Macrotermes bellicosus (Smeathman)) mounds and the implications for their dynamics in an African savannah Ultisol

ABSTRACTThe present study aimed to assess the dynamics of oxyhydroxides via termite mounds in a tropical savannah of Central Nigeria, where the soils often contain oxyhydroxides as a major component of soil minerals. To this end, the quantities of oxyhydroxides stored in mounds built by Macrotermes bellicosus (Smeathman) were compared to those stored in surface (Ap1) soils, and their turnover rates were estimated. Both the mound wall and nest of M. bellicosus were enriched two- to 10-fold with acidified ammonium oxalate soluble iron (Feo) and aluminum (Alo) and dithionite-citrate-bicarbonate (DCB) soluble iron (Fed) and aluminum (Ald) relative to the adjacent surface soil horizon. These oxyhydroxide contents were positively correlated with the clay content (P < 0.05), suggesting that M. bellicosus preferentially used silicate clay-associated oxyhydroxides for mound construction. The Fed, Ald and DCB-soluble manganese (Mnd) preserved in the M. bellicosus mounds ran up to 112 ± 25.6, 5.72 ± 1.41 and 2.17 ± 0.68 kg ha−1, accounting for 1.91 ± 0.23%, 1.00 ± 0.60% and 0.35 ± 0.09% of the total amount stored in the surface soil horizon, respectively. Furthermore, the estimated turnover rates of Fed, Ald and Mnd were 6.6, 0.33 and 0.14 kg ha−1 year−1, respectively. These findings suggest that the mound-building termites significantly impacted the dynamics of free oxyhydroxides in an African savannah soil.

The influence of fungus-growing termites on soil macro and micro-aggregates stability varies with soil type

Termites are considered soil engineers due to their effects on soil properties in tropical ecosystems, which include the production of biogenic aggregates with different physical and chemical properties to the surrounding environment. How termites influence the dynamics of aggregates on the soil surface is still poorly understood. In this study, we sampled 50–250, 250–2000 and >2000μm soil aggregates from the wall of termite mound nests produced by Odontotermes obesus (Blattoidea, Macrotermitinae subfamily) in a Ferralsol and in a Vertisol in Southern India and analyzed their stability in water and to ultrasonic agitation. Our study shows that the influence of termites on the stability of soil aggregates varies depending on the properties of soil. The concentrations in C and N were lower in termite mound soils compared to the control soil aggregates in the Ferralsol for all the soil aggregate size fractions whereas in the Vertisol, the C and N contents were only lower in soil aggregates >2000μm (i.e., no significant difference for aggregates <2000μm). No difference in clay, silt or sand content was measured between the termite mound wall and the control soil. Soil aggregate stability was reduced for all size categories of aggregate in the Ferralsol but it was only reduced for soil macro-aggregates >250μm in the Vertisol. Since micro-aggregates <250μm are considered to predominantly protect soil organic matter in the long term pools, the impact of termites on C protection and nutrient cycling may be higher in Ferralsols than in Vertisols.

Influence of soil pedological properties on termite mound stability

This study investigated the influence of soil properties on the density and shape of epigeous fungus-growing termite nests in a dry deciduous forest in Karnataka, India. In this environment, Odontotermes obesus produces cathedral shaped mounds. Their density, shape (height and volume) and soil physicochemical properties were analyzed in ferralsol and vertisol environments. No significant difference was observed in O. obesus mound density (n=2.7moundha−1 on average in the vertisol and ferralsol areas). This study also showed that O. obesus has a limited effect on soil physical properties. No differences in soil particle size, pH, or the C:N ratio and base saturation were measured whereas the C and N contents were reduced and CEC was higher in termite nest soils in both environments. Clay mineralogical composition was also measured, and showed the presence of higher amounts of smectite clays in termite nest soils, which thus explained the increasing CEC despite the reduced C and N content. However, the main difference was the shape of the termite mounds. The degradation of the nests created a hillock of eroded soil at the base of termite mounds in the vertisol while only a thin layer of eroded soil was observed in the ferralsol. The increased degradation of termite mounds in the vertisol is explained by the presence of smectites (2:1 swelling clays), which confer macroscopic swelling and shrinking characteristics to the soil. Soil shrinkage during the dry season leads to the formation of deep cracks in the termite mounds that allow rain to rapidly penetrate inside the mound wall and then breakdown unstable aggregates. In conclusion, it appears that despite a similar abundance, termite mound properties depend to a large extent on the soil properties of their environments.

The effect of windthrow disturbances on biochemical and chemical soil properties in the northern mountainous forests of Iran

Land degradation as a result of wind (aeolian processes) is one of the most significant causes of soil loss in northern Iran. In order to gain a broader understanding of the specific effects of aeolian disturbance on soils in this region, research was conducted to evaluate soil microbial respiration and nitrogen mineralization in places where differences in microtopography occur due to the uprooting of trees by windthrow events, thereby causing variations in microtopography hereby referred to as “pit–mound positions”.A twenty-hectare study site situated within the Tarbiat Modares University Experimental Forest Station located in the Mazandaran province of northern Iran was chosen for this research, with thirty-four uprooted trees selected for detailed study. A classification of five microsites was developed to distinguish differences in microtopography in the immediate vicinity of these uprooted trees: mound top, mound wall, pit bottom, pit wall and closed canopy. Soil was sampled in the 0–15, 15–30 and 30–45cm depths at all microsites using a core soil sampler with an 81cm2 cross section. Soil reaction, organic carbon, total nitrogen, carbon-to-nitrogen ratio, moisture, abundance and biomass of earthworms, soil microbial respiration and net N mineralization for all samples were measured in the laboratory.Statistical comparisons revealed that the highest soil microbial respiration and net N-mineralization occurred in pit bottoms. Mound tops showed the lowest levels of soil microbial respiration and net N mineralization. Measurements of soil microbial respiration and net N mineralization were shown to decrease in relation to increased soil depth, with significant differences depending on soil depth. Indications of aeolian processes indicate that windthrow events create different microsites, thereby influencing the specific micro-scale soil characteristics. These micro-scale characteristics should be taken into account when performing forest soils surveys and to inform forest management practices.

Effects of Pit and Mound Landscape on Soil Ecosystem Engineers at Local Scales - a Case Study in Hyrcanian Forest

Earthworms comprise a major proportion of the total invertebrate biomass in terrestrial ecosystems and they are often called ecosystem engineers. Felling of trees by wind occurs continually in forest ecosystems. Many of trees are uprooted by windthrow, annually. The uprooting of old trees creates multiple microsites (e. g. pit and mound landscape) that are main source for soil heterogeneity. Efforts have been made in this study to determine the impact of pit and mound landscape on earthworm assemblages. Due to, the experimental forest station of Tarbiat Modares University studied that is located in Mazandaran province, northern Iran. For this purpose, twenty hectare areas considered and numbers of thirty four uprooted trees were found. Five microsites were distinguished including mound top, mound wall, pit bottom, pit wall and closed canopy. Soil samples were taken at 0~15 cm, 15~30 cm and 30~45 cm depths from all microsites using core soil sampler with 81 cm 2 cross section. Soil pH, water content, organic carbon, total nitrogen and carbon to nitrogen ratio measured in the laboratory. The earthworms were collected simultaneously with the soil sampling by hand sorting method. As a result, in this study soil characters changes had significantly impact on earthworm abundance at local scales. Earthworm's (epigeic, anecic and endogeic) density and biomass had more amounts in pit bottom whereas, no earthworms found in mound top and wall microsites. Principle Component Analysis (PCA) performed on earthworm population and environmental variables showed that water content and C/N ratio are potential indicators of earthworm abundance change.

Quantifying the masses of Macrotermes subhyalinus mounds and evaluating their use as a soil amendment

Maintenance of soil quality is critical to environmental sustainability. However, its input cost is becoming unaffordable to small scale farming communities in Africa. Termites are an important element in traditional land-management practices in the Sahel. In their role as regulators of soil ecosystem processes, termites perform a number of vital functions. Although the application of termite mound materials as available nutrient sources is a common practice on the African continent, little is known about the density of masses of mounds and the amounts of nutrients they contain. First, two representative sites of 2km×1km were delineated and then termite mound abundance was recorded (43 and 30 in the two sites). They were used for volume and mass determinations. The study revealed an average abundance of 10moundsha−1 on Calcisols and 14moundsha−1 on Luvisols, with estimated mound soil masses of 13.5tha−1 and 58.9tha−1, respectively. Because termite mounds contain many pores and void spaces, a regression equation that can estimate the correct termite mound mass from mound volume and mound wall bulk density was developed. This revealed that conventional calculations of mound mass without correction for the voids overestimate the true mass by over 10%. Soil samples were collected from top and bottom parts of 6 selected mounds and in the different horizons of adjacent undisturbed soil profiles. Although insignificant differences in organic carbon and total nitrogen contents between the termite mound materials and the surface horizons of the adjacent soils were found, the termite mounds constitute a store of 27–53kgha−1 of total N and 186.3–306kgha−1 of OC. On both sites, the available P and the exchangeable Mg and K contents of termite mound soil were significantly higher than adjacent soils by 90%, 36% and 188%, respectively. Termite mounds contain a considerable store of plant nutrients and the use of mound material as a soil amendment shows great potential for improving soil chemical fertility.

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

AbstractThis study investigated the influence of mound‐building 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−1 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−1) balanced with a lower sand content (676 ± 26.5 g kg−1) than in the adjacent surface (Ap1) horizon, (46.4 ± 12.8 g clay kg−1; 866 ± 83.2 g sand kg−1); the nest body had much higher clay content (559 ± 51.0 g kg−1) but less sand (285 ± 79.2 g kg−1) than the mound wall. As a result, the mounds of M. bellicosus accumulated clay of 2,874 ± 781 kg ha−1 (corresponding to 2.52% of clay stock in the Ap1 horizon) along with an estimated clay turnover rate of 169 kg ha−1 year−1. 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.

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

The role of mounds of the fungus-growing termite Macrotermes bellicosus (Smeathman) in nutrient recycling in a highly weathered and nutrient-depleted tropical red earth (Ultisol) of the Nigerian savanna was examined by measuring stored amounts of selected nutrients and estimating their rates of turnover via the mounds. A study plot (4 ha) with a representative termite population density (1.5 mounds ha−1) and size (3.7 ± 0.4 m in height, 2.4 ± 0.2 m in basal diameter) of M. bellicosus mounds was selected. The mounds were found to contain soil mass of 9249 ± 2371 kg ha−1, composed of 7502 ± 1934 kg ha−1 of mound wall and 1747 ± 440 kg ha−1 of nest body. Significant nutrient enrichment, compared to the neighboring topmost soil (Ap1 horizon: 0–16 cm), was observed in the nest body for total nitrogen (N) and exchangeable calcium (Ca), magnesium (Mg) and potassium (K), and in the mound wall for exchangeable K only. In contrast, available (Bray-1) phosphorus (P) content was found to be lower in both the mound wall and the nest body than in the adjacent topmost soil horizon. Consequently, the mounds formed by M. bellicosus contained 1.71 ± 0.62 kg ha−1 of total N, 0.004 ± 0.003 kg ha−1 of available P, 3.23 ± 0.81 kg ha−1 of exchangeable Ca, 1.11 ± 0.22 kg ha−1 of exchangeable Mg and 0.79 ± 0.21 kg ha−1 of exchangeable K. However, with the exception of exchangeable K (1.2%), these nutrients amounted to less than 0.5% of those found in the topmost soil horizon. The soil nutrient turnover rate via M. bellicosus mounds was indeed limited, being estimated at 1.72 kg ha−1 for organic carbon (C), 0.15 kg ha−1 for total N, 0.0004 kg ha−1 for available P, 0.15 kg ha−1 for exchangeable Ca, 0.05 kg ha−1 for exchangeable Mg, and 0.06 kg ha−1 for exchangeable K per annum. These findings suggest that the mounds of M. bellicosus, while being enriched with some nutrients to create hot spots of soil nutrients in the vicinity of the mounds, are not a significant reservoir of soil nutrients and are therefore of minor importance for nutrient cycling at the ecosystem scale in the tropical savanna.

Occurrence And Distribution Of Mound Building Termites In And Around Kuvempu University Campus, Shimoga, Karnataka State, India

Three mound building termites, viz., Odontotermes wallonensis, Odontotermes obesus and Odontotermes redemanni Roomwal and Chhotani (1960), were identified from Kuvempu University campus, Jnana Sahyadri and adjacent Bhadra reservoir area. The shape of the mound of O.obesus was conical and extended vertically, consisting of one or more hallow conical turrets erected on the surface of the ground. Royal chamber in the mounds was usually placed at the base just beneath the fungus garden. The structure of mound of O. wallonensis was dome shaped with one or more turrets extended horizontally the wall of the turret was thin and smooth. The shape of the turrets were more in number, scattered on the ground with numerous vaults. In the established old mounds the fungus garden was enclosed in the vaults. The shape of the fungus garden was dome shaped and its colour was blackish-brown. The location of the royal chamber was excentric.The mound of O. redemanni was dome shaped with one or more turrets extended horizontally, low in height without any buttresses. The outer mound wall was thick, solid and devoid of openings. The fungus garden was situated in separate chambers which served as egg depository. A well developed royal chamber was located below the ground level. The occurrence and distribution of termites and their mounds in the area revealed that the rich humidity and cellulose material available supported the high density of termites.

Impact of a soil feeding termite, Cubitermes niokoloensis, on the symbiotic microflora associated with a fallow leguminous plant Crotalaria ochroleuca

The influence of a soil-feeding termite nest (Cubitermes nikoloensis) on the development of a symbiotic microflora (rhizobia, arbuscular mycorrhizas) was tested in a pot experiment with a tropical legume (Crotalaria ochroleuca). Our results confirmed the role of soil-feeding termite nests as sites of high nutrient concentration, as a significantly higher content of available P and mineral-N was found in the mound wall. Arbuscular mycorrhizal spores increased in the soil near the termite mound. The mound soil itself almost totally depressed mycorrhizal establishment. The positive effect of the soils close to the mound was also evidenced by the number of nodules per root system as well as the nodule biomass per legume plant grown on this medium. Better growth of Crotalaria seedlings was observed in the soils from the mound wall; the shoot biomass increased by a factor of 9 and the root biomass by a factor of 6 as compared to the control soil (10 m away from the mound). Plant growth on soils from the immediate vicinity of the mound showed intermediate results but a higher N content per biomass unit. This probably reflected the association with arbuscular mycorrhiza and rhizobia. This work evidenced the linkage of plant nutrition to nutrient availability in mound material and the indirect mediating effect of the symbiotic microflora.

Tool-Set for Termite-Fishing By Chimpanzees in the Ndoki Forest, Congo

Abstract Observations strongly indicate chimpanzees (Pan troglodytes troglodytes) of the Ndoki forest use two types of tools, 'perforating sticks' and 'fishing probes' in combination for termite (Macrotermes muelleri) fishing. Perforating sticks were always made of small, stout branches or young saplings of Thomandersia laurifolia (Acanthaceae), about 10 mm in diameter, with lengths of about 50 cm. Fishing probes were made from the flexible stems of Marantaceae species, and were about five mm in diameter, with lengths of about 50 cm. Approximately 15 cm of one end of the tool was usually shaped into a brush. It is likely that chimpanzees make small holes in the termite mound wall to attain access into the termite nest inside, then they insert the probe into the holes and eat the major and minor soldier termites which bite the brush-like end. Of 214 chimpanzee feces collected, 50% contained termite remains of this species, and this fecal analysis shows that termite-eating behavior occurred all the year around, and did not correspond to the seasonality of rainfall or termite activity on the ground. Chimpanzees in the Ndoki forest seem to be able to obtain termitcs from the deep subterranean nest throughout the year by using their tool-set. Such a tool-set might be responsible for the higher frequency of termite-eating in Ndoki chimpanzees than those of chimpanzees in other sites who fish for termites using only probes. This newly described behavior shows that chimpanzees habitually manipulate a tool on an object which they previously modified with another type of tool.