The role of earthworms in the formation of sandy surface soils in a tropical forest in Ivory Coast

doi:10.1016/0016-7061(94)00035-9

Geoderma

Volume 65, Issues 1–2, February 1995, Pages 135-148

https://doi.org/10.1016/0016-7061(94)00035-9 Get rights and content

Abstract

Soils with relatively sandy topsoils over clayey subsoils are widespread, but their genesis is not always clear. We tested the hypothesis that earthworms stimulate the formation of the sandy surface soils by producing clay-rich worm casts that are susceptible to erosion, in an undisturbed forested watershed in southwestern Ivory Coast. Soils of the watershed were strongly weathered and acidic. Their contents of ironstone gravel and of clay, organic matter and plant nutrients decrease in a downslope direction. Production of worm casts increased in the same direction from 0.1 to 0.2 kg m⁻² yr⁻ near the top of the watershed to between 2.3 and 9.6 kg M⁻² yr⁻ near the valley bottom, with an areal average of 3.2 kg m⁻² yr⁻. Casts were invariably richer in clay and silt, organic matter and N, P, Ca and Mg than nearby bulk surface soil. Casts were easily disintegrated by rain splash and overland flow and cast material contributed to the 0.12 kg m⁻² yr⁻ of highly organic suspended sediment removed by surface water drainage. Selective erosion of worm casts was probably more important than eluviation of clay in removing clay from the surface soils. Increasing production and disintegration of casts with decreasing elevation probably played a major role in lowering contents of clay and nutrients in the surface soils in the lower parts of the area.

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Impacts of wetting-drying cycles on short-term carbon and nitrogen dynamics in Amynthas earthworm casts
2021, Pedosphere
Effects of earthworm casts on soil nutrient dynamics and their responses to changing moisture availability in subtropical ecosystems remain poorly understood. This study aimed to examine short-term carbon (C) and nitrogen (N) dynamics and their interactions with wetting-drying cycles in three different structural forms (i.e., granular, globular, and heap-like) of Amynthas earthworm casts. The rates of C and N mineralization in the earthworm casts were examined under two different wetting-drying cycles (i.e., 2-d and 4-d wetting intervals) using a rainfall simulation experiment. After three simulated rainfall events, subsamples of the earthworm casts were further incubated for 4 d for the determination of CO₂ and N₂O fluxes. The results of this study indicated that the impacts of wetting-drying cycles on the short-term C and N dynamics were highly variable among the three cast forms, but wetting-drying cycles significantly reduced the cumulative CO₂ and N₂O fluxes by 62%–83% and 57%–85%, respectively, when compared to the control without being subjected to any rainfall events. The C mineralization rates in different cast forms were affected by the amount of organic substrates and N content in casts, which were associated with the food preference and selection of earthworms. Meanwhile, the cumulative N₂O fluxes did not differ among the three cast forms. Repeated wetting and drying of casts not only enhanced aggregate stability by promoting bonds between the cast particles, but also inhibited microbial survival and growth during the prolonged drying period, which together hindered decomposition and denitrification. Our findings demonstrated that the interactions between the structural forms, aggregate dynamics, and C and N cycling in the earthworm casts were highly complex.
Mid-infrared spectroscopy to trace biogeochemical changes of earthworm casts during ageing under field conditions
2021, Geoderma
Citation Excerpt :
The wavenumbers 1595 and 1456 cm−1 may be related to amide and carboxylate C, which are typical OM compounds subjected to change during OM degradation (Parikh et al., 2014). The wavenumber 1942 cm−1 corresponds to quartz and its gradual increase in intensity from cast A to topsoil aggregates might suggest the preferential loss of mineral constituents caused by rainfall (Nooren et al., 1995). Degradation of OM occurring during cast ageing and change in mineral composition thus explained the differentiation of the samples along axis 1.
Earthworm cast ageing controls soil ecosystem services such as carbon storage and nutrient availability. To test the hypothesis that biogeochemical changes during casts ageing can be traced by infrared spectroscopy, we collected topsoil aggregates and earthworm casts produced by the anecic earthworm Amynthas khami belonging to five distinct degradation stages in woodland in northern Vietnam. We analysed mid-infrared (MIR) spectra of both sample types using two approaches: (1) calculation of the proportion of aliphatic compounds and the humification index of organic matter (OM) using specific wavenumbers and (2) linear discriminant analysis (LDA) of the most important peaks and shoulders of the entire spectrum. Our results showed that aliphatic compound contribution to OM was similar and the humification index of OM lower (2-fold) in casts as compared to topsoil aggregates independent of their degradation stage. In contrast, LDA showed a continuous shift from fresh casts to aged casts and topsoil aggregates in agreement with biogeochemical changes of cast properties. We thus conclude that MIR analysis of bulk samples and LDA taking into account the absorbance intensity of most important wavenumbers is a promising tool to capture biogeochemical alterations of organic and mineral earthworm cast properties during ageing.
Enamel chipping in Taï Forest cercopithecids: Implications for diet reconstruction in paleoanthropological contexts
2020, Journal of Human Evolution
Citation Excerpt :
At present, it is unknown whether enamel chip morphology differs as a result of contact with hard foods or nonfood particulate matter of millimetric size (Strait et al., 2013). The Taï Forest contains exogenous particulate matter that often adheres to food items (Nooren et al., 1995; Geissler et al., 2018; Schulz-Kornas et al., 2019). Particulate accumulation is often strongest during the seasonal Harmattan winds, which deposit large quantities of sand and dust on both the canopy and ground surfaces (Schulz-Kornas et al., 2019).
Antemortem enamel chipping in living and fossil primates is often interpreted as evidence of hard-object feeding (i.e., ‘durophagy’). Laboratory analyses of tooth fracture have modeled the theoretical diets and loading conditions that may produce such chips. Previous chipping studies of nonhuman primates tend to combine populations into species samples, despite the fact that species can vary significantly in diet across their ranges. Chipping is yet to be analyzed across population-specific species samples for which long-term dietary data are available. Here, we test the association between enamel chipping and diet in a community of cercopithecid primates inhabiting the Taï Forest, Ivory Coast. We examined fourth premolars and first molars (n = 867) from naturally deceased specimens of Cercocebus atys, Colobus polykomos, Piliocolobus badius, Procolobus verus, and three species of Cercopithecus. We found little support for a predictive relationship between enamel chipping and diet across the entire Taï monkey community. Cercocebus atys, a dedicated hard-object feeder, exhibited the highest frequencies of (1) chipped teeth and (2) chips of large size; however, the other monkey with a significant degree of granivory, Co. polykomos, exhibited the lowest chip frequency. In addition, primates with little evidence of mechanically challenging or hard-food diets—such as Cercopithecus spp., Pi. badius, and Pr. verus—evinced higher chipping frequencies than expected. The equivocal and stochastic nature of enamel chipping in the Taï monkeys suggests nondietary factors contribute significantly to chipping. A negative association between canopy preference and chipping suggests a role of exogenous particles in chip formation, whereby taxa foraging closer to the forest floor encounter more errant particulates during feeding than species foraging in higher strata. We conclude that current enamel chipping models may provide insight into the diets of fossil primates, but only in cases of extreme durophagy. Given the role of nondietary factors in chip formation, our ability to reliably reconstruct a range of diets from a gradient of chipping in fossil taxa is likely weak.
Surface casting of the tropical Metaphire posthuma increases soil erosion and nitrate leaching in a laboratory experiment
2013, Geoderma
Citation Excerpt :
Earthworm casts produced on the soil surface can influence water infiltration, the detachment and erosion of soil, and the diffusion of nutrients throughout ecosystems via different mechanisms. While freshly emitted earthworm casts are prone to dislocation by the rain and can increase crust formation and soil erosion, aged earthworm casts are considered to enhance soil roughness, increase water infiltration and decrease soil detachment (Blanchart et al., 2004; Nooren et al., 1995; Shipitalo and Le Bayon, 2004). As a consequence, earthworm surface casts have been suggested to significantly influence soil quality (Hauser et al., 2012).
In tropical regions, earthworm casts can be globular or granular, depending on the earthworm species that produced them. Although the effects of globular casts on soil erosion have been extensively studied, less is known regarding the effects of granular casts. This study aimed to investigate how granular casts produced by Metaphire posthuma affect soil erosion. To recreate the patchy accumulation of aggregates in the field, small piles of earthworm casts (CAST) or non-ingested soil (NIS) were placed on a layer of bare soil in microcosms. Rainfall simulations were then carried out to measure the fragmentation dynamics of the different types of aggregates, soil detachment and water runoff quantity and quality (NH₄⁺ and NO₃⁻ content, pH and conductivity). Our results clearly show that CAST aggregates are more prone to water-disintegration than NIS aggregates. As a consequence, M. posthuma activity significantly contributes to a decrease in soil roughness and an increase in soil detachment. The quantity of water runoff collected after the rainfall simulation was similar between both types of aggregates but higher NO₃⁻ concentrations were found with CAST than with NIS aggregates. In conclusion, this study suggests that due to production of granular labile casts at the soil surface, M. posthuma has a detrimental effect on soil roughness and detachment, and NO₃⁻ leaching. More studies are now required to determine if our results are general attributes of granular casts.
Influence of earthworms and termites on runoff and erosion in a tropical steep slope fallow in Vietnam: A rainfall simulation experiment
2012, Applied Soil Ecology
Citation Excerpt :
However, unstable biogenic aggregates (e.g., freshly emitted earthworm casts, termite sheetings) accumulated on the soil surface are prone to dislocation by the rain and can increase seal formation and soil erosion. Water stable aggregates (e.g., old earthworm casts and termite nests), on the other hand, enhance soil roughness, increase water infiltration, protect the soil from crusting and thus decrease soil detachment (Nooren et al., 1995; Blanchart et al., 2004; Shipitalo and Le Bayon, 2004; Jouquet et al., 2004, 2008a, 2010). Surprisingly, very few studies have been conducted in sloping lands of the tropics which are characterized by intense rainfall events, soil degradation, rapid biogeochemical cycling and large populations of soil engineers.
Earthworms and termites, as soil engineers, play a major role in the regulation of biogeochemical processes and the provision of ecosystem services. They create biogenic aggregates on the soil surface, e.g., earthworm casts and termite sheetings, which can influence soil erosion and the downward transfer of fertility. We assessed the effect of the micro-relief generated by earthworms and termites on soil hydrodynamic properties, and soil and nutrient losses. Eighteen 1 m × 1 m plots were established for rainfall simulation experiments (2 runs of 40 min rain, intensity 90 mm h⁻¹) in a steep slope fallow in Northern Vietnam. The soil surface of the micro-plots differed in the proportions of earthworm casts and termite sheetings. The results confirmed the importance of soil biostructures in the regulation of pedohydrological properties of soils. Although globular water-stable earthworm casts promote water infiltration in soil and decrease soil and nutrient losses, the unstable termite sheetings break-down rapidly and generate structural crusts which foster water runoff and soil detachment. No relation was observed between the abundance or biomass of earthworms or termites and the pedohydrological properties measured during the rainfall simulations. This therefore suggests that soil engineers can have greater impact on ecosystem functioning through their biogenic structures rather than as a result of their own abundance or biomass.
Influence of termite infestation on the spatial variability of soil properties in the Guinea savanna region of Nigeria
2009, Geoderma
Soil spatial variability affects the precision of statements about soil properties, behaviour and land use. Termites feed, construct and repair their nests from organic and inorganic components of the soil and through these activities influence soil formation processes and consequently contribute to soil variability as a point centered pedoturbation process. The objective of this study is to evaluate the influence of termites on the spatial variability of soil physical and chemical properties in the Guinea savanna region of Nigeria, using geostatistics, which have been found to be suitable for investigating spatial variability in comparison with classical statistics. Routine soil parameters were measured in the 0–15 cm depth of 20 m × 20 m grid samples in two termite infested and one non-infested plot (each measuring 100 m × 100 m) in Mokwa and Kontagora areas of Niger State, Nigeria. On average, 73.3% and 66.7% of the soil properties in the infested and non-infested plots respectively of Mokwa, and 70.0% and 93.3% of the soil properties in the infested and non-infested plots respectively of Kontagora had coefficients of variation < 35%. Using maximum R², models were fitted to the semivariograms. The magnitude of positive nugget effect displayed by most soil properties as a result of termite infestation (i.e. within the range of 0.002–0.009) was about 100 times lower than those of non-infested (i.e. within the range of 0.008–0.02) in Mokwa. The particles size distribution of the soils were significantly correlated and display strong spatial dependence in the infested plots of Mokwa as indications of intrinsic variation attributable to point centered pedoturbation of termites. Termites contribute to short range variability of soils texture in Mokwa area of Nigeria, which was observed at 20 cm interval while shorter sampling interval may be necessary in Kontagora. Hence inter-termiterial distance could be a determinant in extent of spatial variability.

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Geoderma

Abstract

References (29)

Properties of worm casts and surface soils under various plant covers in the humid tropics

Soil Biol. Biochem.

Potential role of earthworm casts for the phosphorus enrichment of runoff waters

Soil. Biol. Biochem.

Effect of surface-casting earthworms on the transport of phosphorus and nitrogen in surface runoff from pasture

Soil. Biol. Biochem.

On the amount of cast production by the megascolecid earthworm Pheretima hupeiensis

Pedobiologia

Etude hydrologique des bassins de Taï

Comportements hydrodynamiques et érosifs de sols de l'Afrique de l'ouest. Évolution des matériaux et des organisations sous simulation de pluies

Land Unit Survey of the Taï region, south-west Côte d'lvoire

FAO-UNESCO Soil Map of the World: revised legend

A technique for the preparation of large thin sections of soils and consolidated material

A study of a catena in the Taï forest, Ivory Coast

Etude pédologique et représentation cartographique à 1/15000^eme d'une zone de 1600 ha, représentative de la region forestière du sud-ouest ivorien

Evolution des sols sous recrû forestier aprés mise en culture traditionelle dans le sud-ouest de la Côte d'lvoire

The geomorphological role of termites and earthworms in the tropics

Cited by (38)

Impacts of wetting-drying cycles on short-term carbon and nitrogen dynamics in Amynthas earthworm casts

Mid-infrared spectroscopy to trace biogeochemical changes of earthworm casts during ageing under field conditions

Enamel chipping in Taï Forest cercopithecids: Implications for diet reconstruction in paleoanthropological contexts

Surface casting of the tropical Metaphire posthuma increases soil erosion and nitrate leaching in a laboratory experiment

Influence of earthworms and termites on runoff and erosion in a tropical steep slope fallow in Vietnam: A rainfall simulation experiment

Influence of termite infestation on the spatial variability of soil properties in the Guinea savanna region of Nigeria

Research paperThe role of earthworms in the formation of sandy surface soils in a tropical forest in Ivory Coast

Abstract

Soil Biol. Biochem.

Soil. Biol. Biochem.

Soil. Biol. Biochem.

Pedobiologia

Etude hydrologique des bassins de Taï

Comportements hydrodynamiques et érosifs de sols de l'Afrique de l'ouest. Évolution des matériaux et des organisations sous simulation de pluies

Land Unit Survey of the Taï region, south-west Côte d'lvoire

FAO-UNESCO Soil Map of the World: revised legend

A technique for the preparation of large thin sections of soils and consolidated material

A study of a catena in the Taï forest, Ivory Coast

Etude pédologique et représentation cartographique à 1/15000eme d'une zone de 1600 ha, représentative de la region forestière du sud-ouest ivorien

Evolution des sols sous recrû forestier aprés mise en culture traditionelle dans le sud-ouest de la Côte d'lvoire

The geomorphological role of termites and earthworms in the tropics

Research paper
The role of earthworms in the formation of sandy surface soils in a tropical forest in Ivory Coast

Etude pédologique et représentation cartographique à 1/15000^eme d'une zone de 1600 ha, représentative de la region forestière du sud-ouest ivorien