The Influence of Land-Use Types on Terrestrial Soil Invertebrate Species Diversity in the Transitional Zones of Ghana

1. Introduction

Soil invertebrates constitute an essential component of terrestrial ecosystems, performing a wide range of ecological functions that support both aboveground and belowground ecosystem processes (Timpas et al., 2023). These organisms include earthworms, termites, and ants, recognised as ecosystem engineers because they modify soil structure, improve aeration, and facilitate nutrient cycling through their activities. Despite increasing attention being directed towards the ecological importance of soil fauna, they continue to receive less emphasis than other agricultural priorities, particularly efforts aimed at maximising agricultural productivity, which often overlook their critical role in maintaining soil health and ecosystem sustainability (Maqtan et al., 2021). These organisms are indispensable for key ecological processes such as decomposition of organic matter, soil aggregation, and the maintenance of soil fertility (Heděnec et al., 2022; Zhang et al., 2023). However, despite increasing recognition of their ecological importance, land-use changes continue to modify soil biota assemblages, with significant implications for the delivery of essential ecosystem services.

Extensive evidence indicates that human activities have profoundly altered ecosystems worldwide (Tetteh et al., 2018; Millennium Ecosystem Assessment, 2005; Díaz et al., 2006). Among the various anthropogenic drivers, land-use change is recognised as one of the most significant factors reshaping terrestrial ecosystems (Foley et al., 2005; Winkler et al., 2021). The conversion of natural forests into anthropogenic landscapes, including agricultural lands for food production and plantation forests for timber harvesting, has substantially modified vegetation structure and reduced biodiversity, including soil invertebrates, across diverse biomes and continents. These changes have adversely affected soil health and diminished the ecosystem services that soils provide (Sylvain & Wall, 2011; Nielsen et al., 2015; Veldkamp et al., 2020; Zarafshar et al., 2020).

Although previous studies have documented the effects of land-use change on aboveground biodiversity, the responses of terrestrial soil invertebrate communities remain inadequately understood, particularly in tropical ecosystems such as Ghana. The conversion of natural forests into agricultural lands and other human-modified landscapes is expected to alter soil habitat conditions, yet there is limited empirical evidence on how these changes influence the diversity, richness, abundance, and composition of soil invertebrate species. This knowledge gap constrains the development of effective land-use and conservation strategies aimed at preserving belowground biodiversity and sustaining ecosystem services provided by soil organisms. Consequently, the study seeks to investigate the influence of different land-use types on terrestrial soil invertebrate species diversity and to generate baseline information for sustainable ecosystem management. The purpose of this study is to evaluate and compare terrestrial soil invertebrate communities across different land-use types to determine the extent to which land-use practices influence soil biodiversity. The findings will contribute to a better understanding of how land-use change affects belowground ecosystems and provide scientific evidence to support sustainable land management, biodiversity conservation, and the maintenance of essential soil ecosystem services.

2. Methods

2.1. Study Area

The study was conducted in three selected land-use types, namely cultivated farmland, grazing land, and secondary and primary forest. The first site is the cultivated farmland in Niniting, Ashanti Mampong Municipality, which lies at latitude 7°00′19′ N and longitude 1°26′12′ W, with an elevation of about 456 m above sea level. The cultivated farmlands in the area have been deliberately modified and managed by humans for the production of crops such as plantain (Musa sapientum), cocoa (Theobroma cacao), carrot (Daucus carrota), cassava (Manihot sp.), cocoyam (Colocasia esculenta), yam (Dioscorea sp.) and other cash crops.

The second site is the grazing land located at the University of Skills Training and Entrepreneurial Development. These grazing lands were primarily used for feeding domesticated or wild herbivorous animals, such as cattle, sheep, goats and other livestock from the university farm. The area consists of natural grasslands, improved pastures, shrublands, and savannah where the vegetation is periodically managed for livestock production. Geographically, the area lies at 7°04′ N latitude and 1°24′ W longitude. The dominant plant species found in the area include Cynodon dactylon, Sida acuta, Panicum maximum, and Imperata cylindrica.

The third and fourth site is the Kogyae forest reserve, located in the forest savannah transition zone. It covers approximately 386 km² and represents an ecological transition between the Guineo-Congolian forest and Sudanian or Guinea savanna ecosystems. Geographically, the reserve is located between 7°12′N and 7°15′N latitude and 1°05′W and 1°11′W longitude. Due to illegal logging and degradation, the reserve has been categorized as a secondary and primary forest reserve. The soil found within the reserve is mostly the Voltarian geological formation, relatively shallow and prone to drying, particularly in areas dominated by savanna vegetation. The reserve is a semi-evergreen or deciduous forest, transition woodland, savanna woodland and open grassland. Dominant forest tree species in the reserve include Cola gigantea, Sterculia tragacantha, Dacryodes klaineana, Ceiba pentandra, Khaya senegalensis, Milicia excelsa, and Triplochiton scleroxylon. The reserve receives approximately 1,200-1,300 mm of annual rainfall. The landscape experiences a dual rainy season, with the primary rainy season from March to August and the secondary one occurring between September and November. The reserve promotes eco-tourism for the municipality and the nation. However, illegal logging and farming along the reserve serve as the main source of livelihood for the inhabitants.

2.2. Sampling Procedure

In total, fifteen of 25 m × 25 m plots were sampled. The plot size followed the work of previous studies (Tetteh et al., 2018; Asase and Tetteh, 2010). The plots were randomly distributed within each land use type. Thus, a total of sixty (60) plots were demarcated for the primary forest, secondary forest, cultivated and grazing lands.

2.3. Soil Invertebrate Determination

Sampling of soil invertebrates was carried out in both the dry season (February) and the wet season (May). For each land use type, two pitfall traps of dimensions 9 cm height 12 cm were placed at least 5 m apart (Tetteh and Amos, 2024). Thirty (30) pitfall traps were sunk per land use plot and were checked every two days. The traps were filled with three-quarters water and a few drops of detergent to lower surface tension. Specimens were preserved in 70% ethanol after retrieval and sorted in the laboratory for later taxonomic identification. The densities of the captured insects were calculated, and species identification was verified with standard taxonomic references (Blair et al., 1996, as cited in Tetteh et al., 2018).

2.4. Statistical Analysis

Soil invertebrate diversity was assessed using the Shannon–Wiener diversity index (H) and the Jaccard similarity index. The indices were calculated with EstimateS software version 9.1.0 (Colwell, 2019).

3. Results and Discussion

3.1. Results

In total, 2,280 individuals of soil invertebrates belonging to twenty-five species, fourteen taxonomic families and nine orders were identified (Table 1 and Table 2). The dry season recorded 1,462 individual soil invertebrates compared to 818 individuals recorded in the wet season. The families with the greatest number of species were Formicidae (twelve species), Gryllidae (five species), Blattidae (two species) and Scarabaeidae (two species). The total number of soil invertebrate species was 861 in the primary forest, 592 in the secondary forest, while the lowest number, 386, was observed in the grazing land (Table 1 and Table 2). Of the number identified, the most abundant soil invertebrate species in the different land use types were Camponotus chrysursus, Dystercus latissimus, Acheta domesticus, Blattella germanica, Canthon pilularius, Archispirostreptus gigas and Blattela sp.

The majority (64.1%) of the species and individuals of the species were detected in the dry season. Twenty-five of the species were identified in both dry and wet seasons. Mean density of soil invertebrates was higher (24.5±13.2 ha^-1) in the primary forest, followed by the secondary forest (22.4±12.3 ha^-1), while the lowest (13.4±5.2 ha^-1) was in the grazing lands. The density of soil invertebrates was significantly different among the land use types (p < 0.001).

Diversity indices and community structure across seasons and land uses

Mean species richness was higher in the primary forest and lower in the grazing land for both dry and wet seasons and varied significantly in the different land use types (p<0.05). Mean evenness of species also varied significantly among the different land use types, with the highest recorded in the primary forest and the lowest observed in the grazing farmland (Table 3). The study indicates that the mean Shannon-Wiener index was higher for the primary forest reserve and lower in the grazing land. Mean Shannon-Wiener index differs significantly in the different land use types (p< 0.05). The Jaccard similarity statistics showed that the cultivated farmlands and grazing lands are most similar (Jaccard index = 0.242) while the least (Jaccard index = 0.201) was observed in the primary forest and the cultivated farmland.

3.2. Discussion

The findings of the study demonstrate that the conversion of natural forests into human-dominated landscapes, particularly cultivated farmlands and pasturelands, can have considerable effects on soil invertebrate communities. The reduction in soil invertebrate abundance and diversity across managed land-use systems highlights the adverse effects of habitat modification, land-use intensification and landscape homogenisation on terrestrial biodiversity. This observation is consistent with previous studies conducted in tropical mountain ecosystems, which reported that the conversion of natural vegetation to agricultural land can result in significant losses of soil biodiversity (Guarderas et al., 2022; De Valença et al., 2017). Similarly, differences in the structure and composition of soil invertebrate communities among land-use types may reflect variations in the intensity of human disturbance and management practices (Tetteh and Amos, 2024; Lukina et al., 2011; Sylvain and Wall, 2011).The relatively lower abundance of soil invertebrates recorded in cultivated farmlands and pasturelands could be attributed to agricultural practices and other forms of anthropogenic disturbance such as application of agrochemicals, frequent weeding, vegetation removal and continuous grazing which alters soil conditions and reduce the availability of suitable habitats and food resources. The drastic reduction of soil invertebrates in the grazing lands could also be attributed to the continuous grazing and trampling of the vegetation disturbing the soil surface by compaction and the reduction of vegetation and litter cover and limiting the availability of suitable microhabitats for soil invertebrates. In this study, species evenness and Shannon diversity index were higher in the primary and secondary forest than in the cultivated and pasture fields. This observation is consistent to values recorded Tetteh and Amos, (2024) in a similar study.

The most common species also found including Camponotus chrysursus, Dystercus latissimus, Acheta domesticus, Blattella germanica, Canthon pilularius, and Archispirostreptus gigas as recorded in this study. The occurrence of these taxa across the different land-use systems suggests that some soil invertebrates possess a degree of tolerance to environmental disturbance and are capable of surviving under modified habitat conditions. Their presence may also indicate that certain managed ecosystems retain resources and microhabitats that can support particular groups of soil invertebrates. The relatively high abundance and diversity of soil invertebrates recorded in primary and secondary forests may be attributed to the greater structural complexity and ecological stability of these ecosystems. Natural forests are characterised by multilayered vegetation, dense understorey, diverse plant communities and substantial accumulation of leaf litter. These characteristics contribute to the formation of favourable microhabitats by regulating soil temperature and moisture, increasing organic matter availability and providing diverse sources of food and shelter for soil- and litter-dwelling organisms (Ramos et al., 2025). The greater structural heterogeneity of forest ecosystems consequently provides a wider range of ecological niches, which can support more abundant and diverse soil invertebrate communities.

Despite the relatively lower abundance recorded in cultivated farmlands and pasturelands, the presence of several soil invertebrate species demonstrates that these landscapes can still provide suitable refugia for some organisms. The diversity recorded in these land-use systems supports the view that agricultural landscapes, particularly those retaining vegetation and organic residues, can contribute to the conservation of certain components of terrestrial biodiversity (Rahman et al., 2011). Decaying organic matter, leaf litter, crop residues and other forms of vegetation can create microhabitats that provide food, shelter and suitable environmental conditions for different soil invertebrate species. Therefore, the conservation value of agricultural landscapes may depend strongly on how they are managed and the extent to which natural habitat features are retained. Findings of the study indicate that although natural forests remain the most important habitats for maintaining soil invertebrate diversity, appropriately managed agricultural and pasture landscapes can also contribute to biodiversity conservation. Management practices that maintain vegetation cover, minimise soil disturbance and retain organic matter may enhance the capacity of modified ecosystems to support soil invertebrate communities.

4. Conclusion

In conclusion, primary and secondary forests generally supported greater soil invertebrate diversity due to their complex vegetation, stable microclimates, organic matter, and varied habitats. In contrast, cultivated and pasturelands supported fewer invertebrates, likely because of agrochemical use, vegetation removal, grazing, and soil disturbance. Nevertheless, the presence of some species in these modified landscapes suggests that they can serve as secondary habitats or refuges. Sustainable land-management practices, including retaining vegetation, leaf litter, and organic matter while minimising disturbance, could therefore enhance soil biodiversity in agricultural areas.

Funding: