Ethiopian Journal of Environmental Studies & Management 10(9): 1200 – 1210, 2017. ISSN:1998-0507 doi: https://ejesm.org/doi/v10i9.8 Submitted: August 8, 2017 Accepted: November 22, 2017 COMPARATIVE INSECT ABUNDANCE AND DIVERSITY IN AMURUM FOREST RESERVE AND SURROUNDING FARMLANDS, JOS, NIGERIA *OMBUGADU, A.,1 MWANSAT, G.S.,2 CHASKDA, A.A. 2 AND NJILA, H.L. 3 *1Department of Zoology, Federal University Lafia, Nasarawa State, Nigeria 2Department of Zoology, University of Jos, P.M.B. 2084, Jos, Nigeria 3Department of Science Laboratory Technology, University of Jos, Nigeria *Corresponding author: [email protected] Abstract Abundance and diversity of ground-dwelling insect of Amurum Forest Reserve and surrounding farmlands (subdivided into organic and inorganic farmlands) was studied using the pitfall trap method during the on-set of the rainy season of 2005. The organic farmland is made up of waste products from animal husbandry, plant decomposition or products from waste treatment for improvement of soil condition; whereas inorganic farmlands uses inorganic or mineralize fertilizers that are synthetically produced organic compounds to improve soil condition. A total of 29, 217 individuals representing 19 orders, 55 families and 70 species, were collected. Hymenoptera and Coleoptera were the most species – rich orders with Formicidae and Scarabaeidae contributing the most to this richness. Of the three sites sampled, Amurum Forest Reserve and organic farmland had the most diverse and abundant insect species respectively. Some of the species sampled are potentially harmful as agricultural pests whereas others are likely beneficial as agents of biological control. The result suggests organic farm practice as more insect friendly. Key Words: Ground-dwelling insect, Abundance, Diversity, Amurum Forest Reserve Organic farmland, Inorganic farmland Introduction taxa; these include their potential as The health of an ecosystem is often beneficial plant pollinators, food for measured by the diversity of species it birds, disease vectors, biological control holds. These include insects, which are agents etc. (Rosenberg et al., 1986). known to occupy diverse niches (Levy, Some studies have examined the 2003). The importance of insects as responses of various taxa, including indicators of ecosystem health is greatly ground beetles (Family: Scarabaeidae), due to their varying tolerant limits to ants (Family: Formicidae), and butterflies organic and inorganic substances (Bass, (Family: Pyralidae), to urbanization, 1994; Mason, 1997). Similarly, when logging, agricultural practices, and fire used as indicators for conservation, (Dunn, 2004; Sawchik et al. , 2005; Koh, insects have many advantages over other 2007; Bonebrake and Sorto, 2009; Sodhi This work is licensed to the publisher under the Creative Commons Attributions License 4.0 1200 Comparative Insects Abundance and Diversity in Amurum Forest ................ OMBUGADU et al. et al ., 2009; Bonebrake et al., 2010; However, despite the ecological Buczkowski and Richmond , 2012; functions played by soil arthropods, Ojianwuna, 2015; Green Fact, 2016). fewer studies have examined their Few, if any have attempted to examine distribution across different agricultural terrestrial invertebrate assemblages practices. across a range of disturbance events This study aimed to elucidate the (Kimberling and James, 1998). This is of effect of soil disturbance through farming importance especially in agricultural on the diversity and abundance of systems where ground insects are known ground-dwelling insects compared to the to mediate a number of essential uncultivated soil of the Amurum Forest ecological processes that are vital to the Reserve. entire ecosystem: the degradation of organic matter, cycling of nutrients, Materials and Methods sequestration of carbon, and the Study Areas development and maintenance of soil Amurum Forest Reserve and structure by creating channels, pores, surrounding farmlands (organic and aggregates and mounds that influence the inorganic farmlands) are located in Jos- transportation of gases and water (Smith, East Local Government Area of Plateau 2004). State, North Central Nigeria. The Intensive agriculture requires use of Amurum forest reserve (9°53´N 08°59´E) conventional fertilizers, which in the long is about 300 hectares with an annual run result in lower soil fertility, increased rainfall of 1375mm – 1750mm per soil erosion and reduced biodiversity. annum, 58 species of plants and 300 This is thought to be unsustainable in the species of birds and some mammals long-term, as the functions performed by occupy the forest including arthropods the soil biota must increasingly be (Ezealor, 2002). replaced by chemical and mechanical Organic and inorganic farmlands inputs. On the other hand, agri- surround the forest reserve. Cereals ′like environment schemes encourage the maize ( Zea mays ), millet ( Panicum adoption of agricultural practices such as miliaceum ), sorghum ( Sorghum use of organic fertilizers due to their vulgaris ), acha ( Digiteria exilis ) are importance in the conservation of cultivated mostly in the fields annually. wildlife (Beecher et al ., 2002; Smith, The organic farmlands had been managed 2004; Wickramasinghe, 2004; Bengtsson organically for about10 years while the et al., 2005 ). For example, research has inorganic farmland for about 5 years demonstrated greater insect’s richness using synthetic fertilizers (15-15-15 and abundance ( Bengtsson et al., 2005 ) NPK). and as well as avian species on whole Organic farmlands in the area make organic farms than on conventional farms use of waste products from animal (Dahlgren, 1984; Chamberlain et al., husbandry, plant decomposition or 1999). Similarly, Chiang (1970) reported products from waste treatment to that fertilized cornfields (50 tons improve soil condition thereby having a manure/acre) had significantly fewer (ca. long-term return in which products ½) corn rootworms than did unfertilized produced are good in taste, flavour, controls. nutrition and free from chemicals (Chand 1201 Ethiopian Journal of Environmental Studies and Management Vol. 10 no.9 2017 and Pabbi, 2005), supports livelihood of (Lampkin, 1990). The use of inorganic rural dwellers, enhances biodiversity and fertilizers in modern agriculture is simultaneously reduces vulnerability to imperative due to population growth. climate change (Gabriel et al., 2010; Chemical fertilizers use has brought Smith et al., 2010; Thippeswamy, 2013). blessings to humanity through containing Inorganic farmlands in the area use hunger and death in different parts of the inorganic or mineralize fertilizers that are world. But their use have resulted in synthetically produced organic being hazardous to human health and compounds to improve soil condition. environment (Dittmar et al., 2009; Inorgainc fertilizers are being used by Zaman et al., 2011). both commercial and subsistence farmers Figure 1: Map of Amurum Forest Reserve, Laminga, Jos East LGA, Plateau State, Nigeria Methodology Grzimek, 1972; Skaife and Bannister, Ten pitfall traps along a 100 m 1979; Castner, 2000). transect across the three study sites where Statistical analysis was carried out set in two circles of 10 m radius each using the computer software package, containing five individual traps and are Statistical Package for Social Sciences 50 m apart (Van den Bergh, 1992). Pitfall (SPSS Version 11.0 2001). Data was traps were left in the field for 24 hours explored for normality and equality of after which contents were emptied into variance using the Kolmogorov-Smirnov labeled specimen bottles and later sorted, test and the Levene test respectively. The identified and enumerated to species level non- parametric test; Kruskal-Wallis H in the laboratory using insect test was used to check differences in the identification keys (Holt et al., 1964; mean number of insects across the three 1202 Comparative Insects Abundance and Diversity in Amurum Forest ................ OMBUGADU et al. (3) study habitats. Two diversity indices: study sites. These constituted 19 orders, Simpson’s diversity index (D) and 55 families and 70 species (Table 1). Shannon-Wiener index of diversity (H ΄) Insect Abundance across Study Sites were calculated to compare species Insect abundance did not vary diversity across study sites. The P value < significantly (Kruskal-Wallis H test: χ2 = 0.05 was considered statistically 0.464, df = 2, n = 387, P = 0.793) across significant. study sites although average insect abundance was higher on organic Results farmland (Figure 2). Total Number of Insects Collected Species Richness A total of twenty nine thousand, two Results showed the Scrub savanna of hundred and seventeen (29,217) Amurum Forest Reserve as the most individual insects were collected from all species rich as compared to the other study sites (Table 3). Table 1: Distribution of Insect Fauna collected using Pitfall Trap from 3 Habitat Types Site Population of Insects Percentage Mean ± SE Scrub savanna 5,281 18.0 41 ±11.283 Organic farmland 12,404 42.5 89 ±24.740 Inorganic farmland 11,532 39.5 84 ±25.351 Total 29,217 100 120 100 80 60 40 20 0 Number of S. Insects E. ±2 scrub savanna organic farmland non-organic farmland Habitat types Figure 2: Insect distribution across the three study sites Table 2: Distribution of insect by Order/Family across study sites Site Insect Order Insect Family No. % No. % Scrub savanna 17 42.5 38 40.9 Organic farmland 12 30 31 33.3 Inorganic farmland 11 27.5 24 25.8 Total 40