Ants Diversity between Organic and Conventional Farm

COMPARISON OF ANTS DIVERSITY BETWEEN ORGANIC AND CONVENTIONAL FARM AT MACHARE COFFEE ESTATE

Erick Michael Swai

Wildlife Department, College of African Wildlife Management, Kilimanjaro, Tanzania

ABSTRACT

Ants play a vital-ecological role as they influence soil movement, nutrient cycling and water availability in their habitat. Habitat destruction and the use of Agrochemicals are regarded as among the factors that affect the diversity of ants. Machare Coffee Estate is one of the farms which practice both organic and conventional farming. To reveal whether there is a difference in diversity between these two practices this study was conducted at Machare Coffee Estate for three weeks. The study used four transects of 80 m with four quadrants of 10x10 m within it, where 6 pitfall traps with an inter pitfall distance of 3 m were laid down per quadrant on both sites. A total number of 96 pitfall traps were used per site. A total of 2381 ants from five subfamilies were collected. Ant's diversity was analyzed by the Shannon Wiener index and a t-test was used to test the hypothesis. The results showed organic farm has a high diversity (H'= 2.72), abundance (1615) and ants species richness (16). This might have been caused by different factors like there were more prey species for ants,organicsoilpromotesnestingmaterialsfor antsandavailability of water sources around the area. Diversity and abundance of ants differed significantly between the two sites (P=0.00364 and P=0.002) respectively. This study contributes knowledge in the management of ants as an important species in an ecosystem, since they are ecosystem engineers. The study recommends on no use or the use of organic chemicals and organic manures which are healthy to the ecosystem to maintain a diversity of not only ants but all biological resources beneficial to human and nature at large.

Keywords; Ants, diversity, conventional farming, organic farming

CHAPTER ONE

1 INTRODUCTION

1.1 Background Information

The importance of biodiversity conservation is recognized worldwide (Widhiono et al., 2017). Throughout the world, conservationists are struggling to avert, extinction of biodiversity resources (Getachew et al., 2015). Extinction will cause impoverished ecosystem functioning (Drummond & Choate, 2011). Terrestrial ecosystems, for example, the agroecosystem support the greatest global biodiversity (Armbrecht et al., 2006) and thus biodiversity conservation is an important goal for environmental management (Benckiser, 2010).

The increase of the human population has led to the demand for land used for agricultural activities, settlements, and also livestock keeping (Humble et at., 2009). Previously organic agriculture has been mostly practised a type of agricultural practice with the aim of augmenting ecological processes that foster plant nutrition yet conserve soil and water resources (Diao et al., 2010).

Organic systems eliminate the use of agrochemicals and reduce other external inputs to improve the environment and farm economics (Lassau & Hochuli, 2004). The existing yield variation caused the system to shift from organic to conventional (Offenberg, 2015). On the other hand, conventional agriculture involves the use of agrochemical and it is known that conventional agriculture leads to high crop productivity than organic agriculture which will satisfy the needs of expanding the human population (Pimentel & Burgess, 2014). However organic farming supports higher biodiversity than conventional farming due to the presence of soil organic matter which adds nutrients needed for the survivor of an organism (Söderlund & Söderlund, 2013). Moreover, the role of the environment in maintaining biodiversity cannot be ignored so environmental management is an important thing. (Hernandez-Ruiz & Castano-Meneses, 2006).

Several studies across the world have documented that agricultural intensification has led to a significant reduction of biodiversity (Dad et al., 2018). Heavy agricultural reliance on synthetic chemical fertilizers and pesticides is having serious impacts on public health and the environment (Offenberg, 2015). For example, more than 90% of US corn farmers rely on herbicides for weed control (Philpott et al., 2006) and it has been demonstrated to have a strong influence on the abundance and the diversity of arthropod communities (Underwood & Fisher, 2006).

Ants are classified in a single-family, the Formicidae, within the order Hymenoptera, and are social insects that have been developing successfully since the Cretaceous (Hernandez-Ruiz & Castano-Meneses, 2006). The identified living ants belong to 16 subfamilies, 296 genera and 15000 species, around 10000 of which are described (Drummond & Choate, 2011). However, there is an extremely high number of ant species still outstanding to be discovered and described (Folgarati, 1998). Imperfect classification of some groups (especially due to the presence of sibling species) complicates biodiversity assessments even further. The geographical regions with the greatest number of genera decrease in the following order: Indo-Australian, Neotropical, Oriental, Australian, African, Palearctic, Nearctic, and Malaysian, among which the Neotropical and African areas have the greatest number of endemic genera, and the Nearctic and Oriental the least (Lassau & Hochuli, 2004). Ants can be found in any type of habitat from the Arctic Circle to the Equator, although they are absent from Iceland, Greenland, and Antarctica (Philpott et al., 2006). The number of species declines with increasing latitudes, altitudes, and aridity (Rwegasira et al., 2015). Despite the fact that tropical areas and continental forests are amongst the poorest known, these areas have the greatest recorded species diversity of ants (Campos et al., 2007).

Ants show a great role in an ecosystem by carrying out different functions (Fuller et al., 2005). Epigaeic ants influence soil movement, nutrient cycling, and water availability all over their habitats (Minarro et al., 2009). Through the drive of subsoil to the surface, ants increase cation exchange and the amount of available water for plant absorption (Van Mele et al., 2009). Movement of soil during nest and tunnel building and the gathering of organic matter in the form of ant prey and nest-building materials results in physical and chemical changes to the soil (Armbrecht et al., 2006). Physical impacts of ants on soil include an increase in soil macroporosity and a decrease in bulk density, which results in soil aeration and permeability of water. Studies have proved an increase in organic matter, phosphorus, nitrogen, and potassium in ant nests when compared to the surrounding soil (Benckiser, 2010). Ants act as pest control in agriculture (Armbrecht & Gallego, 2007). As generalist predators, ants are capable of switching prey species when they have depleted a resource (Schultz & Brady, 2008). Ants may also control pest populations through the interruption of feeding and oviposition (Van Mele et al., 2009).

In Africa, several studies have investigated the effect of agriculture on a diversity of ants assemblage. Most have looked at either determination of abundance (Hole, 2005) or ants as a biological indicator of habitat change (Armbrecht & Gallego, 2007). In Uganda, the study about ant was done in plantain farms where it looked on the soil microfauna abundance in non-agro forestry farms with that of agroforestry farm (Fuller et al., 2005).

In Tanzania several studies focused on other aspects, a study done at Mahale Tanzania explained about plant-ant relationships where it showed how ants are used as the source of food to other animals (Fuse, 2013). Also, the study was done on the elevation gradient of Mount Kilimanjaro about variation in nutrient use by the foraging ant's communities where it explained that ants forage in the natural ecosystem than managed ecosystem (Peters et al.,2014).

1.2 Problem statement and Justification

Ants like any other living organism, require essential ingredients for their survival and reproduction (Campos et al., 2007). Ants require vitamin, amino acid, carbohydrate, and water; all these essential nutrients are found in the soil with organic matter (Söderlund & Söderlund, 2013). In order to provide good ecosystem service at a high rate, ants need a favourable environment and areas where there is no disturbance including diseases and agricultural products like fertilizers and pesticides (Philpott et al., 2006).

The increase of the human population worldwide has led to a high demand for food which made farmers make sure that crop productivity increases so as to fulfil the needs of people (Offenberg, 2015). Despite their importance, the environment now is disturbed largely by the agricultural practices as farmers do use agrochemicals in their farms so as to increase crop productivity (Norris et al., 2010). This might make habitat unfavourable for ant and might decrease the diversity of ants.

Continued use of agrochemicals will, therefore, decrease ants richness and abundance which will consequently their role in ecosystem structure and functioning (Lassau & Hochuli, 2004).

The diversity of ants in conventional and organic farms has not been investigated in Tanzania, therefore, the study aims at investigating that and provides knowledge for ants conservation. Machare Coffee Estate is among unique plantations in which both conventional and organic farming of coffee are performed. The study contributes to the existing body of knowledge on the influence of these farming practices on ants' diversity. Knowledge about ants diversity is useful for the conservation of other species which associate with ants in the ecological chain (Folgarati, 1998).

Therefore from such a gap in knowledge, this study intends to compare the diversity of ants in organic and conventional farms. Moreover, the findings from this study will aid in biodiversity management and conservation in the area in particular.

1.3 Objectives

1.3.1 General Objective

- To compare ants diversity between organic and conventional farms.

1.3.2 Specific Objectives

- To determine ants diversity between organic and conventional farms
- To determine ants abundance between organic and conventional farms
- To determine ants species richness between organic and conventional farms

1.4 Hypothesis

1.4.1 Null hypothesis

- Ho 1:There is no significant difference in the ants diversity between organic andconventional farm
- Ho 2: There is no significant difference in ants abundance between organic and conventional farm.

CHAPTER TWO

2 METHODOLOGY

2.1 Study area description

Machare Coffee Estate is the first Rainforest Alliance Certified in Africa and is committed to upholding sustainability in all its practices. It is the highest active coffee farm on the slope of Mt. Kilimanjaro.

2.1.1 Geographical Location

It is located at the foot of Mt Kilimanjaro, near the Kilimanjaro Forest conservation area in Northern Tanzania. It is also right below the Rainforest, nestled between two rivers creating a unique microclimate. The altitude of the area is 1350m to 1550m and the total size of the farm is 230 ha. Machare coffee estate based on the production of coffee whereby both organic and conventional farming is practised. In addition to valuing sustainability on their farm, Machare estate also runs a number of projects include tree planting, providing eco-friendly stoves, coffee quality improvement, and water management.

2.1.2 Climate

There are double rainy seasons at Machare Coffee Estate area, long rains often start from March to July and the shorter rains start from November to January. The annual rainfall range is 1000mm to 1700 mm. The temperature varies seasonally, ranging between 17°C and 26°C throughout the year.

2.1.3 Vegetation

Machare Coffee Estate area is characterized by different vegetation types including tree-crop vegetation, river line vegetation, and shrubs.

This image got removed by the editiorial team due to copyright reasons.

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Figure 1: A map of the study area

2.2 Reconnaissance survey

In advance of data collection, a reconnaissance survey was done with the intent of gathering information as well as acquainting with the study area by directly observing the sampling site, vegetation cover and accessibility relative to the sampling points area.

2.3 Sampling Design

2.3.1 Sampling Site

Sampling of ants was conducted in two different sites located in the same area (Machare Coffee Estate). The sites were selected based on the activities conducted in the area where both organic and conventional farming was practised. These sites were organic farm and conventional farm.

2.3.2 Method

The pitfall trap technique is suitable for capturing ants and commonly used methods to survey surface-active invertebrates (Rwegasira et al., 2015). In each habitat, four lines transect with four quadrants per each were established with pitfall traps being allocated within the quadrants. The technique involves the use of a plastic cup of 8 cm, depth 10 cm in diameter. The cup was placed into the hole dug into the soil in such a way that the rims of the cup become flush with the ground surface to allow for smooth movement of ants towards the hole and traps were visited after two days every morning within all period of data collection. Traps were half-filled with preservative liquid (formaldehyde) to avoid escape by captured insects.

2.3.3 Procedures

Transects were located 20 m from the road to avoid edge effect, four transects of 80 m length with inter transect distance of 20m were established in organic farm and four of the same length in conventional farm at Machare Coffee Estate. In each transect, four quadrants of 10x10 m with an inter quadrant distance of 20 m (see figure 2) were established. In each quadrant, 6 pitfall traps with an inter pitfall distance of 3m were sunken in the soil, in total 96 pitfall traps per site. The traps were half-filled with soapy water to reduce surface tension. Traps stayed permanently on both sites for three weeks.

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Figure 2: Sampling design per site

2.4 Data collection

Ants were collected for three weeks using pitfall traps. Data were collected once in a day, from 8:00 am to 11:00 am after every 48hours as suggested by (Hole, 2005). Specimens were collected by carefully removing the specimen from each pitfall trap in all study sites without disturbing the cup and data was recorded per quadrant on each transect. Insects were killed using ethyl acetate in the killing bottle before being identified and preserved in the 70% ethyl alcohol. Techniques used to collect insects are similar to those described by (Rwegasira et al., 2015).

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