Analysis of Diversity and Abundance Soil Insects in Taman Gumi Banten, Forest of Wanagiri Village, Buleleng

The forest in Wanagiri Village about 1.055 ha, and almost 250 ha of that forest managed as “village forest”. Village forest is the forest that is used by villagers, and in addition to being a natural reservoir area and maintaining water availability. This research aims to explored diversity and abundance soil insects that play a role in maintaining soil fertility. Surface insects were collected using the pitfall trap method, while infauna or ground insects were collected using the core method. The site of this research consists of 8 plots each site with random purposive sampling. The results showed that macrofauna species were higher than infauna. The diversity Index of soil insects is in the low category (0


Introduction
Wanagiri Village is one of the villages located on the southern side of Buleleng Regency, Bali. Wanagiri Village has a strategic role seen from an area of 15.75 km2, topographically located at an altitude of 1,220 m above sea level [1], its location is directly adjacent to Buyan Lake and the landscape is mostly hilly with a fairly dense forest ground cover. so that Wanagiri Village has a role and potential for development as a tourism area, conservation of springs, forestry, and plantations.
The forest in Wanagiri Village has an area of 1,055 ha, of which 250 ha of forest is managed by the village as a tourism forest, where one of the areas is used for Banten plant tourism and as a place to support ceremonial facilities so it is called the Taman Gumi Banten Forest (Gumi Banten Park) [3]. The location of the Banten Gumi Park Forest is located on the eastern margin of the forest area of Wanagiri Village. The forest of Taman Gumi Banten has 68 useful plant species, with a density of 348 individuals/ha and the diversity index is classified as moderate [2]. Fertile and sustainable vegetation is also determined by the fauna present in the soil as decomposers of soil organic matter or decomposers [11][12][13][14].
The role of these decomposer insects is often forgotten in forest conservation studies, the existing research only focuses on studies on the diversity and distribution of forest vegetation, including the Wanagiri Village Forest. Studies on the diversity of soil insects in the Wanagiri Village Forest have never been carried out, even though if we want to manage what lives on the ground we cannot escape the knowledge of what organisms live in and on the soil surface, because interactions must occur. Therefore, this study was conducted to examine the diversity of soil insects and their abundance in the forest area of the eastern part of Wanagiri Village, namely the Taman Gumi Banten Gumi Forest.

Method
This research is an exploratory research, carried out to identify soil insects in the forest of Taman Gumi Banten, Wanagiri Village and measure the abundance of these insects and look for interactions or their role in the local ecosystem.

Sample collection method
Insect sampling was divided into 2, ground insects and underground insects. Surface insects were collected using the pitfall trap method, while infauna or insects in the soil were collected using the core method. The sampling site is divided into 4 sites. Each site consists of 8 plots. The next step is to measure the temperature, pH, water content, and observe the texture and color of the soil.

Data analysis
The data analysis of this research includes: a. Identifying soil insects collected using identification keys Borror et al. (1996) [22], Soil Animal Ecology Book [15], and online databases.
b. Determining the dominance index of a type of soil insect against its community.

Result
The results of the study are presented in the following table.

Discussion
From the data presented in Tables 1 and 2, it was found that the number of insects in the forest soil of Taman Gumi Banten was 57 types of insects on the ground with a total of 157 individuals, and 16 types of small insects in the soil as many as 26 individuals. The most common insects found were from the Order Coleoptera and then the Order Collembola. The types and numbers of individuals found at each site tend to be different, and each site has different types and numbers of soil insects. So from the data, it can be said that the population tends to clump. This insect distribution occurs due to the influence of the environment [24] and the character of the insect population [25].
The order Coleoptera from the family Staphylinidae was the most common soil insect found during this study. This group of these insects has an ecological role as predators of other smaller insects. During this research, the organic matter found in the soil was very abundant, seen from the number of leaf residues found in the forest area. Leaves are a source of organic matter used by caterpillars and other decomposers as a food source. This causes predation interactions that occur, namely the abundant food source of Staphylinus Diversity is identical to the stability of an ecosystem, if the diversity of an ecosystem is relatively high, the condition of the ecosystem tends to be stable [23]. Ecosystem environment that has diversity disturbance tends to be moderate, in the case of polluted ecosystem environment species diversity tends to be low. In the forest area of the Taman Gumi Banten as the research location, almost no process of forest destruction or pollution was found, this happened because the forest area was located at an altitude and far from the residential area of the villagers. However, the low diversity index occurs due to the limited duration of sampling in the forest and due to high rainfall so that the insect catches in the pitfall are not optimal.
Environmental factors or soil parameters can affect the number and abundance of species in a habitat. In this study, measurements of temperature, pH, moisture content, texture, and soil colour were carried out ( Because most of the pH levels in each plot are less than 7, the average pH is classified as acidic but there is a pH level that is close to 7 which means that the pH is neutral while the pH is 5 and below insects can still live, at that pH ants and grasshoppers are often found.
However, infauna organisms are rarely found at pH 7 and below because these organisms live in the soil, which means that insects in the soil cannot live in acidic soil levels, so infauna organisms are rarely found. The cause of acidic soil pH at the research site is because the soil texture is like peat with a slightly acidic pH, this is because this soil contains very high organic matter originating from parts or plant remains that fall to the ground so that the activity of decomposition of organic matter is also high. where in the process is always accompanied by the loss of calcium elements in the soil.
In addition to these factors in the study area experiencing the rainy season, high rainfall can result in the decomposition of nutrients in the soil so that naturally the soil will become acidic. Moisture content includes humidity, on insects the effect of humidity is direct. Many types of insects have a narrow tolerance for humidity. If the environmental conditions are very high humidity can cause the death of insects or migrate to other places.
Dry conditions sometimes also reduce certain species due to reduced population. Besides that, humidity also controls the activity of moving and eating. moisture content at all stations is 70%-85%. Soil Texture, based on the research location, it was found that the texture of the existing research sites was on average loose textured. The range is still in good condition because it is very suitable for the location of insect life. Soil colour, from the results of research found at the research site, it was found that the colour level of the soil was blackish brown, where in standardization it was found that this was still in the good category for insect life.

Conclusion
The number of soil insects in the Taman Gumi Banten Forest is as many as 57 types of insects on the ground with a total of 157 individuals, and 16 types of small insects in the soil with a total of 26 individuals. The order Coleoptera of the family Staphylinidae is the most common soil insect. The diversity Index of soil insects is in the low category (0.355987). Soil parameters indicate the abundance of organic content contained, so further research is needed to obtain more detailed soil insect diversity.