Impact of Agroforestry Practices on Vegetation Diversity and Structure in Pesawaran, Indonesia

Plant species, including those utilized for agriculture, livestock, fishing, and forestry, and featuring multiple strata of canopy. Agroforestry has been widely adopted across the globe for an extended period of time, consistently aiming to enhance the economic well-being of local communities while simultaneously conserving agricultural land for environmental sustainability [1-3]. Agroforestry is also regarded as a means of enhancing biodiversity on a national and international scale while contributing to the development of a sustainable economy [4]. In contrast, agroforestry has been referred to as practical agroecology [5], and its management was based on an approach grounded in ecological principles. Therefore, by demonstrating diligence in this regard, the preservation of the environment will be upheld. Agroforestry success has become contingent upon a number of elements, including the selection of suitable plant varieties, the upkeep of the plants, the availability of markets and institutions, and plant maintenance [6]. The agroforestry system has been widely implemented in forest areas in Indonesia. Agroforestry plays a significant role in Indonesia as well, boosting income, promoting environmental stability, and ensuring food security. Agroforestry in Indonesia contributes to food security on a number of Indonesian islands [7].

The community uses an agroforestry technique to manage a large number of protected woods. Because the community is restricted by a forest land use permit in social forestry (HKm), which permits the community to manage forest land to increase community welfare by not chopping down trees, the agroforestry system is typically found in forested areas.

Hkm is a social forestry scheme that implements an agroforestry system. According to the Republic of Indonesia's Minister of Environment and Forestry's Regulation NO.P.83/MENLHK/SETJEN/KUM.1/10/2016, HKm is a state with authority for the welfare of its citizens. HKm is a form of legality in the use of state forests for the community. In order to lessen tension amongst the communities surrounding the forest, HKm aims to conserve the forest while growing the community's social economy. For many years, protected forest Indonesia has been using HKm various changes to achieve the desired goals [8, 9]. In Indonesia, HKm first started providing HKm permits to the community in 1995. Although until now not all protected forests in Indonesia have permits to manage HKm land. The protected forest record of the 20 Pesawaran Forest Management Units (KPH) in the province of Lampung is one example.

In addition to managing the 20 protected forests on the Register, the Pesawaran Forest Management Unit (PFM) of Lampung Province has long combined plantation crops, forestry, and agriculture to create a sustainable agroforestry pattern. Like durian, nutmeg, chocolate, and cardamom, it has long been a superior product for the community, but it didn't get a HKm permit until 2021The property at the 20 KPH Pesawaran registration has a vegetation structure that has already developed into several structures that is a bottom structure that is home to cardamom trees, an upper structure that is occupied by candlenut durian plants, and a middle structure that is occupied by nutmeg and areca nut plants. This arrangement is almost exactly like a natural forest. It takes decades for a vegetation structure like this to grow. Numerous studies have been conducted about the species composition of land used for agroforestry. Recently, great scientific interest has been devoted to examining plant species composition in agroforestry lands [10-14]. However, no research has been carried out on the list of 20 Pesawaran KPHs, and previous research has only focused on analyzing plant types without integrating plant type structure, even though the examination of plant stand structure is equivalent. Thus, the purpose of this study is to identify the plant stratum and examine the vegetation of register 20 in Pesawaran Regency, Lampung Province.

3.1 Analysis of agroforestry plant composition in Register 20 Pesawaran Regency

According to the findings shown in (Table 1), a total of 28 plant species were identified on the agroforestry site of Register 20 KPH Pesawaran, Lampung Province. The classification of plants encompasses four distinct groups: woody plants, MPTS plant types, agricultural plant types, and other types. The woody plants in this category are Bayur (Pterospermum javanicum), Dadap (Erythrina variegata), Sengon (Albizia chinensis), Waru (Hibiscus tiliaceus) dan Cempaka (Magnolia champaca). The MPTS plants include Randu (Ceiba pentandra), Jengkol (Archidendron pauciflorum), Nutmeg (Myristica fragrans), Durian (Durio zibethinus), Candlenut (Aleurites moluccana), Rambutan (Nephelium lappaceum), Petai (Parkia speciosa), Jackfruit (Artocarpus heterophyllus), Duku (Lansium domesticum var. duku), Clove (Syzygium aromaticum), Areca nuts (Areca catechu), Langsat (Lansium domesticum), Mango (Mangifera indica). The agricultural crops include, Cocoa (Theobroma cacao), Coffee robusta (Coffea canephora), Cardamom (Elettaria cardamomum), dan Chilli (Capsicum annuum). Additional examples include paku-pakuan (Pteridophyta spp), sengganen (Melastoma sp), Landri (Bridelia monoica), walur (Amorphophallus variabilis) dan, senduduk (Melastoma hirta). Agroforestry land exhibits several typologies, as supported by empirical findings [3, 20]. Based on researches:

According to Lehmann et al. [21], the analysis conducted using the IFNS system reveals that the utilisation of different combinations of plants and trees leads to differences in production levels, resulting in varying degrees of productivity. The use of an agroforestry system for planting has a beneficial effect on the preservation of biodiversity and serves as a socio-economic resource for the community [22].

Plants with distinct strata exhibit varying growth forms, and each stratum within a community may consist of diverse morphological categories of individuals [23]. The determination of the canopy strata was contingent upon the specific field conditions observed. Consequently, the borders of each observation area will vary according to the specific growing conditions. Nevertheless, the analysis distinguishes between saplings, seedlings, poles, trees, and other categories by considering their pace of growth [24]. At Register 20 KPH Pesawaran, Lampung Province, the forest area exhibits varying levels of density, frequency, dominance, and IVI across different plant species and growth stages. Specifically, durian plants have the highest values in these parameters during the mature phase, cocoa plants during the pole phase, cardamom plants also during the pole phase, and bayur plants during the seedling stage.

The density of plant species has a direct influence on the soil quality. According to Leonika et al. [25], the density of vegetation in a certain land cover exerts influence on the soil quality and the surrounding ecosystem. Increased vegetation density positively affects soil porosity. Agroforestry systems, which entail growing various plant species on a single piece of land, have a substantial impact on the livelihoods of people living in wooded areas [26].

The primary plant species found in Register 20 KPH Pesawaran, consist of durian, cocoa, nutmeg, and bayur. However, while taking into account the whole, the MPTS kind of plant remains the most widely grown by the community. The MPTS plant is a multifunctional plant that utilizes not only its wood, but also its fruit, leaves, and other stem components. Based on researches by Dobo et al. [27] and Lehmann et al. [21] provided evidence that the MPTS plant species exhibited dominance in forest zones. Forest-dwelling communities highly preferred MPTS plants. Register 20 KPH Pesawaran cultivates MPTS plants that fulfill the community's needs for fruit, flowers, seeds, and other resources, while also producing extra income when they are sold.

Table 1. Results of analysis of plant types at Register 20 KPH Pesawaran, Lampung Province

IVI the highest plant at the tree level is the durian plant, while at the poles level it is the cacao plant, and at the saplings level it is the cardomon plant, and at the seedlings level it is the bayur and jengkol plants. Based on (Table 1), the highest level of plant diversity in the tree, polish and sapling phases is the type of plant cultivated by registered farmers in 20 Pesawaran Districts. This is because the choice of plant types on agroforestry land is the type preferred by the local community [15]. Meanwhile, the highest types of plants at the seedling level are bayur and jengkol plants. Bayur plants are a type of woody plant, the number of woody plant types at the seedling level of agroforestry land is in register 20 because of the government's obligation to plant woody plants on agroforestry land in forest areas.

The analysis result value has been calculated using the summed dominance ratio (SDR) technique [28] following the identification of the dominant plant species in each measuring plot. The SDR (Species Dominance Ratio) are a mathematical method that considers the relative density, relative frequency, and relative dominance of a species to determine the most important plant types in a specific measurement plot [29]. In order to precisely assess the most prevalent plant species within a given area, it has become crucial to possess knowledge of the SDR (Species Dominance Ratio) value. The investigation produced the SDR values, which are presented in Table 2.

The Register 20 KPH Pesawaran tree phase exhibited the highest Standardized Difference Ratio (SDR) value of 40.17% among durian plant varieties, as indicated by the data in Table 2. This occurs because wealthy Register 20 KPH Pesawaran farmers often cultivate durian. The durian plant was an example of an MPTS (Multi-Purpose Tree Species) plant that contributes to the local economy through fruit production. Among the plants seen during the pole plant phase, cocoa plants exhibited the highest SDR value, measuring at 56.30%. Due to the prior cultivation of cacao plants by the community, the agroforestry planting strategy implemented by Register 20 KPH Pesawaran, farmers have resulted in the prevalence of cocoa plants. The SDR value of 23.03% was the highest among cardamom plants during the seedling phase. Register 20 KPH Pesawaran farmers often cultivate cardamom due to its low light requirements, which makes it a suitable option for agroforestry areas [30, 31].

The level of authority over the living and nonliving elements of the land increases in proportion to the SDR value [32]. According to Suwinda et al. [28], dominance in a specific area is established by the plants that have the highest level of control over the ecosystem. Boiko and Dementieva [33] observed that it can take many years for dominating plants to establish themselves in forest regions. Nevertheless, the involvement of landowners will expedite the formation of pores and dominant plants on agroforestry land [29]. The Shannon-Weiner diversity index (H') was employed to assess the species diversity value, alongside the SDR value. One of the research findings is the H' value, which can be shown in Table 3.

Table 2. SDR dominance value

Table 3. Diversity Index (H’) per level growth

The subsequent metric, known as the Diversity Index (H), measures the extent of diversity within Register 20 KPH Pesawaran. The Diversity Index can be defined as: A value of 1≤ H≤ 3 indicates a significant level of diversity, while a value of H < 1 indicates a low level of diversity. Register 20 KPH Pesawaran H diversity index indicates that seedlings exhibit the largest concentration of hydrogen (H) content during their growth period. This allows farmers to perpetually establish agroforestry plants—a hybridization of agricultural and forestry vegetation—on agroforestry land as a means of regenerating non-productive plants. Aside from that, the soil will grow more fertile the more seedlings there are, which is also consistent with D’Hervilly et al. [34] showing that different kinds of herbaceous plants can improve soil fertility. During the progression from sapling to pole and then to the mature phase, there are few disparities. Furthermore, research conducted by studies [35-37] has shown that agroforestry systems have a minimal or negative impact on forest variety. The vertical extent at which a species thrives can significantly influence its geographic range.

3.2 Stratum on agroforestry land Register 20 Pesawaran Regency

The height of a plant directly influences its overall dimensions. The goal of the plant height assessment, which is done at every stage, is to identify the layers of vegetation on the Register 20 KPH Pesawaran the agroforestry land. The research findings pertaining to measurements are shown in Table 4.

Table 4. Stratum on agroforestry land

The stratum of the Register 20 KPH Pesawaran agroforestry area was assessed, and measurements of the height of each plant species in each phase yielded the following results. The tree phase reveals that the durian tree stands as the tallest, reaching a height ranging from approximately 14 to 30 metres. These findings indicate that the topmost layer of soil on this site consists primarily of durian. In addition, the pole phase indicates that the langsat and durian varieties are the tallest plants. During the sapling phase, the plants present are jackfruit and petai. In the seedling phase, the plants that can be found include cloves and kapok. The configuration of the stratum and the botanical composition of the utilised plants can impact the variety of species present inside it [38]. In addition to measuring the height of the tree, the diameter of the plant is also assessed in order to calculate the pace of growth for each individual plant.

The findings of horizontal measurements, obtained by measuring the diameter of the plant at each stage of growth, are as follows. Candlenut trees reach a maximum diameter of 75.4 cm in their adult phase. The plant species with the largest pole diameter is observed in the sengt and jengkol plants, measuring 18.4 cm. During the sapling phase, jengkol plants have the largest diameter, measuring 9.3 cm.

The Register 20 KPH Pesawaran agroforestry area has been divided into four Stratum, namely stratum B, C, D, and E, based horizontal measurements of the plants. If a plant has a height above 30 m, it has been categorised as stratum A, if it is tall. According to study [39], plants that are between 20-30 m tall are categorised as stratum B. Plants with a height of 4-20 m are categorised as stratum C, while those with a height of 1-4 m have been deemed part of stratum D. Finally, plants that were below 1 m in height are included in stratum E. Stratum B has been filled with MPTS plants. Stratums C and D contain agricultural crops such as nutmeg, cloves, cocoa, and coffee, whereas Stratum E has been filled with cardamom and understory plants [40]. Register 20 KPH Pesawaran consists of four out of the five available stratum. Register 20 KPH Pesawaran xhibits a plant profile that closely matches that of a natural forest. This has been consistent with the assertion made by Murniati et al. [41].

The Agroforestry technique implemented by Register 20 KPH Pesawaran involves a mixed/random pattern of plant components. The haphazard arrangement of plants and the lack of planned positioning of woody plants on the land result in the formation of this random pattern. Agricultural plants were interplanted in a mixed arrangement with woody plants to utilise the woody plants as shade providers for low canopy plants. The agricultural crops that have been merged include cocoa, coffee, cloves, and nutmeg. Meanwhile, the woody plants that have been included in this combination are durian, avocado, melinjo, kapok, mango, and candlenut. This leads to significant fluctuations in crop productivity due to the diverse range of plant species cultivated on the site [42].