Geospatial approaches for formulating multisystem silviculture in the tropical forests

The Indonesian Ministry of Environment and Forestry (MoEF) issued regulations that allow the use of multiple silvicultural systems throughout a single period of a forest management work plan, known as multisystem silviculture (MSS), to increase the productivity and economic value of forests. However, certain technical issues still need to be resolved before an MSS can be successfully implemented on-site, particularly in terms of scheming the silvicultural system and selecting the appropriate site. This study developed silvicultural systems based on the modelling of geospatial data on current land cover, forest function, slope, and erosion risk. In this study, forest harvesting techniques (prohibited, selective, and clear-cutting) and regeneration approaches (natural, enrichment, and line planting) were formulated by overlaying four thematic maps and applying modelling rules. For specific locations, overlay thematic modelling maps of forest harvesting and regeneration techniques have been verbalized as MSS, such as selective cutting with enrichment planting, selective cutting with line planting, clear-cutting with intensive planting, and many other systems. The results of this geospatial modelling will assist forest managers in creating forest management plans with MSS within particular forest objectives. Additionally, this study supports policymakers in rising technical procedures for implementing multisystem silviculture.


Introduction
In the past 200 years, forest management arrangement has only been focused on the productive purposes of forest ecosystems [1], mostly for exploiting the timber [2].The primary goal of forest management, as established by landowners and/or other forest stakeholders [3], is to maximize economic gain [4].Currently, the forest management planning also highlights climate change adaptation [5] and mitigation [6], improving carbon stocks [7,8], and growing the density of tree stands [9].According to the various authorities that exist, the goals of forest management may also modify over time [10].By taking into account the changing environmental conditions [11,12] based on landscape scales [13,14,15,16] where large-scale deforestation and forest degradation arisen [17,18,19], the traditional forest management systems also need to be modified in order to achieve the new objectives [20,21,22,23,24].
In order to achieve the various forest management goals [25,26] and the climate change mitigation targets [5,27], the systems of silviculture for managing forests have also improved [28,29], including in 1315 (2024) 012078 IOP Publishing doi:10.1088/1755-1315/1315/1/012078 2 formulating timber harvesting practices [30,31] and forest regeneration approaches [4,32] focused on the forest landscape scales [33,34].Silvicultural actions are regarded as real techniques for increasing timber output while maintaining high conservation values and ecosystem services [35].Silvicultural systems generally combine several silviculture techniques [36] that are planned for the entire forest rotation [37] in order to reassure forest management systems from historical circumstances [38,39] towards specific goals [40].
Silvicultural system for managing forests in Indonesia, such as Tebang Pilih Tanam Indonesia/TPTI (selective logging with enrichment planting), Tebang Pilih Tanam Jalur/TPTJ (selective logging with line planting), and Tebang Habis Permudaan Buatan/THPB (clear-cutting with intensive planting), have been regulated [41] by the Indonesian Ministry of Environment and Forestry (MoEF).In recent years, a single forest concession has been able to use many silvicultural systems [42], known as the multisystem silviculture (MSS).The government hasn't, however, formally outlined the processes or criteria for handover each silvicultural system to the suitable location.Additionally, these silvicultural techniques can only be used in state forests that have a production function; they are not permitted in state forests that serve conservation or protection purposes or in private forests.State forests are those set aside by the government, whereas private forests are those that are certified and owned by private, public, or community entities that cover non-forested areas [43].
The aims of this study were to formulate multisystem silviculture for managing tropical forests in East Kalimantan Province using geospatial data modelling.The silvicultural systems were formulated in state and private forests where forest management is planned to achieve forest conservation, protection, and production goals.

Study area
The study area was conducted in East Kalimantan Province, where is located on Borneo Island with coordinates between 2°33' N and 2°25' S and between 113°44' E and 119°00' E. As the third-largest province in Indonesia with a total area of 12.73 Mha (6.7% of Indonesia), East Kalimantan has a land area of 12,62 Mha and inland water of 112,802 ha [44], which consists of three cities (Samarinda, Balikpapan, Bontang) and seven districts (Berau, Kutai Kartanegara, Kutai Timur, Kutai Barat, Paser, Mahakam Ulu, Penajam Paser Utara).As one of the target provinces for reducing carbon emissions, East Kalimantan is a leading member of the GCF (Governors Climate and Forests Task Force) and has been selected as the focal province for Indonesia's efforts to reduce deforestation through the Forest Carbon Partnership Facility's Carbon Fund and the Green Growth Compact [45,46,47].The study area had significant logging, oil palm plantations, and agricultural expansion [48,49,50,51,52].Moreover, the coal mining site is omnipresent, and more than 630 open-pit coal mines are abandoned [53].Van der Laan et al. [54] and Verstegen et al. [55] reported that land use changed in about one-third of Mahakam Ulu and Kutai Barat between 1990 and 2009, bringing about a 9% decline in forest area as a consequence of rapid land development.Moreover, in the National Mid-Term Development Plan 2020-2024, the new capital city of Indonesia will be moved to East Kalimantan to equalize community welfare between regions [56].

Collecting geospatial data
Geospatial datasets (Figure 1) were gathered from national and provincial governments, and several references served as the basis for this study.The Indonesian Ministry of Environment and Forestry (MoEF) Decree No. 278 of 2017 [57] provides a forest area map.A land cover map for 2021 produced by MoEF using visual interpretation of Landsat images was collected in this research.The Center for Geospatial Infrastructure Information Development (CGIID) of Mulawarman University provides geospatial data on slope and erosion risk.All geospatial datasets were clipped into the East Kalimantan Provincial Boundary obtained from the Regional Development Planning Agency (BAPPEDA) of East Kalimantan Province.

Designing forest management objectives
The fundamental factors to consider when formulating silvicultural systems are forest management objectives [4,36,37,58,59,60].According to the previous study [61,62,63], the potential forests in East Kalimantan were around 9.5 million ha calculated from the forest areas designated by the government (89.49%) and forest-covered non-forest areas (10.51%).According to the current conditions of land cover, a forest area of 6.15 million ha revealed a well-functioning, as well as a non-forest area of 999 thousand ha covered by forests, was suggested to be targeted for forest management strategies, while a forest area of 2.4 million ha indicated deforestation and forest degradation was planned to be firstly replanted by forest restoration strategies (Figure 2).The multisystem silviculture formulated in this study is only focused on locations that are targeted for forest management.Three categories of forest functions (production, protection, and conservation) regulated by the MoEF [57] were used in this study to illustrate the goals of forest management.Private forest landowners should refer to government-regulated forest functions when deciding their management goals.This study settled three functions by considering geospatial datasets of land cover, slope, and soil, which were intended for the goals of forest management in private forests.A 2021 land cover map was used to show current land cover conditions.Geospatial datasets of the slope and soil erosion risk maps were used to prove the vulnerability of the forest to silvicultural practices (Table 1).Basically, all forested area covered by primary forests would be advised for conserving biodiversity, which was cited in the Indonesian President Instruction on forest moratorium [64, 65,66,67].Any forested area located on the extreme slope (>40%) and/or the highest-risk level of soil erosion areas would be proposed for protecting the sustainable forest ecosystem services, which was stated in the Indonesian President Decree No. 32 of 1990 on the protected area [68].

Formulating multisystem silviculture
Silvicultural systems were formulated by combining timber harvesting methods and regeneration techniques.Timber harvesting practices were categorized as forbidden logging, selective logging, and clear-cutting (Table 2) by taking into account the geospatial datasets of forest management objectives, land cover, slope, and erosion risk level.The Indonesian Forestry Law [43] states that selective logging is forbidden for purposes of conservation and protection, restricted for purposes of limited production, and permitted for purposes of production and convertible production.Any forested area that is covered by primary forests, is extremely sloping (>40%), or has a high risk of soil erosion was formulated for prohibited logging in order to support the goals for conserving the high values of forest (Indonesia, 2011a) and protecting the sustainable forest ecosystem services [68].Only the portions of the forested land that covered by plantation forest experienced clear-cutting method.Natural regeneration and planting (enrichment, line, and intensive) methods for regenerating forests followed timber harvesting actions and took into account geospatial datasets of land cover, slope, and erosion risk (Table 3).Natural regeneration followed the prohibited logging practice which was applied within the forested area covered by primary forest and/or located on the extreme slope (>40%) and/or highest-risk of erosion (the protected areas).Enrichment planting tracked the prohibited logging practice if it was not covered by primary forests and located separate from the protected area.Selective logging practice was followed by enrichment planting within the moderate slope areas (15-40%) and line planting within the flat to ramps slope areas (0-15%).The forested areas which were applied clearcutting practice should be followed by the intensive planting.

Forest management objectives
According to earlier research results published by Kiswanto et al. [62], the 12.7 million ha total area in East Kalimantan was divided into state forests (66.85%), private forests (7.85%), and non-forests (25.30%).This study did not change the objectives of the state forests referred to the MoEF Decree No. 278 of 2017 [57] and only formulated purposes of the private forest by considering the Indonesian Law on Forestry [43]. Figure 3 displays the management goals for the state forests, private forests, and nonforests.State and private forests were formed based on landscape information to achieve the goals of conservation (4.22%), protection (17.06%), and production (53.41%), whereas non-forest objectives were created for around 25.30% of the province as a whole.All maps would show the formulation produced by this study along with the specific locations targeted for forest restoration (18.55%) and non-forests (25.30%) for addressing the entire area of East Kalimantan Province, despite the fact that this study only formulated silvicultural systems for managing the forests of 7.15 million ha (56.15%).In order to create effective silvicultural systems within appropriate forest landscapes, determining the objectives of forest management systems is seen as the first stage [69,70,71].Although landowners have a right to set private forest management goals, different judgements made from the viewpoints of diverse stakeholders might lead to conflicts of interest, necessitating the need for more spatially based data to help landowners in their decisions [4,26,36].When developing silvicultural practices, the state and private forest management goals (Figure 3) were taken into consideration.This study was started to frame the objectives of private forests based on three functions mentioned on the Indonesian Forestry Law [43] using combinations of the current land cover form, slope, and erosion risk (Table 1).However, the MoEF only regulated the functions of the state forests [57] and did not custom any function for the private forests.According to Pohjanmies et al. [26], the goals of forest management show how natural resources may be used sustainably while still providing ecosystem services.According to Chazdon and Guarigueta [72] and Wollenberg et al. [73], the sustainable forest management takes into account the forest landscapes while determining the broad goals for each individual region [71].Even if a single forest stand can only reach a small goal at once, neighborhoods of forest stands and expansive landscapes can offer a stunning variety of ecosystem services to achieve bigger goals [74].

Timber harvesting practices
Figure 4 depicts the precise location of a number of timber harvesting techniques.Overall, logging techniques were often used in production forests while being mostly forbidden in forests designated for conservation and preservation.However, this research also established restrictions on logging inside the production forests that were located in protected regions (areas with the highest risk of erosion and/or steep slopes) and covered by high conservation values of forests (primary forests).This study calculated the prohibited logging for the 3.5 million ha of forested area, selective logging for the 3.2 million ha of forested area, and clear-cutting practice for the 0.4 million ha of forested area, which correspond to 27.39%, 25.37%, and 3.39% of the total province, respectively.These figures exclude the 2.4 million ha (18.55%) and 3.2 million ha (25.30%) of areas targeted for forest restoration activities.When creating sustainable forest management systems, it is important to comprehend the effects of timber harvesting practices on forest ecosystems [75].In this study, the formulation of timber harvesting practices was limited to the forest areas with a goal of producing timber, and it was suggested that these practices be banned in areas with a goal of conservation and preservation (Figure 4).To guarantee the sustainability of ecosystem services at the protected area and preserve the high values of biodiversity, this study also advised the decision-makers to prohibit any logging activity in the production forests located on the extreme slope and/or the highest soil erosion risk as well as covered by primary forests.The method used to manage the particular landscapes has a significant impact on preserving the high value of biodiversity in forests used for wood production [36].In Indonesia, forest managers are required to set aside 10% of their forest concessions for production as protected areas with steep slopes (>40%), the highest risk of soil erosion, and high conservation values (Indonesia, 1990).Some research [76,77,78,79,80] concentrated on how the harvesting may produce timber and avoid deterioration at the same time.

Forest regeneration approaches
Figure 5 depicts the precise area intended for the use of forest regeneration techniques.23.24 percent of the province's total (2.96 million hectares) were given priority for natural regeneration.2.59 million hectares (20.32%) were the area where enrichment planting was intended.1.17 million hectares (9.20%) were the area for which line planting was planned.A proposal for intensive planting was made for 0.4 million hectares (3.39%).The location goals for both forests and non-forests were also displayed on this map.The regeneration tactics used in this study (Figure 5) made it possible to artificially restore the forest successions in the logged area using a variety of planting methods (enrichment, line, and intense).For enrichment planting with high density and long-lived canopy trees, logged-over and second-growth forest areas provide excellent intrants [36].To sustain sustainable timber production [81] and prevent the decline of biodiversity [82], silvicultural interventions are needed to ensure that forest regeneration has been carried out in the logged forests.Without kind silvicultural command, succession in logging gaps could not be enough to generate sustainable timber yield [83].However, seeing that they will affect the diversity and structure of long-impacted ecosystems, silvicultural picks on artificial regeneration, mainly in taking silvicultural methods and tree species at the site levels, should be made with wisdom.

Multisystem Silviculture
Timber harvesting and forest regeneration are combined in silvicultural systems (Figure 6).This study determined the precise location for using three silvicultural systems governed by the MoEF: Tebang Pilih Tanam Indonesia (selective logging with enrichment planting) of 2.1 million ha (16.17%),Tebang Pilih Tanam Jalur (selective logging with line planting) of 1.2 million ha (9.20%), and Tebang Habis Permudaan Buatan (clear-cutting with intensive planting) of 0.4 million ha (3.39%).Figure 6.Specific site for implementing multisystem silviculture within state and private forests For handling conservation and protection forests as well as the protected area (the high conservation values, the extremely sloping, or highest-risk of soil erosion) within the production forest, this study formulated two kinds of silvicultural systems: prohibited logging with natural regeneration (23.24%) and prohibited logging with enrichment planting (4.15%).Table 4 showed the silvicultural systems formulated for reaching the many forest management objectives and landowners as well as the area targeted for forest restoration (18.55%) and non-forests (25.30%) to summarize the landscape strategies in the whole area of East Kalimantan.The timber harvesting practices and forest regeneration approaches combined into multisystem silviculture (Figure 6 and Table 4) demonstrate the forest management preparation applied in the forest management portions for reaching the various objectives.Forest management units for conservation was targeted for protecting the high biodiversity values inside the forest ecosystems [43] that should be managed by prohibiting timber harvesting caused forest biodiversity damage as well as ensuring natural regeneration or enrichment planting whichever needed for the sustainable forest.Enrichment planting in preservation forest was recommended to use the rare native species for enhancing the genetic diversity within the forest landscapes.Forest management units for protection was targeted for maintaining the sustainable protection supports of forest ecosystem [43] so forest managers must ban timber harvesting and might admit to produce only non-timber forest products from this forest extent.Although natural regeneration was prioritized in protection forest, enrichment planting method whenever unavoidable was suggested for using the native tree variety with deep roots accomplished to manage groundwater system, forbid soil erosion and water intrusion, and uphold soil fertility.Although forest management unit for production was principally targeted for producing timber [43] using the silvicultural systems set by the MoEF [41], this study further allocated some forest area for conservation and guardianship goals as the protected areas within the production forest [68].
Although the MoEF had planned the silvicultural systems in Indonesia, mainly for producing timber [41] and allowed a single forest management unit to apply multisystem silviculture [42], the technical actions for engaging the system in the accurate site have not been issued.This study formulated the appropriate silvicultural systems which could be applied within the suitable forest landscapes (Figure 4 and Table 4).The old-style viewpoints of silviculture approaches were only implemented for producing timber and thus have led some views such as other objectives do not require silviculture [84].However, many studies have confirmed that silviculture can also be performed for managing and restoring the multiple functions of forest [22,35,37,59,[85][86][87][88][89].The silvicultural systems formulated in this study was planned for reaching the various objectives including conservation and protection of the sustainable ecosystem services.Silviculture should be promoted in addressing the new targets of the sustainable forest management [90] for avoiding deforestation [91] and its impact on GHG emissions [92].

Conclusion
This study highlights the value of geospatial data in developing appropriate silvicultural systems and distributing suitable forest landscapes as a geospatial and technical understanding of the government's forestry policies.The appropriate silvicultural systems can also support climate change mitigation by managing forested landscapes and preventing deforestation and forest degradation.The government can apply the silvicultural systems developed in this study to indicate the best silvicultural practices when presenting forest concession authorizations under forest management units for different purposes.Forest managers must, however, provide detailed technical instructions for implementing silvicultural systems at the operational scale by considering non-spatial factors such as the quantity and type of trees to be planted as enrichment.
Private forest landowners have a variety of alternatives for managing their holdings for forest or nonforest purposes, primarily based on how such forests might financially benefit their livelihoods, whereas the government only controls the management of state forests.Because the forestland is outside the government-designated forest region and may be certified by private organizations, the government may not be able to persuade landowners to maintain their holdings as forests.It is advised that the government reward landowners who responsibly manage their own forests by offering incentives.Incentives can promote voluntary cooperation and increase landowners' commitment to preserving their wood.

Figure 1 .
Figure 1.Geospatial datasets of forest functions (top left corner); land cover map of 2021 (top right corner); slope (bottom left corner); and erosion risk (bottom right corner).

Figure 2 .
Figure 2. The potential forests in East Kalimantan Province consist of forest areas designated by the government in the state forest and forest-covered non-forest areas in the private land (left corner), that were targeted for forest management and restoration (right corner).

Figure 3 .
Figure 3. Specific site of the management aims within state forests, private forests, and non-forests.

Figure 4 .
Figure 4. Specific site for applying timber harvesting practices within state and private forests.

Figure 5 .
Figure 5. Specific site for applying forest regeneration approaches within state and private forests.

Table 1 .
The rule set for designing forest management objectives at private forests.

Table 2 .
The rule set for formulating timber harvesting practices within the state and private forests.

Table 3 .
The rule set for formulating forest regeneration practices within the state and private forests.

Table 4 .
Multisystem silviculture applied to many forest management objectives.