Analysis of Spatial distribution of Peatland Depth in Keub Village

Peat is an ecosystem that is formed due to biomass production that exceeds the decomposition process. The area of peat land in Aceh Province reaches 338,164 ha. Improper use of peatlands results in peatland degradation so that the thickness and depth of the peat soil decreases. This research aims to determine the map of changes in the distribution of peat depth classes and determine changes in the peat ecosystem classification map in Keub Village by comparing the peat depth map published by the Ministry of Environment and Forestry in 2019 with interpolation results using the inverse distance weight method. The results of this research showed that there was a change in the peat depth class and the area of distribution of the peat depth class between the peat depth class map published by the Ministry of Environment and Forestry and the interpolation results in Keub Village. Based on a comparison of the KLHK peat depth map with the interpolated map, it was also found that there was a change in the area of protected functional areas in the form of an increase in the number of areas.


Introduction
Definition of peat according to [1] concerning the Protection and Management of Peat Ecosystems, defines peat as organic material that is formed naturally from incompletely decomposed plant remains that accumulate in swamps.According to the statement of [2] the area of peat land in Indonesia is currently around 14.9 million ha.This number is spread across almost all provinces in Indonesia.According to the statement [3] about determining the function of the national peat ecosystem, the area of peat land in Aceh Province is 338,164 ha, which is 3.52% of the total area of peat land in Indonesia.According to the statement [4] based on their function, peatlands are divided into two, namely the protection function and the cultivation function.However, these two functions are often misused by the community in utilizing peatlands.The preservation of the function of peatland ecosystems continues to be a global concern, especially in relation to nutrient depletion, release of greenhouse gases into the atmosphere, land conversion, illegal logging and high land fires.This has an impact on the increasing extent of peatland being damaged due to degradation activities.Clearing peatlands by burning causes a decrease in the soil's ability to store water, namely its hydrological (water management) function.Apart from that, the consequences that will arise will have an impact on changing the characteristics of the natural peat soil.Clearing peatlands by constructing drainage channels can cause the groundwater level to decrease, so that the top layer of peat soil changes to an aerobic condition and reduces the thickness of the peat soil layer.These changes in conditions can increase the activity of microorganisms involved in the peat soil decomposition process [5].Until 2009, 10.77 million ha or 51% of Indonesia's peatland area had experienced deforestation and 2 million ha had been damaged during the period 2000 to 2009.1297 (2024) 012092 IOP Publishing doi:10.1088/1755-1315/1297/1/012092 2 [6].As a result of changes in peatlands, such as changes in peatland characteristics and a decrease in peat depth, it is necessary to update data such as peat depth distribution data.
Based on decree No. SK.938/Menlhk/Setjen/PKL.1/10 of 2019, the Ministry of Environment and Forestry published a peat depth map in West Aceh Regency.One of the villages that has peat land in West Aceh Regency is Keub Village which is utilized by the community.However, the result of inappropriate land use resulted in the degradation of the peatlands in the village.Along with the degradation of the peatlands in the village, the thickness of the peat soils has decreased.Therefore, it is necessary to verify and update the latest peat depth map as guidance data for the sustainable use and management of peatlands in Keub Village, West Aceh Regency.So this research needs to be carried out with the aim of knowing the map of changes in the distribution of peat depth classes in Keub Village and knowing changes in the peat ecosystem classification map in Keub Village.

Tools
The tools used in this research were a peat drill, measuring tape, global positioning system (GPS), computer/laptop (personal computer) and its accessories, ArcGIS, Microsoft Word and Microsoft Excel applications, Avenza maps, camera and writing tools.

Data collection
In this research, the data used is divided into two, namely primary data and secondary data.The primary data in this research is in the form of peat depth data at each observation point in the field or what is called GCP (ground control point) data.GCP data is data that is available in point form.Secondary data used in this research is SHP peat depth map by KLHK SK No. SK.938/Menlhk/Setjen/PKL.1/10 of 2019, SHP village boundary maps, and related literature studies that can strengthen this research.

Research procedure
The research flow is presented in Figure 1 below:   [4] procedures for Inventorying and Determining Peat Ecosystem Functions, it is stated that to obtain data on the characteristics of peat ecosystems through field surveys, you can use the systematic grid method.This method consists of longitudinal and transverse transect lines.The distance between observation points is 200 x 200 meters, the distance between longitudinal transects is 1 km, while the distance between transverse transects is 1 km.The transect route is made in the same direction as the river.
After making the grid of points, the percentage of the number of sampling points that will be used to collect peat depth data in the field is determined using a soil drill.According to the statement of [4] procedures for inventorying and determining the function of peat ecosystems, the minimum number of sampling points taken for peat ecosystem surveys is 10% of the total points.Based on the results of creating a systematic point grid, a total of 105 points were found.The number of points in Keub Village is 105 points.Determination of sampling points is carried out using a purposive sampling method which determines the percentage of sampling points taken per depth class using the following formula: The percentage value per depth class is determined using the following formula: So the number of sampling points for collecting peat depth data in Keub Village was determined, namely 34 points.In some depth classes, points are added so that there is comparative data.Determining the points taken uses the random sampling method.This method is used to make it easier for researchers to adapt to field conditions when conducting ground check point surveys in the peat depth field.Below in Table 1, the percentage distribution of sampling points in the two research villages is presented: The following is a working map of the peat depth field survey in Sumber Bakti Village and Keub Village in Figure 1.

Field survey
Peat depth data collection in the field was carried out using a peat drill.The division of peat depth classes is carried out at depth class intervals per 50 cm, starting from the depth point of 0 cm to the deepest depth where the mineral soil layer is found.After the discovery of the underground peat mineral layer, its depth was calculated using a meter and documentation was carried out.The point where peat depth samples are taken is carried out using a GPS (Global Positioning System) tool.
According to the statement of [4] about technical Guidelines for Processing Spatial Data on Peat Ecosystem Characteristics, the function of the peat ecosystem is divided into two, namely as follows: a. Peat Ecosystem Cultivation Function, is peat soil with a thickness of less than 3 meters.b.The Protective Function of Peat Ecosystems is peat soil with a thickness of more than 3 meters.

Data analysis
Data analysis used in this research is by interpolating the inverse distance weight (IDW) method.The IDW analysis method was chosen because this method has a high percentage of accuracy.According to research conducted by [7] The equation used in the inverse distance weight (IDW) method is as follows: With ‫݅ݖ‬ (i = 1,2,3, ... N) is the height value of the data that you want to interpolate for a number of N points, and the weight ‫݅ݓ‬ is formulated as follows: p is a positive value that can be changed called the power parameter (usually the value 2) and ℎ݆ is the distance from the point distribution to the interpolation point which is described as: After data analysis was carried out using the IDW interpolation method, a comparison was made of the Keub Village peat depth map published by the Ministry of Environment and Forestry SK No. SK.938/Menlhk/Setjen/PKL.1/10 of 2019 with maps interpolated in this research.Comparisons were made to determine changes in the distribution of peat depth classes and peatland classification in Keub Village.

Comparison of peat depth classes
Based on the results of interpolation of peat depth survey data in Keub Village using the IDW interpolation method, it was found that there was a change in the peat depth class.This is presented in the figure 3 a comparison map of peat depth class distribution in Keub Village.

Figure 3. Comparison of peat depth class maps in Keub Village
Based on Figure 2. the map of the distribution of peat depth classes by the Ministry of Environment and Forestry above, it can be seen that the dominant peat depth class is in the 250-300 cm class.This class has an area spread over almost half of the area of Keub Village.In the other class, namely the 0-50 cm class, it can be seen stretching lengthwise across Keub Village.In the depth class 350-400 it looks small, as does the area of the depth class 400-450 cm.In the 400-450 cm class, it can be seen that this class has the smallest area compared to the other depth classes.The distribution of peat depth classes has changed when compared with the research results of the peat depth class distribution map.
In Figure 2, the classification map of the research results above shows that changes occurred in all peat depth classes.The striking change is in the area of the 250-300 cm depth class.This class looks smaller compared to the map published by the Ministry of Environment and Forestry.Another class that experienced striking changes was the 300-350 class.In this class, when compared with the area of the peat depth class published by the Ministry of Environment and Forestry, there has been a very large increase in area.In the depth class 0-50, changes are seen, namely becoming smaller and divided into two points.Based on the research results, it is that in each class there is a change in the area of the peatland depth class.In some classes of peat depth there was an increase in the distribution area and there were also areas where the distribution area decreased.In the peat depth class of 0-50 cm, there was a decrease in area, namely on the KLHK map the area was 100 ha to 55 ha in the research results.However, in some classes there was an increase in distribution area, such as in the 300-350 cm class on the map according to the Ministry of Environment and Forestry, the distribution area was only 45 ha, then increased to 133 ha based on research results.
The distribution of peat depth classes on the two peat depth maps is different due to different years of research.The two maps are also thought to have different methods, resulting in a wide distribution of different peat depth classes.Research on peat depth should be carried out every 5-10 years.This is in accordance with the statement [2] that data on peatlands is very dynamic and therefore needs to be updated regularly every 5-10 years.
Changes in the distribution of peat depth classes in Keub Village look varied.In some classes the area has decreased, but also in some classes the area has increased.These changes are caused by several factors such as the level of peat maturity.According to the statement [8] states that the more mature the peat, the denser the peat and the shallower the depth of the peat.Apart from the maturity level, the drainage rate also causes a decrease in the depth of the peatland.Utilization of peatlands must still pay attention to certain aspects that can cause peatlands to decrease in depth.Burning peatlands and improper infrastructure development such as building drainage channels around peatlands that are not according to planning can disrupt the infiltration process in peatlands, causing the surface of the peat to subside.[9].
Changes in the addition of depth classes and the wide distribution of peat depth classes prove that the dynamic nature of peat soils.The difference in peat depth class between the two maps occurred due to the difference in scale between the two maps when the study was carried out.On the KLHK map, a map is published at a scale of 1:50.000, while in the research map a village mapping scale is used at a scale of 1:5.000.The use of different scales makes the peat depth point shift.The increase in the distribution of deep peat depth classes in Keub Village indicates that the peatlands in Keub Village have the original characteristics of peatlands, namely increasing depth.
The increase in depth area in the deep peat depth class is proven by the existing conditions in that depth class which are still classified as natural.In field conditions, the depth class of deep peat is dominated by shrubs, namely ferns.There is no utilization of this peat depth class which has resulted in an increase in the area of deep peat.In Figure 4, a photo of the existing condition of the deep peat depth class is presented.Based on the results, it is known that the area of cultivation functions on the KLHK peat depth map has decreased according to the research results.On the KLHK map the area of cultivation functions is 368 ha and according to research results it is 248 ha.The total area reduction that occurred was 120 ha.In the protection function, based on a comparison of the KLHK peat depth map with the research results map, it is known that there has been an increase in area, namely 79 ha.The extent of the protected function area on the Keub Village peatlands indicates that the peatlands are classified as deep peatlands.In more detail, the differences in peat depth classification between the two maps are presented in the table: Although the protected function of Keub Village has increased in area.The extent of this protective function indicates that the peatlands in Keub Village must be utilized appropriately.One activity that can cause a decrease in peat depth is improper drainage in peatlands.This is in accordance with the statement [10] states that improper drainage canal construction will have long-term negative impacts and affect various characteristics of peat soil physically, chemically and biologically.Selection of inappropriate plants can also cause subsidence in peatlands.This can also have an impact on plant fertility.The choice of agricultural commodities according to the depth of the peatland also needs to be considered.Peatlands with a depth of <100 cm are recommended for food and horticultural crops, while peatlands with a depth of 2-3 m are recommended for planting annual crops.[11].
The use of protected areas on peatlands, apart from being unsuitable for planting, also poses a high risk of land fires on peatlands.Deep peatlands have very high carbon reserves stored in the soil.The depth of the peat is the main indicator in determining the high carbon stores in peat soil.This is in accordance with the statement [12], of the deeper the peat soil, the greater the carbon reserves in it.The higher the carbon reserves in peat soil, the higher the risk of fires.Fires on peatlands occur due to the dryness of the peat soil, making it very easy to catch fire.Excessive canal construction in peatlands can cause the peat soil to dry out quickly.Canals are made in peatlands so that planting can be done in peatlands.

Figure 2 .
Figure 2. Map of peat depth survey work in Keub Village

Figure 4 .
Figure 4. Existing condition of Keub Village peatlands 3.2.Peat Depth Classification Changes in peat depth classification occur due to changes in depth classes.The classification of peat depth ecosystems is divided into two ecosystem functions, namely cultivation function and protection function.The classification of these two functions is carried out based on the peat depth class grouping presented in Figure 5.

of peat depth survey work in Keub Village, West Aceh Regency Map
) (x,y) are the coordinates of the interpolation point and ‫݅ݔ(‬ , ‫݅ݕ‬ ) are the coordinates for each point distribution.
source: 1. KLHK peat depth map 2. RBI Map of West Aceh Regency, Geospatial Information Agency

Table 2 .
Wide distribution of peat depth classes in Keub VillageNo.

Map of the distribution of peat depth classes in Keub Village, West Aceh Regency Map
source: 1. KLHK peat depth map SK No. SK.938/Menlhk/Setjen/PKL.1/10/2019 2. Results of peat depth interpolation using the IDW method.3. RBI map of West Aceh district, Geospatial Information Agency

Table 3 .
Classification of peat depth ecosystem functions in Keub Village