IOP Conference Series: Earth and Environmental Science

I n te r n a ti o n a l C o n f e r e n ce o f B i o -B a se d E c o no m y f o r A p p l i ca t i o n a n d U t i li z a ti o n b i t . l y/ i c b e a u 2 0 2 0 2 n d I C B E A U 2 0 2 0 A s si s t a n t

section_content: Confere nc e Se ri es ( htt ps:// i opsci ence. i op. org/ journal/ 1755 -1315 ) submi tt ing proce ss. For your i nforma ti on, t he tim e of publ ic at i on a nd ot he r pol ici e s a re det e rm i ne d by t he publi she r of t he IOP j ournal. 

Si nce re ly, Ma nagi ng E dit or Ba stia n Nova, M. Si. 

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section_name: Letter of Acceptance

section_content: Assalamu'alaikum wr. wb, Good morning to all of you. Dear respected keynote speakers Members of the organizing committee Dear participants and observers Distinguished guests, respected colleagues, ladies, and gentlemen

We are very happy to welcome all participants of the International Conference on Bio-Based Economy for Application and Utilization (ICBEAU-2020). This conference has a very strategic position in responding the global development. 

Need on an agricultural product is not dominated currently in food aspect, but is becoming more broadly to the new aspect beyond the food. Fossil based energy currently contributed to many pollution issues in the whole of the world, beside its existence which is more scarce in the future. Drug development, based on synthetic chemicals and materials is believed and regarded plays a significant role in the occurring of new health problem and disease. For that reason, a shifting in medical treatment back to nature is becoming a trend nowadays. Thus, this ICBEAU-2020, should have a very significant impact on the above-mentioned issues.
section_name: Welcome Address by The Head of LPPM in Andalas University

section_content: As the Head of LPPM in Andalas University, I personally very support to this event. We thanks to all parties supporting and contributing to implementing this International Conference. 

Especially I would like to thank for all keynote speakers who responded positively our request to share their insight, experience, and expertise in this conference. 

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section_name: Respected Ladies and Gentlemen

section_name: Rundown of Event

section_content: Indonesia has the largest peatland in the world with an area of 14. 91 million ha [1] or 47% of the total peatland's area in the world [2]. This land can be found in Sumatra, Kalimantan, and Papua [1, 3, 4, 5]. 

On the west coast of Sumatra, the largest distribution of peatlands can be found in Pesisir Selatan, Sumatra Barat, with an area of 95,000 ha [4] which is spread over various land-use types. 

The use of peatlands for agriculture and plantations in Indonesia has been initiated since the 1970s and has developed rapidly from 1990 until now after published the Presidential Decree No. 32 of 1990 about the Management of Protected Areas. Calculating the carbon stock of peat is needed in assessing the importance of soil in the carbon cycle [6], estimate the potential for greenhouse emissions [7], and as a basis for making policies for sustainable peatland management. 

In Indonesia, several studies examining the carbon stock of peatlands had been conducted with various approaches [8, 9, 10, 11]. The results of the research indicated that the value of soil carbon stock in different land uses is varied [11, 12]. Also, there is no information about the carbon stock in Pesisir Selatan under several classes of peatland-uses and depths. 

One of the requirements in calculating soil carbon stock in the area is the availability of a peatland map and its thickness. However, the peatland mapping data provided in Indonesia is currently still at a reconnaissance scale of 1: 250,000 [1]. Hence, the information does not accurate as a basis for calculating carbon stock. Based on this problem, this study aimed to: a] map the peatland in Pesisir Selatan, b] calculate the soil carbon stock on various peatland-use and peat thickness, and c] identify the relationship of soil characteristics to the soil carbon content.
section_name: Introduction

section_name: Research Method

section_content: This research was conducted in the peatland ofPesisir Selatan Regency, Sumatra Barat. The peatlands formed above the alluvium substratum, [13]. We used satellite imagery data [Landsat 8 OLI level 1, 2020] to produce a land-use map by using ArcGIS® 10. 8. Bands 1-7 of the satellite imagery were composited for interpretation. The sharpening of the image resolution was enhanced by using band 8. Since the peatlands in Pesisir Selatan were distributed on 2 image data sheets, the numeric null value for each image was omitted. Subsequently, both image sheets were processed to mosaics. The satellite imagery data was analyzed using a supervised method. Visual interpretation of plant vegetation used a 6-5-4 band [Figure 1 ]. The appearances of natural color by using a 4-3-2 band. Training sample manager processes [25 samples] were conducted for each land use.
section_name: Setting of the research and processing the satellite imagery data

section_content: Soil sample points were determined based on land use, soil map, and peat thickness data [14, 15], Geological map sheets [13], and contour data from SRTM images used for estimating peat thickness and for distinguishing the peat topography, hills, and plains. Each of these data was overlaid to generate the polygons containing information of peat thickness with certain land uses. This technique was chosen to minimize the number of samples but still produce accurate data. Based on the analysis, 509 polygons with 30 diversity of peatland units were collected[Figure 1 ]. Soil observations were conducted in each land unit. Guidelines for soil observation and soil sampling were adopted from Schoeneberger, et al [16].
section_name: Soil Sampling

section_content: Soil analysis laboratory consisted of bulk density [BD], water content [17], total carbon, and ash/mineral content byLOI [Loss of Ignition] method [18, 19]. Calculation of peatland carbon stock per area was adopted from Robertsonet al [20]. Determination of the amount of carbon content for each land use with a certain depth was adopted from Gorham [21].
section_name: Data Analysis

section_name: Results and Discussion

section_content: Based on our results, the total area of peatlands in Pesisir Selatan is 78,998. 74 ha. The total land area is smaller than Puslittanak [14], namely 86,567. 83 ha and mostly similar with Degraded Peatland Mapping data [15] with an area of 79,538. 88 ha. The difference is caused by several land units [Figure 1, left] that do not have a minimum peat layer of 40 cm and do not fulfill other Histosols soil classification criteria based on Soil Survey Staff 2014 [22]. These land units are located in Limau Manih Nagari Lakitan Timur, Lakitan Utara, and Kambang Barat with an area of 1,909. 8 ha. 

We include some additional peatland units with an estimated area of 1,518. 89 ha [Figure 2 ] located in Tarok Nagari Lakitan Selatan, Padang Laban, and the Sungai Liku, which extend from 1 º 43'4. 1"S, 100 º 45'0. 5"E to 1 º 43'4. 1"S, 100 º 48'15"E and 1 º 46'7. 4"S, 100 º 45'0. 5"Eto 1 º 46'7. 4"S, 100 º 48'15"E. The area has a thickness of peat layer varying from 40 to 500 cm, BD 0. 11-0. 32 g. cm -3, Total Carbon 50. 3% and fulfills the criteria of the histic epipedon [22]. 2 ] which are cultivated on peat with a thickness of 0-300 cm, such as food crops and several palawija [secondary plants]. An open field that is not cultivated, so it is dominated by high vegetations with a height average of 1-3 m. 3 Oil Palm Plantation [GPs] All oil palm plantations were possessed by both farmers and agriculture companies. 4 Annual crops [GLp] Paddy fields, corns, and other food crops. This land also covers other seasonal plants cultivated on peatlands. Generally, the land is cultivated with semi-intensive to intensive management. 5 Bare Land [GT] This land has 0-20% vegetation covers. 

The plantation sector has improved the local farmers' economy. However, the utilization of forests as conservation areas on peatlands also needs to maintain, especially forest areas with a thickness of> 300 cm. Based on Table 2, the area of GH in peatlands is around 8,743. 53 ha or 11. 06%. Hence, 6. 2% of them with > 600 cm thickness are found in forest land. It means that the distribution of peat thickness is critical to maintaining the function of forests with a thickness of> 300 cm.
section_name: Distribution of peatlands

section_content: Table 2 shows the total carbon stock reaches 244 million tons with an average value of 3,090. 89 C per ha. The sequence of carbon stock follows GPs> GS> GH> GT> GLp. The soil carbon stock storageatGPs reaches 49% out of the total carbon stock in the peatland and only 0. 07% was found in GLp with an area of178 thousand tons. In this case, the high carbon stock in GPs land use is dominantly related to the large such area [r 2 = 0. 755, Figure 4 ]. The average value of carbon stock in Pesisir Selatan is 3,090. 89 tonnes C. ha -1. This value is relatively higher than other studies, such as research of [23] around 250 ton C. ha -1. This is due to the influence of the peat thickness, where peatland with a thickness of > 600 cm reaches 11. 9%, and a thickness of 300-600 cm is 37% of the total area. However, this average value is consistent with the results of the research by [24] in the Irish Wicklow peatlands with values of 530 -3303 tonnes C. ha -1 at depths of 100-650 cm. For the same land area and peat thickness, the value of carbon stock depends on peat characteristics: total carbon and soil bulk density [25, 26]. Based on the land use, the sequence of mean carbon stock is GH> GS> GT> GPs> GLp due to the difference of the peat thickness [24, 27].
section_name: Soil carbon stock of the peatland based on the classes of land use and peat thickness

section_content: The average percentage of total carbon among land uses [Figure 5 ] shows that the highest total carbon is found in land use GH 20-40 cm at 61. 6%. The value tends to be higher in the subsurface layer20-40 cm, compared to the surface layer [0-20 cm]. This dynamic is in line with [28] indicating the ash [mineral content] in the soil surface layer is higher than the subsurface layer. Since the peat material in the surface layer would be easily decomposed due to aerobic conditions leaving mineral content in the layer. Figure 5 shows that BD tends to be lower in the subsurface than in the surface layer. This pattern is contrary to mineral soils that tend to be higher in the subsurface layer. In mineral soils, BD generally is determined by soil texture and organic matter [29, 30]. However, in the peatland, the soil texture is not acceptable. The determining factor of BD in the peatland is organic carbon content[Figure 6 ]. It is also shown in Figure 5 that total carbon is higher in the subsurface layer. 

Figure 5 also presents that most agricultural areas have a higher BD. It is caused by the peat soil is mixed with mineral material. The mixing is due to the shallow peat thickness. Intensive agricultural activity before planting causes the mixing of peat material with mineral soil so that the BD will be getting higher [Figure 5 ]. Figure 6 shows that the higher the BD, the lower the total carbon content. Soil with higher BD indicates that the most of soil volume is filled with mineral-dense material. Due to the decomposition, the peat experiences a reduction in volume. It affects on decreasing of total C content. Figure 7 shows the relationship between total carbon and soil water content [r 2 = 0. 2434]. If water content increases, so does the total carbon; since when the soil is saturated with water, the environmental condition becomes anaerobic. This condition will reduce the rate of oxidation and microbial activities. If this condition occurs continuously, the dead organic matter will accumulate and the peat layer will become thick so that the soil carbon increased.
section_name: Characteristics of peatlands in Pesisir Selatan

section_content: The total area of peatlands inPesisir Selatan is 78,998. 74 ha. The total amount of peat carbon stock is 244 million tonnes, while the land-use-related sequence follows GPs> GS>GH> GT> GLp. The average value of carbon stock is 3thousandtonnesC. ha -, with the sequence GH> GS> GT> GPs> GLp. The difference in the average value of carbon stock per ha is influenced by the differences in peat thickness. However, the dynamics of total soil carbon indicate the increase in the carbon content increases with soil depth. The relationship between soil carbon content and water content is linear and inversely proportional to BD.
section_name: Conclusion

section_name: Acknowledgment

section_content: This research was supported by the Faculty of Agriculture, Universitas Andalas [ 01 /PL/SPK/PNP/FAPERTA-Unand/2020 ]. The authors thank Debi Pangestu and Fransisco Adi Farma for the field survey in Pesisir Selatan
section_name: Acknowledgment

section_name: Conflict of Interest

section_content: No potential conflict of interest was reported by the authors.
section_name: Conflict of Interest