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Estimate soil carbon stock in mixed deciduous forest at the Sirindhorn International Environmental Park, Thailand.


Forests are important sector to helping reduce global warming. Trees store carbon in the form of wood and biomass components of trees and fallen to the ground, consequently increase carbon stock in soil. Soil carbon sequestration in farmland and forest is one of several approaches used to advantage in reducing the amount of C[O.sub.2] in the atmosphere. Since it is a very effective method for low cost and can be implemented immediately [1], [2]. Plants can accumulate carbon in plant tissue (stem, leaf, root and fruit) by photosynthesis. These organic compounds are biodegradable when plants are falling to the ground or dead. Organic substances such as humus decomposition are still stored in the soil in the form of organic matter. It may remain in the soil for a long time, hundreds or thousands of years [3],[4],[2]. The deforestation is destroying the source of carbon storage. In addition, the wood from deforestation and burning releases C[O.sub.2] into the atmosphere. Thus deforestation to be used without replanting plan causes an imbalance in carbon storage. This research estimate amount of carbon emission as C[O.sub.2] and soil carbon storage in mix deciduous forest in order consider the potential of soil release C[O.sub.2] and soil carbon storage in forest sector.


i. Study area and samplings:

Study area is located in the Sirindhorn International Environmental Park, Phetchaburi province, central part of Thailand. An area of approximately 1,000 acres of lowland forest, it is the natural and planted forests. The soil is Cha-am series and classified as Isohyperthermic Sufic Endoaquepts. Soil samples were collected from the study area every month for the duration of 12 months (November 2008-October 2009). Soil samples were collected at five points within area of 2 * 2 meters. Analyze soil samples for the properties, including moisture by measuring the amount of water to the amount of water contained levels of soil moisture by volume [5]. Soil density analysis by core method [6]. Analysis of soil organic matter by Walkley and Black method [7]. Analysis of the carbon content in the soil by Atomic Absorption Spectrophotometry (AAS).

Air samples were collected using dark static chamber size 30 x 15 x 15 cm (L x W x H) cover down to the ground and sink into the soil with a depth of about 5 cm. Dark static chamber set collection covering an area of about two square meters. Air samples collected in every month of 3 periods, including morning (8:00 to 8:30 am), noon (12:00 to 12:30 pm) and evening (4:00 to 4:30 pm). Air samples were collected using a 20 ml syringe packed into a collection tube, sealed and then store samples and analysis for C[O.sub.2] emission in the laboratory with a GC SHIMADZU GC-8A. This study used data involved, including rainfall, temperature and humidity data from the weather station nearest study site. Biomass collected in the study area by weighing the components of tree branches and leaves that fall on the ground.

ii. Calculate the volume of carbon accumulation:

This study calculate the volume of carbon accumulation in soil using the formula introduced by Milne [8] as follows

SOC stock = SOC content x BD x depth x area Where The SOC stock = carbon content accumulated in soil (t/ha).

SOC content = carbon content in soil (g C/g soil).

BD = soil density (mg/[m.sup.-3]).

Depth = soil depth (m).

Area = land area (mg/[m.sup.-3]).


i. Soil properties:

The soil properties in the study area before investigated experiment (November, 2008) shown in Table 1. Soil texture is silt-clay with poor drainage, less water permeability, and slow runoff of surface water. Organic carbon is 1.62%, organic matter is 2.77%, total nitrogen content is 0.25%, and C/N ratio is 9.55. Soil moisture is 17.05% and soil pH (water) is 8.34.

The soil in the study area during study period (November 2008-October 2009) revealed that soil is silt clay with a pH of 5.34-8.34. Fertility level of the soil in the area is relatively low to high amount of organic matter that is found in the range from 0.26 to 3.67 percent. The moisture content is in the range of 8.06 to 92.41 percent, which is relative high in rainy season (June-October). Organic carbon is in the range of 0.15 to 2.42 percent. Carbon to nitrogen ratio is in the range of 2.28 to 14.02.

ii. Soil carbon loss:

The highest amount of C[O.sub.2] 123.00 gC[O.sub.2]/[m.sup.2]/month released in August 2009 because highest above ground biomass (168.50 g/[m.sup.2]) fall in this month. Biomass was completely biodegradable and then converted to C[O.sub.2], water and minerals. Linear relationship between above ground biomass and C[O.sub.2] was found with [R.sup.2] =0.748. In addition, the pH of the soil is another factor affecting the microbial degradation of compounds. The neutral pH of the soil, resulting in faster degradation of organic matter than acidic pH did. By the proper pH in the range 4.5 to 9.0, which is the decomposition of organic matter is high, then the high C[O.sub.2] emissions (Figure 1). This study also found that the amount of C[O.sub.2] released is correlated with soil moisture and rainfall, which is high moisture from 84.55 to 92.24% was observed during the month of August-September 2009. Lowest emission rate was found in February and March 2008 (70.00 g C[O.sub.2]/[m.sup.2]). Linear relationship between soil moisture and C[O.sub.2] emission was found with [R.sup.2] =0.914. The result showed soil moisture plays importance role on C[O.sub.2] emission.

iii. Soil carbon stock:

Average soil carbon stock for 12 months in study was 0.86 kg/[m.sup.2]. The highest amount of soil carbon stock (2.12 kgC/[m.sup.2]/month) was observed in September 2009 and we found high amount of soil carbon stock in rainy season (July-September) (Figure 2). Although C[O.sub.2] emissions were high during the rainy season, but the accumulation of soil carbon stock was also high due to high amount of plant debris falling in the study area on this duration. Less soil carbon stock was found in dry season (March-June) due to low amount of plant debris and low soil moisture, this condition is not suitable for humus decomposition in soil. Correlation between soil organic matter and soil carbon stock presented in linear form with [R.sup.2] =0.957, while linear relationship between soil organic carbon soil carbon stock was also found with [R.sup.2] =1. Soil moisture and soil carbon stock shown positive relationship in linear form with [R.sup.2] = 0.654. In addition, the result shown that total nitrogen is one of influence factor on soil carbon stock. The linear relationship between total nitrogen content in soil and soil carbon stock was found with [R.sup.2] = 0.618.


The experiments investigated to estimate carbon stock and loss from forest soils in natural forest (mixed deciduous forest) at the Sirindhorn International Environmental Park, Phetchaburi province in Thailand concluded that natural forest has the potential to store carbon. Amount of carbon stored in the soil was 0.86 kg/[m.sup.2]. Amount of soil carbon storage in natural forest in this study depends on soil organic matter, soil organic carbon, soil moisture content, and total nitrogen in soil. Average carbon emission from the soil as C[O.sub.2] in the study area was 123.00 g C[O.sub.2]/[m.sup.2], which was control by above ground biomass and moisture content in soil.


Article history:

Received 3 October 2015

Accepted 10 October 2015

Published Online 13 November 2015


We extend great thanks to the Sirindhorn International Environmental Park, Phetchaburi province, Thailand for allows us to investigated experiment and all facilitate. Thank you to the laboratory of soil and plant analysis, faculty of Agriculture Kamphaeng Saen, Kasetsart University Kamphaeng Saen Campus, Nakhon Pathom province, Thailand for soil and air samples analysis.


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[2] Lal, R., 2005. Forest soils and carbon sequestration. Forest Ecology and Management, 220: 242-258.

[3] Campbell, C.A., 1967. The applicability of the carbon-dating method in soil humus studies. Soil Sci., 104: 217-224.

[4] Post, W.M. and K.C. Kwon, 2006. Soil carbon sequestration and land-use change: processes and potential. Global Change Biol., 6: 317-327.

[5] Topp, G.C., 1993. Soil Water Content. In M.R. Carter., ed., Soil Sampling and Methods of Analysis. Part 3. Canadian Society of Soil Science. Lewis Publishers, 541-557.

[6] Blake, G.R. and K.H. Hartge, 1986. Bulk Density. Methods of Soil Analysis, Part 1, Soil Sci. Soc. Am, 363376.

[7] Walkley, A., I.A. Black, 1934. An examination of Degtjareff method for determining soil organic matter and a proposed modification of the chronic acid titration method. Soil Sci., 37: 29-38.

[8] Milne, E., 2012. Soil organic carbon. Encyclopedia of earth, Available Source: http://www. eoearh. org/article/soil_organic_carbon.

(1) Kruamas Smakgahn, (1) Amornrat Seangthong and (2) Suphachai Amkha

(1) Faculty of Liberal Arts and Science, Kasetsart University Kamphaeng Saen Campus, Kamphaeng Saen district, Nakhon Pathom province, 73140, THAILAND

(2) Faculty of Agriculture at Kamphaeng Saen, Kasetsart University Kamphaeng Saen Campus, Kamphaeng Saen district, Nakhon Pathom province, 73140, THAILAND

Corresponding Author: Kruamas Smakgahn. Faculty of Liberal Arts and Science, Kasetsart University Kamphaeng Saen Campus, Kamphaeng Saen district, Nakhon Pathom province, 73140, THAILAND.

Table 1: Soil properties, C[O.sub.2] emission, and soil
carbon stock during study period.

Soil properties        Nov. 08   Dec. 09   Jan. 09

Texture                         Silt-Clay

Organic carbon (%)      1.62      1.35      0.15

Organic matter (%)      2.77      2.32      0.26

Total Nitrogen          0.25      0.13      0.06
content (%)

Moisture (%)            30.8      17.13     8.57

pH                      8.34      8.39      6.13

C:N ratio               9.55      10.39     3.15

Above ground            107.0     75.00     71.00

C[O.sub.2] emission     40.8      32.53     22.76

Carbon stock            1.42      1.18      0.13

Soil properties        Feb. 09   Mar. 09   Apr. 09

Texture                         Silt-Clay

Organic carbon (%)      0.66      0.16      0.43

Organic matter (%)      1.13      0.27      0.64

Total Nitrogen          0.05      0.07      0.05
content (%)

Moisture (%)            8.06      8.68      19.31

pH                      6.05      6.14      5.37

C:N ratio               14.02     2.46      10.94

Above ground            70.00     70.00     74.00

C[O.sub.2] emission     14.01     12.58     30.02

Carbon stock            0.58      0.14      0.38
Soil properties        May 09    Jun. 09   Jul. 09

Texture                         Silt-Clay

Organic carbon (%)      0.36      0.33      1.89

Organic matter (%)      0.62      0.56      2.49

Total Nitrogen          0.04      0.04      0.48
content (%)

Moisture (%)            49.73     63.58     70.72

pH                      5.30      5.30      5.82

C:N ratio               8.47      7.96      4.45

Above ground           110.00    151.00    160.00

C[O.sub.2] emission     50.95    117.61      119

Carbon stock            0.32      0.29      1.66

Soil properties        Aug. 09   Sep. 09   Oct. 09

Texture                         Silt-Clay

Organic carbon (%)      2.13      2.42      0.25

Organic matter (%)      3.63      3.67      1.05

Total Nitrogen          0.95      0.72      0.19
content (%)

Moisture (%)            84.55     92.41     55.31

pH                      6.00      5.31      5.34

C:N ratio               2.28      3.69      1.87

Above ground           168.50    154.00    130.75

C[O.sub.2] emission      123       122       102

Carbon stock            1.87      2.12      0.22
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Article Details
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Author:Smakgahn, Kruamas; Seangthong, Amornrat; Amkha, Suphachai
Publication:Advances in Environmental Biology
Article Type:Report
Geographic Code:9THAI
Date:Oct 1, 2015
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