IJERD – International Journal of Environmental and Rural Development (2015) 6-1

Research article
erd

Plant Diversity on Slightly Saline Soils in Chi River Basin ofNortheast Thailand
SARAWUT DEEPROM
Faculty of Agriculture, Khon Kaen University, Khon Kaen, Thailand

VIDHAYA TRELO-GES*
Faculty of Agriculture, Khon Kaen University, Khon Kaen, Thailand
E-mai : vidtre@kku.ac.th

BUBPHA TOPARK-NGARM
Faculty of Agriculture, Khon Kaen University, Khon Kaen, Thailand

SAMANG HOMCHUEN
Faculty of Agriculture, Khon Kaen University, Khon Kaen, Thailand

TONGIN KUMMEE
Faculty of Science, Khon Kaen University, Khon Kaen, Thailand
Received 15 December 2014

Accepted 1 April 2015(*Corresponding Author)

Abstract This research is aimed to documenting the diversity of plant species that arefound on slightly saline soils in the Chi river basin of Northeast Thailand. Both in the dry
and the rainy seasons of 2013, plant surveys were conducted at selected sites in threeprovinces (Chaiyaphum, Khon Kaen, and Kalasin) by using a quadrat sampling technique.
Soils under the dominant plant species were collected for physical and chemical analyses.
From the study, a total of 155 plant species belonging to the 72 families were recorded.
Five of those were classified as halophytes, and included Azima sarmentosa, Maytenus
diversifolia, Synostema bacciformis, Pluchea indica and Gisekia pharnaceoides. Thedominant species in the selected sites of three provinces were Cynodon dactylon,
Heliotropium indicum, Melochia corchorifolia, Ageratum conyzoides, Coldenia procumben,
Glinus oppositifolius and Panicum repens, respectively. In the dry season, the average soil
electrical conductivity under the dominant plant species at Chaiyaphum, Khon Kaen andKalasin provinces were 2.52, 0.7 and 0.54 dS/m, respectively. In the rainy season, theaveraged soil electrical conductivity under the dominant plant species were decreased to0.61, 0.37 and 0.14 dS/m in Chaiyaphum, Khon Kaen and Kalasin provinces, respectively.
In all studied areas during in both seasons, the amounts of exchangeable sodium were in thesame direction as the values of electrical conductivity. Soil pH values at all studied areas inboth seasons were in an acidic condition. However, the pH values were lower in the dry
season than in the rainy season. Soil moisture under the dominant plant species was higher
in the rainy season than that in the dry season.
Keywords plant diversity, saline soil, halophytes

INTRODUCTION
The northeast region of Thailand, known as Isan, covers an area of 170,226 sq. km or one third of
the entire country. The region situates on Korat plateau which is distinctly raised from the Central
region. The plateau tilts downward from the Phetchabun mountain range in the west of the region
towards to Mekong River. The plateau consists of two plains: the southern Khorat plain, which isdrained by the Mun and Chi rivers, and the northern Sakon Nakhon plain which is drained by theLoei and Songkhram rivers. The two plains are separated by the Phu Phan mountain range. The soil
is mostly sandy, with substantial salt deposits. Soils in Northeast Thailand are salt-affected due toⒸ ISERD40

IJERD – International Journal of Environmental and Rural Development (2015) 6-1

salt bearing rocks (Department of Land Development, 1991), particularly in Nakhon Ratchasima,Khon Kaen, Roi Et, Chaiyaphum and Mahasarakham provinces (Department of Mineral Resources,1982). Saline soils currently occupy an area of approximately 17% of the region and that area isincreasing annually. A rather large part of the arable land in this region is salt-affected to varying
degrees. Generally, narrow areas, which are strongly salt-affected, are scattered from the western
hilly areas to the undulating regions, and the relatively weakly salt-affected wide areas are spreadthroughout the low-lying flat regions, especially along the big rivers. The degree of soil salinity inthe salt affected areas can be classified into three categories: 1) Severe salt affected soil is the areawhich more than 50% of the soil exhibits surface salt patches. Soil salinity ranges from high to veryhigh. This area known as deteriorated land, covers about 0.2 million hectares and cannot be used
for any agricultural activity. 2) Moderate salt affected soil is the area which 10-50% of the soil
surface is covered with salt patches. The area is about 0.6 million hectares and the land is used as
rice paddies, but the yield is very low. 3). Slightly salt affected soil is the area which salt patches on
the soil surface occur in less than 10% of the area. There are about 2 million hectares, and most of
the area is comprised of rice fields with low yields (Arunin, 1984) (Fig. 1). Soil salinity has become
one of the major determinants of crop productivity in the Northeast Thailand and has an adverse
impact on the physical, chemical and biological properties of soil, as well as on plant growth andyield (Marschner, 1995). To grow crops successfully, these soils must be improved. Investigations
carried out at various research locations in the world have shown that salt-affected soils can be
improved by the planting of salt tolerant plant species. In an effort to identify and dominant the salt
tolerant plant species present on naturally occurring saline soils, it is therefore, necessary to study
the soil properties and vegetation cover that are found on saline soil. The gains from this study will
be valuable, and the dominant species, that have been observed, will deserve further attention as
potential candidates for restoring the salt affected areas. In addition, the presence or absence ofcertain plants can give valuable clues to indicate the degree of soil salinity.

a)

b)

c)

Fig. 1 Categories of salt affected areas: a) severe, b) moderate and c) slightly
METHODOLOGYThis study has aimed to documenting the diversity of plant species and investigating the soil
properties under the dominant species on slightly saline soils in the Chi river basin of Northeast,Thailand. Plant surveys were conducted on 9 selected sites in 3 provinces (Chaiyaphum,Khon Kaen and Kalasin) during both the dry season (April) and the rainy season (October) of 2013by using a quadrat sampling technique (Fig. 2). Plant specimens were collected and identified fromwithin 108 sample plots (1x1 m). The dominant species were analyzed by totally averaging each of
the plant covers.
To study soil properties, soil samples under each of the dominant species found in the study
area were collected separately at the depth of 0-15 cm and were brought back to the laboratory forphysical and chemical analyses in both the dry season and the rainy season. The moist soil samples
were analyzed for the moisture content, pH (1:2.5 soil: water), ECe (saturation extract), organic
matter and exchangeable Na+. A good indicator of potential salinity problems is the depth andquality of the groundwater table. If groundwater table are both saline and shallow or rising, there is
the potential for salinity problems to occur in the future (Kohyama et al., 1993). Therefore, in thisⒸ ISERD

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IJERD – International Journal of Environmental and Rural Development (2015) 6-1

study, the depth of water table has been measured in the middle of both the rainy and dry seasonsby using a piezometer. In addition, water samples were collected to determine the salinity in orderto determine the quality of the groundwater.

Fig. 2 The study area in 3 provinces (Chaiyaphum, Khon Kaen, and Kalasin) of Northeastern
ThailandRESULTS AND DISCUSSION
For soil properties on slightly saline soil in the dry season, the average soil electrical conductivity
under the dominant plant species at Chaiyaphum, Khon Kaen and Kalasin were 2.52, 0.7 and 0.54
dS/m, respectively. In the rainy season, the average soil electrical conductivity under the dominant
plant species decreased to 0.61, 0.37 and 0.14 dS/m in Chaiyaphum, Khon Kaen and Kalasin,respectively. The amounts of exchangeable sodium were in the same direction at electricalconductivity values for all areas studied in both seasons. Soil pH at all studied areas in both seasons
were in an acidic condition. However, soil pH values were lower in the dry season as compared tothe rainy season as found by Topark-ngarm (1990). Soil moisture under the dominant plant species
was higher in the rainy season than in the dry season (Table 1).
Table 1 Soil properties in the dry season and the rainy season in the study areas (Mean±SD)
Soil properties
pH (1: 2.5 H2O)
ECe (dS/m)
OM (%)+Exchangeable Na(ppm)
Soil moisture content(%)

Chaiyaphum Province
Dry season
Rainy season
5.30 ± 0.19
5.93 ± 0.48
2.52 ± 0.94
0.61 ± 0.57
0.83 ± 0.14
0.82 ± 0.22

Khon Kaen Province
Dry season
Rainy season
4.31 ± 0.39
4.56 ± 0.26
0.70 ± 0.20
0.37 ± 0.27
0.74 ± 0.16
0.85 ± 0.13

Kalasin Province
Dry season
Rainy season
4.13 ± 0.15
4.41 ± 0.17
0.54 ± 0.34
0.14 ± 0.05
0.68 ± 0.01
0.66 ± 0.10

12.86 ± 1.90

2.82 ± 2.28

3.00 ± 1.28

1.33 ± 0.96

1.57 ± 0.69

0.31 ± 0.16

4.61 ± 0.92

20.24 ± 4.11

5.35 ± 0.63

13.14 ± 5.57

3.30 ± 0.61

11.65 ± 2.38

The water table at the Chaiyaphum site is more shallow than at the other sites. In addition, thegroundwater salinity is also higher, and that makes the soil salinity at Chaiyaphum site higher thanat the other sites (Table 2).
Table 2 The water table depth and groundwater salinity
Site
Chaiyaphum Province
Khon Kaen Province
Kalasin Province

Water table (cm)
Dry season Rain season
19442> 200105> 200116Ⓒ ISERD

42Groundwater salinity (dS/m)
Dry season
Rain season
2.82
1.20
2.16
1.52
1.78
0.76

IJERD – International Journal of Environmental and Rural Development (2015) 6-1

In the plant study, a total of 155 plant species belonging to the 72 families have been recorded.
Five of those were classified as halophytes: Azima sarmentosa, Maytenus diversifolia, Synostema
bacciformis, Pluchea indica and Gisekia pharnaceoides (Fig. 3). The dominant species in theselected sites of the three provinces were Cynodon dactylon, Coldenia procumbent, Ageratum
conyzoides, Glinus oppositifolius, Melochia corchorifolia, Heliotropium indicum and Panicum
repens, respectively (Fig. 4). In the rainy season, the number of plant species at every study site
was higher due to a decrease in soil salinity as compared to the dry season.

Azima sarmentosa

Maytenus diversifolia

Synostema bacciformis

Pluchea indica

Gisekia pharnaceoides

Fig. 3 The halophytes found in the study area
The dominant species found on the slightly saline soils were quite different from those foundon high saline soils and moderate saline soils. Azima sarmentosa, Maytenus diversifolia, andPluchea indica were the dominant species found in areas of high salinity (Kulna et al., 2012).
Combretum quadrangulare, Imperata cylindrical, Cynodon dactylon, Panicum repens,
Sphaeranthus afraricanus, Glinus oppositifolius and Fimbristylis disticha were the dominant
species dicovered growing in moderate salinity (Chason et al., 2014). Also, Cynodon dactylon,Coldenia procumben, Ageratum conyzoides, Glinus oppositifolius, Melochia corchorifolia,
Heliotropium indicum and Panicum repens were the dominant species found growing in slightly
salinity.

Cynodon dactylon

Coldenia procumben

Melochia corchorifolia

Ageratum conyzoides

Heliotropium indicum

Glinus oppositifolius

Panicum repens

Fig. 4 The dominant species found in the study area in the dry season
Table 3 Cover areas and soil electrical conductivity of dominant species in the study area inthe dry season
Plant Name
Cynodon dactylon
Coldenia procumben
Ageratum conyzoides
Glinus oppositifolius
Melochia corchorifolia
Heliotropium indicum
Panicum repens etc.

Cover areas (%)
16.53
14.58
13.33
12.92
12.50
10.83
8.33

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43ECe (dS/m)
0.87 ± 0.97
0.86 ± 0.93
0.74 ± 0.80
0.32 ± 0.11
1.03 ± 1.26
1.34 ± 1.10
0.88 ± 0.85

Number of plant species (species)

IJERD – International Journal of Environmental and Rural Development (2015) 6-1

Soil electrical conductivity (dS/m)

Fig. 5 The relationship between number of plant species and the average soil electricalconductivity (ECe) in the dry season (less salinity more plant species)
CONCLUSION
From the study, some native plants in Northeast Thailand have been found to have become well
adapted to saline conditions, and these plants are called halophytes. The presence of somehalophytes is generally indicative of a saline soil. There is a natural variation in the ability of plants
to tolerate salinity. Most of plant species can grow well when soil ECe is low. On the other hand,some plant species can tolerate in the soil which have high ECe value (Fig. 5). Therefore, thepresence or absence of certain plants can give valuable clues to indicate the degree of soil salinity.
Cynodon dactylon, Coldenia procumben, Ageratum conyzoides, Glinus oppositifolius, Melochia
corchorifolia, Heliotropium indicum and Panicum repens are the dominant species in areas ofslightly salinity. This study has not experimentally evaluated plant species for their use in therestoration or re-vegetation of salt affected areas. However, comparable salinity levels and species
found in the areas suggest that the dominant species observed in this study would be valuable anddeserve further attention as potential candidates for the restoration of salt affected areas.
ACKNOWLEDGEMENTS
This research was support by The Research Group of Problem Soils in Northeast Thailand, Facultyof Agriculture, The Groundwater Research Center, Faculty of Technology, Khon Kaen Universityand Graduate School of Khon Kaen University for supporting the publishers’ research fund. The
authors wish to thank the editor for making suggestions and improving the language of themanuscript.
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Chason, S., Trelo-ges, V., Topark-ngarm, B. and Homchuen, S. 2014. Study on plant species diversity withsoil properties in moderate saline soil of Chi River, Northeast Thailand. Book of Abstracts. The 5thICERD-International Conference on Environmantal and Rural Development. 18-19 January 2014.
Rajamangala University of Technology Thanyaburi, Thailand.

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