Tài liệu Growths and Carbon Stocks of Para Rubber Plantations on Phonpisai Soil Series in Northeastern Thailand ppt

Growths and Carbon Stocks of Para Rubber Plantations on Phonpisai Soil Series in Northeastern Thailand Chakarn Saengruksawong Soontorn Khamyong, Niwat Anongrak, Jitti Pinthong Departme

Growths and Carbon Stocks of Para Rubber

Plantations on Phonpisai Soil Series in

Northeastern Thailand

Chakarn Saengruksawong Soontorn Khamyong, Niwat Anongrak, Jitti Pinthong

Department of Plant Science and Natural Resources, Faculty of Agriculture Institution: Chiang Mai University

a natural forest Totally 15, 40 x 40 m sampling plots were used for studying rubber growths, three plots per each aged class plantation and one plot for the natural forest In each plot, stem girth at 1.3 m above ground, crown width and height of trees were measured One rubber tree having the mean growth in each aged class plantation was cut and separated to stem, branch, leaf and root biomass for making allometry equations Fifteen soil pits were made in each plot, and soil samples were collected along soil profile Soil physical and chemical properties were analyzed in laboratory Rubber tree densities varied between 80-109 trees/rai (1ha = 6.25 rai) Stem girth and height growths were increased with the plantation ages The growths were very rapid for rubber trees having ages between 1 and 15 years old and become slow for the older trees The biomass amounts of

1, 5, 10, 15 and 20 years old plantations were in the order of 21.25, 55.24, 102.39, 140.50 and 215.39 Mg/ha Ecosystem carbon stocks in these plantations were increased with tree ages as 26.29, 48.28, 76.62, 95.83 and 135.38 Mg/ha, respectively They involved two compartments; (1) biomass carbon: 12.03, 31.45, 58.10, 79.78 and 122.01 Mg/ha; and (2) soil carbon: 14.26, 16.83, 18.52, 16.05 and 13.37 Mg/ha The total carbon storage in natural forest was 134.62 Mg/ha; 124.20 Mg/ha in biomass and 10.42 Mg/ha in soil The young plantations had the high carbon percentages in soil and low in biomass whereas carbon allocation in the older plantations was higher in biomass and lower in soil system

Introduction

Thailand is the world leading producer

and exporter of para rubber (herein called

rubber) with production capacity of 3.1 – 3.2

million tons per year, with 88-90 percent of

total production capacity exported to foreign

markets The country also has high potential

for expanding production area and raising

production capacity In year 2009, rubber

plantations in Thailand covered 2.70 million ha

across Thailand with the majority (2.10 million

ha) in the traditional areas in the southern (2.61

million ha) and eastern 14.68 million ha)

region and the remaining 0.60 million ha are

planted in new areas in the northeastern (0.45

million ha), northern (0.09 million ha) and

central (0.05 million ha) region

The northeastern region of Thailand has

agricultural area of 15.90 million ha, of which

6.65 million ha are suitable for rubber

plantation However, only 3.09 million ha,

have yield more than 1,562 kilogram per ha

per year and currently 0.45 million ha are

being used for rubber plantation The

remaining 2.65 million ha, an area equal of

total area being for rubber production today, is

still available for additional rubber production

Hence, northeastern region of Thailand will be

an important rubber production source for

Thailand in the future

Global warming is a present problem and

spreading throughout the world, encouraging

all nations to take various measures to reduce

global warming under the KYOTO protocol

The protocol is a part of the United Nations

Framework Convention on Climate Change

(UNFCC), enforced in 2005 Even if Thailand

is a non-annex 1 member country that can

reduce greenhouse gas emission through the

clean development mechanism, the appropriate

approach is to plant para rubber plantation in

place of deforestation in Thailand Because

rubber trees have production life of 20 years,

the plantation can be considered as forest

plantation as rubber tress increase in biological

mass as they age and has high capacity for

carbon stock storage

Development of northeastern region as part of the country’s rubber production source will need a study on environmental affect on growth pattern in different areas of the region, especially rainwater, humidity, soil characteristic and rock formation Different soil qualities have strong affect to the debt of water drainable, physical, chemical and biological properties (Bowen & Nambiar, 1989; Fisher & Binkley, 2000) It will also influence the amount of carbon stock stored in different age group of rubber trees hence will affect the environmental role of rubber plantation and will be an important data for better management at relevant organizations Nongkhai Province has plantation area of 724,590 ha with areas suitable for rubber plantation of 340,606 ha It is also the province with most area used for rubber plantation in its region, coving 102,051 ha and also has remaining potential land use of 238,3994 ha Moreover, it is the first test province with pilot plantation project by the Rubber Research Institute of Thailand (RRIT) in year 1978, giving it many test plantation aging from 1 year old to 20 years old Investigation from the Land Development Department shows that most soil type found in the area is the Phonpisai soil coveringin 153,410 ha Studies

on the growth pattern, bio-productivity, and carbon stock potential on Phonpisai soil type is

an interesting topic and will provide important data for the development of management and encouragement of appropriate rubber plantation that give high yields and rehabilitate the environment

Methods

Research site

The research site is located in Rattanawapi District and Phonpisai District, Nong Khai Province The site is located between latitude

17 degrees 52 minutes north and longitude 102 degrees 44 minutes east The land elevation from normal sea level sits between 161-200 meters with incline of 1-7%

Growth and biomass of rubber

Three samples are selected from five

different age groups of plantations including 1

year, 5 years, 10 years, 15 years and 20 years

old that are 40 x 40 square meters in size

Growth studies are done by measurements of

the tree circumference at height of 130

centimeters from the ground as well as

measuring the total height of the tree itself

Biomass measure for the tree in each age

group are determined by cutting trees with

similar size and height to the average tree in

each plantation, one for each age group

Samples trees are then divided into trunk,

branch, leaves and roots for analysis between

biomass and D2H to determine the carbon in

each part of the tree as well as the entire carbon

stock

Growth of plant species and biomass in

referenced natural forest

Research samples are selected from

sample sites in natural forest of Phonpisai

District that are in close proximity to pilot

plantation Natural forests in the area consist of

dipterocarp forest size of 40 x 40 square meters

measuring tree diameter at 130 centimeter

height as well as plant species with height of

over 1.50 meters The quantitative calculations

of each plant species include the density,

important distinction and indicators

Qualitative biodiversity data includes listing

names of plant species in the area in both

common and scientific names and calculation

the biomass of plant species with the following

formula Ogino et al (1967)

W S (trunk) = 189 (D2H)0.902

W B (branhc) = 0.125 W S

1.024

1/W L (leaves) = (1/W S0.9) + 0.172

when W = biomass (kilograms per hectare)

D = diameter at 1.3 meters from ground

(meters)

H = tree height (meters)

Soil characteristics, carbon stocks and

nutrition

Soil studies affecting rubber and plant

species growth in sample plantations and

natural forests are conducted by digging for three sample soils in plantations aged 1, 5, 10,

15 and 20 years old as well as one sample soil

in natural forests, totaling 16 dig sites Each dig sites are 1.5 meters wide, 2.0 meters long and 1.2 meters deep Studies and analysis on soil characteristic are done by studying the physical and chemical properties of the soil Physical properties studied includes (1) total soil density of the soil through the core method, (2) gravel quantity for size more than

2 mm by weighting method, and (3) size distribution and soil texture by hydrometer method Chemical property studied includes (1) soil reaction by pH meter method in ratio of 1:1 with water, (2) carbon exchange capcity (CEC), (3) total nitrogen by micro Kjedahl method, (4) organic matter and carbon in soil by wet oxidation method of Walkley and Black (Nelson and Sommers, 1982), (5) useful phosphorous concentration

particle-by Bray II and colorimetric method, (6) useful potassium level by extracting with ammonium acetate 1N, pH 7.0 and measured by flame photometer and (7) calcium and magnesium concentration extracted with ammonium acitate 1 N, pH 7.0 and measured by atomic absorption tool Calculations of carbon level in soil from soil mass and carbon concentration fluctuation in each soil level were also conducted

Results and Discussion

Growths

Growth of rubber consists of the diameter, height and bush size which will differentiate between age groups

Table 1 shows the growth of rubber tree in each age group It is found that the density of the rubber tree varies a little The density of age groups 1, 5, 10, 15 and 20 years old averages at 78, 71, 79, 81 and 85 respectively The circumference of the tree increases as the tree age Trees aged 1, 5, 10, 15 and 20 years old have average circumference of 8.23, 29.42, 36.76, 53.54 and 54.45 respectively The average heights are 6.49, 8.83, 11.98, 15.41 and 14.46 centimeter and bush sizes of 2.60,

4.80, 5.30, 6.40 and 5.70 centimeters

respectively

As for the amount of rubber tree that can

be harvested according to recommendations of

the RRIT, it is found that 5 years old

plantations do not have trees with

circumference higher than 50 centimeters, the

size appropriate for harvesting Only 1.69% of

10 years old trees have circumference

measurement higher than 50 centimeters The

ratio increases to 65.88% and 67.45% for 15

and 20 years old plantations respectively

For the diameter of the trees, the standard

used for rubber wood purchases, it is found

that pilot plantations have diameters of 6

inches or more for 10 years old plantations

However, only 5.91% of 10 years old tress

have diameter more than 6 inches and

increases to 53.31% and 56.86% for 15 and 20

years old plantations respectively

Compared to southern rubber plantations,

the circumference, diameter and ratio of

harvest-read samples of the rubber trees in the

northeastern region is lower This is due to the

lower fertility of the soil in the northeastern

region

As for the height and branching level

comparison with the southern region, pilot

plantations in the northeastern region are

similar to that of the southern region for the

same age groups

Biomass

Average biomass for the pilot plantation

in each age group from 1, 5, 10, 15 and 20

years old equals to 3.2, 43.0, 94.5, 278.8 and

264.9 kilograms per tree respectively Table 2

shows the biomass per area with plantations

aging 1, 5, 10, 15 and 20 years old having total

biomass of 1.54, 19.10, 46.66, 140.56 and

140.73 Mg/ha respectively

1 year old plantation has average

biomass of 1.54 Mg/ha Biomass from trunk,

branch, leaves and roots equal 0.63, 0.13, 0.25

and 0.52 Mg/ha respectively, calculated into a

ratio of 37.07, 30.13, 6.69 and 26.15 percent

respectively 5 years old plantation has

average biomass of 19.10 Mg/ha Biomass

from trunk, branch, leaves and roots equal

7.07, 5.75, 1.28 and 5.00 Mg/ha respectively, calculated into a ratio of 40.84, 8.73, 16.41 and

34.02 percent respectively 10 years old plantation has average biomass of 46.66

Mg/ha Biomass from trunk, branch, leaves and roots equal 15.43, 18.59, 2.23 and 10.41 Mg/ha respectively, calculated into a ratio of 33.07,

39.84, 4.67 and 22.30 percent respectively 15 years old plantation has average biomass of

140.56 Mg/ha Biomass from trunk, branch, leaves and roots equal 39.01, 72.50, 4.31 and 2.49 Mg/ha respectively, calculated into a ratio

of 27.29, 52.37, 2.97 and 17.36 percent

respectively 20 years old plantation has

average biomass of 140.73 Mg/ha Biomass from trunk, branch, leaves and roots equal 39.01, 72.50, 4.31 และ 2.49 Mg/ha respectively, calculated into a ratio of 27.72, 51.52, 3.06 and 17.70 percent respectively

Biomass of rubber trees increases as they age with very fast rate from 1 to 15 years old and slows down during 15 to 20 years old The ratio of biomass accumulation in each part of the tree also changes as they age In plantation aged 1, 5, 10, 15 and 20 years old, the ratio of biomass accumulation compared to the total biomass equals to 40.84, 37.03, 33.07, 27.29 and 27.72 respectively The ratio for the branch increases as the tree age, from 8.73 to 30.13, 39.84, 52.37 and 52.52 percent respectively In contrast, the ratio for the leaves and roots decreases

Fig 1 Stem girth and height growths, and biomass of para rubber in 1-, 5-, 10-, 15- and 20-year-old

plantations on Phonpisai soil series

Ponpisai

0 5 10 15 20 25 30

Table 1 Growths and biomass of para rubber in different age plantations on Phonpisai soil series

Plantation Plot Density GBH Height

Crown width Biomass age (years) No (trees/rai) (cm) (m) (m) (kg/tree)

Table 2 Biomass of para rubber in different age plantations on Phonpisai soil series

Physical and chemical properties of the

soil are shown in Table 3 and Table 4

1 Physical properties

Soil texture: the soil in nearby

dipterocarp forest is considered the natural

soil in the area The top soil is sandy clay

loam soil and bottom soil is clay Soil

texture in top soil found natural forest and

1, 5, 15 and 20 years old rubber plantations

to have sandy clay loam and 10 years old

planation to have clay soil For bottom soil,

natural forest and 20 years old plantations

have clay soil, 1 and 10 years old

plantations have sandy clay loam to clay

and 5 and 15 years old plantation have

sandy clay loam to clay soil

Bulk density: The top soil of

natural forest has medium density (1.52

Mg.m-3) and bottom soil has low to high density Soil of 1, 5 and 10 years old plantation has very high density (2.21 Mg.m-3) and 15 years old plantation has medium density (1.52 Mg.m-3) However,

20 years old plantation has fairly low density (1.33 Mg.m-3) Bottom soil has high fluctuation with values from fairly low to very high and no difference is found between age groups

Particle density: Top soil in natural

forest has value of 2.09 Mg.m-3 and increase slightly according to the depth Soil for plantations aged 1, 5, 10, 15 and 20 years old has values of 2.42, 2.66, 2.55, 2.28 and 2.39 Mg.m-3 respectively The values are fairly higher than natural forest but no changes are observed between natural forest age groups Bottom soil have fluctuated values similar to the top soil and no changes between plantation age groups

Rubber trees in plantations affect the

property of the soil such as the temperature

and humidity, which in turns affects the

decomposition of rocks and minerals as

well as the decrease of top soil erosion as

the trees age For the soil and density of the

soil itself, it is found that there is little

changes and no differences are observed

between each age groups

2 Soil chemical properties

pH: Top soil and bottom soil of

plantations aged 1, 5, 10, 15 and 20 years old

have high reaction level of 4.6-5.0 pH The

levels are similar to the nearby forest and no

difference between age groups is observed

Organic matter contents: Top soil in the

Ap region for the plantation agede 1, 5, 10, 15

and 20 years old have values of 46.6, 12.1,

17.6, 28.6 and 15.1 g/kg respectively The

values are medium to high and there is no

difference between age groups, which could

result from irregular use of fertilizers The

bottom soil have fairly low to very low values

while natural forest have fairly high value of

32.9 g/kg in top soil and low to very low in

bottom soil

The amount of organic carbon and

nitrogen are subject to change similar to the

other organic matter in the soil

Available phosphorous: Top soil in

plantation aged 1, 5, 10, 15 and 20 years old

have values of 3-5 mg.kg-1 which is low

Bottom soil has very low level For natural

forest, top level have fairly low level (7

mg.kg-1 ) and low to very low for bottom soil

Available potassium: Top soil in

plantation aged 1, 5, and 10 years old have low

to medium values (47-83 mg/kg) and high

level in 15 and 20 years old plantations

(100-110 mg/kg) Bottom soil has high fluctuation

from low to very high but no difference

between age groups Natural soil has high

levels across the soil levels

Cation exchange capcity: Top soil in

plantations aged 1, 5, 10, 15 and 20 years old have values of 7.6, 4.1, 7.1, 6.4 and 3.6 cmol/kg respectively The levels are fairly low

to low and no difference is observed between age groups Bottom soil has high fluctuation from low to fairly high but no difference between age groups For top soil in natural forest, the level is fairly low and for the bottom soil it is medium to fairly high level

Base saturation: Top soil in plantations

aged 1, 5, 10, 15 and 20 years old have values

of 51.40, 26.79, 24.12, 35.10 and 24.75% respectively The levels are low to medium and

no difference between age groups Natural forest has medium level in top soil and low level in bottom soil

Decomposed leaves and parts above the soil of the rubber tree on the ground, as well as the dead roots, will decompose to organic matter in the soil and release various nutrient into the ground The quantity should increase

as the trees growth However, there are no different in the chemical property of the soil between the age groups This may due to the organic matter and nutrient being used and stored in the biomass Some parts are lost with the top soil erosion Moreover, the use of fertilizers can also cause high fluctuation in the organic matter of the top soil

Table 3 Soil physical properties under different age rubber plantations and adjacent dry dipterocarp forest on

Ponpisai soil series

Horizon Depth (cm) Particle size distribution (%) Gravel Bulk density Particle density

Table 3 Soil physical properties under different age rubber plantations and adjacent dry dipterocarp forest

on Ponpisai soil series

Horizon Depth (cm) Particle size distribution (%) Gravel Bulk density Particle density

Dry dipterocarp forest

Table 4 Soil chemical properties under different age rubber plantations and adjacent dry dipterocarp forest on

Ponpisai soil series

Carbon Stocks in Para Rubber Plantations

and Natural Forest

1 Biomass carbon storages

(1) Rubber plantations

Rubber trees synthesis light and absorb

carbon dioxide to produce carbohydrate This

result in carbon accumulation in organic form

The estimate of carbon accumulation level can

be calculated from the biomass (dry mass)

Hence, biomass is related to the growth rate

and density of the rubber tree in each age group

Biomass data and analysis of carbon level

in each part of the tree can be used to calculate

carbon stock in the biomass The density of

carbon in the trunk varies very little between 1

to 20 years old tree between 56.0 to 57.50%

For the leaves and roots, the average is at 54.89

and 57.08% respectively As shown in Table 5,

it can be seen that plantations aged 1, 5, 10, 15

and 20 years old have carbon level in the

biomass in total of 0.87, 10.92, 26.68, 80.23

and 80.57 Mg/ha respectively

1 year old plantation has average carbon

in biomass of 0.87 Mg/ha, divided into trunk,

branch, leaves and roots equal to 0.36, 0.08,

0.14 and 0.30 Mg/ha respectively 5 years old

plantation has average carbon in biomass of

10.92 Mg/ha, divided into trunk, branch,

leaves and roots equal to 4.06, 3.31, 0.70 and

2.85 Mg/ha respectively 10 years old

plantation has average carbon in biomass of

26.68 Mg/ha, divided into trunk, branch,

leaves and roots equal to 8.84, 10.67, 1.23 and

5.94 Mg/ha respectively 15 years old

plantation has average carbon in biomass of

80.23 Mg/ha, divided into trunk, branch,

leaves and roots equal to 2.19, 42.06, 2.29 and

13.93 Mg/ha respectively 20 years old

plantation has average carbon in biomass of

80.57 Mg/ha, divided into trunk, branch,

leaves and roots equal to 22.36, 41.62, 2.37

and 14.21 Mg/ha respectively

Carbon stock in biomass for rubber

plantation increase as they age, with highest

rate during 1 to 15 years old trees and slow

down in 15 to 20 years old trees The ratio of

biomass in each organ changes as the trees age

similar to the biomass level Compared to

RRIM 600 in 25 years old plantation of eastern

region, it is found that the sample 20 years old plantations have less carbon stock than in rubber plantation of eastern region This is due

to the lower growth period from dry climate, low soil fertility and high density of trees in

each plantation of up to 91 trees/rai

(2) Natural forest

Table 6 and 7 shows that dipterocarp forest has 76 plant species with density as high

as 1,119 trees/rai Specie with highest density

is the S obtusa with S siamensis and C subulatum Specie with highest significant factor is the S obtusa (18.05% of all species) and S siamensis, C subulatum, C formosum and M edule having 15.86%, 10.23%, 3.61%

and 2.77% significant factor respectively The five species have aggregate significant factor

of 50.52% of all plant species Biomass of all plant species equals 92.48 Mg/ha, divided into trunk, branch, leaves and roots to 60.21, 15.54, 2.84 and 13.89 Mg/ha respectively Carbon sock level in biomass equals to 45.68 Mg/ha, divided into trunk, branch, leaves and roots to 30.04, 7.57, 1.37 and 6.70 Mg/ha respectively

Species with highest accumulation are the S siamensis, S obtuse, C subulatum, T alta, D obtusifolius, respectively

Originally, dipterocarp forest was in bad condition with maintenance level similar to 20 years old plantations It is a forest recovering fertility with biomass around 92.48 Mg/ha Most biomass, 53.20%, comes from three

species in S obtuse, S siamensis and C subulatum The rest of 46.80% are biomass of

the other 73 plant species with values similar

to 7-15 years old rubber plantations

The creation of rubber plantation is thus an increase in carbon stock for the environment that is facing global warming When compared

to the rubber plantation covering 0.45 million

ha, the northeastern region can contain 18-23 million metric tons for the earth atmosphere However, the observed plantations were not maintained properly If farmers can develop proper planting technique and maintenance procedure, the plantations in the northeastern region will be an important area for rubber and carbon production, similar to the level of the southern region

0 2,000 4,000 6,000 8,000 10,000 12,000 14,000 16,000

Fig 2 Biomass carbon stocks in rubber plantations on Phonpisai soil series

Table 5 Biomass carbon storages in rubber plantations on Ponpisai soil series

Plantation Plot Carbon amounts (kg/rai)

Total biomass carbon Age (years) No Stem Branch Leaf Root Total (Mg/ha)

Table 6 Plant biomass in the natural dry dipterocarp forest

Species Plant name Biomass (kg/rai)

Table 7 Biomass carbon storages in the natural dry dipterocarp forest

No Plant name Stem Branch Leaf Root Total

Speci Biomass Carbon

2 Carbon storages in soils

Accumulated carbon in the form of

organic matter is different between each age

group Natural forest have organic matter of

57.81 Mg/ha, calculated to carbon level of

33.53 Mg/ha In plantations aged 1, 5, 10, 15

and 20 years old, the level is at 37.37, 64.41,

49.37, 53.85 and 20.74 Mg/ha respectively

With the average carbon in organic matter is

at 58 percent, the carbon level is calculated to

be 21.67, 37.36, 28.64, 31.23 and 12.03 Mg/ha respectively

1 year old plantations have higher carbon level than older plantations because of the plowing that produces humus For 5 years old plantation, the level is lowest from the erosion of the top soil The carbon level increases along with the age but 20 years old plantations have low level, possibly due to the originally low fertility level of the soil and partly due to the top soil erosion

Table 8 Biomass carbon storages in soils under rubber plantations and dry dipterocarp forest

Horizon Depth Soil Organic matter Org Carbon

(cm) (kg/m 2 ) (kg/rai) (kg/ha) (kg/rai) (kg/ha)

3 Ecosystem carbon storages

Accumulation of carbon level in the

ecosystem can be divided into two

types, the accumulation in biomass and

accumulation in soil In natural forest,

the carbon level in the ecosystem

measures to 79.21 Mg/ha while in rubber

plantations aged 1, 5, 10, 15 and 20 years

measures to 22.54, 48.28, 55.32, 111.46

and 92.60 Mg/ha respectively

The amount of carbon increases as the biomass of the rubber trees increases

as they age Younger plantations have high ratio of carbon in the ground and decreases

as they age The ratio of accumulation in biomass also increases as they age However, 20 years old plantation has lower carbon accumulation than 15 years old plantation The reason maybe the inappropriate environment and some part due to the different in management

Table 9 Ecosystem carbon storages in rubber plantations and dry dipterocarp forest

Ecosystems Biomass carbon Soil carbon Total

Plantation in Phonpisai area was

dipterocarp forest, with original rock

formation as hard rock, siltstone and sandy

stone Soil in dipterocarp forest is 5

centimeters thick When turned into rubber

plantation, the plowing increases the

thickness to 15-20 centimeters Original

top soil in dipterocarp forest is sandy clay

loam and bottom soil is clay soil The soil

content and density has very little change

between plantation age groups Soil

reaction in top and bottom soil is very

high Organic matter in top soil is medium

to high Available P is low CEC is fairly

low to low Base saturation is medium to

low These properties do not vary between

age groups and are similar to natural

forest As for the available K, the trend is

to increase in the top soil of older

plantations but still similar to natural

forest

The density of the rubber tree has

some differentiation between age groups

with the value of 71-85 trees per rai The

circumference increases as the trees age, with plantations aged 1, 5, 10, 15 and 20 years old averaging 8.23, 29.42, 36.76, 53.54 and 54.45 centimeters respectively The average height averages 6.49, 8.83, 11.98, 15.41 and 14.46 centimeters and diameter averaging 2.60, 4.80, 5.30, 6.40, and 5.70 centimeters respectively When compared to the trees in the southern region, the tree circumference and available trees for harvest is lower

Average biomass of rubber trees for plantations aged 1, 5, 10, 15 and 20 years old equals to 3.2, 43.0, 94.5, 278.8 and 264.9 kg/tree respectively Biomass per area averages 1.54, 19.10, 46.66, 140.56 and 140.73 Mg/ha respectively Hence, the biomass increases as the trees age with highest rate between 1 to 15 years old and slows down when 15 to 20 years old The ratio of biomass accumulation in each part

of the tree also changes as they age with the branch increasing in biomass and leaves and roots decreasing When the

trees are 20 years old, the biomass is 48.24

Mg/ha higher than dipterocarp forest

Amount of accumulated carbon in biomass

of rubber plantation also increases by age

with the highest rate during 1 to 15 years

old and slows down during 15 to 20 years

old Plantations aged 1, 5, 10, 15 and 20

years old have total carbon level of 0.87,

10.92, 26.68, 80.23 and 80.57 Mg/ha

respectively while dipterocarp forest only

have 45.68 Mg/ha Even if there is less

carbon stock in Nong Khai District

compared to those in eastern region, the

future bolds well when rubber trees in

Nong Khai grow and increase in size to

near carbon stock level of plantations in

the eastern region

Phonpisai soil is usually covered with

dipterocarp foreset that have regular forest

fire during the dry season The soil erosion

is also high with low level of water

absorption during rainy season The soil is

very shallow and low in fertility

Plantation of rubber tree in this soil for all

age groups, 1 to 20 years old, slowly

changes the soil property of the area

However, the soil nutrient is also used by

the rubber trees as biomass at a higher rate

than natural forest, especially the

accumulation of carbon in biomass

Even as the current growth of rubber

trees in the northeastern region is lower

than that of the southern region, mainly

due to the different environment and lower

soil fertility, the future of the northeastern

region as a major rubber plantation area is

possible Support to the farmer to maintain

rubber trees in good quality is needed in

order to increase rubber growth rate to be

on par with southern region Rubber

plantation in northeastern region will be an

important source for national carbon stock

Other than helping with global warming,

the plantations will also help generation

income to the farmers and the country

Plantations in the northeastern region of

around 0.45 million ha can serve as carbon

stock for 18.23 million metric tons In the

future, the area has available plantation

area as high as 2.67 million ha that can be utilized as important national carbon stock and create value up to 10 billion Baht

Acknowledgement

The authors would like to thank Director General of Department of Agriculture, Director General of Land Development Department and Director of Department of Plant Science and Natural Resources, Faculty of Agriculture, Chiang Mai University for chemical analysis of plant and soil samples as well as Nongkai Rubber Research Center staffs for facilitate soil samples collection Thanks to students in Department of Plant Science and Natural Resources, Faculty of Agriculture, Chiang Mai University for their help during soil sampling and measuring rubber growths

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Saichai Suchartgul1, Somsak Maneepong2, and Montree

Issarakrisila2

1 Surat Thani Rubber Research Centre, Ta-Chana District, Surat Thani Province, 84170, 2School of Agricultural Technology, Walailak University, Tha Sala, Nakhon Si Thammarat, Thailand 80160

or yield and sustain soil quality in the same time This study was aimed to establish standard values for immature rubber tree A nutrient survey was carried out during June - July

2009 in the east coast of Chumporn, Surat Thani and Nakhon Si Thammarat provinces The data were collected from 43 farmers who grew rubber of the RRIM 600 variety The girths at 150 cm height of 4 year-old rubber were measured in 100 trees from each plantation Soil and leaves were sampled in the area of girth measured trees The samples were analyzed for chemical properties and nutrient concentrations Correlations between the obtained values and mean girths were fitting by a quadratic equation The result of tentative standard values revealed that the optimum ranges for soil pH, base saturation, and exchangeable acidity were 4.5 – 5.0, 25 - 75 % and 10 - 30 m mol (+)/kg respectively The optimum ranges for P (Bray 2), K (1 M

NH4OAc pH 7), Ca (1 M NH4OAc pH 7), S (0.01 M

KH2PO4), Fe (DTPA), Cu (DTPA), Zn (DTPA), and B (hot 0.01 M CaCl2) concentrations in soil were 10 - 20, 40 - 80,

50 - 600, 25 - 35, 30 - 90, 0.5 - 1.5, 0.5 - 1.5 and 0.3 - 0.7 mg/kg respectively The optimum ranges for K/Mg, K/Ca and Mg/Ca in soil were 2.0 - 6.0, 0.4 - 1.4 and 0.2 - 0.6 respectively The optimum ranges for N, P, K, Ca, Mg and

S concentrations in leaves were 3.2 - 3.8, 0.25 - 0.30, 1.0 - 1.4, 1.0 - 1.5, > 0.35 and 0.2 - 0.3 % respectively, and for

Fe, Mn, Cu, and B were 90 - 130, 300 - 500, 10 - 15, and 40

- 80 mg/kg respectively The optimum ranges for K/Mg, K/Ca and Mg/Ca in leaves were 3.0 - 4.2, 0.8 - 1.4 and 0.3 - 0.5 respectively The optimum ranges of CEC, Mg in soil,

Mn in soil and Zn in leaves were unable to establish