seasonally inundated grasslands of the mekong delta case studies...tram chim national park • 7,600...
TRANSCRIPT
Seasonally inundated grasslands of the Mekong
DeltaTran Triet
Vietnam National University – Ho Chi MinhCity
Delta floodplains
Delta floodplain• Hydrology:
– seasonally inundated by Mekong flood water– nutrient-rich
• Geomorphologic setting:– flat, low-laying, extensive depression areas on both
sides and in between the Mekong and the Bassacchannel
– acid sulphate soils• Vegetation:
– Swamp forest dominated by Melaleuca cajuputi, intermingled with herbaceous marshes
– Permanently inundated marshes/pools– Floating vegetation
U-Minh Thuong
Sea water rise and recede Fresh water arrives
Geology Formation
Sediment >12,000 yBP(old sediment)
Sea water level
Sea water level rise
Marine sediment deposited and shell
appeared
Soil formation (> 6,000yBP)
12,000-6,000 yBP
Sediment contain pyritic materials in 6,000-4,000yBP
Marine sediment deposited in 12,000 - 6,000 yBP
Sediment > 12,000 yBP(old sediment)
Sea water came out
Eroded sediment from up-stream of the Mekong river (rich Fe3+)
deposited in mixed fresh and saline water (rich SO4=) in unaerobiccondition to form Pyrite (FeS2)
Soil formation (6,000 – 4,000yBP)
Fresh water come in
Fe3+ SO4=
Reduction
Fe2+ S-
FeS2
Sediment > 12,000 yBP (old sediment)
Fresh water sediment deposited on top to form the delta and build
river levees
Soil formation (<3,000yBP to date)
Marine sediment deposited in 12,000 - 6,000yBP
Sediment contain pyritic materials in 6,000-4,000yBP
Water level in the dry season
Flood plain wetlands
yriticyritic materialsmaterialsexposed to the airexposed to the air
educe xidi eair/bacteriaflooding/bacteria
Fe(II)(TOXIC)Sulfide
Fe(III)-red hydroxideSulphateH+ (ACIDITY)Jarosite KFe3(SO4)2(OH)6
Aluminium (solid)acid (pH<4)
Al3+(aq.)(TOXIC)
yrite e 2
Potentially ASS
Severely & moderately
ASS
A: Horizon with Organic matters
Bg: Horizon (with Brown/Red mottles)
Bj: Horizon (with Brown and/or Jarosite mottles)
C: Horizon (with Pyritic materials)
A typical profile of Acid Sulphate Soil
Ground water level during the dry season
Melaleuca swamp forest
Seasonally inundated grassland
Eleocharis dulcis
Inundation duration: longInundation depth: medium to highAcidity: highSalinity: low to medium
Eleocharis spiralis
Inundation duration: mediumInundation depth: medium Acidity: highSalinity: medium to high
Lepironia grassland
Inundation duration: mediumInundation depth: mediumAcidity: mediumSalinity: low to medium
Ischaemum grassland
Inundation duration: short to mediumInundation depth: low to mediumAcidity: low to mediumSalinity: low
Panicum grassland
Inundation duration: short to longInundation depth: low to mediumAcidity: low to highSalinity: low to medium
Phragmites grassland
Inundation duration: mediumInundation depth: medium Acidity: mediumSalinity: low
Aquatic vegetation in permanently inundated wetlands
Bassac Marsh
Boeung Prek Lapouv
Tram Chim
Ha Tien Plain
Lang Sen
Threats
• Changing of floodplain hydrology due to:– irrigation– flood control
• Wetland loss due to agricultural expansion
• Pollution
Tram Chim National Park• 7,600 ha• Mosaic of Melaleuca
forests, grasslands and swamps
• Critical habitats for many species of water birds, including the Eastern Saruscrane (Grus antigonesharpii)
Eastern Sarus crane
A flagship species of Tram Chim National Park
Sarus Crane Movements
= KNOWN DRY SEASON LOCATIONS
Mekong Delta
?
Stung Treng, Cambodia
NEST
ADULT
Tram Chim, Vietnam
Eleocharis spp. (Cyperaceae)
tubers
= Water Gate
Hydrological restoration
Water management
0
50
100
150
200
250
300
350
400
450
5001-
Jun-
95
1-Au
g-95
1-O
ct-9
5
1-D
ec-9
5
1-Fe
b-96
1-A
pr-9
6
1-Ju
n-96
1-Au
g-96
1-O
ct-9
6
1-D
ec-9
6
1-Fe
b-97
1-A
pr-9
7
1-Ju
n-97
1-Au
g-97
1-O
ct-9
7
1-D
ec-9
7
1-Fe
b-98
1-A
pr-9
8
1-Ju
n-98
1-Au
g-98
1-O
ct-9
8
1-D
ec-9
8
1-Fe
b-99
1-A
pr-9
9
1-Ju
n-99
1-Au
g-99
1-O
ct-9
9
1-D
ec-9
9
1-Fe
b-00
1-A
pr-0
0
1-Ju
n-00
1-Au
g-00
1-O
ct-0
0
1-D
ec-0
0
1-Fe
b-01
1-A
pr-0
1
1-Ju
n-01
1-Au
g-01
Wat
er le
vel (
cm A
MSL
)
Water level
Ground level
Water level inside the core zone of Tram Chim National Park
December, 1992 March, 1994
September, 1996 February, 1998
March, 2001
Water birds increased
Cranes decreased
469
6148 898216734
68
497
365
1052
814741
665
159113
302271
631
503
511
0
200
400
600
800
1000
1200
1986
1988
1990
1992
1994
1996
1998
2000
2002
2004
2006
Hig
hest
num
ber o
f cra
nes
obse
rved
Number of cranes visiting Tram Chim 1986 - 2006
Number of cranes coming to Tram Chim
0
200
400
600
800
1000
2001 2002 2003 2004 2005 2006
Num
ber o
f cra
nes
Mekong Delta Ang Trapeang Thmor Small Wetlands of Open Forest
CRANE POPULATION IN THE LOWER MEKONG BASIN 2001 - 200