1998) and USDA’ Soil Taxonomy (USDA 1999), peat soil is classified as organic
soil or histosol(s) requiring a minimum of 12% (by weight) organic carbon (20%
organic matter) and thickness of 40 cm or more but less if it rests on bedrocks or
lithic contact. However, histosol is not a well-known name, and the term “peat soil”
or “peatland” has been used quite commonly in the world. In Vietnam, the term
"organic soil" had been used for soil characterization and classification by some
previous authors. The term “peat soil” or “histosols” has been used for soil mapping
in recent few decades.
There were variable figures on peatland area in the Mekong Delta showed in
documents previously by the authors. According to previous authors, the total area of
peatlands was quite large, accounted for 228,075 ha (Moormann 1961) or
204,146 ha (Battalion 1967), widely distributed in some provinces in Plain of
Reeds, Long Xuyen Quadrangle, and Ca Mau Peninsula in the MRD. However,
recent inventories of soil types showed the area of peatlands remained only
27,557 ha (1978) and 24,027 ha (1991) (Chieu et al. 1991). Ve and Anh (1990)
and CTU and UAF (1994) reported peatland areas of 34,100 ha.
Differences in the reported peatland areas in the MRD can be due to the limitation
of survey areas and peatland assessment approaches. As previous soil classification
in the Mekong Delta that soils contained peat layers ranged from 40 to 60 cm thick
from topsoil were classified as humus-rich alluvial soils by some authors. Besides,
the ancient abandoned channel courses were rich plant residues storage environments facilitated peat formation; however, not all environments could form
peatlands because some abandoned channel sections were deposited by muds or
organic matter-mixed muds (Quoi 2006). Another reason could be the changes in the
peatlands themselves. Throughout the time, peatlands might reduce in size due to
fire, conversion of peatlands into agricultural lands.
The case of U Minh peat-swamps, located in the Ca Mau peninsula (Fig. 29.1)
illustrated how different references reported different areas. Presently, they are the
largest peatland remaining in Vietnam, composing of two separate zones: U Minh
Thuong (UMT, upper U Minh) and U Minh Ha (UMH, Lower U Minh) (Fig. 29.1),
each of them is now protected as national parks. Moormann (1960, 1961) estimated
U Minh peat-swamps area at 60,000 ha. Tung (1972), based on the detailed
inventory of soil groups by USDA Soil Taxonomy (1960), documented an area of
26,000 ha. In the technical report of the soil map, Tung (1972) also explained
peatland was formed by the accumulation of semi-decaying plant residues in varying
peat thickness, of which soils in peat-swamp margin covered by thin peat layers
classified as Sulfohemists and Sulfihemists. Reviewing the 1976 survey data, Ngo
et al. (2010) stated that the total area of peatland in the U Minh region was about
32,600 ha, of which UMT and UMH were approximately 12,400 ha and 20,200 ha,
respectively. However, based on remote sensing, Nhan et al. (1996) estimated only
about 20,000 ha of peatland remaining in the whole U Minh region.
In the recent surveys, based on aerial photographs taken in 1968 and groundtruthing, Quoi (2010a, 2014b, 2016) documented the area of the former U Minh
peatlands was quite large, approximately 61,314 ha, of which an estimated 35,654 ha
in the UMH and about 25,660 ha in the UMT. The figure is quite consistent with the
29 Management of Peatland in the Mekong River Delta of Vietnam
781
soil or histosol(s) requiring a minimum of 12% (by weight) organic carbon (20%
organic matter) and thickness of 40 cm or more but less if it rests on bedrocks or
lithic contact. However, histosol is not a well-known name, and the term “peat soil”
or “peatland” has been used quite commonly in the world. In Vietnam, the term
"organic soil" had been used for soil characterization and classification by some
previous authors. The term “peat soil” or “histosols” has been used for soil mapping
in recent few decades.
There were variable figures on peatland area in the Mekong Delta showed in
documents previously by the authors. According to previous authors, the total area of
peatlands was quite large, accounted for 228,075 ha (Moormann 1961) or
204,146 ha (Battalion 1967), widely distributed in some provinces in Plain of
Reeds, Long Xuyen Quadrangle, and Ca Mau Peninsula in the MRD. However,
recent inventories of soil types showed the area of peatlands remained only
27,557 ha (1978) and 24,027 ha (1991) (Chieu et al. 1991). Ve and Anh (1990)
and CTU and UAF (1994) reported peatland areas of 34,100 ha.
Differences in the reported peatland areas in the MRD can be due to the limitation
of survey areas and peatland assessment approaches. As previous soil classification
in the Mekong Delta that soils contained peat layers ranged from 40 to 60 cm thick
from topsoil were classified as humus-rich alluvial soils by some authors. Besides,
the ancient abandoned channel courses were rich plant residues storage environments facilitated peat formation; however, not all environments could form
peatlands because some abandoned channel sections were deposited by muds or
organic matter-mixed muds (Quoi 2006). Another reason could be the changes in the
peatlands themselves. Throughout the time, peatlands might reduce in size due to
fire, conversion of peatlands into agricultural lands.
The case of U Minh peat-swamps, located in the Ca Mau peninsula (Fig. 29.1)
illustrated how different references reported different areas. Presently, they are the
largest peatland remaining in Vietnam, composing of two separate zones: U Minh
Thuong (UMT, upper U Minh) and U Minh Ha (UMH, Lower U Minh) (Fig. 29.1),
each of them is now protected as national parks. Moormann (1960, 1961) estimated
U Minh peat-swamps area at 60,000 ha. Tung (1972), based on the detailed
inventory of soil groups by USDA Soil Taxonomy (1960), documented an area of
26,000 ha. In the technical report of the soil map, Tung (1972) also explained
peatland was formed by the accumulation of semi-decaying plant residues in varying
peat thickness, of which soils in peat-swamp margin covered by thin peat layers
classified as Sulfohemists and Sulfihemists. Reviewing the 1976 survey data, Ngo
et al. (2010) stated that the total area of peatland in the U Minh region was about
32,600 ha, of which UMT and UMH were approximately 12,400 ha and 20,200 ha,
respectively. However, based on remote sensing, Nhan et al. (1996) estimated only
about 20,000 ha of peatland remaining in the whole U Minh region.
In the recent surveys, based on aerial photographs taken in 1968 and groundtruthing, Quoi (2010a, 2014b, 2016) documented the area of the former U Minh
peatlands was quite large, approximately 61,314 ha, of which an estimated 35,654 ha
in the UMH and about 25,660 ha in the UMT. The figure is quite consistent with the
29 Management of Peatland in the Mekong River Delta of Vietnam
781