Rice Field Ecology in Northeastern Thailand: The Effect of Wet and Dry Seasons on a Cultivated Aquatic Ecosystem

235 Pages·1979·8.47 MB·English

by  Charles W. Heckman (auth.)

RICE FIELD ECOLOGY IN NORTHEASTERN THAILAND
MONOGRAPHIAE
BIOLOGICAE
Editor
J. ILLIES
Schlitz
VOLUME 34
Springer-Science+Business Media, B.V. 1979
RICE FIELD ECOLOGY IN
NORTHEASTERN THAILAND
THE EFFECT OF WET AND DRY SEASONS ON A
CULTIVATED AQUATIC ECOSYSTEM
CHARLESW. HECKMAN
Springer-Science+Business Media, B.Y. 1979
Dedicated to my wife Wai-Yuen
ISBN 978-94-009-9593-2 ISBN 978-94-009-9591-8 (eBook)
DOI 10.1007/978-94-009-9591-8
© 1979 by Springer Science+Business Media Dordrecht
Originally published by Dr W. Junk by Publishers The Hague in 1979
Softcover reprint of the hardcover 1s t edition 1979
Cover design M. Velthuijs
No part of this book may be reproduced
and/or published in any form, by print,
photoprint, microfilm or any other means
without written permission from the
publishers.
Contents
1. INTRODUCTION ............................................................................ .
2. GEOGRAPHICAL FACTORS ............•........•......................................... 7
A. Climate................................................................................. 7
B. Topography..... ..... ...... ........ ........ ...... ........ .... .... ..................... 9
C. Geology ................................................................................ II
D. Ethnographic and cultural features............................................. II
3. THE RICE FIELD UNDER INVESTIGATION .............. .... ......... ........... ....... 14
A. Location..... ................. ..... ........ ..... ... ... ..... ........ ... .......... .... .... 14
B. Description ............................................................................ 14
C. Soil....................................................................................... 17
D. Hydrological conditions ........................................................... 21
E. Allochthonous nutrient sources.................................................. 25
F. Vagrant predators ................................................................... 27
4. MATERIALS AND METHODS ... ..... ... .... .... ... ............... ... .......... ......... 30
A. Physical and chemical parameters.............................................. 30
B. Production estimates................................................................ 30
C. Field observations ................................................................... 32
D. Sampling ............................................................................... 33
E. Aufwuchs cultures................................................................... 33
F. Identification of species............................................................ 34
G. Disposition of specimens .......................................................... 34
5. FLORA AND FAUNA ..................................................................... 36
A. Identified species......................... ............................................ 36
B. Community structure............................................................... 36
C. Biogeographical considerations .............................................. .... 66
D. Communities ... , ...... ................... ...... ......... .... ......... ...... ... .... .... 67
E. Autecology............................................................................ 71
1. Floating plants................................................................... 73
2. Creeping plants .................................................................. 75
3. Submerged plants................................................................ 76
4. Emergent, rooted plants ....................................................... 77
5. Littoral plants.................................................. .................. 79
6. Monera............................................................................. 82
7. Fungi................................................................................ 84
8. Algae and protozoa............................................................. 84
9. Metazoa ............................................................................ 110
6. SEASONAL SUCCESSION OF THE BIOTA ........................................ 159
A. The early rainy season .............................................................. 159
B. The late rainy season................................................................ 161
C. Transition to the dry seasons..................................................... 163
v
D. The cool season ........... ................. ....................... ...... ............. 166
E. The hot season........................................................................ 167
7. COMMUNITY METABOLISM .......•..•................................................... 170
A. Dissolved oxygen.................................................................... 170
B. Oxygen transmission ............................................................... 175
c. Photosynthesis ....................................................................... 178
D. Respiration............................................................................ 181
E. Primary production................................................................. 186
F. Efficiency .............................................................................. 189
G. Higher trophic levels ................. ........ ... ................. ........ ...... ..... 192
8. THE RICE FIELD AS A MAN-MADE HABITAT ................................... 195
9. SUMMARy ........................•.•................•........•.............................. 200
10. ACKNOWLEDGEMENTS ..•.....••.....................•................................... 205
11. LITERATURE CITED...................................................................... 207
12. INDEX ........................................................................................ 217
VI
1 Introduction
Research was carried out in Udorn Thani beginning in September, 1975, in order
to elucidate the effects of seasonal changes on the aquatic community of a rice
field. Physical and chemical changes that occur during the course of a year were
recorded and related to the structure and activity of the aquatic biological com
munity. A rice field was selected that is typical of the countless habitats of this
kind that are found in Northeastern Thailand (Fig. 1). For a variety of reasons
these habitats and their location are of special interest (Fig. 2).
Figure 1. The rice field investigated, north of the province capital, Udorn Thani, Thailand.
Northeastern Thailand and a small part of Laos comprise the middle Mekong
Valley. Its geographic situation and climatic conditions set this area apart as a dis
tinct sub-region of Southeast Asia. It is unfortunate that sufficient biological
research has not yet been carried out to delimit the SUb-regions according to their
fauna and flora and to fully describe the various ecosystems that occur in them.
The middle Mekong Valley is one of the most neglected areas of the region, and
there is no comprehensive literature on its biota. Very little ecological information
is available on many of the species that abound there.
The contrast between the wet and the dry seasons is greater in Northeastern
Thailand than in any other part of Southeast Asia. Many species common in more
stable aquatic environments elsewhere in Thailand are absent from or rare in the
Northeast. The species that characterize the rice field biota of the area are those
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that are tolerant of extreme physical and chemical variations in their environment
and have successfully adapted to the climatic and agricultural cycles.
The middle Mekong Valley is a large alluvial plain, with few outstanding
geographical features. Its climate, topography and vegetation are relatively uni
form. A lack of rainfall greatly limits plant growth during the dry season. During
the rainy season rainfall is so frequent and heavy that local flooding often results.
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These floods and the occasional overflow of the Mekong and its major tributaries
bring about renewal of the upper soil layers, maintaining continual fertility of the
land without the need for fertilizers.
Most of the region is under cultivation. It is of special interest that recent
archaeological discoveries in Udorn Thani and the neighboring provinces ofKhon
Kaen and Sakhon N akorn have established the existence of one of the oldest
civilizations yet discovered (Pantarakapises, 1972). The Mekong Valley is now
thought to be the site of the first rice cultivation (Griffin, 1973), and imprints of
rice husks have been found on artifacts dated by thermoluminescence and radio
carbon at about 3500 B.C. (Solheim, 1970).
Regardless of the exact date of its beginning, it is highly likely that rice cultiva
tion in Udorn Thani and its neighboring provinces has been carried on for several
millenia, probably continuously. This has some interesting implications for
ecologists and evolutionary biologists who undertake research in the area.
The concept of a "climax community" entails a stability and equilibrium with
the physical surroundings arrived at after a sere, a progressive series of biological
communities (Ricklefs, 1973). If man is considered part of the ecosystem rather
than an outside force, a long-lasting stability brought about by an unvarying
pattern of human activity could well be considered a climax.
Darlington (1957) and Johnson (1964) suggest that the Sundanian (Malaysian)
Sub-region is a zoogeographical center of diversity, from which many species
spread to populate the Palearctic Region. The rice fields of Northeastern Thailand
are populated predominantly by species also reported from the Malay Peninsula.
There are no geographical barriers sufficient to stop the migration of aquatic
species between Malaysia and the Mekong. The requirement of adaptation to an
alternation between extremes of wet and dry seasons seems to be the major
zoogeographical factor in determining the distribution of the species.
Johnson (1967a) considered the rice fields in Singapore and Southern Malaysia
to be depauperate in fauna. These rice fields have only been cultivated for a little
more than a century. Climax communities, especially those that have existed for a
long time, should be expected to show great species diversity (Ricklefs, 1973;
Woodwell, 1970). A rich variety of flora and fauna in the rice fields of Udorn
Thani could be looked upon as evidence of greater age.'
Man's interaction with the aquatic community in Southeast Asia is evident, not
only from the large number of aquatic species he uses for food, but also from the
adaptation of many aquatic species to feeding on man. Besides the numerous
mosquitoes, leeches and horseflies that feed on mammalian, including human,
blood, many species of Trematoda alternate between aquatic intermediate hosts
and man in the course of their life cycles. The diversity of these species, including
those endemic to Southeast Asia, suggests that the ecosystem has existed more or
less continuously for a long time, long enough for these specific host-parasite
relationships to evolve.
Climax communities should show no average net gain of organic material (E. P.
Odum, 1971). Such is the case in the rice fields of the Mekong Valley. A great
proportion of the organic material produced by the aquatic community during the
year is decomposed at the time much aquatic biota dies off in the dry season, and
much is removed by the farmers during and after the rice harvest. This must be
the case, or the very shallow aquatic habitat would fill up and become dry land in
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