Although trees are found growing in paddy fields everywhere in the Northeastern Region, there are very noticeable differences in their density from area to area. However,
only a few limited surveys have been made of the density
of trees in paddy fields in a few local areas in the region.
Watcharakitti (1979) reported the average density of trees
in paddy fields in the Nam Pong River basin in Khon Kaen
province was 51 trees/ha, with a maximum density of
150 trees/ha, compared to 468 trees/ha in an undisturbed
Dry Dipterocarp Forest. A survey in four sites in Khon
Kaen province by Watanabe et al. (1990) showed that the
density of trees varied greatly from site to site ranging from
30 to 149 trees/ha. Prachaiyo (1993) found that the density
of trees in the paddy fields in 16 villages located in the Phu
Wiang District, Khon Kaen Province, varied between 0 and
13 trees/ha. Prachaiyo (2000) subsequently surveyed a
total of 31 plots in 12 provinces in the Northeast and found
that the density of trees in paddy fields ranged from 4 to
24 trees/ha with an average density of 15 trees/ha. Thus,
although past surveys have reported widely varying densities of trees in paddy fields in different parts of Northeast
Thailand (ranging from 0 to 150 trees/ha), it is difficult to
make any general conclusions about the region as a whole,
because of the different locations where studies were
conducted, the quite differing conditions of the study plots,
and, especially, differences in the times when they were
done. It is well known that the density of trees generally
declines over time (Grandstaff et al. 1986) so that it can be
expected that surveys done at earlier dates will have found
higher densities than are to be expected at present. In
addition, the geographical coverage of these surveys is very
limited so that it is impossible to draw conclusions about
variation in the density of trees in paddy fields in different
parts of the Northeastern Region.
Although trees are found growing in paddy fields everywhere in the Northeastern Region, there are very noticeable differences in their density from area to area. However,only a few limited surveys have been made of the densityof trees in paddy fields in a few local areas in the region.Watcharakitti (1979) reported the average density of treesin paddy fields in the Nam Pong River basin in Khon Kaenprovince was 51 trees/ha, with a maximum density of150 trees/ha, compared to 468 trees/ha in an undisturbedDry Dipterocarp Forest. A survey in four sites in KhonKaen province by Watanabe et al. (1990) showed that thedensity of trees varied greatly from site to site ranging from30 to 149 trees/ha. Prachaiyo (1993) found that the densityof trees in the paddy fields in 16 villages located in the PhuWiang District, Khon Kaen Province, varied between 0 and13 trees/ha. Prachaiyo (2000) subsequently surveyed atotal of 31 plots in 12 provinces in the Northeast and foundthat the density of trees in paddy fields ranged from 4 to24 trees/ha with an average density of 15 trees/ha. Thus,although past surveys have reported widely varying densities of trees in paddy fields in different parts of NortheastThailand (ranging from 0 to 150 trees/ha), it is difficult tomake any general conclusions about the region as a whole,because of the different locations where studies wereconducted, the quite differing conditions of the study plots,and, especially, differences in the times when they weredone. It is well known that the density of trees generallydeclines over time (Grandstaff et al. 1986) so that it can beexpected that surveys done at earlier dates will have foundhigher densities than are to be expected at present. Inaddition, the geographical coverage of these surveys is verylimited so that it is impossible to draw conclusions aboutvariation in the density of trees in paddy fields in differentparts of the Northeastern Region.
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