Stand Structure of a Seasonal Dry Evergreen Forest at Huai Kha Khaeng Wildlife Sanctuary, Western Thailand

18 Pages·2001·0.57 MB·English

by  Bunyavejchewin, Sarayudh

NAT. HIST. BULL. SIAM Soc. 49: 89-106，20 01
STAND STRUCTURE OFA SEASONAL DRY EVERGREEN
，
FOREST ATH UAI KHAK HAENG WILDLIFE SANCTUARY
WESTERN THAILAND
Sarayudh Bunyavejchew帥1，Patrick J. Bake';，Ja mes V. LaFranki~，
and Peter S. Ashton4
ABSTRACT
Wed escribe the structure of as tand of seasonal dry evergreen forest located in the Huai
KhaK haeng.Wildlife Sanctuary (HKK)，Ut hai Thani Province based on ac ensus of all trees
註Icmdbhina50一haplot. Mean densities wel官 1，613trees ha-I(註 1cm dbh)，4 39出es
ha-I(. .10 cm)，an d 3.74紅eesha-I註( 100cm). Mean basal area was 30.45 m2h a-I(. .1 cm dbh)，
28.69 m2h a-I注( 10cm dbh)，5. 57 m2h a-I注( 100cm dbh). Thes tand structure (density and
basal ea)of the seasonal dry evergreen fostat HKK is comparable to published reports of
釘 陀
stand structure for other seasonal evergreen fo陀sts1目別lailandand would app巴紅tobe gen-
erally representative of the forest type. TheH KK plot was much less dense (1，613 trees
ha-I注1cm dbh)出ansimilar plots in Malaysia (6，769 t陀esha-I注1cm dbh) and Panama
(4，882 trees ha-I邑1cm dbh)，a1 though had similar values for total basal釘ea.百lem句or
di首erencebetween the forest types was in the density of the saplings. For位ees..10 cm dbh
the seasonal dry evergreen forest plot was as dense or denser than the lowland甘opicalforest
plots. lndividual tree species' diameter distributions exhibited av ariety of forms，fr om negative
exponential to unimodal to irre別lar;however，a mong the 20 most common species unimodal
and町egul釘 diameterdistributions were twice as frequent as negative exponential distribu-
tions. Thed iameter distribution of Hopea odorata Roxb.，出especies with the grea旬stbasal
area on the plot，w as unimodal and approximately norma .lThese results suggest that the紅白
in and around the H郎 plotmay have b悶 su恥 tto aI 叩 -scalecatastrophic disturbance.
Key words: diameter distributions，d isturbances，H opea odorata，H uai Kha Khaeng，
permanent plot.
INTRODUCTION
Between 1992 and 1995 a large-scale pennanent forest dynamics plot (FDP) was
established in as easonal dry evergreen forest at the Huai Kha Khaeng Wildlife Sanctu紅y
(HKK)加westem百ailandto monitor long却 nnchanges in forest composition and s回 C制re.
In this paper wes ummarize the results from the first census describing the stand structure
at血eHKKF DP to answer two questions: (1) Is the forest of the HKKF DP representative
of seasonal evergreen forests of continental Southeast Asia? (2) 'Howd oes the structure of
'Silvicultural Research Division，Fo rest Research Office，R oyal Forest Department，C hatuchak.， Bangkok 10900
2Silviculture Laboratory，C ollege of Forest Resources，U niversity of Washington，Se attle，W A，U SA.
3Center for Tropical Forest Science，S mithsonian Tropical Research lnstitute，Ph ilippines
4H紅V紅dUniversity Herbaria，H arvard University，C ambridge，M A，U SA.
Reωived 25 Juary2001; accepted 12 June 2001.
飢
89
90 SARAYUDH BUNYAV日CHEWIN，PATRICK J. BAKER，JA MES V. LAFRANKIE，PE TER S. ASHTON
the seasonal dry evergreen forest differ from other lowland tropical forest types? and (3)
Is there evidence that the stand has experienced severe disturbance in the past?τbes加 ct町e
of this paper closely parallels MANOKORAN AND LAF'RANKlE (1990)，w hich describes由e
results of the first census from as imilar FDP in lowland evergreen forest of peninsul
釘
Malaysia. Weh ave chosen to adopt as imilar framework for describing the HKKf orest to
facilitate comparisons between these and other large-scale perm entplots (see CONDIT，
佃
1995). A companion paper will describe the floristic structure of the FDP.
SITE DESCRIPTION AND METHODS
百】estudy site is located in the Huai KhaK haeng Wildlife Sanctuary at 15040' N
latitude and 99010' El ongitude in Uthai Thani province，we st-centra1 τbailand，ap proximately
300 kmn orthwest of Bangkok (Fig. 1). Thes anctuary encompasses 2，780 km2o f the Huai
KhaK haeng River watershed. Thet opography consists of broad river va11eys and moderately
steep ridges running north-south. Thes anc旬釘ycontains am osaic of four forest types:
seasonal dry evergreen forest，m ixed deciduous forest，d ry dipterocarp forest，a nd hill
evergreen forest. The study site is located in an eaof seasonal dry evergreen forest.
釘
Elevation within the study plot ranges from 550 to 640 meters above sea leve .lMean
annua1 rainfall is 1，475 mm( 1983-1993). Thec limate is monsoonal with ar ainy season
from May to October and ad ry season from November to April (in which mean monthly
rainfa11is く100mm) (Fig. 2).百leextent and severity of the dry season is variable. Some
years have sporadic rainfall during出edry season; others have little or no rain for the entire
dry season. Mean July temperature is 2rc; mean January temperature is 190C. Minimum
recorded temperatur巴，S訂eas low as 120C and maximum temperatures as high as 380C.
Maximum daily relative humidity drops below 98% only during the height of the dry
season in March and Apri .lMinimum daily relative humidity varies between 40% and 60%
except during the dry season，w hen it is frequently less than 20%.
TheF DP is a5 0-ha rect gle1k m long (north-south axis) and 0.5 km wide (east-
叩
west). The enumeration included all仕切・standingwoody plants O!:1c m dbh. Each tree was
measured，m apped to plot coordinates，a nd identified following as tandard protocol
(MANOKORAN ETA L.，1 990; CONDIT，1 999; BUNYAV日CHEWINETA L.，20 00). All data are
stored in aM icrosoft Access database to facilitate data retrieval and manipulation. Taxonomy
and nomenclature follows BUNYAVEJCHEWIN ETA L. (2000).
RESULTS
Stand-wide Distribution Among Diameter Classes
τbe forest within the 50haplot had ar elatively low density with at otal of 80，640
・
trees or am ean density of 1，609 trees ha-1 (SD = 311.0) The mean density for trees
between 1a nd 2c m dbh was 434 ha-1( SD = 190.56). Between 1a nd 10 cm the mean
=
density was 1，171 ha-1( SD 299.0)，de creasing in al og-linear fashion through 1c m size
class intervals (Fig. 3). When compared to other 50 ha plots，th e HKKf orest has much
lower densities among the small size classes (Table 1).
STAND STRUCTURE OF A SEASONAL DRY EVERGREEN FOREST 91
20
16 16
6HK~~:~~AN0
ell
Q)
(f)
c
ell
12 E 12
ell
"'0
c
.::(
8
98 102 106
Figure l. Location of the Huai Kha Khaeng Wildlife Sanctuary, western Thailand.
400
350
300
.Es 250
=
200
~
c:
a":' 150
100
50
0
F M A M A s 0 N D
Month
Figure 2. Mean monthly rainfall conditions at the Huai Kha Khaeng WS, Thailand (Khao Nang Ram Wildlife
Research Station meteorological data; 1983-1993).
92 SARAYUDH BUNYAVEJCHEWIN，PA TRICK J. BAKER，JA MES v. LAFRANKIE，PE TER s. As町"ON
Mean density of trees 2:10 cm dbh was 438 ha-1( SD =6 1.3). The mean density of
trees注30cm dbh was 83 ha-1( SD = 18.1). The mean density of trees 2:100 cm dbh was
5.6 ha-1( SD =1 2.5). Mean density of trees classed in 10 cm intervals between 10 cm and
100 cm dbh decreased in al og-linear fashion (Fig. 4).
The family Annonaceae had the greatest number of stems 2:1c m dbh (16，663
individuals)，fo llowed closely by the Euphorbiaceae (14，595 individuals) and Sapindaceae
(9，823 individuals). Noo ther families had more than 5，000 stems (i.e.，m e densityof 100
如
ha斗).Because many of the genera at the HKK FDP have only one or two species，th e
pattems of abundance among the most populous genera and species are nearly identical.
百 us，Croton (Euphorbiaceae)，re presented by C. oblongifolius Roxb.叩 dC. hutchinsonianus
Hosseus，w as the most populous genus (9，153 individuals)，w ith C. oblongifolius being the
most common species (9，106 individuals). Polyalthia (Annonaceae) was the second most
populous genus (6，141 individuals) and Polyalthia viridis Craib was the second most
common species with 5，888 individuals. Table 2s ummarizes the distribution of stems
among the top 10 families，g enera，a nd species.
It is worth noting that the HKK plot contains some very large trees. Of the 26 trees
over 150 cm dbh，14 were Ficus species. Most of these were strangling (i.e.，he mi-epiphytic)
figs for which dbh measurements represent the total diameter of fig and host tree. The
remaining 12 trees 1紅gerthan 150 cm dbh were divided among 4s pecies: Aβelia砂locarpa
(Kurz) Craib，A nisoptera costata Korth.，H opeαodorata Roxb.，a nd Tetrameles nud抑ora
R.Br ex Benn.百lelargest tree (excluding strangling figs) was an Anisoptera costata with
ad bh of 206 cm. In comparison，th e Pasoh FDP had only 4t rees larger than 150 cm dbh
(MANOKORAN & LAFRANKlli，1 990).
Species-specific Diameter Distributions
Stand-wide diameter distributions provide ag eneral description of the stand's structure;
however，di ameter distributions of individual species c oftenprovide additional information
佃
about past influences on stand development such as disturbances. The tree species at the
HKKF DP exhibit ar ange of diameter distributions. The negative exponential distribution
that is predicted for self-replacing populations is not as common among the HKKs pecies
as expected. In fact，th e negative exponential distribution is found in only 6o f the 20 most
common species (ranging in abundance from 1，049 to 9，101 individuals); of the remainder，
8 species have unimodal distributions that are approximately normal (although often
positively skewed)，2 species have compound (or multimodal) distributions (i.e.，l arge
numbers of individuals in the smallest size class and au nimodal distribution describing the
remainder of the size classes)，a nd 4s pecies have maximum dbh 10cm and thus enot
く 訂
appropriate for comparison. The most notable species with au nimodal diameter distribution
is Hopea odorata，th e dominant canopy species.百lediameter distribution of Hopea odorata
is approximately normally distributed with am ean diameter of 71 cm (SD =3 8，n =330)
(Fig. 5). Other important canopy species exhibiting unimodal diameter distributions include
Alphonsea ventricosa Hk.f.& Th.，Du abanga grand伊'ora(Roxb. ex DC) Walp.，Dy soλylum
grande Hiem，a nd Litseαcambodiana H.Lec.
Another group of species with diameter distributions that may be indicative of historical
disturbance are those that are commonly associated with mixed deciduous or dry dipterocarp
forests (BUNYAV EJC田 WINET AL.， in press). Several traits suggest that many of these
STAND STRUCTURE OF A SEASONAL DRY EVERGREEN FOREST 93
Table 1. Comparison of tree densities above specified diameters from other large-scale
forest dynamics plots (i.e.，O!: 50 ha).
Plot Trees ha-1 Trees ha-1 Trees ha-1 Trees ha-1
注(1cm dbh) (O!:1O cm dbh) (O!:30 cm dbh) (O!:100 cm dbh)
Pasoh Forest， 6，769 530 75 1.6
Peninsular Malaysia
Lambir Hills NP， 6，687 622 117
Sarawak
Barro Colorado Island， 4，844 414 83 3.4
Panama
Huai KhaK haeng WS， 1，609 438 83 5.6
Thailand
Mudumalai WS， 328 255 103
India
Table 2. Densities of the 10 most populous families，ge nera，an d species at the 50haplot，
・
Huai Kha Khaeng WS，Th ailand.
Rank Family Density Genus Density Species Density
Annonaceae 16，663 Croton 9，153 Croton oblongifolius 9，106
(Euphorbiaceae) (Euphorbiaceae)
2 Euphorbiaceae 14，595 Polyalthia 6，111 POかalthiaviridis 5，888
(Annonaceae) (Annonaceae)
3 Sapindaceae 9823 Dimocarpus 5，501 Dimocarpus longan 5，501
(Sapindaceae) (Sapindaceae)
4 Rubiaceae 4，899 Orophea 4，379 Orophea polycarpa 4，379
(Annonaceae) (Annonaceae)
5 Lauraceae 4，574 Diospyros 4，159 Prismatomeris malayan 4，137
四
(Ebenaceae) (Rubiaceae)
6 Ebenaceae 4，159 Prismatomeris 4，137 Phoebe tovayana 3，018
(Rubiaceae) (Lauraceae)
7 Dipterocarpaceae 2，874 Phoebe 3，018 Baccaurea ram伊ora
(Laaceae) (Euphorbiacae)
町 哩
8 Rutaceae 2，776 Baccaurea 2，582 Arytera litoralis 2，539
(Euphorbiaceae) (Sapindaceae)
9 Leguminosae 2，539 Arytera 2，539 Mitrephora thorelii 2，248
(Sapindaceae) (Annonaceae)
10 Bignoniaceae 1，897 Mitrephora 2，248 Vatica cinerea 2，080
(Annonaceae) (Dipterocarpaceae)
94 SARAYUDH BUNYAVEJCHEWIN, PATRICK J. BAKER, JAMES V. LAFRANKIE, PETERS. ASHTON
1000
ra 100
.J:.
U!
-Cl>
.C..l>.
c:
ra
Cl>
:a: 10
<2 3 4 5 6 7 8 9 10
Diameter class
Figure 3. Density of trees 1 to 10 em dbh (I em intervals) in the 50-ha plot, Huai Kha Khaeng WS, Thailand.
10000
1000
ra
.J:.
U! 100
-Cl>
.C.l.>.
c:
ra 10
Cl>
:a:
0.1
v0 C0 \J 0C ') 10. 0 0c. o c0 o 00 ) 00 0 C0\ J C0 ') 0-.; ;t 10. 0 10. 0
'A
Diameter class
Figure 4. Density of trees in 10'cm size classes in the 50-ha plot, Huai Kha Khaeng WS, Thailand.
STAND STRUCTURE OF A SEASONAL DRY EVERGREEN FOREST 95
50
40
30
z
20
10
0
0v 0N 0C ') 0'< !" 0LO <0. o I0' - 0ro e0 n o0 0 N0 0C ') L0. {) (0( ) I0' -
Diameter Class (em)
Figure 5. Diameter distribution or f-lopea odorara (Dipterocarpaceae), the dominant tree species in the 50-ha
plot, 1-luai Kha Khaeng WS, Thailand.
species are relict populations within the matrix of the seasonal dry evergreen forest at the
HKK FOP: (1) small populations, (2) unimodal diameter distributions that are negatively
skewed, and (3) large mean diameters. Examples include Afzelia xylocarpa, Pterocarpus
macrocarpus Kurz, and Terminalia bellirica (Gaertn.) Roxb. (Fig. 6). Shorea siamensis
Mig., one of the dominant species of the deciduous dipterocarp forests, is represented by
a sole individual of 65 em dbh that has the gnarled and tumescent bole typically associated
with relict S. siamensis in dry dipterocarp stands elsewhere in the sanctuary (P.J. Baker,
unpublished data).
Stand-wide Distribution of Basal Area
Mean basal area of trees d em dbh was 30.39 m2 ha-1 (SO= 5.70). For trees ~10 em
dbh the mean basal area was 28.64 m2 ha-1 (SO = 5.70); for trees ~30 em dbh the mean
basal area was 20.33 m2 ha-1 (SO = 5.43); and, for trees dOO em dbh the mean basal area
was 5.57 m2 ha-1 (SO= 4.46). Basal area peaked in the 10-20 em size class and decreased
in a linear fashion among the larger size classes (Fig. 7).
Members of the family Oipterocarpaceae dominated the FOP with respect to basal
area. While they represented only 3.6% of the total number of stems in the FOP, the
dipterocarps accounted for 21.9% of the basal area (332.24 m2). (Table 3 summarizes the
distribution of basal area among the top 10 families, genera, and species.) A single species,
96 SARAYUDH BUNYAVEJCHEWIN, PATRICK J. BAKER, JAMES V. LAFRANKIE, PETERS. ASHTON
Afzelia xylocarpa
12
10
8
(a) z 6
4
2
0
<20 40 60 80 100 120 140 160 180 200 220
Diameter Class
Pterocarpus macroncarpus
6
5
4
(b) z 3
2
<20 40 60 80 100 120 140 160 180 200 220
Diameter Class
Terminalia bellirica
7
6
5
(c) 4
z
3
2
0
<20 40 60 80 100 120 140 160 180 200 220
Diameter Class
Figure 6. Diameter distributions of (a) Afzelia xylocarpa (Leguminosae), (b) Pterocarpus macrocarpus
(Leguminosae), and (c) Terminalia bellirica (Combretaceae), three species with irregular size dis
tributions dominated by large individuals, in the 50 ha plot, Huai Kha Khaeng WS, Thailand.
STAND STRUCTURE OF A SEASONAL DRY EVERGREEN FOREST 97
Hopea odorata (n = 330 individuals，or 0.41% of the total number of trees on the FDP)，
accounted for 169 m2 of basal ea(3.38 m2h a-1a nd 0.51 m2t ree-1)-11.1 % of the total
釘
basal area of the FDP. TheA nnonaceae had the second highest basal area among families
(292.22 m2h a-1)，fo llowed distantly by the Lauraceae (118.05 m2h a-1)a nd Euphorbiaceae
(83.94 m2h a-1); all three of these families were ranked in the top five families for total
number of individuals on the HKKF DP. The same pattem of similarity between genera
and species that occurred for stem density is found in the distribution of basal 'ea.The
紅
genus Hopea (Dipterocarpaceae)，r epresented by the s泊glespecies H. odorata，h ad the
greatest basal area (see above). Saccopetalum (Annonaceae)，al so represented by as ingle
species (S. lineatum Craib)，ha d the second greatest basal area (128.74 m2h a-1)a mong the
genera at the HKKF DP.
Heterogeneity
Thed i蛇 ibutionof stems and basal area was not uniform across the plot. Wed ivided
the plot into 1，250 20 x2 0mquadrats and calculated the density for each quadrat. The
・
density of stems (O!:1c m dbh) in the quadrats ranged from 11 to 249 trees; median density
was 58 tr< sand 50 percent of the quadrats had total stem densities between 45 and 77
田
(Fig. 8a). Thed istribution was not significantly different合'Oman ormal distribution (Shapiro
= ・
Wilk W 0.90，p < 0 .001; ZAR 1984)，al though it was strongly positively skewed (skewness
= 1.50). Variation in basal 'eaamong quadrats was similar (Fig. 8b); the distribution
釘
was normally distributed (ShapiroWilkW =0 .85，P < 0 .001)，al though strongly positively
= ・
skewed (skewness 2.25). Ther ange of basal紅'eawas 0.11 to 7.02 m2• 百le median basal
紅'eawas 1.09 m2 with 50% of the valu巴sfalling between 0.73佃 d1.53 m2•
Figure 9s hows the distribution of all trees注100cm dbh.τ'hen orthem half of the FDP
has greater proportion of these large trees. The two areas along the eastem and southeastem
edges of the plot出athave no large trees coη'espond to the top of hills，bo th of which are
covered with short dense thickets of bamboo and scrub forest.
百ledistribution ofthe smallest trees (1-2 cmd bh) is shown in Fig. 10. Thes mall tr<田S
are highly aggregated but well distributed across the plot. The southeastem comer of the
plot has the lowest density of small trees. This is most likely the consequence of af ire that
bumed through that p制 ofthe plot in 1992，ju st before the initial plot census began. Such
low-intensity surface fires typically result in widespread mortality of the smallest size
classes of trees (<5 cm dbh; P.J. Baker，u npublished data). Whilem any saplings in出e
seasonal evergreen killed by the frre subsequently re-sprout (S. Bunyavejchewin，un published
data)，f ew would have reached 1c m dbh sufficiently quickly to be included in出ecensus.
98 SARAYUDH 8UNYAYEJCHEWIN, PATRICK J. BAKER, JAMES V. LAFRANKJE, PETERS. ASHTON
5
4
.s0:1:
Cil
~ 3
01
"iii
01
.0 2
!:
01
::Q:;;l
Diameter class
Figure 7. Mean basal area of trees per hectare in the 50-ha plot, Huai Kha Khaeng WS, Thailand. (Note that
the size classes are uneven.)
300
250
200
(a) z 150
100
50
0
0m Nm m.,. <mD cmo 00
N
6 6 6 6 6 A
~ N :'! <D ~
Abundance class (Stems'quad)
250
200
(b) 150
z
100
50
0
"6N0 ' 1"0c''-i "N'7 ' "1.;'',- N"NN ' ""0N:' """c:!'', 1."c;-'',-; "".N.;' . 1."..;,,'.',.- "A'
c-;
0 N
Basal area class (BA/quad)
Figure 8. Density (a) and basal area (b) of 1250 20-m x 20-m quadrats within the 50-ha plot, Huai Kha
Khaeng WS, Thailand.