A JOURNAL ON TAXONOMIC BOTANY
PLANT SOCIOLOGY AND ECOLOGY

REINWARDTIA

Editors
SOEDARSONO RISWAN

MIEN A RIFAI
ELIZABETH A. WIDJAJA

Published by
HERBARIUM BOGORIENSE

BALAI PENELITIAN DAN PENGEMBANGAN BOTANI
PUSAT PENELITIAN DAN PENGEMBANGAN BIOLOGI — LIPI

BOGOR, INDONESIA

Reinwardtia Vol. 11, Part 1, 1 - 55 5 February 1992

IO ISSN 0034 - 365 X

REINWARDTIA

Vol. 11, Part 1, pp. 13 - 22 (1992)

FLORISTIC CHANGES IN A SUB—TROPICAL RAIN FOREST
SUCCESSION

ROCHADI ABDULHADI

"Herbarium Bogoriense", Puslitbang Biologi, Bogor

ABSTRACT

Floristic changes in a subtropical rain forest succession were assessed.
Three regrowth forests aged 20 years, 50 years and 60 years and an un-
disturbed forest were sampled. The series of sites show floristic changes
that would be expected in a successional sequence. The regrowth forests
were dominated by the secondary species but the primary species occur
from the early stage. The oldest regrowth (60 year-old site) was still well
short of regaining its original condition.

ABSTRAK

Perubahan flora pada suatu suksesi hutan subtropika basah ditelaah.
Tiga lokasi hutan sekunder berumur 20, 50 dan 60 tahun serta satu hutan
yang tidak terganggu dicuplik. Pada sederetan lokasi ini memperlihatkan
adanya perubahan flora sebagaimana dalam suatu rangkaian suksesi. Hutan-
hutan sekunder muda didominasi oleh jenis-jenis sekunder, tetapi jenis-
jenis hutan primer sudah hadir sejak awal suksesi. Hutan sekunder tertua
(60 tahun) rupanya masih memerlukan waktu yang panjang untuk men-
capai keadaan flora seperti sebelum terganggu.

INTRODUCTION

Many studies have been concerned with describing the composition
and structure of rain forests. These have usually emphasized trees with
the diameter at breast height (DBH) of 10 cm or more. Such studies have
shown a considerable variation in species composition among individual
stands of rain forest, associated with environmental gradients (Richards
1952, Baur 1964 and Whitmore 1975). However, comparatively few of such
studies have examined along the successional sequences.

The floristic composition of several sub-tropical rain forests assumed
to form a successional sequence is examined. This examines of how second-
ary species are replaced by primary forest species and how long the establ-
ishment of the primary forest species will take place.

14 REINWARDTIA [VOL. 11

STUDY AREA AND METHODS

The study area was in the vicinity of O'Reilly's Guest House in the
Lamington National Park (28°14'S, 153°7'E) Queensland. Rainfall in the
area is about 1 880 mm per year mostly falling in the summer months
between November—April. There are no temperature measurements available
for the area but the environment is probably similar to the nearby Tambo-
rine Mountain where the temperature range varies from a mean daily mi-
nimum of 8.3 °C in July to a mean daily maximum of 26.8° C in January.
The vegetation in the area has been mapped and described by McDonald &
Whiteman (1979) as a tall closed forest alliance dominated, above 800 m,
by a Caldcluvia paniculosa — Cryptocarya erythroxylon — Dysoxylum frase-
ranum association. According to Webb's classification (Webb 1968) this can
be described as a cool sub-tropical rain forest or complex notophyll vine
forest. A number of study sites were chosen in regrowth forests of different
ages (Figure 1) :

Site 1. Twenty year-old regrowth which has developed on abandoned
farmland. The original forest was probably burnt or partially burnt at the
time of clearing. The site is about 40 ha in area and 500 m wide at the nar-
rowest point. It is surrounded on three sides by intact forest and on fourth
by pasture. The elevation is about 860 m.

Site 2. Fifty-year-old regrowth which has developed after an attempt;
to clear the original forest failed. The forest was cleared and partially-
burnt but weeds colonized and regrowth prevented pasture establishment.
The area covers about 16 ha and is 400 m wide at its narrowest point. The
site is bounded on two sites by intact forest and by pasture and disturbed
forest on the other two sides. The elevation is 800 m.

Site 3. Sixty-year-old regrowth forest which has developed after the
original forest was cleared, burnt and converted to pasture for several years
before being abandoned. The area is about 16 ha and about 300 m wide at
its narrowest point. It is surrounded on three sides by intact forest and
bounded on fourth by road and repeatedly disturbed forest dominated by
Acacia melanoxylon. The elevation is 900 m.

Site 4. Undisturbed forest close to Site 1). The elevation is 860 m.
Five strip plots each 10 x 100 m were established in an undisturbed

forest as well as in the 20, 50 and 60 year-old regrowth forests (i.e. Sites 4, 1,
2 and 3). Each strip plot was then divided into 10 plots 10 x 10 m. Thus
50 plots, with a total area of 0.5 ha, were established at each site. Trees
with a DBH greater than 10 cm in each plot were recorded. The diameter
was measured using a diameter tape, about 1.3 m above the ground or 20 cm
above buttress. Specimens were collected for identification purpose and
voucher specimens were prepared.

1992] ROCHADI ABDULHADI : Floristic Changes in a Subtropical Forest 15

RESULTS

Compositional Changes

The number of species, genera and families of trees all tended to in-
crease with an increase in forest age (Table 1). The total number of species
in each 0.5 ha sample area ranged from 37 in the 20 year-old regrowth (Site
1) to 66 in the intact forest (Site 4). Similarly the number of families in-
creased from 19 to 25 respectively. In general the changes of species compo-
sition led to increase in species diversity and equitability, thus the Shannon
diversity index increased from 2.45 in Site 1 to 3.46 in Site 4, and the
equitability from 0.68 to 0.83.

Sorensen's similarity index, based on the species presence or absence,
and Motyka's similarity index, based on the individual number of plants of
each species in each site, both indicate similar trends (Table 2). The degree
of similarity between the various sites was low. However, both indices also
showed that with time the regrowth forest tended to become more similar to
the undisturbed forest. Thus Site 1 (20 year-old site) and Site 4 (undis-
turbed forest) had a Sorensen index of 33.01 while Site 3 (60 year-old re-
growth) and Site 4 had a Sorensen index of 49.60. Not surprisingly the
highest similarity index was between 50 and 60 year eld regrowth forests
(Sites 2 & 3).

In regard of the species functional group, most individual trees in the
youngest regrowth forest (Site 1) were early secondary species (91,9) %,
i.e., species that are short-lived, fast growing, intolerant of shade and regular-
ly produce large numbers of effectively dispersed seeds (Hopkins et al, 1977
& Shugart et al, 1980). The proportion of these declined dramatically
throughout succession. As Figure 2 shows, this decreased to 66 % and 11 %
in older regrowth forest (Site 3) and undisturbed forest (Site 4) respectively.
In contrast, the proportion of trees belonging to primary species (i.e. slow
growing and long-lived trees which are capable of germinating and establishing
in shade, and irregularly produced seeds that are usually less effectively
dispersed) increased from 6 % at the Site 1 to 84 % at Site 4. The late secon-
dary trees which are intermediate in most characteristics between early
and primary species, shows a different trend. The proportion increased from
4 % at Site 1 to 22 % at Site 3, but then declined to 9 % in undisturbed
forest.

Although tne proportion of individuals belonging to primary forest
species in the young regrowth forest was very low, the proportion of primary
forest species was similar to that of early secondary species i.e., 35 % and
45 % (Figure 2. B). The proportion of primary species increased slightly to
48 % in the 60 year-old regrowth, and then increased sharply to 71 % in the
undisturbed forest (Site 4). The proportion of early secondary species, how

1 6 REINWARDTIA [VOL. II

Table 1. Number of species, genera and families of trees in a series of regrowth and
undisturbed forests (based on 5 strip plots per site each of 10 x 100 m each).

Site
Age (years)

Number of species
Number of genera
Number of families
Shannon diversity indices
Shannon equitability indices

Table 2. Matrix of Sorensen

Site
Age (years)

1 (20 years)
2 (50 years)
3 (60 years)
4 (UF)

1
20

37
32
19

2.45
0.68

and Motyka' s

2
50

58
46
23

3.09
0.76

similarity indices

Sorensen's similarity

1
20

20.71
34.54
10.83

2
50

44.21

47.41
14.27.

3
60

55
46
23

2.98
0.74

3
60

50.00
60.18

16.65

4
UF

66
49
25

3.46
0.83

4
UF

33.01
48.16
49.59

Motyka's similarity

ever, declined to 29 % in the 60 year-old, then 11 % in the undisturbed
forest. The proportion of late secondary species at each site was intermedi-
ate between these two groups, increasing to a maximum of 30 % in the 60
year-old regrowth forest and then declining to 20 % in the undisturbed
forest.

These same trends are evident if one considers the identity of species
having the highest importance value at each site. As Table 3 shows, all the
species with importance value greater than 10 in the 20 and 50 year-old
regrowth forests were early secondary species. In a 60 year-old forest, of the
eight species with importance values greater than 10, five were early second-
ary species two were late secondary species (Decaspermum humile and Dys-
oxylum fraseranum) and one was primary species (Elattostachys nervosa).
Conversely, all of those important species in the undisturbed forest were
primary species except for Dendrocnide excelsa.

1992] ROCHADI ABDULHADI : Floristic Changes in a Subtropical Forest 17

Table 3, Rank of the most important species which have importance value greater
than 10.0

Forest age (years)

Rank 20 40 50 UF

1 Acacia melanoxylon Alphitonia excelsa Acronychia oblong- Argyrodendron tri-
ifolia foliolatum*

2 Euodia micrococca Polyscias elegans Alphitonia excelsa Pseudoweinmania
lachnocarpa *

2 Polyscias elegans Acronychia oblong- Polyscias elegans Streblus pendulinus
i folia

4 Dendrocnide excelsa Pentaceras australe Euodia micrococca Dendrocnide excelsa
5 Duboisia myoporoides Rhodomyrtus psi- Rhodomyrtus psi- Pseudocarpa nitidula*

dioides dioides
6 Alphitonia excelsa Acacia melanoxy- Decaspermum hu- Diospyrospentamera*

Ion mile**
7 Acronychia oblong- Euodia micrococca Dysoxylum frase- —

ifolia ranum** —

8 Elattostachys ner-
vosa*

Site

*
**
_
UF

Primary species
Late secondary species
I.V less than 10.0
Undisturbed forest

Population Changes of Particular Species

The number of important early secondary species such as Acacia mela-
noxylon, Alphitonia excelsa, Dendrocnide excelsa, Duboisia myoporoides,
Euodia micrococca and Polyscias elegans increased sharply in the first 20
years following the disturbance (Figure 3). Thereafter, some of these such as
Acacia melanoxylon, Duboisia myoporoides and Euodia micrococca dec-
reased. However, populations of Acronychia oblongifolia, Alphitonia excelsa,
Pentaceras australe, Polyscias elegans and Rhodomyrtus psidioides reached
the highest density in 50 and 60 year-old forest. In general, the early second-
ary species appeared to dominate the regrowth for up to about 60 years.

Late secondary species follow a similar pattern to these early secondary
species. But these species tend to establish and become more prevalent later.
Their populations were small in the 20 year-old forest.

18 REINWARDTIA [VOL. 11

The number of individuals of primary species in regrowth forests was
very small but increased sharply in the mature forest. Only one primary
forest species, Elattostachys nervosa, was numerous in 60 year-old regrowth
forest.

DISCUSSION

As might be expected in a series of forests differing mainly in age, the
number of species, genera and families present increased with time since dis-
turbance. Likewise, diversity also increased with forest age. 3y 60 years, the
regrowth forest had not acquired the species richness or diversity of the un-
disturbed forest. On the other the two similarity indices showed that the
regrowth forests were becoming increasingly like the undisturbed forest as
time passed by.

Early secondary species dominated the 20 year-old regrowth site
(Figure 2). The abundance of these species may be associated with the fact
that their seeds are widely dispersed or that they can be stored, remaining
dormant in the soil seed bank. Secondary trees often require at least 75%
of full sunlight for establishment (Unesco, 1978). Forest clearing, therefore,
allows those species to become established.

The length of time for which the secondary species persist at a site
seems to depend on their life spans. As Figure 2 shows, the population of
the more important secondary species increased then decreased with in-
creasing forest age. Species such as Acacia melanoxylon, Duboisia myopo-
roides and Euodia micrococca probably had a life span no longer than about
60 years since their number had decreased sharply by this age. Others such
as Alphitonia excelsa, Pentaceras australe and Polyscias elegans lived longer
but their population densities began to decline after 50 or 60 years. Acro-
nychia and Rhodomyrtus psidioides all had their highest population number
in the 60 year-old forest but were virtually absent from the undisturbed
forest. According to Shugart et al. (1980) these have a life span in the order
of 100 years, but Rhodomyrtus only about 55 years.

These data support the earlier conclusion by Hopkins et al. (1977) that
the life span of many secondary tree species in these subtropical rain forest
is less than 60 years. Likewise Riswan et al. (1987) noted a. similar longevity
for many secondary tropical species. Interestingly King & Chapman (1983)
found secondary species disappeared from logged forest in New South Wales
within 30 years. Presumably this is because only the shorter lived secondary
species had been able to invade the gaps left by logging.

The well known secondary species Dendrocnide excelsa, differed from
the other species since the population increased in undisturbed forest after
decreasing in older regrowth. As this species is an early secondary species, it
is thought to be intolerant of shade conditions under canopy. It is believed

1992] ROCHADI ABDULHADI : Floristic Changes in a Subtropical Forest 19

that this abundance is due to Dendrocnide invading gaps in the mature
forest, since it is very common in soil seed banks (Abdulhadi, 1989).

Despite sites is being colonized by the early secondary species, many of
the species characteristic of late and primary species also became established
soon after abandonment. It is well known that seeds of these species are
often of limited viability (Budowski, 1970; Shugart et al., 1980 and
Whitmore, 1984). Hence the occurence of these species in the youngest
regrowth forest may have been due to seed rain from nearby parent trees in
the undisturbed forest or to resprouting of suckers from persistant roots
(Webb et al, 1972 and Stacker, 1981).

Although the primary species were present in the young regrowth
forest, their individual numbers were small. In time however, populations of
primary species increased. The early occurence of primary species has also
been reported from regrowth forest elsewhere. Riswan et al. (1987) found
high numbers of these species (60% of all species) in 0.8 ha plot of 35 year-
old tropical rain forest regenerating on an area used for some years- as a
pepper plantation. This plot was close to an area of undisturbed primary
forest.

Assuming a uniform rate of change, an estimate of how long it takes
the number of primary species in this successional process to be established
or reach an equilibrium can be made by calculating the rate of influx of
these species (Riswan et al, 1987). Since the number of primary species in
the 20 and 50 year-old forests were 13 and 22 respectively, the rate of
influx of these species over the 30 years would be nine (i.e., 22 — 13)
species. To achieved 47 species (as found in undisturbed forest), would requi-
re an additional 25 (i.e., 47—22) species. Thus the period ro reach 47 species
would be 25 x 30/9 + 50 = 133 years.

Another way of estimating the time needed to reach maturity is to as-
sess the rate of change in the proportion of primary species. The proportion
of primary species in the 20, 50 year-old and undisturbed forests was 35, 38
and 71% respectively (Figure 2). Thus, the period to reach the 71% in the
mature phase would be (71-38) X [(50—20)/(38-35)] + 50 = 380 years."

These estimates are necessarily approximation. They make no allowance
for the different histories and areas of each site. They also assumed that the
rate at which primary species arrived and become established at a site remain
constant over time. However they are of the same order as other estimates
of the time required for recovery of primary forest. Thus Knight (1975)
concluded that after 120 — 150 years, one of his sites in Barro Colorado
Island was still not a climax. The similar estimation has also been noted by
Riswan et al. (1987). They suggested that for successful reestablishment of
a mixed dipterocarp forest be time required would be between 150 and
500 years.

2 6 REINWARDTIA [ V O L . 1 1

A C K N O W L E D G M E N T

This study has been funded by the University of Queensland and
Australian International Development Bureau. I am gratefully indebted to
Dr. David Lamb for supervising this study as well as for his criticism and
advise.

REFERENCES

ABDULHADI, R. 1989. Sub-tropical rain forest seed dynamics. PhD. thesis, Univ. of
Queensland.

BAUR, G.N. 1964. The ecological basis of rainforest management. Forest Commission of
NSW., Sydney.

BUDOWSKI, G. 1970. The distinction between old secondary and climax species in
Tropical Central American lowland forests. Trop. Ecol. 11 (1) : 44—48.

HOPKINS, MS., KIKKAWA, J., GRAHAM, AW., TRACEY, J.G. & WEBB, L.J. 1977. An ecologi-
cal basis for the management of rain forest. In Monroe, R. & Stevens, N.C. (eds.)
The border ranges, land use conflict in regional perspective, pp. 58 66.

KING, C.G. & CHAPMAN, W.S. 1983. Floristic composition and structure of a rainforest
area 25 yr after logging. Aust. J. Ecol. 8 : 415—423.

KNIGHT, D.H. 1976. A phytosociological analysis of species rich tropical rain forest oh
Barro Colorado Island, Panama, Ecol. Monogr. 45 : 259—284.

MCDONALD, W.J.F. & WHITEMAN, W.G. 1979. Moreton region vegetation map series :
Explanatory booklet for Murwilumbah sheet. Botany branch, Queensland Dept. of
Primary Industries, Brisbane.

MUELLER-DOMBOIS, D. & ELLENBERG, H. 1974. Aims and methods of vegetation ecology.
John Willey & Sons, New York.

RICHARDS, P.W. 1952. The tropical rain forest. University Press, Cambridge.
RISWAN, S., KENWORTHY, J.B. & KARTAWINATA, K. 1987. The estimation of temporal

processes in tropical rain forest : a study of primary mixed dipterocarp forest in
Indonesia. J. Trop. Ecol. 1 : 171-182.

SHUGART, H.H. Jr., HOPKINS, MS., BURGESS, LP. &MORTLOCK, A.T. 1980. The develop-
ment of successional model of subtropical rainforest and its application to assess
the effects of timber harvest at Wiangare State forest, New South Wales. J. Env.
Marag. 11 : 243—265.

STOCKER, G.C. 1981. Regeneration of North Queensland rain forest following clearing
and burning. Bio trop ica 13 (2) : 85—92.

UNESCO 1978. Tropical forest ecosystem. Nat. Resources Research XIV.
WEBB, L.J. 1968. General classification Australian rainforest. A istralian Plants. 9 : 349—

363.
WEBB, L.J., TRACEY, J.G. & WILLIAMS, W.T. 1972. Regeneration and pattern in the sub-

tropical rainforest. J. Ecol. 60 : 675—695.
WHITMORE, T.C. 1984. Tropical Rain Forest of the Far East. Clarendron Press, Oxford.

1992] ROCHADI ABDULHADI : Floristic Changes in a Subtropical Forest 2 1

Figure 1. Map showing the situation of the study area and location of the study sites.

22 REINWARDTIA [VOL. 11

Figure 2.

(B).

60 Mature
Years

The percentages of individual trees (A) and actual species (B) classed as early
species ( • ) , late secondary species (O) and primary species (•) in a regrowtn
forest series.

130-

100-

70-

40-

30-

20-

10-

Figure 3.

(C).

60 Mature
Years

Individual numbers of important species of early secondary species (A), late
secondary species (B) and primary species (C) per 0.5 ha in a regrowth
forest series. (A) : Am. A. melanoxylon, De. D. excelsa, Dm. D. myoporoides,
Em. E. micrococca, Pe. P. elegans, Ae. A. excelsa, Ao. A. oblongifolia, Pa. P.
australe., Rp. R. psidioides; (B) : Dh. D. humile, Df. D. fraseranum; (C) :
At. A. trifoliolatum, Dp. D. pentamera, En. E. nervosa, PL P. lachnocarpa
and Sb. S. pendulinus.

CONTENTS

Page

ROCHADI ABDULHADI Seed banks in a sub-tropical rain forest 1

ROCHADI ABDULHADI Floristic changes in a sub-tropical rain forest
succession 13

A.J.G.H. KOSTERMANS Two remarkable Lindera species (Lauraceae)
probably representing an undescribed genus 23

A.J.G.H. KOSTERMANS A new species of Diplodiscus Turcz. (Tiliaceae)
related to Brownlowia Roxb 27

N. SASIDHARAN & K. SWARUPANANDAN A new species of Cassine
(Celastraceae) from India , 29

A.J.G.H. KOSTERMANS Reinstatement of Pterocarpus echinata Pers.
(Leguminosae — Papilionaceae) ., 33

JUMAAT H ADAM & GC. WlLCOCK. A new natural hybrid of Nepenthes
from Mt. Kinabalu (Sabah) 35

A.J.G.H. KOSTERMANS Durio macrantha Kosterm. species nova (Bom-
bacaceae) from North Sumatra 41

A.J.G.H. KOSTERMANS Salacia acuminatissima Kosterm., spec. nov.
(Celastraceae) from Sri Lanka 53

A.J.G.H. KOSTERMANS Identity of Dracontomelum petelotii Tardleu
-Blot (Anacard.) 55

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