effects of selective logging on tree species … · hill dipterocarp forest of peninsular malaysia...

Journal of Tropical Forest Science 26(2): 188–202 (2014) Saiful I & Latiff A

188© Forest Research Institute Malaysia

EFFECTS OF SELECTIVE LOGGING ON TREE SPECIES COMPOSITION, RICHNESS AND DIVERSITY IN A HILL DIPTEROCARP FOREST IN MALAYSIA

I Saiful1 & Latiff A2

¹Forest Department Headquarters, Ban Bhaban, Agargaon, Dhaka, Bangladesh; [email protected]²Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Selangor Darul Ehsan, Malaysia

Received September 2012

SAIFUL I & LATIFF A. 2014. Effects of selective logging on tree species composition, richness and diversity in a hill dipterocarp forest in Malaysia. A systematic sampling along a gradient-directed transect was conducted in a primary hill dipterocarp rainforest in Peninsular Malaysia to study the effects of selective logging on tree species composition, richness and diversity. The area was surveyed for more than one year before it was logged. Six months to one year after logging, resurveying of the same plots was done. The extraction of 27 trees per hectare affected all diameter classes. Of the 47.0% of total injury, 40.1% of stems were totally destroyed and dead. Species richness and diversity showed significant variation from the original levels. A percentage of 24.1% of the total tree species were recorded lost from the study site in the first cut that encompassed only rare tree species and commercial timber trees. About 50% of the residual species were under very rare category with single stem. Logging also altered the species composition and species accumulation curve of all tree size classes. To arrest the loss of biodiversity, this study strongly suggests integration of biodiversity survey with the existing management system as well as careful planning and execution of improved logging practices.

Keywords: Before and after logging, Shannon index, Fisher’s alpha diversity index, Sorensen’s similarity index, rare, endemic

INTRODUCTION

Malaysia’s rainforest is one of the most species rich and biologically diverse ecosystems in the tropics with substantial number of endemic species (Ng et al. 1990, Whitmore 1990, Ali Budin & Salleh 1993, Bidin & Latiff 1995). There are at least 10,000 species of flowering plants in Malaysia, of which about 2830 are tree species from Peninsular Malaysia (Bidin & Latiff 1995). With regard to forest resources, Malaysia is still fortunate with high percentage of forest cover associated with high richness of tree flora. The total area of natural forests in Malaysia was about 19.26 million ha or 58.6% of the country’s total land area of 32.86 million ha (Anonymous 1992). However, there is growing concern over forest depletion and degradation and many species are known to be threatened with extinction. The country’s most biologically diverse dipterocarp forest which constitutes just over 85% of forested area in Malaysia (Salleh 1993) has largely suffered from uncontrolled logging which has a large impact on biodiversity. In fact, both conservation

and current style of timber exploitation are not suitable for managing Malaysian dipterocarp forests in terms of maintenance of structure, species composition and diversity (Wyatt-Smith 1987). Damage-controlled logging operations using traditional ground skidding system that allows the use of crawler tractors in the harvesting system operation (Pinard 1995, Shamsudin et al. 1999, Taumas 1999) have shown that the level of incidental damage, even after intensive harvesting, can be reduced by as much as half. Implementation of reduced impact logging (RIL) in Sabah could reduce logging damage by up to 50% compared with conventional logging but with increased cost (Taumas 1999). The impact of forest exploitation on population characteristics is well documented but little is known about the impact on biodiversity (Barbier et al. 1994). As such, the status of biological diversity in the country as well as the impacts of logging on biodiversity needs urgent attention (Salleh 1993, Salleh & Manokaran



1995). This is also because the efficiency of the existing Selective Management System (SMS) for managing Malayan hill dipterocarp forest (Wyatt-Smith 1988, Appanah & Weinland 1990) and its modification to accommodate biodiversity conservation requirements (Ashton 2008) are questionable. In fact, there is no evidence of long-term success of this management system (Whitmore 1984, 1990) and there is evidence of biodiversity decline after second and following cuts (IUCN 1992). Most studies were restricted to comparing logged forests with adjacent unlogged forests as opposed to before and after study of the same population or samples. Evaluation in such case may be confounded and valid changes are not so easily detected if there are differences in topography, soil, species composition and disturbance history between the unlogged (control) and logged forest (Cannon et al. 1998, Saiful 2002). As a result, it is difficult to exactly quantify how much of species diversity is lost as a result of destructive logging. However, it was concluded that with random destruction by logging, all rare species would be susceptible to depletion including highly valued timber species that were poorly represented even after low intensity logging (Johns 1992, Appanah 1999). On the other hand, logged forest may not always recover all species lost during logging and their species composition may be somewhat different (Johns 1992). Where small area is considered, tree species richness per unit area is generally slightly reduced as a result of logging (Skorupa 1986). He reported 6.6% reduction of species in the lightly-logged plots whereas in the heavily- logged plots mean number of species reduced to 28.9%. Similarly, both Shannon diversity index and Hills evenness measure also declined correspondingly in the lightly- and heavily-logged forests compared with unlogged site. This study was part of a larger study on effects of selective logging on tree species diversity, stand structure and physical environment of tropical hill dipterocarp forest of Peninsular Malaysia (Saiful 2002). The objective of this research was to evaluate the effects of selective logging on tree species composition, richness and diversity by examining the before-and-after-logging study of the same samples in a primary mixed hill dipterocarp forest.

MATERIALS AND METHODS

Study area

The study was conducted in the Sungai Weng Catchment of Ulu Muda Forest Reserve, Kedah, Peninsular Malaysia (5° 50' N, 100° 55' E). The study area (Figures 1 and 2) is located at about 40 km north-east of Baling, Kedah, bordering Thailand. The elevation of the study area ranges from 340 to 600 m above sea level (Saiful 2002). The study area is characterised by hilly and undulating terrain with moderately steep to very steep slopes (up to 45°). The vegetation is primarily hill dipterocarp forest (Whitmore 1984) and classified within the lowland evergreen rainforest formation. The forest is characterised by high density of small- and medium-sized trees with big emergents mostly of dipterocarp species. The ground layer vegetation consists of common herbs, shrubs, creepers and bertam palms (Eugeissona tristis). Bamboo is best represented in hillsides as well as along stream banks. The climate of the study area is uniformly hot averaging about 25 °C with ample rainfall almost throughout the year. The mean annual rainfall for from 1996 till 1998 averaged 2869 mm. The study site is unique with regard to perennial stream flows. The parent material is predominantly made up of quartzite and sandstone (RRIM 1988) giving rise to clayey and sandy texture. The soil is strongly acidic with pH ranging from 3.2 to 4.5. Within the study area, the soil type is also classified as Baling and Tai Tak series (DOA 1994) which is yellowish brown in colour, and finely textured and well drained.

Field survey

The study area, covering 45 ha consisted of adjacent stands or hills 1, 2 and 3 (Figure 3), was surveyed before it was logged. After 6 months to 1 year of logging, resurveying of the same study plots was done. A systematic sampling along the gradient-directed transect (Gillison & Brewer 1985, Austin & Hyeligers 1989, Kent & Coker 1992) was used in the biodiversity survey. The study site was stratified into four topographic locations such as streamside, ridge, ridge-top and hillside. Sampling was not done separately on each location but all topographic



locations were systematically covered by laying out transects. Within a forest stand (i.e. hill), a line transect was laid out originating from the stream bank, following the centre of the ridge and finally ending at the ridge crest (Figure 3). Transect line was never laid out across ridges or valleys to avoid periodic trends of capturing same habitat type. Without having periodic trends, systematic sampling can often be applied and the resulting data treated as random sampling data without bias (Krebs 1989). A survey of 60 tropical countries also indicated that systematic sampling with either fixed-area plot or strip lines is the most favoured method used to inventorise tropical mixed moist forest (Wood 1990). Lateral transects were established at right angle to the main transect to sample hillsides and spaced systematically at 40-m distance. These lateral transects were positioned alternately on

either side of the main transect and distantly spaced from each other (Figure 4). Study plots were also established at 40-m distance on the transect line. In the case of hillside, every first plot was positioned after 20-m distance from the edge of the ridge plot to distinguish two different habitat types (i.e. ridge and hillside). The rest of the plots were sited at 40-m distance along the transect (Figure 4). Depending on the structure of a terrain (i.e. flat or narrow ridge), plots of 30 m × 30 m or 20 m × 45 m were found to be manageable for recording necessary biological parameters. Trees of ≥ 20 cm diameter at breast height (dbh) were measured within the main plot of 30 m × 30 m or 20 m × 45 m size and three kinds of nested subplots such as 10 m × 10 m, 5 m × 5 m and 2 m × 2 m were distributed inside the main plot for poles (5 to < 20 cm dbh), saplings (1.5 m height, < 5.0 cm dbh) and

Figure 1 Topographic map (1: 50,000) of Ulu Muda Forest Reserve, Kedah showing location of study area and compartments

Compartment boundaryInternational boundary

StreamN

Study area

ULU MUDA FOREST RESERVE



Figure 2 Map of Peninsular Malaysia showing the study location

Figure 3 Topography of the study area showing direction of survey transects (indicated by arrow) following elevation gradient; lateral transects on hillsides are not shown; stands 1, 2 and 3 are selectively logged covering 45 ha; stands 4 and 5 are outside the study area

Area—100 ha

Stream

Scale0 100 200

N

Malacca



seedlings (10 cm to < 1.5 m tall) respectively. The details of the plot design are shown in Figure 5.

Data collection

Diameter at breast height of all trees according to the diameter class selected for different plot sizes was measured with a diameter tape at 1.3 m above ground level or just above the buttress. Each tree sampled was tagged and given a unique identification code. Ground positions of individual trees according to diameter class were mapped. Voucher specimens were oven dried and separated into families and genera, and identified up to species level using keys and descriptions on Malaysian flora (Whitmore 1972, 1973, Ng 1978, 1989). Specimens were verified by comparing with collections at the herbarium of the Forest Research Institute Malaysia (FRIM). Post-logging measurement did not include new recruitment following logging, i.e. enumeration was conducted directly on the initial population to detect the effects of selective logging. Using the same compass bearing of pre-logging survey, the directions of each transect line, plot position and plot boundary were relocated. Based on the tree location map prepared before logging, tree measurements (dbh) of all residual trees for

different diameter classes were taken to relocate the trees. The presence or absence of a tree as per original tree position map was noted. For presence, soundness (i.e. no injury) and type of injury were noted as per damage assessment classification described by Johns et al. (1996) and Saiful (2002). Methods of logging

The minimum cutting limit for the selective logging operation had been prescribed as 55 cm dbh for non-dipterocarp and 65 dbh for dipterocarp species. Trees were marked with consecutive numbers using yellow plastic tags. Tree felling was done by a power saw. Felling was mostly controlled and carried out along or across skid tracks for the advantage of transportation. The loggers engaged bulldozers for construction of roads, skid tracks and log landings as well as to get timber out of the stump site by winch system attached to it. The overall harvest level was 27 trees ha-1 with basal area and volume removal of 19.39 m² and 73.7 m³ ha-1 respectively.

Intensity of sampling

The intensity of sampling (i.e. number of sample required) within the 45 ha study site

Figure 4 Schematic diagram showing laying out of main and lateral transects and positioning of plots within a forest stand; lateral transects are positioned alternately on either side of the main transect and distantly spaced from each other with study plots also regularly spaced

Hillside

Stream Main transect line

Stream plot Ridge plot

Hillside

40 mLateral transect line

Ridge plot20 m

Hillside plots

40 m Plot at ridgetop



was examined based on number of species and diversity index (Figure 6). All three size classes of trees showed gradual decline in fluctuation in mean values of number of species and Shannon diversity index with cumulative number of study plots indicating minimum required sample size for the study site. This travelling mean or performance curve is considered as analogous to a species area curve (Brower et al. 1990) but plots a cumulative mean rather than the cumulative number of species. To obtain desired level of precision of survey estimates, calculation of standard error (%) of the sample mean on Shannon index values was also done and found within the acceptable limit, i.e. 5.6, 4.2 and 2.5% for saplings, poles and timber trees respectively.

Data analysis

The underlying distribution of dataset was examined using histogram to distinguish symmetrical from skewed distribution. Spearman’s rank correlation was used to determine the relationship between the two sets of variables before and after logging. The mean comparison of the variables (e.g. species per plot) before and after logging for different tree size classes was determined using one sample t-test, and for non-normal data, non-parametric Wilcoxon

signed rank test. Statistical significance level was established at p < 0.05. Analysis was performed with the Minitab (Release 10 for Windows) statistical package. The total count of species, based on the number of species per unit number of stems, was used to indicate species richness before and after selective logging. Species diversity indices, namely, Fisher’s alpha (Fisher et al. 1943) and Shannon’s were used to compare diversity of before and after logging relative to different strata. Fisher’s alpha diversity index is considered as a satisfactory measure of diversity which is not unduly influenced by small and varying sample sizes (Magurran 1988). Sorensen’s index of similarity was adopted to detect pattern of similarity or dissimilarity in species composition between different tree size classes affected by logging.

RESULTS AND DISCUSSION

Taxonomic composition

A summary of taxonomic composition of trees 1.5 m height and above affected by the selective logging operation is shown in Table 1. A total of 49 families, 136 genera, 270 species and 949 individuals were enumerated before logging.

Figure 5 Schematic diagrams of plot design showing different shapes and sizes of plots for enumeration of various tree size classes

Transect line Plot

40 m

30 m 20 m

45 m

10 m × 10 m

10 m × 10 m

5 m × 5 m

2 m × 2 m

5 m × 5 m

2 m × 2 m



Figure 6 Construction of diversity curve showing substantial decrease in fluctuations of mean values of Shannon index with the cumulative number of study plots indicating minimum number of samples required for all tree size classes

28

3

2.5

2

1.5

1

0.5

0

Mea

n va

lue

of S

hann

on in

dex

2 4 6 8 10 12 14 16 18 20 22 24 26

Cumulative number of samples

Sapling

Pole

Timber

Table 1 Summary of taxonomic composition of trees 1.5 m height and above affected by the selective logging operation in the 45 ha study site, Ulu Muda Forest Reserve, Kedah

Family Genus Species No. stems Family Genus Species No. stems

B A B A B A B A B A B AAlangiaceae 1 1 1 1 4 2 Myristicaceae 4 4 13 9 30 16Anacardiaceae 7 5 9 5 26 11 Myrsinaceae 1 1 2 2 3 3Annonaceae 8 7 14 12 52 29 Myrtaceae 2 1 15 13 42 25Apocynaceae 2 2 2 2 3 3 Ochnaceae 2 0 2 0 2 0Bombacaceae 2 1 2 1 5 3 Olacaceae 3 3 3 3 40 31Burseraceae 3 3 13 10 49 24 Podocarpaceae 1 1 1 1 3 1Cornaceae 1 1 1 1 2 1 Polygalaceae 1 1 5 3 22 12Dilleniaceae 1 1 1 1 2 1 Proteaceae 1 0 1 0 1 0Dipterocarpaceae 3 3 9 8 72 27 Rhizophoraceae 1 0 2 0 3 0Ebenaceae 1 1 3 2 6 3 Rosaceae 2 2 3 3 3 3Elaeocarpaceae 1 1 7 3 8 3 Rubiaceae 10 8 11 9 34 17Euphorbiaceae 13 12 24 20 116 73 Rutaceae 1 1 1 1 1 1Fagaceae 2 2 8 6 20 12 Sapindaceae 4 4 8 8 22 14Flacourtiaceae 3 3 3 3 8 5 Sapotaceae 3 3 7 6 53 27Guttiferae 4 4 13 12 52 25 Simaroubaceae 1 1 1 1 4 1Icacinaceae 1 0 1 0 1 0 Sterculiaceae 3 3 3 3 13 8Lauraceae 10 10 22 16 42 24 Styracaceae 1 1 1 1 4 3Lecythidaceae 1 1 2 1 6 1 Symplocaceae 1 1 2 1 4 2Leguminosae 8 5 10 5 61 26 Thymeleaceae 1 1 2 1 16 3Linaceae 2 2 2 2 10 5 Tiliaceae 2 1 2 1 6 4Loganiaceae 1 0 1 0 1 0 Trigoniaceae 1 0 1 0 4 0Magnoliaceae 1 1 1 1 3 1 Ulmaceae 1 1 3 3 12 3Melastomataceae 2 2 6 5 17 7 Verbenaceae 2 1 2 1 6 4Meliaceae 6 4 17 14 45 27 Violaceae 1 1 1 1 2 2Moraceae 2 2 6 3 8 3 Total B 49, A 43 136 114 270 205 949 496

Families with 1–2 species and < 5 stems were considered as rare; A = after logging, B = before logging



After logging, there were reductions in all these taxonomic compositions across all size classes of trees. Logging caused 12.2, 16.2, 24.1 and 47.7% reduction in the number of families, genera, species and individuals respectively from the original level. The family dominance was predominantly attributed to 10 large or commonest families based on the number of species and individuals (Table 1). In the top 10 families by species, selective logging did not cause any major change in the original hierarchy but targeted the family dominance by individuals with different ranking (Table 1). Euphorbiaceae was not only dominated before logging by 24 species and 116 trees but also maintained the dominant position with 20 species and 73 trees after logging (Table 1). On the other hand, though logging removed many dipterocarp stems and caused the family to move down from its original position in the top 10 list in the overstorey canopy, Dipterocarpaceae was among the most abundant families (Saiful 2002). In general, selective logging did not cause any change in the contribution of dominant families, and more than 50% of the total species richness and individuals recorded was contributed by dominant families in the logged forest. The effect of logging on the abundance of different families was also essentially random, as indicated by significant correlation (Spearman’s rank correlation: rs = 0.928, n = 43, p < 0.01) between the abundance of the families before and after logging (results not shown) and the finding was consistent with another study from Pahang, Peninsular Malaysia (Johns 1988).

Species abundance and dominance

With 84.1% rarity (species with 1–5 stems) before logging, selective logging affected the residual stand by increasing rare species to 92.7% (results not shown). On the other hand, a total of 105 species (or 38.9%) with single stem were recorded before logging but after logging rarity attained 48.8% with single stem (results not shown). This meant that about 50% of the residual species were under very rare category in the logged-over forest. The increase in rarity was due to the fact that some species were newly added in the rare category by reduction of individuals. With regard to species dominance, there were seven most abundant species under common and very common category (Table 2). Except for Ochanostachys amentacea, the rest of the species lost their original status due to decline in abundance caused by logging. Shorea curtisii, the second most abundant species with 30 stems, moved to the occasional category, most of which were heavily logged than damaged by logging. Despite severe reduction in density, none of the species from very common or frequent status were lost from the study site.

Rare and endemic species

Out of a total of 227 (84.1%) rare species with 1–5 individuals before logging, 65 species were lost from the study plots due to severe logging damage (smashed/uprooted/dead) (results not shown). None of the 65 species (except one, Carallia euryoides, Rhizophoraceae) was listed as endemic from Peninsular Malaysia. As logging

Table 2 Changes in the species dominance before and after logging in the study site

Before logging After logging

Dominant species Family No. stems Status No. stems Status

Ochanostachys amentacea Olacaceae 38 Very common 29 Very common

Shorea curtisii Dipterocarpaceae 30 Very common 9 Occasional

Palaquium herveyi Sapotaceae 27 Very common 15 Frequent

Archidendron bubalinum Leguminosae 23 Very common 11 Frequent

Monocarpia marginalis Annonaceae 20 Common 11 Frequent

Epiprinus malayanus Euphorbiaceae 20 Common 12 Frequent

Aporusa falcifera Euphorbiaceae 16 Common 13 Frequent

Tree species from 1.5 m height and above are ranked in declining order of abundance; very common = > 20, common = 16–20, frequent = 11–15, occasional = 6–10 and rare = 1–5 stems



damage was essentially random, and more or less all study plots and tree taxa were affected, it was quite natural that rare species were always at risk at being eradicated by destructive logging operation. It should be mentioned here that many rare species defined in this study were also found rare (1–5 individuals) in the overall study site comprising 150 ha of concession area with sampled area of 5.85 ha. This overall study surveyed 2624 individuals with 57 families and 421 species (Saiful 2002). Within this 150 ha, only 45 ha were selected for before-and-after-logging study. In fact, many study plots were different in species composition and in many cases every second individual was also a different species. Of the 43 families remaining after logging, a total of 31 families had lost species including commercia l ly important famil ies (e .g . Anacardiaceae, Leguminosae, Dipterocarpaceae). However, 44% (48 trees) of the total stems belonging to those 65 species lost were represented by ≥ 20 cm diameter and 33% (16 trees) of them were commercially logged. This meant that a number of commercial trees of > 20 cm diameter had been lost for the next cut. This could have far-reaching implications on the management system. The susceptibility of rare species to depletion including highly-valued timber species was also recognised (Johns 1992, Appanah 1999). Apart from being potential trees for timber, trees used regularly as food source were also severely affected by logging. Three species, namely, Ficus cucurbitina, Parkia speciosa and Sindora coriacea were lost from the study plots.

Among the new records of species from the study site (Saiful 2002), a total of 10 species such as Drypetes kikir (Euphorbiaceae), Calophyllum incrassatum (Guttiferae), Beilschmiedia madang (Lauraceae), Litsea firma (Lauraceae), Litsea tomentosa (Lauraceae), F. cucurbitina (Moraceae), Xanthophyllum vitellinum (Polygalaceae), Carallia euryoides (Rhizophoraceae), Palaquium ridleyi (Sapotaceae) and Symplocos celastrifolia (Symplocaceae) were also in the list of rare species lost from the sampling site. This implies that many species before knowing their existence and status have been lost from the ecosystem as a result of destructive logging.

Species richness and diversity

A high value of Shannon H' indicates a large number of species with similar abundances; a low value indicates domination by a few species. The effects of logging on species richness and diversity for each size class are summarised in Table 3. Conventional logging drastically reduced the number of tree species from a total of 270 to 205 species, i.e. 24.1% reduction from the original level. The total number of species in all size classes declined after logging and for all trees ≥ 20 cm dbh (i.e. timber trees for next cut), richness fell by 24.7%. In terms of 1 year after logging, Cannon et al. (1998) reported 31% reduction in number of species for trees > 20 cm diameter by comparing logged plots with the adjacent unlogged forest. At each size class level, selective logging reduced the

Table 3 Effects of logging on number of tree species and diversity indices for trees 1.5 m height and above at Ulu Muda Forest Reserve, Kedah

Parameter Status Tree size class

Sapling Pole Timber All combined

Total area surveyed (m²) 675.0 2800 22,500 –

No. of species Before logging 121 130 166 270

After logging 74 (38.8) 88 (32.3) 125 (24.7) 205 (24.1)

No. of stems Before logging 249 247 453 949

After logging 114 137 249 496 (47.7)

Fisher’s a Before logging 94.45 113.10 96.10 124.50

After logging 91.40 105.05 52.05 129.47

Shannon H' Before logging 4.56 4.63 4.52 3.72

After logging 4.16 4.27 4.42 4.87

Figure in parentheses are percentage reduction from the original level; sapling = 1.5 m height, < 5 cm dbh; pole = 5 to < 20 cm dbh; timber = ≥ 20 cm dbh; dbh = diameter at breast height



diversity indices (Table 3). However, across the all size class, diversity increased after logging. The overall increase in diversity in the residual stand within 1 year after logging could be due to reduction of species dominance and increased evenness of species abundance. Apart from the estimated species richness, the difference in plot means (species per plot) before and after logging was also highly significant as revealed by one sample t-test (Table 4) for sapling, pole and timber. Shannon index of diversity did not show normality for poles and timber trees but plot data of saplings were normally distributed. Hence, plot data on Shannon diversity index for tree size classes showed significant difference using one sample t-test for saplings and one sample Wilcoxon signed rank test for poles and timber trees (Table 4).

Species accumulation curve

The effect of selective logging on the pattern of species accumulation for three different size classes of trees is shown in Figure 7. In both saplings and poles, curves fell well below the before logging with irregular patterns in species accumulation. No substantial increase of species accumulation was observed due to heavy logging damage in compartment 29 up to 14 plots. However, after that, the curves continued to rise quite steeply in the moderately damaged compartment 28. In contrast, in the case of timber trees ≥ 20 cm dbh, the curve of after logging was not far below that of before logging and maintained almost similar slope (Figure 7). However, strong conformity exists in terms of

negative effect of logging between Cannon et al.’s (1998) study and this study. After 1 year of logging and in 8-year-old logged forest, Cannon et al. (1998) found that species–area curve was far below the unlogged forest for > 20 cm dbh trees. A different trend in species–area curve was demonstrated by Norhayati (2001) in which logged forest was richer than unlogged primary forest after 10 years of logging, and in this study pioneer species contributed about 9% of the total species in logged forest. However, Queensland studies (Nicholson et al. 1988, Crome et al. 1992), particularly after introduction of new strict silvicultural rules in 1982 (Whitmore 1990), showed minimum damage to residual stand and did not result in the loss of any tree species nor was there any change in the total plant species list after logging. Species similarity and composition

The effects of selective logging on tree species composition between tree size classes were measured by Sorensen’s index of similarity. Logging altered the species similarity between these size classes. Among the diameter classes, saplings and poles showed highest similarity (Cs = 0.49) in species composition before logging (Table 5). However, after logging, poles and timber trees had a relatively high species similarity (Cs = 0.38) than other combinations. On the other hand, hillside and ridge recorded the highest index value (Cs = 0.51) with 83 species in common before logging. However, logging did not cause any major change in species similarity between these two topographic locations compared with others (i.e. hillside vs ridge top or ridge vs ridge top).

Table 4 Test statistics of plot means and median on species richness and Shannon diversity index for different diameter classes of trees affected by selective logging

Parameter Size class Item of estimate

Before logging

After logging Sample size

T value Wilcoxon statistic

No. of species per plot Sapling Mean 7.78 (0.93) 4.07 (0.91) 27 2.86** –

Pole Mean 7.75 (0.59) 4.46 (0.63) 28 4.29*** –

Timber Mean 14.68 (0.87) 8.48 (0.76) 25 7.1*** –

Shannon H' Sapling Mean 1.91 (0.107) 0.92 (0.186) 27 5.44*** –

Pole Median 1.93 1.48 28 – 152***

Timber Median 2.63 2.08 25 – 324***

Standard errors in parentheses



Figure 7 Species accumulation curve for three different tree size classes showing pattern of species accumulation after selective logging

140

120

100

80

60

40

20

0

Cum

ulat

ive

num

ber o

f spe

cies

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29


Pole (before logging)

Pole (after logging)

140

120

100

80

60

40

20

0

Cum

ulat

ive

num

ber o

f spe

cies

1 4 7 10 13 16 19 22 25 28


180160140120100

80604020

0

Cum

ulat

ive

num

ber o

f spe

cies

Sapling (before logging)

Sapling (after logging)


Timber (before logging)

Timber (after logging)

1 3 5 7 9 11 13 15 17 19 21 23 25

Table 5 Changes in species composition by selective logging measured by Sorensen’s index of similarity

Tree size class Before logging After logging Species common Sorensen Cs Species common Sorensen Cs

Sapling vs. pole 62 0.49 27 0.33Sapling vs. timber 57 0.40 29 0.29Pole vs. timber 66 0.45 40 0.38Hillside vs. ridge 83 0.51 47 0.41Hillside vs. ridge top 62 0.48 24 0.29Ridge vs. ridge top 66 0.47 31 0.34



The overall changes in similarity at size class level due to logging might be associated with further changes in species composition by invasion of pioneer species due to opening up of canopy and soil degradation (Pinard et al. 1996). In South-East Asia, the invasion of some members of the family Euphorbiaceae (e.g. Macaranga, Mallotus spp.) in logged-over forest is well documented (Cannon et al. 1998, Johns 1988). At Danum, Sabah, pioneer species alone contributed 9% of the total species in 10-year-old logged forest (Norhayati 2001). In the study site, although these pioneers existed before logging, their abundance was quite insignificant. However, with habitat alteration, these pioneers started to occupy the canopy open areas in a bigger scale. Interestingly, one particular pioneer species (Trema angustifolia, Ulmaceae) was predominant in the heavily-damaged compartment 29, which was not observed or recorded before logging, whereas in the lightly-damaged compartment 28, members of the genus Macaranga were quite frequent.

Comparison with other studies

There are some limitations in comparative studies due to differences in the method of study, number of years after logging, sample size, siting of plots and diameter class of trees. Considering all these limitations, comparison must be made to detect

the overall positive or negative effects of logging. Similar to this study, in terms of 1 year after logging and matching with the diameter class and plot size used but comparing logged plots with adjacent unlogged forest, Cannon et al. (1998) reported 31% reduction in the number of species using 0.1 ha size plots for trees > 20 cm diameter. However, this study recorded 42% reduction in species richness using plots of 0.09 ha in size for similar diameter class. A study by Cannon et al. (1998) showed that per plot species richness was quite low even after 8 years of logging. Based on comparison by number of species per unit number of stems (Table 6), except for Norhayati (2001), the overall negative effect of logging was evident. For example, Kartawinata et al. (1981) from Indonesia compared primary forest plots with that of 30-year-old secondary forest and found similar trend in which there was reduction of 43% at species level though plot size was distinctly different between primary and secondary forests (i.e. 1.6 and 0.3 ha respectively). Comparison based on intensity of logging showed reduction in the number of species and Shannon diversity index. A study by Skorupa (1986), which was based on means found in 100 stems sampled, showed 6.3% reduction of species in lightly-logged plots whereas in heavily-logged plots, mean number of species reduced to 28.6%. Similarly, Shannon diversity index

Table 6 Comparison based on number of species per unit number of stems

Study Area (ha) Years after logging Dbh (cm) No. of species Shannon H'This study Before logging After logging

2.252.25

1 ≥ 20 166 125

4.52 4.42

Norhayati (2001) PF LF

1.01.0

10≥ 10

108 134

4.16 4.49

Abdulhadi et al. (1981) PF LF

1.62.0

6 months ≥ 10 205 159

–

Kartawinata et al. (1981) PF LF

1.60.3

30 ≥ 10209119

–

Hussin 1994 PF LF

4.0 4.0

– ≥ 15 291 274

–

Burghouts et al. (1994) PF LF

4.02.5

– ≥ 10267218

–

PF = primary forest, LF = logged forest; Dbh = diameter at breast height



also declined correspondingly in lightly- and heavily-logged forests compared with unlogged site. However, in the present study for trees ≥ 20 cm diameter, 30% reduction in species richness was recorded in the lightly-logged compartment, while in the heavily-logged compartment, reduction was much higher, i.e. 57.5% (results not shown). Similarly, this study has also shown 12.6% reduction in Shannon diversity index in the lightly-logged compartment while in the heavily-logged compartment, index reduced to 36.1%. In the study site, compartment 29 was heavily damaged resulting in 43% canopy opening as compared with 22% in the lightly-damaged compartment 28 although there was no significant difference in harvesting intensities (i.e. number of trees or volume felled) between these compartments. CONCLUSIONS

The study site was conventionally logged with selective cutting of few large commercially important trees. A mechanical system of logging using heavy bulldozers was employed. With high intensity of logging tracks and high felling damage, the selective logging affected all diameter classes and habitat types. As such the damage caused by harvesting layout and felling to the residuals not only altered the taxonomic composition but also aided drastic reduction in the number of species and diversity. Due to before-and-after-logging study of the same population, the effects of logging on reduction of species and diversity had been precisely quantified, which in many studies was confounded due to methodological limitations. The recovery of original species lost or variously injured during logging including highly-valued timber species may either be delayed or may not regain fully depending on the intensity of the damage done by logging. Further, recovery also largely depended on the resilience of the residual species and their competition with the pioneers. The degree of soil compaction, canopy disturbance and isolation from seed source were among the most limiting factors for the recovery of original composition. However, extremely rare species and particularly those that were specialised for a particular habitat (such as ridge top) might likely never recover in the heavily-damaged logged area. Ultimately, the taxonomic composition of the residual stand

might be somewhat different from primary forest conditions. Moreover, availability of required number of economically important trees for the next cut would also be difficult (Saiful 2002). The paper suggests that to minimise biodiversity loss, there is necessity for intervention not only in the extraction operation but also in the management system that should be compatible with biodiversity conservation. In other words, sustainable forest management system necessarily includes measures for conservation and these measures must be adopted at an early stage of forestry operations. The loss of rare species including commercially valuable species from the study site should be a concern for the management to adopt improved logging practices. Only if adequate baseline data on immediate and long-term effects of logging are available, then silvicultural prescriptions as well as environmental guidelines for logging operation can be formulated. However, the present comparative study from the same samples before and after felling in a primary forest can be useful to formulate ad hoc prescriptions for biodiversity conservation in timber producing areas. For sustainable forest management, one of the important measures could be integration of biodiversity survey in the existing management system. ACKNOWLEDGEMENTS

We appreciate the financial assistance of IRPA (Intensification of Research in Priority Areas) Project Grant No. 08-02-02-0009 and the cooperation received from the State Forestry Department, Kedah, Malaysia for the study. The field staff of Forest Range Office at Baling, Kedah is greatly acknowledged. Thanks are due to the director and curator in charge of the herbarium of FRIM for permission to examine voucher specimens. Thanks are also due to I Ahmed Zainuddin of Universiti Kebangsaan Malaysia for his assistance during data collection.

REFERENCES

AbdulhAdi R, KARtAwinAtA K & SuKARdjo S. 1981. Effects of mechanized logging in the lowland dipterocarp forest of Lempake, East Kalimantan. Malaysian Forester 44: 407–418.

Ali budin K & SAlleh S. 1993. Status and approaches towards biodiversity conservation in Peninsular Malaysia. Proceedings of the ASEAN Seminar on the Management and Conservation of Biodiversity. 30 November–2 December 1993, Kuala Lumpur.



AnonymouS. 1992. Progress report towards sustainable management of national tropical forest in Malaysia. 13th Session of ITTC, Yokohama.

AppAnAh S. 1999. Trends and issues in tropical forest management: setting the agenda for Malaysia. Paper presented at the Conference on Tropical Forest Harvesting: New Technologies Examined. 22–24 November 1999, Kuala Terengganu.

AppAnAh S & weinlAnd G. 1990. Will the management systems for hill dipterocarp forests stand up? Journal of Tropical Forest Science 3: 140–158.

AShton pS. 2008. Changing values of Malaysian forests: the challenge of biodiversity and its sustainable management. Journal of Tropical Forest Science 20: 282–291.

AuStin MP & heyliGeRS PC. 1989. Vegetation survey design for conservation: gradsect sampling of forests in north-eastern New South Wales. Biological Conservation 50: 13–32.

bARbieR EB, buRGeSS JC & FolKe C. 1994. Paradise Lost? The Ecological Economics of Biodiversity. Earthscan Publications Ltd, London.

buRGhoutS TBA, CAmpbell EJF & KoldeRmAn PJ. 1994. Effects of tree species heterogeneity on leaf fall in primary and logged dipterocarp forest in the Ulu Segama Forest Reserve, Sabah, Malaysia. Journal of Tropical Ecology 10: 1–26.

bidin AA & lAtiFF A. 1995. The status of terrestrial biodiversity in Malaysia. Pp 59–73 in Zakri AH (ed) Prospects in Biodiversity Prospecting. Genetics Society of Malaysia, Kuala Lumpur.

bRoweR JE, ZAR JH & Von ende CN. 1990. Field and Laboratory Methods for General Ecology. Third edition. WC Brown Publishers, Dubuque.

CAnnon CH, peARt DR & leiGhton m. 1998. Tree species diversity in commercially logged Bornean rainforest. Science 281: 1366–1368.

CRome FHJ, mooRe LA & RiChARdS GC. 1992. A study of logging damage in upland rainforest in north Queensland. Forest Ecology and Management 49: 1–29.

DOA (depARtment oF AGRiCultuRe). 1994. Soil survey report of six forest compartments in the Ulu Muda Forest Reserve, Baling, Kedah. Paper presented in Bengkel I, Kajian Kesan Pembalakan Terhadap Waduk di Hutan Simpan Ulu Muda, Baling, Kedah. Universiti Teknologi Malaysia, Skudai.

FiSheR RA, CoRbet AS & williAmS CB. 1943. The relation between the number of species and the number of individuals in a random sample of an animal population. Journal of Ecology 12: 42–58.

GilliSon AN & bReweR KRW. 1985. The use of gradient directed transects or gradsects in national resource survey. Journal of Environmental Management 20: 103–127.

huSSin MZ. 1994. Ecological effects of selective logging in a lowland dipterocarp forest on avifauna, with special reference to frugivorous birds. PhD thesis, Universiti Kebangsaan Malaysia, Bangi.

IUCN. 1992. Conserving Biological Diversity in Managed Tropical Forest. International Union for Conservation of Nature, Gland.

johnS AD. 1988. Effects of “selective” timber extraction on rain forest structure and composition and some consequences for frugivores and folivores. Biotropica 20: 31–37.

johnS AD. 1992. Species conservation in managed tropical forests. Pp 15–53 in Whitmore TC & Sayer JA (eds) Tropical Deforestation and Species Extinction. Chapman and Hall, New York.

johnS JS, bARReto p & uhl C. 1996. Logging damage during planned and unplanned logging operations in the eastern Amazon. Forest Ecology and Management 89: 59–77.

KARtAwinAtA K, AbdulhAdi R & pARtomihARdjo t. 1981. Composition and structure of a lowland dipterocarp forest at Wanariset, East Kalimantan. Malayan Forester 44: 397–406.

Kent m & CoKeR p. 1992. Vegetation Description and Analysis: A Practical Approach. John Wiley and Sons Ltd, London.

KRebS CJ. 1989. Ecological Methods. Harper and Row, New York.

mAGuRRAn AE. 1988. Ecological Diversity and its Measurement. Chapman and Hall, New York.

nG FSP (ed). 1978. Tree Flora of Malaya. Volume 3. Longman, London.

nG FSP (ed). 1989. Tree Flora of Malaya. Volume 4. Longman, London.

nG FSP, low CM & mAt ASRi NS. 1990. Endemic Trees of Malay Peninsula. Research Pamphlet No. 106. Forest Research Institute Malaysia, Kepong.

niCholSon DI, henRy NB & RuddeR j. 1988. Stand changes in north Queensland rain forests. Proceedings Ecological Society of Australia 15: 61–80.

noRhAyAti A. 2001. Frugivores and fruit production in primary and logged tropical rainforests. PhD thesis, Universiti Kebangsaan Malaysia, Bangi.

pinARd MA. 1995. Carbon retention by reduced impact logging. PhD thesis, University Florida, Gainesville.

pinARd m, howlett b & dAVidSon d. 1996. Site conditions limit pioneer tree recruitment after logging of dipterocarp forest in Sabah, Malaysia. Biotropica 28: 2–12.

RRIM. 1988. Training Manual on Soil, Management of Soils and Nutrition of Hevea. Rubber Research Institute Malaysia, Kuala Lumpur.

SAiFul i. 2002. Effects of selective logging on tree species diversity, stand structure and physical environment of tropical hill dipterocarp forest of Peninsular Malaysia. PhD thesis, Universiti Kebangsaan Malaysia, Bangi.

SAlleh MN. 1993. Forestry in Malaysia: issues and prospects. Akademika 43: 69–85.

SAlleh MN & mAnoKARAn n. 1995. Monitoring of forest biodiversity: policy and research issues. Pp 127–144 in Boyle TJB & Boontawee B (eds) Measuring and Monitoring Biodiversity in Tropical and Temperate Forests. Center for International Forestry Research, Bogor.

ShAmSudin i, iSmAil h & ChonG PF. 1999. Long haulage ground cable system as an alternative technique of harvesting in hill forests of Malaysia. Paper presented at the Conference on Tropical Forest Harvesting: New Technologies Examined. 22–24 November 1999, Kuala Terengganu.

SKoRupA JP. 1986. Responses of rainforest primates to selective logging in Kibale Forest, Uganda: a summary report. Pp 57–70 in Benirschke K (ed) Primates: The Road to Self-Sustaining Populations. Springer Verlag, New York.

tAumAS R. 1999. Implementation of reduced impact logging (RIL) in Sabah: the Innoprise Corporation Sdn Bhd experience. Paper presented at the



Conference on Tropical Forest Harvesting: New Technologies Examined. 22–24 November 1999, Kuala Terengganu.

whitmoRe TC (ed). 1972. Tree Flora of Malaya. Volume 1. Longman, Kuala Lumpur.

whitmoRe TC (ed). 1973. Tree Flora of Malaya. Volume 2. Longman, Kuala Lumpur.

whitmoRe TC. 1984. Tropical Rain Forests of the Far East. Second edition. Clarendon Press, Oxford.

whitmoRe TC. 1990. An Introduction to Tropical Rain Forests. Clarendon Press, Oxford.

wood GB. 1990. Ground-sampling methods used to inventory tropical mixed moist forests. Forest Ecology and Management 35: 199–206.

wyAtt-Smith j. 1987. The Management of Tropical Moist Forest for the Sustainable Production of Timber: Some Issues. IUCN/IIED Tropical Forest Policy Paper No. 4. International Institute for Environment and Development, London.

wyAtt-Smith j. 1988. Letter to the editor. Forest Ecology and Management 24: 219–223.

effects of selective logging on tree species … · hill dipterocarp forest of peninsular malaysia...

Documents