0090-B1

Rehabilitation of Degraded Peat Swamp Forests in Raja Musa Forest Reserve, Selangor, Peninsular Malaysia

P. Ismail^[1], I. Shamsudin, N. M. Nik Muhamad and I. Faridah Hanum

ABSTRACT

Data from the Third National Forest Inventory shows that there were about 0.23 million ha of logged peat swamp forests (PSFs) in Peninsular Malaysia. It is important to improve the productivity of these areas by planting commercial tree species in order to sustain its role as an important source of high-quality timber species. The main objectives of this study were to determine appropriate planting techniques and identify suitable timber species to rehabilitate highly degraded PSFs.

Field planting, which represents the core of the study, was conducted in Compartment 101, Raja Musa Forest Reserve. The area was classified as highly degraded PSF and occupied mostly by grass, especially Imperata cylindrica. Four different planting techniques were tested, namely open planting, open planting with mulching, open planting with topsoil and open planting with nursery trees. Six indigenous PSF species were used, namely Anisoptera marginata, Calophyllum ferrugineum, Durio carinatus, Madhuca motleyana, Gonystylus bancanus and Shorea platycarpa. Light intensity and foliar analysis studies were also conducted.

Open planting was found to be the best technique for rehabilitating highly degraded PSF. The technique produced the highest survival rate of 83.33%, lowest planting costs and was the easiest method. Foliar analysis indicated no significant differences in macronutrient status of seedlings among the different planting techniques. This indicates that the different planting techniques did not affect nutrient uptake by the planted seedlings. Out of six species used in the study, M. motleyana, S. platycarpa, A. marginata and G. bancanus with survival rate of 92.19%, 79.69%, 79.17% and 73.44% respectively were found suitable to be used for rehabilitating degraded PSF.

It is recommended that the Forestry Department carry out rehabilitation programs in the degraded PSFs. Permanent nursery to raise planting materials of PSF species should be established to support the rehabilitation program. Forest fire can be a major threat to degraded PSF, particularly in areas dominated by grass. Therefore, it is also recommended that studies to determine the best prevention and control measures of forest fire in the PSF be conducted.

This paper was presented at the XII World Forestry Congress in Quebec City, Canada, September 2003."

Introduction

The extent of peat swamp forests (PSF) in Peninsular Malaysia in 1981 was estimated about 0.67 million ha (Shamsudin and Ismail, 1991). The figure declined to 0.34 million ha in 1991. This reduction is associated with land developments where forested peatlands were cleared and developed for agriculture, aquaculture, industries and residential areas. Out of the 0.34 million ha, approximately 0.21 million ha are within the Permanent Forest Reserve (PFR) while the remaining 0.13 million ha are outside PFR or commonly known as stateland PSF. In 1992, there was about 0.23 million ha of logged-over PSF in Peninsular Malaysia (Chin et. al, 1997). Some of the logged-over PSF are severely damaged and categorised as highly degraded PSF. The highly degraded PSF is an area that occupied by grass mainly Imperata cylindrica with no big trees and low residual vegetation. About 30% out of 72,816 ha of PSF in North Selangor PSF is categorised under highly degraded PSF (Shamsudin et al., 1997; Anon, 1997; Woon and Parid, 1999).

It is important to improve the productivity of these areas by planting with commercial tree species, in order to sustain its role as an important source of high quality timber species. Otherwise these areas will only be colonised by pioneer species and susceptible to forest fire. Research on appropriate planting techniques using suitable commercial tree species needs to be conducted on these areas. This project will be act as a preliminary investigation on how to rehabilitate such areas as not much works have been done in the past to rehabilitate degraded/logged-over PSF (Ismail, 1998).

Objectives

Main objectives of this study were:

1. To determine appropriate planting techniques, and
2. to identify suitable species for rehabilitating highly degraded PSF.

Materials and methods

Raising planting material

Planting materials of PSF species are difficult to get, either in government and private nurseries (pers. obs.). This is because PSF species has never been highlighted in any planting projects. Therefore, raising sufficient planting materials acts as an important component of this research project. Planting materials of PSF species were raised using normal procedures applied to inland forest species (Aminah, 1991; Aminah et al., 1997). Besides collection of seeds that is common, other techniques used was wildings collection and vegetative propagation via stem cuttings. Moreover, management aspects of the PSF species in the nursery are also similar to others inland forest species.

Field planting

Study site and experimental design

Field planting that represents the core of the study was conducted in Compartment 101, Raja Musa Forest Reserve, Selangor, Peninsular Malaysia. The area was classified as highly degraded and occupied mostly by grass especially Imperata cylindrica.

A survival and growth performance of seedlings using four different planting techniques were examined. The following planting techniques were tested; open planting, open planting with mulching, open planting with topsoil and open planting with nurse tree. Open planting technique involved clearing of existing plants especially the Imperata cylindrica to eliminate unwanted competition and provide easy access for planting works. The clearing was done in strip of 1m width by using parang and brushing machine. The direction of planting strip was south to north and 2m width of existing grass was left uncut to avoid direct sunlight to the planted seedlings. A 100 gram of Christmas Island Rock Phosphate (15N:15P:15K) was put in the planting holes of 1 feet³ prior the planting. Then, the existing peat was used to cover up the planting holes. Basically, the same method is applied for the other planting techniques except additional treatment through mulching, topsoil and nurse tree provided at planting point. Fresh empty fruit bunch (EFB) of oil palm waste was used as mulching materials in the second method. While Hopea odorata size of 2m height were used as nurse tree in the last planting technique.

Six indigenous PSF species were used in this study. The species were selected based on their availability and commercial timber value. The species were Anisoptera marginata, Calophyllum ferrugenium, Durio carinatus, Madhuca motleyana, Gonystylus bancanus and Shorea platycarpa.

A split plot design of 128m x 121m (1.55 ha) was used with three replications (36m x 111m) comprises all species and planting techniques. In each subplot, total of 16 seedlings were planted at a spacing of 3m × 3m. The total number of seedlings planted was 1,152 (192 seedlings/species).

The planting materials that fulfil the requirement (Ang et. al., 1992) were transported to the field for planting. Hardening was conducted on the seedlings before being transferred to the planting sites. During hardening, light intensity was increased while frequency of watering reduced.

Data collection

The establishment of plots was completed in August 1999. The field planting was initially planned to collect 12 months data for analysis. Unfortunately, due to forest fires in April 2000 approximately eight months after the establishment, data collection in the plot was disrupted. Therefore, the experiment only used data collected over a period of eight months.

The following parameters were monitored:

Survival

The survival of seedlings planted were monitored and recorded every month. Factors affecting survival of the seedlings were also noted.

Basal diameter and total height measurements

The basal diameter (BD) and total height (TH) were measured and recorded every month. BD was measured at 5 cm above the ground by using a digital diameter calliper. To ensure each measurement is taken at the same point, the individual plant was marked at 5 cm above the ground.

Measurement for BD was recorded in millimetre (mm). Meanwhile, TH measurement was recorded by using a long stick with graduation in centimetre (cm). Measurements were recorded to the nearest one decimal point.

Supporting experiment

Two supporting experiments were conducted in the study namely; light intensity and foliar analysis. Light intensity study was conducted in the nursery at FRIM, whereas foliage samples taken from the nursery and field planting in the Compartment 101, Raja Musa FR were used for the foliar analysis. Findings from these supporting experiments will be used to support survival and growths results of the field planting.

The light intensity study was conducted with the main aim to investigate and understand growth responses of these species to various light conditions. Three different relative light intensities (RLI) were used; 100%, 70% and 30%. Two shade chambers of 3m height, 4m wide and 12m long were constructed and the chambers were fully covered with sarlon net that represent 70% and 30% RLI respectively. 20 seedlings of each species aged about one-year old were placed in the shade chambers as well as in the open area. All seedlings, either in the shade chambers or open areas was given similar treatments with respect to watering, fertiliser applications and weeding.

The foliar analysis was conducted in three different stages; stage 1: before planting (in nursery), stage 2: three months after planting and stage 3: six months after planting. Foliar analysis in stage 1 is to determine the status of nutrients in favourable growing conditions at the nursery. The seedlings were fertilised with 1 gram of nitrophoska blue (15N:15P:17K) every month throughout the duration of 12 months in the nursery.

Meanwhile at the planting site, the foliar analysis was done to determine nutrients intake by seedlings at different planting techniques at three and six months after planting. The leaves were not sampled immediately after planting to avoid more stress because according to Ahmad Zuhaidi et al. (1997), the first two months after planting is very crucial for the seedlings to establish. Leaves from individuals at each planting technique were collected and pulled as one sample. In each exercise, all together 24 samples were collected. The samples of leaves were taken into laboratory for the foliar analysis. In the laboratory, at least 20 gram of wet weight or about 15 leaves were required for the analysis. Procedures of foliar analysis to determine the nutrients were described by Wan Rashidah et al. (1989).

Results and Discussion

Planting technique assessment

Results of eight months after planting shows that open planting had the highest survival and lowest cost of planting per seedlings (Table 1). Open planting with mulching had lowest survival and moderate cost (20% additional cost compared to the open planting), meanwhile open planting with topsoil also had high survival and with moderate cost (additional 25% compared to the open planting).

Whereas, open planting with nurse tree had also high survival but it had the highest cost (additional 124% compared to the open planting). The high cost in nurse tree experiment was attributed to tall seedlings acquired for planting as shade tree (2 m height of H. odorata about RM6.00/sapling). Moreover, cost of labour also high because more seedlings (nurse tree) need to be planted in this planting technique.

Table 1. Summary of results based on the planting techniques

Based on the foliar analysis, generally it was found that no differences in term of macronutrient status in different planting techniques. This means that, different planting techniques do not affect the nutrient intake by seedlings at least for period of six months after planting.

Open planting with mulching was found unsuitable to be used as planting technique for rehabilitating highly degraded PSF. This was due to two main reasons; the fresh (EFB) of oil palm used as mulching materials were attractive to wild boar. It has been observed that wild boar dug up mulching materials placed on top of planting holes. They would probably be mistaken that as new food source for them. It caused extensive damaged to planted seedlings. It was observed that only seedlings planted by using this planting technique attracted to wild boar. The attraction maybe due to fried-oil smell produced by the fresh EFB.

Another reason is the fresh EFB produced hot vapour in a normal decaying process that subject leaves to hot air temperature and become dried. Therefore, fresh EFB of oil palm should not be used as mulching material but the dried one in the form of mulching mat maybe suitable for use in planting programs. Wan Asma and Wan Rasidah (1998) reported that dried EFB in the form of mulching mat was successfully used as mulching materials for planting seedlings of Tectona grandis.

Though, open planting with topsoil and open planting with nurse tree had high survival rate they incurred an additional cost of 25% and 124% respectively. Therefore, the best planting technique for rehabilitation highly degraded areas in PSF is open planting. The technique produced high survival as well as gave the lowest cost. Furthermore, the technique was found to be the easiest method in the planting experiment (pers. obs.).

Species assessment

Based on Table 2, M. motleyana had the highest survival with 92.19% and the species preferred light conditions at 70% to 100% RLI or moderate to open area for both basal diameter increment (BDI) and total height increment (THI). Second best performance in term of survival was S. platycarpa with 79.69% and the species adapted very well in the wide range of light conditions (30% to 100% RLI).

A. marginata was in the third place with survival of 79.17% and adapted to light conditions of 70% to 100% RLI or medium to open area. One more species that showed good performance in term of survival was G. bancanus with 73.44% and the species adapted very well at 100% RLI. Shamsudin and Ismail (1999) reported that 58% of G. bancanus still survived six years after planted in an open non peat soil area. The results showed that, the species (M. motleyana, S. playcarpa, A. marginata and G. bancanus) are suitable to be used for rehabilitating highly degraded areas in the PSF.

Another two species; D. carinatus and C. ferrugineum had low survival with only 66.15% and 56.25% respectively. Furthermore both species preferred low to moderate light conditions (30% to 70% RLI). Therefore, the species are not suitable to be planted in an open area such as the grassland in the PSF. However, both species are expected to growth better in more moderately disturbed areas.

Table 2. Summary of results based on the species

Note:

* in the field palnting, BDI and THI were not significant different
** in the light intensity study, survival was not significant different
BDI = basal diameter increment
THI = total height increment
RLI = relative light intensity

Conclusion and recommendations

Conclusions from the studies are as follows:

1. It was found that planting materials of PSF species could be raised through collecting of wildings, seed and vegetative propagation via stem cutting using normal procedures applied to others inland forest species.

2. Management of PSF species in the nursery is also similar to others inland forest species.

3. Open planting was found to be the best planting technique to be used for rehabilitating highly degraded areas in PSF.

4. Four indigenous species of PSF suitable for rehabilitating the highly degraded areas are Madhuca motleyana, Shorea platycarpa, Anisoptera marginata and Gonystylus bancanus.

5. The study showed promising results on rehabilitation of highly degraded areas using PSF tree species. Therefore, rehabilitation works in other less degraded areas is expected to have better results.

6. Forest fire was found to be the main threat to degraded PSF especially in area dominated by grass. More research needs to be conducted on mitigation measures that could be implemented to minimise the occurrence of forest fire. Probably a control measure to regulate water level would be a good solution to prevent fire hazard in degraded PSF areas.

Recommendations can be made from the studies are:

1. Rehabilitation of logged-over PSF should be conducted. In fact, rehabilitation is part of silvicultural treatments applied to other logged-over forests. Therefore, logged-over PSF should also be included in the forest rehabilitation program. The productivity of logged-over PSF areas could be improved and this will sustain the production of high quality timber species and reduce fire risks.

2. Permanent nursery for raising planting materials should be established. The nursery will ensure continuos supply and low cost of the planting materials.

3. Sufficient large seed production area in the PSF should be identified and permanently demarcated.

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