INTRODUCTION

In the species-rich tropical forests, the most appropriate form of management is to rely on natural regeneration to provide the future crop through selective felling of the mature crop. Following the Selective Management System (SMS), as practiced in Peninsular Malaysia, advanced growth of 30-45 cm diameter at breast height (dbh) is expected to produce the next harvest. Therefore it is important to note that residual stands must be adequate in quantity and of a specific quality to ensure a future yield that is both economical and sustainable in the long term.

An understanding of the distribution, regeneration status and growth potential of logged-over forests is important in ensuring the sustainable production timber. An assessment of the residual stocking and development status of logged-over forests was carried out by examining the data obtained from growth plots that have been established in the State of Kedah since 1992. Based on the enumeration of data obtained from these plots, the results of the analysis are discussed with particular reference to their implications on future production. 

METHODOLOGY

Site description

The growth plots in the State of Kedah were randomly distributed in  three (3) forest districts namely North Kedah Forest District, Central Kedah Forest District and South Kedah Forest District. In each district, a total of three (3) Growth Plots of were established. These plots were established based on the following characteristic, namely :

• Located in the Permanent Reserve Forest;
• Number of years after logging to sufficiently represent the different stages of forest development after logging; and
• Available information on Pre-Felling Inventory and Post-Felling Inventory for the purpose of stocking and species comparison.

The size of each plot is one (1) hectare with 25 sub-plots of 20m x 20m and 9 sub-plots of 10m x 10m. In the 20m x 20m sub-plots all trees 5cm – 10cm dbh were measured (Forestry Department Peninsular Malaysia 1992).

The first enumerations were made in 1992 and here since being re-measured seven times. The years 2004 was used as the reference year in relation to the year that the compartment was logged. The definitions of original forests in terms of good, moderate and poor were based on the Second National Forest Inventory 1981-1982 (Forestry Department Peninsular Malaysia 1987).

CONCLUSION

Much more work needs to be undertaken so as to better understand the structure and regeneration status, as well as the growth and development of logged-over forests. Based on the above data analyses, the following conclusions were drawn. The stocking and basal area of all the nine growth plots in the State of Kedah showed gradual increment over time after logging, with the dipterocarp group gaining increasing dominance with the number of years after logging. The results also showed a general trend towards the original stand composition in most of the logged-over forest. The most important factor in ensuring sustainable timber production in the future is the retention of sufficient numbers of trees of the desired species groups after logging, particularly for size classes between 30 to 45 cm dbh. In this regard, all the compartments recorded a recorded a residual stand containing commercial species of more than 30 trees/ha having diameter size of 30 cm dbh and higher. The dipterocarp group was found to be growing faster at the higher diameter classes and thus becoming more dominant in terms of size, basal area and volume contribution towards the stand. It is suggested that the Dipterocarp Forest Growth Simulation Model (DIPSIM) be used to assist the Forestry Department in predicting the next harvest for different forest conditions and harvesting regimes by using the growth data obtained from the 96 growth plots established in Peninsular Malaysia. Basically it is an individual tree based model which allows for the simulation of annual growth in terms of stems, basal area and volume and the effect of different harvesting prescriptions to provide support for decisions in yield prediction. Finally, the monitoring of growth and development in logged-over forests is an important activity in ensuring sustainable management of forest resources. Further analysis of the growth data over longer terms is needed to indicate threshold levels for composition, removal and retention for different forest types. This will assist in fine-tuning the currently employed management practices to achieve sustainable forest management.

SUMMARY OF RESULT DIAMETER INCREMENT, VOLUME, BASAL AREA, MORTALITY AND INGROWTH AT DATA > 30 CM DBH

 INFORMATION ON GROWTH PLOTS

 'CONTINUOUS FOREST INVENTORY (CFI)' PLOTS

 KETERANGAN MENGENAI STRATA HUTAN 

 
GROWTH & YIELD PLOTS (PETAK TUMBESARAN DAN PENGELUARAN)