Dr. Ross Wylie
Dr. Ross Wylie is the program leader, Forest Protection,
Queensland
Forestry Research Institute. He has 33 years of professional
experience
in forest entomology in the tropics and subtropics, principally
in
Queensland, Papua New Guinea and Southeast Asia. He is currently a
member of the Forest Health Committee of the Standing Committee on
Forestry, and formerly the Forestry Representative on the Plant Health
Committee of the Standing Committee on Agriculture and Resource
Management (under the aegis of the Agriculture and Resource
Management
Council of Australia and New Zealand). He is also the
current Deputy
Chairman of Research Working Group 7 (Forest Health),
under the aegis of the
Research Priorities and Coordination Committee
of the Australian
Government's Standing Committee on Forestry; and also
a member of the Board
of Scientific Consultants to the World Koala
Research Corporation.As a well-experienced entomologist, Dr. Wylie has
had
also a number of consultancies abroad such as in Papua New Guinea,
Indonesia, Bangladesh, Malaysia, New Zealand, Thailand, and the
Philkippines.
Dr. Wylie obtained his PhD in Botany
in 1987, Masteral degree in Entomology
in 1976 and Bachelor of Science
degree in 1967, all at the University of
Queensland.
Abstract
Integrated pest management (IPM) has been defined in many ways but essentially involves the use of a combination of pest management tactics to reduce economic losses caused by pests to tolerable levels, with minimal environmental side effects. Most success stories of IPM come from agriculture. Forestry, especially in the tropics, has tended not to implement anything like the complexities of IPM employed in intensive agriculture. A tactic of key importance for forestry is that of prevention, and it is essential that forest entomologists and pathologists be involved in the early planning stages of any new plantation project. There are many challenges in implementing IPM in forestry. Defining an economic injury level for a long-lived perennial crop such as trees is not simple because economic and biological forecasts sometimes need to be made over decades. Defining economic damage and determining economic threshold are similarly problematical. Management objectives for a given forest stand need to be clearly defined by managers so that pest impacts can be judged in that context. In many forest situations, the cost of intensive monitoring programs is unaffordable, while a shortage of trained protection staff in many developing countries in the tropics is also a hindrance to the implementation of IPM. Examples are given of operational forestry IPM programs in the tropics and subtropics, including the wood wasp Sirex noctilio in Australia and South America, the bark beetle Ips grandicollis in Queensland, Rhizina root disease and Sphaeropsis dieback in South Africa, and the sal borer Hoplocerambyx spinicornis in India.
The concept of Integrated Pest Management (IPM) was developed in the late 1950s and early 1960s in response to problems of insecticide resistance and insecticide-induced pest resurgence, plus growing concerns of environmental contamination (Clarke 1995). It was conceived as a means to reduce the use of pesticides, and to encourage the more "ecologically friendly" use of pest natural enemies via biological control (Mariau 1999). IPM has been defined in many ways over the years, but a useful definition is that of Borror et al. (1981) who describes IPM as "...employing the optimum combination of control methods, including biological, cultural, mechanical, physical and /or chemical control measures, to reduce a pest below an economic threshold, with as few harmful effects as possible on the environment and non-target organisms".
Most success stories of IPM come from agriculture. Forestry, especially in the tropics, has tended not to implement anything like the complexities of IPM employed in intensive agriculture, but the objectives are the same. Because the definition is so broad, most sets of tactics can be labeled as IPM, but one of key importance for forestry is that of prevention. A summary of many of the basic reasons for insect pest outbreaks in tropical forestry is presented in Figure 1 (Speight 1997). The right hand side of the diagram illustrates how pest problems might be lessened while the left-hand side provides "recipes" for disaster (from an entomological perspective). In operational forestry, some high-risk situations or silvicultural practices may be unavoidable, and it is then that IPM will attempt to use control tactics rather than preventative ones (Speight and Wylie 2000).
Figure 1. Summary of some major factors which may interact to create insect pest outbreaks in tropical forestry which are potentially manipulatable to reduce the probability of damage (from Speight 1997).
Speight et al. (1999) summarize the types of management that might be employed in a general IPM system for tropical forestry (Figure 2). As the authors explain, not all the components shown would necessarily be available or required in any one IPM program, but various elements are evident in the examples provided later in this paper. As can be seen in section A of the diagram, there needs to be a great deal of planning and decision making carried out before a tree seed is ever planted. It is essential that entomology and pathology are fully considered right at the very start of any new forestry project, but all too often, such aspects are ignored. Sections B and C also need to be implemented in an ideal IPM program so that even if the choices made in section A fail to prevent pest problems completely, the magnitude of such problems can be predicted and dealt with appropriately. Section D is the actual hands-on manipulation of insect pest populations and comes into play once the previous sections have been implemented.
Figure 2. Theoretical components of a generalised IPM System
As outlined by Clarke (1995), the key issues for any IPM program are (i) defining economic damage [the amount of injury which will justify the cost of artificial control measures]; (ii) determining the Economic Injury Level (EIL) [the lowest pest population density that will cause economic damage]; and (iii) determining the economic threshold (ET) [the density at which control measures should be initiated to prevent an increasing pest population from reaching the economic injury level]. This involves detailed knowledge of the pest population dynamics, forest stand dynamics, treatment strategies and impact on resource values (Waters and Cowling 1976). Put simply, forest managers must be provided with the tools and information that will enable them to predict the occurrence of damaging pest populations, the impact of this damage on tree growth, wood quality and stand dynamics, and to predict the effectiveness and cost of various control options (Elliott et al. 1998). This is by no means a straightforward task, as discussed below.
Defining economic damage, EIL and ET
Defining an EIL for a long-lived perennial crop such as trees is not simple because economic and biological forecasts sometimes need to be made over decades. Factors which can only be estimated include the future dynamics of the pest population, the damage which may be caused by the present (or future) infestation (s), the effectiveness of the control strategy, crop growth rate after attack and the value of the crop at harvest (Clarke 1995). The margin for error is thus great. Obviously, the more we know about the pests, the forest stand dynamics and the interactions between these, the more accurate are likely to be our forecasts. However, with increasing refinement of IPM modeling comes increased cost.
Figure 3. Concept of economic threshold in insect pest management (from Speight et al. 1999).
Similarly, in defining economic damage, a large number of external factors need to be taken into account such as company and government policy, forest economics and environmental pressure. As an example, on the Indonesian island of Sumatra in the late 1980s, a pulp and paper company constructed a mill and simultaneously established plantations of eucalypts, the first of which were scheduled to be harvested in 8 years when the existing resource was exhausted. The plantations suffered severe attack by sap sucking mosquito bugs (Helopeltis spp.) (Hemiptera: Miridae) which resulted in tip dieback, bushing of trees and growth check, sufficient to threaten harvesting schedules and thus pulp supply to the mill. In this situation, the insect damage assumed greater economic importance than just the direct growth losses, and would justify higher expenditure on control. Determination of the economic threshold depends largely on the forest manager's judgment of how quickly control measures may be implemented. In forestry, the response time may be long and this may hinder the effectiveness of some IPM strategies when pest damage occurs over a short period.
An added complexity is that in many cases insect pests are not acting in isolation but interact with one or more other insect species, pathogenic fungi or other pest organisms. Ideally, the combined effects of these pest complexes are measured and projected in IPM systems (Elliott et al. 1998).
Monitoring
IPM relies heavily on monitoring to identify areas where pest populations are high, and economic thresholds are likely to be exceeded (Clarke 1995). In contrast to the situation with intensive agriculture, in large and inaccessible forest areas such monitoring may be impractical, or at least, inaccurate. Cost of monitoring in many forest situations may be unaffordable.
Trained protection staff
As is obvious from both Figures 1 and 2, IPM is complicated and requires much more expertise, planning and forethought than would be required for standard techniques of pest control such as routine insecticide spraying. Advice from trained forest protection specialists is essential at all stages of the program, but this may not be available in all developing tropical countries, and will be a particular problem for small-scale forest operations. In Nigeria, for example, Akanbi and Ashiru (1991) in their discussion of IPM for forest defoliators mention a shortfall in the number of well-trained forest entomologists as a limitation in the adoption of such programs. They also cite an analysis of plant protection in 15 African countries, including Nigeria, which showed that, although all the countries concerned have a plant protection service, often these services involve one or a few persons with little or no support facilities or funds to practice effective plant protection.
Economics and impact assessment
Not only is IPM complex but, as indicated in previous sections, it can be expensive. Cost-benefit analyses will indicate whether the economic impact of pest attack in tropical forests outweighs the actual cost of management. This is not always the case, even when clear damage is occurring. An example is the situation described by del Valle and Madrigal (1993) in Columbia, where Pinus patula plantations were attacked by at least two species of moth caterpillars. Increment losses were assessed quantitatively over 4 years. The results showed that there were considerable losses in diameter growth initially for defoliated trees. However, after only 18 months, their mean diameter growth rates were not significantly different from that of trees which had not been defoliated, and after four years the growth rates were identical. Economic analyses revealed that since the cost of IPM for defoliators in Columbia ranged from approximately US$ 9 to US$ 16 per hectare, depending on which strategies were actually employed, then even if up to 90% reduction in pest problems could be achieved, IPM was not an economically worthwhile option (Table 1).
Table 1. Financial return in US$ per hectare of Pinus patula for pulp and other products after varying levels of IPM against defoliating Lepidoptera (from del Valle and Madrigal 1993).
EFFICIENCY OF IPM |
RETURN (US$ PER HA) |
90% |
17.09 |
80% |
15.19 |
70% |
13.29 |
60% |
11.4 |
50% |
9.5 |
NB - Cost of IPM ranges from US$ 9.06 to US$ 16.24 per hectare | |
An example of how an insect can have both negative and positive impacts depending on the management objectives of the forest, is provided by Wickman (1980). He showed that an outbreak of a defoliating insect can reduce the increment of individual trees in the short term but increase mean annual increment of the whole stand over the long term. This can occur through the outbreak causing some tree death, and the residual trees eventually increasing their growth due to a thinning effect and increased nutrient cycling. The first impact would be negative for a short rotation stand but the second impact would be positive for a long rotation stand. Management objectives for a given forest stand need to be clearly defined by managers so that impacts can be judged in that context.
Sirex wood wasp in Australia and South America
Sirex wasp, Sirex noctilio (Hymenoptera: Siricidae), from southern Europe, was accidentally introduced into Australia almost 50 years ago and is a serious pest of Pinus spp. plantations. The female wasp lays its eggs in the sapwood of susceptible trees, depositing a symbiotic fungus and a phytotoxic mucus. The mucus changes the water relations of the tree creating conditions which are ideal for the growth and spread of the fungus. The fungus reduces the moisture content of the green wood to levels more favourable for egg hatching, provides essential nutrients to larvae and rots the wood, thereby facilitating tunneling of larvae (Neumann et al. 1987). The combined effects of the mucus and the fungus cause tree death.
The present distribution of sirex is in the eastern half of Australia where it has spread from the temperate south to the subtropics of northern New South Wales. Since its introduction, there have been several serious outbreaks, the most destructive of these occurring from 1987 to 1989 in the southeast of South Australia and adjacent areas of southwestern Victoria, when over five million P. radiata trees with a royalty value of A$10-12 million were killed (Haugen et al. 1990).
As described by Elliott et al. (1998), the IPM strategy employed against sirex combines detailed monitoring and detection methods, silvicultural treatments and biological control. Detection relies on forest surveillance by aerial and ground inspections and a trap tree plot system which uses herbicide-injected trees in plots, arranged on a fixed grid depending on infestation level, to attract and concentrate sirex populations. The objective of this strategy is to detect sirex in a given locality before annual sirex-induced tree mortality reaches infestation levels of 0.1 percent (1-2 trees per hectare in an unthinned stand). Changes in tree mortality are monitored using ground transects, aerial survey and photography, and trap tree plots.
Silvicultural treatment of P. radiata plantations by thinning to maintain/ improve tree vigour is a key factor in preventing sirex establishment or keeping damage within acceptable levels. Control of sirex populations established in a plantation is achieved by biological means using the parasitic nematode Beddingia siricidicola (by artificially inoculating nematode cultures into sirex-attacked trees whence they sterilise, and are carried by, the emerging sirex adults), and parasitoid wasps. Regular evaluation of the dispersal and effectiveness of these biocontrol agents is an essential component of the strategy.
In South America, S. noctilio was first detected in Uruguay in 1980, in Argentina in 1985, and in Brazil in 1988. Current annual losses in Brazil are estimated at US$ 5 million (Iede et al. 1998). Brazil has implemented most of the components of the Australian IPM strategy described above and the other countries are working towards this.
Five-spined bark beetle in Queensland, Australia
The bark beetle Ips grandicollis (Coleoptera: Scolytidae) is native to north America and was accidentally introduced into South Australia in 1943 and into Western Australia in 1952 via importation of pine logs with bark on from the United States (Morgan 1967). It has since spread to other States, reaching subtropical southern Queensland in 1982 and crossing the tropics in central Queensland in 1994 (Wylie et al. 1999). It is mainly a secondary pest, infesting recently felled trees, logging debris, and standing trees damaged by lightning, wind, fire or drought, but primary attack affecting large numbers of healthy trees has been recorded on several occasions when beetle populations were high. In Queensland in 1994, following fire in plantations of Pinus elliottii, P. caribaea and P. taeda, Ips grandicollis and its associated sapstain caused losses estimated at several million dollars Australian, mostly in privately-owned plantations where salvage was delayed for several months (Wylie et al. 1999).
There are several strategies used to limit the spread and reduce damage by I. grandicollis in Queensland. There is a prohibition on the movement of logs with bark on or of bark chip from a declared infested zone, unless the material is first fumigated. Pheromone traps baited with ipsenol are used to monitor quarantine boundaries. Where large numbers of trees are damaged by fire or other agents, they are rapidly salvaged both to prevent degradation and to minimise build up of the bark beetle populations. Large accumulations of logging slash may be burnt or chopper-rolled. Biological control agents (two species of wasp parasitoids and two coleopteran predators) have been released in all areas where the pest occurs, the wasps now being widely established. Thus, the IPM for I grandicollis in Queensland combines quarantine, silvicultural techniques and biological control.
Integrated management of forest tree diseases in South Africa
As described by Wingfield and Swart (1994), two of the most important disease problems of Pinus spp.plantations in South Africa are Rhizina root disease that develops after slash burning and Sphaeropsis dieback of hail-damaged pines. Rhizina undulata requires a heat stimulus for the onset of pathogenicity. Slash burning after clearfelling has been a commonly accepted silvicultural practice but this often resulted in extensive mortality of newly-planted seedlings due to infection by R. undulata. A consequence of the discontinuation of this practice in South Africa has been a build-up in populations of the pine root-infesting bark beetle Hylastes angustatus (Coleoptera: Scolytidae). These insects breed in old pine stumps and roots and, after emergence, feed on and girdle the newly planted seedlings. This has necessitated the implementation of chemical control for H. angustatus in the summer rainfall areas of the country. A strategy used to reduce Rhizina damage after accidental fire is delayed planting. Sanitation felling and removal of Rhizina-infected older trees is also necessary to prevent build-up of another bark beetle Orthotomicus erosus (Coleoptera: Scolytidae).
Sphaeropsis sapinea has caused extensive mortality of Pinus spp. following hail damage in South Africa, and Zwolinski et al. (1990) have estimated that losses of US$ 3.2 million per year have been incurred. Damage due to Sphaeropsis dieback is often exacerbated through infestation of trees by the weevil Pissodes nemorensis (Coleoptera: Curculionidae) and Orthotomicus erosus. Management of the dieback is largely achieved by planting resistant/ tolerant species (such as P. elliottii) in areas prone to hail damage and reducing insect populations in Sphaeropsis-infected trees by selective felling and associated sanitation practices (Wingfield and Swart 1994).
Sal heartwood borer in India
Hoplocerambyx spinicornis (Coleoptera: Cerambycidae) is the most serious forest pest affecting sal (Shorea robusta) forests in India, its larvae girdling and killing trees and riddling the heartwood with large tunnels. It is normally a pest of felled and dying sal but during epidemics, it attacks healthy trees of all ages and girth (Thakur 2000). During such epidemics, millions of trees may be killed, the losses totaling millions of rupees annually. Pest management is structured around a combination of preventative and remedial measures. The preventative measures are essentially silvicultural practices and consist of (a) regulating the time of felling (in winter when the beetles are not around); (b) removal of logging debris from the forest; and (c) regular monitoring to detect infested trees. Remedial measures include disposal of all infested materials by extraction, conversion and burning, and the use of trap trees. The trap tree operation is based on the principle that the beetles are attracted to fresh sap of the sal. In areas where there are active infestations of the pest, a few trees are felled, cut into billets and the bark beaten to facilitate oozing of the sap. Beetles are attracted to the sap from distances of up to 3 km away. Traps are inspected daily and beetles found are destroyed manually. A single trap tree remains effective for 8 to 10 days (Thakur 2000).
The examples provided above contain many of the elements of IPM outlined in Figure 2, and these tactics are summarised below.
Example |
IPM tactics |
Sirex noctilio wood wasp in Australia & South America |
Detailed monitoring & detection (aerial & ground survey, trap trees), thinning to improve stand vigour, biological control |
Fivespined bark beetle Ips grandicollis in Queensland |
Quarantine & pheromone monitoring of zone border, salvage of damaged trees, destruction of logging slash, biological control |
Rhizina root disease, Rhizina undulata in South Africa |
Chemical insecticides, delayed planting, sanitation felling and removal |
Sphaeropsis dieback Sphaeropsis sapinea in South Africa |
Use of resistant/ tolerant tree species, sanitation felling and removal |
Sal heartwood borer Hoplocerambyx spinicornis in India |
Regulate timing of felling, removal of logging debris, monitoring to detect infested trees, sanitation felling and removal, trap trees |
It can be seen that the tactics include both preventative and remedial measures and the IPMs range in complexity and cost from that of sirex wood wasp (with its need for detailed monitoring and detection, and field inoculations of parasitic nematodes) to the sal heartwood borer where the techniques are straightforward and not particularly expensive.
As indicated in the introduction, nowadays the term IPM is applied to almost any set of tactics used in controlling pest populations, but as argued by Clarke (1995) this is technically not the case. He cites several other pest management models which use control methods identical to those used in IPM, but without the need to develop formal threshold/ impact models or to rely on regular field population monitoring. These include (a) prophylactic applications or fixed control schedules which may be appropriate where EILs are very low, very high, or where monitoring is difficult and response time slow; (b) crisis applications where the pest is an `outbreak' species, reaching critical levels relatively rapidly but infrequently; and (c) silvicultural management, such as planting insect-resistant tree species, in forests where the potential income is limited (minimum maintenance is required post-planting). Clarke is quite correct in that many forest IPMs, particularly in the tropics, are not `pure' models, the example of Ips grandicollis in Queensland given earlier being a case in point. This bark beetle is of only occasional economic importance and does not warrant intensive population monitoring and the setting of EILs. Nevertheless, a combination of control techniques are employed to minimise its damage at a level commensurate with its importance, and the term `integrated pest management' is not entirely inappropriate in the spirit of the Borror et al. (1981) definition quoted earlier. As Clarke intimates, it is perhaps best not to be locked into too strict a definition of IPM and to consider a range of models. My own definition of IPM, to add to the growing list, would be 'the use of a combination or set of control measures, preventative and/ or remedial, to contain a pest within operationally-acceptable levels of damage with minimal environmental side effects'.
Akanbi, M.O. and Ashiru, M.O. (1991). Towards integrated pest management of forest defoliators: The Nigerian situation. Forest Ecology and Management 39:81-86.
Borror, D.J., DeLong, D.M. and Triplehorn, C.A. (1981). An Introduction to the Study of Insects, 5th Edition. (Saunders College Publishing: Philadelphia).
Iede, E.T., Schaitza, E., Penteado, S., Reardon, R.C. and Murphy, S.T. (1998). Proceedings of a Conference: Training in the Control of Sirex noctilio by the Use of Natural Enemies. Colombo, Brazil, November 4 to 9, 1996.
Clarke, A.R. (1995). Integrated pest management in forestry: some difficulties in pursuing the holy grail. Australian Forestry 58(3):147-150..
del Valle, J.I. and Madrigal, A. (1993). Economic impact of damage by defoliators in plantations of Pinus patula. Turrialba 43(2):119-126.
Elliott, H.J, Ohmart, C.P. and Wylie, F.R. (1998). Insect Pests of Australian Forests: Ecology and Management. (Inkata Press: Singapore).
Haugen, D.A., Bedding, R.A., Underdown, M.G. and Neumann, F.G. (1990). National strategy for control of Sirex noctilio in Australia. Australian Forest Grower 13(2), Special liftout Section No. 13.
Mariau, M. (1999). Integrated Pest Management of Tropical Perennial Crops. (CIRAD: France).
Morgan, F.D. (1967). Ips grandicollis in South Australia. Australian Forestry 31:137-155.
Neumann, F.G., Morey, J.L. and McKimm, R.J. (1987). The Sirex Wasp in Victoria. Bulletin No. 29, Lands and Forests Division, Department of Conservation , Forests and Lands, Melbourne.
Speight, M.R. (1997). Forest pests in the tropics: current status and future threats. In Watt, A.D., Stork, N.E. and Hunter, M.D. Forests and Insects, 207-228; (Chapman and Hall: London).
Speight M.R., Hunter M.D., and Watt A.D. (1999) Ecology of Insects :Concepts and Applications. (Blackwell Science: Oxford).
Speight, M.R. and Wylie, F.R. (2000). Insect Pests in Tropical Forestry. (CABI: Wallingford).
Thakur, M.L. (2000). Forest Entomology: Ecology and Management. (SAI Publishers: Dehra Dun).
Waters, W.E. and Cowling, E.B. (1976). Integrated forest pest management: a silvicultural necessity. In Apple, J.L. and Smith, R.F. Integrated Pest Management, 147-177, (Plenum Press: New York).
Wickman, B.E. (1980). Increased growth of white fir after a Douglas-fir tussock moth outbreak. Journal of Forestry 78:31-33.
Wingfield, M.J. and Swart, W.J. (1994). Integrated management of forest tree diseases in South Africa. Forest Ecology and Management 65:11-16.
Wylie, F.R., Peters, B., DeBaar, M., King, J. and Fitzgerald, C. (1999). Managing attack by bark and ambrosia beetles (Coleoptera: Scolytidae) in fire-damaged Pinus plantations and salvaged logs in Queensland, Australia. Australian Forestry 62(2):148-153.
Zwolinski, J.B., Swart, W.J. and Wingfield, M.J. (1990). Intensity of dieback induced by Sphaeropsis sapinea in relation to site conditions. European Journal of Forest Pathology 20:167-174.
Dr. Elias
Dr. Elias is a lecturer of
the Faculty of Forestry and of Postgraduate
Program Study at Bogor
Agricultural University where he got his
Engineering degree in Technology of
Forest Products in 1981. He
obtained his PhD in 1989 from the Faculty of
Forestry, Munich University.
Dr. Elias has a number of work on reduced
impact logging. One of these
is his case study on the Tropical Natural
Forests of Indonesia which was
published by FAO in 1998. He had prepared a
pocket book on Reduced
Impact Logging as well as on Felling and Skidding in
Reduced Impact
Timber Harvesting. He was also an FAO Consultant for National
Code of
Forest Harvesting Practices in Myanmar.
Abstract
By their nature, forest plantations in the tropics can have a great impact on the environment, therefore the intensive forest management of plantation should give more attention on this particular issue, mainly on the timber harvesting operations.
The purpose of this paper is to present the reduced impact timber harvesting (RITH) in tropical forest plantation. The damages to the forest ecosystem in plantation under intensive forest management should be minimized as much as possible. This can be obtained through landscape planning of plantation area; good road network system and harvesting plan; marking of "future" - trees in thinning; low impact timber harvesting technologies and improved techniques; appropriate forest engineering; education and training; etc.
It is expected that limiting the damages will result in protection and maintenance of the long term integrity and value of the forest resources and environmental service.
Key words: RITH, tropical plantation and landscape planning
Most plantations in tropical countries have been managed according to classical sustainable yield principles, with the main purpose to produce industrial roundwood (e.g. saw logs, veneer logs, pulp wood).
Thinning and clear felling of large areas are very common in harvesting operation of forest stands in plantation, mainly in pulp wood plantation, which is characterised by intensive forest management; producing large quantities of pulpwood, large-scale harvesting operations and using highly mechanised machines.
By their nature, forest plantations can have a great impact on the environment, therefore the management of forest plantation should give more attention on this particular issue, mainly on site preparation, fertilizer application and timber harvesting operations activities.
The purpose of this paper is to present the reduced impact timber harvesting (RITH) in the tropical forest plantation. The goals of RITH in plantation are as follows:
Timber harvesting in forest plantation can cause risk of damage as follows (Loeffler, 1989):
According to Elias (2000a), severe damage on soil and remaining stand will cause further extensive environmental damage in form of soil erosion, compacted and infertile soil, turbidity water and sedimentation, etc. and will decrease the future stand/trees quality and stand productivity (timber growth).
Timber harvesting is one of the major human interferences to the forest that causes environmental damage and should therefore be properly planned and executed. To minimize damage to the forest ecosystem in plantation under intensive forest management, landscape planning should be incorporated in the sustainable yield management.
Landscape Planning or sometimes called "Landscape Ecosystem Management" is a relatively new management concept (Hagner, 1999). This planning aims to:
For example: some forest areas should be left untouched as reserves for biodiversity conservation; steep slope could be placed into watershed protection zone; an important habitat for endangered plants or animals as a biological reserve zone.
Landscape planning is a critically important step in defining and locating the net productive area of plantation for timber production for a forest management unit. The timber production zone forms the area basis for determination of the annual allowable cut (Armitage, 1998).
Choice of timber harvesting technologies and techniques should be incorporated in sustainable yield management. This includes avoidance of damage to the remaining stand, retention and protection of trees which have potential for cultural and ecological values.
The improved timber harvesting technologies and techniques consist of (Elias, 2000a; 2000b):
- Felling technique and directional felling
-
Chokering technique and bunching
- Winching technique and controlled skidding
To enhance the successful application of improved technologies and techniques, needed are:
Technically, RITH is conducted as follows (Elias, 2000a):
1. The planning of timber harvesting should be completed long before the loggers enter the site. It must be developed comprehensively both strategically and operationally to ensure that planning mechanism protect all forest values at all times during timber harvesting (Strategic plans 5-10 years, operational plans 1 year and task plan).
2. In RITH operation, the activities should be conducted according to the timber harvesting plans and the standards or code of timber harvesting practices. Use low impact timber harvesting technologies, improved techniques and appropriate forest engineering.
3. After harvesting activities are over, the loggers are to take compulsory measures to prevent further environmental damage.
In forest plantation, there are two forms of harvest, namely thinning (young, small trees) and final harvest (old, large trees). Mobility in the stand is an important environmental feature. This applies in particular to thinning. The denser the stand the more difficult felling and processing of trees, bunching and skidding of timber. At clear cutting, which is a common form of final harvest there are usually no problems of crowding in the stands, hence mobility of machines are easier.
Operational plan
Time schedules for tree harvesting and other work are prepared for all of the units of treatment (harvesting) in the annual area. A large part of the harvesting work consist of felling, processing, skidding and hauling. Planning of harvesting operations includes the planning of road systems. Figure 1 shows an example of road systems and harvesting systems in the annual area (a), and an example of timber harvesting plan in one unit of treatment (b).
Directional Felling
Felling is actually a first transport step in direction which the feller can control by a skillful handling of equipment. If felling is done in the right direction (directed felling), a valuable free transport can be obtained.
Directed felling can also facilitate a concentration of timber to predetermine place in the stand or along the skidtrail for skidding. At directed felling, the logs (trees) are placed in a pattern which facilitates the subsequent operations. The pattern of felling should be compatible with the methods of subsequent processing and transport. Figure 2 shows an example of felling pattern.
Work Techniques and Equipment
Work techniques and equipment which are used for timber harvesting in plantation vary between different forms of harvesting systems, e.g. manual, motor manual and mechanized system. In some places, mainly in small scale plantations, handsaws, axes, chainsaws, oxen, buffaloes and small tractors are still the most common means of timber harvesting. On the other hand, timber harvesting in large-scale plantations is currently highly mechanized, using harvesters, feller bunchers, processors, forwarders, skidders and cable systems.
Figure 1a. Road Systems and Harvesting Systems (Elias, et.al. 2000)
Figure 1b. Timber Harvesting Plan of a Compartment (Elias, et.al. 2000)
Figure 2. Felling Pattern (Staat and Wiksten, 1989)
In terms of ground based machinery, the general trend is towards lighter, more mobile and computerized machines that can automatically optimise the value of harvested trees when cutting them into product assortments (cut-to-length method) and cause little damage to soils and remaining trees.
Work techniques, which are used to minimize damage on soil and remaining stand caused by timber harvesting e.g. are as follows:
Figure 3. Motor-Manual Felling Technique
Figure 4. Chokering Technique
Figure 5. Winching Technique by Tractor
The three figures below are three harvesting systems, which are recommended by the author to be implemented as RITH in the forest plantation of PT. Tanjung Redeb Hutani, Tanjung Redeb, East Kalimantan, Indonesia, in year 2001.
1. For flat to moderate terrain: Feller Buncher - Skidder Full Tree System
2. For steep terrain: Motor Manual - Bulldozer Full Tree System
3. Manual System: Motor Manual - Gravitation System, Short Wood System
For sustainable forest management of plantation, soil compaction and damage to tree roots, tree stems and tree crowns caused by timber harvesting should be minimized as much as possible. This can be obtained through:
1. Landscape planning of plantation area
2. Good road network system (haul road and skidroad network) and good harvesting plan.
3. Marking of "future" - trees in thinning
4. Wide rubber-tires or tracks and low impact timber harvesting technologies.
5. Implementation of directional felling (e.g. by using felling technique, see figure 3), felling pattern and improved timber harvesting techniques
6. Use lighter, more flexible machines, which have a low specific ground pressure
7. Implementation of reduced impact techniques (e.g. bunching by chokering method, winching as long as possible by tractor winch and skidding only on skidtrail, see figure 4 and 5)
8. On sensitive sites (e.g. moist or wet site) the machine movements should be limited on the skidtrails and the skidtrails should be reinforced with a layer of debris from harvested trees.
9. Education and training
Armitage, I. 1998. Guidelines for the Management of the tropical Forest. 1. The Production of Wood. FAO Forestry Paper 135. Forest Resources Division, FAO Forestry Department, Rome, Italy. 293p.
Elias. 2000a. Reduced Impact Timber Harvesting: Can Timber Harvesting and Environmental Protection Co-Exist?. Paper presented in Policy Seminar, Efficacy of Removing Natural Forests from Timber Production as a Strategy for Conserving Forests. 14 May 2000, Noosaville, Queensland, Australia. 6p.
Elias. 2000b. Reduced Impact Timber Harvesting in the Indonesian Selective Cutting and Planting System. Paper presented on Satellite Meeting of Research Group 3.05. Forest Operations in the Tropics, 6 August 2000, IUFRO XXI World Congress 7-12 August 2000, Kuala Lumpur, Malaysia. 7p.
Elias, et.al. 2000. Design of Timber Harvesting Systems for Tropical Plantation of PT. Tanjung Redeb Hutani, East Kalimantan. Joint Project of Faculty of Forestry, Bogor Agricultural University and PT. Tanjung Redeb Hutani, Bogor, Indonesia. 101p.
Hagner, S. 1999. Forest Management in Temperate and Boreal Forests: Current Practice and the Scope for Implementing Sustainable Forest Management. Working Paper: FAO/FPIRS/03. FAO Forestry Policy and Planning Division. Rome, Italy. 47p.
Loeffler, H. 1989. Forstliche Verfahrenstechnik (Holzernte). Lehrstuhl fuer Forstliche Arbeitswissenshaft und Verfahrenstechnik der Unversitaet Muenchen, Deutschland. 516p.
Staat, K.A.G. and N.A. Wiksten. 1984. Tree Harvesting Techniques. Martinus Nijhoftf/Dr.w. Junk Publishers. Dendricht-Boston-Lancaster. 371p.
