Determination of Rotation Period and Scheduling Harvesting and Replanting

Abstract of a presentation conducted by

Gimhani Danushika

Department of Forestry and Environmental Science

University of Sri Jayewardenepura, Sri Lanka

The objectives in forest management are often achieved by controlling the characteristics of a forest stand or set of forest stands in to influence the growth and yield of those stands. Further according to the objective of the land owner, it will change optimal rotation period of the plantations rotation. Most government owned plantations are following biological rotation to determine harvesting age of the plantation while commercial plantations are managed with economic rotation to get maximum economic benefit.

Harvest scheduling is a traditional exercise carried out by forest land managers on public and private lands. Public land management has characteristically balanced timber and non-commodity forest production while private land is going for optimal timber production. Therefore, industrial plantation establishment has been dominated by profit maximization and cost reduction by various strategies like economies of scale. Forest harvest practices in Sri Lanka are conducted by two ways called thinning and final harvesting. Final harvesting can be done in different ways such as clear cutting where all trees are felled, while selective cutting, shelterwood cutting and seed tree cutting are also possible. Thinning generate additional intermediate income from plantation while improving site quality for plant grooving by reducing competition.

Replanting of a harvested site is an important managerial activity which depends on social, cultural, economic and environmental considerations. According to management decision, it can use the same species as before or different species appropriate to the land. When replanting is carrying out, proper silvicultural practices should be maintained to gain the final harvest as expected levels. e:g: nursery establishment and maintaining, establishment of pits for planting, spacing, block wise replanting, weeding, fertilizing, irrigation, thinning and pruning etc. All these action should be conducted in proper way to maintain good replanting practice in harvested land.

Land Evaluation and Species-Site Suitability Determination for Forest Plantation Establishment

Abstract of a presentation conducted by

Sohani Vithanage

Department of Forestry and Environmental Science

University of Sri Jayewardenepura, Sri Lanka

Decisions about the use of land have always been a part of human society. Forestry planning has always taken account of the influence of conditions of land in taking management decisions. The approach and methods of land evaluation were developed in order to provide a systematic framework for assessing the effects of land on potential benefits of each land use. Land evaluation is based upon a comparison between land use and land type. Land use related to forestry can be broadly categorized as production forestry, conservation forestry, recreational forestry and community forestry. These major land uses can be further described in detail according to tree species, silvicultural methods, harvesting practices etc. The focus of land evaluation is to access the requirements and limitation of each of this land use and to compare this with the properties of land.

In the process of land evaluation land use requirements for each identified land utilization type is defined. Simultaneously, land qualities and characteristics of each land unit is described using literature surveys and ground surveys. These data is then coupled with economic and social data to develop a comprehensive comparison of land use with land. The outputs of land evaluation can be presented in terms of land suitability classifications or land suitability maps. At present, this procedure can be carried out with the help of computerized land evaluation systems and geographic information systems. In determining the species site suitability for forest plantation establishment, three aspects have to be considered. They are purpose of plantation, species availability and environmental conditions. For this process, depending on the species and sites, information survey can extend from local level to international level.

Land Evaluation and Species-Site Suitability Determination for Forest Plantation Establishment

Abstract of a presentation conducted by

Sohani Vithanage

Department of Forestry and Environmental Science

University of Sri Jayewardenepura, Sri Lanka

Decisions about the use of land have always been a part of human society. Forestry planning has always taken account of the influence of conditions of land in taking management decisions. The approach and methods of land evaluation were developed in order to provide a systematic framework for assessing the effects of land on potential benefits of each land use. Land evaluation is based upon a comparison between land use and land type. Land use related to forestry can be broadly categorized as production forestry, conservation forestry, recreational forestry and community forestry. These major land uses can be further described in detail according to tree species, silvicultural methods, harvesting practices etc. The focus of land evaluation is to access the requirements and limitation of each of this land use and to compare this with the properties of land.

In the process of land evaluation land use requirements for each identified land utilization type is defined. Simultaneously, land qualities and characteristics of each land unit is described using literature surveys and ground surveys. These data is then coupled with economic and social data to develop a comprehensive comparison of land use with land. The outputs of land evaluation can be presented in terms of land suitability classifications or land suitability maps. At present, this procedure can be carried out with the help of computerized land evaluation systems and geographic information systems. In determining the species site suitability for forest plantation establishment, three aspects have to be considered. They are purpose of plantation, species availability and environmental conditions. For this process, depending on the species and sites, information survey can extend from local level to international level.

Site Quality Improvement in Forest Management

Abstract of a presentation conducted by

Kushani Perera

Department of Forestry and Environmental Science

University of Sri Jayewardenepura, Sri Lanka

The productivity of a site for tree growth is usually evaluated on a stand basis. Considered in this way, site quality expresses the average productivity of a designated land area for growing forest trees. A common way of expressing relative site quality is to set up from three to five classes, or ordinal ranks, such as site I, II and III. The characteristics of each class must be defined to enable any area to be classified.

Site is a complex of physical and biological factors of an area that determine what forest or other vegetation it may carry. Sites get degraded due to many reasons, especially due to human induced problems such as land clearance, clear cutting and deforestation, agricultural depletion of soil nutrients through poor farming practices, livestock including overgrazing, dumping of non-degradable trash, plastics etc.

Site quality is a measure of relative productive capacity of a site for a particular species.Different site gives different growth response to different species. Site quality can be influenced by climatic factors, topographic factors, soil edaphic factors and competition. Monitoring site quality is important to match the species with the site, to estimate the quantity (harvest prediction) and the quality of the timber, to monitor overall ecosystem productivity, diversity and resilience and to check the habitat type and quality.

Site quality can be evaluated by both direct (actual crop production) and indirect factors (plant indicators, crop statistics, site factors).The quality of the original site can be improved by using several silvicultural practices like fertilization, improving the quality of soil by using cover crops, mulches and mechanical methods such as plouging, harrowing and deep ripping of the soil to improve aeration and at the same time mixing the organic matter content of the soil.

Forest Site Preparation, Planting and Early Management

Presented by

Liduli Livera

Forest management plan, a written scheme of management aiming at continuity of policy and action and controlling the treatments includes several steps namely demarcation of boundaries, site preparation, planting, irrigation, weeding, fertilizing, pruning, thinning and regeneration felling. When establishing a forest plantation, lay-out need to be prepared, then site preparation and finally planting operations are carried out. 

Preparation of lay-out includes confirming the location and shape of the forest plantation, preparation of road network plan, location of waterways, subdivision for fire breaks and access, spacing and mapping. Site preparation is done to create favorable growing conditions for seeds and seedlings, and to facilitate tree planting operations. This depends on the purpose of plantation, species to be planted, existing vegetative cover and soil conditions of the plantation site. Field activities which are carried out in site preparation are removal of the existing vegetation to reduce or eliminate competition and ground preparation to improve water retention and provide optimal soil conditions. Manual, mechanical, chemical methods and burning is usually carried out for vegetation clearance of the site. After vegetation clearance ground preparation is done by ploughing, sub-soiling, pre-planting harrowing, preparation of planting pits and terracing. For preparation of planting pits, planting design is important. Planting design decisions are obtained according to planting objectives and operational requirements associated with tending of planting.  Different site preparation practices are carried out for different types of land uses (eg: crop fields, fallow crop field with herbaceous weeds, woody species or shrubs, pastures and open areas, existing timber stands). 

After site preparation and planting operations, early management practices such as protection and cultural treatments are carried out. Protection need to be provided against wild and domestic animal predation, insect and fungi, and weeds. And also watering practices and fertilizing is done for plantations for proper management and to achieve ultimate forest management plan.

Pest Management in Commercial Forestry

Presented by

Madhushi Weerasinghe

Forest Pest can be defined as “any insect, disease or closely related organism which is harmful, injurious, or destructive to forest or timber”. All parts of a tree roots, stems, foliage, shoots and terminal leaders are vulnerable to attack by pests. Pest damage can range from slight damage that has no effect on the value of the harvested product to severe damage that stunts or kills the trees or reduces their market value. Tree pests include insects and mites, diseases, vertebrates, and nematodes.

There are several common pests that can be commonly seen in commercial forestry. In Tectona grandis the most common insects cause severe damage plantations are Leaf Skeletonizer (Eutectona machaeralis) and Defoliator (Hyblaea puera). In Swietenia macrophylla the most common pest is Mahogany Shoot Borer (Hypsipyla grandella). Moreover, there are insect pests in Eucalyptus grandis, such as Eucalyptus gall wasp (Ophelimus maskelli). Also some pathogens such as Leaf Spot Fungi (Cryptosporiopis eucalypti),Cylindrocladium Leaf Spot Blight-Fungi (Cylindrocladium reteaudii), Botryoshharia Canker (Botryosphaeria spp.) and Bacterial Wilt (Ralstonia solanacerum) are common. In Aquilaria malaccensis, Leaf spot Disease caused by Corynespora cassicola is common. Considering Sandalwood (Santalum album L.) there are some nursery diseases such as Damping off and Pre-emergence wilt.Also forest plantations can be damaged by Elephants and small mammals.

Managing tree pests effectively should be based on thorough consideration of ecological and economic factors. The pest, its biology, and the type of damage are some of the factors that determine which control strategies and methods should be used. Pest management decisions represent a compromise between the value of the product, the extent of the pest damage, the relative effectiveness and cost of the control measures, and the impact on the environment.

Here the concept of Integrated Pest Management (IPM) is mainly used. That relies on an understanding of the ecology of the pest, draws on this knowledge non-chemical approaches that will make the environment less suited to the development of the pest population. Integrated Pest Management practice may involve in the control program, the judicious and sensitive use of pesticides where necessary. There are five major steps in IPM. Monitoring is the first step. Monitoring forests and newly established plantations will help detect problems early, while there is still time to take action. Identification of pests and the diagnosis of pest damage is the second step of IPM. Threshold level is point at which the pest or its damage becomes unacceptable. The threshold level may be related to the beauty, health, or economic value of the tree crop and that comes as the third step of IPM. Selection of management strategy is fourth step and under this there are several management strategies such as, do nothing, cultural management, mechanical management, biological management and chemical management. Evaluation is the final step of IPM. It is very important to determine how effective the management and control tactics are. This information will determine whether any follow-up treatment is needed and will improve management strategies for next year.

Insect Management in Commercial Forestry

Presented by

Pabasara Gunawardane

All parts of a tree are vulnerable to attack by pests. Pest damage can range from slight damage that has no effect on the value of the harvested product, to severe damage that stunts or kills the trees or reduces their market value. Tree pests include insects and mites, diseases, weeds, vertebrates, and nematodes. 

Insects belong to the kingdom Animalia and in the phylum Arthropoda. Insects are categorised under the class Insecta. More than one million different species of insects have been identified. Some insects of orders such as Coleoptera, Lepidoptera, Hymenoptera, Hemiptera, Isoptera and Orthoptera are considered as pests in plantation forestry. Tectona grandis, Eucalyptus sp. Swietenia macrophylla, Santalum album and Aquilaria sp. are some of the major plantation species in Sri Lanka and the world

When consider about the insects, at least 174 species of insects have been recorded from the living teak tree. Most of these insects are not economically significant in their attacks. Teak defoliator (Hyblaea puera) causes severe defoliation and, hence, reduce growth rate of the tree. The larva of leaf skeletonizer (Eutectona machaeralis) feeds on the green leaf tissue between the network of veins, leaving the skeleton of veins intact. The most important stem borer in young teak plantations is Zeuzera coffeae. Another stem borer is Xyleutes ceramicus and it is found in older Teak plantations.

More than 920 species of insects are associated in Eucalypts. The most common pest problem of exotic eucalypts is mortality of saplings caused by root-feeding termites. Eucalyptus Gall Wasp has been reported in Sri Lanka in 2010 and it was successfully controlled by natural enemies of the pest insect.

Mahogany shoot borer (Hypsipyla robusta) outbreak is the most severe pest attack found in Mahogany. It is suggested that the relatively low level of attack in Sri Lanka may be due to good overhead shade where the trees have been planted.

Zeuzera coffease (red borer) Indarbela quardinotata (bark-feeding caterpillar) and Aristobia octofasiculata (heartwood borer) are some of the pests causing considerable damage to living Sandalwood trees. In agar plantation no such serious pests and diseases have been observed. A leaf-eating caterpillar (Heortia vitessoides) is considered to be the most destructive pest causing damage by complete defoliation of agar plantations. When compare with the other countries of the region the status of the pest outbreaks in forest plantations are lower in Sri Lanka.

In earlier attempts to control pest the commonly used method was to kill all the pests and with time plantation managers realized that pests need to be controlled only if they cause economic damages. The pest management concept is used to indicate management of the pest population to limit it to a tolerable level. With the advancement of knowledge and the science the concept of integrated pest management (IPM) has been introduced in order to manage the insects and pests in commercial plantations.

Lack of sufficient scientific research, inapplicability of sophisticated pest management methods used in developed countries and having the low attention on the pest management in forest plantation species by the government are major challenges in insect management in Sri Lankan forestry context.

Harvest Scheduling and Replanting in Comjmercial Forestry

Presented by

Arundathi Koliyabandara

Harvest scheduling is a traditional exercise that has been carried out by forest land managers on public and private lands alike. Industrial forest management has generally been distinguished by a much higher rate of intensification than has been the case on public lands. Whereas public land management has characteristically balanced timber and non-commodity forest production. Industrial plantation establishment has been dominated by profit maximization and cost reduction through economies of scale. Forest companies are now facing the challenge of scheduling spatially specific timber management activities over time to achieve their traditional objectives and the new environmental goals.

A good operational harvest schedule will satisfy the customers’ orders from areas of forest while minimising transportation costs. Also, areas of the forest with high quality trees will be used to provide high quality (high value) logs while lower quality areas will fulfil low quality (low-value) demands, minimising the conversion of high quality trees into low-value logs. Operational harvest scheduling can be very difficult. Good operational harvest scheduling is an activity where large immediate financial gains can be found. This is in contrast to tactical planning where gains will be seen in two to three years, or strategic planning with gains realised thirty or more years in the future. The immediate gains of a good harvest schedule are listed below. Harvesting costs are reduced, harvesting productivity is increased, larger volumes of high quality logs are produced and transport costs are lowered. Harvesting is done by two means as thinning and clear cutting. The conducting silvicultural system and the economics and demand are important factors when scheduling the harvest. There are commonly using harvesting systems as clear cutting, shelter wood, selection and coppicing. Clear cutting is where all of the trees in a stand are removed. Clear cutting diseased or insect-infested area  is often necessary to protect healthy trees. Shelter wood System is designed to remove certain trees and establish new growth under the protection of an over story of foliage. Sufficient mature trees are left standing to shelter the site until new growth is well established. The using silvicultural system depends on the objective.If a site is maintained to get timber and to maintain aesthetics selection is used. Coppicing is used when fuel wood is gained. If the prime objective is to get timber, clear cut is the method which will be practised.

The rotation is also an important consideration in harvest scheduling. It helps in deciding when to harvest the stand. There are main rotations used in commercial forestry which can be stated as technical rotation, biological rotation, income generation rotation and etc. Technical rotation is suitable for providing timber, wood with specific dimensions. In biological rotation the maximum volume production is expected. The stand is harvested when maximum mean annual increment is reached. Income generation rotation is a monetary rotation where the harvesting is scheduled at the time where highest average income is gained.

Replanting of a harvested site is an important managerial activity which depends on on social, cultural, economic and environmental reasons. Use of the same species or different species is a choice made by the management. When replanting is carrying out proper silvicultural practices should be maintained to gain the final harvest such as nursery establishment and maintaining, establishment of pits for planting, spacing, block wise replanting ,weeding , fertilising, irrigation, thinning and pruning. Intercropping can be practised based on the objectives.

In Sri Lanka some upcountry Eucalyptus plantations are clear-felled and replanted with more suitable Eucalyptus species. Some selected mature Pinus plantations too are clear-felled and replaced with, Khaya, Hora, Eucalyptus and Mix species. Dry Zone Teak plantations are re established mainly with Teak in the second rotation. However in the areas where elephant damaged is high, Khaya was planted instead of Teak.

Carbon sequestration potential of a plantation will be an added benefit and when scheduling harvest the area leaving for conservation and proper practices of harvesting should be planned.