Establishment and maintenance plan for Cedrela toona

Establishment and maintenance plan for Cedrela toona

Abstract of a seminar presentation

Based on a hypothetically formed plantation company

Sadeepa Senarath Yapa

Establishment and maintenance plan for Cedrela toona is prepared by a company named as Evergreen Plantation Limited who is willing to establish a commercial toona plantation in a barren land of upcountry. The company is mainly targeting to obtain a maximum profit by selling toona timber which is popular as a veneer and used for decorative purposes.

This large tree species is a moderate shade demander whose best growth is at the elevation of around 1200m. As we have a barren land of 50ha with no shade trees we have planned to plant Acacia decurrens two years prior to planting toona in the spacing of 4.5m*4.5m. These Acacia plants will be removed completely form the site 7 years after planting them to provide more space for the growing of toona trees.

Land Preparation, planting and other treatments such as weeding, fertilizing, thinning, pruning and pest and disease control will be carried out in a very careful manner in order to obtain maximum volume of timber at the end of the rotation age of 30 years. Fencing and fire lining will be done in the early stages of the plantation establishment to prevent manmade and natural damages to the plantation.

Final stock will be 225 trees per ha which will be removed by shelter wood system to minimize environmental damages which can be occurred in clear felling. Selected trees will be felled, extracted the moved to roadside and transported to the local market.

Effect of farmer woodlots on farmers

Evaluation of farmers woodlots in the aspects of growth and effect on farmers

Thilina Jayarathne and Upul Subasinghe

Paper presented for the 14th International Forestry and Environmental Symposium 2009

The total forest cover of Sri Lanka is estimated as 32% from the total land area. More than 50% of this area lies in the dry zone where the original forests have been cleared drastically. Plantation forests are therefore being established particularly with exotics as local species are very slow growing, despite their very high timber value. Teak was the first exotic species introduced to Sri Lanka by Dutch in the 17th century for replanting purpose. Other than planting by Forest Department of Sri Lanka, the other methods of establishing teak plantations were community forestry projects (CFP), and now by participatory forestry projects (PFP).

The objective of the present study was to evaluate the farmers' woodlot programmes to identify the effects on farmers. For this purpose, a questionnaire survey was conducted to obtain information on their socio-economic status and management constraints from Anuradhapura, Thambuttegama, Kekirawa Ranges (Anuradhapura Forest Division), Habarana Range (Polonnaruwa Forest Division) and Galgamuawa Range (Kurunegala Forest Division). The questionnaire was distributed among randomly selected ten farmers of each plantation (altogether 214 plantations).

The results revealed the inadequacy of current lease agreement (25 years) and 100% of the respondents wanted to have an extension varying from 5 to 50 years. Moreover, 98% of the total respondents agreed to implement this programme for a second rotation. Farmers have been given a proper guidance by the government officers during the initial establishment stage of the farmer's woodlots. However, it has become inadequate with the time, especially when pruning and thinning are required. Elephant's damages and lack of water are the major problems faced by the most of the farmers. However, according to the farmers, there were minimum elephant damage after plantations become naturalised as witnessed in the Rambukwewa plantation in the Kekirawa range.

Results and direct observations also indicated that some lands given to establish farmers' woodlots are marginal lands for plant growth. Most of lands also indicated frequent fire and erosion. Since teak needs comparatively more nutrients for plant growth, it is recommended to evaluate the chosen sites for (i) the available nutrient levels, (ii) required timber species to match the site quality and (iii) the required growth rate.

In order to enhance the income of the farmers, it is recommended to start the second cycle of woodlots soon after completing the present one, perhaps with better management techniques. However, the plantations vulnerable for elephant damages should not be replanted using teak unless there is an effective protection system. Otherwise such plantations should gradually be converted to natural dry zone forests by the local species such as Azadirachta indica and Tamarindus indica.

Timber production in high density planting of Rubber

Timber production in high density planting of Hevea brasiliensis (Rubber)

Kelum Silva, Upul Subasinghe and Lakshman Rodrigo

Paper presented for the 14th International Forestry and Environmental Symposium 2009

The demand of natural rubber has increased continuously with the increase of population and living standards of the human being. Rubber plantations are also a major source of timber and fuels wood. In order to meet the continuous increase in demand for latex, timber and fuelwood, the productivity of rubber plantations should be increased. Whilst producing high yielding clones for improved latex and timber yield per tree which is a long-term process in perennial crops, planting density could be adjusted to obtain high productivity in rubber plantations. The present level of planting density of rubber in Sri Lanka has been decided on the experiments conducted with the genotypes which are not in common use at the moment. Therefore the present study was aimed to identify the suitable planting density for the recently developed and commonly used genotypes of rubber. This paper is focused to assess the timber production of rubber with respect to high density planting.

The experiment was set up in Rathnapura District of Sri Lanka in 1992. Rubber was planted in three high densities, i.e., 600, 700 and 800 trees per hectare. Also three genotypes (clones), i.e., RRIC 100, RRIC 110 and RRIC 121 were incorporated with the statistical design of split plot where the planting densities were laid as the main plot whilst clones were in the sub-plots. Five trees in each sub-plot were randomly selected and used for the measurements of total tree height (TH), crown height (CH), thickness of the untapped bark (BT) and tree diameter at breast height. Thereafter, stem volumes were determined using the Newton’s formula.

Both TH and CH did not vary significantly among the planting densities tested. Although not statistically significant, there was a marginal decrease in tree diameter with the increase in planting density. Irrespective of the clone used, BT and mean merchantable timber volume per tree decreased significantly with increase in planting density. Nevertheless, this decrease was compensated by the increased number of trees in high densities resulting in comparable level of merchantable volume per hectare among different densities. Total stem volume per tree remained same among four densities tested with that total stem per hectare increased significantly with the increase of planting density. Therefore, higher densities are more useful in the industries of fuelwood, pulp, MDF boards etc. Among the clones tested, the clone RRIC 212outperformed in growth and timber production. The clone RRIC 110 was infected with the Corynespora disease hence showed poor performance in all densities. Despite the increase in total timber production with the increase in planting density, overall financial viability of different densities is to be assessed considering all cost components and valuing both timber and latex produced before making any firm recommendation.

Establishment of relationships of growth at 7-year old mahogany trees with selected site factors

Establishment of relationships of growth at 7-year old mahogany trees with selected site factors in low country wet zone, using GIS as a tool

Himesha Randeni and Upul Subasinghe

Paper presented for the 14th International Forestry and Environment Symposium 2009

Mahogany (Swietenia macrophylla) is an exotic tree, which is heavily adapted to the climatic conditions of wet and intermediate zones of Sri Lanka. Although the state sector manages mahogany with longer rotations, private sector expects to achieve the maximum timber yield within a shorter period. Due to the land scarcity, many of these mahogany plantations have been established in barren and rubber uprooted lands which were heavily degraded. Therefore the soil conditions and site factors directly affect the growth of the mahogany within short rotations.

The present study was carried out in a 7 years old mahogany monoculture plantation established in Gomaragala, in low country wet zone of Sri Lanka to find out the effect of soil and site factors to the mahogany tree growth. Extent of this forest is 20.7 ha and it is managed by a private plantation company. This forest has been divided into 2 lots for the purpose of administration and further divided into 240 plots of 20 perch each.

In order to identify the relationships, tree dbh and height were used as growth parameters. Slope, bedrock establishment and terrain were selected as selected site factors. The growth parameters (i.e.dbh and height) were measured for all the trees in plantation (one measurement from each plot). Slope and terrain as geographical parameters were measured of all 240 plots in the entire plantation.

Since the regression based methods were not adequate for both qualitative as well as quantitative parameter analysis, GIS based analysis was decided to use for the present study, using ArcView 3.3. In order to create digital maps, the survey plan of the selected forest was digitized and georeferanced using 10 ground control points collected by a GPS data receptor. Then the georeferanced base map was digitized to demarcate all the plots and other land marks. After that different maps were prepared in vector form separately for each parameter. However, for the analysis, all these vector layers were converted to raster layers. Raster layers were then reclassified and overlaid two or three layers at a time with the growth parameters to identify the effects. Then map analysis was completed to make decisions regarding tree growth in different site factors.

Results revealed that there are significant relationships between tree growth and the selected site parameters. However, the best conditions for the mahogany tree growth in the particular area are the slope between 11⁰-24⁰, and shallow bedrock prevalence and stony terrain.

Change of crown diameter with dbh of mahogany

Change of crown diameter with dbh of Swietenia macrophylla (mahogany)

even-aged monocultures

Shanika Lakmali and Upul Subasinghe

Paper presented for the 14th International Forestry and Environment Symposium 2009

Mahogany is one of the renowned timber species for its beautifully grained, hard and red-brown wood. It is an introduced timber species, dominated in Sri Lankan forest plantations with fast growth rates and higher timber value. Mahogany plantations are widely established in the intermediate zone and low country wet zone in Sri Lanka. Recently, private sector has started to establish of mahogany monocultures with shorter rotations to gain high income.

Due to the lack of research studies on mahogany, the objective of the present study was to establish an empirical model to predict crown diameter accurately using dbh. For this purpose, data were collected from 16 mahogany monocultures in Kalutara, Ratnapura and Matale districts. In order to represent the whole plantation, sixty trees were selected from good, moderate and poor areas from each plantation.

In order to build a reliable model, theoretical basic structures were developed assuming the crown diameter is a function of tree dbh. This basic structure was fitted to the data as linear, exponential, and logistic form separately for different growth types. In addition to the untransformed variables, transformations were also made whenever possible. Suitable candidate models were preliminary selected by R2 and residual distributions. After further analysis, it was proven that the best results were given by the logistic model structure for good, moderate and poor site types (R2 = 92.0%, 71.4%, 65.9% respectively). In order to eliminate the difficulty of using separate models for different growth types, the possibility of using a common model for all growth types were tested. For this reason, one way ANOVA was used for residuals of different growth types generated after fitting respective models. Results indicated that it was possible to use a common model and therefore the logistic form was re-fitted to pooled data.

The final model was “crown diameter = 0.645 + 2.682 / (1+exp (-0.356 (dbh –7.749)))” and it had a R2 of 60.9%.

Establishment of relationships of growth with site factors and some selected soil parameters of a selected 7 years old mahogany plantation in Eheliyag

Establishment of relationships of growth with site factors and some selected soil parameters of a selected 7 years old mahogany plantation in Eheliyagoda DS, using GIS as a tool

B.Sc. Dissertation

Himesha Randeni and Upul Subasinghe

Mahogany (Swietenia macrophylla) is an exotic tree, which is heavily adapted to the climatic conditions of wet and intermediate zones of Sri Lanka. Although the state sector manages mahogany with longer rotations, private sector expects to achieve the maximum timber yield within a shorter period. Due to the land scarcity, many of these mahogany plantations have been established in barren and rubber uprooted lands which were heavily degraded. Therefore the soil conditions and site factors directly affect the growth of the mahogany within short rotations.

The present study was carried out in a 7 years old mahogany monoculture plantation established in Gomaragala, in low country wet zone of Sri Lanka to find out the effect of soil and site factors to the mahogany tree growth. Extent of this forest is 20.7 ha and it is managed by a private plantation company. This forest has been divided into 2 lots for the purpose of administration. However, for the sales purposes it has been divided into 240 plots.

In order to identify the relationships, tree dbh and tree height as growth parameters; slope and terrain were selected as geographical factors as well as soil texture, soil organic carbon level and soil pH levels were selected as soil parameters. The growth parameters (i.e.dbh and height) were measured of all the trees in plantation. Slope and terrain as geographical parameters were measured of all 240 plots in the entire plantation. Soil parameters namely soil pH, soil organic carbon and soil texture were measured for systematically selected 50 plots out of 240 plots to represent the entire plantation. There are some qualitative parameters namely tree growth, terrain, presence of bedrock, included into the present study. These were usually assessed to give a single value for each plot.

Since the regression based methods was not adequate for both qualitative as well as quantitative parameter analysis, GIS based analysis was decided to use for the present study, because it serves as an analytical and decision supporting tool. ArcView 3.3 was used for this purpose. In order to create digital maps, the survey plan of the selected forest was digitized and georeferanced by main 10 ground control points collected by a GPS data receptor. Then the georeferanced base map was digitized to demarcate all the plots and other land marks. After that different maps were prepared in vector form separately for each parameter. However, for the analysis, all these vector layers were converted to raster layers. Raster layers were then reclassified and overlaid two or three layers at a time with the growth parameters to identify the effects. Then map analysis was completed to make decisions regarding tree growth in different site factors and soil conditions with similar other environmental conditions. Since the soil pH, soil organic carbon level and soil texture were measured in selected 50 plots out of 240 plots, the raster layers were interpolated for entire area.

Results of the present study revealed that there are significant relationships between tree growth with the selected parameters. However, the best conditions for the mahogany tree growth in the particular area are the slope between 11⁰-24⁰, soil pH level bellow 4.0, soil organic carbon range between 9.0%-14.0%, soil with sand between 50%-70%, shallow bedrock prevalence and stony terrain.

Changes of branch and crown characteristics with stem parameters and age of Swietenia macrophylla even-aged monocultures

Changes of branch and crown characteristics with stem parameters and age of Swietenia macrophylla (mahogany) even-aged monocultures

B.Sc. Dissertation

Shyanika Lakmali and Upul Subasinghe

Growth predictions in the plantation forestry play a vital role in order to maximize the future gains specially in the field of economy. Plantations of mahogany monocultures in private sector directly focus in the timber production and thereby the financial gain. Tree growth is accompanied with the photosynthesis process and it increases the stem parameters of the trees. Therefore there is a close relationship between crown development and tree growth. In addition to that, crown growth causes a competition after the canopy closure in the forest plantations.

The main objective of the present study was to establish a series of empirical models for predicting the relationships between stem, crown and branch parameters. In addition to that an attempt was taken to predict the above parameters with age. It was expected to use those relationships to prepare a pruning schedule for mahogany monoculture plantations in Sri Lanka.

In order to achieve the objectives, data were collected from 16 mahogany monocultures in Kalutara, Ratnapura and Matale districts. In order to represent the whole plantation, due to growth differences, sixty trees were selected from each of plantation as twenty trees from each good, moderate, and poor growing areas. The measurements were taken including dbh, total tree height, crown diameter, height to the first branch, height to the second branch, branch lengths and base diameters up to two branches.

Regression analysis was employed to build the suitable relationships between related variables. Both linear and non-linear regression equations were tested for each relationship using MINITAB and GENSTAT statistical software. In order to obtain the best equations, both qualitative (R² ) and quantitative (residual distribution and fitted line plots) were used. Initially, the data were grouped as good, moderate and poor growth types. Then different theoretical model structures (linear with untransformed and transformed variables, exponential and logistic) were separately fitted to those data. After that the best model was selected for each relationship for each growth type. At this point, it was a must to select the similar model structure (with different regression parameter sets) for each relationship in each growth type.

According to the results, crown and branch variables were highly correlated with the stem variables such as dbh and total height. Therefore the predictions of the crown and branch growth could be expressed by using dbh and total height. It was not possible to build linear relationships and

In order to predict the required variable, 12 non-linear models were constructed. Then the possibility of using a common model for all growth types was tested for each variable with pooled data. However, only three models out of 12 models proved the possibility of using as common models for all growth types. The rest of models were therefore decided to use as growth specific ones.

Finally using those models, a pruning schedule was prepared for different growth types of mahogany monocultures in Sri Lanka.