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.

Challenges faced by the private sector in establishing teak plantations in Sri Lanka

Challenges faced by the private sector in establishing eak plantations in Sri Lanka

Abstract of a seminar presentation

Prabhani Jayasekara

Teak was introduced to Sri Lanka in 17th century by Dutch. It was widely planted in dry and intermediate zones after 1950s. Teak has a long history of systematic management. The earliest Teak plantations in Sri Lanka are traced back to the late seventeenth century. Teak planting, which was once mainly the domain of government forest departments, is today attracting the interest of the private sector. The private sector has taken advantage of technical developments has succeeded in attracting private individuals to invest in teak.

Many private companies involve in Teak planting in Sri Lanka such as:

Forestree Investments limited - a subsidiary of Access Group of Companies

Sadaharitha Plantations Limited

HELP GRRN “Wanasarana” Teak Plantation Project

Green Vision Lanka Private Limited

In Sri Lanka first private sector large scale commercially managed teak plantation was started by Help Green (Pvt) Ltd in 1998 with a unit which is equivalent to a land extent of 41.6 perches with 100 teak trees.

The expected final harvest of the private forest plantations are much shorter than that of the Forest Department plantations and therefore very high financial inputs are necessary to uplift such plantation conditions.

Among the major challenges faced by the private sector in establishing teak plantations, land unavailability, social issues, environmental issues, lack of scientific information and research, management problems and unforeseen catastrophes (insects, pests, animal damages, weeds, and uncontrolled fires) become prominent. Quality of timber cut from private sector plantations will also be a major issue because timber cut from old teak trees which grow slowly in natural forests is more durable and harder and teak from young trees grown in plantations may be more prone to splitting and water damage.

The private sector Teak planters have successfully identified many of the above mentioned challenges and they have taken actions in order to avoid economic loss which can be caused due to those issues.

Challenges faced in establishing khaya plantations in Sri Lanka

Challenges faced by the Forest Department in establishing khaya plantations in Sri Lanka

Abstract of a seminar presentation

Benica Jayasekara

Khaya senegalensis is the scientific name for khaya, which belongs to the Family Meliaceae. It is commonly known as African mahogany or dry zone mahogany. It’s a fast growing tree species in dry conditions and grows up to 20-30m in height. Timber of khaya is hard, dense and reddish brown in colour.

Khaya is one of the major timber species used by the Forest Department in reforestation programs in dry and intermediate zones of Sri Lanka. It was introduced from Africa during 1960’s. However, most of the khaya plantations of Sri Lanka are less than 10 years old.

The reasons for the use of Khaya by the Forest Department is the high demand for timber, fast growth rates in dry and intermediate zones, tolerance to poor site quality and resistance to heavy weed competition, harsh conditions and diseases and pests (except borer). Moreover the rural community prefers khaya over teak because khaya is morphologically more similar to the native species in Sri Lanka. In addition to those, wild elephants do not damage khaya trees.

According to the Forest Department, khaya was selected as the best tree species for the dry zone. There are however, a few challenges faced by the Forest Department in establishment of khaya plantations. Expensive seeds, low seed viability, fertilization, weeding, multiple shoots, porcupine damage, black twig borer attack, red stem borer attack and the forest fires as examples.

Forest Department had taken remedial actions for these challenges and still they are doing further studies to improve the khaya plantations. Still the khaya plantations in Sri Lanka are less than 10 years and therefore the Forest Department might face more problems with the time, because the rotation age of khaya is 30 years and still the yield tables for this species has not been prepared.

Status and possibilities on forest certification in Sri Lanka

Status and possibilities on forest certification in Sri Lanka

Abstract of a seminar presentation

Manuri Gamage

Forest certification found its roots in the concern over rapid tropical deforestation in the 1980s and the 1990s. It is a process which results in a written certification being issued by an independent third party, attesting to the location and management status of a forest which is producing timber. Forest certification also provides consumers with a credible guarantee that the product comes from environmentally responsible, socially beneficial, and economically viable sustainably managed forests.

Sri Lanka has adopted only FSC certification by an independent, non-profit organization, formed in an effort to establish a global system for certifying that products come from well-managed forests. Only three multinational certification bodies accredited by FSC are currently issuing certification in Sri Lanka.

At present, certification is confined mainly to the rubber plantation sector in Sri Lanka. Only four such companies currently hold FSC forest management certification, out of large-scale plantation companies in Sri Lanka. Forty-two percent of the country's plantations are owned by small holders. Therefore, this group plays a key role in the rubber industry as well as in supplying raw materials to wood-based industries. None of the small-scale rubber plantations in Sri Lanka are certified. Out of the many manufactures only nine companies have obtain the chain of custody certification.

Facilitating group certification for small rubber plantation owners to obtain forest certification, encouraging certified plantation owners to focus on high-end species such as teak and mahogany where there is great potential to capture price premiums, building awareness among plantation owners of advantages of obtaining the certification other than price premiums, seeking new export markets for the certified timber and timber products, obtain approval for the FSC National standards and implement within the country, encouraging local organisations to obtain accreditation from FSC as a certification body, developing an internal certification scheme with its own standards can be mentioned as some of the potentials in forest certification in the country.