This chapter describes the morphology, distribution, wood anatomy, andvariations of agarwood resin contents and resin content of Gyrinops walla endemic to Sri Lanka. We revealed for the fi rst time, this species, which populates the lower elevations of the wet zone of Sri Lanka in 2012. More importantly, the recently identifi ed species possesses agarwood-producing ability, similar to other species in the Thymelaeaceae family. Before this scientifi c discovery, G. walla was considered a least valuable species due to the very low stem density. Not much is known about this forgotten species; we intend to unleash its full potential as a new economic commodity to this country.
Modelling forest tree volumehas a long history due to its importance in forest management decision making. However, tree biomass prediction become more popular recently because it has a strong relationship with carbon sequestration. Over the years, numerous attempts were made to construct allometric models in predicting tree volume and biomass in Sri Lanka for different forest species. Volume and biomass estimation in forest trees in Sri Lanka can be divided into four main types, i.e., (i) use of specific models built for the target species, (ii) use of models originally built for different tree species from the target once, (iii) use of common/universal conversions and (iv) use of remote sensing related studies. The first three types, however, became more common because mainly remote sensing studies do not facilitate the biomass estimation at the tree level. Details of tree volume and biomass prediction models constructed for Eucalyptus grandis, E.torelliana, E. microcorys, Tectona grandis, Pinus caribaea, Khaya senegalensis and Alstonia macrophylla are discussed in this paper. Moreover, it discusses the result of a study conducted in a wet zone natural forest to predict species-specific individual tree biomass using diameter as the only explanatory variable. Finally it elaborates the issues faced in developing allometric equations in Sri Lanka.
Enhancement of carbon storage in tree biomass through the establishment of manmade forests is considered as a viable option to reduce atmospheric CO2 levels. Therefore the present study was conducted to estimate the biomass and carbon contents of the main stem of Tectona grandis Lin. f. (Teak) plantations in Sri Lanka using a non-destructive sampling technique. Harvesting of T. grandis is scheduled in Sri Lanka after 35 years of planting and therefore it is considered as a long rotation species. Allometric models were built to predict the variation of stem biomass and carbon of T. grandis with age and stem volume. A separatemodel was also built to predict the stem carbon change with the stem biomass.
23 T. grandis plantations were selected covering all three climatic zones, viz. dry,intermediate and wet of Sri Lanka for necessary data collection. Breast height diameter and height were measured for the sampled trees. Stem volume was calculated by a volume function which used diameter and height as the explanatory variables. Stem biomass and carbon contents were calculated converting those values of core samples obtained from the trees using a tree increment borer.
Results revealed that the average stem carbon content is 55% from the biomass. However,there were variations of this value for certain plantations of different ages. All allometricmodels built in this study had high R2 values which were over 90%.
Colombo city, the commercial capital of Sri Lanka and also a popular touristdestination is currently under a redesigning program coupled with landscapingactivities. Therefore it is important to investigate the spatial distribution of thegreen cover and its change over the time so that the findings can effectively be used to identify priority areas for restoring and revitalizing the greenery of the city. This study was conducted on mapping the green cover in all 47 wards of Colombo city for the years 1956, 1982, 2001 and 2010 by analyzing aerial photographs and IKONOS maps using Geographic Information Systems. Investigations were further extended to identify the vegetation cover% and its change in each ward during the 54 year study period. According to the results, the green cover of Colombo city declined from 35.67% to 22.23% from 1956 to 2010. In 2010, the highest green cover (49.65%) was reported in Narahenpita and only three other wards (Kirillipone, Cinnamon Gardens, and Thimbirigasyaya) had green cover over 30% of the total land extent. In contrast, the green cover was less than 10% for ten wards, i.e., Kochchikade North, Kochchikade South, Grandpas North, Masangasweediya, Panchikawatte, Fort, Gintupitiya, New Bazaar, Maligawatte, and Aluthkade East. Under the current redesigning plans, those ten wards should be given the priority to increase the green cover to re-establish a healthy environment. Expansion of built-up areas and road network can be surmised as major reasons for the gradual reduction of green cover in Colombo city.
Gyrinops walla is the only agarwood producing tree growing in Sri Lanka which is believed to be endemic. Agarwood is valuable resinous heartwood of Thymalaeaceae family. Present study is aimed to identify the characteristics of naturally formed agarwood type resins in G. walla stems. Samples were isolated from trees growing three different location in the wet zone of Sri Lanka. Naturally formed resinous part of wood was solvent extracted and analysed by GCMS. Further, the current study has developed an effective GCMS method to analyse agarwood type resin from G. walla. Tree diameters and the heights varied in the trees samples, which had no effect on resin formation. Resin contents were not significantly different between three populations although the chemical variations were considerably high. Among the 19 constituents identified by GCMS in the agarwood resins, free fatty acids and isopropyl naphthalene, 2-phenylethyl chromone compounds found to be common for most of the G. walla trees tested. Comonly found sesquiterpene compounds from the G. walla resin were Jinkhol, γ-eudesmol, valerenol and valerinal. Similar compounds have been reported in resin from Aquliaria spp. which is the more established source of agarwood. A future study would experiment on artificial resin induction methods and establishing plantations of G. walla to sustain its supply.
Enhancement of carbon storage through the establishment of man-made forests has been considered as a mitigation option to reduce increasing atmospheric CO2 levels. Therefore the present study was carried out to estimate the biomass and carbon storages of the main stem of Eucalyptus grandis using allometric relationships using the plantations of Nuwara Eliya and Badulla districts in Sri Lanka. Tree diameter and total height were measured for the samples trees and stem volume was estimated using a previously built individual model for the same species. Stem biomass was estimated using core samples and carbon was determined using Walkley-Black method. Finally the biomass values were converted separately to the carbon values. Non-liner regression analysis was employed for the construction of models which had age as the explanatory variable. Linear regression was used in order to build the models to predict the above ground and stem biomass and carbon using volume as the explanatory variable. For both linear and non-linear types, the model quality was tested using R2 and fitted line plots. According to the results, stem biomass and carbon values at the 7th year were 110.8 kg and 68.7 kg respectively. Stem biomass and carbon values at the 40th year were 1,095.8 kg and 679.4 kg respectively. Carbon content at the age 20 was 62.0% from the stem biomass. Exponential models were proven to be better than the logistic models to predict the diameter, height, stem volume, biomass and carbon with age. R2 values and the fitted line plots indicated that the selected models are of high quality. Linear models built to predict the stem biomass and carbon using stem volume also showed the high accuracy of these models which had R2 values above 97.9%.
Although the primary role of mangrove vegetations as photosynthetic primaryproducers, they are the basis of a complex and productive ecosystem. The mangrove forests in the tropics are threatened due to the immense human pressure especially through infrastructure development and aquaculture. Therefore information on the change of mangrove species diversity in different climate conditions and in the location of the forest is useful for restorationand identifying the conservation needs. The species diversity of six mangrove forests of three different climate regions was examined in this study. Species diversity in bottom, hydromorphic fringe, non-hydromorphic fringe and upland segments of each forest was alsostudied. There was no clear species difference in different climate regions. The highest diversity was reported in Negombo Lagoon of wet zone followed by Chilaw Lagoon of dry zone. Avicennia marina, Excoecaria agallocha, Lumnitzera recemosa and Rhizophora mucronata were found in all six forests. Aegicereas corniculatum, Bruigera gymnorrhiza and B. sexangula were found only in wet and intermediate zones. The lowest species diversity was identified in the bottom segments having R. mucronata, R. apiculata, Acanthus ilicifolius and Scyphiphora hydrophyllacea. The highest diversity was recorded in the non-hydromorphic fringe segment where 14 out of 15 totally recorded species were found in that region. Several threats to the mangrove forests, especially due to infrastructure developments and shrimp farming were also identified.
Eucalyptus grandis Hill ex Maiden (rose gum) is an introduced species to Sri Lanka from Australia. At present it has drawn attention of both public and private sectors due to the use as fuel, railway sleepers and sawn timber. This study focused on prediction of total height of E. grandis with age, which is an essential requirement in plantation management. Data were collected from 26 even-aged plantations, covering all favourable regions of Sri Lanka for the growth of E. grandis. At first theoretical equations were formulated with four possible transformations. Then parameters were estimated by fitting data at three different stages. R2 values and standard residual distributions were used as preliminary evaluations. Initially it was tried to model height using tree age as the only explanatory variable. Both linear and exponential functions were used at this stage. The resultant models, however, were not successful for both functions due to low R2 values. Therefore next attempt was made after partitioning the data into different site types using a simple site index. Three different site types were identified at this stage. Then linear and exponential functions were separately fitted to each site type to estimate parameters for different site types while keeping the same basic equation forms. This attempt was also not successful due to low R2 values, large outliers (for some site types) or incompatibility of the resultant models with biological reality. After the above unsuccessful attempts, the last step was conducted by pooling the data again and incorporating a second explanatory variable, site index. Other than multiple linear functions, exponential and logistic functions were modified by adding the second explanatory variable at this stage. Based on R2 and standard residuals, seven suitable models were selected. Then the estimated height values were fitted against an age series to test the distribution and compatibility with biological reality. Finally, after both qualitative and quantitative evaluations, the best model was selected to predict the height growth for E. grandis in Sri Lanka for all site types.
Forests are important ecosystems as they reduce the atmospheric CO2 amounts and thereby control the global warming. Estimation of biomass values are vital to determine the carbon contents stored in trees. However, biomass estimation is not an easy task as the trees should be felled or uprooted which are time consuming and expensive procedures. As a solution to this problem, onstruction of mathematical relationships to predict biomass from easily measurable variables can be used. The present study attempted to construct a mathematical model to predict the stem biomass of Pinus caribaea using the data collected from a 26 year old plantation located in Yagirala Forest Reserve in the low country wet zone of Sri Lanka. Due to the geographical undulations of this forest, two 0.05 ha sample plots were randomly established in each of valley, slope and ridge-top areas. In order to construct the model, stem wood density values were calculated by using stem core samples extracted at the breast height point. Stem volume was estimated for each tree using Newton’s formula and the stem biomass was then estimated by converting the weight of the known volume of core samples to the weight of the stem volume. Prior to pool the data for model construction, the density variations along the stem and between geographical locations were also tested.
It was attempted to predict the biomass using both dbh and tree height. Apart from the untransformed variables, four biologically acceptable transformations were also used for model construction to obtain the best model. All possible combinations of model structures were fitted to the data. The preliminary model selection for further analysis was done based on higher R2 values and compatibility with the biological reality. Out of those preliminary selected models, the final selection was done using the average model bias and modeling efficiency quantitatively and using standard residual distribution qualitatively.
Santalum album L., native to India, Indonesia and Sri Lanka, is the best quality oil yielding species among all members of the genus Santalum. Due to the high value of heartwood and oil, this species is illegally harvested in large numbers which can lead to possible extinction. Although it has been named as a protected species since 1964 in Sri Lanka, still the illegal harvesting is very high and the regeneration of this valuable resource is also hindered due to the slow growth rates and low germination rates. Moreover, all Santalum species are hemi-parasitic in nature so that they absorb certain nutrients from other plant species through the connections made via roots. Due to the decline at rapid phase, it is essential to take certain steps to restore S. album resource in Sri Lanka before it becomes almost extinct. Following this objective, the present paper describes the current distribution of S. album in Sri Lanka and attempts made for enhancing the germination rate and initial growth rate of the seedlings by means of seed treatments, seed viability loss and the effect of different host species at the seedling stage. According to the recent findings, S. album has a wider distribution in Sri Lanka despite of the belief that the best oil yielding trees grow in Badulla-Welimada region. According to the results of the experiments conducted, 0.05% Gibberellic acid was identified as the best seed treatment and the seed viability loses rapidly with the storage time. Desmodium triflorum, Mimosa pudica and Clitoria ternatea were identified as the best host species for the seedling stage of S. album.
Enhancement of carbon storage through the establishment of man-made forests has been considered as a mitigation option to reduce increasing atmospheric CO2 levels. Therefore the present study was carried out to estimate the biomass and carbon storages of the above ground parts of Eucalyptus grandis growing as plantations in Sri Lanka. In addition, it was expected identify the variation of biomass and carbon storage in the above ground parts of the selected species with stem volume.
E. grandis plantations were selected using FORDATA database of the Department of Forest Conservation of Sri Lanka. Those plantations were selected from Badulla and Nuwara Eliya Forest Divisions where the selected species is growing in large scale. Using the random sampling, tree diameter, total height, lower and upper crown height were measured. Crown measurements were obtained using a digital photographic analysis method. Number of branches in each tree was counted. Stem volume was estimated using the breast height diameter and tree height using a previously developed individual stem volume prediction modes for the same species. Stem and branch biomass values were estimated using extracted core samples and the crown biomass was separately estimated. For this reason, crown volume was estimated using equations of conoid, paraboloid or hemisphere after determining the crown shape with the digital photographic analysis. Stem and leaf carbon were determined using Walkley-Black method and finally the biomass values were converted separately to the carbon values for different above ground parts of the tree.
Non-liner regression analysis was employed for the construction of models which had age as the explanatory variable. Both exponential and logistic curves were tested for this purpose. Linear regression was used in order to build the models to predict the above ground and stem biomass and carbon using volume. For both linear and non-linear types, the model quality was tested using R2 and fitted line plots.
According to the results, above ground biomass and carbon values at the 7th year were 138.8 kg and 82.9 kg respectively. Annual biomass increment for E. grandis was 33.1 kg. Above ground biomass and carbon values at the 40th year were 1,323.5 kg and 822.1 kg respectively showing annual carbon storage of 22.4 kg. 65.9% of the above ground stem biomass was carbon.
Exponential models were proven to be better than the logistic models to predict the diameter, height, stem volume, above ground biomass, stem biomass, branch biomass, crown biomass, above ground carbon, stem carbon, branch carbon and crown carbon with the age. The R2 values and the fitted line plots indicated the strength of the selected models. Linear models built to predict the above ground biomass, stem biomass, above ground carbon and stem carbon using stem volume also showed the high predictability of the models. R2 values were above 97.9% for all linear models. Therefore the models built in the present study can be used to estimate the stem and crown growth, above ground biomass and above ground carbon for E. grandis in effective manner.
Santalum album is a native plant of Sri Lanka and its value and quality have been used to show the characteristics of good in the ancient literature. It naturally distributes in the area where mean annual the temperature is between 22.5-25.0 0C; mean annual rainfall is between 1,000-1,500 mm; and at the elevation between 500-1,000 m above mean sea level. However, recent research has proven that S. album grows in wider climatic and elevation regions than the above with a growth rate of 0.3 to 1.0 cm of dbh and 0.3 to 1.0 m of height per year. S. album has been listed as a protected species in Sri Lanka under the Flora and Fauna Act of 1964 and again with the recent amendment of the year 2009. Felling and harvesting have become a lengthy procedure due to this reason and therefore planting is unpopular among the general public. The major threat to the existing trees is the illegal harvesting which heavily caused the resource depletion. Due to the severity of the illegal harvesting, protection has become useless and owners tend to sell trees before the maturity. However, establishment of commercial S. album plantations has become popular and fast growing among the private sector since recent years. This activity became accelerated since 2010 as one company started establishing plantations in different climatic zones of Sri Lanka after some silvicultural studies. Limited availability of lands, poor land quality and poor access to the available lands are the current problems faced in establishing such plantations. S. album research has been stated recently in Sri Lanka and studies on oil quantity and quality, seed germination and seedling hosts were already completed
Santalum album (Indian Sandalwood) is found in the mountainous regions of the intermediate zone of Sri Lanka. Few studies have been conducted on sandalwood ecology in this region, and ours is the first recorded study of essential oil content and chemical composition of heartwood. We harvested two trees with State permission and took cross-sections for analysis. We demonstrated a difference in the heartwood formation and oil yield of the trees. The composition of the oil was found to be consistent between trees and along the trunk of the tree. Main aromatic compounds were santalols and other compounds are recorded in lesser quantities. Results of this study comply with the other published work on sandalwood elsewhere. This initial study on S. album in Sri Lanka provided promising results for the future of sandalwood agroforestry.
One of the main methods of establishing teak (Tectona grandis L. f.) plantations in Sri Lanka was through farmer woodlots. Therefore the present study was conducted with the objectives of identifying the growth of teak in different farmer woodlots in dry and intermediate zones of Sri Lanka, indentifying the management issues and measuring the availability and effects of selected soil nutrients on growth. 17 teak plantations of age ranging from 8 to 13 years managed through farmer woodlots were selected for this purpose. Those plantations were selected from Anuradhapura and Polonnaruwa forest divisions to represent the dry zone and from Kurunegala forest division to represent the intermediate zone. Three farmer woodlots from each plantation were randomly selected for the data collection and 10 farmers were interviewed from each plantation via a pre-tested questionnaire survey. Dbh and total height were measured from the trees in the sample plots and soil samples were collected to measure soil pH, bulk density, organic carbon, nitrates, phosphorus, potassium, magnesium and calcium.
It was identified that the growth of the selected plantations were less than that of the height class II of teak yield tables published by the Sri Lanka Forest Department. A significant correlation was not identified between soil chemical parameters and the growth. Further, the tested nutrients were available in very low levels in the tested sites.
The results of the questionnaire survey revealed that, 100% of farmers needed to extend the present 25 year lease agreement by 5 to 50 years to obtain more income. Moreover, 98% was willing to continue the programme for another cycle. However, they face problems such as poor site quality, wild elephants, fire and insect damage in managing their woodlots. In addition to that, lack of technical support was also highlighted.
In order to manage the forest plantations, yield tables play a vital role by providing the necessary growth information against the age for different site types. Although the complex growth models have become popular recently, still yield tables are very widely used for prediction of growth and yield.
Alstonia macrophylla Wall ex G. Don commonly known as hawari nuga was an introduced species to Sri Lanka from Malaysia. Although the timber quality is not valuable as that of most of the commercial timber species in Sri Lanka, the Forest Department and the private sector have established a considerable amount of plantations of this species in the low country wet zone due to its fast growth rate and high adaptability to different site types. In addition to that, A. macrophylla is growing as individuals and small blocks in homegardens, barren lands and edges of natural forests. However, at present, a yield table or any other method is not available for this species to predict its growth for different site types.
Therefore the present study was conducted with the objectives of classifying the site quality of A. macrophylla plantations and to construct yield tables for those site classes. For this reason, 23 even-aged plantations and 29 blocks (non-plantations) were selected from Galle, Kalutara, Matara and Ratnapura districts. The selected plantations varied in age from 5 to 22 years and the age could not be identified for the non-plantations due to the unavailability of records or due to the growth of trees of different ages. The data collected were the dbh, total height, timber height, crown dimensions and the necessary data for the calculation of stem volume by using Newton’s formula.
In order to classify the sites, a top height related index was used and it was possible to identify two different site types for A. macrophylla. However, there were no adequate amount of plantations for the site class I and therefore a yield table could not be constructed for that site although all the necessary growth models were constructed in this study.
In order to construct the yield table, first a height-age relationship was built to predict the total height at any age. Then the tree dbh was modelled against total height so that the dbh of any age can indirectly be predicted by using the dbh-height model. Using dbh and total height another model was constructed to predict total stem volume and in addition to that, a merchantable volume prediction model was built from dbh and total height. In addition to the above models used for the construction of yield tables, a separate simple volume prediction model which is independent from the site quality was built for the trees growing as non-plantations.
Other than the untransformed variables, four transformations were used in this study for the selected candidate variables in order to identify the best models with the highest accuracy. Data were fitted to both linear and non-linear forms and the preliminary selection of the suitable models were done based on the R2 value. In order to identify the best models among the selected ones, both qualitative (standard residual distribution, fitted line plots) and quantitative (average model bias, mean absolute difference and modelling efficiency) tests were utilised. For the finally selected models the biological reality was also tested. As a rule, it was expected build the models of same structure to predict the similar variable for all site types. A validation test was also conducted with independent data for the finally selected models to identify the suitability for the use in the field.
The selected models to construct the yield table were very low in bias. However, certain models did not indicate a very high R2. The reason may be the high variability of the data in each age. Finally a yield table was prepared for the site class II with the final harvest at 20 years after planting. The recommended initial spacing was 2.5x2.5 m and also two thinnings were recommended in between.
In addition to the above, the site quality of A. macrophylla growing in the selected four districts was further classified using GIS in order to prepare a site quality map.
Forests in Sri Lanka contribute to the mitigation of global climate change through sequestrating a net amount of carbon dioxide and also maintaining carbon stocks as forest biomass. This study was conducted using an empirical method to understand the biomass and stored carbon by forest plantations in Sri Lanka. Further, in this study, the possibility of predicting the above ground tree biomass and carbon of Pinus caribaea (Morelet) was investigated. A 27 year old P. caribaea plantation was selected from the Low Country Wet Zone in Sri Lanka and the data were collected using 0.05 ha sample plots. Without felling trees, a core sample was obtained from the stem and biomass and carbon of that sample was used to estimate the stem biomass and carbon through volume measurements. The canopy biomass and carbon were estimated using samples of primary, secondary and tertiary branches and leaves. The total above ground tree biomass and carbon were estimated by adding the stem and canopy values together.
It was found that, for 27 year old P. caribaea, the average above ground tree biomass was 368.9 kg and the carbon was 215.9 kg which is 58.5% from the biomass. The amount of carbon in the canopy was 64.5% from the canopy dry mass. The carbon percentages of the primary, secondary and tertiary branches and leaves were 61.7, 59.1 and 79.6 respectively. The total above ground tree carbon for a 27 year old P. caribaea plantation was 103.6 T ha-1.
Then regression models were developed to identify the relationships of biomass and carbon with stem volume. A relationship between biomass and carbon was also developed for the selected species. Finally, mathematical models were developed to predict biomass and carbon using some other tree variables such as diameter and height, without felling the trees.