Corticolous lichens as indicators of forest management regimes in the Dotalugala area of Knuckles mountain range – Sri Lanka

G. Weerakoon1, S. Somaratne2, P.A. Wolseley3 and S.C. Wijeyaratne1
Department of Botany, University of Sri Jayewardenepura, Sri Lanka
Department of Botany, The Open University of Sri Lanka
Department of Botany, The Natural History Museum, United Kingdom

Lichens have been widely considered as bioindicators of forest health and ecological continuity as well as atmospheric pollution. The use of lichens as bioindicators in tropical zones has been hampered by the lack of taxonomic and ecological knowledge. The purpose of the study was to assess the variation of lichen diversity in different forest management regimes under different environmental conditions on the basis that their potential uses as bioindicators of environmental alterations in different habitats in the Knuckles mountain range. The sampling sites were chosen to include pristine forest of montane and sub-montane and six different disturb vegetation types. Lichen species, their frequency and cover values were recorded together with environmental parameters in 20 sites of 100 m2 plots. Ten trees were sampled randomly in each plot. The collected data were analyzed to assess the relationship between lichen diversity and environmental conditions in different forest management regimes using one-way analysis variance, least significant difference- LSD (mean comparison) and Regression tree analysis.

There were 192 lichen species recorded from the natural vegetations, where as 148 lichen species present in the disturbed vegetation types. The results of the study have shown that there is a considerable variation in the lichen diversity along different vegetation types and their degree of disturbance. The statistical analysis revealed a significant variation in lichen diversity between the disturbed and undisturbed vegetation in the area (F = 6.213, df = 1; p ≤ 0.05). Similarly, lichen diversity in different vegetation types also indicated a remarkable variation (F =3.21, df = 7; p ≤ 0.05). The results obtained from regression tree analysis indicated that there were three important variables that determined the lichen diversity of the study area; type of vegetation, altitude and association with other cryptogamic communities.

There are distinct lichen communities associated with tree boles in disturbed forests including weedy taxa and low diversity with few forest lichen species.  The analysis of epiphytic lichen diversity showed significant difference in the natural vegetation and disturbed vegetation.

This may be due to the heterogeneity of microclimatic conditions and specialist lichen communities associated with pristine tropical forests. Thus, there is utmost importance to identify lichen communities that can be use as indicators of reflecting forest health for the purpose of sustainable management.

A Boolean Network Model to test ecosystem resilience under elevated nitrogen deposition and drought

K.  Naithani and E. A.H. Smithwick
The Pennsylvania State University, University Park, USA

Elevated nitrogen deposition alters soil biogeochemistry and associated ecosystem processes that can lead to plant mortality and decline in stand productivity. Understanding the effects of elevated nitrogen deposition as a result of different land use practices is critical for predictive understanding of ecosystem productivity and resilience. Nitrogen cycling in terrestrial ecosystems is a nonlinear, complex and dynamic process which can be characterized by coupling of physical, chemical and biological processes and their feedback at different spatial and temporal scales. This paper presents a graph theoretic approach to characterize the behavior of nitrogen dynamics in terrestrial ecosystems. Different pools and observations are presented as nodes and their direct and indirect effects are displayed as edges connecting them. The directed network allows the percolation of perturbations among couplings in a desired direction. We used a Boolean Network Model to test the effect of elevated nitrogen deposition on ecosystem productivity by running the model under different initial conditions and analyzing alternate stable states (attractors).

Prior information about the processes involved in nitrogen cycle and its influence on plant growth is used to determine a set of rules that encodes causal relationships and change in one component leads to the change in another component of the network which is used as an input to a Boolean form of the process network.

We found that network is robust against simulated perturbations via introduction of drought and elevated nitrogen deposition alone, but showed great vulnerability under combined influence of drought and elevated nitrogen deposition. Simulation of ecosystem behavior from our model indicates the potential vulnerability of key nitrogen cycling process and provides basis for future experimental and field research to test the outcome of our model.

Restoration of sand dune vegetations after the Tsunami in Cuddalore, SouthEast coast of India

M. S. Muthukumarasamy and K.D. Kaliyaperumal
Faculty of Marine Science, Annamalai University, India

Sand dune plants or psammophytes include creepers like beach morning glory (Ipomea pescaprae) and sand spinifex (Spinifex littoreus). These vegetations serve as binding agents to form sand dunes which in turn act as a shelter for some marine animals during the breeding season. The sea turtles lay eggs in such sand dunes.  Moreover, the sand dunes also protect the coast from the waves by lessening the force of the oncoming waves.

These plants are threatened due to the construction of roads, formations of groynes and conversion of the coast into a tourist destination.  This occurs at Cuddalore, Silver Beach also.  A preliminary restoration work was under taken during the post-tsunami period and sand dune vegetation has been successfully restored in a few places on the Silver Beach of Cuddalore.  Propagation of I. pescaprae was done by plucking a portion of the creeper and planting it in pits dug at a depth of 30 to 40 cm. Three places were selected for restoration with 6m x 6m.  The planting of creepers were performed at an interval of 2m distance each in 6 pits.  The growth rate of the creepers was found to be 60 cm in length within two months.  The overall survival was 80%.  The plants were nurtured without any fertilizers except watering once in a week.  Fencing was made to protect the study area. Ideal season for the culture of Ipomea pescarprae in the sand dune area is the northeast monsoon period.

Key words: sand dune vegetation, Tsunami, coastal ecosystem

Comparison of wood quality of even-aged Teak (Tectona grandis L.f.) plantations in three districts of Sri Lanka

D.P. Weerasinghe and H.S. Amarasekara

Teak is listed as a super luxury timber in Sri Lanka and it has a high demand from construction and furniture industries. Teak hardwood is highly durable. It is an exotic species and, almost all teak plantations are located in dry and intermediate zones of the country. There are about 35,000 ha of teak plantations and most of these plantations are managed by the Forest Department. These plantations are distributed throughout many administrative districts in the country. Despite of its importance as a high-demand species in the market, there have been limited or no research studies conducted to assess the wood quality of teak grown in different districts.

This study compares the wood quality of even-aged teak plantations in three districts of Sri Lanka, i.e., Anuradhapura, Kurunegala and Ratnapura teak from Ratkarawwa area (Ratnapura district) was specially selected for comparisons, since there is a general belief among people that Ratkarawwa produce superior quality teak in comparison to other teak growing areas of the country.

Quality of teak wood was assessed by analyzing specific gravity and percentage of heartwood. Ring width was taken as the indicator of growth rate.

Three 45-year old trees of 45 grown in state plantations were examined in this study. Sample disks were extracted at breast height from each tree. Ring width and specific gravity of each ring was measured. The mean ring width values recorded for trees from Anuradhapura, Kurunegala and Ratnapura districts (A=2.679mm, K=2.652mm, R=3.106mm) did not differ significantly. The mean specific gravity values of trees from three districts (A=0.6142, K=0.6587, R=0.6901) were statistically significant. It was also observed that there is no significant relationship between ring width and specific gravity in the three districts. Heartwood percentage and wood colour were also analyzed to illustrate wood quality.

Slightly higher specific gravity value and high heartwood percentage were observed in Ratnapura teak. Furthermore, growth rate is high in this area and it contributes towards gaining high timber volume.

According to timber characteristics investigated in this study, it can be inferred that Ratkarawwa area (Ratanapura) produce high quality teak in comparison to the other two districts and, economically good teak wood are produced by plantations in Ratanapura district. However, other areas are also capable of producing good quality teak timber.

D.P. Weerasinghe and H.S. Amarasekara

Department of Forestry and Environmental Science, University of Sri Jayewardenepura, Sri Lanka.

Forest woodland ecosystem: An insight into the addition of litter through teak plantation

A. K. Mani, S. Manivasakan, S. Vijayabaskaran

Teak is an important tree species grown under plantation conditions for timber requirement. Being a deciduous tree, it favours for accelerated nutrient cycling. A field experiment was conducted in an eighteen year old teak plantation at Forest College and Research Institute, Mettupalayam, Tamil Nadu, India to study the litterfall, their composition and rate of decomposition. The litter collected were separated into leaf litter, flowers, fruits and twigs. All were subjected to decomposition by using nylon bag technique. The total annual litterfall accounted for 11,255 kg ha-1. Of the total litter, leaf fall in a year was 9216 kg ha-1 (81.9%) followed by 726 kg ha-1 (6.5 %) by twigs, 707 kg ha-1 (6.3 %) by fruits and 607 kg ha-1 (5.3 %) by the flowers. Among the litter components, flowers decomposed rapidly than the other components. The highest decomposition constant (K) was recorded for flowers (2.39) and the least for fruits (0.70). The per cent remaining of the absolute amount of dry matter of leaf litter, flowers, fruits and twigs after one year of decomposition was 17.3, 9.2, 49.5 and 19.6, respectively.

A. K. Mani, S. Manivasakan, S. Vijayabaskaran

Regional Research Station, Tamil Nadu Agricultural University, India

Growth, biomass and carbon accumulation among rubber (Hevea brasiliensis), teak (Tectona grandis) and mahogany (Swietenia macrophylla) A case study from 1 to 10 Years of Age Series

N. Appuhamy1, L. Samarappuli2 and S. Karunaratne1

The study was conducted to compare the biomass accumulation and carbon stocks among rubber, teak and mahogany. Above Ground Biomass of each species were calculated using the allometric models. Mean total tree height of rubber, teak and mahogany were ranging from 0.87 m to 20.32 m, 3.41 m to 11.05 m and 1.65 m to 7.53 m, respectively, between 1 to 10 years of age. For height and age, regression logistic standard curves were fitted to teak, rubber and mahogany with the R2 of 0.845, 0.916 and 0.921 respectively. The mean dbh of rubber, teak and mahogany were varying from 2.19 cm to 19.63 cm, 1.97 cm to 12.84 cm and 1.75 cm to 8.14 cm, respectively, within the selected age series. Exponential curves for rubber (R2=0.976) and teak (R2=0.915) and logistic curve for mahogany (R2=0.913) were fitted for dbh vs. age. Mean total tree biomass and carbon stock in rubber were significantly higher from other two species in all selected age series, except first year; biomass and carbon stock varying 0.89 kg/tree to 262.61 kg/tree and 0.45 kg/tree to 131.30 kg/tree, respectively. For other two species, it was ranged from 0.74 kg/tree to 88.87 kg/tree and 0.37 kg/tree to 44.35 kg/tree for teak and 0.49 kg/tree to 23.83 kg/ tree and 0.24 kg/tree to 11.91 kg/tree for mahogany. For Biomass and age regression logistic, critical exponential and exponential standard curves were fitted to rubber (R2=0.965), mahogany (R2=0.862) and teak (R2=0.874). The relationship of Height vs. dbh showed a high degree of association for rubber (R2=0.918), teak (R2=0.859) and mahogany (R2=0.976). Moreover, the relationship of biomass vs. height recorded a high degree of association for rubber (R2=0.911), teak (R2=0.862) and mahogany (R2=0.962).

N. Appuhamy1, L. Samarappuli2 and S. Karunaratne1

1Department of Plantation Management, Faculty of Agriculture and Plantation Management, University of Wayamba, Sri Lanka 2Department of Soils and Plant Nutrition, Rubber Research Institute of Sri Lanka.

Deterioration of soil quality with continuous plantation of teak (Tectona grandis)

N.T. Diyalawaththa1, R.M.D. Alawathugoda2 and P.I. Yapa1

A study was carried out at Rathmale teak Plantation, Thalawa to investigate the cause for the poor growth of teak saplings in a selected area. The study hypothesized that the poor growth and development of second rotation teak is a result of poor physical and chemical properties of the soil that gradually developed after the conversion of natural forest to plantation. Three sites, poorly grown teak plants, normally grown teak plants, natural forest land were selected. Soil samples from top and sub layer were analysed for pH, Electrical conductivity (EC), Nitrogen, Phosphorus, Potassium, CEC, Soil organic matter (SOM), Texture and Bulk density (BD). Bulk density, SOM and EC were significantly different between site one and site two. Higher BD, lower SOM and EC are key components of the soil quality and the changes may have led to the poor growth of Teak in site one. It was therefore clearly evident that the change in soil quality as a result of the conversion of natural forest to teak plantation is linked with the poor growth of teak saplings in the area under investigation.

N.T. Diyalawaththa1, R.M.D. Alawathugoda2 and P.I. Yapa1

1Department of Export Agriculture, Sabaragamuwa University of Sri Lanka 2Forest Research Center, Forest Department, Sri Lanka

Economic valuation of conservation of genetic resources of wild rice relatives : Assessing the preferences of adjacent community for conserving Oryza granulata in the Wavulpane area

R. Dissanayake1, S. Guruge1, M. Udugama1, M.U. Jayasinghe1, U.A.D.P. Gunewardena2
R.P.L.C. Randeni and R.S.S. Rathnayake3

This study was aimed to achieve the specific objective of assessing the preferences of adjacent communities for utilization, benefit sharing and conservation of the genetic resources of Wild Rice Relatives (WRR) in Sri Lanka and to explore the capability of setting the priorities for conservation and management of WRR based on these preferences. The “Wavulpane” village located in the Rathnapura district was selected as the case as: (a) it was reported to be one of the growing areas for the WRR of Oriza granulata, and (b) there were no weedy rice problems prevailing in this village. The “Choice Experiment Models” (CEM) [i.e. stated preference method used to obtain Option Values for non-market goods by exploring the individuals’ stated behavior in a hypothetical setting] were applied. The data were collected from 50 individuals who were well aware of the presence and potential importance of this particular WRR through a Participatory Community Appraisal (PCA) carried out with the support of a structured questionnaire designed specifically for the CEM. Outcome of the Choice Experiment, which used a Fractional Factorial Design to array four attributes and three levels in the choice sets orthogonally, shows that an individual in an adjacent community was Willing-To-Pay nearly Rs. 82 per year for in-situ conservation of WRR. The need of the hour is, therefore, to develop appropriate policy and institutional framework that works for this task to which both short and long term policies as well as stakeholder participation should be guaranteed (i.e. research stations, universities, NGOs).

R. Dissanayake1, S. Guruge1, M. Udugama1, M.U. Jayasinghe1, U.A.D.P. Gunewardena2
R.P.L.C. Randeni and R.S.S. Rathnayake3

1Department of Agribusiness Management, Wayamaba University of Sri Lanka
2Department of Forestry and Environment Science, University of Sri Jayawardenapura Sri Lanka
3Ministry of Environment and Natural Resources of Sri Lanka.

Timber production in high density planting of Hevea brasiliensis

T.U.K. Silva, V.H.L. Rodrigo, S.M.C.U.P. Subasinghe

The demand of natural rubber has increased continuously with the increase in population and living standards of the human being. Rubber plantations are also a major resource of timber and fuel wood. In order to meet the continuous increase in demand for latex, timber and fuel wood, 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. Also, the optimum density should vary with different socio-economic conditions. 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 Ratnapura district of Sri Lanka in 1992. Rubber was planted in three high densities, i.e., 600, 700 and 800 trees per hectare, with the presently recommended level of 500 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 plots whilst clones were in the sub plots. Five trees in each sub plot were selected randomly and were used for the measurements of total tree height (TH), crown height (CH), thickness of the untapped bark (BT) and tree diameter at breast height at 11 years after planting (11 YAP). Thereafter, stem volumes were determined using Newton’s formula.

Both TH and CH did not vary significantly among planting densities tested. Though 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 decline was compensated by increased number of trees in high densities resulting in comparable levels of merchantable volume per hectare among different densities. Total stem volume per tree remained same among four densities tested with that total stem volume per hectare increased significantly with the increase in planting density. Therefore, higher densities are more useful in the industries of fuel wood, pulp, MDF boards etc. Among the clones tested, the clone RRIC 121 outperformed in growth and timber production. The clone RRIC 110 was infected with Corynespora leaf 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.Key words: rubber, planting density, latex, timber, fuel wood

T.U.K. Silva1, V.H.L. Rodrigo1, S.M.C.U.P. Subasinghe2

1Rubber Research Institute of Sri Lanka

2Department of Forestry and Environmental Science, University of Sri Jayewardenepura, Sri Lanka.

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

K.R.A.H.A. Randeni and S.M.C.U.P. 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 and further divided into 240 plots of 20 perch each.

In order to identify the relationships, between growth and site factors, 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 used for the present study, using ArcView 3.3. In order to create digital maps, the survey plan of the selected forest was digitized and georeferenced using 10 ground control points collected by a GPS data receptor. Then the georeferenced 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.


K.R.A.H.A. Randeni and S.M.C.U.P. Subasinghe

Department of Forestry and Environmental Science, University of Sri Jayewardenepura Sri Lanka.