Category Archives: Silviculture

Evaluation of Social Forestry Component of the Sri Lanka Australia Natural Resource Management Project

Posted on by

This reports the evaluation of the social forestry component of the  Sri Lanka Australia Natural Resource Management Project (SLANRMP) in the Kurunegala District. The main objective of this component was to contribute to poverty reduction through improved natural resource management in the dry and intermediate zone of Sri Lanka through community participation. 

The study focused on three forest ranges in Kurunegala District namely Mahawa, Galgamuwa and Malsiripura. Ihalathimbiriyawa village was selected from Mahawa Range while Dalapotugama and Katiyawa villages were selected from Galgamuwa and Malsiripura Ranges respectively. 30% of the households participating in the Project were selected from each forest range at random while those who are not participating were taken as control. Secondary data were collected from published reports while primary data were collected using questionnaire surveys, focal groups discussions and key informant surveys and field observations.

The project was able to reach more than 90% of the households in both Dalapotugama and Ihalathimbiriya villages while it was only 60% in Katiyawa village. In each village Community Based Organisation was functioning well and was registered with the Divisional Secretary. The participation of female members as Office Bearers was very high in all the villages (59-70%). The level of participation of the communities in project related work was highest in Ihalathimbiriyawa (95%) compared with others Dalapotugama and Katiyawa which was 60%. The extent of forest replanted/protected  and maintained was high in Dalapothagama and Ihalathimbiriyawa (107-192 ha) but this was much smaller in Katiyawa (42 ha). In all the three villages the occurrence of forest fires decreased  to none in the year 2007. With regard to availability  of water, more rainwater harvesting was significant after the Project. Although the total no of non agricultural activities did not change much, there was a market shift towards skilled labour after the project.

The main reason for participating in the project was for financial benefits  as well as protection of the village environment (26%). More group and individual savings with the project (95.6%). More credit sources introduced  which placed less reliance on the mudalali. More credits were taken for farming activities (43%) with the project as from only 4% without the project. Credit limits also increased from 10.5% to 52.3 % for the range Rs. 5000-20,000 which showed that the people’s livelihoods had enhanced significantly. The common mode of transport shifted from the push bike to motor cycle.
(40% to 64%).
The number of micro enterprises generated from the Project, especially the ones which are successfully continuing are rather few in all three villages (4-6% of the total households enrolled). However, loans had been applied for other enterprises and had been approved too. Apart from the Forest Department about 8 other agencies have established contacts with the communities with project related work. However, a major drawback experienced was  lack of forward market contracts which might be a deterrent to the sustainability of the Project.
H.D.P Sumanapala1  D.M.S.H.K Ranasinghe2 and Manoj Kumar Nathy31Forest Department, 2University of Sri Jayawardenapura, 3Sri Lanaka Australia Natural Resource Management Project

Problems and improvement potentials of Kandyan homegardens at Yatinuwara area

Posted on by

Kandyan homegardens are the most predominant upland cropping system which supposed to be highly adapted, diversified, economically and environmental viable land use system. Objectives of this study were to identify problems and improvement potentials to this important system of land management. Data were collected from randomly selected (n=65) homegardens in Yatinuwara District Secretariat division during 2006. A vegetation survey was conducted to evaluate the structure and composition of homegardens. A household survey was conducted by interviewing the members to identify tree use practices by family members, constraints and improvement potentials. Secondary data were also collected from Agrarian Service Centres, maps and reports.

Homegardens in the study area have maintained diverse on farm trees. They cultivating and using at least 138 species of which 36, 34, 24 and 6% comprised timber, medicinal plant, fruit tree and export agricultural crop species. There are 73, 193, 300 and 147, individuals of timber, fruit, medicinal and export agricultural crops plants/ha indicating high plant density per unit area. These species grown on homegardens have substantially contributed to meet the daily need of household, supplying mainly fruit, green vegetable, timber and fuelwood. Some of these species have medicinal value and also play an important role in soil conservation. This suggests that homegardens are important as a source of conserving agro-biodiversity, species, habitat and landscape protection. However, more than half of the homegardens of Yatinuwara area are 20-80 perches category which indicate land fragmentation. Thus, each land unit has to play a vital role with limited land availability. Therefore, sustainable management practices are very important to increase production to reach increasing demand due to increasing human population while maintaining the resource base. In satisfying necessary changes to homegardens, availability of quality planting material (only 22% had access to recommended planting material), height of fruit trees, poor soil management and labour scarcity were identified as major problems in Yatinuwara area. There are improvement potentials to homegardens by increasing the productivity of the existing system. It is possible even to increase the number of trees per homegardens by introducing new varieties. It is also possible to replace existing less productive individuals by certified planting material. In addition, management of soil can also be improved by introducing new techniques such as compost preparations with garbages and fallen leaves which require attitudinal changes of households. Implications of these are discussed with respect to food, nutritional and health security and income generation.

K I A Kothalawala, D K N G Pushpakumara and T Sivananthwerl

Department of Crop Science, Faculty of Agriculture, University of Peradeniya, Sri Lanka

Estimation of above ground biomass of forest trees using dbh as a single parameter

Posted on by

I  D Welivita and S M C U P Subasinghe
Department of Forestry and Environmental Science,
University of Sri Jayewardenepura, Sri Lanka

Forests in Sri Lanka contribute to the mitigation of climate change through sequestrating a net amount of carbon dioxide and also maintaining carbon stock as biomass. Total tree biomass comprised of above ground and below ground biomass of trees. This paper presents a methodology developed to estimate individual tree above ground biomass using allometric relationships. The advantage of this method is that the above ground biomass per unit area can be determined by estimating these values for different species separately within that area. The present study was conducted in Yagirala Natural Forest Reserve situated in Kalutara District, low country wet zone of Sri Lanka. In this study, the above ground biomass of different species available in that forest were predicted using the diameter at breast height (dbh).

45 tree species were identified in the forest and models were separately developed for each species. For each species, 3 classes were established using the size, i.e., small, medium, and large. For class 1 and 2 trees, the main stem and the average size branch were divided into sections and for each section end diameters and length were measured. The volume of each section was estimated using Smalian’s formula. The total branch volume was estimated by multiplying the average branch volume by number of branches. Then a volume and biomass relationship was estimated for each species by measuring the biomass of a known volume.

The leaf biomass in the crown was estimated by measuring that in 1m3 of crown volume. Then it was converted to the entire crown via crown volume. Finally above ground tree biomass was calculated by adding branch and crown biomass to stem biomass.

Then allometric relationships were developed to predict the above ground biomass of each of 45 species separately using dbh. A strong relationship was found between total tree biomass and dbh of all species with R2 values over 95%. In order to test further improvement of the models, total height was added as the second explanatory variable. However, it did not improve the R2 and for most species height became non-significant. Therefore the finally selected basic model structure was log biomass = a + b log dbh. The model parameters however, indicated different values for a and b for the different species, varying a from -1.71 (Mastixia tetranda) to – 0.73 (Xylopia parvifolia) and b from 2.01 (Putranjiva zeylanica) to 3.29 (Syzygium cordifolium).

Selection and Field Establishment of Tree Crops for Large Scale Plantations in Wet, Dry and Intermediate Zones of Sri Lanka

Posted on by

Rachitha Silva

Large-scale forest tree planting in Sri Lanka started in late 1950’s and till December 1998 has covered about 140,000 ha of forest plantations belonging to the Forest Department. The main plantation species are Teak, Eucalypts (Eucalyptus grandis), and Mahogany etc. Most of the fuel wood, miscellaneous hardwood and teak plantations are located in the Dry zone. Eucalypts and Pine plantations are mostly in the up country Wet zone. Mahogany plantations are situated in Intermediate and Wet zone. Current emphasis is on indigenous hardwoods, like Nedun while planting of Pines is banned and Eucalypts is being planted only on a very limited scale.

The selection of a tree crop depends on; the purpose of intended plantation, the potential species available for planting, the site qualities, Silvicultural and economic factors. The purpose of plantation is a policy decision of Government arising from a domestic need. After determining the purpose, the choice of species is narrowed. If a native species meets the need, there is no reason to choose an exotic, if not exotics have to be introduced. Species and provenance trials have to be carried out before establishment of plantation. The site qualities play a major role in Genotype x Environment interactions. The site qualities like climate, soil, physiographic and biotic factors affect the growth at different sites. Silvicultural factors include silvicultural systems, ecological requirements of species etc. Economical factors include demand and supply, Relative costs and returns.

Field establishment of a selected species involve several steps like surveying, site preparation, planting, maintenance and tending operation. Field establishment techniques of several plant species for Dry and Intermediate zone (Teak, Mahogany), Up country (Eucalyptus microcorys) and Low country Wet zone (Nedun) have been discussed.

Planting of Trees in Saline Soils

Posted on by

H.M.A.B. Herath

Soil salinity is the oldest soil pollution problem. The collapse the Babylonian empire is considered to be partly the result, of failure of irrigated crops due to the accumulation of salt. The problem is primarily associated with arid and semi-arid regions of the world, where there is an insufficient rain to leach out the soluble salts.

Three billion hectares of land have been affected by soil salinity in the world. In Europe twenty million hectares of land is affected due to this purpose in Sri Lanka, such salt affected soil is found along the coastal zone an extent of 223,000 hectares have been affected. This is about 3 percent of the total land area of the Island. Several natural and artificial factors influence the development of soil salinity. It provides unfavourable conditions for plant growth. Saline soils can be categorized as saline soil and saline alkali soil (sodic soil). Sodic soils are more detrimental for plant growth than saline soils. Good soil processing is critical for plant growth in saline soils. Therefore soil reclamation methods should be applied for eradicating soil salinity. Salinity of soil can be reduced by applying chemical, physical and biological methods. Another important factor is the choice of suitable plant species. The selected species should be adapted to saline conditions. The most suitable salt tolerant species include Eucalypts and Acacia species.

After establishment of plants, proper silvicultural practices and good maintenance are essential for development of a good plantation.