Affectivity of Chemical Weed Control in Commercial Tea Plantations: A Case Study in Hapugastenne Estate, Maskeliya, Sri Lanka

AbstractThe usage of agro chemicals on food crops is getting restricted day by day with the sanctions set by the institutes devoted in food security, mainly due to the disclosure of their harmful residual effects on human health. Thus, several Commercial Tea Plantation companies have voluntarily suspended the use of many Herbicides on Tea under their charge, which are still permitted to use in Sri Lanka. Intense emergence of Herbicide tolerant weed species on treated areas was noted in the mean time, although this crucial factor had been remained un-noticed as a result of frequent manual weeding under taken by the Tea estates under various other accounts such as plucking, fertilizer application, mossing and ferning green manure etc. Therefore, an investigation was carried out to ascertain the affectivity of Herbicides recommended for Commercial Tea Plantations, over a period of 24 months in Hapugastenne Tea Garden, Maskeliya, since year 2012 at five different elevations, with five replicates set at each elevation. Results show that over 20 weed species out of 23 acutely problematic weeds which cause great damage to Tea crop, are entirely tolerant to Diurone, Paraquat and Glyphosate and cannot be controlled by using said Herbicides. It was further revealed that such weed species have the ability to turn a Tea Plantation into a totally unproductive and economically non-viable unit within a time period of one to two years depending on the herbicide tolerant weed species present. These weeds are capable of suppressing the growth of the Tea bushes by making them stunted in growth with poor bush frames, turn the foliage yellowish and induce defoliation, unless they were removed completely by manual uprooting

CHANGES IN VEGETATION AND SOIL CHARACTERISTICS OF REGENERATING FOREST AT RANDENIGALA

Victoria, Randenigala, Rantambe(VRR) sanctuary is the largest sanctuary in Sri Lanka. Certainareas in the Rantambe catchment was disturbed for the construction of Randenigala dam in 1987with no planned rehabilitation programme. This study was initiated to assess the changingpattern of vegetation and its influence on soil physical and chemical properties of disturbedforestland near Randenigala dam, relative to the surrc:unding undisturbed natural forest.The site was located 1 km North of the Randenigala Dam in a hilly slope in the intermediatezone and was surrounded by relatively undisturbed natural vegetation of dry mixed evergreenforest. In the sampling site (about 100 ha) the vegetation and soil has been removed down toparental material for dam construction. Three rectangular transacts measuring 5mxlOOmweremarked in each natural and regenerating forest sites .AlI plants were identified, height anddiameter at breast height (dbh) over >2cm of woody plants were measured. Soil pits were cut inboth disturbed and undisturbed forest sites and profiles were described. Soil samples wereremoved from each horizons for the analysis of soil physical and chemical properties. In thedegraded sites, soil pits were cut in the open area (6m), in the canopy edge (3m), and 0.5m fromthe tree base of dominant pioneer tree species to observe the soil improvement.Plant density of the undisturbed forest was three times higher than the disturbed forest andconsists of 17 trees, six shrubs, and four woody climber species. Five trees, six shrubs, onewoody climber, two grasses, and three creepy herbaceous species were found in the regeneratingforest. Common families present were Euphorbiaceae (38%), Sterculaceae (24%) and Rubaceae(12%) in the undisturbed forest and Hipocraraceae (40%), Leguminosae (26%) andApocynaceae (18%)in the disturbed forest.Five and two major soil horizons were identified in the undisturbed and disturbed forest sites,respectively. Soil N, P, K and organic matter contents and hydraulic conductivity were greaterand the bulk density was lower in the undisturbed site. The mean weight diameter (MWD) of thesoil aggregate was greater in the soil horizons of undisturbed site (1.6-2.7mm) compared to thedegraded site (1.1 mm). Similar trends were also observed for wet aggregate stability in theundisturbed (90% remaining) and disturbed (71% remaining) in forest soils. However, MWD(1.5mm) and wet aggregate stability (83% remaining) gradually improved towards the tree baseof pioneer tree species. (i.e. under Bouhinia racemosat in the regenerating disturbed forest site.Increase in soil organic matter content stabilizes the soil aggregates and makes soil moreresistant to erosion by wind and water under the canopy of pioneer species. The retention of soilunder these trees contributes to the development of the soil profile, improvement of soil fertilityand subsequently, the vegetation diversity of degraded sites.

Nitrogen - grasping the challenge. A manifesto for science-in-action through the International Nitrogen Management System. Summary report

Report published by Centre for Ecology & Hydrology, Edinburgh, UK on behalf of the International Nitrogen Management System (INMS). Freely available to download from the Official link

Carbon stock and tree diversity of dry-zone homegardens in Southern Sri Lanka

Traditional land-use systems such as tropical homegardens hold a large potential for climate change mitigation and adaptation due to their multi-functional role in providing income and ecosystem services while decreasing pressure on natural forests. Although, the importance and recognition of homegardens has been highlighted for their large potential in carbon sequestration, tree diversity and functioning there is still lack of quantitative data on homegardens and their contribution to climate change mitigation. In this study, tree diversity and above-ground biomass carbon of woody species was estimated on a local level around the village of Beralihela in the dry south-eastern part of Sri Lanka. A total of 45 homegardens were sampled on size, floristic composition of trees, girth at breast height (GBH) and height of trees. In total, 4278 trees were sampled and 82 different tree species were recorded. The Shannon Wiener index used to evaluate biodiversity ranged from 0.76–3.01 with a mean value of 2.05. Using allometric models, we find a mean above ground biomass carbon stock of 13 Mg C ha-1 with a large range among homegardens (1–56 Mg C ha-1, n=45) due to a variation of tree diversity, species and composition between individual homegardens. Per unit area basis, above ground carbon stock was higher in small homegardens (26 Mg C ha-1) than medium (9 Mg C ha-1) and large (7 Mg C ha-1) homegardens due to a higher tree density. The results of this study contribute to closing the knowledge gap of the less studied dry-zone homegarden agroforestry systems and their function in storing carbon and provide multi-functional benefits to its users. The results are also useful for the national process of whether homegardens should directly or indirectly be considered to be included as an activity within Sri Lanka’s newly commenced UN-REDD National Programme. This study shows the potential of using tropical homegardens for future land-use planning and multiple benefits including carbon sequestration potential, particularly in terms of land scarcity and climate mitigation options. The concept of homegardens in Sri Lanka also provides interesting aspects to the debate and future research in terms of forest definitions and general sustainability

Aboveground tree carbon stocks of Lowland evergreen mixed vegetation at Gannoruwa

Conservation of global forests is being considered as one of the sustainable ways of mitigating global warming, because forests are widely perceived to act as major sinks for atmospheric carbon. Estimation of carbon stocks of tropical forests are important for management, planning and for REDD initiatives.Therefore, this study was initiated to estimate existing carbon stocks of a Lowland evergreen mixed forest at Gannoruwa and how it has changed overtime.The sampling points were selected using an unsupervised classified Landsat TM satellite image and topograhpic maps, considering the elevation level and the vegetation type. A GPS (Global Position System) was used to detect the correct location of sampling points and sampling plot size was set as 30m×30m. The dbh and height of each individual in the sampling plot which is greater than 5cm dbh was measured.The dbh and height values were applied to a pre-derived regression equation and the above ground biomass was calculated. The equation was Y=exp {-3.3012+0.9439 ln(D2H)},(r2=0.9) where, Y is aboveground biomass, D is dbh and H is height. Assuming the carbon stock as 50% of the biomass, the above ground carbon stock was calculated. It was 146.4 mt/ha of carbon and the total aboveground tree carbon stock was 39.1×103 tons. The estimated basal area of the forest has declined compared to 25year old recorded data and it reflects the carbon reduction of the forest due to anthropogenic activities

Carbon stock and tree diversity of dry-zone homegardens in Southern Sri Lanka

Traditional land-use systems such as tropical homegardens hold a large potential for climate change mitigation and adaptation due to their multi-functional role in providing income and ecosystem services while decreasing pressure on natural forests. Although, the importance and recognition of homegardens has been highlighted for their large potential in carbon sequestration, tree diversity and functioning there is still lack of quantitative data on homegardens and their contribution to climate change mitigation.In this study, tree diversity and above-ground biomass carbon of woody species was estimated on a local level around the village of Beralihela in the dry south-eastern part of Sri Lanka. A total of 45 homegardens were sampled on size, floristic composition of trees, girth at breast height (GBH) and height of trees. In total, 4278 trees were sampled and 82 different tree species were recorded. The Shannon Wiener index used to evaluate biodiversity ranged from 0.76–3.01 with a mean value of 2.05. Using allometric models, we find a mean above ground biomass carbon stock of 13 Mg C ha-1 with a large range among homegardens (1–56 Mg C ha-1, n=45) due to a variation of tree diversity, species and composition between individual homegardens. Per unit area basis, above ground carbon stock was higher in small homegardens (26 Mg C ha-1) than medium (9 Mg C ha-1) and large (7 Mg C ha-1) homegardens due to a higher tree density. The results of this study contribute to closing the knowledge gap of the less studied dry-zone homegarden agroforestry systems and their function in storing carbon and provide multi-functional benefits to its users. The results are also useful for the national process of whether homegardens should directly or indirectly be considered to be included as an activity within Sri Lanka’s newly commenced UN-REDD National Programme.This study shows the potential of using tropical homegardens for future land-use planning and multiple benefits including carbon sequestration potential, particularly in terms of land scarcity and climate mitigation options. The concept of homegardens in Sri Lanka also provides interesting aspects to the debate and future research in terms of forest definitions and general sustainability

Aboveground tree carbon stocks of Lowland evergreen mixed vegetation at Gannoruwa

Conservation of global forests is being considered as one of the sustainable ways of mitigating global warming, because forests are widely perceived to act as major sinks for atmospheric carbon. Estimation of carbon stocks of tropical forests are important for management, planning and for REDD initiatives.Therefore, this study was initiated to estimate existing carbon stocks of a Lowland evergreen mixed forest at Gannoruwa and how it has changed overtime.The sampling points were selected using an unsupervised classified Landsat TM satellite image and topograhpic maps, considering the elevation level and the vegetation type. A GPS (Global Position System) was used to detect the correct location of sampling points and sampling plot size was set as 30m×30m. The dbh and height of each individual in the sampling plot which is greater than 5cm dbh was measured.The dbh and height values were applied to a pre-derived regression equation and the above ground biomass was calculated. The equation was Y=exp {-3.3012+0.9439 ln(D2H)},(r2=0.9) where, Y is aboveground biomass, D is dbh and H is height. Assuming the carbon stock as 50% of the biomass, the above ground carbon stock was calculated. It was 146.4 mt/ha of carbon and the total aboveground tree carbon stock was 39.1×103 tons. The estimated basal area of the forest has declined compared to 25 year old recorded data and it reflects the carbon reduction of the forest due to anthropogenic activities.

Carbon stock and tree diversity of dry-zone homegardens in southern Sri Lanka

Tropical homegardens hold a large potential for climate change mitigation and adaptation due to their multi-functional role in providing income and ecosystem services while decreasing pressure on natural forests. However, there is still lack of quantitative data on homegardens and their landscape potential for carbon sequestration services. In this study, tree diversity and above-ground biomass carbon of woody species was estimated on dry-zone homegardens in the dry south-eastern part of Sri Lanka. A total of 45 homegardens were sampled on size, floristic composition of trees, diameter at breast height (GBH) and height of trees. In total, 4278 trees were sampled and 82 different tree species were recorded. The Shannon Wiener index used to evaluate biodiversity ranged from 0.76–3.01 with a mean value of 2.05. Using allometric models, we find a mean above-ground biomass stock of 13 Mg carbon (C) ha-1 with a large range among homegardens (1–56 Mg C ha-1, n=45) due to a variation of tree diversity, species and composition between individual homegardens. Per unit area basis, mean above ground carbon stock was higher in small homegardens (1 ha, 8 Mg C ha-1, n=7) homegardens due to a higher tree density. The results show a vast heterogeneity in terms of carbon and biological diversity within the dry zone homegardens; results that will contribute to closing the knowledge gap of the less studied dry-zone homegarden systems and their functions in storing carbon and providing multi-functional benefits to its users. The results are also useful for whether homegardens should directly or indirectly be considered to be included as an activity within Sri Lanka’s newly commenced UN-REDD National Programme

REDD+ readiness implications for Sri Lanka in terms of reducing deforestation

Any system to compensate countries for reduced emissions from deforestation and forest degradation (REDD+) requires a historical reference level against which future performance can be measured. Here we examine the possibilities Sri Lanka, a small forest country with limited data on forest carbon stocks, has to get ready for REDD+. We construct a historical reference level using available forest inventory data combined with updated 2008 and 2009 in situ carbon density data for Sri Lankan forests. Furthermore, we use a combination of qualitative and quantitative data to attribute the clearing of Sri Lankan forests in the latest years for which national forest inventory data are available, 1992–1996, to various proximate drivers and to estimate the opportunity cost of forest conservation. We estimate that baseline deforestation emissions in Sri Lanka amounted to 17 MtCO2 yr−1 in the 1992–1996 period, but conclude that it is challenging for Sri Lanka to produce a robust and accurate reference level due to the lack of nationally based inventories. We find that the majority of forest clearing (87%) is due to small-scale, rainfed farming, with the two other major drivers being rice and tea cultivation. Further, Sri Lankan revenues from REDD+ participation could be substantial, but they are sensitive to REDD+ policy transaction cost, highly uncertain timber revenues, and particularly the carbon price paid for emission reductions. The latter needs to be higher than $5–10/tCO2 if there are to be substantial incentives for Sri Lanka to participate in REDD+. There is, however, a large gap in the knowledge of deforestation drivers that needs to be filled if Sri Lanka is to formulate an effective policy response to forest degradation in REDD+. For successful REDD+ implementation in Sri Lanka to happen, technological assistance, readiness assistance, and continued political momentum are crucial