1,720,961 research outputs found
Assessment of Soil Carbon Stocks in Selected Freshwater Urban Wetlands in Colombo District, Sri Lanka
Full text linkWetlands have a high potential to sequester atmospheric carbon and can play an important role in climate change mitigation. Vegetation parameters and climatic conditions have a direct influence on the capacity of carbon stock in wetlands and the carbon sequestering process is linked to the productivity and decomposition rate. The current study assessed the carbon stock capacity of two wetlands in the Colombo district. These were the Green Isle urban wetland (part of the Bellanwila- Attidiya sanctuary), which is a wetland undergoing restoration and the Beddagana urban wetland, a successfully restored wetland of the Colombo Ramsar wetland complex. The current study had two main objectives: firstly, to assess and compare the soil carbon stock capacity in two urban wetland areas (one successfully restored, the other undergoing restoration). Secondly, to compare the carbon stock capacity of freshwater urban wetlands in the Colombo district with that of other tropical ecosystems. The study was conducted from December 2022 to February 2023. Soil samples were collected at depths of 0-20 cm and 20-40 cm from the soil surface and obtained from four plots in Green Isle and five in Beddagana. The loss of ignition method was used to calculate soil organic carbon (SOC) concentration. Soil organic matter (SOM), soil bulk density, and soil depth were determined for calculating carbon stock. The estimated average carbon stock up to a depth of 40 cm in the Green Isle urban wetland was 245±5 C/ha. Regarding Beddagana urban wetland, three ecosystem types were identified: shrubland, marshland, and woodland. The average carbon stock up to 40 cm depth in the three ecosystems was 315±5 t C/ha, 493±6 t C/ha, and 513±3 t C/ha respectively. The overall average carbon stock up to 40 cm depth in the Beddagana urban wetland was estimated at 441±4 t C/ha. The study revealed that the soil organic carbon stock capacity of the restored urban wetland surpasses that of the wetland currently undergoing restoration. Comparison with studies on other tropical terrestrial ecosystems showed that the urban wetlands under study held relatively higher carbon reservoirs. The vegetation cover and human disturbance on the soil influenced the diversity seen within the two sites and between them. The study highlights that within the Colombo district, restored freshwater urban wetlands in particular are important for climate change mitigation as they have a higher soil organic carbon stock capacity.
Keywords: Urban wetlands, Climate change, Mitigation, Carbon stock, Carbon sequestratio
Exploring the Spatial Variation of Morpho-Anatomical Traits of True Mangrove and Mangrove Associates in the Southern Province of Sri Lanka in Accordance with Climatic Adaptation
Full text linkAs salt-tolerant species, mangrove vegetation has evolved special characteristics to survive in its harsh environment. Since leaves are the most productive organs and are exposed to the external environment, they are highly sensitive to environmental changes. Although many studies on Sri Lankan mangrove flora have been focused on mangrove physiology, conservation etc., only a few studies have focused on leaf morpho-anatomical characteristics in relation to different climatic conditions. The present study is aimed to determine the spatial variation of morphological and anatomical characters of leaves of true mangrove and mangrove-associate species in the Southern Province of Sri Lanka. Seven mangrove sites in the Southern Province covering the three principal climatic zones were selected. Mature leaves were collected at each site along with soil salinity measurements. Leaf morphological traits such as specific leaf area (SLA) and leaf anatomical traits including leaf thickness with cuticle (LT), palisade thickness (PT), spongy mesophyll thickness (ST), palisade to spongy ratio (PSR) and water storage tissue thickness (WST) were measured. ANOVA test and Cluster Analysis were carried out using RStudio software to determine whether there is a significant morpho-anatomical trait variation in relation to different climatic zones. The study observed varied leaf trait values for different true mangrove and mangrove associate species that emphasized the varying degrees of ability to cope with different environmental conditions. For instance, a lower leaf area and SLA were observed in true mangrove species compared to mangrove associates. Lumnitzera racemosa Willd. had significantly higher LT (481.56 μm±53.74b) and WST (221.14 μm±47.9a) which facilitates osmoregulation. In addition, high PSR was observed in Acrostichum aureum (L). which would enhance the photosynthetic efficiency. Furthermore, a variation in laminar traits was observed in relation to different climatic zones. Some species including Bruguiera sexangula (Lour) Poir, Rhizophora spp., Hibiscus tiliaceus (L). and Clerodendrum inerme (L) Gaertn. showed significantly higher SLA in the wet zone. The presence of salt glands on the adaxial surfaces of the leaves of Acanthus ilicifolius (L)., a mangrove associate species, revealed similar adaptations as in true mangrove species. A spatial variation in clustering was observed with members of the same family clustering together, indicating a genetic influence. A. ilicifolius (L)., a mangrove associate species, exhibited similar adaptive responses as true mangroves whereas Excoecaria agallocha (L). showed adaptations to inhabit different climatic zones. In conclusion, both true and mangrove associate species are likely to adapt to environmental changes under climate change scenarios. This study would aid in the identification of climate- resilient species for mangrove restoration programs.
Keywords: Mangrove, Morpho-anatomical traits, Adaptation, Mangrove associates, Spatial variation, Climate chang
A Study on Soil Quality Parameters of Two Urban Wetlands in Colombo District, Sri Lanka
No full textThe biological productivity of urban wetlands and quality of their ecosystem services depends on the health of its soil characteristics. Soil characteristics influence vegetation growth, pollutant buffering potential and watershed protection through regulation and infiltration. Assessment of soil characteristics is therefore required for effective management of urban wetlands, particularly of those undergoing restoration. However, in Sri Lanka, limited studies have focused on soil health in urban wetlands. The study evaluated the soil characteristics of two wetlands in the Colombo district: the Green Isle urban wetland (part of the Bellanwila-Attidiya sanctuary), a site currently undergoing restoration, and the Beddagana urban wetland, a successfully restored site (part of the Colombo Ramsar wetland complex). The main objective was to compare the soil characteristics in two urban wetland sites that differed in restoration status. Soil samples were taken at depths of 0-40 cm from the surface, with five replicates collected from each of the four plots at Green Isle and five plots (25 m2 area each) at Beddagana wetland sites. Eleven soil parameters; temperature, moisture, pH value, electrical conductivity, bulk density, organic matter, nitrate, phosphorus, potassium, texture, and color were determined through field and laboratory investigations over a 3-month period (December 2022 – February 2023). Data analysis using two-way ANOVA (R version 4.2.3) revealed significant differences in soil temperature, pH, electrical conductivity, nitrate, and phosphorus content between the two urban wetland sites over the period. The principal component analysis identified electrical conductivity, soil temperature, and soil nutrients as key factors distinguishing the soil samples of the two sites, along with the difference in soil pH value. The Beddagana urban wetland had a loamy soil, and the Green Isle site had a higher clay content. On the Simple Additive Soil Quality Index (SQI), the Beddagana site exhibited higher soil quality (SQI=5.67) compared to the Green Isle site (SQI=4.96). The significantly higher value for conductivity and nitrate of the Green Isle site could be due to waste disposal from surrounding urban areas while the higher temperature would be a result of the lower vegetation cover in comparison to the Baddegana site. In conclusion, the SQI indicates that the restored Beddagana urban wetland has higher soil quality than the Green Isle urban wetland, which is still undergoing restoration. This validates its use in further studies to assess restoration status of urban tropical wetlands. The study shows the importance of assessing specific soil characteristics such as electrical conductivity when restoring degraded urban wetlands and the role of soil properties in understanding disturbances.
Keywords: Urban wetlands, Soil quality parameters, Restored wetlands, Soil nutrient
Assessing Soil Carbon Recovery: Evidence of Progressive Restoration at a Lowland Wet Zone Site in Sri Lanka
No full textDiyakothakanda forest in the Kalutara district (6° 45' N - 80° 31' E) is a 2-hectare restoration site that was initiated in 2009. The restoration project, which used the relay floristic method (2016 onwards), demarcated the degraded forest area into three zones (A, B, and C) from lower to higher elevations. The main objective of the present study was to compare soil characteristics and soil carbon stock with an adjacent reference forest to determine the success of initial restoration efforts in terms of soil. A stratified random sampling approach was used. From each zone of the restoration site (RS) and the corresponding zones of the adjacent natural forest (NF), five topsoil samples (0 to 25 cm depth) per zone were collected, and soil pH, electrical conductivity, moisture, bulk density, and organic carbon content were measured. Hierarchical clustering was performed based on soil parameters using RStudio (version: 4.4.1). A heat map was generated (ArcGIS Pro 3.0.1) using soil carbon stock data. No significant difference was observed in soil pH (5.4 -5.6) and electrical conductivity (45.7mS/m) between the two sites. A significant difference was observed between the natural forest and the restoration site in soil moisture (RS: 1.1%, NF: 9.1%) and organic carbon content (RS: 4.5%, NF: 6.1%). Soil carbon stocks were 10573 t ha-1 and 4334 t ha -1 in the natural forest and restoration site, respectively. This significant difference shows that the restoration effort would require further time for carbon stocks to recover to levels seen in natural forests. However, out of the three zones of the restoration site, zones A and B, which are the older plots, showed a higher value for soil carbon stock compared to zone C. Under hierarchical clustering, five main clusters were formed, with most of the RS plots in the first cluster, while the last cluster showed only NF plots. In the other clusters, plots from both sites were seen, suggesting that these RS plots share similarities with the NF plots regarding soil parameters. This can be considered a positive early outcome for the restoration effort as it shows that the mature areas of RS have reached the NF level in terms of selected soil parameters. The current study lays a foundation for gathering further insights into the restoration process at this site and thereby suggesting optimized restoration strategies for the lowland wet zone of Sri Lanka.
Keywords: Soil carbon stock, Restoration site, Hierarchical clustering, Soil characteristic
The Importance of Non-Timber Forest Products in Livelihood Maintenance of Rural Communities of Mulatiyana Forest Reserve, Sri Lanka
Full text linkForests provide many products and ecosystem services for the wellbeing of people. However, increase in human population has caused an enormous pressure on the way of utilising forest resources. Several studies have claimed the use of Non-timber forest products (NTFPs) as a forest conservation strategy involving local communities. The NTFPs contribute in several ways to improve the livelihoods of populations living adjacent to forests; providing food, water, medicines, energy, other material inputs and a source of income. This enhances the value of the forest and encourages community-based forest conservation. A study was carried out in the Mulatiyana Forest Reserve; a lowland rain forest in Southern Province, Sri Lanka to obtain an overview of the current utilisation of NTFPs. Seventy-two individuals who use the forest on a regular basis and are residents within 1 km boundary of the forest participated in the survey. The study found that, utilisation of forest resources is restricted to age classes above 30 years. Thus, the interaction between the forest and the younger generation is rare. There is only 16% female representationamong the users and therefore, promoting the use of NTFPs by females has the potential of supporting their families by improving their livelihood. A majority of the forest users (85%) have not attained the GCE O/Ls’ indicating their possible ineligibility to pursue a profession. More than half (58.4%) of the forest users are farmers. Forest products are extracted as input materials for farming activities and hence their livelihoods are strictly bound with the forest. Most of the forest extractions were carried out to fulfill their food and medicine requirements. Plants with timber value (Vitex altissima), medicine (Canarium zeylanicum, Dimocarpus longan, Coscinium fenestratum) or other importance (Gyrinops walla, Caryota urens, Caesalpinia bonduc) are illegally extracted from this forest. Controlled and well managed practices inside the forests under the inspection of relevant authorities are essential to achieve sustainable forest management. Forest officers and rangers are actively involved in protecting this reserve. Community around the forest also actively participate in such activities by informing the authorities of illegal actions. The NTFPs are an important resource for local inhabitants, which also encourages community-based forestconservation actions. Further attention should be given to this aspect in local forest policy implementation.Keywords: Non-timber forest products, Community forestry, Sustainable forest management, Rural communities, Sri Lank
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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