PG Thesis
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Item Comparative assessment of the spatial distribution and edaphic attributes of mangroves in Perumba and Puthuvype regions(Department of Forest Resource Management, College of Forestry, Vellanikkara, 2024-01-25) Rohan, M S.Mangroves are characterized by salt-tolerant vegetation thriving in tropical and subtropical coastlines. It provides critical ecological services and a source of livelihood for coastal communities. Globally, these crucial ecosystems are currently under threat due to the over-exploitation of natural resources. The mangroves in the state of Kerala have witnessed a drastic reduction in the area from seven hundred sq. km to a mere nine sq. km over the last five decades. Developmental activities and anthropogenic disturbances in the coastal areas are the major threats to these sensitive ecosystems. The knowledge of the extent of disturbance, the changes brought by the anthropogenic activities and their effect on the mangrove vegetation are the prerequisites for the sustainable management of these ecosystems. In this context, the present research work studied the extent of change in mangrove areas, variation in vegetation structures, soil and water properties among two contrasting regions namely, the Perumba river region with low and the Puthuvype region with high human disturbances. The Land Use Land Cover (LULC) classification for the current year has shown almost same percentage of mangroves to the total area in both the studied regions. In the present study, we used the three most widely used machine learning algorithms for the classification process. Among the machine learning algorithms studied, the Gradient Tree Boost (GTB) algorithm with a combination of Sentinel 1, 2 datasets and few spectral indices shown exemplary performance (88 % accuracy) in classifying mangrove areas. Change detection analysis showed a positive trend in mangrove cover in Perumba region (7.03 % increase) and contrarily a negative trend (66.51 % decrease) in the Puthuvype region during the study period (2013 - 2023). Phytosociological analysis figured out seven species belonging to four families in both Perumba and Puthuvype regions. The only difference in the species composition between the two regions is that Kandelia candel was found only in Perumba region, while it was replaced by Bruguiera gymnorhiza in the Puthuvype region. The common species present among these two regions were Avicennia officinalis, Bruguiera cylindrical, Excocaria agallocha, Rhizophora apiculate and Rhizophora mucronata. The Perumba region exhibits higher vegetation diversity indices when compared to the Puthuvype region. Perumba region exhibited higher seedling, tree, and sapling density, indicating a healthier mangrove ecosystem. In both regions, the majority of trees belong to the girth xii class of 20-30 cm. Further, Important Value Index (IVI) identified Avicennia officinalis as a dominant species followed by Rhizhophora mucronata in both the regions. Soil analysis showed a significant variation for chemical properties between the regions studied. Electrical conductivity, soil organic carbon, available nitrogen, available potassium, sodium, magnesium, lead, and chromium levels were recorded higher values in the Perumba region. Meanwhile, available phosphorus content was found higher in the Puthuvype region. In addition, biological properties viz, actinomycetes, bacteria, and fungi populations were higher in the Perumba region. Moreover, water analyses also revealed a maximum electrical conductivity, salinity and turbidity in the Perumba region. Altogether, the study showed a declining mangrove population in the Puthuvype region due to significant changes in the mangrove ecosystem brought by the intense anthropogenic interventions in the mangrove ecosystem, necessitating immediate action for the restoration of this fragile ecosystem.