20.13.2.2 Carbon sequestration

Figure 20.14: Graph of NDVI and LST correlation Source: Primary This land surface temperature affects human life as during the daytime, Earth surface absorbs the heat of sun and increases its temperature out of which some warmth rises into the air where gases catch and hold the warmth near the surface and air temperature rise with increase in humidity. It affects human physically, psychologically and socially. It also effects the health condition such as depression, anxiety, dehydration, weakness, loss of salt, headaches, loss of interest in social interaction psychological un-peacefulness. This temperature also influences weather and climate patterns. For example, in places where it is too hot or too cold, the crops may die. Along with this it also affects glaciers, ice sheets, permafrost, etc. in Earth’s ecosystem. Increasing green spaces can reduce the surface temperature in turn reducing other climatic problems as well as health problems including glaciers, ice sheets, etc.

20.13.2.2 Carbon sequestration

Trees play an important role in reducing atmospheric CO2 through assimilation. They sequester carbon by capturing carbon dioxide from the atmosphere and transforming it into biomass through photosynthesis. Sequestered carbon is then accumulated in the form of biomass, deadwood, litter and in forest soils. Greens constitute a major carbon pool by absorbing 25% of carbon in atmosphere which includes trees as well as grass. For grass:  Total area of grass and lawns is considered.  Carbon sequestration per year for grass is 1.13 T/Ha/year.  Areas of grass and lawns multiplied by carbon sequestration per year for grass gives total carbon sequestration by grass. For trees:  The girth of the tree is measured at the girth at breast height (GBH) – 1.32 m above ground surface  Tree diameter is measured as D = GBH + 3.14 (assuming the tree trunk to be cylindrical)  Above ground biomass (AGB) is estimated by multiplying the bio - volume to the green wood density (WD) of tree species. Tree bio – volume (Tbv) value is calculated by: Tbv = 0.4 *D*D*H

AGB = WD * Tbv Standard average density of 0.6gm/cc is applied wherever the density value is not available for tree species.  Below ground biomass (BGB) is calculated by multiplying the above ground biomass (AGB) by a factor of 0.26 as the root to shoot ratio BGB = AGB * 0.26  Total biomass (TB) is the sum of the above and below ground biomasses. TB = AGB + BGB  Carbon estimation: Generally, for any plant species 50% of its biomass is considered as Carbon content in the tree C = TB / 2  As CO2 is composed of 1 molecule of carbon and 2 molecules of oxygen, the atomic weight of carbon is 12.001115 while that of CO2 is 43.999915. The ratio of CO2 to C is 3.6663. therefore, the weight of CO2 sequestered in the tree is determined by multiplying the weight of Carbon contained by a factor of 3.6663 CS = C * 3.663 But due to data constraints on the number and type of plant species present in Vijayawada city, various assumptions were taken to calculate the amount of carbon sequestered by the different types of trees in Vijayawada i.e.:  The NDVI classification was considered and the trees were classified under the categories of less, medium and high vegetation. Trees were considered for the category of high vegetation, shrubs, weeds and small plants for medium vegetation and grass for less vegetation and the calculation was further carried out.

Figure 20.15: Chart of NDVI categories with type of vegetation Source: Primary  Average individual tree coverage was considered by taking the average of the tree coverage of major species.  For each category of NDVI major species of trees, shrubs, weeds and grass of Vijayawada was considered and for those the above methodologies for calculation of carbon sequestration power were carried out.  Average sequestration power for each category was found out by taking the average carbon sequestration power of major species.