Abstract
Abstract. Carbon sequestration has been proposed as a means of slowing the atmospheric and marine accumulation of greenhouse gases. This study used observed and simulated land use/cover changes to investigate and predict carbon sequestration rates in the city of Karaj. Karaj, a metropolis of Iran, has undergone rapid population expansion and associated changes in recent years, and these changes make it suitable for use as a case study for rapidly expanding urban areas. In particular, high quality agricultural space, green space and gardens have rapidly transformed into industrial, residential and urban service areas. Five classes of land use/cover (residential, agricultural, rangeland, forest and barren areas) were considered in the study; vegetation and soil samples were taken from 20 randomly selected locations. The level of carbon sequestration was determined for the vegetation samples by calculating the amount of organic carbon present using the dry plant weight method, and for soil samples by using the method of Walkley and Black. For each area class, average values of carbon sequestration in vegetation and soil samples were calculated to give a carbon sequestration index. A cellular automata approach was used to simulate changes in the classes. Finally, the carbon sequestration indices were combined with simulation results to calculate changes in carbon sequestration for each class. It is predicted that, in the 15 year period from 2014 to 2029, much agricultural land will be transformed into residential land, resulting in a severe reduction in the level of carbon sequestration. Results from this study indicate that expansion of forest areas in urban counties would be an effective means of increasing the levels of carbon sequestration. Finally, future opportunities to include carbon sequestration into the simulation of land use/cover changes are outlined.
Highlights
Carbon sequestration is defined as the process of removing carbon from the atmosphere and depositing it in a carbon reservoir (UNFCC, 2015)
Residential space will increase in area by approximately 10 %, agricultural land will reduce by 5 %, forests will increase slightly by approximately 0.3 %, barren areas will reduce by approximately 6 % and rangeland will remain almost constant, with only slight fluctuations in area
The results suggest that the city of Karaj will experience a reduction in its levels of carbon sequestration due to the impingement of residential areas, which do not contribute to carbon sequestration, into other land use classes
Summary
Carbon sequestration is defined as the process of removing carbon from the atmosphere and depositing it in a carbon reservoir (UNFCC, 2015). When carbon is removed from the atmosphere and stored in the soil as organic carbon, its contribution to global warming is reduced. Any carbon that is stored in plant tissue is either consumed by animals or, after the plant dies, it enters the soil as decomposed organic matter. Soil organic matter is a complex mixture of carbon-containing materials that include decomposed plant and animal tissues, microbes (protozoa, nematodes, fungi and bacteria) and carboncontaining minerals. Factors such as climate, natural vegetation, soil texture and drainage all influence the level and duration of soil carbon sequestration (Schlesinger, 1984)
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