Kriging-based estimation of the change in soil carbon stock in the Karasu coastal black sea region of Turkey

Abstract

In this study the effects of deforestation and land-use changes in Karasu Forests located within the provincial borders of Sakarya on elemental carbon and carbon stock were analyzed. The specific goals of this study are 1) to predict and map soil carbon stocks as a function of depth from the ground surface up to 1 m depth for the Karasu region using a weighted ordinary kriging approach that takes into account the land use spatial distribution; 2) to evaluate the impact of the land use pattern in the study area (primarily forested and deforested areas) on soil carbon stock; 3) to reveal the relationship between the soil carbon stock and soil parameters in the study area. For this purpose, 360 soil samples were collected over the Spring and Fall 2009 seasons from a total of 45 different locations covering the entire study area (21 points within the forest areas, 24 points within defrosted areas). At each location, undisturbed soil samples were taken from depths of 0-5, 5-20, 20-45 and 45-100 cm. The carbon content of the soil samples were analyzed in the laboratory by dry combustion using an automatic CHNS analyzer. The spatial distribution of the soil carbon stocks from the surface to a depth of 1 m was estimated using profile depth distribution functions and a modified ordinary kriging procedure that honors the observed C stock data, their statistical spatial structure as well as the land use pattern at each location. As a result of geostatistical analysis, spatial average values of carbon stocks were 9.96 kg/m2 in spring 2009 and 10.84 kg/m2 in fall 2009. It was observed that the impact of deforestation on carbon content within the study area during the last two decades was limited to the upper most 0-5 cm layers. However, deforestation did not caused a significant change in the amount of total carbon sequestered in soil up to a depth of 1 m.|Keywords : Land Use Change, Soil Carbon Stock, Geographic Information System (GIS), Geostatistical Analysis.