Influence of Global Warming on Aggregate Stability and Hydraulic Conductivity Under Highland Soil Order in Turkey

Ongoing global warming may cause an increase in air and soil temperatures. These increases can then lead to increase in the frequency of soil freezing and thawing cycle during the winter in cool-temperate and other high-latitude regions. The purpose of this study was to explore the effects of repeated soil freezing and thawing treated cycles (FTTC) on wet aggregate stability (WAS) and hydraulic conductivity (HC) in incubation laboratory and field experiment on Pellustert, Argiustoll, Haplustept, and Fluvaquent soils, the major soil groups in the eastern part of Turkey. To provide long-term climatic effect of soil FTTC on WAS and HC, a laboratory study was conducted simulating with three steps based on 60-year temperature cycles occurring in the region. The results demonstrated that the initial WAS increased with increases in FTTC from 3 to 6, by 18% to 113% but decreased after that point in all the soil freeze-thaw treatments by 2% to 25%, depending on soil type. The effect was more pronounced with increased moisture contents at freezing. The percent decrease in HC of soils ranged from 19% to 44%. The highest WAS values of soil samples under laboratory condition were determined in the Argiustoll soil, followed by Pellustert > Haplustept > Fluvaquent but was Fluvaquent > Haplustept > Pellustert > Argiustoll for HC of the soils. The field study results showed that global climate changes occurring in recent decades in the region deeply affected the WAS and HC values and that the highland soils are most sensitive to the global climatic change. Increasing air temperature has resulted in the rise of soil temperature, increasing the frequency of soil freeze-thaw cycles during the winter in cool-temperature and other high-latitude regions. If ongoing global warming continues this trend, WAS and HC changes in highland soils may lead to decrease and alterations in regional agricultural production such that regular organic manure or green manure amendments will be needed to sustain soil management and crop production for these major soil groups.