Multi-Depth soil temperature trend assessment in Silifke, Türkiye: A case study from Mersin province

Abstract

Many factors such as solar radiation, surface air temperature, precipitation, and vegetation cover play an important role in influencing soil temperature. Thus, soil temperature and depth are parameters that mediate and respond to climate change and are related to global warming. Understanding soil temperature dynamics at different depths is essential for assessing the temporal and spatial impacts of climate change on terrestrial systems. Such multi-depth analyses provide insight into how different soil layers respond to warming, which is crucial for agriculture, hydrology, and ecosystem management. In this study, Mann–Kendall Trend Test and Şen’s Innovative Trend Test (using statistical parameters such as Sen's Slope, Z-value, p-value, Tau, and ITA's Slope) were applied to determine the temperature trends at different soil depths (5 cm, 10 cm, 20 cm, 50 cm, and 100 cm) between 1980 and 2022 in Silifke, Mersin, Türkiye. The analyses revealed that soil temperature trends ranged from −0.0119ÅãC to 0.0892ÅãC annually, indicating significant warming in surface layers. When analyzing the monthly changes in soil temperature as a function of depth, it was found that there were significantly increasing trends in all months except January (p < .01 or p < .05). Therefore, it can be said that soil temperatures are also increasing on an annual basis. However, the strongest trend of temperature increase was observed in the summer months (June–August), followed by a significant increase in the fall months (September–November). Furthermore, this increase was more pronounced at near-surface depths (5 cm, 10 cm, and 20 cm). Soil layers near the surface are more affected by global warming or seasonal changes. In contrast, deeper layers exhibit delayed responses to temperature fluctuations. These findings underscore the need for long-term studies to monitor soil–climate feedbacks driven by temperature rise and climate change.