Change in Temperature Over the Past 50 Years at Wudaogou and Its Influence on Soil Temperature at Different Depths

Abstract

【Objective】 Soil temperature affects crop growth and biogeochemical processes in terrestrial systems, and understanding its variation is hence important to evaluate the impact of global warming on agricultural production and soil gas emissions. The aim of this paper is to analyze the change in soil temperature over the past 50 years at Wudaogou Hydrological Station in Anhui province, China. 【Method】 The analysis was based on data measured from 1971 to 2020. Monthly average temperature at different soil depths from 0 to 320 cm, as well as their relationship with ambient air temperature was analyzed, using linear trend estimation, M-K test and Morlet wavelet method. 【Result】 ①The temperature at different soil layers has changed. Except in the period from June to September, soil temperature in other months has been in increase, with the largest increase seen in March and the least increase in October. Temperature in the depths of 0~160 cm has been increasing, with the increasing rate decreasing along the soil depth. In contrast, the temperature at the depth of 320cm has been dropping. ②The wavelet analysis showed two dominant periods in the monthly-average temperature: 3~6, 8~12 a, and a further period of 15~25 a. ③The M-K mutation test showed that the temperature at depths from 0 to 320 cm had undergone abrupt changes in 2012, 2017, 2016, 2019 and 1972. ④The temperature at different soil depths was correlated with ambient air temperature differently, with the temperature in the depths of 0~80 cm being more sensitive to air temperature. No correlation was found between the air temperature and soil temperature at the depth of 320 cm. 【Conclusion】 The monthly average temperature at different soil layers has been in increase over the past centuries, likely due to global warming, though the increasing rate and its correlation with air temperature varied with soil depth.

Keywords

• soil temperature
• ambient air temperature
• monthly average
• morlet wavelet analysis