How did dry soil temperatures differ under trees and in grasslands?

Details

Interactions between land and atmosphere directly influence hydrometeorological processes and local climate. Because vegetation cover varies, these feedbacks can change over small areas and become more complex. The study aimed to determine how soil moisture and vegetation cover interact to influence soil temperatures in very water-limited environments.

Researchers continuously monitored soil water content and soil temperature every 30 minutes for two and a half hydrological years, using capacitance and temperature sensors located in open grasslands and below tree canopies. The study covered three areas in drylands with a Mediterranean climate.

The results highlighted the importance of soil moisture and vegetation cover in modifying soil temperatures. During daytime under low-soil-moisture conditions, daily maximum soil temperatures averaged 7.1 °C below air temperature under tree canopies, whereas in grasslands they averaged 4.2 °C above air temperature. As soil wetness decreased, soil temperature increased, but this effect was significantly weaker under tree canopies than in grasslands. Both high soil water content and shading were reflected in lower maximum soil temperatures and smaller daily temperature amplitudes. Statistical analysis emphasized the influence of soil temperature on soil water reduction regardless of vegetation cover.

If soil moisture deficits become more frequent due to climate change, variations in soil temperature could increase, affecting hydrometeorological processes and local climate.