Extensive severe droughts are frequently reported across the globe. How will these droughts influence the ecosystem, regional, and the global carbon balance? Savannas are a major component of the world’s vegetation and mainly include woody savanna (mainly tree), tree savanna (mainly tree and shrub), shrub savanna (mainly shrub and grass) and grass savanna (mainly grass with little shrub). However, few studies have focused on the response of woody savanna soil respiration to experimental drought.
Researchers from Global Change Ecology Group of Xishuangbanna Tropical Botanical Garden (XTBG) conducted a study to investigate how soil respiration would respond to different levels of precipitation exclusion (‘drought strength’).
The researchers conducted a two-year drought experiment in Yuanjiang savanna ecosystem in Yunnan, SW China, using three precipitation reduction levels. They made four treatments: a control treatment (CK); 30% precipitation exclusion (PE3), 50% precipitation exclusion (PE5) and 70% precipitation exclusion (PE7).
They found that the cumulative soil respiration rates were significantly decreased in both rainy and dry seasons as drought became more intense. The sensitivity of soil respiration to soil moisture decreased as drought severity increased. There were bursts of CO2 emission when dry soils were rewetted by rainfall after the dry season.
They observed a parabolic function in all treatments, which was due to higher soil temperature coinciding with insufficient soil water content.
The researchers regarded that quadratic relationship between soil respiration and soil temperature may be important for modeling the response of soil respiration to climate change (drought) in savanna ecosystems.