The influence of drought strength on soil respiration in a woody savanna ecosystem, southwest China

Abstract

Background and aims: Drought is expected to be more frequent and more intense with global warming. Our aim was to investigate how soil respiration would respond to different levels of precipitation exclusion (‘drought strength’). Methods: We conducted a two-year drought experiment in a woody savanna ecosystem in south west of China, which consisted of four treatments: a control treatment (CK); 30% precipitation exclusion (PE3), 50% precipitation exclusion (PE5) and 70% precipitation exclusion (PE7). Results: 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. Unlike most other exponential relationships between soil respiration and soil temperature, a parabolic function was observed in all treatments (P < 0.05), which was due to higher soil temperature (>28 °C) coinciding with insufficient soil water content (<11% Vol). Respiration rate is best represented by a model which combines soil moisture and temperature. Conclusion: Soil respiration rates were significantly decreased as drought enhanced. The response of soil respiration to drought in the dry season should not be ignored especially when evaluating the effect of drought on soil respiration in a whole year in savanna ecosystems. The 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.