Temperature sensitivity of soil microbial activity modeled by the square root equation as a unifying model to differentiate between direct temperature effects and microbial community adaptation

• Published in: Global change biology 2018-07, Vol.24 (7), p.2850-2861
• Main Author: Bååth, Erland
• Format: Article
• Language: English
• Subjects: Adaptation; Adaptation, Physiological; Biological activity; Climate Change; Communities; Desert environments; Deserts; Ecosystem; Forests; Growth; Habitats; In situ temperature; Mathematical models; Microbial activity; microbial growth; Microbiomes; Microbiota; Microorganisms; Models, Biological; Polar environments; Q10; Rainforests; respiration; Sensitivity; Soil; Soil Microbiology; Soil microorganisms; Soil temperature; Soils; T min; Temperature; Temperature effects; temperature sensitivity; Tropical climate; Tropical forests
• ISSN: 1354-1013; 1365-2486
• DOI: 10.1111/gcb.14285

Numerous models have been used to express the temperature sensitivity of microbial growth and activity in soil making it difficult to compare results from different habitats. Q10 still is one of the most common ways to express temperature relationships. However, Q10 is not constant with temperature and will differ depending on the temperature interval used for the calculation. The use of the square root (Ratkowsky) relationship between microbial activity (A) and temperature below optimum temperature, √A = a × (T−Tmin), is proposed as a simple and adequate model that allow for one descriptor, Tmin (a theoretical minimum temperature for growth and activity), to estimate correct Q10‐values over the entire in situ temperature interval. The square root model can adequately describe both microbial growth and respiration, allowing for an easy determination of Tmin. Q10 for any temperature interval can then be calculated by Q10 = [(T + 10 − Tmin)/(T−Tmin)]2, where T is the lowest temperature in the Q10 comparison. Tmin also describes the temperature adaptation of the microbial community. An envelope of Tmin covering most natural soil habitats varying between −15°C (cold habitats like Antarctica/Arctic) to 0°C (tropical habitats like rain forests and deserts) is suggested, with an 0.3°C increase in Tmin per 1°C increase in mean annual temperature. It is shown that the main difference between common temperature relationships used in global models is differences in the assumed temperature adaptation of the soil microbial community. The use of the square root equation will allow for one descriptor, Tmin, determining the temperature response of soil microorganisms, and at the same time allow for comparing temperature sensitivity of microbial activity between habitats, including future projections. The square root model is suggested as a unifying model of temperature effects that allows for describing the temperature sensitivity of soil microbial growth and respiration using only one descriptor, Tmin. Tmin will also indicate the adaptation to temperature of the microbial community. A global envelope of Tmin values from −15°C in cold, Arctic habitats, to around 0°C in tropical regions, is suggested, with an 0.3°C increase in Tmin per 1°C increase in mean annual temperature.