Dataset for: Heat wave-induced microbial thermal trait adaptation and its reversal in the Subarctic

Climate change predictions suggest that arctic and subarctic ecosystems will be particularly affected by rising temperatures and extreme weather events, including severe heat waves. Temperature is one of the most important environmental factors controlling and regulating microbial decomposition in soils; therefore, it is critical to understand its impact on soil microorganisms and their feedback to climate warming. We conducted a warming experiment in a subarctic birch forest in North Sweden to test the effects of summer heat waves on the thermal trait distributions that define the temperature dependencies for microbial growth and respiration. We also determined the microbial temperature dependences 10 and 12 months after the heat wave simulation had ended to investigate the persistence of the thermal trait shifts. As a result of warming, the bacterial growth temperature dependence shifted to become warm-adapted, with a similar trend for fungal growth. For respiration, there was no shif..., In brief, soil and field characteristics: We measured gravimetric soil moisture (105°C for 24 h) and SOM content through loss on ignition (550°C for 12 h). Soil pH and electrical conductivity (EC) were determined in a 1:5 (w:v) soil:water extraction. Soil total carbon (TC) and total nitrogen (TN) were measured using Dumas dry combustion by a C/N 144 elemental analyzer (VarioMAX CN, Elementar, Germany). The normalized difference vegetation index (NDVI) as a proxy for plant productivity, the fraction of photosynthetically active radiation (fPAR), and the leaf area index (LAI; the projected area of leaves over the unit of measured ground area; m2 m-2) were determined with NDVI meter (SpectroSense2+, Skye, UK).
The temperature and moisture data were collected by using data loggers (TMS-4 29cm, TOMST®, Czech Republic) with 15 min resolution. The in situ soil (-8 cm), surface (0 cm), air (+15 cm) temperatures, and volumetric soil moisture (between 0 and -14 cm) were monitored.
Bacterial growt..., , # Dataset for Heat wave-induced microbial thermal trait adaptation and its reversal in the Subarctic

[https://doi.org/10.5061/dryad.b5mkkwhkf](https://doi.org/10.5061/dryad.b5mkkwhkf)

We conducted a field warming experiment to test the effects of summer heat waves on microbial temperature traits. The field warming experiment included 4 independent blocks, and each block included 2 control and warmed plots. The dataset includes the field and soil characteristics (August 2020), *in situ* temperature and moisture measurements (between June 2020 and August 2020), as well as bacterial growth, fungal growth, and respiration rates in C unit (μg C g-1 SOM h-1) measured at different time points (August 2020, June 2021, August 2021).

The warming treatments started in mid-June and ran until mid-August, covering the growing season of 2020. In mid-August 2020, the IR heaters were removed after two months of warming, and the plots were left without warming treatment under ambient conditions. Then,...