Arctic and alpine tundra ecosystems are large reservoirs of organic carbon1,2. Climate warming may stimulate ecosystem respiration and release carbon into the atmosphere3,4. The magnitude and persistency of this stimulation and the environmental mechanisms that drive its variation remain uncertain5-7. This hampers the accuracy of global land carbon-climate feedback projections7,8. Here we synthesize 136 datasets from 56 open-top chamber in situ warming experiments located at 28 arctic and alpine tundra sites which have been running for less than 1 year up to 25 years. We show that a mean rise of 1.4 °C [confidence interval (CI) 0.9-2.0 °C] in air and 0.4 °C [CI 0.2-0.7 °C] in soil temperature results in an increase in growing season ecosystem respiration by 30% [CI 22-38%] (n = 136). Our findings indicate that the stimulation of ecosystem respiration was due to increases in both plant-related and microbial respiration (n = 9) and continued for at least 25 years (n = 136). The magnitude of the warming effects on respiration was driven by variation in warming-induced changes in local soil conditions, that is, changes in total nitrogen concentration and pH and by context-dependent spatial variation in these conditions, in particular total nitrogen concentration and the carbon:nitrogen ratio. Tundra sites with stronger nitrogen limitations and sites in which warming had stimulated plant and microbial nutrient turnover seemed particularly sensitive in their respiration response to warming. The results highlight the importance of local soil conditions and warming-induced changes therein for future climatic impacts on respiration.

• MeSH
• buněčné dýchání * MeSH
• časové faktory MeSH
• datové soubory jako téma MeSH
• dusík metabolismus   analýza   MeSH
• ekosystém * MeSH
• globální oteplování * MeSH
• koloběh uhlíku MeSH
• koncentrace vodíkových iontů MeSH
• půda chemie   MeSH
• půdní mikrobiologie MeSH
• roční období MeSH
• rostliny metabolismus   MeSH
• teplota MeSH
• tundra * MeSH
• uhlík metabolismus   analýza   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Geografické názvy
• Arktida MeSH
• Názvy látek
• dusík MeSH
• půda MeSH
• uhlík MeSH

Heavy metal (HM) accumulation in soil affects plants and soil fauna, yet the effect on microbial alpha-diversity remains unclear, mainly due to the absence of dedicated research synthesis (e.g. meta-analysis). Here, we report the first meta-analysis of the response of soil microbial alpha-diversity to the experimental addition of cadmium (Cd) and copper (Cu). We considered studies conducted between 2013 and 2022 using DNA metabarcoding of bacterial and fungal communities to overcome limitations of other cultivation- and electrophoresis-based techniques. Fungi were discarded due to the limited study number (i.e. 6 studies). Bacterial studies resulted in 66 independent experiments reported in 32 primary papers from four continents. We found a negative dose-dependent response for Cu but not for Cd for bacterial alpha-diversity in the environments, only for Cu additions exceeding 29.6 mg kg-1 (first loss of - 0.06% at 30 mg kg-1). The maximal loss of bacterial alpha-diversity registered was 13.89% at 3837 mg kg-1. Our results first highlight that bacterial communities behave differently to soil pollution depending on the metal. Secondly, our study suggests that even extreme doses of Cu do not cause a dramatic loss in alpha-diversity, highlighting how the behaviour of bacterial communities diverges from soil macro-organisms.

• Klíčová slova
• Alpha-diversity, Bacterial communities, Heavy metals, Meta-analysis, Rhizosphere, Sediment, Soil,
• MeSH
• Bacteria genetika   MeSH
• kadmium MeSH
• látky znečišťující půdu * analýza   MeSH
• měď analýza   MeSH
• půda MeSH
• půdní mikrobiologie MeSH
• těžké kovy * analýza   MeSH
• Publikační typ
• časopisecké články MeSH
• metaanalýza MeSH
• Názvy látek
• kadmium MeSH
• látky znečišťující půdu * MeSH
• měď MeSH
• půda MeSH
• těžké kovy * MeSH