Tipping Points in Bacterial Richness Amplify Extracellular Enzyme Activities in Northern Peatlands

Jassey, VEJ ORCID: 0000-0002-1450-2437, Lafont Rapnouil, T ORCID: 0000-0002-5411-3479, Le Geay, M ORCID: 0009-0007-6098-7942, Walcker, R ORCID: 0000-0002-5769-810X, Gandois, L ORCID: 0000-0002-9326-6830, Barret, M, Fanin, N ORCID: 0000-0003-4195-855X, Robroek, BJM ORCID: 0000-0002-6714-0652, Lauga, B ORCID: 0000-0001-5997-1176, Andrews, LO ORCID: 0000-0002-8494-4791, Greuza, AB, Bakker, MR ORCID: 0000-0002-3251-3586, Bertrand, G, Birkwald, T, Borges, PAV, Branfireun, B, Brearley, FQ ORCID: 0000-0001-5053-5693, Brousseau, C, Bu, ZJ ORCID: 0000-0001-9710-6343, Carrias, JF ORCID: 0000-0002-6201-1544 et al (2026) Tipping Points in Bacterial Richness Amplify Extracellular Enzyme Activities in Northern Peatlands. Global Change Biology, 32 (9). pp. 1-17. ISSN 1354-1013

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Abstract

Bacterial communities are vital to northern peatlands' carbon and nutrient cycling, one of the Earth's largest terrestrial carbon stores. However, their diversity and ecological roles at broad geographic scales remain partially understood, limiting our ability to predict their response to global change. Here, we combine a trans-Holarctic survey across 171 Sphagnum-dominated peatlands (SDPs) with a continental-scale reciprocal transplantation experiment to quantify how bacterial diversity shapes carbon and nutrient cycling across bioclimatic gradients. We show that bacterial diversity and composition differ markedly among peatland bioclimatic regions and are primarily structured by the universal abiotic drivers of northern ecosystems: minimum temperature, snow cover, and soil water content. Ecological models further revealed that deterministic processes accounted for approximately 80% of bacterial community assembly, highlighting the strong influence of environmental filtering. Biodiversity-Ecosystem Function analyses identified bacterial richness as a key driver of carbon and nutrient cycling. Using moving-window structural equation models, we identified a critical bacterial richness threshold, below which extracellular enzyme activities increased by ~60%. This transition coincided with stronger environmental filtering and shifts towards bacterial communities with a greater predicted potential for extracellular nutrient acquisition and heterotrophic metabolism. Together, these findings demonstrate that bacterial richness underpins peatland biogeochemical functioning and suggest that biodiversity loss may accelerate carbon turnover, weakening the capacity of northern peatlands to retain carbon. As climate change threatens this unique microbiome, safeguarding bacterial diversity will be critical for maintaining ecosystem resilience and the stability of this globally important carbon sink.

Item Type:	Article
Uncontrolled Keywords:	Soil Microbiology; Bacteria; Biodiversity; Wetlands; Sphagnopsida; Carbon Cycle; Carbon; Microbiota; 4101 Climate Change Impacts and Adaptation; 31 Biological Sciences; 3103 Ecology; 41 Environmental Sciences; 14 Life Below Water; Soil Microbiology; Bacteria; Biodiversity; Wetlands; Sphagnopsida; Carbon Cycle; Carbon; Microbiota; 05 Environmental Sciences; 06 Biological Sciences; Ecology; 31 Biological sciences; 37 Earth sciences; 41 Environmental sciences
Subjects:	G Geography. Anthropology. Recreation > GE Environmental Sciences Q Science > QH Natural history > QH301 Biology
Divisions:	Biological and Environmental Sciences (from Sep 19)
Publisher:	Wiley
Date of acceptance:	11 August 2026
Date of first compliant Open Access:	8 October 2026
Date Deposited:	08 Oct 2026 10:35
Last Modified:	08 Oct 2026 10:35
DOI or ID number:	10.1111/gcb.71099
URI:	https://researchonline.ljmu.ac.uk/id/eprint/29633

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