Kuuri-Riutta Olivia, Le Geay Marie, Jassey Vincent E J, Barel Janna M, Laine Anna M, Ylänne Henni, Tuittila Eeva-Stiina
School of Forest Sciences, University of Eastern Finland, 80101, Joensuu, Finland.
Centre de Recherche sur la Biodiversité et l'Environnement (CRBE), Université de Toulouse, CNRS, IRD, Toulouse INP, 31062, Toulouse, France.
New Phytol. 2025 Nov;248(3):1336-1350. doi: 10.1111/nph.70519. Epub 2025 Sep 2.
The impacts of drying on bryospheric photosynthesis are poorly understood. Utilising a 20-yr-long experiment, we quantified the effects of long-term water level drawdown (WLD) on links between bryospheric photosynthesis, microbial community composition, decomposition, and environmental variables. The community structure of photoautotrophic microbes was investigated using metabarcoding and quantitative polymerase chain reaction. Microbial photosynthesis was measured as photosynthesis efficiency (φPSII) and maximum electron transport rate through photosystem II (ETR). Bryospheric photosynthesis was measured using an infrared gas flux analyser. Chlorophyta, Cyanobacteria, and Ochrophyta were dominant photoautotrophic phyla in all study areas, but communities had site-specific WLD responses. WLD increased microbial and bryospheric photosynthesis in the poor fen. ETR was promoted by soil phosphorus concentration, φPSII, and Chlorophyta abundance, and bryospheric photosynthesis by Cyanobacteria abundance, a deep water table, soil sulphur concentration, and decomposition. In undrained areas, high abundance of Cyanobacteria promoted soil nitrogen concentration and, therefore, photosynthesis. In WLD areas, these connections were lost, but bryospheric photosynthesis benefited from WLD directly. Our study confirms that photoautotrophic microbes, especially Cyanobacteria and Chlorophyta, are important contributors to bryospheric photosynthesis in pristine boreal peatlands. Furthermore, increased bryospheric photosynthesis after drying may offset carbon loss from increased decomposition, but this depends on the site characteristics.
干燥对苔藓植物光合作用的影响尚不清楚。我们利用一项长达20年的实验，量化了长期水位下降（WLD）对苔藓植物光合作用、微生物群落组成、分解作用以及环境变量之间联系的影响。利用宏条形码和定量聚合酶链反应研究了光合自养微生物的群落结构。微生物光合作用通过光合作用效率（φPSII）和通过光系统II的最大电子传递速率（ETR）来衡量。苔藓植物光合作用使用红外气体通量分析仪进行测量。绿藻门、蓝细菌门和褐藻门是所有研究区域中占主导地位的光合自养门类，但群落对水位下降有特定地点的响应。在贫养沼泽中，水位下降增加了微生物和苔藓植物的光合作用。土壤磷浓度、φPSII和绿藻门丰度促进了ETR，而蓝细菌门丰度、深水位、土壤硫浓度和分解作用促进了苔藓植物光合作用。在未排水区域，高丰度的蓝细菌促进了土壤氮浓度，从而促进了光合作用。在水位下降区域，这些联系消失了，但苔藓植物光合作用直接受益于水位下降。我们的研究证实，光合自养微生物，尤其是蓝细菌和绿藻，是原始北方泥炭地苔藓植物光合作用的重要贡献者。此外，干燥后苔藓植物光合作用的增加可能抵消分解作用增加导致的碳损失，但这取决于地点特征。
