What question did this study set out to answer?

To determine if the Mediterranean alder Alnus cordata can perform nitrogen cycling similarly to the temperate species Alnus glutinosa under drought conditions.

April 16, 2026Open Access

Adaptive vegetation change as a pathway to sustain wetland nitrogen cycling

Key Points

To determine if the Mediterranean alder Alnus cordata can perform nitrogen cycling similarly to the temperate species Alnus glutinosa under drought conditions.
Analyzed soil organic matter, organic carbon, and nitrogen under both alder species in a specific wetland region.
Examined the nitrogen form balance in the soil and nodule nitrogen-fixing activity for both species.
Studied the phylogenetic clades of Frankia strains associated with both alders and their microbial community functions.
Both alder species had similar effects on soil organic matter, carbon, and nitrogen accumulation.
Ammonium was the prevalent nitrogen form under both alders.
Nodule nitrogen-fixing activities did not differ between species or Frankia strains.
Functional microbial communities responsible for nitrogen cycling were equally abundant and active under both species despite slight variations.

Abstract

Wetlands provide a wide range of ecosystem services. However, climate change and its associated drought events are a direct threat to their integrity, notably to their fauna and flora and especially water supply dependent species. In wetland ecosystems, the temperate alder tree species Alnus glutinosa is dependent on the water supply and contributes to atmospheric nitrogen entry in N-cycling via its symbiosis with the actinobacteria Frankia. If A. glutinosa populations were to decline due to rainfall decrease, using another tree species as replacement could be considered, provided it could fulfil the same N-cycling functions. In the present study, we focused on the Dombes region, a French continental wetland in which rainfall decrease has been observed in recent years and we aimed to assess whether the Mediterranean alder species Alnus cordata, known to be more drought resistant, performs the N-cycling ecological function in the same way as the temperate species A. glutinosa. A. cordata and A. glutinosa had similar impacts on accumulation of soil organic matter, organic carbon and nitrogen. Alnus presence had an effect on nitrogen form balance in the soil, with ammonium being prevalent under both alders. Both alder species were colonized by the same two phylogenetic clades of Frankia strains and nodule N-fixing activities did not differ between species nor between Frankia strains. Abundances of soil N-cycling functional microbial communities and their activities (fixation, nitrification and denitrification) were found to be identical under both alder species despite slight differences in structure and diversity of those functional communities. In the Dombes, the Mediterranean species A. cordata performs its role in N-cycling in the same manner as the temperate climate species A. glutinosa while associating with the same symbiotic Frankia and functional microbial communities. These results are an interesting step for assessing the use of A. cordata as replacement of A. glutinosa in wetland restoration programs.

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Cite This Study

Henry et al. (Tue,) studied this question.

synapsesocial.com/papers/69e07c632f7e8953b7cbdb2f https://doi.org/https://doi.org/10.1186/s13717-026-00693-6

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