Search

With the continuous expansion of saline soils under climate change, understanding the eco-evolutionary tradeoff between the microbial mitigation of carbon limitation and the maintenance of functional traits in saline soils represents a significant knowledge gap in predicting future soil health and ecological function. Through shotgun metagenomic sequencing of coastal soils along a salinity gradient, we show contrasting eco-evolutionary directions of soil bacteria and archaea that manifest in changes to genome size and the functional potential of the soil microbiome. In salt environments with high carbon requirements, bacteria exhibit reduced genome sizes associated with a depletion of metabolic genes, while archaea display larger genomes and enrichment of salt-resistance, metabolic, and carbon-acquisition genes. This suggests that bacteria conserve energy through genome streamlining when facing salt stress, while archaea invest in carbon-acquisition pathways to broaden their resource usage. These findings suggest divergent directions in eco-evolutionary adaptations to soil saline stress amongst microbial clades and serve as a foundation for understanding the response of soil microbiomes to escalating climate change., (© 2024. The Author(s).)

Carbon (C) and nitrogen (N) coupling regulated by intensified microbial activity and turnover in the rhizosphere hotspots are essential for balancing C-N budgets, sustaining agroecosystem productivity and mitigating global climate changes. However, it remains unclear whether and how the (different) spatial distribution of root-derived C from rhizosphere to non-rhizosphere will regulate N transport and transformation. To address this, a rhizobox (100 × 80 × 80 cm) experiment was conducted on soils from the same site using 13C-CO2 (for 2 weeks) and 15 N-urea labelling for two cultivation systems, upland wheat and paddy rice. The paddy system showed larger proportion (43.5 versus 10.1%) of root-derived 13C retained into bulk soil, wider spatial transportation of both C and N (> 40 mm versus < 6.7 mm), higher proportion of plant-N uptake from soil pool (86.4 versus 62.3%), and higher loss of N derived from fertilizer pool (29.7 versus 13.2%), compared to the upland system. We identified that in paddy rice, larger amounts of N can be horizontally transported from bulk soil to the rhizosphere; the effects of root-derived C on N transformation mediated by soil microorganisms are more profound; higher plant uptake of soil-N as well as higher loss of fertilizer-N than those of upland wheat. Our results suggest that the transport and transformation of N are under the regulation of the spatial distribution of root-derived C and the associated microbial activities. This paves a new path towards proper management for weighing nutrient availability against fertilization reduction and balancing productivity with sustainability. [ABSTRACT FROM AUTHOR]