Limited dependence on soil nitrogen fixation as subtropical forests develop

Area of Science:

• Soil Science
• Microbiology
• Ecology

Background:

• Nitrogen (N) fixation by soil microbes is vital for nutrient-poor ecosystems.
• The evolution of N fixation and soil diazotrophs during forest development is not well understood.

Purpose of the Study:

• To investigate how soil nitrogen fixation and diazotroph communities change throughout forest succession.
• To identify the drivers behind these changes in a 60-year forest rewilding chronosequence.

Main Methods:

• Utilized a 60-year forest rewilding chronosequence.
• Measured soil nitrogen fixation activity and diazotrophic microbial diversity and abundance.
• Analyzed soil acidification and nitrogen content.

Main Results:

• Soil N fixation activity decreased with forest age, dropping by 64.8% in intermediate and 93.0% in old forests.
• Diazotrophic diversity and the abundance of key diazotrophs (e.g., Desulfovibrio, Pseudomonas) significantly reduced in older forests.
• Forest succession-driven soil acidification and increased N content were identified as key drivers.

Conclusions:

• Forest development leads to a decline in soil N fixation and diazotroph populations.
• Changes in soil chemistry, specifically acidification and N enrichment, influence these microbial shifts.
• Understanding these dynamics is crucial for comprehending nutrient accumulation in developing forest soils.