Symbiotic and Free-Living N2 Fixation in Subtropical Pueraria lobata Communities of Southwest China,Journal of Geophysical Research: Biogeosciences

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Symbiotic and Free-Living N2 Fixation in Subtropical Pueraria lobata Communities of Southwest China
Journal of Geophysical Research: Biogeosciences ( IF 3.7 ) Pub Date : 2021-06-25 , DOI: 10.1029/2021jg006282
Junniu Zhou _{1,

2,

3,

4} , Jiangming Ma _{2,

3} , Dejun Li _{1,

4}

Affiliation

Biological N₂ fixation plays crucial roles in determining the pattern and pace of ecological succession and carbon sequestration. Nevertheless, the rates and controls of symbiotic (SNF) and free-living (FNF) N₂ fixation have rarely been investigated simultaneously. Here we measured SNF and soil FNF rates for eight early succession ecosystems dominated by kudzu (Pueraria lobata (Willd.) Ohwi) in a subtropical region of China in growing and nongrowing seasons. N₂ fixation rates were measured using acetylene reduction assay against a ¹⁵N₂ uptake method. Both SNF and soil FNF rates were significantly higher in the growing season than in the nongrowing season. The two forms of N₂ fixation contributed equally to total N₂ fixation rate across the eight sites with soil FNF being higher than SNF in half of the sites. Total N₂ fixation rates ranged from 7.12 to 61.93 kg N ha⁻¹ yr⁻¹ with an average of 22.93 ± 6.52 kg N ha⁻¹ yr⁻¹. N₂ fixation contributed significantly to soil nitrogen and carbon accumulation. Both SNF and FNF were significantly related to soil moisture. Additionally, SNF and soil FNF were strongly correlated with phosphorus availability and vanadium/iron availability, respectively, most likely implying that SNF was limited by phosphorus and soil FNF was limited by vanadium or iron. Our findings suggest that SNF and soil FNF may be limited by different sets of nutrients within an ecosystem.

更新日期：2021-07-22

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