Rainfall events stimulate episodic associative nitrogen fixation in switchgrass

IF 3.9 3区 环境科学与生态学 Q2 ENVIRONMENTAL SCIENCES
Carmella Vizza, Matthew A. Belanger, Jabarius Jones, Sean J. Murphy, Daniel H. Buckley, G. Philip Robertson, Sarah S. Roley
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Abstract

Associative N2 fixation (ANF) is widespread but poorly characterized, limiting our ability to estimate global inputs from N2 fixation. In some places, ANF rates are at or below detection most of the time but occasionally and unpredictably spiking to very high rates. Here we test the hypothesis that plant phenology and rainfall events stimulate ANF episodes. We measured ANF in intact soil cores in switchgrass (Panicum virgatum L.) in Michigan, USA. We used rain exclusion shelters to impose three rainfall treatments with each receiving 60 mm of water over a 20-day period but at different frequencies. We concurrently established a treatment that received ambient rainfall, and all four treatments were replicated four times. To assess the effects of plant phenology, we measured ANF at key phenological stages in the ambient treatment. To assess the effects of rainfall, we measured ANF immediately before and immediately after each wetting event in each treatment involving rainfall manipulation. We found that the previous day’s rainfall could explain 29% of the variation in ANF rates within the ambient treatment alone, and that bulk soil C:N ratio was also positively correlated with ANF, explaining 18% of the variation alone. Wetting events increased ANF and the magnitude of response to wetting increased with the amount of water added and decreased with the amount of inorganic N added in water. ANF episodes thus appear to be driven primarily by wetting events. Wetting events likely increase C availability, promote microbial growth, and make rhizosphere conditions conducive to ANF.

Abstract Image

降雨事件刺激开关草的偶发性联合固氮作用
关联氮固定(ANF)很普遍,但特征不明显,这限制了我们估算氮固定全球输入的能力。在一些地方,大部分时间氮固定率处于或低于检测水平,但偶尔会不可预测地飙升到很高的水平。在这里,我们验证了植物物候和降雨事件会刺激氮固定率上升的假设。我们测量了美国密歇根州开关草(Panicum virgatum L.)完整土芯中的 ANF。我们使用防雨罩施加了三种降雨处理,每种处理在 20 天内降雨量为 60 毫米,但降雨频率不同。同时,我们还设置了一个接受环境降雨的处理,所有四个处理均重复四次。为了评估植物物候的影响,我们在常温处理的关键物候期测量了 ANF。为了评估降雨的影响,我们在每个降雨处理中,在每次降雨前和降雨后立即测量ANF。我们发现,仅前一天的降雨量就能解释环境处理中 ANF 变化率的 29%,而土壤容重 C:N 比率也与 ANF 呈正相关,仅此就能解释 18% 的变化。湿润事件增加了ANF,对湿润的响应程度随加水量的增加而增加,随水中无机氮添加量的增加而减少。因此,ANF 的变化似乎主要是由湿润事件驱动的。湿润事件可能会增加碳的供应量,促进微生物生长,并使根圈条件有利于 ANF 的形成。
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来源期刊
Biogeochemistry
Biogeochemistry 环境科学-地球科学综合
CiteScore
7.10
自引率
5.00%
发文量
112
审稿时长
3.2 months
期刊介绍: Biogeochemistry publishes original and synthetic papers dealing with biotic controls on the chemistry of the environment, or with the geochemical control of the structure and function of ecosystems. Cycles are considered, either of individual elements or of specific classes of natural or anthropogenic compounds in ecosystems. Particular emphasis is given to coupled interactions of element cycles. The journal spans from the molecular to global scales to elucidate the mechanisms driving patterns in biogeochemical cycles through space and time. Studies on both natural and artificial ecosystems are published when they contribute to a general understanding of biogeochemistry.
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