¹⁵N methodologies for quantifying the response of N₂-fixing associations to elevated [CO₂]: A review

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• 作者：Phillip M. Chalk ^{chalkphillip@gmail.com" class="auth_mail" title="E-mail the corresponding author} ; Shu K. Lam ^{shukee.lam@unimelb.edu.au" class="auth_mail" title="E-mail the corresponding author} ; Deli Chen ; ^{delichen@unimelb.edu.au" class="auth_mail" title="E-mail the corresponding author}
• 关键词：15N ; δ15N ; Elevated [CO2] ; Legumes ; Symbiotic dependence ; Stable isotope tracer
• 刊名：Science of the Total Environment
• 出版年：2016
• 出版时间：15 November 2016
• 年：2016
• 卷：571
• 期：Complete
• 页码：624-632
• 全文大小：601 K

文摘

Methodologies based on ¹⁵N enrichment (E) and ¹⁵N natural abundance (NA) have been used to obtain quantitative estimates of the response of biological N₂ fixation (BNF) of legumes (woody, grain and forage) and actinorhizal plants grown in artificial media or in soil exposed to elevated atmospheric concentrations of carbon dioxide e[CO₂] for extended periods of time, in growth rooms, greenhouses, open top chambers or free-air CO₂ enrichment (FACE) facilities. ¹⁵N₂ has also been used to quantify the response of endophytic and free-living diazotrophs to e[CO₂]. The primary criterion of response was the proportional dependence of the N₂-fixing system on the atmosphere as a source of N. i.e. the symbiotic dependence (P_atm). The unique feature of ¹⁵N-based methods is their ability to provide time-integrated and yield-independent estimates of P_atm. In studies conducted in artificial media or in soil using the E methodology there was either no response or a positive response of P_atm to e[CO₂]. The interpretation of results obtained in artificial media or with ¹⁵N₂ is straight forward, not being subject to the assumptions on which the E and NA soil-cultured methods are based. A variety of methods have been used to estimate isotopic fractionation attendant on the NA technique, the so-called ‘B value’, which attaches a degree of uncertainty to the results obtained. Using the NA technique, a suite of responses of P_atm to e[CO₂] has been published, from positive to neutral to sometimes negative effects. Several factors which interact with the response of N₂-fixing species to e[CO₂] were identified.