N-15 methodologies for quantifying the response of N-2-fixing associations to elevated [CO2]: A review

作者：Chalk Phillip M; Lam Shu K; Chen Deli^*

来源：Science of the Total Environment, 2016, 571: 624-632.

DOI：10.1016/j.scitotenv.2016.07.030

• N-15
• delta N-15
• Elevated [CO2]
• Legumes
• Symbiotic dependence
• Stable isotope tracer

Methodologies based on N-15 enrichment (E) and N-15 natural abundance (NA) have been used to obtain quantitative estimates of the response of biological N-2 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. N-15(2) 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 N-2 -fixing system on the atmosphere as a source of N. i.e. the symbiotic dependence (Palm). The unique feature of N-15-based methods is their ability to provide time-integrated and yield-independent estimates of Palm. 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 N-15(2) 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 Pat, to e[CO2] has been published, from positive to neutral to sometimes negative effects. Several factors which interact with the response of N-2 -fixing species to e[CO2] were identified.

• 出版日期2016-11-15