Assessment of 15N natural abundance in leaves of Coriaria ruscifolia and other plant species occurring in humid forests of northwest Patagonia

CHAIA E; MYROLD D; HUSS-DANELL K; WALL LG

Porto

Congreso; 16 International meeting on Frankia and actinorhizal plants; 2010

The actinorhizal species from Northwest Patagonia growing in the semiarid steppe, Ochetophila trinervis and Discaria chacaye (Rhamnaceae), have a foliar natural abundance of 15N (δ15N) different than that of reference plants and fix considerable amounts of N (Chaia & Myrold, 2010). Corresponding information about actinorhizal plants growing in the humid forests of the region is lacking. To better understand the role of native actinorhizal plants in the N economy of northwest Patagonian ecosystems we assessed the foliar δ15N and N concentrations of Coriaria ruscifolia (Coriariaceae), the rhamnaceous species D.chacaye and Colletia hystrix, and some non-actinorhizal species growing adjacent to or distant from the actinorhizal plants at four sites. In addition, concentrations of N and δ15N of soils under sampled plants were measured. Foliar N concentrations in C. ruscifolia, D. chacaye and C. hystrix were significantly higher than in non-actinorhizal shrubs growing at the same sites, even though soils under the studied plants had very low and similar N concentrations. Foliar N concentration in reference plants growing either adjacent to or distant from the actinorhizal plants was similar. Foliar δ15N of C. ruscifolia, D. chacaye and C. hystrix was close to 0 and was not correlated wih soil δ15N values across the sites. A tendency towards higher foliar δ15N mean values in actinorhizal plants than in most non-actinorhizal plants was observed in three out of four studied sites. Preliminary evaluation of the data indicates that all studied actinorhizal species fix atmospheric nitrogen in the humid Patagonian forests.