Spatial distribution of roots and nodules and d 15 N evidence of nitrogen fixation in Adesmia volckmanni; a Patagonian leguminous shrub

GOLLUSCIO RA; FAIGÓN SOVERNA A; TANKE M

JOURNAL OF ARID ENVIRONMENTS

ACADEMIC PRESS LTD-ELSEVIER SCIENCE LTD

Año: 2006 vol. 67 p. 328 - 333

0140-1963

Descriptions of the spatial distribution of nodules and their relationship with the distribution of roots are extremely rare in leguminous shrubs of arid ecosystems. In this paper we show that in the Patagonian arid steppe the spatial distribution of nodules of Adesmia volkmanni Philippi (ex- A. campestris) paralleled that of their roots. Nodules and roots of A. volkmanni were concentrated in intermediate (70?90 cm) soil layers, but did not appear to be biologically active (no visual signs of leghaemoglobin).In addition, leaves showed the same natural 15N abundance (d 15N) than those of another native shrub species, Mulinum spinosum, a known non-fixer with the same rooting and phenological patterns. However, high leaf N content, presence of nodules, and clear isotopic differences between the two species in a more humid site suggest that nitrogen fixation could occur in some favourable years in Adesmia volkmanni plants of xeric sites.