Environmental and species-specific controls on d 13 C and d 15 N in dominant woody plants from central-western Argentinian drylands

GABRIEL GATICA; JULIETA N. ARANIBAR; EDUARDO PUCHETA

AUSTRAL ECOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2016 vol. 41

1442-9985

Spatial variation in mean annual precipitation is the principal driver of plant water and nitrogen status in drylands. The natural abundance of carbon stable isotopes (d 13 C) in photosynthetic tissues of plants C 3 isan indicator of time-integrated behaviour of stomatal conductance; while that of nitrogen stable isotopes (d 15 N) is an indicator of the main source of plant N (soil N vs. atmospheric N 2 ). Previous studies in drylands have documented that plant d 13 C and d 15 N values increase with decreasing mean annual precipitation due to reductions in stomatal conductance, and soil enriched in 15 N, respectively. However, evidence for this comes from studies focused on stable isotope measurements integrated at the plant community level or on dominant plants at the site level, but little effort has been made to study C and N isotope variations within a species growing along rainfall gradients. We analysed plant d 13 C, d 15 N and C/N values of three woody species having different phenological leaf traits (deciduous, perennial and aphyllous) along a regional mean annual precipitation gradient from the central-western Argentinian drylands. Noticeably, plant d 13 C and d 15 N values in the three woody species did not increase towards sites with low precipitation or at the start of the growing season (drier period), as we expected.These results suggest that environmental factors other than mean annual precipitation may be affecting plant d 13 C and d 15 N. The short-term environmental conditions may interact with species-specific plant traits related to water and nitrogen use strategies and override the predictive influence of the mean annual precipitation on plant d 13 C and d 15 N widely reported in drylands.