Carbon (ä13C) and nitrogen (ä15N) stable isotope composition in plant and soil in Southern Patagonia’s native forests

PERI P.L.; LADD B.; PEPPER D.A.; BONSER S.P.; LAFFAN S.W.; AMELUNG W.

GLOBAL CHANGE BIOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2012 vol. 18 p. 311 - 321

1354-1013

Stable isotope natural abundance measurements integrate across several biogeochemical processes in ecosystem N and C dynamics. Here we report trends in natural isotope abundance (ä13C and ä15N in plant and soil) along a climosquence of 33 Nothofagus forest stands located within Patagonia, Southern Argentina We measured 28 different abiotic variables (both climatic variables and soil properties) to characterise environmental conditions at each of the 33 sites. Foliar ä13C values ranged from -35.4 to -27.7‰, and correlated positively with foliar ä15N values, ranging from -3.7 to 5.2‰. Soil ä13C and ä15N values reflected the isotopic trends of the foliar tissues and ranged from -29.8 to -25.3‰, and -4.8 to 6.4‰, respectively, with no significant differences between Nothofagus species (N. pumilio, N. antarctica, N. betuloides). Principal component analysis and multiple regressions suggested that mainly water availability variables (mean annual precipitation), but not soil properties, explained between 42 and 79 % of the variations in foliar and soil ä13C and ä15N natural abundance, which declined with increased moisture supply,. We conclude that a decline in water use efficiency at wetter sites promotes both the depletion of heavy C and N isotopes in soil and plant biomass. Soil ä13C values were higher than those of the plant tissues and this difference increased as annual precipitation increased. No such differences were apparent when ä15N values in soil and plant were compared, which indicates that climatic differences contributed more to the overall C balance than to the overall N balance in these forest ecosystems.