Characteristics and influence factors in leaf and soil carbon stable isotopes of Caragana jubata.

Abstract

In order to explore the relationship of plant carbon (C) cycling with its habitat in the high-altitude regions, a leguminous shrub, Caragana jubata, that mainly distributed in those areas was studied. We collected leaf and soil samples of C. jubata from 35 sites along an east-west transect across the alpine regions of China. We measured leaf carbon stable isotope (δ13C), soil δ13C, and the difference between leaf and soil δ13C (Δδ13C) of each sampling site. We further analyzed the effects of climatic factors, leaf and soil elements on leaf δ13C, soil δ13C and Δδ13C. Results showed that leaf δ13C ranged from -30.9‰ to -27.1‰, with a mean value of -28.4‰, soil δ13C ranged from -26.2‰ to -23.2‰, with a mean value of -25.3‰, and Δδ13C ranged from 2.0‰ to 7.7‰, with a mean value of 3.1‰. δ13C values of leaf was significantly lower than that of soil. Soil δ13C initially decreased and subsequently increased with increasing leaf δ13C. Leaf δ13C was negatively correlated with growing season temperature and leaf C content. Soil δ13C was negatively correlated with relative humidity and mean temperature of the warmest month, and was positively correlated with soil carbon:nitrogen (C:N). Soil δ13C firstly decreased and subsequently increased with soil C content. Δδ13C was positively correlated with leaf C content, soil C content, and soil C: N. Climatic factors directly affected leaf δ13C and Δδ13C, and indirectly affected leaf δ13C, soil δ13C and Δδ13C through their effects on leaf and soil elements. The C cycle of C. jubata was affected by climatic factors, leaf and soil elements in the alpine regions.