Hydraulic architecture of three Caragana species and its relationship with environmental factors in different habitats of the Inner Mongolian Plateau, China

Hydraulic architecture and its relationship with environmental factors were studied in three Caragana species, namely, Caragana microphylla Lam., C. davazamcii Sancz and C. korshinskii Kom, which were found in different habitats of the Inner Mongolian Plateau, China. The improved flushing method was used in situ on one-year-old twigs for comparing the hydraulic efficiency and the regulating abilities of these three species as well as their mechanisms of regulating water transport to cope with variable environments. The relationship between hydraulic architecture and air temperature followed a linear function with negative slope, whereas the relationships between these parameters with atmospheric humidity were positive. Comparing the hydraulic efficiency among the three seasons, a descending order was given as summer>spring>autumn. In the same season, the hydraulic efficiency of C. korshinskii was higher than that of C. davazamcii, which was in turn higher than that of C. microphylla. It can be concluded from the range of Ks and the slope of two linear functions that there were significant differences in the sensitivity of specific conductivity to environmental factors, both among species and among seasons, with a descending order as summer>spring>autumn. In the same season, C. korshinskii was the most sensitive to the changes of environment, and the sensitivity of C. davazamcii was higher than that of C. microphylla. The results also supported the view that the reduction of hydraulic efficiency because of the embolism in xylem could benefit the plants subjected to water deficit by means of limiting water loss.