Respiration and morphological characteristics of fine roots of two mangrove species by root branching order

To identify the functional traits of fine roots in mangrove species, we evaluated the root respiration rate and morphological traits, namely mean root diameter, specific root length (SRL), and root tissue density (RTD), using the root branching order classification in the two mangrove species. Although root respiration rates varied widely (0.63−12.76 and 0.42−6.55 nmol CO2 g－1 s－1, respectively), there was a trend toward higher respiration rates for the smaller diameter roots. Only root respiration rates of first-order roots of Bruguiera gymnorrhiza were significantly higher than those of higher order roots. There were differences in SRL, RTD, and root diameter between first two order roots and forth-order roots of both species, except for SRL of second- and forth-order roots of B. gymnorrhiza. First-order roots of Rhizophora stylosa differed significantly from that of B. gymnorrhiza in respiration rate, SRL and RTD, showing the characteristics of species. Fine root respiration and morphological traits by order classification may reflect differences in the functional traits of roots. Further research on the physiomorphological differentiation of fine roots would improve our understanding of various tolerance and adaptation strategies for environmental stress, among mangrove species.