It is increasingly recognized that tree fine roots (<2mm in diameter) are not composed of homogenous units as traditionally assumed. Instead, they include groups of individuals that differ markedly both in structure and function. Fine root respiration is a significant component of carbon cycling in forest ecosystems, however, it is commonly measured according to arbitrary diameter class. To date, few studies have focused on fine root respiration and its relationship with fine root morphology and nutrients across of different root orders, because of the numerous difficulties associated with its measurements,especially in subtropical evergreen broad-leaf forest. So in this study, intact fine root segments of six dominant tree species (Cinnamomum micranthum; Tsoongiodendron odorum Chun; Cinnamomum chekiangense; Castanopsis fabri; Altingia gracilipes; and Castanopsis carlesii) in an evergreen broadleaved forest located at the Wanmulin Nature Reserve, Jian'ou, Fujian province, were collected by excavation, separated into different root orders, and then measured for respiration rate by an Li-6400 portable photosynthesis system. We here aimed to examine the following three questions: (1) the relationship between specific root respiration (SRR) and root order; (2) the effect of root order and tree species on SRR; and (3) the relationship of SRR with specific root length (SRL) and tissue N concentration. The one-way and two-way ANOVA revealed that: tree species, root order and tree species × root order all had significant effects on SRR (P<0.01 for all cases). SRR ranged from 0.625 to 1.79 μgC·g^-1·s^-1 for the lowest root order, and significantly declined with increasing root order, which was consistent for the six tree species(P<0.01). This decline, however, differed among species, with SRR decreased most sharply for Cinnamomum chekiangense. The regression analysis showed that SRR changed systematically with root order, which could be represented by quadratic, cubic, exponential or power functions. Across all the root orders, SRR was positively correlated both with SRL and nitrogen concentration for each tree species (P<0.01). Across all the six species, SRR was positively correlated (P<0.01) with SRL only in the third order, and there was no correlation between SRR and nitrogen concentration in all the five root orders. When pooled by all the tree species and root orders, SRR was positively correlated both with SRL and nitrogen concentration (P<0.01). These means that both SRL and nitrogen concentration could only reflect the intra-species but not the inter-species variations of SRR. The analysis of covariance demonstrated that: tree species had significant effected on (P<0.01)the slope of the regression straight line which between SRR and SRL, but root order had no significant effected on slope and intercept of the regression straight line, these means the correlation between SRR and SRL was significantly affected by tree species but not by root orders, and the correlation between SRR and nitrogen concentration was significantly affected both by tree species and root orders. It is concluded that there existed evident functional heterogeneity among fine roots of different branch orders, and SRL could reflect this heterogeneity only in specific tree species.