Fine root acclimation to different environmental conditions is crucial for the growth and sustainability of forest trees. Relatively small variations of absorptive root biomass may result in a large change in forest aboveground growth. To investigate the acclimation of absorptive roots to different environments and their relation to aboveground biomass, we investigated the relation between absorptive root biomass and associated aboveground biomass of Chinese fir in 6 stands in subtropical China that differed markedly in their local climate and edaphic conditions. The six populations of Chinese fir were from the central (Shaxian, Taihe and Huitong) to the marginal portions (Tongling, Nayong and Pingxiang) of the range in subtropical China. We analyzed fine root mass densities (FRMD, mg/cm3), aboveground biomass and its production rate to examine the relation of absorptive root to aboveground biomass.
Results/Conclusions
Generally, Chinese fir was found to have higher aboveground biomass but smaller fine root biomass in the centre than in the margins (P ＜0.05). The FRMD of absorptive roots in the central distribution areas (Shaxian and Huitong) were significantly lower than in other stands while the aboveground biomass in all the three central populations was higher than in the margins (Tongling, Nayong and Pingxiang). The aboveground net primary productivity per tree per year (ANPPtree, kg tree-1 y-1) was negatively correlated with the standing biomass of absorptive root biomass per tree (ARBtree, kg tree-1) (P <0.05). The ratio of ANPPtree to ARBtree in central distribution areas were higher than in marginal distribution areas and decreased significantly in the order Huitong> Shaxian> Tongling> Taihe> Pingxiang> Nayong, which were 108.7, 77.3, 22.3, 11.7, 10.5 and 8.8, respectively. These results suggested that in areas suitable for forest growth, trees allocate more biomass to aboveground and less biomass to fine roots, which coincided with the classification of traditionally central distribution areas and marginal distribution areas of Chinese fir in subtropical China.