| Fine root is the most significant organ for trees because of its main function in absorbing water and nutrient for the growth of plants. The turnover of fine root plays an important role in biogeochemical cycles. We have two main objectives:1)one is to understand the spatial distribution fine roots of two dominant tree species in Badagongshan and compare the difference of fine root distribution between these two evergreen and deciduous trees; 2)the other is to examine the fine root architecture of different tree species and explore the relationship between fine root architecture and function, then to infer the relationship between fine root architecture and dominance of tree species in biota or evolution position of a certain tree species.Our research primarily consist of the following two parts:(1)The spatial distribution of available nutrient in soil is heterogeneous, resulting in the heterogeneous of the fine root spatial distribution. Here we choose the two dominant tree species (Cyclobalanopsis multinervis and Fagus lucida) and examine their fine root distribution in horizontal distance 50,80,120 cm, vertical depth 0-30 cm through drilling core method. We found that for both these two species, fine root biomass decreased along the depth of soil but no obvious trend on horizontal distance. The fine root biomass of deciduous tree specie Fagus lucida was significantly greater than that of the evergreen specie Cyclobalanopsis multinervis.(2) As a complex branch network, the morphology of fine root plays an important role in absorbing and its turnover. Since the network of fine root are different among different tree species, so exploring the morphology of species is significant to understand the belowground niche of different tree species and how they affect biogeochemical cycle. In this research, we studied root morphology across the first five root branch orders of 8 dominant and 5 rare tree species from a subtropical mixed forest in Badagongshan Nature Reserve, Hunan Province. Our objectives were to determine how root morphology (e.g., diameter, length, specific root length) changed across root branch orders and how such variation of fine roots differ between dominant and rare species. The results are summarized as following:the diameter, length and specific root length among 13 different species were of great variation. Diameter and length increased with the increasing root order, but specific root length decreased along the rising root order. The proportion of cumulative root length of the first three root orders is more than 80% in all species. The specific root length of endangered Davidia involucrate var. involucrate is much lower than other species and its diameter is larger. Compared to the six evolutional tree species, diameter and length of the first five root order in the seven ancient tree species were significantly lager, and specific root length was significantly lower than the evolutional ones, while there were no significant difference in the tissue density, carbon and nitrogen concentration. Since the root architecture is influenced by water, nutrient availability in soil and the genetic characters of species, our results suggest that the weak absorbing function of its root was one of the reasons for Davidia involucrate var. involucrate becoming rare and endangered.Conclusion:Fine root biomass of the two dominant tree species C multinervis and F lucida decrease with the depth of soil. There is no significant correlation between fine root biomass and horizontal distance or direction. The fine root biomass of deciduous specie F lucida is much more than the evergreen specie C multinervis. There is an siginificant trend between the root morphology (e.g. diameter, length, specific root length, tissue density et al.) and root order. Fine root morphology in different species was significantly different among species. Fine-root architecture showed no significant relationship with the dominance of trees, but it was influenced by the tree evolution status in a certain extent. |
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