Root Structure Of Five Tree Species In Northeast China

The root plays an important role in the cycles of carbon and nutrient in terrestrial ecosystem. Previous studies focused on fine root which was defined as diameter less than a level or the first 5 orders, for example the diameter less than 2 mm,. Those fine roots often have thin diameter and active ability in ecosystem. Simultaneity it is a key factor to understand the role of fine roots in ecosystem. But no study on the whole root system was reported. So we are not clear what root structure is. In this study, we excavated the whole root systems of spruce (Picea koraiensis), korean pine (Pinus koraiensis), and linden bran (Tilia mandshurica), in Liangshui National Nature Reserve and Davurian larch (Larix gmelinii), Manchurian ash (Fraxinus mandshurica) in Jianlagou Silviculture Experimental Station. We divided the root system following the river branching approach into several orders, and measured the morphology factors of each order such as mean diameter, mean individual root length and specific root length, and also architecture factors of each order described as branching ratio, internode's length and branching density. Also we assessed the total root biomass of the whole root system which is corrected by ash. At last we did regress on the relationships between the total biomass and root basal diameter, and the relationships between morphology and architecture factors and orders. The results as follow:The whole root systems of the five species we studied follow the speculation of self-similar fractal conducted by West et al. Especially the relationship between root numbers and root orders behaving as decreasing and the relationship between mean root length and root orders behaving as increasing with increasing root orders. For total cross-sectional area of each order, only 3-7orders followed the speculation of self-similar fractal. The total cross-sectional area of 1, 2, 8 and higher orders having significantly difference didn't follow the speculation of self-similar fractal.From the comparisons of morphology and architecture among five species, we found that the root diameter, root length, and internode's length steadily increase but the specific root length, branch ratio, and branch density distinctly decreasing with increasing root orders. This maybe is the potential regulation of vascular plants because it is right in different species from different spaces.From the regressions between root morphology, root architecture and root orders we found that the morphology characters (Diameter, Root length and Specific root length) of five species have two-dimension exponential relationship with root orders. However, the root architecture is complex. The branch ratio also is have two-dimension exponential relationship with root orders, but only the two broadleaf species' internode's length and branch density have two-dimension exponential relationship with root orders, the three conifer species' internode's length and branch density fitted parabola regression. Particularly the regression correlation coefficient of linden bran (T. mandshurica) didn't achieve significantly level which less than 0.5000.Our results indicate that there are mathematics relationships between root morphology, architecture and root orders. So we can indicate root characters through mathematics equation. This maybe a new way to study root system without destroyed sampling. Moreover, this dissertation studies the morphology of individual root and the architecture of root system through the whole body, providing comprehensive and foundational data for designing root system model.