Fine Root Architecture In Fraxinus Mandshurica And Larix Gemilini

It is widely appreciated that a better understanding of the plant root architecture and function variation is a very important research objectives. The study will provide basic scientific data for the root system modular building, and also contribute to the precise evaluation of carbon and nutrient dynamic at the ecosystem scale. We studied architecture characteristics (diameter, length and specific root length etc.) of different fine root branch orders between two tree species Larix gmelini and Fraxinus mandshurica on Maoershan Forest Research Station (45°21'-45°25'N, 127°30'-127°34'E) which owned by Northeast Forestry University, China. Both ash and larch forests were planted in 1986. We collected the fine root samples from two soil depths (i.e., 0-10cm, ll-20cm) in May 15, July 15 and September 15 of 2003. After washing, the root system was dissected into 5 orders, except the 1x order roots from higher order roots. After dissecting, fine root length, diameter and dry weight of a given order were determined. The objective of this study was to examine how root length, diameter, specific root length (SRL) were related to root branching pattern and their variation with different season or soil depth.The results show that mean diameters (p<0.001) and length (P<0.05) of fine root are different significantly from first-order to fifth-order, and increased regularly with increasing root order in both species. But the SRL and total length on a unit area decreased obviously with the increasing root order. The mean diameters of first-order roots were 0.26mm for ash and 0.34mm for larch, and that of the fifth-order roots were 1.54mm and 1.70mm for ash and larch each respectively. When the diameters are smaller than 2mm and 1mm, fine roots of both species include five orders (ash) and four orders (larch) respectively. If the diameters of fine roots are defined as less than 0.5mm, previous three orders for ash roots and two orders for larch roots would be included as fine root population. Within the same root orders, variations of fine root diameter are also obvious. Diameter ranges increased with increasing root orders. These results suggest that both diameter and order cannot be ignored in estimating fine root life span and turnover. Total length of first three order roots constitute 95.3% and 85.7% of all five order root length, and their SRL ware much higher than the 4 and 5 order roots, which are the most important water and nutrients absorb component, 1x order roots from the higher order roots make up 12% of total root length, should not be ignored also. Response to the resource availability, number and architecture of each order roots present clearly season and depth variation. Because finer roots (1-3 orders) were larger in total number and length, therefore, their death had an important influence on the nutrient uptake, soil nutrient cycle and C allocation in plants.