Spatial And Temporal Distribution Of Fine Root Biomass Of Dominant Tree Species And Changes After Fire On Great Xing'an Mountains

1. With Larix gmelinii and Betula platyphylla forests as test objects, their fine roots were sampled to analyze biomass level, distribution and seasonal dynamics. The results showed some differences, the annual average fine roots biomass (≤5mm) of Larix gmelinii and Betula platyphylla were 371.64g·m-2 and 402.87g·m-2. Fine roots horizontal distribution was similar. Fine roots biomass of Larix gmelinii showed maximum value (411.22g·m-2) in the midpoint of stem and the edge of canopy projection, then on the edge of canopy projection were 364.94g·m-2, and the minimum value (338.78g-m-2) appeared close to the stem. Betula platyphylla were 445.87g·m-2,437.32g·m-2 and 325.45g·m-2, respectively. Fine roots biomass vertical distribution was affected by the differences of physical and chemical properties of soil. Fine roots biomass of two forests in the 0～10cm layer was 52.20% and 57.78%. Fine roots biomass of two forests showed significant seasonal dynamics in the growing season. The minimum value appeared in May. The maximum value of Larix gmelinii (598.80g·m-2) appeared in July, while Betula platyphylla (528.97g·m-2) appeared in September.2. With Larix gmelinii forest as test objects in tahe forestry on Great Xing'an Mountains, take the investigation of forests burned at different times, their roots were sampled to analyze the change of root biomass, C, N nutrient concentration and C/N value after the fire. The results showed that:1)One week after fire, live root biomass of low-intensity and moderate intensity burning trees were only 80% and 36% of control trees, fine root biomass of≤1mm diameter were 60% and 19% of control trees, respectively; 2)Three months after fire, fine roots of low-intensity burning trees had came to a certain degree of recovery, fine roots of moderate intensity burning trees was significantly lower than the degree of recovery of low-intensity burning trees. Two years after fire, there was no significant difference between the former tree root biomass and the control, and there was no significant difference between fine root biomass of≤lmm diameter of the latter trees and the control; 3) Fire reduced tree root nutrient concentrations of carbon and nitrogen, low-intensity burning decreased the value of C/N, however, moderate intensity burning increased the value of C/N.