Abstract:

Objective: This study is intended to investigate the effect of planting Stropharia rugosoannulata under Larix gmelinii and Betula platyphylla forests on the flammability of litter layer in the Greater Khingan, and to develop a method to combine forest fire prevention with underforest economy. Method: After the period of forest fire prevention, a stand of 2 500 m² was set up in each of the L. gmelinii and the B. platyphylla forests of Zhuangzhi forest farm of Songling Forestry Bureau in June 2020, and 12 sample quadrats of 70 cm×70 cm were set up in each stand (2 stands, canopy density about 0.7). The litter was used as the cultivation substrate to plant S. rugosoannulata. Four densities of the control (0 bags), low (2 bags), medium (4 bags), and high (6 bags) were set up according to the number of fungus bags planted in each quadrat. After mushroom harvesting, the litter samples were collected and taken back to the laboratory for thermogravimetric experiments, the calorific value and ignition point were measured, and the thermogravimetric indicators of holocellulose and lignin such as thermal weight loss proportion, weight loss ratio and thermal degradation kinetics were analyzed. Meanwhile, we calculated and compared the difference in flammability index and comprehensive burning index. Result: The activation energy and calorific value of holocellulose in litter under L. gmelinii forest decreased with the increase of planting density of S. rugosoannulata, and were lower in medium and high densities, in which the activation energy of holocellulose decreased by 36.39% and 35.07%, respectively, and the calorific value decreased by 74.21% and 76.81%, respectively. The activation energy of holocellulose of litter under B. platyphylla forest decreased significantly under medium and high density (P < 0.05), it was the lowest at low density, which decreased by 32.97%. The trend of calorific value was consistent with the litter of L. gmelinii forest, which was still lower under medium and high densities, and decreased by 78.75% and 72.07%, respectively. Conclusion: Underforest planting of S. rugosoannulata had the effect of reducing the comprehensive burning index of the litter in L. gmelinii forest and B. platyphylla forest, the litter planting with medium and high density S. rugosoannulata had the better effect in reducing the comprehensive burning index, and the comprehensive burning index of litter under the medium and high planting density in L. gmelinii forest decreased by 86.74% and 87.51%, respectively, and the comprehensive burning index of litter under the medium and high planting density in B. platyphylla forest decreased by 93.63% and 91.52%, respectively. Future study can explore the optimal planting density with both fire prevention benefit and mushroom yields.

Key words: flammability, Stropharia rugosoannulata, forest litter layer, Greater Khingan, thermogravimetry