Abstract:

The forest combustibility played a decisive role in forest fire prevention, and could have a great impact on the success of vegetation restoration in the rocky desertification area. In order to study the combustibility of the young vegetation restoration stands in the rocky desertification area, four patterns of vegetation restoration stands were chosen in the rocky desertification area in the Southwest region of Hunan Province, and they were Pinus elliottii pure forest (PEPF), Platycladus orientalis pure forest (POPF), Pinus elliottii and Liquidambar formosana mixed forest (PLMF), Liquidambar formosana and Platycladus orientalismixed forest (LPMF). The efficient fuel loading (EFL), relative moist content (RMC), dehydration rate, gross caloric value (GCV), and the efficient fuel energy were measured and analyzed in sample plots. The results showed: 1) The main fuel types were Imperata cylindrica, Verbena officinalis, and some shrubs in the young vegetation restoration stands in the rocky desertification area. 2) The EFL of the 4 patterns of vegetation restoration stands were all high, between 5.16 and 9.89 t·hm^-2, and the POPF had the highest EFL which was 9.89 t·hm^-2. 3) RMC was lower in the fire risk season (autumn and winter in Hunan province), between 17.8%－42.6%, with lowest in the litter and I. cylindrica in POPF. The POPF had the lowest average RMC and the most rapid dehydration rate among the 4 patterns of stands, and hence the greatest combustibility, whereas the PLMF was opposite, with the highest RMC and the smallest combustibility. 4) The GCV of the major fuel types was between 11.7－20.8 kJ·g^-1 in the 4 stand patterns. Through analysis of variance we found that there was no significant difference in GCV of the same fuel type in different stand patterns, except for the litters. And there was no significant difference of the weighted average GCV in the 4 different stand patterns, which value were between 17.37－18.03 kJ·g^-1. 5) The order from high to low of the efficient fuel energy was: POPF, PEPF, PLMF, LPMF. The highest efficient fuel energy was 176.69×10⁶ kJ·hm^-2 in POPF, and the lowest was 92.73×10⁶ kJ·hm^-2 in LPMF. 6) From these features of the young stands we can see that the forests of the 4 patterns all had great combustibility, and the pure forest had a higher combustibility than the mixed forest. Therefore, for the purpose of forest fire protection, we should choose mixed forests instead of pure forests, and it is necessary to clean the forest in time and reduce the EFL, during the process of vegetation restoration in the rocky desertification area.

Key words: Shaoyang county, rocky desertification, efficient fuel, fuel loading, gross caloric value