计划烧除对马尾松人工中龄林土壤的短期影响

Short-term Effects of Prescribed Burning on Soil under Middle Aged Pinus Massoniana Plantation

计划烧除是预防人工林森林火灾发生的主要措施之一,研究火烧迹地土壤特征对理解土壤生态系统结构、功能及火后植被恢复具有重要意义。以黄丰桥林场马尾松人工中龄林为研究对象,按地表可燃物载量设置对照(CK)、低(PB1)、中(PB2)、高(PB3)4种火强度梯度处理。4种处理样地土壤表面温度峰值分别为17、151、322和564℃,峰值温度持续10 min左右,温度高于100℃的持续时间分别为0、19、43和54 min。土壤pH值随火强度的增大而上升,随着时间的推移,土壤pH值逐渐下降,对照与PB1样地(2个月后)差异不明显,但4个月内PB2与PB3样地之间平均pH值差异显著。4种处理样地表层土壤有机碳存在显著差异,土壤有机碳含量随火强度的增大而减少。PB1、PB2、PB3样地的土壤砂石含量增加,而黏土含量减少。对照样地土壤团聚体和平均重量直径没有显著变化,但计划烧除后短期内平均重量直径随火强度的增大而增大,PB1、PB2、PB3样地分别增加0.21、0.25和0.38 mm。6个月内各处理间土壤斥水性差异显著,表层土壤斥水性随火强度增大而增加,PB1、PB2、PB3样地的土壤斥水性1个月内分别达231、454、665 s,分别为对照样地的23、45、66倍。试验结果为火干扰后土壤质量评价及植被恢复提供参考。

Prescribed burning is one of the most important measures for forest fire prevention in plantation. It is important to understand soil ecosystem structure, function, and vegetation restoration of burned forest sites. In order to reveal the short-term effects of soil physical and chemical properties after prescribed burning, we took middle aged Pinus massoniana plantation as research object from the Huangfengqiao State Forest Farm, Zhuzhou, Hunan Province, China. Four fire intensity treatments consisting of control （CK： 0 t hm-Z）, low （PBI： 25 t hm-2）, medium （PB2：50 t hm-2）, and high （PB3：100 t hm-2） were set up. Immediate changes in soil properties under different treatments were studied and monitored monthly during a 6-month period. Soil surface peak temperatures at each plot were 17 ℃, 151 ℃, 322 ℃, and 564℃, respectively, in four fire intensity treatments. The peak temperature lasted about 10 min. Temperature higher than 100 ℃ of prescribed burning Iasted 0 min, 19 min, 43 min, and 54 min, respectively. Soil pH generally increased with increasing temperature or fire intensity. As time went by, soil pH gradually reduced. The difference of pH was not obvious between control and PB 1 after two months, but there were significant differences between PB2 and PB3. There were significant differences in surface soil organic carbon among four treatments. The content of soil organic carbon decreased with prescribed burning intensity enhancement. The content of sand in PB1, PB2, and PB3 increased after prescribed burning, but the content of clay decreased. The change of aggregate and mean weight diameter were not significant in control sample, but it increased by 0.21 mm, 0.25 ram, and 0.38 mm with the fire intensity enhancement, respectively, in PB1, PB2, and PB3 samples. There were significant differences in soil water repellency among four treatments. Soil water repellency increased with the fire intensity enhancement. And it was 231 s, 454 s, and 665 s, respectively, which was 23, 45 and 66 times, respectively, in PB1, PB2, and PB3 samples than in control sample. The results can provide references for assessing soil quality and restoring vegetation of burned forest.