长白松人工林采伐迹地火灾对土壤性质的影响

Effects of fire on soil properties of Changbai pine logging sites

【目的】研究长白松采伐迹地不同风速下的火灾对土壤性质的影响,并观测火烧后5年内土壤中营养元素含量的变化,为遭受火灾后的森林资源恢复提供科学依据。【方法】模拟长白松人工林采伐迹地发生火灾,利用热电偶测温系统得到火灾过程中土壤达到的最高温度,每隔半年进行1次灾后土壤的取样测量。采用折线图及柱状图的方法直观地描绘出不同风速条件下的火灾对土壤性质的影响。【结果】火灾释放的能量使表层土壤温度急剧升高,土壤性质会随之发生改变。当土壤温度超过200℃时,土壤受到高温作用会形成严重板结,容重大幅升高且在观测期内无法恢复至正常水平;土壤中有机质以及全氮含量的大量损失同样发生在200℃并难以天然恢复;全磷、全钾的大量损失发生于更高的温度,但火烧后土壤裸露会导致其持续损失;表层土壤速效磷、速效钾含量受到高温的作用在短期内显著升高。【结论】深层土壤的容重仅在低风速的火烧下升高,且各元素含量受火烧影响较小,5年内均可恢复至正常水平。浅层土壤的有机质会大量流失、土壤容重升高,但从火烧1年后开始缓慢恢复,有效营养元素含量也在火烧后初期有不同程度的升高,此时进行人工恢复可以使其得到有效利用。

【Objective】This article was aimed to explore the effects of fire on soil properties under different wind speeds in Changbai pine logging sites,and characterize the changes of nutrient elements in soil within five years after the fire,to provide a scientific basis for forest resource recovery after the fire.【Method】A fire in the logging site of Changbai pine plantation was simulated,and the thermocouple temperature measurement system was used to obtain the highest temperature of the soil during the fire.Afterwards,the post-disaster soil sampling measurement was carried out every six months.The effects of fire on the soil properties under different wind speed conditions were visually depicted by the method of line graph and bar graph.【Result】The energy released by the fire caused a sharp increase in the temperature of the surface soil,and the soil properties changed accordingly.When the soil temperature exceeded 200°C,severe compaction was formed under the high temperature.The bulk density of the soil increased significantly and cannot be restored to the normal level during the observation period.The loss of organic matter and total nitrogen in the soil also occurred at 200°C,which was difficult to recover naturally.A large amount of total phosphorus and potassium loss occurred at higher temperatures,and the soil was exposed after the fire,which would lead to its continuous loss.The content of available phosphorus and potassium in the surface soil increased significantly in a short period due to the effect of high temperature.【Conclusion】The bulk density of deep soil only increased under low wind speed fire,and the content of each element was less affected by fire,which can return to normal levels within five years.The organic matter in the shallow soil was greatly lost and the soil bulk density increased,which would be recovered slowly from one year after the fire.The content of available nutrients also increased to different degrees in the early stage after the fire.At this time,artificial restoration can be utilized effectively.