不同火干扰强度对枫香次生林土壤理化性质的影响

火干扰是影响森林土壤生态系统结构与功能的重要因素之一。探讨火干扰后森林土壤理化性质的动态特征,为火后植被恢复以及森林可持续经营提供重要的理论指导。2014—2016年在湖南省株洲市枫香次生林内设置16块20 m×20 m样地进行试验,研究4种火干扰强度(对照、低强度、中强度、高强度火烧)后不同时间节点(火烧后3,30,180,360,720天)的枫香次生林的土壤容重(BD)、土壤斥水性(SWR)、有机质(SOM)、pH、全氮(TN)、全磷(TP)和全钾(TK)等指标。通过描述性统计、单因素方差分析和Fisher LSD检验研究了土壤性质在同一时间节点不同火干扰强度之间以及同一火干扰强度下不同时间节点间的显著性差异(p0.05)。结果表明:火干扰后各时间节点下,BD、SWR、pH、TK均随火强度增大而增加,而SOM和TP随火强度增大而降低,不同火干扰间TN均不存在显著性差异。同一时间节点内火干扰土壤与对照相比,低强度火干扰对BD、SWR、pH和SOM的影响不显著,中强度火对部分时间节点下的土壤理化性质有影响,而高强度火对其影响均比较显著。同一强度火干扰后,BD、SWR、pH在不同时间节点间存在显著性差异,BD、SWR、pH在火烧后3天显著增大,然后逐渐减少;BD在火后360天恢复到火烧前状态,而SWR、pH则需720天。SOM仅在高强度火烧后360,720天与其他时间节点间存在显著性差异;火干扰后,SOM与火烧前相比先减少,后逐渐上升,火后360天逐渐恢复到火烧前的水平并维持稳定。中、高强度火干扰后,时间节点跨度越大,TK的差异越显著,而TN和TP仅在高强度火烧后差异显著。研究发现火干扰强度和时间节点对7种土壤性质均有一定影响,其中高强度火干扰对土壤理化性质影响最大。火干扰后短期内引起地力衰退,影响林地土壤养分状况,对土壤生态系统产生重要影响,但随着时间推移,2年后土壤理化性质基本恢复到火烧前的水平。

Effects of Fire Disturbance on Soil Physiochemical Properties in Liquidambar formosana Secondary Forest

Fire disturbance is one of the important factors affecting the structure and function of forest soil ecosystem. In order to provide theoretical guidance for forest regeneration and sustainable management after fire disturbance, this study explored the dynamic characteristics of physiochemical properties in forest soil after different fire disturbances. The effects of fire intensities (control, low, moderate and high intensity fire) and time nodes (3, 30, 180, 360, 720 days after fire) on bulk density (BD), soil water repellency (SWR), soil organic matter (SOM), pH, total nitrogen (TN), total phosphorus (TP) and total potassium (TK) contents were measured in a field-scale experiment with 16 plots (20 m×20 m) from Liquidambar formosana secondary forests in Zhuzhou, Hunan Province, China from 2014 to 2016. The differences and changing trends of soil properties among different fire disturbances at the same time node and different time nodes under the same fire disturbance were studied by descriptive statistical analysis, one way ANOVA and Fisher LSD test (p<0.05). The result showed that BD, SWR, pH, and TK increased with the increase of fire intensities, while SOM and TP decreased after the fire disturbance at the same time node. There was no significant difference of TN among different fire disturbances. Compared with the control, the effects of low intensity fire on BD, SWR, pH and SOM were not significant at the same time node, the effects of moderate intensity fire on these soil physiochemical properties were significant at some time nodes, while the effects of high intensity fire on them were significant. After the same intensity of fire disturbance, there were significant differences in BD, SWR and pH among different time nodes (p<0.05). BD, SWR and pH increased significantly at the first three days after fire, then decreased gradually; BD returned to pre-fire level after 360 days of fire, while SWR and pH needed 720 days after fire. However, there were significant differences of SOM between 360, 720 days and other time nodes only after high intensity fire. After fire disturbance, SOM decreased first, then increased gradually, and returned to the level before fire and maintained stability after 360 days. After fire with moderate and high intensities, the greater the time span was, the more significant the difference of TK was, while the differences of TN, TP were only significant after high intensity fire. Fire intensities and time nodes had certain effects on the studied soil properties, among which high intensity fire showed the biggest effects on soil properties. Fire disturbance caused soil fertility decline in the short time and affected the soil nutrient status of forest land. However, with the time went on, the properties of soil physiochemical gradually recovered to the pre-fire level after two years.