Effects Of Fire Disturbance On Dynamic Changes Of Soil Physical And Chemical Properties In Secondary Forest Of Liquidambar Formosana

Soil physical and chemical properties are the key indicators to determine soil quality.Studying the dynamic trends of soil physical and chemical properties,soil depth and recovery time can reveal the transformation law and regulation mechanism of soil fertility.Through burning plants and high temperature denaturation,forest fire can change the content of physical and chemical properties of forest soil,affect the increase and loss of organic matter,nitrogen,phosphorus and potassium in soil,change soil porosity and pH,and then affect the distribution pattern of physical and chemical properties of the whole system Vegetation and soil restoration and forest management provide scientific theoretical guidance.From 2014 to 2016,16 20 m×20 m sample plots were set up in the secondary forest of Liquidambar formosana in You County,Zhuzhou City,Hunan Province.The fire interference intensity was control(unburned),low intensity fire interference,medium intensity fire interference and high intensity fire interference.Four sample plots were set for each fire interference intensity,and three soil profiles were set along the diagonal.Four mixed soil samples(16 samples)were collected from the control plot,and soil samples at different depths(0-5 cm,6-10 cm,11-15 cm,16-20 cm)were collected from each fire disturbed plot at five time points(3 days,30 days,180 days,360 days,720 days after fire)The soil bulk density(BD),soil water repellency(SWR),soil organic matter(SOM),pH,total nitrogen(TN),total phosphorus(TP)and total potassium(TK)in different soil layers and recovery time after fire disturbance treatment were determined.Single factor analysis of variance and Fisher LSD test were used to analyze the significant differences of soil physical and chemical properties among different fire disturbances,different soil layers and recovery time under the same fire disturbance,and to explore the influence of fire disturbance intensity on soil physical and chemical properties and the dynamic change trend of different soil depth and recovery time after fire disturbance.The results showed that,The overall change trend of soil physicochemical properties after fire disturbance showed that fire disturbance intensity,soil depth and time node all have certain effects on the seven soil physicochemical properties,in which high-intensity fire disturbance has the greatest impact on soil properties,while low-intensity fire disturbance has the least impact.With the increase of fire intensity,BD,SWR,pH and TK increased,while SOM,TN and TP decreased.BD and SWR in different soil layers after fire disturbance:BD and SWR of each layer of Liquidambar formosana secondary forest increased with the increase of fire interference intensity.High intensity fire had the most significant effect on soil BD,while low intensity fire had little effect on soil BD.In the same soil layer,there was no significant difference in BD between low and medium intensity fire disturbance plots and unburned plots,while high intensity fire disturbance increased BD significantly(P<0.05);SWR of different layers of soil increased with the increase of fire disturbance intensity,but decreased with the depth of soil layer.SWR of different layers increased significantly after middle and high intensity fire disturbance.SWR of lower layer was significantly smaller than that of upper layer after the same fire disturbance.The SOM and pH of different soil layers after fire disturbance showed that the SOM and pH of Liquidambar formosana secondary forest were significantly affected by soil depth and fire disturbance.With the increase of fire intensity,soil pH increased,and the same soil layer pH was significantly affected by high-intensity fire;while SOM in all soil layers decreased with the increase of fire interference intensity,and the surface soil was significantly affected by fire interference,and the surface soil SOM decreased significantly after fire.SOM was significantly affected by soil depth after low and medium intensity fire disturbance,and the bottom soil was significantly smaller than the upper soil after high intensity fire disturbance.The change trend of TN,TP and TK in different soil layers after fire disturbance.TN is less affected by fire intensity,while TP and TK are not affected by fire.Under the disturbance of the same fire intensity,the difference of TN between the upper soil and the lower soil was significant,the difference of TP between the four soil layers was small,but the difference of TK was significant.The dynamic change characteristics of soil physical and chemical properties at different time points after fire disturbance.Soil physical and chemical properties returned to prefire level within 2 years after fire disturbance,and BD,SWR and pH were significantly affected by time node after fire disturbance,while SOM,TN and TK were significantly affected by recovery years after high-intensity fire disturbance,and TP was relatively less affected by time node.BD was most significantly affected by time node after high intensity fire,and recovered to the level before fire 360 days later.There were significant differences between different time nodes under medium intensity and high intensity fire disturbance,and recovered to the state without fire after 720 days.SOM was significantly affected by high intensity fire before 360 days,and gradually returned to the level before fire and remained stable after 360 days.The soil pH increased significantly 3 days after fire,then decreased gradually,and returned to the level before fire 720 days later.The high strength of TN joint is only affected by the time of fire.Fire intensity at each time node had no significant effect on soil TP.TK is significantly affected by time node after medium and high intensity fire disturbance.