Study On The Characteristics Of Soil Bioavailable Phosphorus Of Rock Desertification Area In The Karst Graben Area

Karst graben basin area is ecological security shelter and contiguous poverty zone with paying rare attention to science and technology in comprehensive rocky desertification treatment of national engineering.The fragile ecological environment in the karst area and the unreasonable development and utilization of human beings have caused the problem of rocky desertification,which is particularly serious in the Yunnan graben basin,which restricts the development of the local economy and society and threatens the safety of the ecological environment.Phosphorus is one of nutrient elements necessary for the growth and development of crops,and its content and effectiveness will directly affect the growth and development of vegetation.The use of scientific phosphorus classification methods is the key to studying the characteristics and effectiveness of soil phosphorus components.Fire is widely used as a way to improve the quality of soil.Combustion applies heat to the soil and leaves ash,which improves the properties of the soil.In this study,fire burn sites of different years were selected as the research object,and an improved grading determination method based on bioavailable phosphorus forms was used to study the characteristics of the phosphorus component in the soil during the fire and recovery period after fire and environmental factors.The impact on the phosphorus component mainly obtained the following conclusions;(1)The effect of burning increases the soil p H,the content of elements K,Ca,Fe and Cu increases,the content of elements Na,Mg,Mn,P,Al and Zndecreases,the content of organic carbon and total nitrogen decreases,the activity of acid phosphatase decreases,and the activity of alkaline phosphatase increases..In the post-fire recovery stage,the soil p H in the burned area gradually decreased,tending to the soil p H of the unburned original forest.The organic carbon and total nitrogen content gradually increased,even exceeded the unburned original forest,and then began to decline.The element Ca content increased first In the downward trend,the content of element Al showed a gradual decrease trend,the soil acid phosphatase activity gradually increased,and there was no obvious change in alkaline phosphatase activity.(2)The burning effect increased the contents of the four phosphorus forms in the soil,and the increasing range was: HCl-P>Citrate-P>Enzyme-P>Ca Cl2-P.In the post-fire recovery phase,with the increase of the fire recovery period,the dominant phosphorus components are: Enzyme-P(2019),Ca Cl2-P(2017),Citrate-P(2015),Enzyme-P(2013),Enzyme-P(2000).(3)The available phosphorus in the burned soil Olsen-P was only significantly positively correlated with Citrate-P,and more significantly positively correlated with Ca Cl2-P,but not significantly related to Enzyme-P and HCl-P.Phosphorus may mainly come from inorganic phosphorus activated by soil organic acids and organic phosphorus hydrolyzed by enzymes.The availability of phosphorus in the soil gradually increases with the increase of recovery time,reaches its maximum at the recovery time of 4 years,and then gradually decreases.(4)Redundancy analysis shows that total P,total Ca,TN,ALP,and SOC of the soil are the significant factors that drive the succession of bioavailable phosphorus components in the soil in the burned area.