Study On The Spatial-temporal Variablity Of Phosphorus And Soil Adsorption In Forest Belt Surrounding Taihu Lake

As one type of ecotone between water and land, the near-shore ecological forest belt playsan irreplaceable role in non-point source pollution prevention and water eutrophicationcontrolling. This thesis chooses woods of Populus liaoningensis, Magnolia grandiflora,Cinnamomum camphora and Lagerstroemia indica as the study object, by the means of wildcollection and laboratory experiment, studying the seasonal dynamics of soil and plantphosphorus and the characteristics of soil phosphorus adsorption, finding out the migration andtransformation regularity of phosphorus in the soil-plant system as well as the most active formof phosphorus in adsorption process, which provides scientific basis for management andmaintenance of the forest belt surrounding Taihu lake as well as prevention of watereutrophication. The main research results are as follows:(1) Different forest belt absorbs different amount of phosphorus, inwhich process there exists obvious seasonal changes. For deciduous trees such as Populusliaoningensis and Lagerstroemia indica, phosphorus content peak occurs in summer, whereas forevergreen trees such as Magnolia grandiflora and Cinnamomum camphora, the peak occurs inwinter.(2) The differences of phosphorus amount between the four forest belts and abandonedfarmland come to a significant level (p<0.05). Seasons and the types of forest belts influentphosphorus amount in soil a lot, with the regularity that type ranged as Magnolia grandiflora＞Cinnamomum camphora＞Lagerstroemia indica＞Populus liaoningensis, and season ranged aswinter＞autumn＞spring＞summer. In various forms of inorganic phosphorus, NaOH-Pi＞NaHCO₃-Pi＞HCL-Pi,while in organic phosphorus, NaOH-Po＞NaHCO₃-Po＞HCL-Po.Phosphorus content extracted from NaOH solution is the highest.There are dynamic variations ofphosphorus in soil-plant system, namely the increased phosphorus content inside plant equalswith the decreased phosphorus content in soil. This is to say, pollutant phosphorus is removedfrom soil.(3) There is significant difference of phosphorus static adsorption capacity between theforest belts and abandoned farmland (p<0.05), with adsorption capacity ranged as Magnoliagrandiflora, Cinnamomum camphora, Lagerstroemia indica, Populus liaoningensis andabandoned farmland, and season ranged as winter＞autumn＞spring＞summer, which indicatesthat seasons and types of forest belts affect soil absorption of phosphorus a lot. Isothermalabsorption experiment suggests that phosphorus-adsorption capability of Magnolia grandiflorand Cinnamomum camphora is higher, with greater retention and buffering capacity towardsphosphorus. Soil absorption capacity increases as the temperature increases, along with larger phosphorus amount in soil. Meanwhile, pH value tends to change from acidity or alkaline toneutral before or after soil adsorbing phosphorus, with the least adsorption in neutral condition.After the soil-adsorbing-phosphorus experiment, all forms of phosphorus have varying degrees ofincreasing or decreasing, with NaOH-Pithe most,H2O-P the least, and NaOH-P the most activephosphorus form in the process of soil absorption.(4) Relevant analysis suggests that there is apparent relationship between pH, organic matter,total nitrogen and phosphorus content in soil. The relation between different forms of phosphorusand total phosphorus comes to prominent level, the same with different forms of phosphorus andavailable phosphorus, except for HCL-Piand NaOH-Po.There is significant positive correlationbetween soil adsorption capacity and total phosphorus, different forms of phosphorus, organicmatter and total nitrogen, whereas extremely significant negative correlation with pH, and noobvious relation with available phosphorus, water content, bulk density and potassium.