| Phosphorus is an indispensable nutrient element in the growth and development of plants.The phosphorus in the soil is fixed by Fe3+、Al3+,the content of available P in the Southern soil is low.The insufficient available P is an important factor limiting the yield of the plantation.As one of the important fast-growing timber tree species,Chinese fir occupies a very important position in the forestry production in China.But soil nutrient utilization rate decreased,especially the available phosphorus content after continuous planting of Chinese fir.On the other hand,about 35%of the remainder after fir loggingas such as leaves and small tree trunks is usually burned,a large number of plant resources are not fully utilized and wasted,and can cause soil erosion and air pollution.Therefore,it is imminent to improve the availability of phosphorus and the utilization of remainder in the forest,especially in Chinese fir forest.Biochar is a granular charcoal formed by pyrocarbonization of crop stalks,sawdust,animal feces,sludge and other materials.Its raw material is widely distributed,which provides a way for recycling of agricultural and forestry wastes.There are many researches on the improvement of agricultural soil by biochar.However,the systematic research on the mechanism of biochar affecting the phosphorus in forestry soil has rarely been reported,which greatly restricts its application in production.Effective phosphorus deficiency in soil is an important reason for the decline of continuous productivity of Chinese Fir Plantation.If we can prove the mechanism of biochar affecting the availability of phosphorus in soil,the regulation of soil phosphorus availability by biochar can improve the utilization of phosphorus in Chinese fir plantation soil,which is very meaningful for the sustainable management of Cunninghamia lanceolata Plantation and environmental protection.In view of this,leaves and stem of fir cutting processing residue as raw materials were made from biochar in this paper.The mechanism of Chinese fir forest soil phosphorus regulation by biochar was studied from the effect on soil phosphorus adsorption and desorption,soil phosphorus transformation,soil enzyme activity,bacterial diversity and availability of phosphorus and other aspects.The main conclusions are as follows:1.Langmuir equation can fit the adsorption process of phosphorus in red soil after addition of biochar well.The maximum phosphorus uptake of soil treated with BL600 and BL300 was 213mg/kg and 92mg/kg higher than that of control respectively.The maximum phosphorus uptake of soil treated with BW600 and BW300 was 76mg/kg and 49mg/kg higher than that of control respectively.The ability of improving soil phosphorus adsorption by leaves carbon is higher than trunk carbon.Biochar prepared at high temperature increased to a greater extent than biochar prepared at low temperature.Middle and low volume(2%,4%)is promoted,high addition(8%)is inhibited.On the other hand,biochar addition generally reduces desorption rate of phosphorus,and trunk carbon decreased to a greater extent than leaves carbon.Biochar addition is more sensitive in high phosphorus concentration,phosphorus desorption capacity is higher at high phosphorus concentration,soil leaching became easy.2.Biochar increased soil phosphorus utilization rate by changing the content of soil Al-P、O-Al-P、Ca2-P、Ca10-P and its own phosphorus supply.On the one hand,the content of Al-P、O-Al-P and Ca10-P in soil is reduced by the addition of biochar.On the other hand,the Ca2-P content in the soil is increased.Leaves carbon decreased to a greater extent than the trunk carbon carbon,Biochar prepared at high temperature decreased to a greater extent than biochar prepared at low temperature.Content of soil Ca2-P by leaves carbon was significantly higher than that of trunk carbon treatment.The higher the amount of biochar application,the higher the content of soil Ca2-P,the content of Ca2-P in the soil treated by high temperature biochar was higher than that of the low temperature biochar,but the content of Fe-P and O-Fe-P was changed little.3.The ability of increasing the content of available phosphorus by biochar in the soil of Chinese fir forest is BL600>BL300>BW300>BW600.The ability of increasing the content of total phosphorus in soil by biochar is BL600>BL300>BW300～BW600.Leaves carbon significantly increased the contents of available phosphorus and total phosphorus in the soil of Chinese fir leaves,especially in 3%BL600 increased in the highest.The effect of trunk carbon treatment on soil phosphorus content is little or even reducing the content of available phosphorus in soil.4.Biochar treatment changed the diversity of the original bacterial community structure and the abundance of phosphate solubilizing bacteria in soil.Trunk carbon treatment increased the number of soil bacteria,but inhibited the growth of some original bacteria,and reduced the diversity and evenness of soil microorganisms.Leaves carbon treatment increased the types of soil bacteria,improve the diversity and evenness of soil bacteria.However,the types of the dominant species of bacteria in the soil were changed,and the abundance of Chloroflexi and Acidothermus in the soil was reduced,and the abundances of Proteobacteria and Burkholderia-Paraburkholderia were increased.5.Biochar treatment decreased the activity of soil acid phosphatase,which was related to the significant increase of soil pH value.Trunk carbon treatment improves soil α-glucosidase activity but enzyme activity reducing with long-term culture.Leaves carbon treatment improves soilβ-glucosidase activity and enzyme activity increasing with long-term culture.By using the principal component analysis leaves carbon treatment can significantly improve the soil enzyme activity and phosphorus content in BL600 3%added is the best promotion.Through correlation analysis,it is concluded that soil total enzyme activity can be better responded to the results of principal component analysis.Soil urease and beta glucosidase have the greatest influence on soil phosphorus content,which can provide a reference for the availability of soil phosphorus.In conclusion,The effect of leaves carbon on improving the availability of phosphorus in the soil of Chinese fir forest is reflected as follows:The rich phosphorus content of leaves carbon provides phosphorus nutrition directly to the soil;The addition of the pH value of soil by leaves carbon;the content of Al-P、O-Al-P and Ca10-P in soil is reduced by the addition of leaves carbon,the Ca2-P content in the soil is increased;Leaves carbon addition enriches the diversity of soil bacterial community,improve the activity and quantity of soil phosphate-solubilizing bacteria;Leaves carbon addition promoted the activity of urease、beta glucosidase and so on,which indirectly enhanced the availability of phosphorus in soil.The effect of trunk carbon on decreasing the availability of phosphorus in the soil of Chinese fir forest is reflected as follows:The content of P,Ca,Fe,Al and other elements in the trunk carbon was lower,and the direct release of soil phosphorus was smaller;The effect of trunk carbon on soil pH value is weak;The influence of trunk carbon on phosphorus transformation in soil was not obvious;Trunk carbon decreased the diversity of soil bacterial communities,and inhibited the activity and quantity of soil phosphate-solubilizing bacteria. |
