Analysis Soil Phosphorus Availability And Its Influence Factors After Vegetation Restoration From Seriously Burning In Greater Khingan Mountain Areas,China

In order to understand phosphorus availability and its influence factors in soil after restoration from the seriously burning,we chose soil samples from artificial restoration(Pinus sylvestris var.mongolica plantation,Larix gmelinii plantation),artificial accelerated natural restoration(secondary forest)and natural restoration(natural secondary forest)stand in Greater Khingan Mountain area.Using modified Hedley phosphorus fractionation and Sui et al.phosphorus adsorption and desorption methods to measure the contents of different phosphorus forms and phosphorus adsorption and desorption measurements in rhizosphere soil and bulk soil(0-10,10-20 cm)and high-throughput sequencing method and disodium p-Nitrophenyl phosphate tetrahydrate to measure the abundances of bacteria and phosphatase activity,respectively.The contents of total phosphorus,available phosphorus,organ ophosphorus,NaHCO3-Pi,NaHCO3-Po and NaOH-Po decreased with the deepening of the soil after restoration from seriously burning,while the contents of inorganic phosphorus,H2O-Pi and NaOH-Pi in the soil except the Larix gmelinii plantation showed a phenomenon of surface accumulation.The ratios of contents of available phosphorus,organic phosphorus,labile phosphorus forms(H2O-Pi,NaHCO3-Pi and NaHCO3-Po)and PAC in all forest stands in rhizosphere to those in bulk soil(R/S)were great than 1.The contents of total phosphorus,labile phosphorus forms,inorganic phosphorus,organic phosphorus and labile phosphorus fractionations in the rhizosphere and 0?10,10?20 cm bulk soil were higher than that of secondary forest and natural secondary forest after artificial restoration of 29a,and Larix gmelinii plantation was the highest.The contents of moderately labile NaOH-P and stable HCl-P in soil was the highest in Larix gmelinii plantation.The content of residual-P in the soil was not sensitive to the restoration methods.Except for the Pinus sylvestris var.mongolica plantation,the soil pH increased with the deepening of soil layer in others.The contents of soil organic carbon and total nitrogen decreased with the deepening of soil layer.The soil pH was in order of Pinus sylvestris var.mongolica plantation>Larix gmelinii plantation>secondary forest>natural secondary forest.Soil organic carbon was the dominant factor of phosphorus forms variability.There was a negative correlation between pH and residual-p and NaOH-Po,and a strong positive correlation between soil organic carbon,total nitrogen and NaOH-Po.The soil adsorption and desorption measurements to phosphorus in all forest stands were consistent with the Langmuir isothermal adsorption curve.The soil Qm decreased with the deepening of soil layer.Soil K increased with the deepening of soil layer except natural secondary forest.The soil desorption amount to phosphorus of Larix gmelinii plantation decreased with the deepening of soil layer.Except the soil desorption amount to phosphorus of in natural secondary forest when the phosphorus concentration of adsorbent was 20 mg·L-1,the R/S value of soil to phosphorus desorption amount was all greater than 1.The soil desorption ratio to phosphorus of Larix gmelinii plantation decreased with the the deepening of soil layer,while the secondary forest and natural secondary forest were opposite.The soil to phosphorus desorption ratio in rhizosphere soil of Larix gmelinii plantation is higher than that of bulk soil.The soil MBC to phosphorus was considered by Qm and K.The soil MBC of Larix gmelinii plantation and natural secondary forest was higher,and that of Oinus sylvestris var.mongolica plantation was the lowest.The soil DPS to phosphorus in Larix gmelinii plantation was the highest,followed by that of Pinus sylvestris var.mongolica plantation.Compared with the natural secondary forest,the average value of soil desorption to phosphorus in the Pinus sylvestris var.mongolica plantation increased,while that in the Larix gmelinii plantation and secondary forest decreased,and the soil desorption ratio to phosphorus of Pinus sylvestris var.mongolica plantation was the highest.Soil DPS was the dominant factor of phosphorus fractionation variability.K,MBC were positively correlated with residual-P,while the average desorption amount was negatively correlated with residual-P.Soil Qm and DPS were positively correlated with other phosphorus forms except residual-P,while Qm was closely correlated with HCl-Po,DPS with NaHCO3-Po.In addition to Pinus sylvestris var.mongolica plantation,the soil bacteria at phylum level and abundance of phosphorus solubilizing bacteria decreased with the deepening of soil layer.In addition to Larix gmelinii plantation,the rhizosphere soil had enrichment effect on the phosphorus solubilizing bacteria community.The soil bacteria Ace index,Simpson index,Shannon index in all forest stands and Chao1 index expect Pinus sylvestris var.mongolica plantation increased with the deepening of soil layer.In addition to Pinus sylvestris var.mongolica plantation the R/S of the four alpha diversity index of soil bacteria was not less than 1.The dominant soil bacterial communities in different stands were Actinobacteria,Proteobacteria,Chloroflexi,Gemmatimonadetes,Verrucomicrobia,Planctomycetes and Bacteroidetes.The richness and evenness of soil bacterial community in Pinus sylvestris var.mongolica plantation were the highest.Compared with the natural secondary forest,the abundance of soil phosphorus solubilizing bacteria was increased in Pinus sylvestris var.mongolica plantation and Larix gmelinii plantation,while there was no significant difference between secondary forests and natural secondary forests.In addition,the activity of soil alkaline phosphatase at all forest stands and soil acid phosphatase expect Pinus sylvestris var.mongolica plantation decreased with the deepening of soil layer.And the activity of soil acid phosphatase and alkaline phosphatase in rhizosphere was higher than that in bulk soil.The activity of soil acid phosphatase and alkaline phosphatase in Larix gmelinii plantation was higher.According to RDA,the bacterial abundance at phylum level and abundance of phosphorus solubilizing bacteria was positively correlated with labile phosphorus forms,and Chaol index,ACE index and Shannon index were negatively correlated with residual-P.Soil Flavobacterium,Serratia,Acinetobacter were positively correlated with different phosphorus forms,and were the main executors of soil phosphorus transformation in the study area.The labile H2O-Pi,NaHCo3-Pi and NaHCO3-Po was positively correlated with the activity of acid phosphatase,while the moderately labile NaOH-Po and stable residual-P were closely correlated with alkaline phosphatase.At present,artificial afforestation was more conducive in improving the availability of phosphorus in soil.There was no shortage of phosphorus supply in all recovery methods,and the soil had a low risk of phosphorus pollution in water.The availability of soil phosphorus was regulated by the adsorption and desorption measurements,basic soil properties,soil microorganisms and phosphatase.