| Soil aggregate is the basic unit of soil structure.The forms,distribution and its relevant influence factors of phosphorus in soil aggregate reflect the geochemical characteristics and cycling mechanism of phosphorus.The geochemical forms of phosphorus in forest soil aggregates is an important research focus in the field of nutrition maintenance mechanism and its sustainable utilization of forest ecosystem.In this work,soil was fractionated by a combination method of physical,chemical,and density fractionation techniques,and sequential extraction procedure was used for the fractionation of phosphorus.In this paper,the forms characteristics and influencing factors of inorganic phosphorus in soil and its aggregates under different interference conditions were systematically analysed,the content level and spatial distribution of inorganic phosphorus in the study area were preliminarily determined,and the influence mechanisms of different interference modes on forms distribution of soil inorganic phosphorus were discussed.This work was significant to the further study on biogeochemical cycle mechanism of phosphorus in the soil-forest ecosystem and the sustainable development and utilization of cold temperate forest ecosystem.The main results were as follows:1.With the increase of thinning intensity,the contents of soil TOC,TP,Act-P and large aggregates decreased significantly,TP and Act-P in all aggregate fractions of soil also showed the similar change trend.The RDA and correlation analysis showed that TOC and p H were the key factors affecting the distribution of soil phosphorus forms.2.The contents of TP,Act-P,Sta-P and TOC in soil increased with the increasing of after-fire restoration years,and Fe-P and Oc-P showed the similar change trends.The content of TP also increased with the increasing of restoration years in c POM fraction.The analysis shows that TOC was a key environmental factor affecting the dynamics of soil phosphorus forms in the process of after-fire restoration.3.The content of soil TOC in the study area was high in the central and western regions,gradually decreasing to the east,and significantly lower in the northwest,northeast and southeast regions than that in other regions.The spatial distribution of TP content in soil and all aggregate fractions were almost same to each other,which was higher in the eastern and midwestern regions and lower in the south..4.The distribution trend of TP content in all aggregate fractions was roughly as follows: ?Clay > d Clay > LF > c POM > d Silt > ?Silt > i POM,in which c POM and d Silt fractions contribute greatly to soil TP.The order of phosphorus forms content in study area was as follows: ACa-P > Fe-P >Oc-P > Or-P > De-P > Al-P > Ex-P.5.C/P of soil and each protection mechanism fraction in study area were all less than 200,C/P of different protection mechanism fractions differed significantly,and the order was as follows: non-protection mechanism > biochemical protection mechanism > physical protection mechanism > physical and biochemical coupling protection mechanism,which indicated that phosphorus release potential during organic matter decomposition was highest in physical and biochemical coupling protection mechanism.6.The protective effect of soil aggregate protection mechanism on TOC was significantly better than that on TP.The protective ability of each protection mechanism was as follows: physical and biochemical coupling protection mechanism > biochemical protection mechanism >physical protection mechanism > non-protection mechanism. |
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