The Effect Of The Growth Of Pinus Sylvestris Plantation On Soil Eco Stoichiometry

The growth of sand-fixation forest of Pinus sylvestris affects the stoichiometric changes of soil carbon,nitrogen and phosphorus,which however has been studied rarely.Based on the Pinus sylvestris plantation in different growth stages(young forest,middle-aged forest,mature forest and over-mature forest)in Horqin Sandy Land,the change rules of soil carbon,nitrogen and phosphorus stoichiometry with forest age in the 0-100 cm layer were investigated in this paper.Soil N:P and C:P decreased sharply with soil profile,and the vertical decline rate was faster than C:N.C:N The content changes with the depth of soil layer.Soil layer of Pinus sylvestris var.mongolica plantation has significant effect on C:N and N:P,No effect on C:P.The soil nitrogen under the forest is the limiting factor of C:P and N: P.The soil layer of Pinus sylvestris Plantation had significant effect on C:N ratio and N: P ratio,There was no effect on C:P ratio.The soil nitrogen under the forest is the limiting factor of N:P.The C:N ratio of Pinus sylvestris var.mongolica plantation increased negatively in 0-20 cm soil layer,With the increase of soil depth,it is positive growth at 20-100 cm.C:P,N:P was negative growth at 0-100 cm.The soil nitrogen content is the limiting factor of N: P,N:P and P are the limiting factors of C:N and C:P at this stage.The soil layer of 56 a Pinus sylvestris Plantation had significant effect on N:P ratio and C:P ratio,but had no effect on C:N ratio.In this stage,C:N is the main limiting factor,Soil phosphorus is the main limiting factor of C:P,Soil nitrogen is the main limiting factor of N:P.The soil C:N ratio of Pinus sylvestris var.mongolica forest increased with the increase of forest age from 13 a to 25 a in 10-100 cm soil layer.The decrease of mineralization rate leads to the decrease of 13 a to 25 a,C:P ratio is lower than 25 a to 44 a,C:P is the rate of descent.From 44 a to56a,the growth of Pinus sylvestris Plantation had a significant effect on the C:N ratio of soil,At this time,the C:N ratio of soil was significantly higher than that of other forest ages.The soil C:P ratio was 0-100 cm in the period from 13 a to 44 a,They all decrease year by year,There was no significant difference in forest age.The phosphorus content needed for the growth of,Therefore,the phosphorus content of 13a-44 a increased in 0-100 cm soil layer.At 56 a,the ratio of soil to C:P was significantly different,And the C:P ratio of 0-100 cm soil layer is significantly higher than that of other forest age soil.The N: P ratio of Pinus sylvestris Plantation Soil is far lower than the average value of soil N:P in China,In 10-100 cm soil layer,the N:P ratio decreased with the increase of forest age,The growth of Pinus sylvestris Plantation plays an important role in litter decomposition and soil nutrient return.It can be seen from 0-40 cm soil layer and 80-100 cm soillayer of all forest ages,There was no significant difference in the effect of forest age on N:P ratio of soil,But it is still higher than the original grassland.The results show that the growth of Pinus sylvestris var.mongolica can supplement soil C,N and P.When Pinus sylvestris Plantation grows to 56 a,If the soil N content is artificially increased,It can inhibit the forest decline due to the limitation of soil N and P,The growth and development rate of Pinus sylvestris Plantation was maintained.In this way,the growth time of Pinus sylvestris Plantation can be prolonged,It can also increase the sustainability of desertification control.