Soil Organic Carbon And Nitrogen And Humus Components Of Different Forest Models In Zhanggutai Region

Zhanggutai artificial sand-fixing forest land is an important base for forestry in our province.Organic carbon in forest soil is an important part of the global carbon cycle.In order to achieve the sustainable development of the plantation ecosystem in the region,explore the changes in the soil nutrient environment after operating forestry,study the distribution pattern of soil organic carbon and nitrogen under different models of artificial sand-fixation.It plays an important role in guiding the evaluation of local forest management work and the ecological services of forest lands.This article takes the soil under the three afforestation models?different forest age,different forest types and different density?of Zhanggutai sandy land in Liaoning Province as the research object.Making comparison and analysis of distribution characteristics of soil organic carbon,total nitrogen and humus in 0⁴0cm soil layer through field survey sampling and indoor analysis.The results show:?1?With the increase of forest age of Pinus sylvestris var.mongolica,the soil organic carbon and nitrogen content increased significantly?P<0.05?.The growth rate was slow in the form 7 to 16 years,the growth rate increased from 16 to 34 years,and it increased after 34 years.The speed decreased again,The soil organic carbon content of Pinus sylvestris var.mongolica reaches the highest in 55 years.In different forest types,soil organic carbon content was highest in pure forest of Pinus sylvestris(18.87 g·kg^-1).This was followed by Maackia amurensis and Pinus sylvestris var.Mongolica(17.91 g·kg^-1)and Elm and Pinus sylvestris var.mongolica(17.54 g·kg^-1).The soil total nitrogen content was higher in pure forest of Pinus sylvestris var.mongolica(2.28 g·kg^-1),in Maackia amurensis and Pinus sylvestris var.mongolica(2.27 g·kg^-1)and in Elm and Pinus sylvestris var.mongolica(2.03 g·kg^-1)than in other forest types.The soil organic carbon and nitrogen contents of pure forest of Pinus sylvestris var.mongolica in various soil layers are relatively stable.The content of organic carbon in the soil surface increased significantly after mixing Maackia amurensis,Elms and Pinus sylvestris var.mongolica.The soil organic carbon content in the density group first increased with the increase in planting density of Pinus sylvestris var.mongolica,and then decreased again.The PS-1,PS-2,and PS-3(800¹200 plant·hm^-2)patterns contributed more to the accumulation of organic carbon and nitrogen in the soil of Pinus sylvestris var.mongolica.However,the difference in density had little effect on the content of organic carbon and nitrogen in the deep soil.?2?The soil organic carbon and nitrogen reserves increased with the growth of forest age in different ages of Pinus sylvestris var.mongolica forests,of which the increase range was the largest from 16 to 34 years and slowed down after 55 years.The soil organic carbon and nitrogen reserves of different forest types of Maackia amurensis and Pinus sylvestris var.Mongolica(20.0 t·hm^-2,2.59 t·hm^-2)were higher than that of pure Pinus sylvestris var.mongolica(19.92 t·hm^-2,2.47 t·hm^-2),the accumulation of soil organic carbon and nitrogen in Maackia amurensis and Pinus sylvestris var.Mongolica,Elm,Pinus sylvestris var.mongolica and other coniferous broad-leaved mixed forests is relatively large.The stability of soil organic carbon and nitrogen storage in the soil layers of Pinus sylvestris var.mongolica is better than that of other forest types.In different density forests,the soil organic carbon content in all soil layers increased first and then decreased with the increase in the density of Pinus sylvestris var.mongolica forests.The highest soil organic carbon and nitrogen reserves under different densities were PS-1,PS-2,and PS-3,the planting density of Pinus sylvestris var.Mongolica should be reasonable at 800¹200 plant·hm^-2.But each density has little effect on soil organic carbon and nitrogen reserves in the deep.?3?The content of humic acid in different forest ages increased with the increase of forest age.The growth rate was the fastest among the 16 to 34 years,and the amplitude was the highest.In the 55 years,the soil humic acid carbon content was the highest,but the growth rate decreased.The soil humic acid carbon content varies according to different forest types.The maximum PQ and C_HA/C_FA values of soil above 10cm are 34 a and 55 a mode.The maximum value of soil below 10cm is 55 a mode.The improvement of soil humus components by Spruce and Pinus sylvestris var.mongolica,Elm and Pinus sylvestris var.mongolica,and Pinus sylvestris var.Mongolica is better than other forest type.The degree of humification and the degree of polymerization of humus in the shallow soil are the highest in Pinus sylvestris var.mongolica.The degree of humification and the degree of polymerization of humus in pure soil of Pinus sylvestris var.mongolica were below 20cm layer.The humic acid carbon content in different densities of forests was significantly different.The content of PS-2 and PS-3 in humid acid carbon content is the highest in 0⁵cm soil layer,and PQ and C_HA/C_FA are the largest PS-2mode.In other soil layers,the difference of density had little effect on soil humic acid carbon content and humus component quality.?4?The soil organic carbon content under different forest ages,forest types,and densities showed significant positive correlations with humic acid carbon,humic acid carbon,and fulvic acid carbon in different degrees.