Effects Of Thinning And Transplant On Community Characteristics Of Artificial Robinia Pseudoacacia Forest

Tending and under-forest introduction are considered to be one of the most effective ways of forest management and protection of vegetation diversity.However,there is still a lack of systematic research on how the thinning intensity and understory introduction affect the ecological vegetation structure,soil properties and microbial diversity of artificial forests.In this regard,this study was based on botany and soil science theories,and introduced four different densities of Sabina vulgaris(0,90)through different thinning intensities(intensity,moderate,and light thinning)in the forests of Robinia pseudoacacia.After 120 and 150 strains/mu of Sabina vulgaris and Platycladus orientalis,the effects of plant diversity,soil organic carbon content,and soil microbial enzymes were studied systematically,and the relationships between plant diversity,soil characteristics,and soil microbial properties were analyzed.The main conclusions are as follows:(1)Effects of thinning intensity and under-season introduction on species diversity of artificial Robinia pseudoacacia forest: Compared with the intensity-harvesting Robinia pseudoacacia forest,the degree of canopy closure of moderately and slightly reduced Robinia pseudoacacia forests increased significantly by 97.96 % and 98.98 % respectively;Significantly decreased by 44.10 % and 54.54 %;the basal diameter decreased significantly by 42.57 % and 53.09 % respectively;no significant changes were observed in tree height.Compared with the non-introduced Robinia pseudoacacia forest,the canopy density of Robinia pseudoacacia forest did not change significantly under the different introduction methods.The introduction of Thuja orientalis,and the introduction of low,medium and high density Sabina vulgaris led to a significant decrease in DBH of 16.29%,24.69%,and 19.74% respectively.17.69%;The basal diameter decreased significantly by 16.94%,24.63%,18.06%,and 19.15%,respectively;introduction of low,medium and high density Sabina serrata led to a significant decrease in tree height of 5.47 %,9.96 % and 8.58 %,respectively.There was no significant change in height.The dominant species of shrubs and bark are found in pure Robinia pseudoacacia forest and mixed forest.The dominant herb species is Artemisia sacrospira.The density of pure Robinia pseudoacacia forest is not too large,and the density of the mixed forest of Robinia pseudoacacia and Sabina vulgaris is conducive to the growth of herbaceous vegetation.,the density of the hours is conducive to the growth of shrub vegetation.(2)Effects of thinning intensity and under-forest introduction on the soil carbon content of artificial Robinia pseudoacacia: Under the same cutting intensity of pure Robinia pseudoacacia forest and the same introduction method,the total organic carbon content in soil decreased as the depth of soil layer increased.There is a clear vertical distribution of the soil.The total variation of total organic carbon in the soil under pure thinning Robinia pseudoacacia under different thinning intensities was highest(4.20 g/kg),followed by moderate thinning(2.65 g/kg),and mildest thinning(2.26 g/kg).The average change rule of the three kinds of easily oxidized organic carbon content was the highest mean intensities(1.22 mg/g),followed by mild thinning(0.63 mg/g)and moderate thinning(0.52 mg/g).The total variation of total organic carbon content in the soil of Robinia pseudoacacia seedlings under different introduction methods was highest.The average density of S.vulgaris was the highest(4.61 g/kg).The rest were introduced low density Sabina vulgaris(4.57 g/kg),but not introduced the Robinia pseudoacacia forest.3.35 g/kg),introduction of high-density Sabina vulgaris(3.33 g/kg)and introduction of Platycladus orientalis(3.21 g/kg);the average variation rule of three kinds of easily oxidized organic carbon content;the highest average value of unintroduced Robinia pseudoacacia forest(1.09 Mg/g),followed by introduction of low-density Sabina vulgaris(0.94 mg/g),introduction of high density Sabina vulgaris(0.92 mg/g),introduction of medium density Sabina vulgaris(0.75 mg/g),and introduction of Platycladus orientalis(0.74 mg/g)Mg/g).Overall,soil total organic carbon and oxidizable organic carbon content were positively correlated with soil total nitrogen,total pHospHorus,available pHospHorus,nitrate nitrogen,and water content,and negatively correlated with ammonia nitrogen and pH.There may be a close relationship between soil total organic carbon content,easily oxidized organic carbon content and soil total nitrogen.(3)Effects of thinning intensity and under-forest introduction on soil microbial enzymes in artificial Robinia pseudoacacia under different forest conditions: Under different thinning intensities of pure Robinia pseudoacacia,for the same microbial enzyme,the order of enzyme activity is high and low.In the second place,the lowest intensity was observed under the thinning;under the same cutting intensity,the order of the activity of different microbial enzymes was both ?-1,4 glucosidase> acid pHospHatase> cellobiohydrolase> ?-1,4-NAcetaminoglucosaminidase.Under different introduction methods,the activity of the four enzymes increased to varying degrees compared to unintroduced pure Robinia pseudoacacia.Under the same introduction method,the order of the activity of different microbial enzymes was as follows: Acid PHospHatase > ?-1,4 Glucosidase > Cellobiohydrolase > ?-1,4-N-acetylglucosaminidase.The four enzyme activities were positively correlated with soil total nitrogen,total pHospHorus,available pHospHorus,nitrate nitrogen,bulk density and water content,and negatively correlated with soil ammonia nitrogen.Soil microbial enzyme activities may be closely related to soil total nitrogen,nitrate nitrogen,bulk density,and soil moisture content.(4)Study on the relationship among vegetation,soil and microbial enzymes under different thinning intensity and introduction methods: Under different thinning intensities,the relationship between different microbial enzymes and vegetation characteristic parameters varies,?-1,4-N-acetylamino Glucosidase and acid pHospHatase are closely related to tree height,?-1,4 glucosidase and cellobiohydrolase are closely related to DBH and basal diameter;the correlation between soil organic carbon content parameter and microbial enzyme activity is low Reactive oxygenated organic carbon content.Among the different introduction methods,the DBH and basal diameter are closely related to the activity of microbial enzymes in the characteristic parameters of vegetation.The content of organic carbon in the organic carbon content parameter is closely related to the activity of microbial enzymes.In the later vegetation development in the Loess Plateau region,shrub species and shrubs are recommended for shrub species,and Artemisia species is selected for herbaceous species.For pure R.pseudoacacia forests,the planting density is not too large,and the stand density is recommended to be below 75 plants/mu;In the mixed forest of Sabina vulgaris,if the herbaceous vegetation is restored,a high-density(150 plants/mu)mixed forest should be selected to restore the shrub-vegetated mixed forest with low density(90 plants/mu).