| Seabuckthorn is a kind of shrub species with strong drought and cold tolerance.Because of its complex root system,sprouting,self-renewal and cloning ability,it has strong environmental suitability.It can not only grow in the more fertile forest zone of the Loess Plateau,but also grow stably in the grassland zone with steep slope and poor soil.As a good shrub species of arti ficial forest,Hippophae rhamnoides L,It has been widely used in the ecological restoration of the semi-arid area of the Loess Plateau.In order to better guide the wide planting and application of Hippophae rhamnoides in arid and semi-arid areas,the growth status of Hippophae rhamnoides and trees in 36 sample plots of Hippophae rhamnoides pure forest,mixed forest and Hippophae rhamnoides hopeiros mixed forest in Wuqi County,Yan’an City,Shaanxi Province were investigated,The soil samples under the forest were analyzed in laboratory.Based on the principle of Entropy TOPSIS comprehensive evaluation,the optimal model of seabuckthorn transformation and mixing was explored from three aspects: the overall growth status of forest,the benefits of soil improvement under forest and further comprehensive evaluation.The main results are as follows:(1)Considering the growth of basal diameter,plant height and crown width,the growth of Hippophae rhamnoides on shady slope was better than that on sunny slope.The average basal diameter,plant height and density of Hippophae rhamnoides had no significant correlation with each factor under the afforestation mode of Hippophae rhamnoides + Prunus armeniaca,but the preservation rate of Hippophae rhamnoides had a significant negative correlation with the density of Prunus armeniaca.Under the afforestation mode of Hippophae rhamnoides + Robinia pseudoacacia,the conservation rate of Hippophae rhamnoides was significantly positively correlated with the diameter at breast height of Robinia pseudoacacia,and the crown width of Hippophae rhamnoides was significantly negatively correlated with the conservation rate of Hippophae rhamnoides.Under the afforestation mode of Hippophae rhamnoides and Populus hopeiensis,the conservation rate of Hippophae rhamnoides was negatively correlated with the height of Populus hopeiensis.(2)Soil p H value showed that the soil of 12 sample plots with 2 slope directions and 6 mixed patterns were alkaline.The p H value of pure seabuckthorn forest on sunny slope was the highest,and that of pure seabuckthorn forest on shady slope became the lowest.The percentage and that of mixed Seabuckthorn and apricot forest on shady slope was the most.The percentage of soil total nitrogen varied from 0.3% to 0.8%.The total nitrogen content of pure seabuckthorn forest on sunny slope was much higher than that of other mixed models,while the total nitrogen content of most mixed models on shady slope was less different.The soil hydrolytic nitrogen varied from 24 mg / kg to 72 mg / kg.The nitrogen content supply capacity was the strongest in the mixed Seabuckthorn and Populus hopeiensis forest on the shady slope.The total K content of soil varied from 16 g / kg to 20 g / kg.The soil total phosphorus varied from 0.3 g / kg to 0.8 g / kg.The phosphorus supply ability of seabuckthorn + Pinus tabulaeformis mixed forest on sunny slope was the strongest,and that of seabuckthorn and Populus hopeiensis mixed forest on shady slope was the strongest.(3)In the pure seabuckthorn forest,the most important soil nutrient factor for basal diameter is total phosphorus,whether it is shady slope or sunny slope;For plant height,the most important soil nutrient factor on sunny slope is available phosphorus,the most important soil nutrient factor on sunny slope was total carbon,regardless of base diameter,plant height or density;The most important soil nutrient factor of shady slope is total potassium.In the mixed forest of Hippophae rhamnoides and Prunus armeniaca,the most important soil nutrient factor for basal diameter was total phosphorus on sunny slope and hydrolytic nitrogen on shady slope;For plant height,the most important soil nutrient factor on sunny slope was total phosphorus;The most important soil nutrient factor of shady slope is available phosphorus.For density,the most important soil nutrient factor on sunny slope is total nitrogen,and the most important soil nutrient factor on shady slope is available phosphorus.In the mixed forest of Hippophae rhamnoides and Robinia pseudoacacia,the most important soil nutrient factor for basal diameter was total phosphorus on sunny slope and hydrolytic nitrogen on shady slope;For plant height,the most important soil nutrient factor on sunny slope was total phosphorus,and the most important soil nutrient factor on shady slope was total potassium;For plant height,the most important soil nutrient factor in shady slope was available phosphorus;For density,hydrolytic nitrogen is the most important soil nutrient factor on sunny slope,and available phosphorus is the most important soil nutrient factor on shady slope.For plant height,the most important soil nutrient factor on sunny slope is total potassium,and the most important soil nutrient factor on shady slope is hydrolytic nitrogen.(4)The order of the overall growth status of the Seabuckthorn mixed forest was Seabuckthorn +Populus hopeiensis mixed forest(sunny slope)> Seabuckthorn + Populus hopeiensis mixed forest(shady slope)> Seabuckthorn + Robinia pseudoacacia mixed forest(sunny slope)>Seabuckthorn +Platycladus orientalis mixed forest(sunny slope)> Seabuckthorn + Pinus tabulaeformis mixed forest(sunny slope).Hippophae rhamnoides and Robinia pseudoacacia(sunny slope)> mixed forest of Hippophae rhamnoides and Platycladus orientalis(sunny slope)> pure forest of Hippophae rhamnoides(shady slope)> mixed forest of Hippophae rhamnoides and Pinus tabulaeformis(shady slope).The results showed that Seabuckthorn + Populus hopeiensis mixed forest(shady slope)>Seabuckthorn + Pinus tabulaeformis mixed forest(sunny slope)> Seabucktho rn + Platycladus orientalis mixed forest(shady slope)> Seabuckthorn + apricot mixed forest(shady slope)>Seabuckthorn pure forest(sunny slope)> Seabuckthorn + apricot mixed forest(sunny slope)>Seabuckthorn + Platycladus orientalis mixed forest(sunny slope)> Hippophae rhamnoides + Robinia pseudoacacia mixed forest(sunny slope). |
