| Pinus sylvestris plantation is the main tree species for windbreak and sand fixation in the Hunshandake sandy land.The stability of the plantation ecosystem is an important prerequisite for determining its sustainable ecological function.This paper takes the Pinus sylvestris plantation in the southeastern edge of the Hunshandake Sandy Land as the research object.Based on the division of site conditions,this paper investigates the growth status of Pinus sylvestris plantation,the micro environment in the forest,the physical and chemical properties of soil,the forest under various site conditions.Under the herb species diversity,the grey relational analysis method is used to comprehensively evaluate the vegetation stability of each site,identify its limiting factors,and provide a theoretical basis for vegetation management,protection and ecological construction in the Hunshandake Sandy Land.The main research conclusions are as follows:(1)According to the principle and basis of site conditions,the southeastern edge of Hunshandake Sandy Land is divided into the following 7 types of sites by selecting slope and aspect as the dominant factors:flat slope,sunny gentle slope,shady gentle slope,sunny slope,shady slope,sunny steep slope and shady steep slope.(2)The growth of Pinus sylvestris plantation on the sunny slope was the best under each site condition,and the average tree height,DBH and crown width were 3.10m,55.32mm and 1.75m,respectively;0.98m,23.06mm,0.55m.The tree height,DBH and crown width of each site are mainly distributed in 1.5m～3.5m,20mm～50mm,and0.9m～1.8m.With the increase of slope,the height class,diameter class and crown width class of Pinus sylvestris plantation showed a normal distribution.(3)There was no significant difference in temperature,humidity and light intensity in the pine plantation at a height of 0.5m from the ground under different site conditions.Among them,the temperature difference is≤8.59℃,the humidity difference is≤27%,and the light intensity difference is≤6.5576×10~4LUX.The maximum value of temperature(38.0℃),light intensity(15.873×10~4LUX)and minimum value of humidity(29%)all appeared on the flat slope.(4)The minimum mean values of soil saturated water holding capacity,capillary water holding capacity and field water holding capacity of Pinus sylvestris plantation under different site conditions all appeared on the steep slopes in the sunny direction,which were 30.12%,26.41%and 21.66%,respectively.The average value of the shady sleep slope is the largest,which is 11.75%,8.11%and 7.92%higher than that of the sunny sleep slope,and the soil water holding capacity of the shady sleep slope is the best.Considering all soil properties,the soil nutrients under the Pinus sylvestris plantation on flat slopes and sunny slopes are the best.(5)A total of 18 species of plants appear in the herb layer under the Pinus sylvestris plantation,belonging to 8 families and 15 genera,more than 60%of which are perennial herbs.The important value of Spodiopogon sibiricus was 32.51,and it was the dominant species in this site,and Anemarrhena asphodeloides was the dominant species.The important values of each herb on different sites were sunny slope>shady slope,and the vegetation diversity index showed a low-high-low trend with the increase of slope as a whole.(6)The stability of Pinus sylvestris plantation under different site conditions is as follows:sunny slope>flat slope>shady gentle slope>sunny steep slope>shady steep slope>shady slope>sunny gentle slope.Soil alkaline hydrolyzable nitrogen,available potassium,total nitrogen,total phosphorus,total potassium,and understory herb species richness,uniformity,and dominance are the main limiting factors that affect the stability of pine sylvestris plantations in each site condition. |
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