| Purple soil hilly area is a typical subtropical monsoon climate ecological fragile area.Due to the influence of natural and man-made factors,bare slopes that difficult to recover naturally were often formed.In order to realize the functions of afforestation and beautification and ecological integration,slope protection lawn was often built on bare slopes for vegetation restoration and reconstruction.However,the spatial distribution of solar radiation and precipitation was seldom considered,which changes the distribution of water and nutrients in slope soil,resulting in heterogeneity of water,fertilizer,air,heat,light and other habitat factors on different slope slopes,which affects the growth of turfgrasses and the stability and ecological function of the communities.In the study,the cold-season mixed-sown lawn which sown by Festuca arundinacea,Lolium perenne and Poa pratensis on three slope directions(semi-shading slope EN 40°,sunny slope WS33°,shady slope WN 29 °)of same location in purple soil hilly area was used as the research object.After 1-5 years of construction,continuously measured the community characteristic parameters such as species density,dominant plant species and height,community density and base coverage of lawn community,and determined the dominance parameters such as relative frequency,relative coverage and relative density of three lawn grasses.At the same time,it also measured the growth parameters such as plant individual and population biomass,and the quality parameters such as color,coverage and uniformity,meanwhile measured soil particle size composition and soil p Hysical and chemical properties.The purpose of all the measurements was to analyze the succession and change rule of slope-plant-vegetation-soil-function relationship,and to study the effects of slope direction on community characteristics,turfgrasses important value and turf quality and slope soil.Then explore the reasons why the slope direction affects the community characteristics and the structure,function and service life of lawn,in order to screen out the planting and maintenance technologies suitable for different slope directions.It provided a basis and reference for bare slope ecological vegetation restoration,increasing slope landscape benefits,preventing lawn degradation and plant community function evaluation.To contributed the construction and improvement of the city’s overall environment and improved the city’s forest ecosystems integrated with cities,forests and water.The main results are as follows.1)Slope direction significantly affected the characteristic parameters of lawn community(P < 0.05).The community density of semi-shady slope was higher than that of sunny and shady in 2-5 years,and the base coverage of shady slope was significantly higher than semi-shady and sunny in 2-4 years,but the species density of sunny slope was higher than semi-shady and shady in 1-5 years.With the increase of years,the species density and dominant species height on sunny slope were higher than semi shady and shady,and the community density and base coverage were lower and lower than semi-shady and shady slope.The influence of slope direction was dominant species height ＞ species density ＞ community density ＞ base coverage.Slope direction and years affected community composition and succession potential.2)Slope direction significantly affected the communities proportion,relative density and important value of three turfgrass(P < 0.05).The proportion of three turfgrass decreased year by year,the relative density and important value decreased fastest in 2-3 years,and the degradation rate of sunny slope was higher than semi-shady and shady.The effect of slope direction on relative value was relative density ＞ relative frequency ＞ relative coverage,and on grass species was L.perenne ＞ F.arundinacea ＞ P.pratensis.The important value of the turfgrasses on shady slope in 1-2 years was greater than that on semi-shady and sunny,and that on sunny slope in 3-5 years was greater than semi-shady and shady(P < 0.05).3)Slope direction significantly affected the growth and biomass of turfgrass(P <0.05).The effects of slope direction on absolute and relative biomass were P.pratensis ＞ L.perenne ＞ F.arundinacea.The absolute biomass of F.arundinacea on sunny slope was greater than semi-shady and shady,and the relative biomass of L.perenne and P.pratensis on shady slope was greater than semi-shady slope and sunny(P < 0.05).The biomass per plant increased from 2 to 3 years and decreased from 4 to 5 years(P < 0.05).The sunny slope was conducive to the growth of F.arundinacea,while the shady slope was conducive to the early growth of L.perenne and P.pratensis.The effect of slope direction on root/shoot ratio was F.arundinacea＞L.perenne ＞ P.pratensis,and the root/shoot ratio of 3 turfgrasses on sunny slope was larger than semi-shady and shady.4)The slope direction significantly affected the degradation rate and degradation performance of turfgrasses important value and biomass.The slope direction had a significant effect on relative density,relative frequency and relative coverage degradation rate.The degradation rate of important value was L.perenne ＞ total value ＞ F.arundinacea ＞ P.pratensis,and the degradation rate of relative biomass was P.pratensis ＞ L.perenne ＞ total value ＞ F.arundinacea.As L.perenne and P.pratensis had 74.81 % and 86.13 % degradation rate in the 2nd year on sunny slope,but F.arundinacea had 70.16 % degradation rate on shady slope in 4th year.The slope direction and service year together make the slope lawn seriously degraded in 2-3years.The density,texture,color and uniformity of quality indexes decreased continuously.Although weed invasion increased the coverage and intensity to a certain extent,the overall quality excellence decreased continuously,and finally changed from mild degradation to severe degradation.5)Slope direction had significant effect on soil p Hysical and chemical properties(P < 0.05).The effect on particle size composition was large sand ＞ fine silt ＞ very fine sand ＞ Coarse Sand ＞ clay ＞ coarse silt ＞ fine sand.The clay,fine silt,coarse silt and large sand on the sunny slope are lower than those on the shady and semi-shady slope.The clay,fine silt,coarse silt,very fine sand and fine sand of three slopes soil in the fifth year were significantly greater than those in the first year.The organic matter,effective N,effective P and effective K of the shady slopes were significantly higher than sunny slopes,but the effective P and effective K of semi-shady slopes were not different from those of shady slopes.The slope protection lawn significantly increased the proportion of clay and silt in the soil in the three slope directions,increased the soil thickness of the slope,reduced the soil bulk density,and increased the contents of available N,available P and available K of soil organic matter.In summary,the slope direction significantly affects the characteristics of lawn community,the important value of established species,the degradation speed and quality excellence of lawn.Controlling weed invasion was an effective way to prevent the degradation of the lawn.The lawn establishment significantly improves the soil texture and water and fertilizer supply capacity of slope soil.Therefore,it is the basic requirement of ecological management and construction of slope protection vegetation to select grass species,establish planting and maintenance techniques,strengthen weed management and maintain pioneer vegetation functions. |
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