| Vegetation has a profound impact on soil erosion,soil and water conservation,and soil is the survival condition for human.As an important factor in the natural environment,terrain has a certain influence on the spatial differentiation of vegetation and soil nutrients.Based on the Landsat TM image data of 1987,1995,2007 and 2014,and the Pixel Dichotomy Model was used to estimate the vegetation coverage of the Beiluo River Basin and its upper reaches,and the terrain factor which extracted from DEM terrain elevation data was combined to analysis the laws of vegetation coverage vary with the terrain and the dynamic change characteristics.So as to provide basic information for the ecological construction and benefit evaluation of the region.At the same time,the vegetation growth status and the spatial distribution of soil nutrients in the Zaozhuanggou catchment of Wuqi County were analyzed by field sampling,and the vegetation growth status and spatial variability of soil nutrient in terrain were explored to determine the relationship between vegetation growth and soil nutrient which can provide a scientific basis for the ecological environment.And the main conclusions are as followed:(1)Ninety percent of the area in the basin was the hilly-gully and the table-gully regions;sixty-seven percent of the areawas the slope with the gradient ranging from 8°to 25°;the area of the four slope aspects was almost equal.The average vegetation coverage in the basin increased from 41.1% in 1987 and 45.4% in 1995 to 63.4% in 2007.(2)In upper reaches of the Beiluo River Basin,the average vegetation coverage increased from 20.21% in 1995 and 41.64% in 2007 to 51.22% in 2014.The vegetation coverage is low in 1995.The area of low coverage(average vegetation coverage <20%)is the largest,accounting for 54.04%;In 2007,the vegetation coverage increased rapidly,the area of moderate coverage(40~60%)increased significantly,and the growth rate was 41.34%;The vegetation cover situation in 2014 is more improved than in 2007,among them the coverage area of the high(>80%)and the mid-high(60~80%)are significantly increased,and the area of moderate,mid-low(20~40%)coverage decreased obviously.(3)The total area of Zaozhuanggou small catchment is 1.59km2,the main land use types are grassland,shrub land,terraced fields,forest land and dam land,and the area of grassland is 1.29 km2 which accounting for 81.13% is the largest among the types.The proportions of Flat slope(<5°),Gentle slope(5~8°),Slope(8~15°),Steep slope(15~25°),Hard slope(25~35°),Dangerous slope(>35°)are 2.23%,1.29%,7.38%,23.03%,35.52%,30.65% respectively.The relationship between the area of different aspect is semi-shady slope(38.27%)> semi-sunny slope(26.58%)> sunny slope(25.11%)> shady slope(9.39%).(4)A total of 71 species of grassland in Zaozhuanggou watershed were investigated.The main species were 29 species,belonging to 16 families and 16 genera.In different landscape positions,the magnitude of the Simpson index in the community increases from Slope top to Slope below,and reaches a peak(0.760)at Slope blow,then decreases to 0.689 at Groove slope.Similarly,the Shannon-Wiener index,Margalef index,Pielou index and the biomass have the same trend.In different slopes,the ? indices and the biomass show a slow increase in the fluctuation.Approximately,they reach two peaks on the 0-5 ° and 5-15 ° slope zones.In semi-shady and semi-sunny slope,the Simpson,Pielou,Shannon-Wiener and Margalef indices are bigger than them in shady and sunny significantly,and the biomass is biggest in shady slope.(5)There are significant differences in the average contents of organic matter,total nitrogen and total phosphorus among the five land use types in woodland,shrub land,grassland,terraced fields and dam land.Because of the nitrogen fixation effect of seabuckthorn,the highest content of organic matter is shrub land which is much larger than other types of land use,the lowest content is the dam,and the shrub forest organic matter content is 3.25 times the dam,showing a law which is shrub land(16.32g/kg)> grassland(12.56g/kg)> forest land(10.58g/kg)> terraces(9.40g/kg)> dam land(5.02g/kg).The total nitrogen and total phosphorus contents in the dam were the highest,which was significantly higher than that of other land use types.(6)The distribution characteristics of soil nutrient in terrain were analyzed with 94 grassy plots.In different terrain parts,the highest content of soil organic matter is the Slope(15.02g/kg),and the lowest is the Groove slope(9.38g/kg).The trend of total nitrogen is basically the same as that of organic matter.The highest content of total phosphorus is also the Slope(0.87g/kg),the lowest phosphorus content is the lowest part of the Slope center(0.52g/kg).In different aspect parts,the content of organic matter in the shady slope is much larger than that of the semi-shady slope,the semi-sunny slope and the sunny slope,the trend is Shady slope(17.25g/kg)> Semi-shady slope(12.46g/kg)> Sunny slope(12.38g/kg)> Semi-sunny slope(11.3g/kg).The difference of total nitrogen content is little(1.70~1.78 g/kg)in each aspect.The content of total phosphorus varies greatly in each aspect,the trend is Semi-sunny slope(0.94g/kg)> Semi-shady slope(0.69g/kg)> Sunny slope(0.36g/kg)> Shady slope(0.32g/kg).In each slope,the distribution of organic matter content section shows an increasing trend from gentle slope to steep slope in fluctuation,and peak value appears in slope range of 25-35 °.Total nitrogen and total phosphorus content showed a decreasing trend from slow to steep in fluctuation,and the slope was the highest peak. |
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