| In desert areas,the combination of mechanical sand barriers and artificial sand-binding shrubs to restore surface vegetation and improve soil quality is one of the important engineering measures for sand control and ecological restoration.This study took the artificial sand-binding vegetation area on the southeastern margin of the Tengger Desert as the research object,and checkboard of nylon net and wheat straw sand barrier with artificial sand-binding shrubs land for 3 years were selected as study sites,with the surrounding sand-binding shrubs land with no-square sand barriers as control.This study aims to clarify the influence of different sand-binding materials on the soil-vegetation system of artificial forest land,and comprehensively evaluate the ecological effects.Through the combination of field vegetation survey,soil sample collection and indoor sample analysis,we determined the soil physical and chemical properties and fractal dimension of sand-binding forests with different materials,calculated soil quality indexes and investigated vegetation growth characteristics in each site.The growth characteristics were used to analyze the relationship between vegetation growth and soil quality in sand-binding forests with different materials.The main results are as follows:(1)The contents of soil particle of silt in the straw sand barrier plot,nylon net sand barrier plot and the control plot was 4.42%?5.17%,4.07%?4.22%and 2.67%-3%respectively,and the contents of soil particle of very fine sand was 79.28%?80.06%,74.98%?77.91%and 82.94%?83.60%respectively,whereas the contents of soil particle of fine sand was 14.77%?16.20%,17.93%-20.95%and 13.56%?14.17%respectively.The layout of the sand barrier reduced the contents of very fine sand and increased the contents of silt,but had little effect on the contents of fine sand.Whereas there were no significant differences between the contents of silt in the straw sand barrier plot and nylon net sand barrier plot.This shows that straw sand barrier has limited effect on increasing silt contents relative to nylon net sand barrier.Soil particles were not effected by seasonal variation.(2)The fractal dimension in the straw sand barrier plot,nylon net sand barrier plot and the control plot was 1.15?1.24,1.08?1.12 and 0.77?0.89 respectively.This shows that the layout of the sand barrier increases soil fractal dimension.Whereas there were no significant differences between the soil fractal dimension in the straw sand barrier plot and nylon net sand barrier plot.It shows that straw sand barrier has limited effect on increasing soil fractal dimension relative to nylon net sand barrier.The contents of soil organic carbon followed the order of straw sand barrier plot>nylon net sand barrier plot>control plot,which was less effected by seasonal variation.Soil water content,soil pH and soil bulk density were less effected by different material sand barriers,whereas were more effected by seasonal variation.Soil temperature,soil electrical conductivity and soil total nitrogen were effected by both different material sand barriers and seasonal variation.(3)There was a significantly positive correlation between soil silt contents and soil organic carbon.The contents of very fine sand had a negative correlation with soil organic carbon and total nitrogen.There was a significantly positive correlation between fine sand contents and soil organic carbon.Each kind of soil particle had no correlation with soil water content,soil temperature,soil pH,soil electrical conductivity and soil bulk density.The soil fractal dimension had a significant positive correlation with the content of silt particles and soil organic carbon,whereas no correlation with very fine sand,fine sand,soil water content,soil temperature,soil pH,soil electrical conductivity,soil bulk density and soil total nitrogen.(4)The soil quality comprehensive index of straw sand barrier plot,nylon net sand barrier plot and control plot was-0.18?1.08,-0.03?0.72 and-1.33?-0.16,respectively.The soil quality index of straw sand barrier and nylon net sand barrier was significantly higher than that of the control plot,but there was no significant difference in soil quality index between straw sand barrier plot and nylon net sand barrier plot.The soil quality index of each plot showed an increasing trend with seasonal variation and reached a maximum in autumn.It was indicated that the layout of sand barriers can improve the soil quality of sand-binding forests land,whereas in the early stage of sand-binding(within 3 years),the soil quality improvement effect of straw sand barriers relative to nylon net sand barriers was limited.(5)The height of Caragana korshinskii followed the order of nylon net sand barrier plot>control plot>straw sand barrier plot,with significant difference between each site.Whereas the crown width of Caragana korshinskii of nylon net sand barrier plot was significantly larger than that of the straw sand barrier plot and the control plot,and there was no significant difference between the latter two plots.The height of Artemisia ordosica followed the order of straw sand barrier plot>nylon net sand barrier plot>control plot,with significant difference between each site,and its crown width and the crown width of the Caragana korshinskii showed a consistent change.The height and crown width of Hedysarum scoparium showed no significant difference between each site.Moreover,the biomass of Artemisia ordosica,Caragana korshinskii and Hedysarum scoparium in the three plots were also not significantly different.Correlation analysis showed that the height,crown width and biomass of the three shrubs had no correlation with soil physical and chemical properties and soil quality indicators.(6)Comprehensive analysis shows that nylon sand barriers or straw sand barriers are installed on the mobile sand lands with artificial sand-binding shrubs which created in the southeastern margin of the Tengger Desert could facilitate the fine soil particles by ameliorating stressful soil conditions in a short time,enhancing the increase of soil silt contents and soil fractal dimension as well as soil organic carbon content,thus be beneficial for the improvement of soil physical and chemical properties.The layout of sand barriers could improve the comprehensive quality of soil in sand-binding forests land and facilitate desertification control.Whereas,in the early stage of sand-binding(within 3 years),the straw sand barrier has limited effect on improving the silt contents and increasing the soil fractal dimension and soil quality compared with the nylon sand barrier.Moreover,the effects of different materials sand barrier sand fixation measures on the growth and development of different species of shrubs are quite different. |
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