| After the implementation of returning farmland to forests and grassland projects,the vegetation in the Loess Plateau had undergone tremendous changes,vegetation coverage had increased significantly,and vegetation properties had changed due to vegetation litter and root.The improvement of the soil properties of gully head by the vegetation restoration effectively enhanced the soil erosion resistance and slowed the advancement.However,the research on the influence of typical vegetation communities on the soil properties of gully head was rarely reported.Therefore,this study took the typical vegetation communities of gully head as the research object,and investigated the first-level branch gully head in the Nanxiaohegou watershed of Dongzhiyuan,Qingyang City,Gansu Province,and selected the typical vegetation communities of Stipa bungeana?Agropyron cristatum?Lespedeza davurica?Artemisia scoparia?Artemisia atrovirens?Bothriochloa ischaemum?Medicago sativa and Medicago sativa+Artemisia scoparia for investigating.The community characteristics of the gully vegetation and the root characteristics of the 070 cm soil layer were investigated.The soil properties of the 070 cm soil layer in the typical vegetation community were studied with the agricultural land gully as the control.This study explored the difference of typical vegetation community characteristics and soil properties of gully heads,analyzed the relationship between vegetation community characteristics and soil properties,deepened the understanding of vegetation restoration's impact on soil erosion in loess tableland,and provided a scientific basis for the sustainable use of vegetation and ecological environment construction in the reclamation area.The main conclusions were as follows:?1?A total of 42 species of herbaceous plants appeared in 21 survey sites in the first branch gully heads of Nanxiaohegou Basin,belonging to 13 types,and 66.67%belonged to Gramineae,Asteraceae,and Leguminosae.The three plant types played an important role in the ecosystem of gully heads.The typical vegetation communities of the gully heads had Patrick richness index of 6-18,Simpson index of 0.150.33,Simpson dominance index of 5.3316.00,and Pielou evenness index of 0.750.89.?2?The root mean diameter of the typical vegetation communities of gully head was 0.550.80 mm,the root biomass was 2.53×1032.15×104 g/m3,and the root volume was 8.44×10-65.93×10-55 m3.The root biomass and root volume of Agropyron community were the largest,which were the smallest in Artemisia scoparia community.The specific root length was 15.8462.07 m/g,and there was no significant difference between the typical vegetation communities?P>0.05?.The specific root length of Lespedeza davurica community and Bothriochloa ischaemum community were larger than others.The root specific surface area was 0.030.09 m2/g,and the root specific surface area of Medicago sativa community was significantly higher than others?P<0.05?.The root length density was 7.77×1043.44×105 m/m3,and the root surface density was 133.10588.64 m2/m3.The root length density of Leymus chinensis community,Stipa bungeana community and Agropyron community was higher than other communities?3?On the vertical section of 070 cm soil layer,the root mean diameter of Stipa bungeana community,Leymus chinensis community,Artemisia scoparia community,Medicago sativa+Artemisia scoparia community was not significantly different with soil layer change?P>0.05?.The root mean diameter of the Agropyron community,the Lespedeza davurica community,Medicago sativa community and Artemisia atrovirens community decreased with the deepening of the soil layer.More than41.70%of root biomass in all communities was concentrated in 0-10 cm of top soil layer.The root volume of each typical vegetation community decreased with the increase of soil depth.The specific root length in 0-10 cm soil layer of Artemisia atrovirens community was significantly smaller than the other soil layers?10-70 cm??P<0.05?,and the other communities'specific root length did not change with the soil layer incresed?P>0.05?.The root surface area in 0-10 cm soil layer of Agropyron community,Lespedeza davurica community and Artemisia selengensis community was significantly smaller than that of other soil layers?10-70 cm??P<0.05?,and the other community specific surface area did not change with the soil layer incresed.The root length density of 0-10 cm soil layer of all communities was significantly greater than that of the remaining soil layers?10-70 cm??P<0.05?,and the root length density decreased with increasing soil depth.The root surface area density of each typical vegetation community in gully head decreased with the increase of soil depth.?4?The soil water content of typical vegetation communities in gully head was10.12%19.16%,the soil water content of the Artemisia scoparia community was12.90%higher than cropland,and the other communities were 0.81%40.39%lower than cropland.In the vertical distribution of soil,the water content of the soil of Stipa bungeana community,Artemisia scoparia community,Bothriochloa ischaemum community,Medicago sativa+Artemisia scoparia community decreased first and then increased with the deepening of the soil layer.The soil water content of Agropyron cristatum community,Lespedeza davurica community and Artemisia selengensis community increased with the deepening of the soil layer,and the soil water content of Medicago sativa community decreased with the deepening of the soil layer.The soil bulk density of typical vegetation communities in gully head was 1.181.52g/cm3,and the soil bulk density of Medicago sativa+Artemisia scoparia community increased by 7.77%compared with cropland,and the other communities decreased by0.37%15.87%compared with cropland.In the vertical distribution,the bulk density of Agropyron cristatum community and Artemisia scoparia community increased with the deepening of the soil layer,and there was no significant difference between the soil layers of Stipa bungeana community?P>0.05?.The soil bulk density of Lespedeza davurica community,Bothriochloa ischaemum community,Medicago sativa community and Medicago sativa+Artemisia scoparia community increased first and then decreased.The soil bulk density of Artemisia scoparia community decreased first and then increased.The total soil porosity of the typical vegetation community in gully head was 35.55%60.38%,and the soil organic matter content was 0.75%1.53%.?5?The water-stable aggregate content of typical vegetation communities in gully head was 24.51%44.85%,the average weight of the aggregate was 0.361.06 mm,the geometric mean diameter of the aggregate was 0.190.38 mm,and the fractal dimension of soil aggregate was 2.732.90.The water-stable aggregate content of the cropland was 23.48%,the average weight diameter was 0.33 mm,and the geometric mean diameter was 0.19 mm,which were significantly smaller than typical vegetation communities?P<0.05?.The fractal dimension of the soil aggregate in the cropland was 2.91,significantly larger than the vegetation gully heads?P<0.05?.The water-stable aggregate content,average weight diameter and geometric mean diameter of typical vegetation communities in gully head decreased significantly with the soil depth?P<0.05?.The fractal dimension of aggregate of the typical vegetation communities in gully head increased significantly with the deepening of the soil layer?P<0.05?.?6?The response between soil properties and typical vegetation community characteristics was:There was a significant positive correlation between soil water content and Patrick richness index?P<0.01?;soil total porosity was significantly positively correlated with Patrick richness index?P<0.01?and significantly positively correlated with the Shannon-Wiener index?P<0.05?.There was no significant correlation between soil bulk density,soil organic matter content,soil aggregate characteristics and vegetation diversity index?P>0.05?.The relationship between soil properties and root characteristics was:There was a significant correlation between soil water content,soil organic matter content,soil water stable aggregate content,average weight diameter,geometric mean diameter,aggregate fractal dimension and root biomass,root surface area density?P<0.01?.The above indicators were significantly correlated with root length density except soil water content?P<0.01?.Soil water content,soil water stable aggregate content,average weight diameter,fractal dimension of aggregate and root volume were significantly correlated?P<0.05?,and soil water content was significantly correlated with root length density?P<0.05?.There was a significant correlation between soil organic matter content and root diameter?P<0.05?.There was no significant correlation between soil bulk density,total porosity and vegetation root index?P>0.05?. |
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