Study On Soil Property And Water Holding Characteristics Of Different Vegetation Belt In The Loess Plateau

Vegetation restoration has effectively improved the ecological environment of the Loess Plateau.It is of great significance to study the influence of vegetation restoration on the near surface characteristics to accurately evaluate the ecological effect of the project of returning farmland to forest(grass)in the Loess Plateau.The vegetation zonality distribution in the Loess Plateau is obvious,and the transition from forest zone to grassland zone leads to significant differences in vegetation growth patterns and aboveground characteristics due to the limitation of climate and water conditions.In this study,different vegetation zones(forest zone,forest steppe zone,grassland zone)were used as sample points,and plant communities under different site conditions(middle sunny slope,lower sunny slope,top of slope,middle shady slope,lower shady slope)were studied.The main results were as follows:(1)In this study,116 species of 87 genera and 35 families were investigated.More than half of the species are composed of Gramineae,Leguminosae,Rosaceae and Compositae,accounting for 56.9%of the total number of species,and the remaining 43.1%belong to 31 families and 41 genera.The plant community growth type and life type are both forest belt>forest grassland belt>grassland belt.The growth type is mainly perennial herbs,and the living type is mainly semi-hidden bud plants.the number of species,Margalef richness index and Shannon-Wiener diversity index were all forest zones>forest steppe zones;the Simpson dominance index was grassland zone>forest steppe zone.there was no significant difference in the Pielou evenness index in the three vegetation zones.The coverage and aboveground biomass are forest belt>forest grassland belt>grassland belt.Slope position and slope direction had significant influence on coverage and biomass.The cover degree is shady slope>slope top>sunny slope,forest belt is gully slope>Liangpo,forest grassland belt is the highest in the middle of Yinpo,the upper part of Yangpo is the lowest,grassland belt is Liangpo>gully slope,aboveground biomass is>slope.(2)Soil structure and nutrient status are affected by vegetation community type,slope and slope.The overall content of soil water stability of>0.25mm is the>grassland belt of>forest belt.The forest belt is the largest of the lower slope,the lowest of the lower slope,the lower slope of the largest,the top of the lowest slope,the largest of the middle slope and significant differences under different vertical conditions.The soil organic carbon content in different vegetation zones is forest belt>forest grassland belt>grassland belt,forest belt is 8.80-12.71 g/kg,shady slope>slope top,forest grassland belt is 6.31-11.84,sunny slope>shady slope top,grassland belt is 3.89-8.03 g/kg,the lower part of sunny slope is the highest,and the middle part of shady slope is the lowest;The distribution of soil total nitrogen content is forest belt>forest grassland belt>grassland belt,forest belt is 0.68-1.22 g/kg,the lower part of Yin slope is the highest,the lower part of sunny slope is the lowest;forest grassland belt is 0.56-1.58 g/kg,sunny slope>shady slope top;grassland belt is0.22-0.59 g/kg,sunny slope>slope top and shady slope,the difference is significant under different site conditions(P<0.05);The distribution of soil total phosphorus content is forest belt>forest grassland belt>grassland belt,forest belt is 0.48-0.68g/kg,forest grassland belt is 0.56-0.62 g/kg,grassland belt is 0.30-0.46.(3)There are obvious differences in the distribution of litter volume and water holding characteristics in different vegetation zones.The volume was forest belt(154.25-392.95 g/m~2)>forest grassland belt(151.27-287.58 g/m~2)and grassland belt(109.24-174.81 g/m~2).The natural moisture content,maximum moisture holding volume and maximum moisture absorption ratio are all different under different vertical conditions.The natural moisture content,maximum water holding capacity and maximum moisture absorption ratio of litter under different site conditions are different.Forest belt,forest grassland belt and grassland belt have natural moisture content of 28-54.5%,26.8-41%and 20.7-31.3%,respectively,and the difference is significant under different site conditions(P<0.05).The maximum water holding capacity is 3.26-3.64,2.94-3.2,1.63-1.92 times,and the maximum moisture absorption ratio is 3.26-3.64,2.94-3.21,2.63-2.92 times,respectively.The effective storage amount of dead objects is the forest belt(219.86-787.09 g/m~2)>forest grassland belt(188.15-437.7 g/m~2)>grassland belt(99.89-181.22 g/m~2),dry water holding relationship and water immersion time under different vertical conditions:Y=alnt+b(R~2>0.91),the water absorption rate and soaking time:V=kt~n(R~2>0.99),both show good correlation.