| Aiming at the scarcity of research on soil moisture,root system,soil N,P,K nutrient characteristics and deep dried soil layers in the strip planting Caragana korshinskii plantation in the loess hilly area of Ningxia,the 20-year rain-fed strip planting Caragana korshinskii was used as the research object,and the sloping farmland was used as the control to have a deeper understanding of the soil moisture,root system and nutrient status of the local strip planting Caragana korshinskii and to provide a basis for the scientific management of the local Caragana twig ecological forest.The soil moisture,nutrients and Caragana root system were measured in 0-1000 cm soil depths,and the vertical distribution characteristics and correlations of deep soil moisture,roots and nutrients were discussed,and the following main conclusions were obtained:(1)With the increase of depth,the soil water content of Caragana korshinskii first decreased and then increased,and finally tended to be stable.The average moisture content between and within the belt was 8.14%and 7.87%,accounting for 49.42%and 47.75%of the farmland,respectively.The inter-band and intra-band moisture content coincide at 920 cm.(2)The soil water storage capacity of Caragana korshinskii forest land was significantly lower than that of agricultural land in the 0-1000 cm profile(P<0.05).Compared with the agricultural land,the soil water storage in the 0-1000 cm profile between and within the Caragana korshinskii forest land was reduced by 745.17 mm and 939.59 mm,respectively,which was equivalent to a decrease of 37.26 mm and 46.98 mm per year compared with the agricultural land.The soil water deficit was evident in the depth range of 300-1000 cm in Caragana korshinskii forest land,and the average water deficit degree in 300-1000 cm soil layer was 38.06%.The average water availability in the depth range of 0-1000 cm between the strip planting Caragana and the strip was 0.14 and-0.12,respectively.The inter-band and intra-band mean values of soil water supply coefficient were 0.39 and 0.28,respectively.The soil water content of each layer of 300-1000 cm between and within the Caragana korshinskii forest land was lower than the stable water content,and the dried soil layer occurred.(3)The root system of the 20-year rain-fed Caragana korshinskii in the southern mountainous area of Ningxia was mainly concentrated in the 0-160 cm soil layer.In the 0-1000 cm soil depths,the root dry weight between the 0-160 cm soil layers and within the zone accounted for 65.67%and 65.44%,respectively.The root surface area density accounted for 77.23%and 75.29%,respectively,and the root length density accounted for 72.19%and 70.87%.With the increase in depth,the root system gradually decreased,and the total root volume within the zone was significantly greater than between zones(P<0.05).(4)The total nitrogen content of the rain-fed Caragana korshinskii in the southern mountainous area of Ningxia decreased with the depth in the 0-1000 cm soil layer,and the total nitrogen was enriched in the surface layer.In the depth range of 0-1000 cm,the total P content in Caragana korshinskii did not change much,and the available potassium content in the depth range of 0-1000 cm showed a decreasing trend with the increase of depth.The total nitrogen content of Caragana korshinskii was weakly variable in the depth range of 0-1000 cm,and the average variation coefficient of 0-1000 cm was 13.19%.The total phosphorus content of Caragana korshinskii in 0-300 cm and 600-700 cm soil layer belonged to weak variation coefficients of 14.20%and 14.41%,respectively;in 300-600 cm and 700-1000 cm,it belonged to moderate variation,with variation coefficients of 18.25%and 18.30%,respectively;the coefficient of variation of the content of available potassium in Caragana korshinskii at 0-500 cm and 700-1000 cm was 3.15%and 9.71%,respectively,and the variation coefficient at 500-700 cm was 22.07%.(5)There was a significant negative correlation between the depth of the rain-fed Caragana korshinskii forest and each parameter(root surface area density,root length density,root dry weight,total nitrogen content,total phosphorus content,available potassium content,soil water content)in the southern mountainous area of Ningxia(P<0.01).All parameters except total nitrogen and soil water content,and available potassium content do not correlate with soil water content;the other parameters are extremely significantly correlated.The water content of the belted rain-fed Caragana korshinskii forest land in the mountainous area of southern Ningxia showed a trend of decreasing with the increase of depth and finally tending to be stable.The 20-year Caragana korshinskii deep soil water is deficient with the poor water availability,low water supply coefficient,thus it is difficult for Caragana korshinskii to absorb water.The root system gradually decreased with the increase in depths,and the total root volume within the zone was significantly greater than between zones.The soil total nitrogen content in the 0-1000 cm profile was enriched in the surface layer.However,the total phosphorus content had no significant difference,and the available potassium content decreased with increased depth.Caragana korshinskii root system was significantly correlated with soil water and nutrient. |
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