| There is a large number of abandonment in mountain jujube forests in the loess area of northern Shaanxi,in order to clarify the soil quality of mountain jujube forests under different abandonment years,so as to improve the quality and efficiency of abandoned jujube forests and high-quality development in the future study area.Provide scientific basis and data support.In this study,the soil quality evaluation of mountain jujube forests and abandoned grasslands abandoned for 1 a,3 a,6 a,10 a,15 a,20 a in the study area reveals the soil physical and chemical properties,soil microbes and other indicators of mountain jujube forests with different abandonment years.In response to the number of years of abandonment,the principal component analysis method was used to score comprehensively the soil quality of different years of abandonment,so as to clarify the soil quality of the jujube forest in different abandonment years.The main research conclusions are as follows:(1)The soil water content of jujube forests under different abandonment years shows hierarchical and volatility with seasonal changes.The soil water content of0-100 cm soil layer is most obviously affected by seasonal changes,and the deep soil water content changes Small and relatively stable.The average soil water content of the 0-340 cm soil layer of each forest land is 8.13%,and the average water storage capacity is 361.87 mm;the average summer soil water content is 9.28%,and the average soil water storage capacity is 397.41 mm;the autumn soil water content and soil water storage capacity.They are between 4.24%-15.94% and 282.12 mm-465.31 mm.There are differences in the degree of soil water storage deficit and the compensation degree of water storage deficit in jujube forests under different abandonment years.In the 0-100 cm soil layer,the soil water storage deficit of each plot showed a trend of first decreasing and then increasing with the increase of the soil depth;the summer soil water storage compensation degree of each plot was in the200-340 cm soil layer.Both are negative values,that is,summer rainfall does not compensate for the deep soil water,and the soil water deficit is aggravated.(2)In the 0-20 cm soil layer,the silt content is the highest in the 6 years after abandonment,and the lowest in the 20 years after abandonment;in the 20-40 cm soil layer,the clay content is the highest in the 3 years after the abandonment,the soil gravel content is the highest in the 20 years after the abandonment,and the lowest in the 6 years after the abandonment.As the depth of the soil layer increases,the soil bulk density of each forest land generally increases;with the increase in the number of years of abandonment,the soil bulk density first increases and then decreases.With the increase of soil depth,the soil non-capillary porosity showed a trend of first decreasing and then increasing.At 0-20 cm,the maximum water holding capacity of the soil is the largest in 20 years and the smallest in 1 year.The maximum water holding capacity is 46.70% and 35.12%,respectively.There are significant differences in the capillary water holding capacity of each forest land under different abandonment years(P<0.05).(3)The soil organic carbon content has obvious surface aggregation.As the depth of the soil layer increases,the soil organic carbon content gradually decreases.The average organic carbon content of 0-10 cm soil is 10.05 g/kg,and the organic carbon content of 100-340 cm is organic.Carbon storage accounts for 61% of the entire soil profile.Under different abandonment years,the deep soil organic carbon content gradually decreases with the increase of the abandonment years,and the difference is not significant,that is,the abandonment years have little effect on the distribution of deep soil organic carbon.Among the 0-20 cm soil layer,the soil organic carbon storage of 15 years of abandonment was the largest,26.15 t/hm2;the soil organic carbon storage of 1 year was the least,18.69 t/hm2.The soil p H of different abandoned forest lands was all greater than 8,and the soil was alkaline.The total amount of soil,available nutrient content and soil enzyme activity of each forest land showed a decreasing trend with the increase of soil depth.Among them,the content of soil available phosphorus increased with the increase in the number of years of abandonment;the content of soil available phosphorus in the 20 years after abandonment was as high as 30.01 mg/kg.As the depth of the soil layer increases,the soil C:N shows an upward trend.The change trend of soil C:P of each forest land under different abandonment years is different,and the overall range is 9.32-45.47.The soil N:P of each forest land under different abandonment years is between0.14-2.11.(4)A total of 36 phyla,101 classes,208 orders,313 families,and 504 genera of bacteria were detected in the soil of jujube forests in different years of abandonment.The soil bacteria group is mainly Actinobacteria(31.95%),Proteobacteria(29.93%),Acidobacteria(12.62%),followed by different abandonment years of jujube woodland soil bacteria group is Gemmatimonadetes(8.19%),Chloroflexi(7.53%),Bacteroidetes(2.63%),Verrucomicrobia(1.14%),Planctomycetes(1.13%)and Rokubacteria(1.11%)mostly.A total of 10 phyla,33 classes,75 orders,162 families and 269 genera of fungi were detected in the soil of jujube forests in different years of abandonment.The soil fungi phyla are mainly Ascomycota and Basidiomycota,with Mortierellomycota dominated.(5)A total of 21 soil indicators were selected for principal component analysis,and soil clay,soil p H,soil water content,total soil porosity,organic carbon,available phosphorus,total nitrogen,catalase,and invertase were screened out.A total of 10 soil indicators with urease were used to evaluate soil quality.Based on the soil quality index method,the total score of abandonment of soil quality was the highest for 15years(0.823),followed by 20 years(0.755),and abandoned grassland was the smallest(0.300).Based on the modified Nemero index method,the total score of abandoned soil quality was the highest for 15 years(0.601),followed by 10 years(0.582),and the lowest(0.223)for abandoned grassland. |
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