| The response of soil aggregate composition and stability and its carbon（C）,nitrogen（N）and phosphorus（P）stoichiometric characteristics to land use change and vegetation restoration is of great significance to the protection and restoration of fragile ecological environment.This study takes 7 kinds of land use types（arbor forest land,sparse forest land,shrub forest land,grassland,bare land,corn land and abandoned land）and 7 kinds of vegetation restoration（Tectona grandis,Cupressus funebris,Zanthoxylum bungeanum,Hylocereus undatus,Lonicera japonica,Pennisetum sinese and Amomum villosum）in Guanling Zhenfeng Huajiang rocky desertification plateau Canyon comprehensive treatment demonstration area in Guizhou as the research object.The wet sieve method was used to separate the particle size of soil aggregates（>2mm,2-0.25 mm,0.25-0.053 mm and <0.053mm）,study the response of the composition and stability of soil aggregates in three soil layers of 0-5cm,5-10 cm and 10-15 cm to land use and vegetation restoration,and study the impact of land use and vegetation restoration on the stoichiometric characteristics of C,N and Pof soil aggregates,and explore the main soil physical and chemical factors affecting the composition,stability and stoichiometric characteristics of C,N and Pof soil aggregates,It provides scientific basis for vegetation restoration,soil and water conservation and land use regulation of karst ecosystem.The main findings include:（1）The composition of soil aggregates in the study area is mainly large aggregates with particle size of >0.25mm（except grassland）,and grassland is mainly with particle size of 2-0.25 mm and <0.053 mm,and there is no significant difference in the composition of soil aggregates.Among the seven kinds of land use,arbor forest land,open forest land and corn land accounted for a relatively high proportion of large aggregates.The stability of soil aggregates in corn field and abandoned land is stronger,while the stability of soil aggregates in bare land and grassland is weaker.In 7 vegetation restoration,the proportion of large aggregates of Tectona grandis,Cupressus funebris and Lonicera japonica was significantly higher than that of bare land.The stability of soil aggregates of Cupressus funebris and Lonicera japonica is higher,while that of Zanthoxylum bungeanum and Pennisetum sinese is lower.Among them,the stability of soil aggregates of Tectona grandis,Cupressus funebris,Hylocereus undatus,Lonicera japonica and Amomum villosum was significantly improved compared with bare land.The stability of soil aggregates tends to be higher in surface soil than in deep soil in different land use,but there is no significant difference in soil layer in different vegetation restoration.The correlation study showed that the higher the mass fraction of large aggregates,the stronger the stability of soil aggregates.（2）Among the seven land use modes,the C and N contents of soil aggregates are higher in open woodland and abandoned land,and lower in arbor woodland and grassland.The grain size of >2mm and 2-0.25 mm is higher,and the grain size of 0.25-0.053 mm is lower.The Pcontent of soil aggregates was higher in bare land and abandoned land,lower in arbor forest land,shrub forest land and grassland,and there was no obvious regularity in the Pcontent of aggregates in each particle size.In 7vegetation restoration measures,the C content of aggregates is higher in Tectona grandis,Cupressus funebris and Lonicera japonica than that in bare land,and lower in Pennisetum sinese and Amomum villosum.The particle sizes of >2mm and 2-0.25 mm are higher,and the particle sizes of0.25-0.053 mm are lower.The overall N content of aggregates showed that Tectona grandis,Cupressus funebris,Zanthoxylum bungeanum,Hylocereus undatus,Lonicera japonica were significantly higher than those in bare land,while Pennisetum sinese and Amomum villosum were lower than those in bare land.The particle sizes of >2mm and 2-0.25 mm are higher,and the particle sizes of 0.25-0.053 mm are lower.The Pcontent of aggregates was significantly higher in Zanthoxylum bungeanum than that in bare land,but lower in Tectona grandis,Hylocereus undatus,Pennisetum sinese and Amomum villosum.The Pcontent of aggregates in each particle size is greatly different due to different planting measures,but there is no obvious regularity.The content of C,N and Pin soil aggregates in 14 sample plots decreased with the deepening of soil layer.（3）Among the seven land use modes,the aggregate C and N of arbor forest land,sparse forest land and abandoned land are higher,while that of grassland,bare land and corn land are lower.The C Pratio and N Pratio of soil aggregates were significantly higher in arbor forest land,sparse forest land and shrub forest land than in grassland,bare land,corn land and abandoned land.There was no significant difference in the ratio of C to N between the restored aggregates and the control plots.Among them,Tectona grandis and Cupressus funebris were higher than those of Zanthoxylum bungeanum,Hylocereus undatus and Pennisetum sinese.The C/P ratio and N/P ratio of soil aggregates were higher in Tectona grandis,Cupressus funebris and Hylocereus undatus than in bare land,Pennisetum sinese and Amomum villosum.The stoichiometric ratio of C,N and Pof soil aggregates in 14 sample plots had no obvious change law of soil layer.In terms of particle size difference,aggregate C/N ratio and C/P ratio have different particle size differences in different land cover,but there is no obvious common law.（4）Through correlation analysis and redundancy analysis（RDA）of environmental factors affecting the composition and stability of soil aggregates,it is found that soil bulk density and 2-0.25 mm particle size fraction showed a negative correlation with 0.25-0.053 mm and<0.053 mm particle size fraction is a positive correlation.Soil p H and0.25-0.053 mm particle size fraction has a negative correlation.Soil total organic C,total N and total Pcontent and >2mm and 2-0.25 mm particle size fraction is roughly positively correlated with 0.25-0.053 mm and<0.053 mm particle size fraction showed a negative correlation.Stoichiometric characteristics of soil C and Paggregates 2-0.25 mm particle size fraction is roughly positively correlated with 0.25-0.053 mm and <0.053 mm particle size fraction showed a negative correlation.Soil total organic C,aggregate C content and aggregate C N ratio are the main influencing factors of soil aggregate stability,which are roughly positively correlated with soil aggregate stability.In addition,under the background of vegetation restoration,there is a negative correlation between soil bulk density and aggregate stability. |
PDF Full Text Request