Study On The Stability Of Soil Aggregates In Paulownia Plantation And Its Influencing Factors

The fast-growing Paulownia plantation and its rotation will consume ground power,destroy the stability of the soil structure and cause soil erosion,which will aggravate the decline of ground power.Soil aggregates are one of the important elements that reflect the stability of the soil structure,and its ability to retain water and fertilizer can measure the quality of the soil.From the perspective of aggregates,this paper takes 4 forest-age Paulownia plantations and control evergreen broad-leaved forests in Xiangyin county,Hunan province as the research objects Three standard plots are set for each forest stand.and each plot is set at 0-20cm,20?40cm,40?60cm,60?100cm take soil examples in 4 layers to measure soil properties,aggregate stability and nutrient at particle size.The purpose is to explore the stability of soil aggregates in Paulownia plantation,and to analyze its influencing factors through correlation,stepwise regression,and construction of structural equation model.The main conclusions are as follows:(1)With the decrease of particle size,the content of mechanically stable aggregates showed a gradual decrease trend,and the water-stable aggregates showed a"W"-like change trend.With the increasing age of the forest,the mechanical stability of the aggregates increased and then decreased.The overall water stability of the aggregates was 2 and 4-year-old>10-year-old,evergreen broad-leaved forests>13-year-old.The order of the influence of different forest types on the overall stability of soil aggregates is 13-year-old>evergreen broad-leaved forest>4-year-old>2-year-old>10-year-old.The overall stability of the 13-year-old is relatively low.and corresponding management measures can be added.(2)SAT has significant differences among soil layers,showing a trend of 13-year-old>evergreen broad-leaved forest>2 and 10-year-old>4-year-old.The contents of SOC,TN,TP,and TK generally showed a trend of 2-year-old>10 and 13-year-old>4-year-old and evergreen broad-leaved forest.With the increase of forest age,pH showed a trend of increasing first,then decreasing and then increasing.The CEC,MBC,and MBN have the highest content in 13-year-old.The content of MBP is the highest in 2-year-old and the lowest in 13-year-old.The effects of different forest types on soil properties showed that 10-year-old>2-year-old>13-year-old>evergreen broad-leaved forest>4-year-old.In the mechanical composition,the content of silt particles is generally higher than that of clay particles and sand particles,and the content of clay particles is relatively high in 10-year-old.The content of each soil layer of the particle nutrient is significant,and decreases with the decrease of the particle size,then increases and then gradually decreases.The content of particle nutrient in seedling forest,middle-aged forest and mature forest of 4 particle size aggregates was higher than that of young forest and evergreen broad-leaved forest.Among the<0.25mm micro-aggregates,the 2-year-old SOC and deep soil layer TP content are higher,the 13-year-old SOC is relatively low,and the particle nutrient content of 10-year-old is relatively high overall.The order of the influence of different forest types on particle nutrient is 2-year-old>13-year-old>4-year-old>10-year-old>evergreen broad-leaved forest.(3)BD,CEC,MBN,and MBP are significant factors.Among them,the mechanical stability of aggregates is positively correlated with BD,negatively correlated with CEC and MBN,and MBP is positively correlated with water stability of aggregates.Moreover,the mechanical stability of aggregates is negatively correlated with water stability.Microaggregates of<2?m size are significant influencing factors of the mechanical stability of aggregates and have a positive correlation.In microaggregates with a particle size of<0.25mm,SOC has a significant and positive correlation with water-stable aggregates,and TP has a significant effect on the overall stability of aggregates.2?1mm particle size TP and TK are the significant factors affecting the mechanical stability of soil aggregates and have a negative correlation.(4)The structural equation model shows that SOC,TN,TP,TK,CEC,and MBN have a significant effect on soil properties.The weight of SOC on soil properties is 0.83,which is the highest contribution.Soil properties are negatively correlated with aggregate stability and have a weight of-0.16.