Study On Soil Aggregate Stability Of Different Forest Types In Anning River Basin

The Anning River Basin is located in the upper reaches of the Yangtze River,where the ecological environment is fragile.Combined with unreasonable human activities,the area of soil erosion in this region is large.In order to slow down the rate of soil erosion and reduce water and soil loss,a large number of artificial forests are planted locally for ecological restoration.In order to explore the stability characteristics and related influencing factors of soil aggregates under different forest types,four forest types(Cyclobalanopsis glauca Forest,Eucalyptus Forest,pinus yunnanensis Forest,and Cyclobalanopsis glauca pinus yunnanensis Mixed Forest)with a forest age of more than10 years were selected in the Anning River Basin.Based on a comprehensive analysis of soil aggregate stability,soil physicochemical properties,and community characteristics,combined with correlation analysis,regression analysis,and other methods,the soil physicochemical properties were further revealed The relationship between the two major factors of community characteristics and the stability of soil aggregates.To provide theoretical reference for soil erosion prevention and control work such as ecological restoration and artificial forest breeding in the region.The main research findings are as follows:(1)Analyze soil aggregates in three soil layers(0-10 cm,10-20 cm,20-30cm)under four forest types in the study area.The results indicate that:(1)The four forest types are mainly composed of aggregates>0.25 mm.After wet screening,the particle size of soil aggregates significantly decreases and their stability decreases.(2)The stability of soil aggregates in different forest types was comprehensively evaluated using entropy weight method and linear weighting method,and the results showed that the stability of aggregates in mixed forests was relatively high.In the 0-10 cm soil layer,the stability index of soil aggregates is as follows: mixed forest(0.836)>eucalyptus forest(0.581)>Cyclobalanopsis glauca forest(0.476)>Yunnan pine forest(0.382).In a soil layer of 10-20 cm,the stability index of soil aggregates is as follows: mixed forest(0.915)>Yunnan pine forest(0.558)>Cyclobalanopsis glauca forest(0.497)>eucalyptus forest(0.320).In a soil layer of 20-30 cm,the stability index of soil aggregates is in the order of mixed forest(0.856)>Cyclobalanopsis glauca forest(0.370)>Eucalyptus forest(0.251)>Yunnan pine forest(0.236).(2)Based on the analysis of soil physicochemical properties of different forest types,it is concluded that:(1)The difference in soil moisture and pore characteristics under different forest types is most significant in the 0-10 cm soil layer.In the 0-10 cm soil layer,the natural moisture content,saturated moisture content,and field water capacity of the soil are all in the order of Cyclobalanopsis glauca forest>mixed forest>Yunnan pine forest>eucalyptus forest.The soil bulk density is in the order of Yunnan pine forest>Cyclobalanopsis glauca forest>eucalyptus forest>mixed forest,and the total porosity of the soil is in the order of mixed forest>eucalyptus forest>Qinggang forest>Yunnan pine forest.The soil capillary porosity is in the order of Cyclobalanopsis glauca forest>Yunnan pine forest>mixed forest>eucalyptus forest,The non capillary porosity of the soil is as follows: Eucalyptus forest>Mixed forest>Cyclobalanopsis glauca forest>Yunnan pine forest.(2)Among the three soil layers,the permeability of Yunnan pine forest soil is the worst.In the 0-10 cm,10-10 cm,and 20-30 cm soil layers,the eucalyptus forest,mixed forest,and Cyclobalanopsis glauca forest have the strongest permeability.(3)The chemical properties of the soil show that there is a small difference in soil p H between different forest types(5.04～5.91),all of which are acidic soils.The content of soil organic matter is at a moderate to low level(11.43～26.36g/kg),and the content shows a significant downward trend with the deepening of the soil layer.(3)The analysis of community characteristics of different forest types shows that:(1)Herbal communities under different forest types α The diversity index is highest in mixed forests,with the exception of Eucalyptus forest,which has the lowest Margalef richness index.The other three diversity indices are all the lowest in Cyclobalanopsis glauca forest.(2)The aboveground biomass of the herbaceous community ranges from1378 to 2593 g/m2,and the mixed forest is significantly higher than the Cyclobalanopsis and Eucalyptus forests.(3)The water holding capacity of the litter in the Qinggang forest and mixed forest is stronger,with higher storage capacity,maximum water holding capacity,and effective storage capacity compared to the eucalyptus forest and Yunnan pine forest.(4)Spearman correlation and regression analysis were conducted on the stability of soil aggregates and their influencing factors,and the results showed that:(1)There is a positive correlation between saturated water content,field capacity,and aggregate stability in soil moisture characteristics.Among them,there is a significant positive correlation between the saturated water content of Qinggang forest and mixed forest,the field water capacity of Yunnan pine forest,and the stability of aggregates.The regression equation is: aggregate stability index=0.003+0.009 * saturated water content+0.027 *field water capacity.(2)In the soil pore characteristics,the stability of aggregates is negatively correlated with bulk density,and positively correlated with total porosity and capillary porosity.Among them,the stability of aggregates in Qinggang forest and Eucalyptus forest has a significant relationship with bulk density and total porosity.The regression equation is: aggregate stability index=1.558-0.951 * bulk density+0.006 capillary porosity.(3)In the soil chemistry characteristics,the aggregate stability is positively related to the organic matter content,and negatively related to the p H value.Among them,the stability of aggregates in Qinggang and Eucalyptus forests is significantly correlated with organic matter content and p H.The regression equation is:aggregate stability index=1.565+0.015 * organic matter-0.246 * p H.(4)In the diversity characteristics of understory herbaceous communities,the stability of aggregates is related to α The diversity index shows a positive correlation.Among them,the Shannon Wiener index of four forest types,the Simpson index of Yunnan pine and eucalyptus forests,and the Margalef richness index of Yunnan pine and mixed forests have a significant relationship with aggregate stability.The regression equation is: aggregate stability index=-0.988+0.609 * Shannon Wiener index+0.217 * Margalef richness index.(5)Among the biomass characteristics,there is a positive correlation between aboveground biomass,root biomass,and aggregate stability.Among them,there is a significant positive correlation between the stability of aggregates in Cyclobalanopsis glauca forests,mixed forests,and eucalyptus forests and aboveground biomass.The regression equation is: aggregate stability index=0.270+0.000 2 * aboveground biomass.(6)Among the characteristics of litter,there is a significant positive correlation between the stability of aggregates in Cyclobalanopsis glauca forests,mixed forests,and eucalyptus forests and the volume of litter accumulation.The regression equation is:aggregate stability index=0.335+0.029 * litter accumulation.(7)The R2 regression analysis shows that the Shannon Wiener index,Margalef richness index,litter volume,soil organic matter content,and p H of the understory herbaceous community have a significant impact on the stability of soil aggregates.