| The southern hilly region of Gannan in Jiangxi Province is an important part of the barrier zone of red soil hills and mountains in southern China,where soil erosion is severe.The rich heat and abundant rainfall provide excellent natural conditions for afforestation.Therefore,it is crucial to study the influence of typical afforestation on regional soil quality in Gannan.This study selected four typical afforestation types,which are relatively geographically concentrated,have the same soil background,and can represent vegetation types in the Gannan hilly region,as well as natural coniferous and broad-leaved mixed forests and wasteland as controls,in Dayu County,Ganzhou City,as the study site.By studying the impact of different vegetation types on soil physicochemical properties,hydrological characteristics,and plant root characteristics,using principal component analysis to establish a minimum data set,and calculating the soil quality index of different vegetation types,this study explored the influence of typical afforestation on soil quality in Gannan.The main research results are as follows:(1)Compared with the natural conifer-broadleaf forest and barren land,the organic matter content of the artificial forest increased by 6.48% and 288.96%respectively,while the stability of soil aggregates increased by 47.54% and 228.94%respectively.The natural water content increased by 48.49% and 73.84%,and the infiltration rate increased by 93.41% and 144.45%,respectively.However,the root length density of the artificial forest decreased by 17.66% compared with the coniferbroadleaf forest,resulting in a decrease in the shear strength value of the artificial forest by 7.46%.(2)The minimum dataset and its weights for the soil quality index of typical artificial forests in southern Jiangxi Province are as follows: mean weight diameter(0.169)> root length density(0.161)> saturated water content(0.160)> sand particles(0.159)> total nitrogen(0.130)> cohesion(0.118)> organic matter(0.102).The results of fitting the minimum dataset and the full dataset soil quality index(R2 = 0.836,p<0.01)show a highly significant correlation between the two,indicating that the soil indicators in the minimum dataset can reflect the vast majority of information in the full dataset,and are a comprehensive reflection of soil quality.(3)The average soil quality index of the artificial forest within a depth of 0-60 cm is 0.65.Compared with the conifer-broadleaf forest and barren land,the soil quality index of the artificial forest increased by 12.07% and 71.05%,respectively.The specific performances of each forest type are as follows: Chinese fir forest(0.69)>navel orange orchard(0.66)> 4-year-old ecological navel orange orchard(0.65)> 10-year-old ecological navel orange orchard(0.64)> 20-year-old ecological navel orange orchard(0.63)> bamboo forest(0.61)> conifer-broadleaf forest(0.58)> barren land(0.38).The Chinese fir forest had the highest soil quality.Among the navel orange orchards,the soil quality of the common navel orange orchard was the highest,and the soil quality index of the ecological navel orange orchard decreased at a rate of 0.29%per year with increasing planting age.The planting of artificial forests reduces soil bulk density,improves soil acidity,increases soil water retention capacity,enhances soil aggregation,and reduces the degree of soil collapse and destruction.Plant roots play an important role in improving the shear strength,so understory vegetation should be retained in the future plantation to give full play to the strengthening effect of roots.At the same time,the soil quality of artificial forests in the study area is superior to that of natural forests,indicating that the restoration of vegetation in artificial forests plays an important role in improving the ecological environment and soil quality in southern Jiangxi. |
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