Diversity characteristics of herbaceous species under Robinia pseudoacacia forest in different years
[Objective]This study,with an investigation into the species composition and diversity index of herbaceous layer under Robinia pseudoacacia forests in the hilly gully region of the Loess Plateau,is aimed to explore the characteristics and main influencing factors of its diversity index,in order to provide reference for the practice of regional vegetation restoration.[Method]With the R.pseudoacacia forests in different years(7,12,22 and 45 years)in Zichang City selected as study subjects,the species composition of the herbaceous layer in the understorey of R.pseudoacacia forests of different years were investigated employing the"space instead of time"method and the plot survey method before an analysis was conducted of the main factors influencing the diversity index using redundancy analysis(RDA).[Result](1)There were 55 species of herbaceous species in R.pseudoacacia forests of different years,belonging to 18 families,and their dominant species were mainly Asteraceae,Gramineae and Leguminosae,with the overall performance showing that the dominant species belong to a few families,while the subordinate species belong to most families;the Artemisia vulgaris,A.caruifolia and A.gmehinii have higher importance values;(2)The aboveground biomass of understory herbaceous in R.pseudoacacia forests increased with years,and planting years increased significantly the aboveground productivity of the herbaceous layer(P＜0.05).(3)Ammonium nitrogen,soil organic carbon,soil moisture and total phosphorus were the main factors influencing the Margalef and Simpson index of species diversity as well as aboveground biomass of the understory herbaceous layer whereas total nitrogen,total phosphorus,ammonium nitrogen,and soil silt were the main factors affecting Shannon-Wiener and Pielou index.[Conclusion]The herbaceous layer of R.pseudoacacia forests in the study area showed different species diversity at different years.Artemisia plants showed great adaptive ability at different years,and species diversity indicators and biomass are significantly affected by soil moisture and nutrients.Therefore,it is important to focus on the balance of soil moisture and nutrients in future afforestation practices in the Loess Plateau region to enhance the stability and sustainability of plantation ecosystem development.[Ch,2 fig.2 tab.31 ref.]
different yearsunderstory herbaceous layerspecies diversityaboveground biomassinfluencing factors
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