林龄和立地条件交互对杨树人工林林下植被多样性的影响OA

[Objective]To reveal the distribution characteristics and influencing factors of understory vegetation diversity under different stand ages and site conditions,this study investigated the understory vegetation of poplar plantations of varying stand ages in the hilly region of southern Jiangsu Province,the coastal mudflats,and the allu-vial plain area of northern Jiangsu Province.[Method]By combining one-way ANOVA,two-way ANOVA,and principal component analysis,the effects of site conditions and stand age on the diversity characteristics of understo-ry vegetation in poplar plantations and their correlations with soil physical and chemical properties were explored.[Result](1)At the middle-aged forest stage,the Shannon-Wiener and Margalef indices of the herb layer in the allu-vial plain area of northern Jiangsu Province were significantly higher than those in the hilly region of southern Jiangsu Province(P<0.05).(2)At the near-mature forest stage,the Shannon-Wiener and Margalef indices of the shrub layer in the hilly region of southern Jiangsu Province were significantly higher than those in the alluvial plain area of northern Jiangsu Province(P<0.05)and those in the coastal mudflats(P<0.01).The two-way ANOVA showed that the interaction between site conditions and stand age had a significant impact on the Shannon-Wiener and Simpson indices of the understory shrubs(P<0.05).(3)The Shannon-Wiener index,Simpson index,Margalef index and Pielou's evenness index of the shrub layer in the understory of poplar plantations were significantly posi-tively correlated with soil organic carbon(SOC)and total nitrogen(TN)content.Comprehensive analysis showed that the diversity of the shrub layer in the coastal mudflats and the alluvial plain area of northern Jiangsu Province was relatively low,and it was mainly affected by factors such as SOC and TN.[Conclusion]This study clarified the distribution characteristics and influencing factors of understory vegetation diversity under the canopy of poplar plantations in different site conditions in Jiangsu Province,which provides a theoretical basis for formulating differ-entiated management measures for poplar plantations at the regional level,and for enhancing the diversity of the un-derstory vegetation to improve the productivity of poplar plantations.