Impact of the origin of sites planted with hybrid poplar on plant community composition and diversity

Intensively managed fast-growing tree plantations may affect plant diversity, and we have little knowledge on how it is affected by site origin in order to better orientate site selection for their establishment. The aim of this study was thus to determine the impact of site origin on plant diversity in intensively managed hybrid poplar plantations. We investigated vascular and non-vascular plant communities within fast growing hybrid poplar plantations (PEH) established on abandoned agricultural lands (AAL) with herbaceous or shrubby vegetation, and on previously forested lands, and compared them to adjoining non-afforested surrounding sites. Our results show that PEH plantations established on herbaceous and shrubby AALs had similar or higher plant diversity even though they contained no forest species after 15 years. When established on previously forested lands, PEH plantations favored the establishment of ruderal species compared to their non-reforested equivalents, but plant diversity and richness tended to decrease following plantation establishment. Thus, if site selection is made to preserve or increase plant diversity, abandoned agricultural lands should preferentially be chosen rather than previously forested sites to install intensively managed hybrid poplar plantations.