title: Spatial processes structuring riparian plant communities in agroecosystems: implications for restoration.
abstract: The disruption of hydrological connectivity by human activities such as flood regulation or land-use changes strongly impacts riparian plant communities. However, landscape-scale processes have generally been neglected in riparian restoration projects as opposed to local conditions, even though such processes might largely influence community recovery. We surveyed plant composition of field edges and riverbanks in 51 riparian zones restored by tree planting (565 1-m2plots) within two agricultural watersheds in southeastern Québec, Canada. Once the effects of environmental variables (hydrology, soil, agriculture, landscape, restoration) were partialled out, three models of spatial autocorrelation based on Moran's eigenvector maps and asymmetric eigenvector maps were compared to quantify the pathways and direction of the spatial processes structuring riparian communities. The ecological mechanisms underlying predominant spatial processes were then assessed by regression trees linking species response to spatial gradients to seed and morphological traits. The structure of riparian communities was predominantly related to unidirectional spatial gradients from upstream to downstream along watercourses, which contributed more to species composition than bidirectional gradients along watercourses or overland. Plant traits selected by regression trees explained 22% of species response to unidirectional upstream-downstream gradients in field edges and 24% in riverbanks, and predominantly corresponded to seed traits rather than morphological traits of the adult plants. Our study showed that even in agriculturally open landscapes, water flow remains a major force structuring spatially riparian plant communities by filtering species according to their seed traits, thereby suggesting long-distance dispersal as a predominant process. Preserving hydrological connectivity at the watershed-scale and restoring riparian plant communities from upstream to downstream should be encouraged to improve the ecological integrity of rivers running through agricultural landscapes.
authors.affiliation: Département de Phytologie, Faculté des Sciences de l'Agriculture et de l'Alimentation, Université Laval, 2425 rue de l'agriculture, Québec, Québec, G1V 0A6, Canada. berenger.bourgeois.1@ulaval.ca.|Québec Centre for Biodiversity Science, Department of Biology, McGill University, Stewart Biology Building, 1205 Dr. Penfield Avenue, Montréal, Québec, H3A 1B1, Canada. berenger.bourgeois.1@ulaval.ca.
authors.forename: Bérenger
authors.initials: B
authors.lastname: Bourgeois
authors.affiliation: Department of Biological Sciences, University of Denver, F W Olin Hall, Room 102 2190, E Iliff Avenue, Denver, Colorado, 80208-9010, USA.|EcoLab, Institut National Polytechnique de Toulouse, Centre National de la Recherche Scientifique, Université Paul Sabatier, 118 route de Narbonne Bâtiment 4R1, Toulouse, Cedex 9, 31062, France.
authors.forename: Eduardo
authors.initials: E
authors.lastname: González
authors.affiliation: Département de Phytologie, Faculté des Sciences de l'Agriculture et de l'Alimentation, Université Laval, 2425 rue de l'agriculture, Québec, Québec, G1V 0A6, Canada.
authors.forename: Anne
authors.initials: A
authors.lastname: Vanasse
authors.affiliation: Natural Resources Canada, Canadian Forest Service, Great Lakes Forestry Centre, 1219 Queen St. East, Sault Ste. Marie, Ontario, P6A 2E5, Canada.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Aubin
authors.affiliation: Département de Phytologie, Faculté des Sciences de l'Agriculture et de l'Alimentation, Université Laval, 2425 rue de l'agriculture, Québec, Québec, G1V 0A6, Canada. monique.poulin@fsaa.ulaval.ca.|Québec Centre for Biodiversity Science, Department of Biology, McGill University, Stewart Biology Building, 1205 Dr. Penfield Avenue, Montréal, Québec, H3A 1B1, Canada. monique.poulin@fsaa.ulaval.ca.
authors.forename: Monique
authors.initials: M
authors.lastname: Poulin
mesh_terms: D000383:Agriculture; D059001:Aquatic Organisms / Q000502:physiology*; D003710:Demography; D017753:Ecosystem; D004784:Environmental Monitoring; D052918:Environmental Restoration and Remediation; D018521:Plant Physiological Phenomena; D010944:Plants / Q000145:classification*; D011792:Quebec; D045483:Rivers
keywords: agricultural landscapes; ecological restoration; eigenvector maps; hydrochory; plant traits; spatial autocorrelation; unidirectional vs. bidirectional spatial processes; watercourse vs. overland spatial processes