Université Laval
Ph.D. candidate
Supervisor: Monique Poulin
Anne Vanasse, Université Laval
Start: 2012-01-01
End: 2015-10-04

Project

Restoration of riparian plant communities by tree planting in agricultural landscapes
Tree planting is frequently conducted in riparian zones to restore the ecological services of these ecotones widely degraded by agricultural intensification. Nevertheless, little is known about the response of riparian plant communities to tree planting. My Ph.D. aimed to identify some important recolonization mechanisms of riparian plant communities after tree planting in agricultural landscapes. Accordingly, four main research questions were raised: 1) does agricultural intensification reduce the establishment success of planted trees?; 2) does tree planting induce a plant succession leading to the re-establishment of plant communities characteristic of natural riparian forests?; 3) which spatial processes and ecological mechanisms structure plant diversity in riparian zones?; 4) do light availability, competition and soil conditions act as ecological filters limiting the recolonization of forest herbs? The increase in cultivation frequency of annual crops in the agricultural field adjacent to riparian zone reduced the survival and growth of planted trees, thereby demonstrating the detrimental impact of agricultural intensification on the establishment success of planted trees. However, trees induced a pattern of plant succession leading to the re-establishment of a vegetation structure, an abundance of ecological groups and a species composition characteristic of natural riparian forests. Furthermore, this type of plant succession corresponded to a model of threshold dynamics in which shade-tolerant species outcompeted light-demanding species after an ecological threshold related to light availability had been crossed. Upstream to downstream spatial processes along rivers, predominantly contributed to the plant composition of riparian zones, more so than bidirectional spatial processes overland or along rivers. These upstream-downstream processes were mostly linked to the traits of plant seeds. In other words, hydrochory was highlighted as a key watershed-scale process driving riparian plant diversity. Finally, the recolonization of two of the three forest herbs transplanted in riparian zones was reduced either by low shade levels, competition or agricultural soil. These scientific discoveries deepen our understanding of the functioning of riparian plant communities in agricultural landscapes, and promote more successful restoration of riparian zones.

Keywords

riparian communities, plant biodiversity, agricultural intensification, ecological restoration, plant succession, ecological filters, functional traits, soil seed banks

Publications

1- Vegetation Response to Control of Invasive Tamarix in Southwestern US Rivers: A Collaborative Study Including 416 Sites
González, Eduardo, Anna A Sher, Robert M Anderson, Robin F Bay, Daniel W Bean, Gabriel J Bissonnete, Bérenger Bourgeois, David J Cooper, Kara Dohrenwend, Kim D Eichhorst, Hisham El Waer, Deborah K Kennard, Rebecca Harms-Weissinger, Annie L Henry, Lori J Makarick, Steven M Ostoja, Lindsay V Reynolds, W Wright Robinson, Patrick B Shafroth
2017 Ecological Applications

2- Divergence between riparian seed banks and standing vegetation increases along successional trajectories
Bourgeois, Bérenger, Céline Boutin, Anne Vanasse, Monique Poulin
2017 Journal of Vegetation Science

3- Effects of competition, shade and soil conditions on the recolonization of three forest herbs in tree-planted riparian zones
Bourgeois, Bérenger, Anne Vanasse, Monique Poulin,
2016 Applied Vegetation Science

4- Spatial processes structuring riparian plant communities in agroecosystems: implications for restoration
Bourgeois, Bérenger, Eduardo González, Anne Vanasse, Isabelle Aubin, Monique Poulin
2016 Ecological Applications

5- Threshold dynamics in plant succession after tree planting in agricultural riparian zones
Bourgeois, Bérenger, Anne Vanasse, Eduardo González, Roxane Andersen, Monique Poulin
2016 Journal of Applied Ecology

6- Trade-Offs in Seed Dispersal Strategies Across Riparian Trees: The How Matters as Much as the When
González, E., B. Bourgeois, A. Masip, A. A. Sher
2015 River Research and Applications

7- Establishing a moss cover inhibits the germination of Typha latifolia, an invasive species, in restored peatlands
Bourgeois, Bérenger, Sandrine Hugron, Monique Poulin
2012 Aquatic Botany

8- Establishment success of trees planted in riparian buffer zones along an agricultural intensification gradient
Bourgeois, B., A. Vanasse, D. Rivest, M. Poulin
2016 Agriculture, Ecosystems & Environment

9- Integrative conservation of riparian zones
González, Eduardo, María R. Felipe-Lucia, Bérenger Bourgeois, Bruno Boz, Christer Nilsson, Grant Palmer, Anna A. Sher
2016 Biological Conservation

10- Spatial modeling improves understanding patterns of invasive species defoliation by a biocontrol herbivore
Henry, Annie L., Eduardo González, W. Wright Robinson, Bérenger Bourgeois, Anna A. Sher
2018 Biological Invasions