Effects of competition, shade and soil conditions on the recolonization of three forest herbs in tree-planted riparian zones

Authors: Bourgeois, BérengerVanasse, AnnePoulin, Monique
Abstract: Abstract Questions: In mesic forests, ecological filters due to past agricultural land-use reduce forest herbs recolonization. Is the recruitment of such species also limited in tree-planted riparian zones, by local filters such as competition, shade level and soil conditions? Location: Two agricultural watersheds, southeastern Québec, Canada. Methods: Three herbs characteristic of natural riparian forests were selected for this study: one graminoid, Glyceria striata, and two ferns, Matteuccia struthiopteris and Onoclea sensibilis. Effects of shade level (75% versus 50%) and soil type (forest versus agricultural soil) on seedling emergence were evaluated in a seed-sowing greenhouse experiment. In a two-year transplant field experiment, seedling and sporophyte establishment was monitored in five natural riparian forests and five tree-planted post-agricultural riparian zones on microsites with understory vegetation kept intact or cleared and on forest or agricultural soils. Using a priori contrasts, we assessed the influence of habitat type (natural riparian forests or tree-planted riparian zones), competition and post-agricultural soil type on transplant survival and growth. Results: Seedling emergence tended to be higher on forest soils for G. striata while sporophyte emergence increased under 75% shade for M. struthiopteris. Transplanted seedlings and sporophytes of the three species survived and grew as well in tree-planted riparian zones as in natural riparian forests. In tree-planted riparian zones however, competing understory vegetation reduced the survival and growth of G. striata and agricultural soil reduced the growth of M. struthiopteris. For O. sensibilis, only sporophyte survival was reduced by competition in tree-planted riparian zones. Conclusions: Planting trees in post-agricultural riparian zones fosters an establishment of forest herbs similar than those observed in natural riparian forests. Additional environmental filters specific to tree-planted riparian zones however offset the positive influence of trees and limit the recolonization of the three studied species. Considering the partial restoration success of establishment niches by tree planting, controlling spontaneous vegetation after tree planting is advised when conceivable and cost-effective to promote the recolonization of environmentally-limited forest herbs. Long-term transplant experiments should be more largely conducted to identify the ecological filters that reduce plant recolonization, and thereby design the most effective restoration strategies.
Document Type: Article de recherche
Issue Date: 25 July 2016
Open Access Date: 25 July 2017
Document version: AM
Permalink: http://hdl.handle.net/20.500.11794/3168
This document was published in: Applied Vegetation Science, Vol.19 (4), 679–688 (2016)
https://doi.org/10.1111/avsc.12246
Opulus Press
Alternative version: 10.1111/avsc.12246
Collection:Articles publiés dans des revues avec comité de lecture

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