Limiting processes for perennial plant reintroduction to restore dry grasslands

Abstract

International audienceIn restored grasslands of southern Europe, perennial plants remain highly underrepresented compared with the reference ecosystems. We tested various treatments to reintroduce common perennial plant species (Brachypodium retusum, Poaceae, and Thymus vulgaris, Lamiaceae), which are usually not or poorly reintroduced via soil and hay transfer. Treatments included microenvironmental manipulations (rock cover and plant interactions) and two grazing intensities. Target perennial species were transplanted in 2002 in the reference grassland ecosystem (intact grassland area used as a control) and in two abandoned fields. Survival was assessed in June 2003 and June 2004. Target species shoot and root biomass were measured in June 2004. Grazing greatly reduced the survival and biomass of both target species and its effects were reinforced by summer drought: plants that did not establish well enough during the autumn and spring did not survive summer. The restored rock cover had a mild positive effect, particularly on B. retusum. There were no negative or positive plant neighbor interactions in the steppe, while there was competition in both abandoned fields. Competition was particularly intense in the abandoned melon field, composed of a dense sward of annual grasses (Bromus sp.). In order to reintroduce perennial species to dry grasslands, the ideal combination of treatments is to exclude or reduce grazing during the first year to allow seedlings to establish and to recreate adequate microenvironmental conditions. Reducing competition from arable weeds may help but is not essential in such dry grasslands

Recovery of Mediterranean steppe vegetation after cultivation: Legacy effects on plant composition, soil properties and functional traits

“…Our results show that the dominant perennial steppe grass B. retusum has so far been unable to re‐establish on the fallow land; this is not only directly explained by habitat change due to deep soil ploughing and high fertilization, but also indirectly by competition with the common fallow‐land species (Buisson, Corcket, & Dutoit, ; Coiffait, Buisson, & Dutoit, ). Moreover, dispersal limitation and the mainly vegetative reproduction of this steppe grass (Dureau & Bonnefon, ) have prevented successful re‐establishment.…”

“…A high percentage of bare ground is characteristic of fallow land, where stones were removed for cultivation purposes (Buisson & Dutoit, ). However, stones create important micro‐habitats for the typical steppe vegetation: they preserve humidity, serve as shelter and create safe sites for rhizomes of e.g., B. retusum (Bourrelly, ; Buisson et al., ; Caturla, Raventós, Guàrdia, & Vallejo, ).…”

“…In addition to monitoring natural recovery over the long term, new grazing systems could be introduced to hasten recovery or more active restoration implemented by seeding nurse or structuring species (e.g., B. retusum ; Coiffait et al., ; Buisson et al., ). Future analyses could cover an extended set of species and include further traits to better elucidate assembly processes.…”

Adaptive differentiation among populations of the Mediterranean dry grassland species Brachypodium retusum: The role of soil conditions, grazing, and humidity

“…The latter habitat is also characterized by stones (pebbles and cobbles) shaped by the former rivers. These stones were found to favor growth and survival of B. retusum because rhizomes and roots can grow underneath and thus benefit from higher soil moisture during the hot and dry Mediterranean summer (Buisson et al, 2015). Apart from soil characteristics and stone cover, these two habitats show also large differences in soil moisture and grazing intensity.…”

The effects of management on vegetation trajectories during the early‐stage restoration of previously arable land after hay transfer

“…The restoration of grasslands from previously arable lands has been the subject of numerous studies focused on the ecological mechanisms underlying restoration successes or failures (Muller, Dutoit, Alard, & Grévilliot, 1998;Pywell et al, 2002;Török, Vida, Deák, Lengyel, & Tóthmérész, 2011). Experimental approaches have considerably strengthened the conceptual bases of restoration ecology by testing hypotheses from the field of community ecology (Wainwright et al, 2018) and exploring key processes in restoration operations such as biotic interactions or disturbances (Buisson, Corcket, & Dutoit, 2015). One of the principal processes that affects restoration success is the limited dispersal and recruitment of plant seeds in a context of habitat fragmentation (Pywell et al, 2002;Woodcock, McDonald, & Pywell, 2011), particularly after a long history of intensive agricultural practices that has reduced the number of floodplain grassland species seeds stored in the seed bank (Bischoff, Warthemann, & Klotz, 2009;Hedberg & Kotowski, 2010;Scotton, 2016).…”