Recruitment limitation of native species in invaded coastal dune communities

Abstract

Recruitment limitation may limit the ability of sites to regenerate after disturbances such as weed invasion and weed management. We investigated seed bank constraints and dispersal limitation in coastal dune communities on the east coast of Australia. The ability of sites to regenerate naturally following weed removal was assessed in coastal dune communities invaded by the invasive alien, bitou bush (Chrysanthemoides monilifera subsp. rotundata). To investigate recruitment limitation, seed banks and vegetation of invaded, native, intensively managed (selective application of herbicide and some revegetation) and extensively managed (large-scale, non-selective herbicide application) sites were compared. We investigated the dispersal mechanisms of species in the seed bank and vegetation to determine if communities might be dispersal-limited, i.e. contain significant numbers of species with only shortdistance dispersal capabilities. Species richness and composition of soil seed banks differed from the vegetation in foredunes and hinddunes. Invasion depleted seed banks further. About half of the species had short-distance dispersal mechanisms indicating the potential for dispersal limitation. Secondary weed invasion following management was evident although alien species occurred in both seed banks and vegetation. Our results indicated that coastal dune communities suffer recruitment limitation. Native, managed and invaded dune communities appear to be both seed bank and dispersal-limited although management and invasion exacerbates recruitment. Regeneration of coastal dune communities will require active reintroduction of species, particularly those with short-distance dispersal mechanisms.

Covariation in diaspore mass and dispersal patterns in threeMediterranean coastal dunes in southern Spain

“…Diaspore dispersal is restricted and controlled by vegetation density in the fixed dunes (Watkinson and Harper, 1978;French et al, 2011). The results obtained indicated that diaspore dispersal in the fixed M-oceanic and M-subtropical dunes has an interplay between restricted dispersion, mainly semachory, and more developed dispersal through vertebrate dispersal.…”

Invasive Phragmites australis management outcomes and native plant recovery are context dependent

“…Recruitment deficiencies may also be partly due to propagule limitation, which has led to poor native plant recruitment in many ecosystem restorations (French, Mason, & Sullivan, ; Kettenring & Galatowitsch, ). While some studies in tidal ecosystems have found diverse native seed banks under Phragmites (e.g., Hazelton, Downard, Kettenring, McCormick, & Whigham, ), the composition and densities may not match noninvaded areas and may be highly variable across sites.…”

Recovery of Foredune and Blowout Habitats in a Freshwater Dune Following Removal of Invasive Austrian Pine (Pinus nigra)

“…Third, the two dune habitats we studied are species poor by definition, and the dominant species were already present in the habitats. In systems with higher species diversity, such as the bitou bush‐invaded coastal hind dune communities of New South Wales, Australia, recruitment limitation and the loss of seed sources following invasion by a woody invader may be a problem (Mason & French ; French et al ).

The key to successful recovery of habitats with high natural disturbance is to restore native ecosystem processes, such as wind.

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