No abstract

Wetlands are increasingly valuable under climate change in terms of their ecological functions, ecosystem services, and biodiversity. Simultaneously, wetlands are hotspots for anthropogenic activity due to their high soil fertility and water supply, and have been subject to significant modification, degradation, and staggering losses. With climate change having increasing impacts on ecosystems globally, the need for wetland restoration is rapidly growing. Natural regeneration, whereby vegetation is allowed to regrow via propagules already present within the landscape, provides a cost-effective and large-scale approach to restoration for many, but not, all wetlands. This paper emphasises the importance of natural regeneration of wetland ecosystems as an effective restoration approach under climate change. We discuss drivers and barriers of natural regeneration of wetlands under climate change along with implications for management approaches. Drivers of wetland natural regeneration are depicted along with their interactions, displaying a range of abiotic and biotic factors that influence ecosystem change. Key adaption approaches to maintain and promote natural regeneration of wetlands under climate change include integrated land and water management, protecting and promoting key relevant biotic and abiotic processes within landscapes, and reconsidering current exotic species management strategies. Most importantly, however, natural regeneration should be recognised as an important and viable restoration approach under climate change in order to meet restoration demand and promote landscape resilience to changing conditions.

Revegetating abandoned agricultural lands is vital to restoring critical ecological functions and services. Natural regeneration, whereby vegetation regrows via the seeds already present within the landscape, has shown to be an effective approach to restoring large agricultural areas, although more research is required to understand the regenerative capacity of the various seed sources. Here, we investigate the regenerative capacity of old‐fields of semi‐arid floodplains of eastern Australia in a year‐long seedling emergence experiment. We examined the germinable seed banks from three potential propagule sources (soil, leaf litter, and animal scats) collected across 24 field sites, comprising 12 old‐fields and 12 adjacent remnant vegetation patches, distributed across four regions. Soil seed banks stored the most germinable species of the three seed bank types, although these were dominated largely by annual herbaceous species. High abundances of seedlings emerged from scat samples, indicating that native animals, such as kangaroos and emus, play a role in transporting seeds in these landscapes. Finally, leaf litter stored the most germinable propagules of woody species, therefore, representing a vital mechanism for woody vegetation regeneration. There were few differences in emerging seedling assemblages in terms of species richness, abundance or composition between seed banks of old‐fields and adjacent remnant vegetation, suggesting that old‐field seed banks have a high level of resilience. Our findings suggest that these seed banks can make an important contribution to natural regeneration of these old‐fields, but mainly with respect to understory and midstory species, with overstory tree species mostly absent from these seed sources.

In semi-arid landscapes, water regimes play a critical role in shaping patterns of vegetation regeneration. In riparian and floodplain habitats, however, the importance of flooding versus rainfall is poorly established for many species and habitats. Here, we present the results of a field experiment designed to investigate the establishment responses of both Eucalyptus camaldulensis (river red gum) seedings and understory vegetation to different hydrological conditions within two contrasting habitat types. We ran a field experiment in these habitats along the Condamine River in the northern Murray-Darling Basin in eastern inland Australia. We imposed flooding, rainfall, and drought treatments on 180 seedlings of E. camaldulensis and extant understory vegetation in 18 experimental plots to examine seedling survival and the establishment and dynamics of understory plant assemblages over nine months. Although there was very high seedling mortality overall, our results were consistent with findings from elsewhere in the Murray-Darling Basin indicating that flooding is a critical factor driving the survival of E. camaldulensis seedlings and the resilience of understory vegetation cover and diversity. Although the chance of seedling survival up until ten weeks was higher in the riparian habitat than in the floodplain old-field, the effect of habitat type was reduced under flooded conditions. Despite the low numbers of surviving E. camaldulensis seedlings, the value of a few successfully established trees on old-fields should not be underestimated, nor the potential effects of flooding on restoring the understory. This research highlights that rainfall is unlikely to provide sufficient watering in these habitats for vegetation regeneration.