Ecosystems may be best equipped to support biodiversity and function resiliently when they have developed slowly and spontaneously through succession. Environmental managers within extractive industries seek similar properties for sites undergoing rehabilitation, but are under regulatory pressure to achieve results faster than nature normally provides. Through collaboration with an aggregate producer already engaged in quarry expansion, rehabilitation and offsetting, we took advantage of a unique opportunity to test the extent to which ecological properties of late-successional ecosystems may be produced at younger sites by relocating slow-forming ecosystem structures from the former to the latter and replicating habitat conditions required by living components of the structures. We experimentally excavated the topmost layer of forest floor (“living mulch”, e.g. litter, topsoil, propagule banks, biotic networks) from mature maple forest in the expanding quarry and relocated it immediately to large plots within nearby sites spanning a successional gradient typical of the human-dominated landscape (a depleted gravel pit; recent and older afforestations; mature forest contiguous with the donor site but outside the impact zone). We superimposed habitat-mimicry applications to subsections of each plot, including woody debris from the donor forest, planting of living shade-providers (dogwood saplings), and installation of artificial shade-providers (shade-cloth shelters).
Results/Conclusions
Given that living mulch relocation was carried out less than two years ago, responses measured so far provide insight into the very earliest responses of ecosystems to relocated materials; several more years of observation are required to answer the questions fully. Preliminary comparisons among plant communities indicate, however, that understorey herb species associated with mature forest are significantly more likely to occur at earlier-successional sites in plots treated with living mulch than in adjacent untreated areas, and this effect is strongest at the oldest afforested site. The addition of woody debris and artificial shading is also positively associated with plant communities that are more similar to the donor forest than to untreated areas of the younger sites. Planted dogwood sapling exhibited poor survival and had minimal impact on other vegetation. Extensive investigation into responses at multiple levels, from soil seed banks, microbial and faunal communities to trees, habitat features and thermodynamic properties of ecosystems is currently underway, and will undoubtedly contribute to a more complete understanding of the potential for accelerating succession in restoration.