A plant traits approach to managing legacy species during restoration transitions in temperate eucalypt woodlands

Abstract

Degraded communities often contain a subset of the species that comprised the predisturbance community. These represent an important legacy of the predisturbance state, yet restoration treatments may be detrimental to them. This study examined the potential of leaf traits and life form to predict whether restoration treatments can maintain legacy swards of Austrostipa bigeniculata (hereafter Austrostipa) while controlling exotic annuals in temperate eucalypt woodlands. Treatments included carbon addition to reduce soil nitrate, both with and without burning or pulse grazing to deplete exotic seed pools. We compared leaf traits of Austrostipa with a native grass (Themeda triandra) known to be advantaged, and 8 exotic annual species known to be disadvantaged by these treatments. Leaf traits indicated potentially greater negative impacts of carbon addition on exotic annuals compared to Austrostipa, and on Austrostipa compared to Themeda, suggesting a net restoration benefit. Similarly, burning or pulse grazing is expected to have little negative impact on perennial resprouting grasses (hemicryptophytes; Austrostipa and Themeda) compared with annual exotics (therophytes) with short-lived seed banks. Treatment responses were largely consistent with predictions: treatments that significantly reduced exotic annuals had no net disadvantage to Austrostipa swards despite significant reductions in Austrostipa seedling growth with carbon addition. Indeed by Year 3, Austrostipa mortality in untreated plots led to 46% lower Austrostipa abundance than in treated plots at one site, potentially due to litter build-up or other mechanisms. We conclude that plant traits provide a useful framework for designing restoration transitions that retain native legacy species while controlling exotics.

Functional diversity is more sensitive to biotic filters than phylogenetic diversity during community assembly

“…, Laughlin , Cole et al. ). Moreover, species with desired functional traits may be more phylogenetically related than species with less desirable functional traits, which could assist in the selection of species to use for restoration (Hipp et al.…”

“…Consequently, assessing the functional traits of dominant and subordinate species in restorations could help practitioners develop appropriate management strategies to promote native species (Sandel et al 2011, Laughlin 2014, Cole et al 2016. Moreover, species with desired functional traits may be more phylogenetically related than species with less desirable functional traits, which could assist in the selection of species to use for restoration .…”

Trajectories of floristic change in grassland: landscape, land use legacy and seasonal conditions overshadow restoration actions

“…; Cole et al. ). Our conclusions need to be treated with some caution as the botanical sampling only recorded a maximum of six species per quadrat.…”

Establishment of native grasses and their impact on exotic annuals in degraded box gum woodlands

“…However, an earlier study observed similarly poor recruitment of Poa in C4 Bothriochloa swards, as well as high recruitment of C4 Themeda in these C4 swards . Over the 4 years, Austrostipa species grew vigorously and increased in basal area and abundance in all treatments (Cole et al 2016a). seed predation, relatively small seed size in Poa and Rytidosperma), and our results highlight the need for better methods for reestablishing these C3 grasses in restored woodlands.…”

“…This can be achieved by burning prior to seed maturation. Importantly, strategic burning and grazing can also promote the health, vigour and competitiveness of native grass swards (Menke 1992;Zedler 2007;Cole et al 2016a). Similar effects can also be achieved by strategic grazing, although this is less well studied (Doll et al 2011;Cole et al 2016b).…”