How Does Restoration of Native Canopy Affect Understory Vegetation Composition? Evidence from Riparian Communities of the Hunter Valley Australia

Abstract

Restoration of native vegetation often focuses on the canopy layer species, with the assumption that regeneration of the understory elements will occur as a consequence. The goal of this study was to assess the influence of canopy restoration on the composition and abundance of understory plant species assemblages along riparian margins in the Hunter Valley, NSW, Australia. We compared the floristic composition (richness, abundance, and diversity) of understory species between nonrevegetated (open) and canopy revegetated plots across five sites. A number of other factors that may also influence understory vegetation, including soil nutrients, proximity to main channel, and light availability, were also measured. We found that sites where the canopy had been restored had lower exotic species richness and abundance, as well as higher native species cover, but not native species richness, compared with open sites. Multivariate analysis of plots based on plant community composition showed that revegetated sites were associated with lower total species diversity, light availability, and exotic cover. This study has found that the restoration of the canopy layer does result in lower exotic species richness and cover, and higher native species cover and diversity in the understory, a desirable restoration outcome. Our results provide evidence that restoration of native canopy species may facilitate restoration of native understory species; however, other interventions to increase native species richness of the understory should also be considered as part of management practice.

Understanding and predicting the combined effects of climate change and land‐use change on freshwater macroinvertebrates and fish

“…Closed canopy revegetation is also recommended for introducing microclimatic changes to increase native species richness while decreasing exotic species numbers (Harris et al . ; Lee et al . ).…”

“…Riparian buffer widths of between 30 and 200 m are generally recommended, dependent on stream size, land-use intensity and management objective (Hansen et al 2010;Richardson, Naiman & Bisson 2012). Closed canopy revegetation is also recommended for introducing microclimatic changes to increase native species richness while decreasing exotic species numbers (Harris et al 2012;Lee et al 2012). In a more urbanized and warmer world, however, alternative best management practices for riparian restoration may be necessary as these guidelines may be insufficient for mitigating future climate and land-use change impacts.…”

Reclamation strategies for mined forest soils and overstorey drive understorey vegetation

“…Because understorey vegetation accounts for a large part of forest overall biodiversity and contributes greatly to ecosystem functioning (Gilliam, ; Hart & Chen, ; Nilsson & Wardle, ; Vockenhuber et al., ; Zhang, Chen, & Taylor, ), diverse and productive understorey vegetation is an important determinant of restoration success (Koch, ; Macdonald et al., ). In many instances, however, understorey vegetation is restored passively (Aerts & Honnay, ; Harris, Leishman, Fryirs, & Kyle, ). That is, development of understorey vegetation following the restoration of degraded forested ecosystems may depend on strategies aimed at improving abiotic site conditions and overstorey development (Palmer et al., ).…”

“…That is, development of understorey vegetation following the restoration of degraded forested ecosystems may depend on strategies aimed at improving abiotic site conditions and overstorey development (Palmer et al, 1997). This approach is common in diversified contexts ranging from severely degraded sites such as Bauxite mines (Koch, 2007), oil sands mines (Macdonald et al, 2015) and granite quarries (Zhang, Zhuang, & Chu, 2013) to mildly degraded riparian vegetation (Harris et al, 2012).…”

Spatial processes structuring riparian plant communities in agroecosystems: implications for restoration

“…, Harris et al. ). Once riparian zones have been physically reconfigured, plant species are assumed to passively recolonize (field of dreams hypothesis, “if you build it, they will come”; Palmer et al.…”