Rapid Characterisation of Vegetation Structure to Predict Refugia and Climate Change Impacts across a Global Biodiversity Hotspot

Abstract

Identification of refugia is an increasingly important adaptation strategy in conservation planning under rapid anthropogenic climate change. Granite outcrops (GOs) provide extraordinary diversity, including a wide range of taxa, vegetation types and habitats in the Southwest Australian Floristic Region (SWAFR). However, poor characterization of GOs limits the capacity of conservation planning for refugia under climate change. A novel means for the rapid identification of potential refugia is presented, based on the assessment of local-scale environment and vegetation structure in a wider region. This approach was tested on GOs across the SWAFR. Airborne discrete return Light Detection And Ranging (LiDAR) data and Red Green and Blue (RGB) imagery were acquired. Vertical vegetation profiles were used to derive 54 structural classes. Structural vegetation types were described in three areas for supervised classification of a further 13 GOs across the region. Habitat descriptions based on 494 vegetation plots on and around these GOs were used to quantify relationships between environmental variables, ground cover and canopy height. The vegetation surrounding GOs is strongly related to structural vegetation types (Kappa = 0.8) and to its spatial context. Water gaining sites around GOs are characterized by taller and denser vegetation in all areas. The strong relationship between rainfall, soil-depth, and vegetation structure (R2 of 0.8–0.9) allowed comparisons of vegetation structure between current and future climate. Significant shifts in vegetation structural types were predicted and mapped for future climates. Water gaining areas below granite outcrops were identified as important putative refugia. A reduction in rainfall may be offset by the occurrence of deeper soil elsewhere on the outcrop. However, climate change interactions with fire and water table declines may render our conclusions conservative. The LiDAR-based mapping approach presented enables the integration of site-based biotic assessment with structural vegetation types for the rapid delineation and prioritization of key refugia.

Biodiversity hotspots and Ocbil theory

“…Remote sensing to map Ocbils is just beginning in detail (e.g., Schut et al 2014). Gairola et al (2013) highlighted the merits of using remote sensing as a tool to test aspects of Ocbil theory.…”

Large- and small-scale environmental factors drive distributions of cool-adapted plants in karstic microrefugia

“…Resource-gaining sites are also sometimes considered refugia (Schut et al, 2014). The doline bottoms are such resourcegaining sites, receiving more nutrients and moisture (B atori et al, 2009, 2011) and are hence potential microrefugia for a variety of functional groups, in addition to cool-adapted species.…”

Detecting microrefugia in semi-arid landscapes from remotely sensed vegetation dynamics

“…For example, there is interest in directly detecting refugial microclimates using thermal remote sensing, although this is challenged by the complex relationships between land surface temperature detected by remote sensors and air temperatures (Pepin et al, 2016). Alternatively, LiDAR data have the potential to indicate microrefugia by characterizing vegetation structures (Frey et al, 2016;Lenoir et al, 2017) or small topographic features (Lenoir et al, 2017) that buffer microclimates, or by detecting the relict vegetation communities occurring within microrefugia (Schut et al, 2014).…”

“…Finally, the most prevalent guideline about the occurrence of microrefugia in southwestern Australia is that they are associated with granite outcrops. Because of the very low infiltration of exposed granite, runoff from granite outcrops provides water subsidies to their surroundings, influencing vegetation composition and structure (Schut et al, 2014) and providing valuable resources to wildlife (Withers, 2000). Granite outcrops have also been used as water resources by aboriginal peoples (Bindon, 1997) and western settlers (Laing and Hauck, 1997).…”