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.
Highlights
Considerable changes in the distribution and ecology of species and ecosystems are likely to be ongoing over the coming decades in response to anthropogenic climate change [1,2,3]
Airborne Light Detection And Ranging (LiDAR) data and Red, Green and Blue (RGB) imagery were acquired by AAM Pty Ltd (Perth, Australia) from flights covering the areas around 28 targeted Granite outcrops (GOs) across the Southwest Australian Floristic Region (SWAFR) rainfall-gradient from mesic to low rainfall environments (Fig. 1)
The canopy height of vegetation in plots on or near GOs responded more strongly to precipitation than to ground coverage, with annual precipitation ranging between 314–1208 mm yr21 for the GOs included in this study (Table 1)
Summary
Considerable changes in the distribution and ecology of species and ecosystems are likely to be ongoing over the coming decades in response to anthropogenic climate change [1,2,3]. The current reliance on species distribution models (SDMs) is most often applied at coarse spatial scales, but refugia may occur at relatively fine spatial scales [8,9,10]. [12,13]), and coarse SDMs predict large impacts on species distributions [14,15]. None of these models take into account fine scale environmental heterogeneity, and as a consequence are unable to identify refugia at finer scales - the scales likely to enable local persistence under predicted changes, though see [16,17]
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