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

Abstract

(in press). Detecting microrefugia in semi-arid landscapes from remotely sensed vegetation dynamics. Remote Sensing of Environment. Accepted 4 August 2017. DOI:https: //doi.org/10.1016/j.rse.2017.08.005 Disclaimer:The PDF document is a copy of the final version of this manuscript that was subsequently accepted by the journal for publication. The paper has been through peer review, but it has not been subject to any additional copy-editing or journal specific formatting (so will look different from the final version of record, which may be accessed following the DOI above depending on your access situation). 2 AbstractMicrorefugia are sites with stable, high quality habitat within landscapes characterized by dynamic environmental conditions driven by climate variability or ecological disturbances. There is considerable interest in the potential of microrefugia to provide climate change resilience to landscapes and to biodiversity conservation. Although attractive conceptually, there is yet little guidance on how to identify climate change microrefugia in order to study and protect them, and the data required to do so are often lacking. This study demonstrates how time series remote sensing, using all available Landsat images of a study area, can be used to directly detect microrefugia maintained by water subsidies in a semi-arid landscape in southwest Western Australia.Microrefugia were identified as pixels with abundant vegetation and consistent vegetation dynamics between wet and dry years. At every pixel, a harmonic model was fit to the intra-annual time series of vegetation index values compiled from the wettest years in the Landsat-5 Thematic Mapper (TM) archive. This model was then used to predict the phenological cycle of the driest years at that pixel. Candidate microrefugia were defined to be those pixels with (1) high vegetation activity in dry years and (2) highly predictable phenologies that are consistent regardless of the weather conditions experienced in a given year. Spatial relationships between candidate microrefugia and landscape features associated with elevated moisture availability (thought to drive climate microrefugia in these semi-arid landscapes) were assessed. The candidate microrefugia show great promise. Evaluations against high-resolution imagery reveal that candidate microrefugia most likely buffer against drought, although refugia from other disturbances, especially fire, were also detected. In contrast, spatial proxies of the physical features expected to maintain microrefugia failed to adequately represent the distribution of microrefugia across the landscape, likely due to data quality and the heterogeneity of microrefugia. Direct detection of microrefugia with Earth observation data is a promising solution in data limited regions. Landsat time series analyses are well suited to this application as they can characterize both the habitat quality and stability aspects of microrefugia.

Hiding from the climate: Characterizing microrefugia for boreal forest understory species

“…Daytime microclimates in the summer are often strongly related to forest canopy cover, which not only buffers high maximum temperatures but also low minimum (night‐time) temperatures, suggesting that the populations occupying sites with lower maximum temperatures in denser forests also experience more stable climates. Climate or habitat stability has been suggested to be one of the core features of refugia (Andrew & Warrener, ; Ashcroft et al, ; Keppel et al, ; Morelli et al, ). Since a continuous forest cover buffers large temperature fluctuations, boreal rear‐edge populations may actually depend on low levels of disturbances in terms of management activities like thinning or clearing.…”

“…Climate or habitat stability has been suggested to be one of the core features of refugia (Andrew & Warrener, 2017;Ashcroft et al, 2012;Morelli et al, 2016). also provide valuable information about where to find microrefugia for northern species.…”

“…The (micro)refugia concept has been studied and discussed around the globe, across taxa and ecosystems (Andrew & Warrener, 2017;Hannah et al, 2014;Kiedrzyński, Zielińska, Kiedrzyńska, & Rewicz, 2017;Niskanen et al, 2016;Osman et al, 2018;Scheffers, Edwards, Diesmos, Williams, & Evans, 2014;Schut et al, 2014;Terribile et al, 2012) and a considerable amount of speculation and expectation has been expressed on the carrying role of microrefugia to slow down ongoing climate-driven loss of species and genetic biodiversity (Abeli et al, 2018;Hampe & Petit, 2005;Keppel et al, 2012;Provan & Maggs, 2011). Much of the work has been theoretical, and more empirical studies, like ours, are needed to understand the characteristics of microrefugia, to make realistic predictions and to give adequate advice to conservation and management.…”

Remote sensing of phenology: Towards the comprehensive indicators of plant community dynamics from species to regional scales

“…Donoso et al, 2016; Leong & Roderick, 2015; Olliff‐Yang et al, 2020). Regional asynchronies in phenometrics can also identify microrefugia, i.e., stable regions of quality habitat and unique microclimates that help buffer the effects of climate in dynamic landscapes and promote species persistence (Andrew & Warrener, 2017; Bobrowski et al, 2018).…”

Detecting phenological changes in plant functional types over West African savannah dominated landscape

“…The use of remote sensing data (e.g. normalized difference vegetation index (NDVI)) to monitor disturbance or retrospectively identify the effects of environmental variables on phenological variability of PFTs is receiving significant attention (Jacques et al 2014;Andrew and Warrener 2017;Ilangakoon et al 2018;Cao et al 2018;Yang et al 2018;Nguyen et al 2018;Woodcock et al 2019).…”