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Microclimate reveals the true thermal niche of forest plant species

By: Stef Haesen and Koenraad Van Meerbeek

Species distribution models have become the go-to tool for forecasting how changes in environmental conditions affect species' geographical distribution. Most of these models are correlative in nature, employing statistical or machine-learning methods to uncover relationships between species occurrences and the environment they inhabit. The customary practice involves incorporating a standard set of bioclimatic variables, typically at a spatial resolution of 1 × 1 km². However, these macroclimatic data, derived through interpolating weather station data, essentially reflect the free-air temperature conditions in open ecosystems. While these data effectively capture changes in free-air temperatures, it is essential to acknowledge that these macroclimate-based species distribution models may introduce bias due to the simplified assumptions these models make regarding the causal relationship between spatially-averaged climatic predictors and the fitness of individual organisms.


“Constructing these high-resolution, microclimate-based species distribution models was made possible by leveraging the high-performance computing infrastructure provided by the VSC.”

To address this concern, researchers from the sGlobe lab, which is part of KU Leuven's division of Forest, Nature, and Landscape, integrated novel microclimatic data into their species distribution models. In this way, they evaluated the enhancements these data brought in terms of the performance and outcomes of species distribution models, particularly regarding thermal response curves and the geographical ranges of European forest plant species. Constructing these high-resolution, microclimate-based species distribution models was made possible by leveraging the high-performance computing infrastructure provided by the VSC.



Figure 1: (a) Distribution of Paris quadrifolia across the European continent, where a high suitability indicates areas where the species is able to find suitable environmental conditions for survival. (b) The species occurs in warmer places (or refugia) at the northern edge of its distribution, where its survival is limited by low minimum temperatures. (c) The species occurs in cooler places (or refugia) at the southern edge of its distribution, where its survival is limited by high maximum temperatures.


The study's findings demonstrate that species distribution models based on microclimate significantly outperform their macroclimate-based counterparts. They also reveal the introduction of a systematic bias in thermal response curves when relying on macroclimate-based models. Furthermore, the inclusion of microclimate data in these models enables the identification of micro-refugia within the landscape - areas where species can find a stable and suitable climate amid unfavorable, changing macroclimatic conditions. This newfound information holds particular significance in the realm of conservation science, as microclimate-based species distribution models prove to be valuable tools for gaining insights into biodiversity conservation in the face of climate change. This is especially pertinent given the increasing policy and management emphasis on conserving refugia worldwide.


 

Read the full publication of this article in Ecology Letters

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