Aim
Niche‐based species distribution models (SDMs) have become a ubiquitous tool in ecology and biogeography. These models relate species occurrences with the environmental conditions found at these sites. Climatic variables are the most commonly used environmental data and are usually included in SDMs as averages of a reference period (30–50 years). In this study, we analyse the impact of including inter‐annual climatic variability on the estimation of species niches and predicted distributions when assessing plant demographic response to extreme climatic episodes.
Location Mediterranean basin, SE Iberian Peninsula.
Methods
We first characterized species niches with inter‐annual and average climate in the same environmental space. We then compare the respective capacities of climatic suitability obtained from averaged climate‐based and from inter‐annual variability‐based niches to explain population demographic responses to extreme drought. Furthermore, we assessed the relative increase in niche size when including climatic variability for a set of Mediterranean species exhibiting a wide range of distribution areas.
Results
We found that climatic suitability obtained from inter‐annual variability‐based niches showed higher explanatory capacity than average climate‐based suitability, especially for populations living in climatically marginal conditions, although both niches quantifications significantly explained species demographic responses. In addition, species with restricted distribution ranges increased relatively more their niche space when considering climatic variability, probably because in widely distributed species spatial variability compensates for temporal variability. Main conclusions
The common use of climatic averages when characterizing species niches could lead to underestimations of species distribution and misunderstanding of demographic behaviour, with implications for conservation plans derived from SDMs, for example, overestimations of species extinction risk under climate change, or underestimations of alien species invasion’ risk. We highlight that including climatic variability in niche modelling can be particularly important when dealing with species with restricted distribution and populations at the margin of their species niche.
The southeast Iberian Peninsula is the only place in the European Community where Tetraclinis articulata (Vahl) Masters populations are native. In this area, the optimal ecological niche for this species is occupied by Pinus halepensis (Miller). The increasing intensity of extreme drought events induced by climate change causes severe declines in pine forests, while providing expansion opportunities for established Tetraclinis populations. Within the framework of the LIFE-TETRACLINIS project, a study has been designed to simulate the pine forest decline effects on the population dynamics of this protected species. This work investigates the effects of decreasing competition on T. articulata specimens with limited reproductive activity. To induce the reproductive activity of these specimens through increasing the availability of light, the surrounding pines were removed within a 15 m radius. Increased light availability was modelled using “Light Detection And Ranging” (LiDAR) data, and changes in the main reproductive parameters were registered throughout the study period. A significant increase in the reproductive population was achieved, as well as the cones produced per specimen and the recruitment. Findings obtained are promising for the habitat management in continental Europe and enhancing this forest system’s resilience to extreme drought events and climate change.
The latest reports from the European Commission warn of the need to improve the conservation status of its forest habitats. Native populations of priority habitat 9570 (Tetraclinis articulata forests) in continental Europe are located in the southeast of the Iberian Peninsula. The LIFE-TETRACLINIS-EUROPE project aimed to improve habitat conservation conditions. As part of the results of this project, a habitat quality index was proposed with the intention of evaluating both its conservation conditions and its evolution after the implemented action measures. The variables used in this index were selected with the aim of achieving high representativeness of the quality of the habitat while at the same time being easily integrated into monitoring programs. In this paper, we intend to verify the suitability of the variables chosen for this index, its sensitivity to discriminate different conservation levels, and its possible inclusion in forest management programs through a cost-effectiveness analysis.
Extreme climatic events are increasing with climate change, producing changes in communities' climatic characterization. So, mismatches (climatic disequilibrium, CD) between climatic conditions inferred from species' requirements (community inferred climate, CIC) and macroclimate may undergo changes with extreme climatic events. Climatic resilience is defined as the ability to maintain or recover community climatic characteristics, regardless of species' identity, after disturbance or stress.We evaluated the dynamics of plant community climatic characterization in Mediterranean shrublands that experienced a drought event, considering CIC and CD. CIC was calculated by averaging species' climatic niche centroids, weighted by species' relative abundances, in the multivariate environmental space obtained from the climate of the species' geographical occurrence. CD was estimated as Euclidean distance in this space between the observed historic macroclimate and CIC. Climatic resistance was inferred by the distance between pre‐drought and drought CIC, climatic resilience by the distance between pre‐drought and post‐drought CIC, and relative climatic resilience by the same distance weighted by the climatic displacement suffered during the drought. We found a significant reduction in community CD after drought, with CIC becoming more arid, likely due to environmental filtering of those species with wetter distribution. Communities with less pre‐drought CD showed higher climatic resistance but pre‐drought CD did not explain climatic resilience. Communities with more arid CIC exhibited high climatic resilience regardless of drought impact (high relative climatic resilience), except for certain communities exhibiting highly arid CICs. Communities with less arid CIC showed low relative climatic resilience, as their resilience was associated with high resistance.The study highlights community impacts by extreme droughts through filtering of species distributed in more humid climates. This produces changes in the CD of communities, whose resilience is determined by CIC, pre‐drought CD, and drought impact in terms of CIC change.