Quantifying the resilience of coastal phytocoenoses though a trait-based adaptation index

Abstract

Coastal ecosystems, particularly in Mediterranean regions, are increasingly threatened by climate change and the associated fluctuations in salinity, temperature and drought. The long-term survivability of coastal phytocoenoses depends on their ability to adapt quickly to these conditions. Current assessment methods, often based on static inventories, may not capture the functional mechanisms. To address this gap, we developed a novel, trait-based ‘Index of Adaptation’, which quantifies how plant communities persist under environmental stress by measuring functional adaptation across sites and stress gradients. We hypothesised that harsher coastal habitats, defined by high abiotic stress, would necessitate a higher degree of local functional adaptation for community survival, reflected in a high index score. For our trait-based approach we quantified key morphological adaptations of coastal halophytes and xerophytes (e.g., leaf area, stomatal dimensions, trichome density, chlorophyll a content, epidermal thickness) during both the peak growing season (wet) and the peak stress season (dry). This temporal comparison is critical for distinguishing plastic responses from constitutive strategies. These data were used to define two metrics: A “Performance Score” (PERF) that quantifies the community’s physiological condition during the harsh summer period. It is calculated from trait values that reflect the capacity to maintain physiological function under stress. A high PERF score indicates a community that "performs" well during the primary annual selection bottleneck. [excerpt]