Woody Plant Life-Form Structure Reflects Major Ecological Gradients Within a Protected Temperate Ecosystem from Romania

This study, conducted in the Cheile Nerei-Beușnița National Park (southwestern Romania), tested the hypothesis that the life-form structure of woody plants reflects the main ecological gradients of moisture, temperature, and soil reaction in a temperate protected ecosystem characterised by sub-Mediterranean influences and a predominantly calcareous substrate. The analysis focused on the woody flora of the area, comprising 64 species belonging to 22 families, and included the assessment of life-form structure, phytogeographical spectrum, and ecological preferences based on Ellenberg indicator values. Life forms were classified according to Raunkiaer's system, identifying megaphanerophytes, mesophanerophytes, and nanophanerophytes. The woody flora was dominated by nanophanerophytes, followed by megaphanerophytes and mesophanerophytes, indicating a complex vertical structure. The phytogeographical spectrum showed a predominance of European elements, alongside Eurasian and sub-Mediterranean components. Ecological analysis revealed a dominance of mesophilous and mesothermal species, consistent with mesic and temperate environmental conditions. Soil reaction preferences were mainly basiphilous and neutrophilous, reflecting the calcareous substrate, with vertical differentiation of ecological niches between tree and shrub layers. The high proportion of native species (>90%) and the limited presence of alien taxa indicate a high level of ecological integrity and resistance to biological invasions. Overall, the results demonstrate that the structure of woody plant life forms and their ecological preferences accurately reflect the main ecological gradients of the ecosystem. The combined use of life-form spectra and ecological indicator values provides a useful framework for assessing ecosystem structure, stability, and conservation status in temperate protected areas.