Habitat Degradation Facilitates the Invasion of Neophytes: A Resurvey Study Based on Permanent Vegetation Plots in Oak Forests in Slovenia (Europe)

• Published in: Plants (Basel) 2024-04, Vol.13 (7), p.962
• Main Authors: Kermavnar, Janez, Kutnar, Lado
• Format: Article
• Language: English
• Subjects: Botanical research; canopy openness; Conservation status; Degradation; Disturbances; disturbed soils; Ecosystem integrity; Environmental aspects; Environmental degradation; Erechtites; Erigeron annuus; Flowers & plants; Forests; Forests and forestry; Habitat destruction; Habitats; Impatiens parviflora; Indigenous plants; Indigenous species; introduced plants; invasive non-native plants; Land degradation; long-term vegetation change; Mortality; Nutrients; Oak; oak mortality; overstory; Physiological aspects; Plant communities; Plant introduction; Plant species; Quercus petraea; Quercus robur; Slovenia; Soil conditions; Soils; Solidago gigantea; temporal variation; tree mortality; Trees; Trends; Understory; Vegetation; Wildlife conservation; woody plants
• ISSN: 2223-7747; 2223-7747
• DOI: 10.3390/plants13070962

The spread of neophytes (non-native plant species) challenges the conservation status and ecological integrity of forests, especially in lowland areas. Long-term resurvey studies are needed to evaluate the temporal dynamics of neophytes in forests; however, such data are scarce. In 2023, we resampled a set of 45 permanent vegetation plots (established in 1992/93) in two forest vegetation types: oak-hornbeam forests dominated by and colline oak-beech forests dominated by . Over the last 30 years, oak forests have experienced extensive oak tree mortality, with the degree of habitat degradation being greater in forests. In the early 1990s, only three neophytes with low abundance were recorded across all plots. In the 2023 resurvey, the total number of neophytes increased to 22 species (15 herbaceous and 7 woody species), comprising 6.9% of the total species pool in the understory layer. The increase in the plot-level number and cover of neophytes was significant in plots dominated by but not in those with . The most frequent neophytes were (present in 31% of plots), (27%), (16%) and (16%). The richness and cover of neophytes were significantly affected by the tree layer cover (negative correlation) and the degree of soil disturbance (positive correlation). All neophytes established in disturbed patches, whereas the occurrence of was exceptional as it was able to colonize less degraded, shaded understory environments. Habitat degradation (the mortality-induced loss of stand-forming oak trees resulting in extensive tree layer cover decrease) emerged as a key driver promoting neophyte proliferation, coupled with the impact of management-induced disturbances affecting overstory and soil conditions. The spread is expected to continue or even intensify in the future because novel light regimes and disturbances make forest habitats less resistant to neophyte proliferation.