Author: Giorgi Kozhoridze
A joint research initiative between the Czech University of Life Sciences in Prague and Tel Aviv University aimed to explore a frequently neglected impact of invasive plant species: their capacity to alter the local climate. Concentrating on the delicate coastal sand dunes of the eastern Mediterranean, the research investigated how two invasive species—Acacia saligna, a densely growing tree, and Heterotheca subaxillaris, a resilient herb—are transforming microclimatic conditions in these areas. Our team from the Department of Spatial Sciences at the Faculty of Environmental Sciences (CZU, Prague), along with colleagues from the School of Plant Sciences & Food Security and the Department of Geography and Human Environment at The Porter School of the Environment and Earth Sciences (TAU, Tel Aviv), utilized high-resolution drone imagery and satellite data to monitor how these plants influence crucial environmental factors such as surface temperature, evaporation, and water stress.
Ecological Impacts and Microclimate Alterations
🌿 Heterotheca subaxillaris (Herbaceous Invader)
- Thermal Impact: H. subaxillaris as a herbaceous species, increases surface temperatures throughout its growing season—0.6°C in spring, 1.8°C in summer, and 2.19°C in autumn—compared to native vegetation.
- Water Stress Effects: This species intensifies water stress both directly (by reducing soil moisture through poor ground shading and high PET) and indirectly (via elevated temperatures and increased water vapor loss).
- Vegetation Structure: It exhibits low vegetation signals on satellite images (low SAVI), indicating sparse canopy and minimal soil shading. This allows solar radiation to increase evaporation from exposed soil.
- Ecophysiology: Even though we explored low transpiration and assimilation rates of these herbaceous plants, H. subaxillaris can access deep soil moisture with its extensive root system. Combined with allelopathic and chemical defenses (e.g., sesquiterpene carboxylates), this gives it a strong adaptive edge.
- Impact Summary: H. subaxillaris functions as a microclimate disruptor, exacerbating drought conditions and outcompeting native vegetation through both climatic and biochemical means.
🌳 Acacia saligna (Tree Invader)
- Canopy and Cooling: Unlike H. subaxillaris, A. saligna has a dense canopy and high vegetation signal (SAVI), providing substantial soil shading and a cooling effect on ambient temperatures.
- Transpiration and PET: It has high assimilation and transpiration rates, which elevate water vapor and PET levels, leading to indirect moisture depletion despite its shading.
- Water Stress Influence: While A. saligna does not exert a strong direct effect on water stress, it significantly contributes indirectly through increased evaporation and atmospheric moisture (water vapor).
- Soil Alteration and Competition: A. saligna modifies soil chemistry by enriching nitrogen and reducing key minerals, favoring nitrophilous invasive species. Its allelopathic behavior suppresses native plant regeneration.
- Facilitator of Secondary Invasion: By modifying habitat structure and chemistry, A. saligna indirectly supports the proliferation of co-occurring species like H. subaxillaris.
Conclusions
The study shows that both H. subaxillaris as herbaceous and A. saligna as tree invader plant species severely alter coastal microclimates but through different mechanisms. H. subaxillaris drives direct warming and water stress with minimal shading, while A. saligna cools its immediate environment but promotes long-term ecosystem degradation via high transpiration and chemical soil alteration. Their combined presence reshapes vegetation dynamics and promotes a feedback loop of invasion in water-scarce, sandy environments.
By integrating phenology-tuned remote sensing with ecological analysis, this study offers a replicable framework for monitoring invasive species and understanding their long-term environmental consequences.
Fur more details please see https://doi.org/10.1016/j.agrformet.2025.110606