| 2 | Understanding plant drought resistance in a Mediterranean coastal sand dune ecosystem:differences between native and exotic invasive species显示文摘Aims Mediterranean coastal dunes are habitats of great conservation interest,with a distinctive and rich flora.In the last century,Acacia spp.,native from Australia,have been introduced in Portugal,with the objective of stabilizing sand dunes,and since have become dominant in numerous sand dune habitats.This invasion process led to the reduction of native plant species richness,changed soil characteristics and modified habitat’s microclimatic char-acteristics.The aim of this research was to typify and compare,in Mediterranean sand dune ecosystems,the ecophysiological responses to drought of Helichrysum italicum and Corema album,two native species,and Acacia longifolia,an exotic invasive spe-cies.We addressed the following specific objectives:(i)to com-pare water relations and water use efficiencies,(ii)to evaluate water stress,(iii)to assess water use strategies and water sources used by plants and(iv)to evaluate the morphological adaptations at leaf and phyllode level.Methods In order to obtain an integrative view of ecophysiological patterns,water relations and performance measuring methods have been applied:predawn(ψPD)and midday(ψMD)water potential,chloro-phyll a fluorescence,oxygen isotopic composition of xylem,rain and groundwater(δ18O)and leaf carbon isotopic discrimination(Δ13C).The leaf characteristics of the three species,as well as the histochemistry of non-glandular trichome cell walls,were also studied to identify morpho-traits related to drought resistance.Important Findings The results support our initial hypothesis:although A.longifolia clearly possesses a degree of resistance to water stress,such ability is provided by a different water strategy,when compared to native species.Natives relied on morphological adaptations to restrict water loss,whereas the invasive species adjusted the water uptake as a way to balance their limited ability of restricting water loss.We corroborate that woody native species(i)have a conservative water-saving strategy and minor seasonal variations relative to invasive species,(ii)use enriched water sources during drought periods,indicating different water sources and root systems com-paring with invasive species and(iii)present drought leaf morpho-functional adaptations related with limiting water loss.Comparing the physiological performance of invasive and native species can offer causal explanations for the relative success of alien plant invasions on sand dunes ecosystems. | Cristina Antunes Ana Júlia Pereira Patrícia Fernandes Margarida Ramos Lia Ascensão Otília Correia Cristina Máguas | 2018 | Journal of Plant Ecology2018，11，1： | 4 |
| 3 | The ecological performance of metallophyte plants thriving in geochemical islands is explained by the Inclusive Niche Hypothesis显示文摘Aims The Inclusive Niche Hypothesis has not been validated for plants using ecophysiological performance.The few experiments have measured growth and competition but not the physiological response of plants.A metallophyte plant that hyperaccumulates aluminium(Al),Plantago almogravensis,showed a defined spa-tial distribution by occurring mostly on vegetation gaps associ-ated with metalliferous areas(geochemical islands).This case was used to determine,in situ,whether the Inclusive Niche Hypothesis was suitable to explain the extent of the species real-ized niche.Methods The vegetation associated with P.almogravensis geochemical islands in the SW coast of Portugal was mapped.The biotic(neighbouring plants)and abiotic(edaphic)components of the niche were cor-related with parameters of the plant’s ecological and physiological performances(plant density and cover;leaf C and N concentration and isotopic composition;growth).The results were obtained using image analysis,abundance and morphological measures,isotopic signatures and chemical composition.Important Findings The species showed better physiological performance where its ecological performance was lower due to trade-offs with environ-mental constraints.The species’realized niche was mostly limited by shrub competition and soil Al-toxicity.These limits contribute to explain the rarity status of the species:the species has a poor capacity to compete but,due to an enhanced Al-tolerance and Al-hyperaccumulator trait,has the ability to find refuge in geochem-ical islands that are too harsh for most other species.This work,based on ecophysiological field studies,provides support for the Inclusive Niche Hypothesis relating to plant species. | Helena C.Serrano Cristina Antunes Manuel J.Pinto Cristina Máguas Maria Amélia Martins-Loução Cristina Branquinho | 2015 | Journal of Plant Ecology2015，8，1： | 0 |
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