Environmental control of plant species abundance in a microtidal Mediterranean saltmarsh

Batriu E., Pino J., Rovira P., Ninot J.M. (2011) Environmental control of plant species abundance in a microtidal Mediterranean saltmarsh. Applied Vegetation Science. 14: 358-366.
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Doi: 10.1111/j.1654-109X.2011.01122.x

Resum:

Question: To what extent are environmental factors the main determinants of species abundance in Mediterranean coastal marshlands? Location: The Llobregat delta, Barcelona, Spain. Methods: Vegetation relevés were performed and a set of water table and soil variables were periodically monitored in 43 sampling points randomly distributed in four marsh areas (sites) along a coastal-inland gradient. A canonical correspondence analysis (CCA) was performed to identify the primary water and soil correlates of species cover, after considering the effect of site and point spatial location. The realized niches of dominant species were modeled through GLMs performed on the first two axes of CCA. Niche overlapping among these species was compared with their coexistence, assessed through pairwise correlations of relative species cover in each sampling point. Results: Water and soil variables explained more of the variation in species' abundance than site and spatial position. Mean water table level, maximum water conductivity and sodium adsorption ratio (SAR), summarized in the two first CCA axes, explained 23.8% of the variability in species' cover. Arthrocnemum fruticosum, Phragmites australis subsp. australis, Juncus acutus, Spartina versicolor and Juncus maritimus dominated the vegetation stands. Niches obtained from GLM response curves showed moderate overlapping among all these species except for A. fruticosum. However, pairwise correlations were mainly negative or non-significant, indicating low coincidence, and even segregation, between species' cover. Conclusions: The abundance of dominant plants in Mediterranean marshes is only partly explained by the environmental gradients summarized in niche models. The role of other factors such as facilitation or competition between species and random recruitment should be explored. © 2011 International Association for Vegetation Science.

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Deconstructing the native–exotic richness relationship in plants.

Bartomeus I, Sol D, Pino J, Vicente P, Font X (2011) Deconstructing the native–exotic richness relationship in plants. Global Ecology and Biogeography doi: 10.1111/j.1466-8238.2011.00708.x.

Widespread plant species: Natives versus aliens in our changing world

Stohlgren T.J., Pyšek P., Kartesz J., Nishino M., Pauchard A., Winter M., Pino J., Richardson D.M., Wilson J.R.U., Murray B.R., Phillips M.L., Ming-yang L., Celesti-Grapow L., Font X. (2011) Widespread plant species: Natives versus aliens in our changing world. Biological Invasions. 13: 1931-1944.
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Doi: 10.1007/s10530-011-0024-9

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Estimates of the level of invasion for a region are traditionally based on relative numbers of native and alien species. However, alien species differ dramatically in the size of their invasive ranges. Here we present the first study to quantify the level of invasion for several regions of the world in terms of the most widely distributed plant species (natives vs. aliens). Aliens accounted for 51.3% of the 120 most widely distributed plant species in North America, 43.3% in New South Wales (Australia), 34.2% in Chile, 29.7% in Argentina, and 22.5% in the Republic of South Africa. However, Europe had only 1% of alien species among the most widespread species of the flora. Across regions, alien species relative to native species were either as well-distributed (10 comparisons) or more widely distributed (5 comparisons). These striking patterns highlight the profound contribution that widespread invasive alien plants make to floristic dominance patterns across different regions. Many of the most widespread species are alien plants, and, in particular, Europe and Asia appear as major contributors to the homogenization of the floras in the Americas. We recommend that spatial extent of invasion should be explicitly incorporated in assessments of invasibility, globalization, and risk assessments. © 2011 Springer Science+Business Media B.V.

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