Short-term invasibility patterns in burnt and unburnt experimental Mediterranean grassland communities of varying diversities

Abstract

This paper reports the findings of a short-term natural invasibility field study in constructed Mediterranean herbaceous communities of varying diversities, under a fire treatment. Three components of invasibility, i.e. species richness, density and biomass of invaders, have been monitored in burnt and unburnt experimental plots with resident diversity ranging from monocultures to 18-species mixtures. In general, species richness, density and biomass of invaders decreased significantly with the increase of resident species richness. Furthermore, the density and biomass of invading species were significantly influenced by the species composition of resident communities. Although aboveground biomass, leaf area index, canopy height and percent bare ground of the resident communities explained a significant part of the variation in the success of invading species, these covariates did not fully explain the effects of resident species richness. Fire mainly influenced invasibility via soil nutrient levels. The effect of fire on observed invasibility patterns seems to be less important than the effects of resident species richness. Our results demonstrate the importance of species richness and composition in controlling the initial stages of plant invasions in Mediterranean grasslands but that there was a lack of interaction with the effects of fire disturbance.

Invasive species and climate change: Conyza canadensis (L.) Cronquist as a tool for assessing the invasibility of natural plant communities along an aridity gradient

“…The effect of increased competition on C. canadensis at the mesic Mediterranean site was clearly indicated by the decrease in aboveground biomass in quadrats with both C. canadensis and natural plant community, compared to the aboveground biomass in the controls from which the local plant community had been removed. These findings are supported by other studies that examined invasion resistance mechanisms, with C. canadensis as a model plant, and reported similar responses to competition with the local vegetation (Dimitrakopoulos et al 2005;Thébaud et al 1996). Interestingly, in contrast to the negative effects of the competition treatment on the invasive plant, the neighboring plants showed little response to the presence of C. canadensis.…”

Wildland Fire Governance: Perspectives from Greece

“…These fires had the most widespread impact on Chios and Samos, where well over half of the forest cover was lost. While fire-adapted landscapes such as these require periodic burning, research indicates that increases in fire frequency beyond natural fire return intervals can actually lead to elimination of taxa from ecological communities and potential invasion of other, less desirable species (Dimitrakopoulos et al, 2005; see also Aravanopoulos et al, 2004).…”

“…Examination of wildfire issues in Greece requires a basic knowledge about local biophysical characteristics. The islands of Lesvos (1636 km 2 in size), Chios (642 km 2 ), and Samos (477 km 2 ) share a number of characteristics, including rugged mountainous terrain, areas of fire-adapted vegetation (see, for example, Dimitrakopoulos et al, 2005), and extensive stretches of shoreline and beaches. Of the various types of vegetation that make up the forests and woodlands of the islands (Table 2), fire data indicate that most blazes occur in the calabrian pine (Pinus brutia) coniferous forests and in shrublands (for impacts on these forests, see Aravanopoulos et al, 2004).…”

Grazing effects on plant functional group diversity in Mediterranean shrublands

“…Species recorded in these plots were a priori classified into seven PFGs according to Flora Europaea. The selected PFGs were based on the existing literature on plant functional traits in Mediterranean and other types of ecosystems (Lavorel et al 1997;Hooper and Vitousek 1997;Sternberg et al 2000;Troumbis et al 2000;Joshi et al 2001;Dimitrakopoulos et al 2005;Spehn et al 2005;Petchey and Gaston 2006). PFGs defined were: (a) annual forbs (n = 300 species), (b) annual grasses/sedges (n = 67 species), (c) legumes (n = 129 species), (d) perennial forbs (n = 404 species), (e) perennial grasses/sedges (n = 69 species), (f) small shrubs (\150 cm) (n = 94 species) and (g) tall shrubs ([150 cm) (n = 39 species).…”