Assessing the residual effects of Carpobrotus edulis invasion, implications for restoration

Abstract

We examined whether the residual effects on soil caused by the invasion of Carpobrotus edulis, common iceplant, would inhibit the reestablishment of a native plant species. Carpobrotus edulis interacts both directly by suppressing the growth and establishment of other plants and indirectly by altering soil chemistry. We tested whether the residual effects of C. edulis resulted in lowered germination, survival, growth, and reproduction of Gilia millefoliata, a rare dune annual. We compared G. millefoliata planted in plots previously occupied by C. edulis to G. millefoliata planted in plots that previously had native vegetation. Each plot received three treatments: seed, transplant, and unplanted, and were censused every three weeks until senescence. Carpobrotus edulis had strong negative effects on the germination, survival, growth, and reproduction of G. millefoliata. C. edulis lowers soil pH and increases organic content due to the recalcitrance of tissue to decomposition, which may have evolved as a mechanism to facilitate recolonization and invasion.

Distribution of alien species along sand dune plant communities zonation

“…Some invaders, such as Carpobrotus edulis, affect the community composition, diversity and succession via modification of the soil properties. It has been shown that the effect of C. edulis on pH and nitrogen compounds persists over time even after Carpobrotus removal (13,14). This suggests a possible allelopathic effect of its litter (14).…”

Long-term spatio-temporal expansion of the native-invasive Retama monosperma on coastal dunes: Importance of land-use and natural dispersal vectors

“…The process involves significant changes in dune geomorphology and other environmental characteristics, such as lower incidence of wind and salt spray and increases in soil organic matter and nutrients (El-Bana et al, 2002;Muñoz Vallés et al, 2011) as well as in the type of flora and fauna supported by the dunes (Lichter, 1998;Levin and Ben-Dor, 2004;Plassmann et al, 2010). In different parts of the world, dune stabilization is having a negative impact on the richness and diversity of dune plant and animal species of high conservation value, and is becoming an important environmental problem (Avis, 1995;Alvarez and Cushman, 2002;Conser and Connor, 2009;Isermann et al, 2007;Isermann, 2008;Kutiel et al, 2004a;Marchante et al, 2008;Wiedemann and Pickart, 1996). At present, fixation and stabilization of coastal dunes are identified by several authors as one of the main threats to these ecosystems (Isermann et al, 2007;Jørgensen and Kollmann, 2008;Kutiel et al, 2004a).…”

“…Over time, many of these species have spread beyond their initial plantation areas, further stabilizing the surrounding dune systems, and sometimes exhibiting invasive behaviour and causing serious problems for the conservation of the coastal dune ecosystems (Avis, 1995;Conser and Connor, 2009;Marchante et al, 2008;Zunzunegui et al, 2012).…”

Weak effects of the exotic invasive Carpobrotus edulis on the structure and composition of Portuguese sand-dune communities

“…These ecosystems, and the Mediterranean sand-dunes in particular, are of high biogeographic interest, and hold many threatened species and endemisms (Habitat Directive 92/43EEC). Despite their conservation value, they are constantly under threat from human constructions and leisure activities, and from biological invasions by exotic plants (e.g., D'Antonio 1993;Conser and Connor 2009). Such invasions have been considered the second most important cause of change in the composition, structure, and functioning of natural ecosystems worldwide-following habitat destruction (Simberloff et al 2005;Thuiller et al 2005;Walther et al 2002).…”

“…Different studies have described the spread of C. edulis in sand dune ecosystems of Portugal (Almeida and Freitas 2001;Campelo et al 1999), and the direct and indirect negative influences of this exotic invasive on native plant communities worldwide: it competes for space and resources, and alters soil chemistry and nutrient cycles (e.g., Albert 1995;D'Antonio and Haubensak 1998). However, most studies on the interactions between this exotic invasive and the native communities it invades have considered only one or a few target native species (e.g., Conser and Connor 2009), or focused on the mechanisms of competition between C. edulis and natives (D'Antonio and Mahall 1991;Traveset et al 2008). Little attention has been given to the effects of C. edulis on the structure and composition of invaded communities.…”