Testing coexistence of extinction debt and colonization credit in fragmented calcareous grasslands with complex historical dynamics

Abstract

Calcareous grasslands are among the most species-rich ecosystems in temperate countries.However, these ecosystems have suffered from fragmentation and destruction during the last century. We studied the response of calcareous grassland plant diversity to landscape changes in Belgium. Results indicated that high area loss (since 1965) old habitat patches exhibited an extinction debt inverse to low area loss old habitat patches, little depending on the area loss threshold (60%, 70%, 80% or 90%) considered for the distinction between the high and low area loss patches. However, human activities also created new habitat patches in the landscape and therefore provided opportunities for calcareous grassland plant species to colonize new habitats.This also provided opportunities to study species colonization abilities in the context of habitat restoration. We analyzed species richness in new patches compared to old patches in order to detect colonization credit. We detected the presence of a colonization credit in new patches when using high loss old patches (area loss>80%, exhibiting an extinction debt) or all old patches as a reference. However, when the reference was low loss old patches alone (area loss<80%, less likely to exhibit an extinction debt), no colonization credit was detected. In addition, species composition was similar between new patches and old patches. These results are encouraging for restoration programs. However, the results indicated that the presence of an extinction debt in reference habitats could lead to inaccurate conclusions in restoration monitoring. Therefore, extinction debt should be considered when choosing reference habitats to evaluate restoration success.

Specialist plant species harbour higher reproductive performances in recently restored calcareous grasslands than in reference habitats

“…Some species can therefore not yet be observed in the 289 vegetation but can be expected to colonize restored grasslands in ensuing years. In the 290 calcareous grassland of our study region, however, Piqueray et al (2011c) showed that there 291 was no colonization credit for our three study species. The three species considered in the 292 present study have been able to colonize restored habitats.…”

“…However, it has to be noted that reference grasslands are remnant grasslands that 312 have been isolated in the landscape for more than one century. These grasslands surely 313 represent a core area for the calcareous grasslands ecological network, but they may also 314 exhibit an extinction debt that can affect specialist plant species (Piqueray et al 2011c). 315…”

Response of plant functional traits during the restoration of calcareous grasslands from forest stands

“…They had their maximum extensions during the Roman period, the Medieval age and the early Modern Times (Poschlod et al 2008;Poschlod & Baumann 2010), but locally also starting from the Neolithic age on (Dutoit et al 2009). Since the end of the 19 th century, seminatural calcareous grasslands have undergone dramatic decline and fragmentation in European countries Krauss et al 2010;Piqueray et al 2011a). Following abandonment of traditional agro-pastoral practices that were responsible for their maintenance, these unique communities were replaced by arable land, afforestations, or spontaneous encroachment and succession from adjacent forest communities ).…”

“…Both regions have similar species pools (Butaye et al 2005;Piqueray et al 2007). They are separated by a distance of only 40km and have similar land-use histories (Adriaens et al 2006;Piqueray et al 2011a). Due to the large-scale loss of these ecosystems throughout Belgium, more than 100 ha of calcareous grasslands (ca.…”

The Importance of Species Traits for Species Distribution on Oceanic Islands

“…Due to dispersal limitation [11], [12] and extinction debt [13], [14] the distribution of these species may reflect historical habitat configuration. Species distribution in the landscape may then not reflect species long-term ability to successfully colonize habitats and to survive there.…”