Ecological behaviour of herbaceous forest species along a pH gradient: a comparison between oceanic and semicontinental regions in northern France

Abstract

Aim On the basis of 2402 phytoecological relevés, with complete species lists, and real pH measurements resulting from chemical analyses of the top layer of forest soils, this paper compares quantitatively the ecological response of 46 herbaceous forest species along a pH gradient in two regions of northern France. LocationThe two regions investigated are oceanic north-western France (NW) and semicontinental north-eastern France (NE). MethodsFor each of the 46 species with more than 50 occurrences in both NW and NE regions, an ecological response curve was computed with simple logistic regression models, and two synthetic numerical values were derived: ecological optimum (OPT) and ecological amplitude (AMP). A comparison of the ecological behaviour of species present in both regions was performed in terms of shift in optimum and/or amplitude. ResultsAll 46 species did reveal a reaction to pH. Our main observation was the relative stability of the behaviour of most species with reference to pH conditions, which is consistent with results from some previous studies. Slight differences regarding the two synthetic parameters (OPT and AMP) were however observed between the NW and NE regions, probably due to a form of competitive release in neutral environments in the NW. Main conclusionsAmong the main possibilities that could explain a geographical shift in the ecological behaviour of herbaceous species, competitive effects are, we suggest, the most plausible explanation. In the light of former studies, it seems that further analyses of geographical shifts in the ecological behaviour of forest plant species over large areas are needed, such as for example over the European continent.Nomenclature Tutin et al . (2001).

Plant Species Responses to an Elevational Gradient in German North Sea Salt Marshes

“…6 Species response curves, fitted by Huisman-Olff-Fresco (HOF; Oksanen and Minchin 2002a, b) modelling for 19 species (frequency >5%) on the basis of 2,691 1-m 2 plots, displaying each species' probability of occurrence with respect to the elevational gradient in relation to MHT (cm; zero line dotted). For each species, the estimated lower and upper limit are highlighted (solid lines) to mark species' amplitude (Gégout and Pierrat 1998;Coudun and Gégout 2005). For a summary of model types and parameters of the response curves see Electronic Appendix 2.…”

“…Under field conditions 'physiological niches' of species are usually constrained by competition (see Ellenberg et al 1992). There are various parameters for describing 'ecological niches' (Hutchinson 1957) including minima-maximaranges (Bockelmann et al 2002), medians (Sánchez et al 1996;Silvestri et al 2005), tolerances (ter Braak and Looman 1986;Schröder et al 2005), or amplitudes (Coudun and Gégout 2005;Peppler-Lisbach 2008). Species response curves are another useful tool (ter Braak and Looman 1986;Gégout and Pierrat 1998;Pakeman et al 2008) to link species' presence/absence or abundance data to gradients.…”

“…Studies of species response along environmental gradients have mostly been applied to consistent, but small data sets (e.g., Wierda et al 1997) or to large, but combined data sets of different relevés sources (e.g., Coudun and Gégout 2005). Salt marshes are well-suited to study species responses along gradients because the ends of gradients are often well-defined due to their limited extension from sea to land.…”

Assessing the response of open-habitat bird species to landscape changes in Mediterranean mosaics

“…In this context, the continuum model (Austin 1999) is being taken into consideration through the definition of habitat gradients and creates an explicit link between species' distribution patterns and ecological processes (Fischer and Lindenmayer 2006). Most of the studies about response curves along an ecological gradient have been conducted on plant species (Austin 2002;Oksanen and Minchin 2002;Rydgren et al 2003;Coudun and Gegout 2005;Yee 2006) and relatively little research has focused on response curves for animals describing ecological processes at the landscape scale (Suárez-Seoane et al 2002).…”

Can understory vegetation accurately predict site index? A comparative study using floristic and abiotic indices in sessile oak (Quercus petraea Liebl.) stands in northern France

“…The nutrient gradient expressed by the first axis was practically identical in both regional samples despite the change in floristic composition. Moreover, Coudun and Gégout [18] recently showed that the pH behaviour of plant species is close in the north-eastern and north-western part of France: the correlation between regional pH indicator values is 0.78 and 75% of the species have regional pH indicator values differences lower than 0.5.…”