Impact of the local environmental factors associated to plant-fungi communities on the conservation of Liparis loeselii (L.) Rich. In the French Rhône-Alpes region

Abstract

The fen orchid (Liparis loeselii (L.) Rich., 1817), specific to calcareous wetlands, is threatened by its habitat degradation and disappearance. It is thus categorised as endangered in the Rhône-Alpes red list and is nationally protected in France. Although many studies have been conducted about Liparis loeselii var. ovata ecology in the coastal zone, few have focused on the loeselii variety growing in continental marshes. Now this variety's ecology must be better known in order to determine efficient conservation actions, especially when using ecological restoration in marshes.

The aim of this study is to characterise ecological factors that explain the state of loeselii variety populations in the French Rhône-Alpes region. The conservation state of 13 wetlands populations were related to plant and fungal communities as well as local environmental factors (e.g. hydrology, soil, management). These relationships were pinpointed by mixed models and multivariate analyses comparing community structures that depend on Liparis loeselii presence and the scale of study.

Our results suggest that engineer species are structuring the marsh, creating a hilly micro-topography which is important to L. loeselii, inducing specific plant communities. At the micro-habitat scale, moss bulges are a favourable support to fen orchid development. Furthermore, a constant water supply in wetlands during the season is essential to its growth whereas high temperature explain low occurrence frequency or disappearance of this orchid in some study sites.

This study highlights the dual negative effects of climate change on Liparis loeselii: increasing temperatures and changing rainfall patterns. These two causes induce a synergistic drop in the water table with strong consequences on the conservation status of Liparis populations.