Window of opportunity of Liparis loeselii populations during vegetation succession on the Wadden Sea islands

Abstract

The present study aims at assessing the life span of populations of the orchid L. loeselii during successional in dune slacks on the Wadden Sea islands. An inventory of Liparis loeselii populations was carried out on 6 islands, while the population structure was assessed in more detail on the island of Texel. The occurrence of the orchid was related to soil factors and hydrological conditions. Groundwater levels were measured in a dune area with natural dune slack formation. The groundwater composition was analyses and the freshwater lenses were modelled. Various scenarios were investigated, including sea level rise and sand nourishment. The window of opportunity for L. loeselii to colonize a new slack is relatively narrow. Under favorable management, the population can survive c. 20 years. Soil pH was positively correlated with the occurrence of L. loeselii populations, while a high organic matter content was negatively correlated. Sites with large populations of L. loeselii, were situated in young dune slacks, that functioned as flow-through lakes and has top soilsinfluenced by anoxic calcareous groundwater. Modelling showed that the freshwater lens would decrease due to sea level rise, while artificial sand nourishment could counteract this effect. The populations of the Hors area on Texel, the Netherlands, can survive for several decades due to continuous formation of new slacks. Discharge of calcareous groundwater is essential to keep the pH on a high level. The hydrological systems that supply dune slack with groundwater are relatively small and are vulnerable for changes in sea level rise.

Past and future of the EU-habitat directive species Liparis loeselii in relation to landscape and habitat dynamics in SW-Texel, the Netherlands

“…In addition to vegetation development, abiotic factors such as pH and soil organic matter also affect the survival and population density of L. loeselii (e.g. Stuckey, 1967;Wheeler et al, 1998;Lammerts and Grootjans, 1998;Wotavová et al, 2004;Janečková et al, 2006;Oostermeijer and Hartman, 2014;Grootjans et al, 2016). Favourable conditions recorded for the species include a high pH (N 6), combined with low availability of nutrients and low amounts of soil organic matter.…”

Contrasting fine-scale genetic structure of two sympatric clonal plants in an alpine swampy meadow featured by tussocks

“…Thus, the genetic relatedness of original genets could influence their population viability in the long term. In wetlands, the “opportunity window” for succession often presents itself when flood retreats and seedlings emerge rapidly due to dormancy relief [53, 54]. This is also the case for B .…”

Genetic Diversity of Liparis loeselii in Latvia

“…The presence of L. loeselii depends on the required specific soil conditions in particular microhabitats. A negative effect of the soil organic matter was found on the survival of L. loeselii populations: the extinct populations were associated with sites with high content of organic matter (Grootjans et al, 2017). Accumulation of organic matter in the soil alters many soil properties, such as soil moisture and pH, and, consequently, has a large impact on mineralization rates (Berendse et al, 1998).…”

“…The high concentration of Fe had an indirect effect on increased accumulation of organic matter in soil. Therefore, high iron concentrations might imply indirect impact on the decline of orchid populations (Grootjans et al, 2017). In Latvia, pH levels in soils of microbiotopes with presence of L. loeselii populations varied from acid (pH 4.41) to basic (pH 8.75) (Roze et al, 2015).…”