Population structure of the rare, long-lived perennial Gentiana pneumonanthe in relation to vegetation and management in the Netherlands
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Published source details
Oostermeijer J. G. B., Van't Veer R. & Den Nijs J. C. M. (1994) Population structure of the rare, long-lived perennial Gentiana pneumonanthe in relation to vegetation and management in the Netherlands. Journal of Applied Ecology, 428-438.
Published source details Oostermeijer J. G. B., Van't Veer R. & Den Nijs J. C. M. (1994) Population structure of the rare, long-lived perennial Gentiana pneumonanthe in relation to vegetation and management in the Netherlands. Journal of Applied Ecology, 428-438.
Summary
In the Netherlands, the marsh gentian Gentiana pneumonanthe used to be a common plant of wet heathland and hay meadows but has become fairly rare in recent decades due to land reclamation, fertilizer application, land drainage and also lack of suitable management at nature reserves. This study investigated the population structure of G.pneumonanthe in relation to vegetation and management in nature reserves throughout the Netherlands.
Study sites: Marsh gentian population structure and associated vegetation characteristics was determined in 60 nature reserves spread throughout the Netherlands.
Marsh gentian age states: Six different marsh gentian age states were distinguished: seeds; seedlings; juveniles; vegetative adults (no flowering stems); generative adults (one of more flowering stem) and dormants (plants in a dormant state with no visible organs above the soil surface. Dependent upon the proportions of each, population types were accorded.
Marsh gentian population types: Three different marsh gentian population types in the different vegetation types were distinguished:
i) 'invasive' or 'dynamic' populations - high densities of seedlings and juveniles relative to adult plants;
ii) 'normal' or 'stable' populations - adult plants prevailing but with low densities of seedlings and juveniles;
iii) 'regressive' or 'senile' populations - only adult flowering and adult vegetative plants.
Effects of management on population structure: In wet heathland sites, a clear trend was observed in the age state structure from 'invasive' populations in young successional stages with a high proportion of bare soil, to 'normal' populations in relatively stable situations, to 'regressive' populations in late successional stages or unmanaged areas dominated by grasses and shrubs with little or no open ground.
In hay meadows, the alternative main habitat where marsh gentians occur in Holland, 'normal' gentian populations were usually observed. However, where mowing has been stopped or where a combination of early mowing and acidification exists, this leads to closure of the vegetation structure by grasses or bryophytes, respectively, and therefore to a 'regressive' population structure as there are few or no open areas in which seeds can germinate and seedlings establish.
Conclusions: The structure of the surrounding vegetation appears to be very important in determining marsh gentian population structure. In particular the amount of bare soil surface and cover of the litter layer explains most of the variation in the density and proportion of different age states in the populations. As the area of bare soil surface in the vegetation increases, so does the proportion of seedlings and juveniles in the population, whilst regressive or senile populations occur where percentage cover of the litter layer is high.
Individuals in heathland and grassland populations seem to have a different life-strategy because of the differences in vegetation dynamics between these two habitat types.
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