How upward seepage of alkaline groundwater sustains plant species diversity of mesotrophic meadows

“Wet mesotrophic meadows depending on upward seepage of fresh alkaline
groundwater, regarded as the Dutch crown jewels of biodiversity, have declined
dramatically in both surface area and botanical quality over the last century. Nowadays,
these low productive meadows are only found in protected nature reserves, usually small
ones, isolated in an intensively used agricultural landscape. The high biodiversity is
explained by the supply of unpolluted, base rich groundwater, which ensures a relatively
high and stable groundwater level and leads, in combination with a limited amount of
infiltrating precipitation water, to small scale water quality gradients in the soil. These
gradients range from base rich, mesotrophic with a circumneutral pH to base poor
oligotrophic and more acid conditions in the root environment of the plants. As a result,
plant species with different environmental preferences can grow next to and interwoven
with each other. Deep intensive drainage in the agricultural areas surrounding the reserves
resulted in reduced seepage intensities, and increased influence of infiltrated precipitation
water in the soil. As a result, the buffering capacity of many Dutch fen meadow soils
decreased and small scale hydrochemical gradients disappeared, resulting in a loss of
biodiversity. To restore seepage dependent meadow ecosystems to their full floristic glory,
water management measures should aim at restoring seepage intensities and high
groundwater levels, whilst at the same time preserving small scale abiotic gradients. This
requires delicate measures, which are only feasible with enough knowledge about the
hydrological and biogeochemical processes driving the small scale abiotic gradients. So far
however, knowledge was insufficient to take such measures effectively.”

(Citaat: Cirkel, D.G. – How upward seepage of alkaline groundwater sustains plant species diversity of mesotrophic meadows (2014))