N, K and P deficiency in chronosequential cut summer-dry grasslands on gley podzol after the cessation of fertilizer application

With the intensification of agricultural practices, formerly species rich marginal grassland communities of high botanical value in the Netherlands have been fertilized or manured since the first part of the twentieth century. This type of land use resulted in a dramatic decrease of the original plant species-richness. In the early 1970's yearly nutrient input to many of these grasslands was ceased as a nature management practice, while hay-cropping was continued. This type of grassland management is carried out to decrease overall nutrient supplying ability of the soil to plant cover in order to restore their original high botanical richness. The effect of this management on the type and the extent of nutrient deficiency was studied by comparing the short-term shoot responsiveness of undisturbed turfs to added nutrients and the nutrient status of fieldgrown dominants of four hay-field communities which were not fertilized for 3, 7, 20 or 25 years. Contrary to expectation, hay-cropping without input of additional nutrients did not impose an increase of species-richness of grassland on gley podzol. During early vegetation change strong inadequacy of N supply and moderate inadequacy of K supply by the soil regulate (shoot) growth. P-deficiency was not established. Prolonged discontinuation of fertilizer application caused concomitant inadequate supplies of N, K and P. In the last field (25 years unfertilized), nutrient deficiencies could not be detected by shoot growth responses to added nutrients but only by a low nutrient status. It appeared that during this type of vegetation change N-deficiency is the most pronounced and that K-deficiency developes much more rapidly than P-deficiency. The strong decline in total aerial pool sizes of N, K and P also emphasizes these simultaneously occurring shifts. We conclude that cut grassland composition on gley podzol soil is regulated by co-deficiencies of at least the soil phytoavailable macronutrients nitrogen, potassium and phosphorus. The absence of change in plant species number is likely not regulated by the nutrient supplying ability of the soil. Seed dispersal from elsewhere seems to be the most important factor

Restoration of Wet Dune Slacks on the Dutch Wadden Sea Islands: Recolonization After Large-Scale Sod Cutting

The effects of sod cutting were studied in a dune area on the Dutch Wadden Sea Island of Texel. Sod cutting was carried out in a range of different dune slacks in order to restore dune slack vegetation with many endangered Red List species. Sod cutting removed approximately 96% of the soil seed bank. Species abundant in the seed bank, notably Juncacea, also had a high frequency in the vegetation that established during the first year after the restoration measures. Many other species not registered in the seed bank or in the former vegetation also appeared. Species richness in the monitored plots exceeded that of uncut reference plots after a few years. Colonization rates were higher than extinction rates in most plots, indicating that a stable state has not been reached after 5 years. Differences in species richness between slacks appeared to be related to the occurrence of source areas nearby and availability of dispersal agents, such as flooding and animals.