Impact of grazing on the input of organic matter and nutrients to the soilin a grass-encroached Scots pine forest

In the Netherlands, grazing is used as a measure to counteract grass-encroa chment in Dutch pine forests. A 7-year experiment with moderate and heavy g razing intensities versus non-grazed control situations was performed to ev aluate the impact of grazing on nutrient cycling in these forest ecosystems . In this paper, changes in organic matter and nutrient input to the soil c ompartment due to grazing are quantified. Grazing resulted in a 50% reducti on of grass shoots, which was partly caused by a lower biomass production ( 35%) Grass root production and input also decreased by about 30%. Total lit ter input in the pine stand was only reduced by 20%, due to the lack of imp act on tree litter input. The relative contribution of pine litter to the t otal litter input increased from about 30 to 40%. Grazing also reduced the input of nutrients, but reduction was not equal for all nutrients. Changes in nutrient input were not a result of changed nutrient concentrations in l itter, but were due to shifts in the relative contribution of different lit ter types. Potassium was most reduced (30%) and reduction was mainly due to biomass consumption, while the input of N and P (20-23% reduction) was mai nly affected by decreased production of grass roots and shoots. The input o f Ca was least affected by grazing: 10% reduction. Reduced input of fresh l itter and nutrients and an increased contribution of pine litter may result in lower decomposition rates and presumably decreased nutrient availabilit y. This may affect biomass production and nutrient cycling through the gras s layer. (C) 2001 Elsevier Science B.V. All rights reserved.