Soil acidification along an ammonium deposition gradient in a Corsican Pine stand in northern Belgium

In a homogeneous Corsican pine (Pinus nigra ssp laricio) stand, situated in a region of intensive livestock breeding, effects of different NHx doses o n soil acidification were studied. Throughfall collectors were placed every 25 m on a transect of 1.4 km, oriented according to the dominant wind dire ction. The throughfall water was analysed on NH4+. A permanent monitoring p lot is situated in the middle of the transect where quantity and chemical c omposition of different water fractions are monitored fortnightly. Along th e transect, soil samples of the upper mineral soil (0-10 cm) were taken and analysed on pH-H2O and pH-KCl. The measured deposition of NH4+-N was very high, especially in the forest edge at the prevailing wind direction (55 kg ha(-1) year(-1)), where up to twice as much NH4+-N was found as in the mon itoring plot. A forest edge zone of 180 m with significantly higher NH4+ de position could clearly be delineated. Serious indications were found that a ll NH4+ was nitrified but that this process was slowed down. The variation in NH4+ depositions was clearly reflected in the state of soil acidificatio n: pH-H2O and pH-KCl values varied between 3.1 ledge) and 3.8 (centre), and 2.4 ledge) and 2.8 (centre) respectively.