MECHANISMS FOR CARBON AND NUTRIENT RELEASE AND RETENTION IN BEECH FOREST GAPS .1. MICROCLIMATE, WATER-BALANCE AND SEEPAGE WATER CHEMISTRY

Nutrient cycling and water balance in forest gaps has received little attention until now, although gap regeneration is important to natural dynamics of temperate forests. Gaps of 30 m diameter, cut in a mature beech forest, exhibited a distinct change in microclimatic conditions in comparison with the surrounding stand. Soil moisture in gaps remai ned very high throughout the observation period. Disruption of the N c ycle in gaps led to substantial nitrate losses; seepage water nitrate concentrations were 10-18 mg NO3-N L(-1). Excess nitrification was a s ignificant cause of soil acidification and aluminium release. The pH i n subsoil seepage water decreased by 0.25. Liming in gaps promoted the establishment of a herbaceous vegetation, which functioned as an impo rtant nutrient sink, and thus is recommended for tree regeneration in highly acidified forest ecosystems as it increases the resilience of t he ecosystem to nutrient losses.