RESUMEN
Interrelations exist in the terrestrial ecosystems between the plant type and characteristics of nutrient uptake. Annual net nitrogen mineralization in soils of different plant communities in the high altitude zone of Spil mountain located in the Mediterranean phytogeographical region of Turkey was investigated throughout one year by field incubation method. Seasonal fluctuations resulting from field incubation were markedly higher in autumn and spring than summer. These are mainly associated with the changes in soil moisture being at minimum in the Mediterranean summer. A significant correlation was developed between the net Nitrate (kg NO3--N ha week-1) production and soil water content (p<0.05; r =0.316 in soil of 0-5 cm; r =0.312 in soil of 5-15 cm). The results showed that the annual productivity of nitrogen mineralization shows different values depending on communities. Annual net ammonium (NH4+-N) production in the soils of each community was negatively estimated. However, annual net nitrate (NO3--N) production (0-15 cm) was higher in grassland (27.8 kg ha y-1) and shrub (25.0 kg ha y-1) than forest (12.4 kg ha y-1) community. While annual net Nmin values were close to each other in grassland (14.5 kg ha y-1) and shrub (14.1 kg ha y-1), but negative in forest community (-3.6 kg ha y-1). The reasons for these differences are discussed.
RESUMEN
Large areas of land are disturbed in sensitive bio-diverse mountain environments by Ski runs. Restoration of vegetation on such disturbed mountain sites may be hampered by soil degradation but the severity and nature of the constraints is not well understood. This study was designed to compare the water holding and nutritional status of soil in three Ski runs which had different construction dates and disturbance levels, and the adjacent undisturbed site in the Abies bornmuelleriana forest community in the sub-alpine belt of Uludag Mountain (Bithynian Olympus). The values of soil parameters were depressed in proportion to the disturbance level. Water holding capacity (WHC), total nitrogen (N), organic carbon (C) and calcium (Ca2+), magnesium (Mg2+) and potassium (K+) contents (mg kg-1 dry weight) of soils in the Ski run which had the highest disturbance level were lower than that of the undisturbed adjacent sites. However, the results indicated that the soil parameters were less degraded when secondary vegetation was growing on the disturbed areas.