LEAF NITROGEN AS A FACTOR OF SUSTAINABLE DEVELOPMENT IN TWO CHESTNUT FOREST ECOSYSTEMS IN SALAMANCA AREA, SPAIN

The leaf nitrogen contents of two Castanea sativa Mill. forest stands of the Salamanca province in Spain were monitored, relating the amounts with other structural population characteristics. For this, different experiments were conducted: the analysis of nitrogen levels in leaf aboveground biomass, leaf litterfall, leaves decomposing during a two year period, and a seasonal nitrogen variation during a vegetative cycle. The two ecosystems were: a chestnut grove and a chestnut coppice. The calculated leaf biomass in chestnut coppice stand was 2850 kg ha^-1 (about 2% overall). Perennial material (trunks and branches) represented 98% of the total biomass. The turnover or rotation coefficient for N was 44.4 in chestnut coppice stand. In both plots, the highest leaf nitrogen concentration was observed in the spring and summer months, during initial leaf growth. Thereafter, they decreased due to retranslocation during the period of leaf fall in autumn. The relation: Nutrients in leaf biomass – Nutrients in leaf litterfall = Translocation to perennial parts for N was 24.9 kg ha^-1 in chestnut coppice stand.