Litterfall production and leaf area index in a virgin European beech (Fagus sylvatica L.) – Silver fir (Abies alba Mill.) forest

Because of their role in carbon and nutrient exchange, litterfall and leaf area have been increasingly studied in the last few decades. However, most existing information comes from managed forests, while comparable data for virgin forests is scarce. To address this scarcity, we investigated a mixed beech – silver fir virgin forest located in the Southern Carpathian Mountains, using 78 litter traps to measure the annual litterfall production, litter composition and leaf area index (LAI). The LAI was calculated in two ways: directly, by using litter traps, and indirectly, based on hemispherical photographs. Furthermore, we investigated the influence of different stand and environmental characteristics on litter production, total foliar mass and LAIs. Annual litter productivity ranged from 1.8 to 8.3 t ha−1 with a mean of 3.5 t ha−1. Litter was composed mainly of beech leaves (66%) along with a lower percentage of silver fir needles (16%). The total foliar dry mass (sum of beech leaves and silver fir needles) increased significantly with the proportion of beeches and decreased with the median stand age. The LAI determined by using litter traps had a mean value of 5.06 m2 m−2, ranging from 3.52 to 8.22, and was characterised by a higher variability than the LAI estimated indirectly using the hemispherical approach (which had a mean value of 3.65 and a range of 2.30–5.28). The two indices did not correlate with each other. We found no significant relation between the LAIs and any stand or environmental variables. We conclude that in the more complex forests, such as the virgin beech – silver fir mixed forest we studied, annual foliar dry mass is more closely related to stand characteristics than is LAI. We also note significant limitations of both LAI estimation methods, which indicate that a more elaborate approach to estimating