Organic matter dynamics in beech and pine stands of mountainous Mediterranean climate area

Abstract

Aboveground biomass, litter production and weight loss of litter due to decomposition were monitored in two forest ecosystems in the Sierra de la Demanda, Spain, a Mediterranean climatic zone, over a 3-years period. The two ecosystems were a mature beech forest (Fagus sylvatica L.) and a Scots pine plantation (Pinus sylvestris L.). The aboveground biomass was estimated by cutting and weighing seven trees from each site according to diameter classes, recording the categories of trunk, branches and leaves. The results indicate a total biomass of 152.1 Mg·ha in the pine stand and 132.7 Mg·ha in the beech stand. The percentage distrib- ution of biomass weight of trunks, branches and leaves was similar in both forests. The higher biomass in relation to DBH was esti- mated in the beech forest, which seems to indicate that it would not be very suitable to reforest land that is appropriate for beech with pine. The litter fall was 5 791 kg·ha in the pine forest and 4 682 kg·ha in the beech forest, although variations from year to year were observed, mostly due to water stress in summer. Weight loss due to decomposition of litter was similar in the two forest ecosystems, apparently due to the similarity in rainfall distribution at the sites. Jenny's litter decomposition index (K) and Olson's litter decomposition index (K were higher for the Scots pine stand than for the beech stand, K: 0.46 and 0.37, K 0.82 and 0.59, respectively, and Jenny's leaves and Olson's decomposition indices were similar. © 1999 Inra/Editions scientifiques et medi-