Litterfall, litter accumulation and litter decomposition rates in four forest ecosystems in northern Greece

Abstract

Dry weight and N, P, K, Ca, Mg and Na quantities in the litter fall and forest floor were measured in two site qualities of four undisturbed natural forest sites of three coniferous ( Pinus pinaster Aiton, Pinus nigra Arn. v. pallaciana, and Abies borisii regis, Matf.), and one deciduous ( Fagus silvatica L.) species located in northern Greece. Mass and nutrient content of litter fall and forest floor differed greatly among species and generally decreased in the order: F. silvatica> A. borisii regis> P. nigra> P. pinaster. Mean annual litter fall ranged from 4000 kg/ha at the beech site to 1420 kg/ha at the maritime pine site and forest floor dry weight varied from a high of about 82 t/ha under the fir site to a low of 32 t/ha under the maritime pine site. The accretion of nutrients (kg/ha per year) on the forest floor through litterfall ranged from 6.9 to 32.8 for N, 0.7 to 2.8 for P, 3.2 to 12.3 for K, 3.7 to 47.9 for Ca, 1.8 to 8.6 for Mg and from 0.25 to 0.80 for Na. Average element quantities (kg/ha·per year) of the forest floor were between 235.4 and 913.9 for N, 15.4 and 55.8 for P, 40.4 and 113.1 for K, 99.3 and 506.9 for Ca, 39.9 and 285.5 for Mg, and between 3.1 and 18.2 for Na. Site quality did not considerably affect either the litter fall and nutrient returns to the forest floor or the littermass and nutrient accumulation in the L horizon. A positive relationship, however, was noticed between site quality and litter and nutrient accumulation in the F, H horizons beneath the black pine and beech and a negative one beneath the fir. Residence times of forest floor were approximately 17 years at the beech site, 21 years at the black pine site, 23 years at the maritime pine site and 32 years at the fir site suggesting considerable differences in the decomposition rate among forest sites which were mainly associated to the litter fall, the microclimate conditions and the nutrient status of the sites. Further, residence time of litter mass and nutrients were substantially greater in the current study than in other studies carried out in Mediterranean type conditions indicating, slower decomposition rates in Greek forests.