Estimating forest structure and shade tolerance of the species in a mixed deciduous broad-leaved forest in Abruzzo, Italy

To explain the coexistence of plant species in a mixed deciduous broad-leaved forest in Abruzzo, Italy, a number of leaf traits were analyzed, and the shade tolerance was investigated. Bud break started at the end of April and the rapid leaf growth during the first stages was attested by the highest relative growth rates. The leaf area index (LAI) increased from 0.7 at the beginning of the leaf growth to 2.6 at full lamina expansion. Most of the species of the dominated layer were shade-tolerant and most of the species of the dominant and co-dominant layers were shade-intolerant. There was a fairly well defined specific leaf area (SLA) range between the shade-tolerant (271.1 cm2 g(-1)) and shade-intolerant species (159.2 cm2 g(-1)). The SLA, the chlorophyll content (Chl) and the leaf water content showed the same trend from the top to the bottom of the forest canopy. The chlorophyll a/b ratio ranged from 2.78 (dominant + co-dominant layers) to 2.95 (dominated layer). Laburnum anagyroides Medicus, one of the most shade-tolerant species (305.1 cm(2) g(-1) SLA), showed the highest total chlorophyll content (2.69 mg g-L) and Quercus cerris L., one of the most shade-intolerant (148.2 cm2 g(-1) SLA), the lowest (0.70 mg g(-1)).