Contribution to growth and increment analysis on the Italian CONECOFOR Level II Network

The paper deals with the "Estimation of growth and yield" included in the National Programme on Intensive Monitoring of Forest Ecosystems CONECOFOR Aims of the paper are: i) to outline the composition and design of Level II PMPs network, also examining the structural characteristics of forest stands; ii) to describe the contents of mensurational surveys carried out in winter 1996/97 and 1999/00; iii) to analyse the growth rates in progress at each PMP using selected descriptors. Stand origin (11 high forests and 13 stored coppices and transitory crops) and the number of forest types tested are focused as the main discriminants of the PMPs network. This composition, together with irregular forestry practice, results in a number of consequences (prevailing age classes, tree densities and related stand structures, growth patterns) which cause a high in-and-between variability of all growth parameters. For the purposes of this analysis, the network of the plots was divided into three main sets: broadleaved high forest (i.e. beech stands), 6 PMPs; coniferous forest (i.e. Norway spruce stands), 5 PMPs; coppice forest (i.e. deciduous and evergreen oaks, beech and hardbeam stands), 13 PMPs. The measurement of basic growth variables (dbh and tree height) was used to describe the tree populations in each PMP; the calculation of basal area, mean and top dbh, mean and top height, provided the reference dataset at each inventory. The assessment of social class according to Kraft gave information on vertical stand structure and made it possible to analyse growth according to tree layers. Data comparison provided increments in the interval 1997-2000. The occurrence of natural mortality and ingrowth was also assessed to take into account their combined effect on tree population dynamics. No trend was found, due to limited data availability, but it was possible to have a detailed overview of the stand situation and growth rates in PMPs.