Tree ring growth by core sampling at the CONECOFOR Permanent Monitoring Plots. The deciduous oak (Quercus cerris L.) type

Abstract

Radial growth analysis evaluates the ability of trees to grow under different site and environmental conditions, thus contributing to bio-ecological studies aimed at increasing understanding of forest stand evolution. Tree ring growth is analysed in five Permanent Monitoring Plots (PMPs) dominated by Turkey oak (Quercus cerris L.). Common structural features of these PMPs are their origin (coppice forest) and their current physiognomy as stored coppice and transitory crop. A dendroecological approach was used to analyse past radial stem growth, the influence of silvicultural background and stand age, as well as to compare the growth rhythm of stands in different site-indexes and environmental conditions. Tree coring was carried out at the time of the first inventory (winter 1996/97) by sampling 8 to 11 dominant and co-dominant trees representative of the upper storey in the buffer area of each PMP. The basic stem and crown growth variables were measured for each tree sampled and two cores collected at 1.30 m. Annual ring width was determined by the Tree Ring Measurement System SMIL3 and the data were elaborated by the ANAFUS software. Site mean curves and growth trend per social class in each stand were defined both by visual comparison and statistical analysis among individual tree series. The main results were as follows: i) social differentiation becomes established earlier with better site indexes and higher tree densities; ii) sensitivity to external disturbances is higher and more defined in the dominant class than in the co-dominant tree layer; iii) competition cycles are clearly discernible and related to both stand density and site-index in young stands under natural evolution (stored coppices); iv) when silvicultural interventions were performed in the past is quite visible readable in the stands under conversion into high forest (transitory crops); v) the mean series per site are statistically related and common periods characterized by a similar growth trend have been recognized.