Dynamics of pure even-aged ash (Fraxinus excelsior L.) stands in view to modelizing“size-density”trajectories of unthinned ash stands, with application in evaluating the impact of Chalara dieback on ash mortality

Résumé 0

The ash datasets came essentially from two networks of permanent and semi-permanent plots installed in the north and the north-east of France. - the first set of permanent plots (set #1) belonged to a network installed in the 1990’s period to study the effects of thinnings on the dynamics (growth and mortality) of pure even-aged ash stands. For the present study, only the unthinned plots of this network (“control plots”) were considered. The stands covered a wide range of initial densities (from 1100 to 40 000 trees per ha). An old additional plot, ‘Fleur-Fontaine’, installed in 1907, was also considered, but only for the period before thinning. In some cases, cleaning operations were performed at the installation of those plots so as to lower the initial stand density and at the same time reduce the importance of species mixed with ash in natural regenerations (‘Val-Saint-Pierre’). - the second set of semi-permanent plots (set #2) was installed later to study more specifically the dynamics of stands at maximum density. These plots were generally young stands originating from natural regenerations, and only those where regular mortality had not started at installation were retained for the study. The four semi-permanent plots retained presented the highest densities observed in the whole data set (between 49000 and 105000 trees per ha). The presence (or absence) of Chalara fraxinea dieback in the studied plots was also mentioned in the data set for each inventory year. The following data appear in the ash dataset: - “Dataset”: data sets #1 and #2 - “Forest”: name of forest - “Plot”: plot number - “Block”: block number - “Dinit”: initial density (‘treatment’) - “Year”: year of inventory - “Cg”: quadratic mean girth at breast height (cm) for years of inventory - “N”: number of live trees per ha for years of inventory - “N0”: number of live trees per ha for the first year of inventory - “Age”: age of the stand (in years) - “Ho”: dominant height (m) = mean height of the largest 100 trees per ha - “Chalara”: absence (0) or presence (1) of Chalara for years of inventory