Density management diagrams for sweet chestnut high-forest stands in Portugal

Abstract

This study aims to develop stand density management diagrams (SDMDs) for pure even-aged high-forest stands of sweet chestnut in Portugal, defining the appropriate upper and lower limits of growing stock while considering the biological, technological and economic objectives that are expected for these stands. The SDMDs were developed with data collected from high-forest stands in northern Portugal, which is the main representative area of these stands in the country. Data were collected from 23 pure even-aged permanent plots with re-measurement intervals of 4-10 years, 43 semi-permanent plots and 18 even-aged temporary plots; all plots were established in chestnut high-forest stands with a broad range of ages. SDMDs were constructed by simultaneously fitting four nonlinear equations relating stand variables using the full information likelihood technique. SDMDs for the estimation of stand total volume, stand stem biomass, stand total aboveground biomass, and carbon content in aboveground biomass are presented as bivariate graphs with dominant height on the x-axis and the number of trees per hectare on the y-axis (using logarithmic scale). A tool is made available to define an optimal range of stand density for a silviculture oriented to single-stem selection on a tree-by-tree basis, focusing management on the most valuable trees. This tool is aimed to support forest managers in the decision-making process, enabling them to schedule thinnings on the basis of the dominant height growth of the trees with the greatest potential (frame trees), maintaining an adequate growing stock and assessing the corresponding aboveground wood volume, biomass, carbon, and mean diameter breast height.

Size-density trajectories for even-aged sessile oak (Quercus petraea (Matt.) Liebl.) and common beech (Fagus sylvatica L.) stands revealing similarities and differences in the mortality process

“…This shows how important it is to include size-density trajectory models in stand growth simulators and to be careful when selecting temporary plots in order to establish the maximum size-density line of a given species (Le Goff et al 2011). Such characteristic density lines are at the basis of the construction of density management diagrams-called SDMDswhich are commonly used in the USA since Drew and Flewelling (1979) and more recently in Europe (Sales Luis and Fonseca 2004;Penner et al 2006;Lopez-Sanchez and Rodriguez-Soalleiro 2009;Patricio and Nunes 2017;Minoche et al 2017). It can be mentioned here that the characteristic sizedensity lines represented in these SDMD diagrams are often drawn somewhat arbitrarily parallel to the maximum sizedensity line, whereas the parallelism of these characteristic sizedensity lines for oak and beech could be really established in this study (Fig.…”

The impact of the Asian chestnut gall wasp (Dryocosmus kuriphilus) on chestnut tree growth may be mediated by site resources

“…From initial tree measurements, we estimated the dominant height of each plot (H) as the average height of the thickest trees in the plot. Subsequently, and using information on stand age provided by the owners, we estimated the site index (SI) as the dominant height of the plot at a reference age of 45 years, according to the site index curves reported by Patrício and Nunes (2017) for high chestnut forest stands in the nearby region of Northern Portugal. In addition, we used the number of stems per hectare (N) and H to calculate the relative spacing (RS), which is a measure of stand density.…”

Extreme climatic events affect populations of Asian chestnut gall wasps, Dryocosmus kuriphilus, but do not stop the spread

“…In addition, spatial variability in local site conditions, involving microtopography and soil, can lead to large spatial variability in site quality (Skovsgaard & Vanclay, 2013). The quality of each plot for chestnut growth was assessed through the site index (the expected dominant height of the plot at a reference age of 45 years), according to the site index curves developed by Patricio and Nunes (2017). For our analyses, we recognized eight high-quality sites and eight low-quality sites based on whether the height of dominant trees was greater than or less than 25 m at 45 years.…”