Coppicing is a method to regenerate broadleaved trees by cutting them at the base to stimulate the formation of new sprouts. Researchers have now shown that production of these new shoots by beech trees is driven mostly by soil fertility, precipitation, and size of cut stems.
The authors thought that sprouting could depend crucially on the reserves of nutrients (such as carbon and nitrogen) that the tree accumulates in its root system during its life, and that it would crucially decrease if the buds that surround the stem base lost vitality due to aging or damage. Consistently with expectations, sprouting was found to weaken on poor soils, at high precipitation sites, and for stools larger than 25 inches in diameter, because they are more prone to drying up or being damaged. Additionally, in 82% of cases, sprouting was stimulated by leaving one or more shoots on the stool after felling, which maintains the flow of nutrients from the soil to the tree base.
Why are these findings significant?
In southern Europe, coppices have been used for centuries to produce firewood and charcoal. In the last decades, many coppice forests in the Alps were left unmanaged due to depopulation of rural mountain areas. Now the interest in coppices is growing again, due to their ability to sustainably produce energy wood which may replace non-renewable fossil fuels.
Beech is the most common forest species in Italy. The ability of beech to form new sprouts declines with aging. Therefore, by knowing what drives sprouting we can improve forest management decisions in over-aged and abandoned beech coppices, and apply the best silviculture to provide energy biomass, but also biodiversity and hydro-geologic protection.
How was this study conducted?
This study relied on data from 24 beech forest stands in the alpine region of Piedmont, north-western Italy, within an elevation range of 2700-4500 feet. Forests had an age between 1 and 26 years, depending on the time since last management. Forests had been managed as either clearcut coppices (one site, harvest intensity = 100%), coppices with standards (harvest intensity = 72–95%, 15 sites), or had been converted to high forest (61–72%, 8 sites).
In each forest we established a circular sampling plot with an area between 0.1 and 0.15 acres, and recorded slope, aspect, and canopy cover. For each stool in the plot, we counted all cut and uncut shoots, all live and dead resprouts, and measured their diameter and height. We estimated the age of the stand at the time of coppicing by counting tree rings on exposed stools per plot.
We fitted two statistical models to assess how the probability of sprouting and the height of the tallest resprout were affected by topography, soil type, climate, age at coppicing, mean diameter of cut shoots, and type of cutting (all shoots on each stool, or selective cut). Both models were optimized including only significant predictors.
These findings are described in the article entitled Vegetative regeneration of beech coppices for biomass in Piedmont, NW Italy, recently published in the Journal of Biomass and Bioenergy. This work was conducted by Giorgio Vacchiano, Roberta Berretti, Fabio Meloni, Antonio Nosenzo and Renzo Motta from the University of Turin, and Pierpaolo Brenta and Pier Giorgio Terzuolo from IPLA (the Institute for Timber and Environment).