ORIGINAL ARTICLE Kinetic of cracks propagation related to the growth stress of clonal Eucalyptus wood Mahyoub Amer 1 • Bousselham Kabouchi 1 • Mohamed Rahouti 2 • Abderrahim Famiri 3 • Abdelwahed Fidah 3 • Mohsine Ziani 4 • Salah El Alami 1 Received: 26 March 2019 / Accepted: 16 July 2019 Ó Indian Academy of Wood Science 2019 Abstract The growth stress released during felling trees of Eucalyptus sp. and after cutting into logs causes fissure and cracks propagation into the log sections. Evolution and velocity of cracks of woody discs of Eucalyptus grandis and E. camaldulensis clones were investigated. The first set of observations and measurements were taken in 2 h after discs crosscutting. All wood discs presented two cracks developed at opposite directions in the transversal plane RT. The discs of E. grandis have larger values for the length and velocity of cracks and energy liberated than those of E. camaldulensis discs. The second set of obser- vations and measurements were done after 2 weeks of discs cutting. In each disc of E. grandis, the two cracks increased towards the periphery. A third crack was appeared in all discs of E. camaldulensis and extended in a perpendicular direction along the two previous cracks. The cracks size increased, and some of them reach the discs periphery with their side opening. In this stage, the wood discs of E. grandis present lower values for splitting indicators than those of E. camaldulensis wood. So, the good knowledge of the cracks evolution related to the growth stress may help us to take the suitable procedures to reduce their influence in this type of wood during cutting, storage and first transformation. In addition, by these findings com- pleted by further researches, mathematical models can be developed in order to increase sawing yield and to avoid splits on woody boards. Keywords Clonal eucalyptus  Wood  Cracks propagation  Energy liberation  Splitting indicators  Growth stress Introduction In Morocco, plantations of Eucalyptus sp. occupied an area of about 208,000 ha, concentrated in north-west (plain of Gharb) and north (Rif regions). These plantations are dominated by E. camaldulensis, E. grandis, E. gompho- cephala and E. sederoxylon species (Famiri 1996; Hakam et al. 2005). They contribute to the production of pulp- wood, charcoal and firewood. But, their contribution as timber and other wood solid products remains limited because of the high growth stresses of Eucalyptus wood (Famiri et al. 2001; Vega et al. 2016; Amer et al. 2017; Grill et al. 2017). The residual growth stresses in Eucalyptus logs during felling and after their cutting or during logs sawing into boards release an important elastic energy that causes the log-end splitting and apparition of cracks and distortion in logs and boards making operations of sawing and drying delicate as well as depreciating the quality of final wood products and limit their uses (Jullien et al. 2003; Okuyama et al. 2004; Maziri et al. 2010; Daya and Azari 2014; Bodna ´r and Mina ´rik 2015). & Mahyoub Amer mahyoub51973@gmail.com 1 Laboratory of Condensed Matter and Interdisciplinary Sciences, Faculty of Sciences, Mohammed V University, Rabat, Morocco 2 Center of Plant and Microbial Biotechnologies, Biodiversity and Environment, Faculty of Sciences, Mohammed V University, Rabat, Morocco 3 Physics and Mechanics of Wood Laboratory, Research Center of Forestry, Rabat, Morocco 4 National Institute of Archeological Sciences and Patrimony, Rabat, Morocco 123 J Indian Acad Wood Sci https://doi.org/10.1007/s13196-019-00242-z