Peeler core and slabwood fibre properties for Pinus radiata D.Don pulp production

Background: Pulp production based on Pinus radiata D.Don is constantly improving the value recovery of logs. One example is using the peeler cores and slabwood derived from sawing and peeling processes to produce pulp. However, these two raw materials have not been characterised for their fibre properties.  Methods: We report on four wood fibre quality attributes derived from peeler cores and slabwood, directly influencing pulp quality and pulping process: fibre length (mm), fibre width (µm), fines content (%), and coarseness (µg/m). This pilot study sampled two P. radiata stands grown on different sites and early silvicultural regimes in the Araucanía Region of Chile. Analysis of wood fibre consisted of three trees per stand, and six discs per tree: two at the bottom, two at breast height (1.3 m), and the last two at 5.23 m height.  Results: The trajectory of mean annual increment in diameter at breast height (MAI) and periodic annual increment in diameter at breast height (PAI) for trees in the two stands aligned with their respective site qualities and silvicultural regimes. In Stand 1, with a site index of 36, and Stand 2, with a site index of 31, the average proportions of juvenile wood (measured at 1.3 m) were 50% and 53%, respectively. Thus, despite weed control and fertiliser application in Stand 1, there was no increase observed in the proportion of juvenile wood. There were significant differences in fibre properties between peeler core and slabwood, and these differences were present across the range of tree heights and diameters (p<0.05). While there were no statistically significant differences among disc positions, significant distinctions emerged between stands and wood types. The interaction between these factors was also found to be statistically significant (p<0.05). Conclusions: Our study suggests that adding these two materials into the mix for producing pulp would have positive implications due to pulp from peeler core is more suitable for printing and writing grades and addition of mature wood from slabwood, could improve strength properties of paper manufacture. However, it is necessary to test the optimal proportion for the final mix.