Properties of tracheids are related to the usability of wood for different end-products in pulp and paper industry and in sawmill. Tracheid morphology is correlated with, e.g., optical and physical properties of paper. The detailed knowledge of the processes determining tracheid properties would result in economic benefits. In this study, the relationships between the wood density, tracheid properties and tree growth rate controlled by thinning and fertilisation treatments were investigated in Norway spruce (Picea abies (L.) Karst) trees. The study is among a larger research consortium (Optimisation of the quantity and quality of wood raw material in forest management and industrial processes, “PURO”). The results of this study are used to develop models for predicting the wood and tracheid properties of Norway spruce in Finland.
The tracheid properties of Norway spruce were studied in two thinning-fertilisation experiments established in the 1970s. They were located in central Finland (in Suonenjoki and in Parikkala). At establishment the age of the trees was 38 years in Parikkala (DBH 14 cm) and 53 years in Suonenjoki (DBH 13 cm). The experiments included three thinning and three fertilisation treatments in a randomized block design, i.e., each treatment combination were included once in both experiments. Fertilisation treatments were: (F0) unfertilized; (F1) 150 kg nitrogen (N) / ha per every 5 years; and (F2) 300 kg N / ha per every 5 years. Thinning treatments were: (T0) delayed first thinning, i.e., 60% from original stem number removed 15 after the establishment; (T1) normal thinning, i.e., 30% from original stem number removed at establishment and 30% from original stem number removed 10 years after the establishment; and (T2) intensive first thinning, i.e., 60% from original stem number removed at establishment. In 2003, the sample trees were felled and sample discs were taken at 4 m intervals above breast height. The radial increment and wood density were measured form all the sampled trees; tracheid length, cell wall thickness, and lumen diameter were measured from the samples taken from the plots F0T0, F0T2, F1T0, and F1T2.
Compared to unfertilised control (F0), fertilisation treatments (F1 and F2) increased the radial increment of sample trees (basal-area increment of sample trees, cm2) by, on average, 40%, while wood density on the fertilised plots decreased by 7%. Compared to T0, thinning treatments T1 and T2 increased the radial increment of the sample trees by 8% and 29%, respectively. For wood density the differences between thinning treatments were not significant. Furthermore, we found only small differences in tracheid length (2%–6%), cell wall thickness (2%–15%), and lumen diameter (0%–8%) among different fertilisation and thinning treatments. Conversely, the random intra- and inter- tree variations in wood and tracheid properties of Norway spruce were large.
Keywords: Tracheid properties and wood density, Thinning and fertilization treatments, Norway spruce
Authors
Tuula Jaakkola
Finnish Forest Research Institute, Vantaa Research Unit, Vantaa, Finland
Harri Mäkinen
Finnish Forest Research Institute, Vantaa Research Unit, Vantaa, Finland
Pekka Saranpää
Finnish Forest Research Institute, Vantaa Research Unit, Vantaa, Finland
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