Drying characteristics of wood of invasive tree species growing in an urban environment: Določanje sušilnih karakteristik lesa invazivnih drevesnih vrst rastočih v urbanem okolju | Določanje sušilnih karakteristik lesa invazivnih drevesnih vrst rastočih v urbanem okolju: Drying characteristics of wood of invasive tree species growing in an urban environment

anglais. Non-native tree species are increasingly growing in urban environments, where they are exposed to cultivation and pruning measures, and in many cases their growth becomes uncontrolled, even invasive. In such cases the structure of the wood is more heterogeneous, with more tyloses, discolorations and decay, and higher moisture content. The drying of such wood is more demanding and cannot rely on the standard drying schedules. Therefore, the drying kinetics of the boards (thickness 22 mm, 28 mm and 46 mm) of three wood species (black locust – Robinia pseudoacacia; box elder – Acer negundo and horse chestnut – Aesculus hippocastanum) were analysed at 20 °C and 40 °C. Additionally, the drying quality was assessed by determining the moisture content gradient, drying stresses and presence of typical drying defects. In the drying tests the moisture content gradients were relatively low in all species, so no high drying stresses were generated. Due to the expected high risk of collapse, careful drying of green maple was needed, to prevent board twisting when a pronounced number of knots and greater fibre deviation occurred. Half-drying times indicated the longer drying of thicker black locust boards, and very careful drying of maple. We confirmed the usability of the half-drying time to compare the drying kinetics of different wood species and assortments.

slovène. V vrtovih in parkih se zaradi oblik in privlačnega videza vse pogosteje razširjajo neavtohtone drevesne vrste, ki so podrejene posebnim gojitvenim in obrezovalnim ukrepom. Pogosto lahko postane njihova širitev nekontrolirana, celo invazivna. V primeru takih dreves je struktura lesa bolj heterogena, les je bolj verjetno otiljen, diskoloriran in okužen ter ima višjo vlažnost. Sušenje takšnega lesa je težavnejše in ne omogoča uporabe standardnih sušilnih programov. Raziskali smo kinetiko sušenja treh lesnih vrst (robinije – Robinia pseudoacacia; amerikanskega javorja – Acer negundo in divjega kostanja– Aesculus hippocastanum). Sušili smo deske debelin 22 mm, 28 mm in 46 mm pri 20 °C in 40 °C. Ob tem smo spremljali kakovost sušenja. Ocenjevali smo vlažnostni gradient, sušilne napetosti in pojav značilnih napak pri sušenju. Pri sušilnih preizkušancih so bili vlažnostni gradienti pri vseh lesnih vrstah razmeroma nizki, zato nismo zabeležili visokih sušilnih napetosti. Raziskave so pokazale, da je zaradi ugotovljene nevarnosti kolapsa potrebno previdno sušenje lesa svežega javorja, da se prepreči krivljenje desk, zlasti ob prisotnosti številnih grč in večjem odstopanju poteka lesnih vlaken. Polovični časi sušenja so nakazovali daljše sušenje debelejših preizkušancev robinije in zelo previdno sušenje javorja. Potrdili smo uporabnost kinetike polovičnega časa sušenja različnih vrst in debelin lesa.