Effects of using certain tree species in forest regeneration on volume growth, timber yield, and carbon stock of boreal forests in Finland under different CMIP5 projections

Abstract

We studied how the use of certain tree species in forest regeneration affected the volume growth, timber yield, and carbon stock of boreal forests in Finland under the current climate (1981-2010) and recent-generation global climate model (GCM) predictions (i.e., multi-model means and individual GCMs of CMIP5), using the representative concentration pathways RCP4.5 and RCP8.5 over the period 2010-2099. Forest ecosystem model simulations were conducted on upland national forest inventory plots throughout Finland. In a baseline management regime, forest regeneration was performed by planting the same tree species that was dominant before the final cut. In alternative management regimes, either Scots pine, Norway spruce or silver birch were planted on mediumfertility sites. Other management actions over rotation were done as in a baseline management. Compared to baseline management, an increased planting of birch resulted in relative sense highest increase in the volume growth, timber yield, and carbon stock in forests in the south, especially under severe climate projections (e.g., multi-model mean RCP8.5, and GCMs such as HadGEM2-ES RCP8.5 and GFDL-CM3 RCP8.5). This situation was opposite for Norway spruce. In the north, the volume growth, timber yield, and carbon stock of forests increased the most under severe climate projections (e.g., multi-model mean RCP8.5 and CNRM-CM5 RCP8.5), regardless of tree species preference. The magnitude of the climate change impacts depended largely on the geographical region and the severity of the climate projection. Increasing the cultivation of birch and Scots pine, as opposed to Norway spruce, could be recommended for the south. In the north, all three species could be cultivated, regardless of the severity of climate change.

Effects of using certain tree species in forest regeneration on regional wind damage risks in Finnish boreal forests under different CMIP5 projections

“…The responses of forests to climate change may differ greatly at the regional level. This is related to differences in the prevailing environmental conditions (climate, site), current forest structure (age, species) and forest management regimes (Bergh et al 2003;Briceño-Elizondo et al 2006;Garcia-Gonzalo et al 2007;Kellomäki et al 2008;Lindner et al 2010;Alrahahleh et al 2018). Particularly under severe climate warming, the growth and success of Norway spruce are expected to decrease in Finland, especially on southern upland forest sites, if the growing conditions (temperature and water availability) become suboptimal for its growth (Briceño-Elizondo et al 2006;Jyske et al 2010;Kellomäki et al 2018;Ruosteenoja et al 2018).…”

“…At the same time, they predict a slight to moderate increase in precipitation in the north, but only a slight increase (GFDL-CM3 RCP8.5), or a decrease (HadGEM2-ES RCP8.5), in precipitation in the south. Under such severe climate change outlooks, an increased cultivation of Norway spruce may decrease the growth and volume of growing stock, especially under southern boreal conditions, more than predicted, based on the multi-model means of the GCMs (Alrahahleh et al 2018). Consequently, the severe climate projections (HadGEM2-ES RCP8.5 and GFDL-CM3 RCP8.5) may affect the wind damage risk even more than the tree species preferences in forest regeneration, which should be considered in forest management decision making.…”

“…Depending on the severity of the climate change projection, radically different adaptive measures for forestry might be useful. For example, Norway spruce could grow well on certain sites under less severe climate projections and thus would be preferred in forest regeneration, but this would not be the case for more severe climate projections (Alrahahleh et al 2018). Therefore, the use of different individual GCM projections under RCPs is required in considering the uncertainties in the model predictions for forest growth and dynamics and consequently for the wind damage risks to forests.…”

“…This is needed in order to properly adapt forest management to climate change. The forest ecosystem models, together with up-to-date information on current forest resources, and different climate projections offer a means of predicting forest growth and dynamics under changing management regimes and environmental conditions, respectively (Garcia-Gonzalo et al 2007;Seidl and Lexer 2013;Alrahahleh et al 2017Alrahahleh et al , 2018Reyer et al 2017). The use of the simulated outputs of forest ecosystem models as inputs for mechanistic wind damage models also offers a means of predicting the threshold wind speeds needed for wind damage to forests and, consequently, their probabilities and the amount of damage to expect (Gardiner et al 2008;Peltola et al 2010;Seidl et al 2014;Ikonen et al 2017).…”

“…In addition, we expected that very severe climate change projections could affect the wind damage risk to a greater degree than tree species preferences in forest regeneration. The same simulation layout was recently used by Alrahahleh et al (2018), who studied how the use of certain tree species in forest regeneration affected the volume growth, timber yield and carbon stock of boreal forests in Finland under different CMIP5 projections.…”