1.09.00 - Ecology and silviculture of mixed forests
The Research Group on ecology and silviculture of mixed forests will be a multidisciplinary team of researchers spanning from forestry, ecology and social sciences aimed (1) to disentangle the mechanisms behind the dynamics of mixed forests, (2) to respond to the Social needs from forests, i.e. increasing demand of multiple ecosystem services, (3) to orientate management of mixed forests based on scientific evidence. The research group will interact with other units within Divison 1 and across all Divisions.
Silviculture is continually facing challenges. Successful regeneration, provision of products and services and restoration of degraded lands have been historically the drivers of the advancement of Forestry. Nowadays, those challenges continue to be important but new ones have appeared. Loss of diversity due and excessive over-simplification of forest structures, climate change and increasing demand of ecosystem services from Society has moved the balance between from single-species to mixed-stands putting sometimes Forestry on the fence.
The concerns about the possible negative consequences of current biotic and abiotic risks for forest resilience have suggested adopting strategies towards alternative management regimes (Puettmann et al. 2015), close-to-nature (Bauhus et al. 2013), climate-smart forestry (Nabuurs et al. 2015) or species-rich forest management options (Bravo-Oviedo 2018) as a response to changes in social attitudes towards forests, their products and services.
Liang et al. (2016) concluded that forests with higher tree species richness are more productive based on a positive biodiversity-productivity relationship at a global scale whereas Gamfeldt et al. (2013) found higher levels of multiple ecosystem services in mixed stands. However, a positive relationship between biodiversity and multifunctionality depends on the level of functionality assessed (van der Plas et al. 2016).
The interest in complex forest compositions and structures has led to studies on the performance of mixed- versus pure stands but many are hampered by proper experimental designs, protocols or data quality (Binkley et al. 2017; Ruiz-Peinado et al. 2018). One exception is the triplet approach (Heym et al. 2017) where studies on yield and growth have demonstrated overyielding in mixed stands (Pretzsch et al. 2015b; Pretzsch 2018) likely due to higher light interception and complementary effects (Forrester et al. 2017) and with more temporal stability in terms of basal area growth (del Rio et al. 2017). However, the triplet approach is still adopted at a regional scale and upscaling to global mixed forests would require further research on site and species identity effects and the role of functional diversity in the generation of multiple ecosystem services.
There has been some attempts to summarize and compile the research conducted on mixed forests (Kelty et al. 1992; Olsthoorn et al. 1999; Pretzsch et al. 2017; Bravo-Oviedo et al. 2018) but the adoption of a true mixed-species silviculture is lacking due to the difficulty to simulate mixing effects at multiple processes (Pretzsch et al. 2015a). The increasing evidence of the superior performance of mixed forests calls for a design of mixed-species stands and advanced silvicultural prescriptions (Bauhus et al. 2017; Pretzsch and Zenner 2017) that still needs to be further developed.