Why Douglas-fir trees?
Interior Douglas-fir forests were chosen for this research due to their large range in British Columbia and their commercial importance. These forests have become a recent harvesting focus in British Columbia as mountain pine beetle salvage has ended so it is critical to know how to manage them. Unlike the beetle-killed forests, clearcutting is not appropriate in many interior Douglas-fir forests because of their uneven-aged structure and arid climate. Many of today’s practicing foresters have little knowledge to draw on regarding interior Douglas-fir management, because it has been several decades since they have been harvested on a large scale. Many foresters who managed these forests in the past have now retired, and the outcomes of different treatments were poorly documented. Interior Douglas-fir is one of the species of trees most sensitive to climate change. Successful establishment and growth of the species depends on adequate soil moisture, which at the present time is already limited in summer on many sites where it grows. Water availability will become an increasing limitation to Douglas-fir establishment and growth if projected increases in summer temperature occur, which will increase evaporation and exacerbate soil moisture limitations resulting from increasingly drier summers.
Why Mother Trees?
Mother Trees were considered when developing harvesting treatments because past research has shown that they can help seedlings regenerate, reduce losses of carbon and biodiversity from the ecosystems, and can play an important role in connecting trees in the forest through mycorrhizal networks. Mother Tree research sites have been established across a climate gradient in a “space-for-time” approach, where the range of current forest ecosystem conditions across regional climates is used as a proxy for predicting responses as climate changes over time. In this way, the Mother Tree Project can provide essential information on how to increase regeneration success as climate changes. Clearcut and partially logged sites are being regenerated with a range of species, grown from both local and migrated seed sources. Regeneration using a range of such seed genotypes are being studied by scientists in clearcuts, but not on partially cut sites.