Deforestation, rising temperatures, drought, fire and other ecological disturbances are reducing forest cover on much of the earth, and compromising the ability of forests to supply important ecosystem services. Ecosystem management and ecological restoration are focused on preventing and repairing ecosystem degradation, but the rapidity and pervasiveness of these global transformations threaten to exceed our capacity to plan for or respond to them at sufficient spatiotemporal scales. In this chapter we focus on forests in two contrasting biomes – boreal and Mediterranean – that are anticipated to experience major ecological changes in the 21st century. The relatively species-poor boreal forest covers 11% of the earth's surface and exerts a major influence on the global climate. Mediterranean climate region (MCR) forests are highly fragmented and cover less than 0.5% of the earth's surface, but the MCR regions support nearly 1/5 of the world's flora. Forests in both biomes are dominated by stress-tolerant taxa, but the principal source of ecological stress is very different: low air and soil temperatures in the boreal region, and lack of soil moisture during the warm growing season in the MCRs. Projected climatic changes will ameliorate the central ecological stress in boreal forests, with rising temperatures and increasing precipitation leading to generally better growing conditions for trees. In the MCRs, projected climatic changes will exacerbate hydrological stress, as warming and projected decreases in growing-season soil moisture worsen the annual drought. Overall, the direct effects of climate change on tree survival and growth are likely to be positive in the boreal region and negative in the MCRs, but interactions between these climate drivers and other stressors – changes in precipitation type, fire and pest outbreaks, invasive species, and so on – will have important and potentially contrasting indirect effects on soils and the forests that grow in them. In both biomes the implications for forest composition, structure, function, dynamics and sustainability are profound. We examine how interactions between global change, soils and disturbance are likely to affect boreal and MCR forests, and what the implications of these effects may be for ecosystem management and ecological restoration. We describe general patterns of climate, vegetation, soils, human history, and disturbance ecology in the two biomes and we summarize climate trends and projected future conditions, with focus on effects to soils. We finish with biome-specific summaries of current restoration strategies and practices, and a consideration of how soil responses to global change-related stressors and disturbances might require changes in the way we plan for and implement forest management and restoration. Both boreal and MCR forests and their soils will experience major changes over the next 50–100 years. Adherence to the basic tenets of ecosystem management and ecological restoration will provide the best chance of conserving these forests and sustaining the ecosystem services they provide.
Developments in Soil Science, Volume 36, 2019.,