Catastrophic shifts in tree-microbial symbioses: the causes, consequences, and warning signs of environmental collapse in the global forest system

The distribution of life on earth is shaped by climate. Moving north or south from the earth's equator to its polar caps, the sequence of ecosystems spans moist rainforests, dry deserts, seasonally green temperate forests and the vast evergreen forests and frozen tundra. Life in each of these ecosystems is adapted to the challenges that climate imposes, from the extremes of heat and cold that must be survived to the regular cycles of resources that must be exploited. As the earth's climate is changing at unprecedented speed, this regular sequence of ecosystems is being massively reorganised. As a NERC Independent Research Fellow, I propose to study how climate warming is driving transformative changes in the world's largest forested region over decades and centuries, fast enough to witness over the scale of individual human lifetimes.
My research indicates that hundreds of billions of trees that span the earth's great northern forests are living on the edge of a climatic tipping point. Tipping points occur when alternative ecosystem types engage in a tug-of-war with their environments, with each ecosystem altering local conditions in a way that allows it to survive. This tug-of-war can create an unstable frontier between warring ecosystems, where small climate changes can rapidly and irreversibly determine the winner. The technical term for these changes in ecosystem state is catastrophic ecosystem shifts; collectively, they represent the most dramatic planetary response to climate change.
The tipping point my research has unmasked is massive, stretching from North America clear across Eurasia, encompassing an area roughly twice the size of Europe. It separates forests that are dominated by trees that form symbiotic partnership with different groups of fungi (called mycorrhizas). Over 99% of trees associate exclusively with one of two primary groups of mycorrhiza to acquire the soil nutrients they require to grow and reproduce. Ectomycorrhizas dominate on the colder side of the tipping point where nutrient cycling is slow, in the vast boreal forests of Canada and Eurasia, whereas arbuscular mycorrhizas dominate on the warmer side where nutrient cycling is fast, in temperate and tropical forests. Moreover, these two groups appear locked in a tug of war on the process of nutrient cycling, with ecto- and arbuscular mycorrhizas slowing down and speeding it up, respectively, in an effort to transform their environments to their liking. Climate change is tipping the balance in this global tug-of-war, warming climates, speeding up nutrient cycling, and sending ectomycorrhizal trees and and their fungal partners beyond the tipping point where they can no longer thrive. If global forests follow the model set by other ecosystems engaged in such a tug of war, the transformations could occur much more rapidly than previously thought, occurring over the course of decades and centuries rather than thousands of years.
My objective is predict exactly how fast global forests will change as a result of climate change acting on this massive, ecological tug of war. Specifically, I will use global datasets comprising over 31 million forest census plots to build a mathematical model that can be used to determine the speed and consequences of catastrophic shifts in forest tree symbioses. These models will be used to predict catastrophic symbiotic shifts before they happen, identify warning signs of imminent ecosystem collapse, and forecast the resulting losses (and potential gains) in resulting ecosystem function. The resulting research will also help identify whether these ecosystem catastrophe's can be averted by reducing greenhouse gas emissions. The goal is to gain advance knowledge about the changing fates of our forests so that we can learn how to live them with them.