Climate Change Effects on Terrestrial Ecosystem Processes: Plant-Fungal Interactions

Global climate projections by the year $2100$ include temperature increases between $1.1$ and $6.4\,^{\circ}\text{C}$ , shifting rainfall patterns, and more frequent extreme events.
Fungal responses to climate change are categorized as direct or indirect (mediated by plant interactions).
Essential ecosystem model components include decomposers, detritus, humus, and the plant, herbivore, and decomposer subsystems (Swift et al., 1979).

Fungal diseases are expanding their geographic range toward higher latitudes as agroclimatic zones shift poleward (Bebber et al., 2013).
Temperature is the critical factor affecting pathogen spread; specific extreme minimum temperatures can be more impactful than monthly averages (Watkinson et al., 2015).
Elevated temperatures lead to faster germination, increased growth rates, and more reproductive life cycles per year.
High moisture and relative humidity levels generally favor infection, sporulation, and spore germination, except for pathogens adapted to hot, dry environments like $Ustilago$ .
Survival of plant debris-borne fungi is promoted by milder, wetter winters, while warmer, drier summers typically decrease pathogen threats.

Wheat: Rust ( $Puccinia\ striiformis$ ) increases with temperature; Crown rot ( $Fusarium\ pseudograminearum$ ) biomass increases with elevated $CO_2$ .
Rice: Rice blast ( $Magnaporthae\ oryzae$ ) severity increases with elevated $CO_2$ .
Barley & Maize: Powdery mildew ( $Blumeria\ graminis$ ) and Smut ( $Ustilago\ maydis$ ) severity decreases with elevated $CO_2$ .
Potato: Late blight ( $P.\ infestans$ ) predictions vary, with significant increases projected for Finland.
Pathogen spectra are shifting, such as the movement from stripe rust to leaf rust or the appearance of new pathogens like $Verticillium\ longisporum$ in oilseed rape.

Distribution of mycorrhizal fungi shifts with host vegetation; in the Santa Rosa mountains, White fir ( $Abies\ concolor$ ) and Jeffrey pine ( $Pinus\ jeffreyi$ ) moved upward by $96\,m$ and $28\,m$ respectively over $30\,yr$ .
Elevated $CO_2$ increases photosynthesis, driving higher mycorrhizal abundance: Ectomycorrhizas (ECM) increase by an average of $19\%$ and Arbuscular Mycorrhizas (AM) by $84\%$ .
Increased carbon inputs to soil result in higher soil respiration and a community shift toward long-range foraging fungi.
In Tundra ecosystems, warming results in increased shrub biomass but decreased cover of mosses and lichens.
Altitudinal gradients model latitudinal shifts: ECM species richness and diversity decrease as altitude increases, as seen in the Canadian Rocky mountains.