Potential climate-induced distributions of <i>Lophodermium</i> needle cast across central Siberia in the 21 century

Needle cast caused by fungi of the genus Lophodermium Chevall. is a common disease in pine trees in Siberia. Regression analyses relating needle cast events to climatic variables in 1997–2010 showed that the disease depended most on precipitation of two successive years. Temperature conditions were important to trigger the disease in wetter years. We used our regional bioclimatic envelope model and IPCC scenarios to model the needle cast distribution and its outbreaks in the 21st century. In a warming climate, the needle cast range would shift northwards. By 2020, needle cast outbreaks would already have damaged the largest forest areas. But outbreak areas would decrease by 2080 because the ranges of modeled pathogen and Scots pine, the disease host, would separate: the host tree progression would be halted by the slower permafrost retreat, which would in turn halt the potential pathogen progression.

Forest forecasting with vegetation models across Russia

Vegetation models are essential tools for projecting large-scale land-cover response to changing climate, which is expected to alter the distribution of biomes and individual species. A large-scale bioclimatic envelope model (RuBCliM) and an individual species based gap model (UVAFME) are used to simulate the Russian forests under current and future climate for two greenhouse gas emissions scenarios. Results for current conditions are compared between models and assessed against two independent maps of Russian forest biomes and dominant tree species. Comparisons measured with kappa statistics indicate good agreement between the models (kappa values from 0.76 to 0.69), as well as between the model results and two observation-based maps for both species presence and absence (kappa values from 0.70 to 0.43). Agreement between these multiple types of data on forest distribution provides confidence in the projected forest response to changing climate. For future conditions, both models indicate a shift in the dominant biomes from conifers to deciduous leaved species. These projections have implications for feedbacks between the energy budget, carbon cycle, and land cover in the boreal system. The distinct biome and species changes emphasize the need for continued investigation of this landmass that has the size necessary to influence regional and global climate.

Potential effects of climate change on ecosystem distribution in Alberta

We propose a new and relatively simple modification to extend the utility of bioclimatic envelope models for land-use planning and adaptation under climate change. In our approach, the trajectory of vegetation change is set by a bioclimatic envelope model, but the rate of transition is determined by a disturbance model. We used this new approach to explore potential changes in the distribution of ecosystems in Alberta, Canada, under alternative climate and disturbance scenarios. The disturbance model slowed the rate of ecosystem transition, relative to the raw projections of the bioclimatic envelope model. But even with these transition lags in place, a northward shift of grasslands into much of the existing parkland occurred over the 50 years of our simulation. There was also a conversion of 12%–21% of Alberta’s boreal region to parkland. In addition to aspatial projections, our simulations provide testable predictions about where ecosystem changes as a result of climate change are most likely to be initially observed. We also conducted an investigation of model uncertainty that provides an indication of the robustness of our findings and identifies fruitful avenues for future research.