Cool as a moose: How can browsing counteract climate warming effects across boreal forest ecosystems?

Area of Science:

• Ecology
• Climate Change Biology
• Forest Science

Background:

• Herbivory can alter vegetation responses to climate change, but its interactions with climate and other ecological factors like competition are complex.
• Predicting the net effect of herbivory (counteracting, amplifying, or interacting with climate impacts) on ecosystems remains challenging.

Purpose of the Study:

• To investigate how moose herbivory modifies the climatic responses of boreal trees across two continents.
• To model complex causal pathways involving climate factors, tree species, competition, and herbivore dynamics.

Main Methods:

• Utilized experimental exclosures on two continents to study moose-tree interactions.
• Employed modeling to analyze causal pathways including climate, tree species, competition, tree height, time, food availability, and herbivore metrics (presence, density, browsing intensity).

Main Results:

• Moose can counteract positive temperature responses in trees ('cooling effect'), with species-specific variation based on foraging preferences.
• Preferred deciduous trees were strongly impacted by moose, while less preferred conifers were more influenced by climate and tree height.
• Moose altered temperature responses of specific species (e.g., balsam fir more responsive, rowan less responsive) and indirect effects via competition were observed.

Conclusions:

• Moose 'cooling power' in boreal forests is highly context-dependent, influenced by species differences, snow cover, competition, and climate effects on browsing.
• Reduced snow cover in a warming climate may increase moose browsing impact.
• Understanding these multifaceted interactions is essential for predicting ecosystem responses to climate change.