Net Climate Effects of Moose Browsing in Early Successional Boreal Forests by Integrating Carbon and Albedo Dynamics. Issue 3 (3rd March 2023)

• Record Type: Journal Article
• Authors: Salisbury, John; Hu, Xiangping; Speed, James D. M.; Iordan, Cristina Maria; Austrheim, Gunnar; Cherubini, Francesco
• Is Part Of: Journal of geophysical research. Volume 128:Issue 3(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-03-03
• Subjects: forest management -- wild herbivores -- climate change -- albedo; Geobiology -- Periodicals; Biogeochemistry -- Periodicals; Biotic communities -- Periodicals; Geophysics -- Periodicals; 577.14
• DOI: 10.1029/2022JG007279
• Languages: English
• ISSNs: 2169-8953

Abstract

Abstract: Moose ( Alces alces ) is a large herbivore that can mediate boreal forest regeneration after timber harvest through selective browsing of tree species. Despite increasing evidence of moose browsing influence on tree growth in early successional forests, climate effects due to changes in carbon sequestration rates and biophysical factors such as albedo remain largely unexplored. We used 11 years of data from 44 pair‐sites of herbivore exclosures within clear‐cut forests in Norway to investigate how moose browsing alters aboveground tree biomass and albedo. We find a higher total aboveground tree biomass (mainly deciduous species) in unbrowsed than browsed forest plots, as moose browsing limited the growth of tree biomass. The effect of moose exclosure on relative tree abundances differed between sites, suggesting that moose browsing has stronger effects on forest structure than composition. At the same time, moose increased forest albedo relative to un‐browsed forests, driving biophysical cooling. When averaged at regional levels, climate effects due to changes in biomass and albedo are of similar magnitude, but contributions can diverge in specific locations. In a region with intensive forestry operations and high moose density, CO2 emissions from moose browsing in post‐harvested sites can be equal to about 40% of the annual emissions of fossil fuels from that region. Cooling effects from increased albedo can offset about two thirds of this impact. Given its influence on tree growth rates and climate impacts, management of moose browsing density should be integrated into forest management plans to optimize climate change mitigation and forest productivity. Plain Language Summary: Moose play a key role in shaping landscape structure and forest composition. For example, moose influence vegetation and soils via foraging, trampling, and nutrient cycling, thereby affecting tree growth rate, community composition, and ecosystem carbon budget. It is estimated that moose alone can browse 10% of the annual harvest volume in Norway. Moose also alter land cover properties such as surface albedo (i.e., the fraction of reflected solar energy radiation), with direct implications for the climate. A better knowledge of the interactions of the climate‐forest‐moose nexus can help the identification of integrated management of forest resources and wild herbivores that maximize climate change mitigation benefits and ecosystem services, including timber value. Our study analyzed 11 years of empirical field measurements from 44 post‐harvest sites in Norway to study climate impacts from both carbon sequestration and albedo dynamics induced by moose browsing. We found that moose browsing cools the climate by increasing surface albedo and warms the climate by limiting forest carbon sequestration. The two effects tend to compensate for each other, but there are large regional variations. Given the potential effects on both tree growth and the climate, moose browsing should be more actively integrated into forest management plans. Key Points: Field data are used to study the effects of moose on forest albedo and carbon dynamics Moose browsing contributes to warming by limiting carbon sequestration, but exerts a cooling effect by increasing surface albedo The two effects have the same order of magnitude, but vary regionally, and forest management practices should consider these effects