Improving PREdictability of circumboREAL forest fire activity and its ecological and socio-economic impacts through multi-proxy data compari

Informations

Funding country

Norway

Acronym

-

URL

-

Start date

1/1/2016

End date

12/31/2021

Budget

354,117 EUR

Fundings

Abstract

The ability to predict forest fire activity is critical to mitigate its impacts, including fire- and climate-driven dynamics of ecosystem and socio-economic services. Climate and fire are primary driving factors of ecosystem dynamics in the boreal forest, directly affecting global carbon balance and atmospheric concentrations of trace gases including carbon dioxide. Resilience of ocean-atmosphere system provides potential for detection of upcoming fire season intensity. Joint analyses of historical fire proxies (fire scars on trees and charcoal in lake sediments) with independently obtained proxies of climate variability, climate-growth relations, and vegetation cover should contribute towards better knowledge of modern climate drivers of forest fires and predictability of fire activity at multiple temporal scales. PREREAL is an international project focusing on identification of drivers controlling boreal fire activity, and its predictability by relying on analyses of multiple metrics of modern and historic fire activity, forest growth, forest cover, and climate-ocean variability. The project also aims to provide decadal and century-scale predictions of future fire activity and translate these into impacts on ecosystem services. The Norwegian part of PREREAL has special focus on the North Atlantic region and on 1) climate-tree growth variability, 2) forest cover change, and 3) climate-ocean variability. Main results 1: Climate change modulates boreal forest ecosystems through changing growth constraints. Understanding spatiotemporal variations in climate?growth relationships is essential to project forest ecosystem dynamics, and climate?environmental feedbacks. We analysed this matter in three different studies. All three revealed spatiotemporally unstable growth responses to climate. Consequently, projections of future forest ecosystem dynamics based on climate variables identified during specific periods and for specific areas may be misleading. Results from Northern Norway show that a wide range of growing season and non-growing season climate variables limited growth during the early twentieth century. Thereafter the number of growth-limiting variables have progressively decreased. At the eastern side of the North Atlantic a proposed strengthening of moisture control over tree growth in recent decades was revealed insignificant. Meaning that despite climate warming forest growth has remained temperature-limited. However, a weakening of the influence of growing season temperature on growth during the mid- to late twentieth century was shown. In the third study we in addition tested local coherency between tree growth proxies (diameter, height, NDVI) which in generally showed to be insignificant. This lack of local coherency suggests that forest growth estimates based on a single proxy should be considered with great caution. 2: Recent climate warming and scenarios for further warming have led to expectations of rapid movement of ecological boundaries. The transition zone between the boreal forest and Arctic tundra (forest-tundra ecotone, FTE) is one such boundary and that represents an important bioclimatic zone with feedbacks from forest advance and corresponding tundra disappearance (up to 50% tundra loss is predicted for the 21st century) driving widespread ecological and climatic changes. By using FTE movement data from >150 sites across the circumarctic area a strong discrepancy was revealed between ground-based findings and commonly used predictions both regarding rate of advance and climate variables driving the change. Advance rates were in general 1?2 orders of magnitude smaller than predicted values, and importance of precipitation rather than temperature was highlighted. Biotic and abiotic factors (including forest fire) influencing FTE behaviour make poleward advance rates matching predicted 21st century climate changes unlikely. In addition, we successfully tested and suggests a new remote sensing method for delineation of FTE. Accurate mapping of FTE is challenging, and delineation products that can serve as the basis of time series analyses has so far been lacking. 3: The mid-20th century changes in North Atlantic Ocean dynamics have been considered early signs of climate tipping points. The circulation strength of the North Atlantic subpolar gyre varies on a range of timescales, it regulates the northwards oceanic heat transport and influences weather and climate over Scandinavia. In one of our studies we demonstrate a linear relationship between atmospheric blocking events and records of forest fires from northern Scandinavia for the period since 1948 until today. Clustering methodology is successfully used in identifying the dominating weather patterns over Scandinavia. However, and despite promising indications from the literature, forest fires and atmospheric blockings are not consistently coupled to anomalies in the North Atlantic subpolar gyre dynamics.