Globally consistent climate sensitivity of natural disturbances across boreal and temperate forest ecosystems

Abstract

Disturbance regimes are changing in forests across the world in response to global climate change. Despite the profound impacts of disturbances on ecosystem services and biodiversity, assessments of disturbances at the global scale remain scarce. Here, we analyzed natural disturbances in boreal and temperate forest ecosystems for the period 2001–2014, aiming to 1) quantify their within‐ and between‐biome variation and 2) compare the climate sensitivity of disturbances across biomes. We studied 103 unmanaged forest landscapes with a total land area of 28.2 × 106 ha, distributed across five continents. A consistent and comprehensive quantification of disturbances was derived by combining satellite‐based disturbance maps with local expert knowledge of disturbance agents. We used Gaussian finite mixture models to identify clusters of landscapes with similar disturbance activity as indicated by the percent forest area disturbed as well as the size, edge density and perimeter–area‐ratio of disturbed patches. The climate sensitivity of disturbances was analyzed using Bayesian generalized linear mixed effect models and a globally consistent climate dataset. Within‐biome variation in natural disturbances was high in both boreal and temperate biomes, and disturbance patterns did not vary systematically with latitude or biome. The emergent clusters of disturbance activity in the boreal zone were similar to those in the temperate zone, but boreal landscapes were more likely to experience high disturbance activity than their temperate counterparts. Across both biomes high disturbance activity was particularly associated with wildfire, and was consistently linked to years with warmer and drier than average conditions. Natural disturbances are a key driver of variability in boreal and temperate forest ecosystems, with high similarity in the disturbance patterns between both biomes. The universally high climate sensitivity of disturbances across boreal and temperate ecosystems indicates that future climate change could substantially increase disturbance activity.

Excess forest mortality is consistently linked to drought across Europe

“…While droughts in general and hotter droughts in particular can trigger mortality directly, it is most likely the combined effect of drought and secondary mortality agents that led to the tree mortality hotspots identified in this study. One of the most important mortality agents in terms of hotter droughts is fire [12][13][14][15] . For example, the year 2005 marks one of the most severe fire seasons on the Iberian Peninsula in recent decades 40 , explaining the significant hotspot of drought-related tree mortality identified in our analysis in the same year across the western Iberian peninsula (Fig.…”

“…While drought can impair photosynthesis and directly trigger mortality through carbon starvation and hydraulic failure 3 , it is most often the combined effect of drought and secondary mortality agents that causes large-scale pulses of tree mortality [4][5][6] . In particular, hotter droughts are an inciting factor of tree mortality from insects [6][7][8][9][10][11] and may further increase the size and intensity of forest fires [12][13][14][15] . As droughts are predicted to become more frequent and more intense under climate change 16,17 , concerns have been raised whether forest ecosystems might become increasingly susceptible to drought-induced ecosystem collapse [18][19][20] .…”

Maintaining natural and traditional cultural green infrastructures across Europe: learning from historic and current landscape transformations

“…Finally, there is (4) intensive even-aged forest management (Sweden S). Potential natural forest vegetation types, including a wide range of developing stages after locally and regionally typical natural disturbances (Seidl et al 2020), represent important visions for functionally connected and representative GIs (see CBD 2010). Primary or primeval forests are naturally regenerated forests of native species where there are no clearly visible indications of human impacts and where ecological processes are not significantly disturbed (FAO 2015).…”

Charcoal ecology: Its function as a hub for plant succession and soil nutrient cycling in boreal forests

“…Forest disturbances, especially fires, are sensitive to climate conditions; thus, disturbance regimes are predicted to change due to accelerated warming and drying climates in boreal forests (Johnstone et al, 2016; Seidl et al, 2020). Boreal forests are high‐latitude forests in which the length of the season with subzero temperatures is 6–8 months and in which trees are 5 m in height at a minimum and the canopy cover is 10% (Gauthier, Bernier, Kuuluvainen, Shvidenko, & Schepaschenko, 2015).…”

“…Globally, this amount represents approximately 49% of the global total of forest C stocks (Dixon et al, 1994). In boreal forests, fire is the major disturbance agent (Seidl et al, 2020). Historically, severe crown fire was the most common form of fire in North America, while surface fire was the dominant form in Scandinavia and Russia (Gauthier et al, 2015; Makoto, Nemilostiv, et al, 2007).…”