Resilience of European larch (Larix decidua Mill.) forests to wildfires in the western Alps

Abstract

European larch is a dominant species in the subalpine belt of the western Alps. Despite recent increases in wildfire activity in this region, fire ecology of European larch is poorly understood compared to other larch species around the world. This study aims to assess whether European larch forests are resilient to fires, and to find out the factors that drive such resilience. We assessed the recovery of larch forests along a gradient of fire severity (low, moderate, high) based on the abundance and dominance of post-fire larch regeneration. We established 200 plots distributed among burned larch forests in nine wildfires that occurred between 1973 and 2007 in the western Alps. We included variables regarding topography, climate, fire severity, fire legacies, ground cover, grazing intensity, and time since fire. To evaluate potential drivers of larch recruitment, we applied generalized linear mixed models (GLMM) and random forests (RF). Larch regeneration was much more abundant and dominant in the moderate- and high-severity fire classes than in the low-severity class. More than half of the plots in the moderate- and high-severity classes were classified as resilient, i.e., post-fire larch regeneration was enough to recover a larch stand. GLMM and RF produced complementary results: fire severity and legacies, such as snags, canopy cover and distance to seed source, were crucial factors explaining post-fire larch recruitment. This study shows that fire has a positive effect on larch regeneration, and we conclude that European larch forests are highly resilient to mixed-severity fires in the western Alp

Aridity and competition drive fire resistance trait covariation in mountain trees

“…, Moris et al. ), and fires are expected to increase in frequency and intensity with future warmer and drier conditions (Schumacher and Bugmann , Dupire et al. ).…”

“…Here, we aim to investigate patterns of variation of fire resistance traits from individuals to biogeographic regions across the wide climatic and vegetation gradients of the western Alps. Alpine forests are mostly prone to surface fires (Genries et al 2009, Moris et al 2017, and fires are expected to increase in frequency and intensity with future warmer and drier conditions (Schumacher andBugmann 2006, Dupire et al 2017). Paleoecological analyses have shown longterm differences in fire activity between species and plant communities in the Alps (Tinner et al 2000, Blarquez et al 2012.…”

Modeling anthropogenic and natural fire ignitions in an inner-alpine valley

“…In this study, lighting represented on average 33 % of all summer ignitions among those with a known cause and 38 % between June and August (comparable to other Alpine regions, e.g., 40 % in Austria; Müller et al, 2012). Such a high rate is indicative of the fact that summer fires in this study area can still be considered a partially "natural" disturbance regime, except for the fact that suppression policies are still quite aggressive and prevent a more complete restoration of fire as an agent potentially useful for regeneration and ecosystem functioning (Vazquez Moris et al, 2017). In turn, in the study area the frequency of lightning-induced fires is highly correlated with the summer Standardized Precipitation and Evaporation Index in Aosta (Castagneri et al, 2015) (R = 0.55 for all months between May and September and 0.69 for the month of July).…”

“…Historically, some ecosystems such as forests dominated by Scots pine or European larch might have evolved under medium-to high-frequency fire regimes (Vazquez Moris et al, 2017). However, the frequency and severity of fires have been heavily influenced by human activities, such as widespread pastoral fires and a century-long strict fire suppression policy.…”

reply to RC2 - nhess-2017-380

“…Moreover, forest management and human actions may strongly influence the spatiotemporal pattern of fire ignitions (DeWilde and Chapin, 2006), especially in highly developed regions such as southern Europe, where most of the wildland fires are human-induced. Here, several studies have shown the significance of the distance of forest fires to roads, settlements, and infrastructure or specific land uses or even its abandonment as predisposition for fire ignition (Vega-Garcia et al, 1995;Goldammer, 2003;Catry et al, 2009;Martinez et al, 2009).…”