Gradually increasing forest fire activity during the Holocene in the northern Ural region (Komi Republic, Russia)

Abstract

In many boreal regions of Russia the past natural variability of forest fire activity remains largely undocumented, preventing accurate assessment of the impact of current climate warming on forest ecosystem dynamics. This study aims to reconstruct the Holocene fire history of the northern Ural mountain foothills, in the Komi Republic, based on analyses of charcoal particles from peatland deposits and coupled with dendrochronological investigations. The results show that there was a gradual increase in forest fire activity during the past 11,000 years. Between 11,000 and 5100 cal. yr BP, the mean fire return interval (FRI) oscillated between 600 and 200 years. During this period, regional data showed that cold temperature, humid climatic conditions, combined with steppe vegetation between 11,000–9000 cal. BP, and then the development of spruce-dominated forest between 9300 and 4600 cal. yr BP, were less conducive to fires. After 5100 cal. yr BP, a gradual increase in drought conditions through reduced precipitations, associated with the establishment of a Scots pine forest favored fire frequency, with a mean FRI under 200 years (range, 200–40 years). Nowadays (since CE 1500), human activity induces an unprecedented fire activity with a mean FRI below 100 years (range, 100–40 years).

Wildfire history of the boreal forest of southwestern Yakutia (Siberia) over the last two millennia documented by a lake-sedimentary charcoal record

“…Although some studies draw a similar conclusion (e.g. Carcaillet et al, 2001 in eastern Canada), this result contrasts with many other studies from the Eurasian and North American boreal zones, where vegetation changes were found to be closely connected to changes in fire regimes (Barhoumi et al, 2019(Barhoumi et al, , 2020Feurdean et al, 2020;Gavin et al, 2007;Kelly et al, 2013). However, on a shorter, multidecadal timescale, phases with more Cyperaceae pollen (sedges) in the Lake Khamra record and a higher ratio of evergreen to deciduous arboreal pollen types coincide with periods of high fire activity in phases 2 and 4 (see Fig.…”

“…The reconstructed record-wide mean FRI of 43 yrs, incorporating both the exceptionally short FRI of phase 2 (14 yrs) and the long FRI of phase 3 (60 yrs, excluding the c. 600-yr-long period without identified fires), lies within the range of the few comparable studies in western Siberia. Barhoumi et al (2019) found the shortest FRIs of the Holocene ranging from 40-100 yrs between 1500 CE and present day in macroscopic charcoal records from the northern Ural region. A mean FRI of 45 yrs during recent centuries was inferred by Feurdean et al (2020).…”

“…A background component was determined by computing a locally estimated scatterplot smoothing (LOESS) at a window width of 25% of the total record length (package "locfit" v.1.5-9.4, function "locfit"; Loader et al, 2020). This window width was found to result in an efficient distribution of a signal-to-noise index (SNI) >3 after Kelly et al (2011), which indicates a high degree of separation between signal and noise (Barhoumi et al, 2019;Kelly et al, 2011). A peak component was created by subtracting the background component from the timeseries.…”

“…lists only a few continuously sampled macroscopic charcoal records across the Siberian boreal forest. Only recently 60 have charcoal records of sufficient temporal resolution allowed the assessment of fire return intervals in western Siberian evergreen forests and they reveal close fire-vegetation relationships (Barhoumi et al, 2019;Feurdean et al, 2020). More studies have been conducted in North America (e.g.…”

Did long‐term fire control the coniferous boreal forest composition of the northern Ural region (Komi Republic, Russia)?

“…At Yaksha, the three study sites did not show the same local recent fire activities when tree ring fire scars were analysed (Barhoumi et al, 2019). In Kuosmanen et al (2014)…”