Warmer temperatures promote shrub radial growth but not cover in the central Canadian Arctic

Abstract

We assessed the response of Salix richardsonii, a deciduous shrub, to climate change by determining the combination of climatic factors that regulated its growth over the past half-century. We tested whether increasing arctic temperatures promote shrub growth and increased cover. We analyzed fifty-four stems (out of seventy sampled) from S. richardsonii shrubs near the Walker Bay research station in Nunavut, Canada (68°21′ N, 108°05′ W) and surveyed shrub cover in 1996 and 2010. We measured annual growth rings, removed the age-related pattern, and used a response function analysis to explore the climate-growth relationship. The standardized chronology was positively associated with mean July temperature, corroborating other evidence that summer temperature is an important driver of shrub radial growth. Basal area increment revealed a longterm increase in radial growth, although it has stabilized this century. Surveys showed no significant increase in shrub cover at Walker Bay from 1996 to 2010. Our results support a growing body of evidence that increased shrub growth does not necessarily translate into a prolonged increase in shrub cover. Instead, we conclude that the heterogeneity of the arctic shrub response to climate change may be associated with variation in the proximate factors limiting recruitment such as water table saturation and herbivory.

Increases in graminoids after three decades of change in the High Arctic

“…2)-reiterates patterns elsewhere in the High Arctic (Elmendorf, Henry, Hollister, Björk, Boulanger-Lapointe et al 2012;Kapfer & Grytnes 2017;cf. Hill & Henry 2011), as well as at Walker Bay, 140 km to the south-west (Buchkowski et al 2020). Declines in mosses-in my study, manifest in both cover and frequency, albeit marginally significant (Table 1)-is another widespread trend (Elmendorf, Henry, Hollister, Björk, Bjorkman et al 2012;Elmendorf, Henry, Hollister, Björk, Boulanger-Lapointe et al 2012;Bjorkman et al 2020).…”

“…On south-eastern Victoria Island, a region undergoing rapid climate change (Panchen 2016;Bush & Lemmen 2019;Buchkowski et al 2020), I discovered pronounced shifts in vegetation after three decades: a marked increase in graminoids, along with substantial declines in Dryas integrifolia, Polygonum viviparum and Saxifraga oppositifolia (Table 1, Figs. 2, 5).…”

“…Since the late 1940s, temperatures have risen substantially in the nearby community of Cambridge Bay, 60 km to the south-east-by 0.30 C°/decade in mean July temperature (Panchen 2016;Buchkowski et al 2020) and by 0.40 C°/decade in mean annual temperature (Buchkowski et al 2020). Since 1960, winter snow depth has increased by 1.1 cm/decade (Lam et al 2022).…”

The Use of Basal Area Increment to Preserve the Multi-Decadal Climatic Signal in Shrub Growth Ring Chronologies: A Case Study of Betula glandulosa in a Rapidly Warming Environment

“…Moreover, based on the results of Baral et al [40], who demonstrated that climate-tree growth relationships were stronger when using BAI rather than standardized RW in short chronologies, we believe that the use of BAI might be of high interest when analyzing shrub species' growth rings. Indeed, even though BAI measurement has been used mainly with trees, it remains only marginally used for shrub species [22,23,[41][42][43].…”

“…A secondary objective was to determine if BAI estimations (i.e., calculated from raw ring width measurements) are correlated with the actual measurements of BAI (i.e., measured on scanned cross-sections using image analysis) for B. glandulosa. Indeed, both approaches have been used in previous studies but have never been compared (calculated: [37,40,42]; measured: [22,41]). Calculating BAI from RW measurements is significantly faster, but might generate inaccurate values in the presence of eccentric growth forms or irregular rings [23].…”