Winter precipitation - not summer temperature - is still the main driver for Alpine shrub growth

Carrer, Marco; Pellizzari, Elena; Prendin, Angela Luisa; Pividori, Mario; Brunetti, Michele

doi:10.1016/j.scitotenv.2019.05.152

Cited by 53 publications

(54 citation statements)

References 56 publications

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“…A similar positive effect of increased growing season length and/or temperature has been found at many northern and high‐elevation locations worldwide (Forbes et al., ; Blok et al., ; Pellizzari et al., ; Myers‐Smith et al., 2015a), where plant growth is temperature limited (Körner, ; Wipf, ; Wheeler et al., ). The negative correlations between radial growth, melt‐out timing and winter snowfalls observed in the BCF profiles at QW and QN are congruent with other dendroecological studies carried out in the Alps (Pellizzari et al., ; Francon et al., ; Carrer et al., ). Our results differ from most Arctic studies, however, where the positive effect of snowpack on shrub growth (Zalatan and Gajewski, ; Hallinger et al., ; Hollesen et al., ; Ropars et al., ) has been attributed to its thermal insulation effect (Chapin et al., ; Sturm et al., ; Hallinger et al., ).…”

Section: Discussionsupporting

confidence: 90%

“…In the western Italian Alps, by contrast, Carrer et al. () described a positive association between dwarf juniper growth and summer precipitation but did not report any significant effect of summer temperature on ring width.…”

Section: Discussionmentioning

confidence: 91%

“…In comparison, only a handful of chronologies have been constructed so far for shrubs in alpine regions (e.g., Liang and Eckstein, ; Franklin, ; Lu et al., ). Dendroecological studies carried out in the European Alps hitherto identified that increasing summer temperatures and earlier snow melt‐out dates would have a positive effect on shrub growth (Pellizzari et al., ; Francon et al., ; Carrer et al., ). By contrast, in the Mediterranean mountain ranges of southeastern Spain, juniper shrubs were shown to experience a change in their main limiting factors, shifting from temperature and growing season length to water availability (García‐Cervigón et al., ).…”

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confidence: 99%

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Some (do not) like it hot: shrub growth is hampered by heat and drought at the alpine treeline in recent decades

Francon

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Till–Bottraud

et al. 2020

American J of Botany

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PREMISE:Mountain ecosystems are particularly sensitive to climate change. However, only a very small number of studies exist so far using annually resolved records of alpine plant growth spanning the past century. Here we aimed to identify the effects of heat waves and drought, driven by global warming, on annual radial growth of Rhododendron ferrugineum. METHODS:We constructed two century-long shrub ring-width chronologies from R. ferrugineum individuals on two adjacent, north-and west-facing slopes in the southern French Alps. We analyzed available meteorological data (temperature, precipitation and drought) over the period 1960-2016. Climate-growth relationships were evaluated using bootstrapped correlation functions and structural equation models to identify the effects of rising temperature on shrub growth. RESULTS: Analysis of meteorological variables during 1960-2016 revealed a shift in the late 1980s when heat waves and drought increased in intensity and frequency. In response to these extreme climate events, shrubs have experienced significant changes in their main limiting factors. Between 1960 and 1988, radial growth on both slopes was strongly controlled by the sum of growing degree days during the snow free period. Between 1989 and 2016, August temperature and drought have emerged as the most important. CONCLUSIONS: Increasing air temperatures have caused a shift in the growth response of shrubs to climate. The recently observed negative effect of high summer temperature and drought on shrub growth can, however, be buffered by topographic variability, supporting the macro-and microrefugia hypotheses.

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Section: Discussionsupporting

confidence: 90%

Section: Discussionmentioning

confidence: 91%

mentioning

confidence: 99%

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Some (do not) like it hot: shrub growth is hampered by heat and drought at the alpine treeline in recent decades

Francon

Corona

Till–Bottraud

et al. 2020

American J of Botany

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“…Our results are in line with numerous studies from Arctic and Alpine environments, which demonstrated that the accumulation of temperature above a certain threshold is a key factor driving growth through cell division and differentiation (Hoch, 2015;Körner, 2003;Wheeler et al, 2016;Wipf, 2010) and phenological transitions (Kudo and Suzuki, 1999;Molau et al, 2005). Results are also consistent with (i) dendrochronological studies that demonstrated the negative effect of snowpack duration on radial growth at the upper shrub limit in the Alps (Carrer et al, 2019;Francon et al, 2017;Pellizzari et al, 2014) and (ii) manipulation experiments (Stinson, 2005;Wheeler et al, 2016) showing increased productivity in case of artificial snow removal at sites where melt-out dates occurred after late-May (Wipf and Rixen, 2010). Results from the Alps differ from the wealth of studies in the Arctic, where a positive effect of snowpack was highlighted.…”

Section: Radial Growth Responses Along the Snow Melt-out Timing Gradientsupporting

confidence: 92%

“…Still underused in high-altitude environments, the limited number of existing dendroecological studies tends to confirm that dwarf shrub productivity is influenced by interannual variations of growing season temperature (Francon et al, 2017;Franklin, 2013;Liang et al, 2012;Liang and Eckstein, 2009;Lu et al, 2015;Pellizzari et al, 2014). In the Alps, initial results point to a negative effect of winter precipitation on the radial growth of shrubs (Carrer et al, 2019;Francon et al, 2017;Pellizzari et al, 2014;Rixen et al, 2010), a phenomenon that has been observed only rarely in circum-Arctic tundra ecosystems (Bär et al, 2008;Hallinger et al, 2010;Ropars et al, 2015;Zalatan and Gajewski, 2006;but see Schmidt et al, 2010, who found snow to correlate negatively with Salix arctica growth). Several hypotheses have been proposed to explain this phenomenon, such as the detrimental effect of late-persisting snow on the onset of cambial activity, growing season length or soil temperatures (Pellizzari et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

Assessing the effects of earlier snow melt-out on alpine shrub growth: The sooner the better?

Francon

Corona

Till–Bottraud

et al. 2020

Ecological Indicators

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Enhanced shrub growth in a warming alpine climate has potential far-reaching implications, including soil nutrient cycling, carbon storage, or water and surface energy exchanges. Growth ring analysis can yield mid-to long-term, annually resolved records of shrub growth, and thereby offer valuable insights into how growth is driven by interannual climate variability. In the European Alps, dendroecological approaches have shown that dwarf shrub productivity is influenced by interannual variations of growing season temperature but results also point to a negative effect of winter precipitation on radial growth. However, as past work lacked snow cover data, links between snow cover duration, growing season length, energy availability and inter-annual shrub growth remain poorly understood. In this paper, we combined multi-decadal shrub-ring series from 49 individuals sampled at three sites along a 600-m elevational gradient in the Taillefer massif, located in the French Alps to assess growth sensitivity of long-lived and widespread Rhododendron ferrugineum shrubs to 2 both snow cover dynamics and temperature changes. To this end, we computed structural equation models to track the response of shrub radial growth to extending growing season at 1800, 2000 and 2400 m above sea level and for two time periods (i.e. 1959-1988 and 1989-2016). The second period is marked by a significant advance in snow melt-out resulting in a regime shift highlighted at the end of the 1980s by a breakpoint analysis. At the high-elevation site, our results demonstrate a positive effect of increasing growing season length on shrub growth, which is strongly dependent on snowpack depth and snow cover duration. Conversely, at lower elevations, earlier melt-out dates and associated late frost exposure are shown to lead to radial growth reduction. Moreover, the climate signal in ringwidth chronologies of R. ferrugineum portrays a weakening since 1988similar to a phenomenon observed in series from circumpolar and alpine tree-ring sites and referred to as "divergence". By analyzing long-term records of radial growth along an elevation gradient, our work provides novel insights into the complex responses of shrub growth to climate change in alpine environments. This paper demonstrates that R. ferrugineum, as a dominant alpine shrub species, behave as an ecological indicator of the response of alpine ecosystem to global warming.

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Retrogressive thaw slumps in the Alaskan Low Arctic may influence tundra shrub growth more strongly than climate

2022

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Thermokarst disturbance in permafrost landscapes is likely to increase across the tundra biome with climate warming, resulting in changes to topography, vegetation, and biogeochemical cycling. Tundra shrubs grow on permafrost, but shrub–thermokarst relationships are rarely studied in detail. Since the 1980s, Alaska's North Slope has experienced increased thermokarst activity, including retrogressive thaw slumps (RTSs) on hillslopes. Within decades, RTSs near Toolik Lake, Alaska, were colonized by tall (≥0.5 m) deciduous shrubs. We used dendrochronology methods on 66 shrubs (182 stem cross sections) representing dominant deciduous species: willows (Salix pulchra and S. glauca) and dwarf birch (Betula nana) at two RTS chronosequences on Alaska's North Slope comprising seven sites, to quantify thermokarst and climate effects (25 years of temperature and precipitation records) on shrub secondary growth (i.e., annual rings) in RTS‐disturbed and undisturbed moist acidic tussock (MAT) tundra. Across species, average growth ring widths were two times wider for shrubs in RTSs than in MAT, and ring widths decreased with RTS age. A 1°C June temperature increase was associated with 2% wider rings across species and sites, but shrubs showed marginal growth in warmer summers, supporting tundra‐wide shrub climate sensitivity studies. A 4.5% average ring width increase per 1 mm of previous year's September precipitation was seen in shrubs in mid‐successional RTSs, suggesting protective effects of early snowfall in RTSs versus open tundra. Retrogressive thaw slump age category explained 47% and 30% of average ring width variance of willows and dwarf birch, respectively, in linear mixed‐effects models. Climate variables explained 2% average ring width variance across species. Our results suggest that RTS exerts strong successional effects on tundra shrub growth. Climate effects appear to show weaker synoptic patterns across the study area. Retrogressive thaw slumps will likely contribute to tundra greening where RTS activity is increasing.

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Winter precipitation - not summer temperature - is still the main driver for Alpine shrub growth

Cited by 53 publications

References 56 publications

Some (do not) like it hot: shrub growth is hampered by heat and drought at the alpine treeline in recent decades

Some (do not) like it hot: shrub growth is hampered by heat and drought at the alpine treeline in recent decades

Assessing the effects of earlier snow melt-out on alpine shrub growth: The sooner the better?

Retrogressive thaw slumps in the Alaskan Low Arctic may influence tundra shrub growth more strongly than climate

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