Long‐term experimental warming and nutrient additions increase productivity in tall deciduous shrub tundra

DeMarco, Jennie; Mack, Michelle C.; Bret‐Harte, M. Syndonia; Burton, Mark; Shaver, Gaius R.

doi:10.1890/es13-00281.1

Cited by 75 publications

(67 citation statements)

References 57 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Nitrogen addition had a positive effect on B. glandulosa radial growth. This result corroborates other studies that have shown that tundra shrubs can benefit from higher nutrient availability to increase their overall biomass (DeMarco, Mack, Bret‐Harte, et al., ; Parsons et al., ; Shaver & Chapin, ), cover or height (Press, Potter, Burke, Callaghan, & Lee, ). However, nitrogen addition‐induced increase in radial growth only occurred 3 years out of 5, indicating that nitrogen addition alone is not sufficient to insure radial growth increase.…”

Section: Discussionsupporting

confidence: 90%

“…1.5°C (Marion et al., ). This being said, the positive effect of nitrogen addition corroborates the results of many experimental fertilisation studies on deciduous shrubs in high‐latitude ecosystems (Chapin et al., ; DeMarco, Mack, Bret‐Harte, et al., ; Gough et al., ; Zamin, Bret‐Harte, & Grogan, ). The positive response of B. glandulosa to enhance soil nitrogen availability shows that its growth is at least partially limited by nitrogen.…”

Section: Discussionsupporting

confidence: 82%

“…Simulation experiments using open‐top chambers have demonstrated that an increase of 1–3°C in summer temperatures (Marion et al., ) can increase shrub cover, height and biomass (Arft et al., ; Wahren, Walker, & Bret‐Harte, ). There is also experimental evidence that nutrient availability might be more limiting than temperature for shrub growth (Chapin, Shaver, Giblin, Nadelhoffer, & Laundre, ; DeMarco, Mack, & Bret‐Harte, ), as shrub biomass shows a stronger increase to nutrient addition treatments than to experimental warming (DeMarco, Mack, Bret‐Harte, Burton, & Shaver, ; Gough, Moore, Shaver, Simpson, & Johnson, ; Shaver et al., ).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Simulated caribou browsing limits the effect of nutrient addition on the growth of Betula glandulosa, an expanding shrub species in Eastern Canada

et al. 2017

View full text Add to dashboard Cite

Warmer summer temperatures and enhanced soil fertility increase shrub growth in tundra ecosystems, and these factors have likely contributed to shrub expansion at the circumpolar scale over the last decades. Conversely, large herbivores have the potential to counteract the positive impacts of climate change on shrub growth. Indeed, by stripping the leaves, herbivores have the potential to control the growth of shrub species and, consequently, limit their expansion. To disentangle the impacts of climate change and herbivory on Betula glandulosa Michx., we conducted a 5‐year factorial experiment near Deception Bay, Nunavik, Canada, in which we simulated warmer temperatures, increased nitrogen availability and three caribou browsing intensities during the growing season. At the end of the experiment, we harvested the above‐ground biomass of B. glandulosa and conducted dendrochronological analyses on stems. Fertilised plots under ambient temperature had 34% greater shrub biomass than plots assigned to the combined treatment of nitrogen addition and warmer temperatures. Browsing intensity had no effect on final biomass. Nitrogen addition increased radial growth (18%–33%; 3 years out of 5). Overall, browsing had a cumulative negative impact on B. glandulosa radial growth during the 5‐year experiment. While browsing had no effect in the first year of the experiment, moderate browsing (leaves stripped on 25% of available shoots) decreased radial growth by 27% at year 2, 32% at year 4 and 27% at year 5. Heavy browsing (leaves stripped on 75% of available shoots annually) decreased radial growth by c. 27% at year 2, 37% at year 3, 50% at year 4 and 48% at year 5. We did not observe significant interactions between browsing, temperature and nitrogen availability. Synthesis. Our results clearly showed that caribou browsing may limit the growth of B. glandulosa, and thus can potentially limit its expansion. Herbivory should thus be considered when predicting tundra vegetation changes in the Arctic, at least in areas with high herbivore densities.

show abstract

Section: Discussionsupporting

confidence: 90%

Section: Discussionsupporting

confidence: 82%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Simulated caribou browsing limits the effect of nutrient addition on the growth of Betula glandulosa, an expanding shrub species in Eastern Canada

et al. 2017

View full text Add to dashboard Cite

show abstract

“…The increased abundance of shrubs in high-latitude regions has been studied extensively (e.g., Sturm et al, 2001b;Myers-Smith et al, 2011;DeMarco et al, 2014a), and numerous studies have identified links with factors such as snow cover (Sturm et al, 2001a;Pomeroy et al, 2006), radiation regime (Bewley et al, 2007), and nutrient cycling (Myers-Smith and Hik, 2013;DeMarco et al, 2014b). Regarding soil temperatures, the isolated assessment of shrub expansion indicates that the capture of drifting snow by shrubs increases snow depth and soil temperatures in winter, while shading decreases temperatures in summer (e.g., Sturm et al, 2001a).…”

Section: Implications For Feedback Processes With Climate Change 42mentioning

confidence: 99%

Shifted energy fluxes, increased Bowen ratios, and reduced thaw depths linked with drainage-induced changes in permafrost ecosystem structure

et al. 2017

View full text Add to dashboard Cite

Abstract. Hydrologic conditions are a key factor in Arctic ecosystems, with strong influences on ecosystem structure and related effects on biogeophysical and biogeochemical processes. With systematic changes in water availability expected for large parts of the northern high-latitude region in the coming centuries, knowledge on shifts in ecosystem functionality triggered by altered water levels is crucial for reducing uncertainties in climate change predictions. Here, we present findings from paired ecosystem observations in northeast Siberia comprising a drained and a control site. At the drainage site, the water table has been artificially lowered by up to 30 cm in summer for more than a decade. This sustained primary disturbance in hydrologic conditions has triggered a suite of secondary shifts in ecosystem properties, including vegetation community structure, snow cover dynamics, and radiation budget, all of which influence the net effects of drainage. Reduced thermal conductivity in dry organic soils was identified as the dominating drainage effect on energy budget and soil thermal regime. Through this effect, reduced heat transfer into deeper soil layers leads to shallower thaw depths, initially leading to a stabilization of organic permafrost soils, while the long-term effects on permafrost temperature trends still need to be assessed. At the same time, more energy is transferred back into the atmosphere as sensible heat in the drained area, which may trigger a warming of the lower atmospheric surface layer.

show abstract

“…; DeMarco et al . ). This should result in larger differences in seedling performance between bryophyte species.…”

Section: Introductionmentioning

confidence: 97%

Bryophyte traits explain climate‐warming effects on tree seedling establishment

et al. 2016

View full text Add to dashboard Cite

Summary Above the alpine tree line, bryophytes cover much of the tundra soil surface in dense, often monospecific carpets. Therefore, when climate warming enables tree seedling establishment above the tree line, interaction with the bryophyte layer is inevitable. Bryophytes are known to modify their environment in various ways. However, little is known about to which extent and by which mechanisms bryophytes affect the response of tree seedlings to climate warming. We aimed to assess and understand the importance of bryophyte species identity and traits for tree seedling performance at tree line temperatures and their response to warmer conditions. Seedlings of two common, tree line‐forming tree species (Betula pubescens and Pinus sylvestris) were planted into intact cushions of eight common tundra bryophyte species and bryophyte‐free soil and grown for 18 weeks at current (7·0 °C) and near‐future (30–50 years; 9·2 °C) tree line average growing‐season temperatures. Seedling performance (biomass increase and N‐uptake) was measured and related to bryophyte species identity and traits indicative of their impact on the environment. Tree seedlings performed equally well or better in the presence of bryophytes than in bryophyte‐free soil, which contrasts to their usually negative effects in milder climates. In addition, seedling performance and their response to higher temperatures depended on bryophyte species and seedlings of both species grew largest in the pan‐boreal and subarctic bryophyte Hylocomium splendens. However, B. pubescens seedlings showed much stronger responses to higher temperatures when grown in bryophytes than in bryophyte‐free soil, while the opposite was true for P. sylvestris seedlings. For B. pubescens, but not for P. sylvestris, available organic nitrogen of the bryophyte species was the trait that best predicted seedling responses to higher temperatures, likely because these seedlings had increased N‐demands. Synthesis. Climatically driven changes in bryophyte species distribution may not only have knock‐on effects on vascular plant establishment, but temperature effects on seedling performance are themselves moderated by bryophytes in a species‐specific way. Bryophyte traits can serve as a useful tool for understanding and predicting these complex interactions.

show abstract

Long‐term experimental warming and nutrient additions increase productivity in tall deciduous shrub tundra

Cited by 75 publications

References 57 publications

Simulated caribou browsing limits the effect of nutrient addition on the growth of Betula glandulosa, an expanding shrub species in Eastern Canada

Simulated caribou browsing limits the effect of nutrient addition on the growth of Betula glandulosa, an expanding shrub species in Eastern Canada

Shifted energy fluxes, increased Bowen ratios, and reduced thaw depths linked with drainage-induced changes in permafrost ecosystem structure

Bryophyte traits explain climate‐warming effects on tree seedling establishment

Contact Info

Product

Resources

About