Satellite observations document trends consistent with a boreal forest biome shift

Global Change Biology, Journal Year: 2022, Volume and Issue: 28(10), P. 3275 - 3292

Published: Feb. 24, 2022

The boreal forest biome is a major component of Earth's biosphere and climate system that projected to shift northward due continued change over the coming century. Indicators will likely first be evident along climatic margins include changes in vegetation productivity, mortality, recruitment, as well overall greenness. However, extent which already underway remains unclear because local nature most field studies, sparsity systematic ground-based ecological monitoring, reliance on coarse resolution satellite observations. Here, we evaluated early indicators using four decades moderate (30 m) observations biogeoclimatic spatial datasets. Specifically, quantified interannual trends annual maximum greenness an ensemble indices derived from Landsat at 100,000 sample sites areas without signs recent disturbance. We found increased (greened) 38 [29, 42] % 22 [15, 26] 1985 2019 2000 2019, whereas decreased (browned) 13 [9, 15] 15 [13, 19] during these respective periods [95% Monte Carlo confidence intervals]. Greening was thus 3.0 [2.6, 3.5] 1.5 [0.8, 2.0] times more common than browning primarily occurred cold sparsely treed with high soil nitrogen summer warming. Conversely, climatically warmest both types (e.g., evergreen conifer forests), especially densely where summers became warmer drier. These macroecological reflect underlying shifts recruitment are consistent stages shift.

Language: Английский

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Sufficient conditions for rapid range expansion of a boreal conifer

Nature, Journal Year: 2022, Volume and Issue: 608(7923), P. 546 - 551

Published: Aug. 10, 2022

Unprecedented modern rates of warming are expected to advance boreal forest into Arctic tundra1, thereby reducing albedo2-4, altering carbon cycling4 and further changing climate1-4, yet the patterns processes this biome shift remain unclear5. Climate warming, required for previous advances6-17, is not sufficient by itself range expansion conifers forming forest-tundra ecotones5,12-15,17-20. No high-latitude population conifers, dominant North American treeline taxon, has previously been documented5 advancing at following last glacial maximum (LGM)6-8. Here we describe a white spruce (Picea glauca) post-LGM rates7 across an basin distant from established treelines provide evidence mechanisms sustaining advance. The doubles each decade, with exponential radial growth in main stems individual trees correlating positively July air temperature. Lateral branches adults terminal leaders large juveniles grow almost twice as fast those treelines. We conclude that surpassing temperature thresholds1,6-17, together winter winds facilitating long-distance dispersal, deeper snowpack increased soil nutrient availability promoting recruitment growth, provides conditions These observations enable forecast modelling important insights environmental converting tundra forest.

Language: Английский

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Mechanisms and Impacts of Earth System Tipping Elements

Reviews of Geophysics, Journal Year: 2023, Volume and Issue: 61(1)

Published: Feb. 16, 2023

Abstract Tipping elements are components of the Earth system which may respond nonlinearly to anthropogenic climate change by transitioning toward substantially different long‐term states upon passing key thresholds or “tipping points.” In some cases, such changes could produce additional greenhouse gas emissions radiative forcing that compound global warming. Improved understanding tipping is important for predicting future risks and their impacts. Here we review mechanisms, predictions, impacts, knowledge gaps associated with 10 notable proposed be elements. We evaluate approaching critical whether shifts manifest rapidly over longer timescales. Some have a higher risk crossing points under middle‐of‐the‐road pathways will possibly affect major ecosystems, patterns, and/or carbon cycling within 21st century. However, literature assessing scenarios indicates strong potential reduce impacts many through mitigation. The studies synthesized in our suggest most do not possess abrupt years, exhibit behavior, rather responding more predictably directly magnitude forcing. Nevertheless, uncertainties remain elements, highlighting an acute need further research modeling better constrain risks.

Language: Английский

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Towards an increasingly biased view on Arctic change

Nature Climate Change, Journal Year: 2024, Volume and Issue: 14(2), P. 152 - 155

Published: Jan. 22, 2024

Abstract The Russian invasion of Ukraine hampers the ability to adequately describe conditions across Arctic, thus biasing view on Arctic change. Here we benchmark pan-Arctic representativeness largest high-latitude research station network, INTERACT, with or without stations. Excluding stations lowers markedly, some biases being same magnitude as expected shifts caused by climate change end century.

Language: Английский

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Browning events in Arctic ecosystems: Diverse causes with common consequences

PLOS Climate, Journal Year: 2025, Volume and Issue: 4(1), P. e0000570 - e0000570

Published: Jan. 27, 2025

Arctic ecosystems are experiencing extreme climatic, biotic and physical disturbance events that can cause substantial loss of plant biomass productivity, sometimes at scales >1000 km 2 . Collectively known as browning events, these key contributors to the spatial temporal complexity greening vegetation dynamics. If we properly understand future terrestrial ecosystems, their feedbacks climate, understanding is essential. Here bring together in compare impacts rates recovery, likely changes frequency distribution. We also seek commonalities across contrasting event types. find while high levels damage (up 100% mortality), have capacity for with largely re-established within five years many events. despite leaf area dominant species, compensatory mechanisms such increased productivity undamaged subordinate species lessen on carbon sequestration. These hold true most climatic but less so fire abrupt permafrost thaw, due greater removal vegetation. Counterintuitively, some provide conditions (greening) longer-term, particularly where exposes ground colonisation. Finally, projected causes currently suggest types will become more frequent, tundra thaw expected be greatest severe occurrence regions. Overall, increasingly important consequences ecosystem structure function, feedback climate.

Language: Английский

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Mountain treelines climb slowly despite rapid climate warming

Global Ecology and Biogeography, Journal Year: 2020, Volume and Issue: 30(1), P. 305 - 315

Published: Nov. 13, 2020

Abstract Aim To better understand how climate change drives altitudinal treeline dynamics at large spatial scales. Location Northern Hemisphere. Time period 1901–2018. Major taxa studied Tree species that constitute alpine treelines. Methods We conducted a meta‐analysis of annual shift rates 143 sites from 38 published studies. For each site, we calculated current in or seasonal temperatures, precipitation and drought (standardized evapotranspiration index). then evaluated relationships between rates, site characteristics using standard partial correlation analyses, as well generalized linear models. These analyses were the hemispheric scale for two geographic subsets subarctic (north 60° N) temperate regions (south N). Results Treelines ascended 88.8%, remained stable 10.5% descended 0.7% sites. The mean rate (0.354 m/year) was half what would be expected warming alone. Treeline shifts significantly faster than regions. effect more important temperature predicting rate. In regions, autumn mostly determined rates. region, warmer temperatures higher accelerated whereas wetter springs reduced them. Autumn winter minimum best explained across Main conclusions A combination thermal hydrological factors Hemisphere, with assuming an modifying role general temperature‐driven ascent. Regional therefore, co‐depend on drying wetting trends, which should considered future estimates global impacts ecosystems.

Language: Английский

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Global fading of the temperature–growth coupling at alpine and polar treelines

Global Change Biology, Journal Year: 2021, Volume and Issue: 27(9), P. 1879 - 1889

Published: Jan. 29, 2021

Abstract Climate warming is expected to positively alter upward and poleward treelines which are controlled by low temperature a short growing season. Despite the importance of as bioassay climate change, global field assessment posterior forecasting tree growth at annual scales lacking. Using annually resolved tree‐ring data located across Eurasia Americas, we quantified modeled relationship between radial treeline during 20th century. We then tested whether this temperature–growth association will remain stable 21st century using forward model under two scenarios (RCP 4.5 8.5). During century, enhancements were common in most sites, showed positive trends. Interestingly, trends was contingent on age suggesting biogeographic patterns local factors besides warming. Simulations forecast decoupling The season projected lengthen rates would increase become less dependent rise. These forecasts illustrate how may decouple from cold regions near margins existence. Such could impact ecosystem processes mountain polar biomes, with feedbacks

Language: Английский

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Arctic shrub expansion revealed by Landsat-derived multitemporal vegetation cover fractions in the Western Canadian Arctic

Remote Sensing of Environment, Journal Year: 2022, Volume and Issue: 281, P. 113228 - 113228

Published: Sept. 9, 2022

Warming induced shifts in tundra vegetation composition and structure, including circumpolar expansion of shrubs, modifies ecosystem structure functioning with potentially global consequences due to feedback mechanisms between climate. Satellite-derived indices indicate widespread greening the surface, often associated regional evidence shrub obtained from long-term ecological monitoring repeated orthophotos. However, explicitly quantifying across large scales using satellite observations requires characterising fine-scale mosaic Arctic types beyond index-based approaches. Although previous studies have illustrated potential estimating fractional cover various Plant Functional Types (PFTs) imagery, limited availability reference data space time has constrained deriving fraction series capable detecting expansion. We applied regression-based unmixing synthetic training build multitemporal machine learning models order estimate shrubs other surface components Mackenzie Delta Region for six intervals 1984 2020. trained Kernel Ridge Regression (KRR) Random Forest (RFR) Landsat-derived spectral-temporal-metrics generated pure class spectra directly imagery. Independent validation very-high-resolution imagery suggested that KRR outperforms RFR, a MAE 10.6% remaining MAEs 3.0 11.2%. Canopy-forming were well modelled all densities, coniferous tree tended be overestimated differentiating herbaceous lichen was challenging. Shrub expanded by on average + 2.2% per decade entire study area 4.2% within low tundra, while relative changes strongest northernmost regions. In conjunction expansion, we observed plant decline. Our results corroborate perception replacement homogenisation communities facilitated competitive advantage species under warming The proposed method allows multidecadal quantitative estimates at 30 m resolution, initiating new opportunities mapping past present PFTs can help advance our understanding vast heterogeneous biome.

Language: Английский

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Not every high‐latitude or high‐elevation forest edge is a treeline

Journal of Biogeography, Journal Year: 2023, Volume and Issue: 50(5), P. 838 - 845

Published: March 14, 2023

Abstract Attempts at identifying climate warming effects on mountain and arctic vegetation caused a recent hype in treeline studies. In this perspectives article, we recall the need of clear‐cut definitions, consistent terminology theoretical framework that permits hypothesis testing. Founded ecological niche concept, application fundamental edge to defining potential climatic limit tree growth, while realized captures all deviations for reasons related other, more local, abiotic factors, biotic interactions, disturbances human interventions. An important point is globally common phenomenon calls driver which temperature low life form tree. We explain why other factors may affect local range limits, such as microclimate, moisture wind do not devaluate classical isotherm concept. Our key message applying clearly defined concept treeline, also allows from it explaining within reproducible framework.

Language: Английский

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Northern expansion is not compensating for southern declines in North American boreal forests

Nature Communications, Journal Year: 2023, Volume and Issue: 14(1)

Published: June 8, 2023

Climate change is expected to shift the boreal biome northward through expansion at northern and contraction southern boundary respectively. However, biome-scale evidence of such a rare. Here, we used remotely-sensed tree cover data quantify temporal changes across North American from 2000 2019. We reveal strong north-south asymmetry in change, coupled with range shrinkage distributions. found no for biome, while increased markedly core range. By contrast, declined along boundary, where losses were related largely wildfires timber logging. show that these contrasting trends are structural indicators possible onset which may lead long-term carbon declines.

Language: Английский

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