Spatial coherence and change of opposite white spruce temperature sensitivities on floodplains in Alaska confirms early-stage boreal biome shift

Juday, Glenn P.; Alix, Claire; Grant, Thomas A.

doi:10.1016/j.foreco.2015.04.016

Cited by 63 publications

(114 citation statements)

References 45 publications

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“…Furthermore, total global precipitation is increasing, with wetter conditions observed and projected for many regions (IPCC 2013), which could ameliorate future tree mortality in those locations. Tree growth and accumulating forest carbon storage across diverse regions have been robust or accelerating as determined by plots (Phillips et al 2008, Lewis et al 2009, McMahon et al 2010, Fang et al 2014, Báez et al 2015, treering studies (Martínez-Vilalta et al 2008, Salzer et al 2009, Bü ntgen et al 2013, Juday et al 2015, biogeochemistry flux tower sites (Zaehle et al 2014), and remote-sensing (Fensholt et al 2012, Jong et al 2012, Liu et al 2015a, Xia et al 2015. Indeed, global terrestrial biomass has increased recently, driven by additional woody biomass in shrublands, savannas, and some forests (Barger et al 2011, Pan et al 2013, Liu et al 2015a.…”

Section: Observationsmentioning

confidence: 99%

On underestimation of global vulnerability to tree mortality and forest die‐off from hotter drought in the Anthropocene

2015

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Abstract. Patterns, mechanisms, projections, and consequences of tree mortality and associated broadscale forest die-off due to drought accompanied by warmer temperatures-''hotter drought'', an emerging characteristic of the Anthropocene-are the focus of rapidly expanding literature. Despite recent observational, experimental, and modeling studies suggesting increased vulnerability of trees to hotter drought and associated pests and pathogens, substantial debate remains among research, management and policy-making communities regarding future tree mortality risks. We summarize key mortalityrelevant findings, differentiating between those implying lesser versus greater levels of vulnerability. Evidence suggesting lesser vulnerability includes forest benefits of elevated [CO 2 ] and increased water-use efficiency; observed and modeled increases in forest growth and canopy greening; widespread increases in woody-plant biomass, density, and extent; compensatory physiological, morphological, and genetic mechanisms; dampening ecological feedbacks; and potential mitigation by forest management. In contrast, recent studies document more rapid mortality under hotter drought due to negative tree physiological responses and accelerated biotic attacks. Additional evidence suggesting greater vulnerability includes rising background mortality rates; projected increases in drought frequency, intensity, and duration; limitations of vegetation models such as inadequately represented mortality processes; warming feedbacks from die-off; and wildfire synergies. Grouping these findings we identify ten contrasting perspectives that shape the vulnerability debate but have not been discussed collectively. We also present a set of global vulnerability drivers that are known with high confidence: (1) droughts eventually occur everywhere; (2) warming produces hotter droughts; (3) atmospheric moisture demand increases nonlinearly with temperature during drought; (4) mortality can occur faster in hotter drought, consistent with fundamental physiology; (5) shorter droughts occur more frequently than longer droughts and can become lethal under warming, increasing the frequency of lethal drought nonlinearly; and (6) mortality happens rapidly relative to growth intervals needed for forest recovery. These high-confidence drivers, in concert with research supporting greater vulnerability perspectives, support an overall viewpoint of greater forest vulnerability globally. We surmise that mortality vulnerability is being discounted in part due to difficulties in predicting threshold responses to extreme climate events. Given the profound ecological and societal implications of underestimating global vulnerability to hotter drought, we highlight urgent challenges for research, management, and policy-making communities.

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Section: Observationsmentioning

confidence: 99%

On underestimation of global vulnerability to tree mortality and forest die‐off from hotter drought in the Anthropocene

2015

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“…We correlated site-level chronologies with climate records from the Fairbanks Station, a first-order weather station located at the Fairbanks International Airport. The same climate data has been used previously in dendrochronological reconstructions in interior Alaska, and it is highly correlated with growth patterns in upland white spruce (Barber et al, 2000;Juday and Alix, 2012;Juday et al, 2015). Since our black spruce chronologies have limited temporal depths in the early part of the series, we limited the climate-growth analysis to the period A.D. 1949-2010.…”

Section: Analysis Of Climate-growth Relationshipsmentioning

confidence: 99%

Climate-Growth Relationships Along a Black Spruce Toposequence in Interior Alaska

Wolken

Mann

Grant

et al. 2016

Arctic, Antarctic, and Alpine Research

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“…Recent forest cover data collected across both tropical and alpine indicator species highlighted population shifts in response to environmental variability (Rannow 2013, Juday et al 2015. Aided by analyses of temperature and precipitation gradients, tropical plant researchers in Hawai'i have also noted subtle shifts in the range of native Hawaiian plant species in response to climate change (Krushelnycky et al 2013) but this work did not extend to forest tree species.…”

Section: Introductionmentioning

confidence: 95%

“…These data highlight the importance of maintaining population sizes and decreased habitat fragmentation on future reproductive success. Nearly a decade ago, Aitken et al (2008) proposed that tree species capable of a greater degree of adaptation, were most likely to survive future climatic change trees may experience range expansion or contraction depending on inherent plasticity and availability of suitable soils and site conditions in novel locations, versus less plastic species that will exhibit decreased population representation across locations (Ozolincius et al 2014, Juday et al 2015.…”

Section: Introductionmentioning

confidence: 99%

Stable isotope ratios and reforestation potential in Acacia koa populations on Hawai’i

Lawson

Pike

2017

Ann. For. Res.

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Lawson S. S., Pike C. C. 2017. Stable isotope ratios and reforestation potential in Acacia koa populations on Hawai'i. Ann. For. Res. 60(2): 279-295.Abstract. Stable carbon and nitrogen isotopes can be influenced by a multitude of factors including elevation, precipitation rate, season, and temperature. This work examined variability in foliar stable carbon (δ13C) and nitrogen (δ15N) isotope ratios of koa (Acacia koa) across 17 sites on Hawai'i Island, delineated by elevation and precipitation gradients. Sites were identified and grouped with respect to mean annual precipitation (MAP), mean annual temperature (MAT) and position along three elevation transects. Analysis of resultant δ13C and δ15N isotope ratios from multiple individuals across ecoregions indicated certain regions exhibited a correlation between carbon and/or nitrogen content, isotope ratios, precipitation, and elevation however, many comparisons showed no correlation. We used publicly available temperature and moisture data to help eliminate confounding effects by climatic drivers and capture possible points of contention. At sites where the temperature, precipitation, and elevation data were not significantly different, we compared stable isotope information to determine if additional variables might have contributed to a lack of definitive data. Our results identified several areas within the Waiakea Forest Reserve and Volcanoes National Park where, based on isotope analyses, reforestation efforts could be most successfully initiated.

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Spatial coherence and change of opposite white spruce temperature sensitivities on floodplains in Alaska confirms early-stage boreal biome shift

Cited by 63 publications

References 45 publications

On underestimation of global vulnerability to tree mortality and forest die‐off from hotter drought in the Anthropocene

On underestimation of global vulnerability to tree mortality and forest die‐off from hotter drought in the Anthropocene

Climate-Growth Relationships Along a Black Spruce Toposequence in Interior Alaska

Stable isotope ratios and reforestation potential in Acacia koa populations on Hawai’i

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