Soil Nitrogen Five Years after Bark Beetle Infestation in Lodgepole Pine Forests

Norton, Urszula; Ewers, B. E.; Borkhuu, B.; Brown, Nicholas R.; Pendall, Elise

doi:10.2136/sssaj2014.05.0223

Cited by 28 publications

(25 citation statements)

References 55 publications

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“…Taken together, it is reasonable to expect that more water was available in this ecosystem in the years following the peak mortality, which is consistent with the observed increase in soil moisture (Frank et al, ). It is uncertain how long the reductions in growing season evapotranspiration will continue as the understory plants respond (Boucher & Mead, ; Millar et al, ), postbeetle increases in soil moisture lessen (Norton et al, ), and the surviving trees have a growth release (Veblen et al, ). Since the sublimation process is intimately tied to the canopy, at least the winter change in ecosystem water balance should persist for decades while forest succession begins in the understory (Aplet et al, ).…”

Section: Discussionmentioning

confidence: 99%

Bayesian Analyses of 17 Winters of Water Vapor Fluxes Show Bark Beetles Reduce Sublimation

Frank

Massman

Ewers

et al. 2019

Water Resources Research

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Sublimation is an important hydrological flux in cold, snow-dominated ecosystems. In high-elevation spruce-fir forests of western North America, spruce beetle outbreaks have killed trees, reduced the canopy, and altered processes that control sublimation. We evaluated two hypotheses related to effects of disturbance on sublimation in this ecosystem: (1) the dominant source for sublimation is canopy intercepted snow and (2) the loss of canopy following a beetle disturbance leads to less total sublimation. To incorporate uncertainty hierarchically across multiple data sources and address phenomenological parsimony, Bayesian statistics were used to analyze 17 years (2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016) of winter eddy covariance flux data at the Glacier Lakes Ecosystem Experiments Sites AmeriFlux sites where a spruce beetle outbreak caused 75-85% basal area mortality. Our analysis revealed that resistances to sublimate snow from the canopy were an order of magnitude less than from the snowpack, and the maximum snow loading capacity in disturbed canopies was reduced to 34% of its pre-outbreak value. Total sublimation has decreased since 2010, 2 years after the main outbreak, declining 24% (with a 95% credible interval, C.I., between 18% and 38%) during 2014-2016 due to a 32% decrease in canopy sublimation. Snowpack sublimation only increased 3% over this period. With less total sublimation, the forest retained 6.1% (4.5-12.3% C.I.) more snowpack mass or equivalently 4.4% (3.2-8.8 C.I.) of the annual precipitation. Considering tree growth and ecological succession are slow in spruce-fir forests, this decrease in sublimation should persist as an increased snowpack for decades, with substantial impacts on catchment hydrologic processes and potentially streamflow.

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Section: Discussionmentioning

confidence: 99%

Bayesian Analyses of 17 Winters of Water Vapor Fluxes Show Bark Beetles Reduce Sublimation

Frank

Massman

Ewers

et al. 2019

Water Resources Research

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“…Results of larger‐scale field‐based studies, [e.g., Stednick , ; Biederman et al ., , ] indicate that MPB effects may not surpass the changes in forest structure needed to produce significant changes in annual water yield. Recent watershed‐scale modeling [ Livneh et al ., ] identified increases in annual water yield that were buffered by regeneration of understory vegetation, consistent with empirical evidence of soil moisture recovery with understory regrowth [ Norton et al ., ]. Increases in observed streamflow from combined forest disturbance (including wildfire, logging, and MPB infestation) has been found to oppose the change from inter‐annual climate trends [ Zhang and Wei , ].…”

Section: Introductionmentioning

confidence: 99%

“…While some studies report decreases in modeled [Mikkelson et al, 2013b] or observed [Frank et al, 2014;Bernsteinov a et al, 2015] total ET, leading to increased water yield at the hillslope or flux tower scale, others show mitigating changes that minimize the net effect [Biederman et al, 2014a;Brown et al, 2014]. The loss of transpiration often leads to a temporary increase in soil moisture under affected trees [Clow et al, 2011;Bearup et al, 2014b;Norton et al, 2015] that may feedback to increased ground evaporation, which is also enhanced through increased exposure with canopy loss. Similar to the inconsistent response in ET, peak snow water equivalent (SWE) has been observed to either increase [Boon, 2012;Pugh and Small, 2012;Perrot et al, 2014;Winkler et al, 2014;Bernsteinov a et al 2015] or to be unaffected [Biederman et al, 2014b] in MPB-affected forests.…”

Section: Introductionmentioning

confidence: 99%

Numerical experiments to explain multiscale hydrological responses to mountain pine beetle tree mortality in a headwater watershed

Penn

Bearup

Maxwell

et al. 2016

Water Resources Research

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The effects of mountain pine beetle (MPB)‐induced tree mortality on a headwater hydrologic system were investigated using an integrated physical modeling framework with a high‐resolution computational grid. Simulations of MPB‐affected and unaffected conditions, each with identical atmospheric forcing for a normal water year, were compared at multiple scales to evaluate the effects of scale on MPB‐affected hydrologic systems. Individual locations within the larger model were shown to maintain hillslope‐scale processes affecting snowpack dynamics, total evapotranspiration, and soil moisture that are comparable to several field‐based studies and previous modeling work. Hillslope‐scale analyses also highlight the influence of compensating changes in evapotranspiration and snow processes. Reduced transpiration in the Grey Phase of MPB‐induced tree mortality was offset by increased late‐summer evaporation, while overall snowpack dynamics were more dependent on elevation effects than MPB‐induced tree mortality. At the watershed scale, unaffected areas obscured the magnitude of MPB effects. Annual water yield from the watershed increased during Grey Phase simulations by 11 percent; a difference that would be difficult to diagnose with long‐term gage observations that are complicated by inter‐annual climate variability. The effects on hydrology observed and simulated at the hillslope scale can be further damped at the watershed scale, which spans more life zones and a broader range of landscape properties. These scaling effects may change under extreme conditions, e.g., increased total MPB‐affected area or a water year with above average snowpack.

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“…The impacts of canopy uptake and canopy chemistry resulting from changes in vegetation density and composition could be explored in more detail with future work using a 1-D forest canopy-chemistry model (e.g., Wolfe, 2011;Ashworth et al, 2015) for the regions where we project large impacts. We have assumed that the basal emissions from the soil after the disturbance will be the same as those prior to the disturbance, but large-scale tree mortality and forest succession have the potential to alter soil biogeochemistry (Gao et al, 2015;Norton et al, 2015;Trahan et al, 2015).…”

Section: J a Geddes Et Al: Land Cover Change Impacts On Atmospherimentioning

confidence: 99%

Land cover change impacts on atmospheric chemistry: simulating projected large-scale tree mortality in the United States

et al. 2016

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Abstract. Land use and land cover changes impact climate and air quality by altering the exchange of trace gases between the Earth's surface and atmosphere. Large-scale tree mortality that is projected to occur across the United States as a result of insect and disease may therefore have unexplored consequences for tropospheric chemistry. We develop a land use module for the GEOS-Chem global chemical transport model to facilitate simulations involving changes to the land surface, and to improve consistency across land-atmosphere exchange processes. The model is used to test the impact of projected national-scale tree mortality risk through 2027 estimated by the 2012 USDA Forest Service National Insect and Disease Risk Assessment. Changes in biogenic emissions alone decrease monthly mean O 3 by up to 0.4 ppb, but reductions in deposition velocity compensate or exceed the effects of emissions yielding a net increase in O 3 of more than 1 ppb in some areas. The O 3 response to the projected change in emissions is affected by the ratio of baseline NO x : VOC concentrations, suggesting that in addition to the degree of land cover change, tree mortality impacts depend on whether a region is NO x -limited or NO x -saturated. Consequently, air quality (as diagnosed by the number of days that 8 h average O 3 exceeds 70 ppb) improves in polluted environments where changes in emissions are more important than changes to dry deposition, but worsens in clean environments where changes to dry deposition are the more important term. The influence of changes in dry deposition demonstrated here underscores the need to evaluate treatments of this physical process in models. Biogenic secondary organic aerosol loadings are significantly affected across the US, decreasing by 5-10 % across many regions, and by more than 25 % locally. Tree mortality could therefore impact background aerosol loadings by between 0.5 and 2 µg m −3 . Changes to reactive nitrogen oxide abundance and partitioning are also locally important. The regional effects simulated here are similar in magnitude to other scenarios that consider future biofuel cropping or natural succession, further demonstrating that biosphere-atmosphere exchange should be considered when predicting future air quality and climate. We point to important uncertainties and further development that should be addressed for a more robust understanding of land cover change feedbacks.

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Soil Nitrogen Five Years after Bark Beetle Infestation in Lodgepole Pine Forests

Cited by 28 publications

References 55 publications

Bayesian Analyses of 17 Winters of Water Vapor Fluxes Show Bark Beetles Reduce Sublimation

Bayesian Analyses of 17 Winters of Water Vapor Fluxes Show Bark Beetles Reduce Sublimation

Numerical experiments to explain multiscale hydrological responses to mountain pine beetle tree mortality in a headwater watershed

Land cover change impacts on atmospheric chemistry: simulating projected large-scale tree mortality in the United States

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