Elsevier

Forest Ecology and Management

Volume 409, 1 February 2018, Pages 317-332
Forest Ecology and Management

Interactions of predominant insects and diseases with climate change in Douglas-fir forests of western Oregon and Washington, U.S.A.

https://doi.org/10.1016/j.foreco.2017.11.004Get rights and content

Highlights

  • Forest disturbances are beginning to show evidence of climate-mediated changes.

  • Biotic disturbances must be understood to predict responses of future forests.

  • We reviewed major biotic agents in the Douglas-fir region’s disturbance regime.

  • Interactions with climate change will likely vary among biotic disturbance agents.

  • These factors must be characterized by forest type to aid in adaptive management.

Abstract

Forest disturbance regimes are beginning to show evidence of climate-mediated changes, such as increasing severity of droughts and insect outbreaks. We review the major insects and pathogens affecting the disturbance regime for coastal Douglas-fir forests in western Oregon and Washington State, USA, and ask how future climate changes may influence their role in disturbance ecology. Although the physiological constraints of light, temperature, and moisture largely control tree growth, episodic and chronic disturbances interacting with biological factors have substantial impacts on the structure and functioning of forest ecosystems in this region. Understanding insect and disease interactions is critical to predicting forest response to climate change and the consequences for ecosystem services, such as timber, clean water, fish and wildlife. We focused on future predictions for warmer wetter winters, hotter drier summers, and elevated atmospheric CO2 to hypothesize the response of Douglas-fir forests to the major insects and diseases influencing this forest type: Douglas-fir beetle, Swiss needle cast, black stain root disease, and laminated root rot. We hypothesize that (1) Douglas-fir beetle and black stain root disease could become more prevalent with increasing, fire, temperature stress, and moisture stress, (2) future impacts of Swiss needle cast are difficult to predict due to uncertainties in May-July leaf wetness, but warmer winters could contribute to intensification at higher elevations, and (3) laminated root rot will be influenced primarily by forest management, rather than climatic change. Furthermore, these biotic disturbance agents interact in complex ways that are poorly understood. Consequently, to inform management decisions, insect and disease influences on disturbance regimes must be characterized specifically by forest type and region in order to accurately capture these interactions in light of future climate-mediated changes.

Introduction

Disturbance regimes in forests of western North America are showing evidence of climate-mediated shifts associated with global climate change in the form of historically unprecedented tree mortality (Anderegg et al., 2012, van Mantgem et al., 2009). Instigating factors for these mortality events include extreme drought (Allen et al., 2015, Asner et al., 2015), increased fire severity and extent (Abatzoglou and Williams, 2016), and expansion of bark beetles into previously climatically unsuitable habitat (Bentz et al., 2010, Björkman and Niemelä, 2015). The frequency and severity of forest disturbances will likely continue to increase given predicted climate-related changes in environmental conditions over the 21 st century (Allen et al., 2015), which will influence a range of characteristics of these forests including the ecosystem services that they provide (Johnstone et al., 2016, Seidl et al., 2016).

Projected changes in climate will make forests more vulnerable to tree mortality resulting from physiological stress interacting with other climate-influenced events, such as insect and disease outbreaks, droughts and fires (Beedlow et al., 2013, Kolb et al., 2016, Weed et al., 2013). Current predictions for major climate-related trends affecting forests in western North America include increased fire season length and burned area (Abatzoglou and Williams, 2016, Flannigan et al., 2013), increased occurrence of severe drought (Allen et al., 2015), reduced mountain snowpack (Kapnick and Hall, 2012), and generally increasing temperature, with seasonal trends including warmer wetter winters, and hotter drier growing seasons (Rupp et al., 2016).

There is a growing interest in understanding the interactions of multiple disturbance factors (Anderegg et al., 2015, Johnstone et al., 2016, Law and Waring, 2015) in forest ecosystems because their combined effects can differ from that of any single agent acting alone (Seidl et al., 2016). However, interactions for any given forest type vary by landscape character, forest structure, specific insect herbivores and forest pathogens, as well as seasonal climatic factors, storms, and fire patterns. Consequently, to inform management decisions, disturbance regimes must be characterized specifically by forest type and region in order to accurately capture these interactions and allow for prediction of future climate-mediated changes. If conducted at a scale at which management actions are implemented, such as forests with the same dominant tree species and climatic conditions, assessments of potential climate-related changes to disturbance regimes can greatly improve our ability to adaptively manage our forests and the ecosystem services they provide.

Here, we examine the primary insects and diseases (referred to throughout as biotic disturbance agents) of Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco). Although western hemlock is commonly found as a co-dominant in Douglas-fir forests, especially in old growth forests, Douglas-fir is the dominant species on most of the forested land from near sea-level to roughly 1200 m elevation in western Oregon and Washington, U.S.A. Further, Douglas-fir is the principle timber species, and it is ecologically important for carbon sequestration, and wildlife habitat, as well as being vital for the production of hydropower, irrigation, and drinking water (Curtis and Carey, 1996, Harmon et al., 2004, Kline et al., 2016, Ruggiero et al., 1991). Ecological effects of the major disturbance regimes, especially fire and logging, have been studied extensively in this forest type (Cohen et al., 2002, Creutzburg et al., 2016, Healey et al., 2008, Tepley et al., 2013, Wimberly and Spies, 2001). However, the role of insects and diseases within the disturbance regime has not been adequately addressed, even though there is currently a major foliage disease (Swiss needle cast) epidemic occurring in the region (Ritóková et al., 2016).

Here, we: (1) identify the impacts of the major insects and diseases affecting Douglas-fir and their interactions, (2) integrate our understanding of temperature and moisture stress in trees with future climate projections to hypothesize changes in disturbance agent behavior under climate change, and (3) highlight important knowledge gaps in the understanding of the current and projected disturbance regimes in coastal Douglas-fir forests.

Section snippets

Ecological setting

Coastal Douglas-fir forests extend from British Columbia through northwestern California. However, we constrain the geographical extent to Washington and Oregon, west of the crest of the Cascade Mountain Range where Douglas-fir is the dominant tree species (Fig. 1), which has traditionally been called the “Douglas-fir region” (Franklin, 1979, Jensen, 1955). This is a moist temperate forest region is dominated by conifers and has relatively long time periods between high severity natural

Physiological response to water and temperature stress

The proximate effects of climate change on Douglas-fir forests are increased temperature and water stress, particularly during the summer drought. However, they interact with insect pests and diseases to affect tree mortality. Here, we present the basic physiological effects of water and temperature stress in trees to better understand the interactions of biotic disturbance agents within a forest context. Water stress typically appears first in trees growing on sites with features such as

Biotic disturbance agents

Disturbance dynamics vary widely among Douglas-fir forests by structure and age. We focus on the insects and pathogens, which interacting with temperature and moisture stress commonly result in climate-related tree mortality within the region. These include laminated root rot (caused by Phellinus sulphurascens [Pilat]), black stain root disease (caused by Leptographium wagneri [Kendrick] Wingfield), Swiss needle cast (caused by Phaeocryptopus gaeumannii [Rohde] Petrak), and Douglas-fir beetle (

Predicted climate change impacts

There are three components of changing climate likely to influence the ecology of the Douglas-fir region: hotter drier summers, warmer wetter winters, and elevated atmospheric CO2 levels. Climate model simulations suggest that by mid-century the Douglas-fir region will experience hotter drier summers and warmer wetter winters with substantial decreases in snowpack (Mote and Salathé, 2010). Averaged across a number of regionally downscaled climate models, it is predicted that, compared to the

Knowledge gaps

Regardless of climate change scenarios, the biotic disturbance agents discussed above are likely to remain prominent or increase on the landscape. However, significant questions remain regarding interactions of trees, climate, and disturbance factors. We outline key areas in which further study is needed below.

Conclusions

The disturbance regime in Douglas-fir region consists of generally long-term fire return intervals interacting with biotic and abiotic factors, which then interact with the anthropogenic disturbance of forest management. Generalizations beyond the region are limited due to the unique aspects of abiotic and biotic disturbance agents in these Douglas-fir forests. Because climate-disturbance interactions vary depending on topographic and edaphic conditions, management actions should be tailored to

Acknowledgements

The collaborative research described in this article has been funded by the U.S. Environmental Protection Agency (EPA), U.S. Department of Agriculture Forest Service (USFS) and the Oregon State University Swiss Needle Cast Cooperative. It has been subjected to review by the USFS and the EPA National Health and Environmental Effects Research Laboratory’s Western Ecology Division and approved for publication. Approval does not signify that the contents reflect the views of the EPA or the USFS,

References (174)

  • T.E. Kolb et al.

    Observed and anticipated impacts of drought on forest insects and diseases in the United States

    For. Ecol. Manage.

    (2016)
  • B.E. Law et al.

    Carbon implications of current and future effects of drought, fire and management on Pacific Northwest forests

    For. Ecol. Manage.

    (2015)
  • E.H. Lee et al.

    Douglas-fir displays a range of growth responses to temperature, water, and Swiss needle cast in western Oregon, USa

    Agric. For. Meteorol.

    (2016)
  • J.T. Abatzoglou et al.

    Seasonal climate variability and change in the Pacific Northwest of the United States

    J. Clim.

    (2014)
  • J.T. Abatzoglou et al.

    Impact of anthropogenic climate change on wildfire across western US forests

    Proc. Natl. Acad. Sci.

    (2016)
  • W.L. Albright et al.

    Tree growth and climate in the Pacific Northwest, U.S.A.: a broad-scale analysis of changing growth environments

    J. Biogeogr.

    (2013)
  • C.D. Allen et al.

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

    Ecosphere

    (2015)
  • W.R.L. Anderegg et al.

    Consequences of widespread tree mortality triggered by drought and temperature stress

    Nat. Clim. Chang.

    (2012)
  • W.R.L. Anderegg et al.

    Tree mortality from drought, insects, and their interactions in a changing climate

    New Phytol.

    (2015)
  • A. Angert et al.

    Drier summers cancel out the CO2 uptake enhancement induced by warmer springs

    Proc. Natl. Acad. Sci.

    (2005)
  • M.E. Apple et al.

    Morphology and stomatal function of Douglas fir needles exposed to climate change: elevated CO2 and temperature

    Int. J. Plant Sci.

    (2000)
  • G.P. Asner et al.

    Progressive forest canopy water loss during the 2012–2015 California drought

    Proc. Natl. Acad. Sci.

    (2015)
  • M.P. Ayres

    Global change, plant defense, and herbivory

  • S. Bansal et al.

    Climate-related genetic variation in drought-resistance of Douglas-fir (Pseudotsuga menziesii)

    Glob. Chang. Biol.

    (2015)
  • S. Bansal et al.

    Impact of climate change on cold hardiness of Douglas-fir (Pseudotsuga menziesii): environmental and genetic considerations

    Glob. Chang. Biol.

    (2015)
  • Beedlow, P.A., Tingey, D.T., 2007. A summary of NHEERL ecological research on global climate change. EPA 600/R-05/007...
  • P.A. Beedlow et al.

    Rising atmospheric CO2 and carbon sequestration in forests

    Front. Ecol. Environ.

    (2004)
  • B.J. Bentz et al.

    Climate change and bark beetles of the western United States and Canada: direct and indirect effects

    BioScience

    (2010)
  • C.J. Bernacchi et al.

    Improved temperature response functions for models of Rubisco-limited photosynthesis

    Plant Cell Environ.

    (2001)
  • L.T. Berner et al.

    Tree mortality from fires, bark beetles, and timber harvest during a hot and dry decade in the western United States (2003–2012)

    Environ. Res. Lett.

    (2017)
  • B.J. Bond et al.

    Stomatal behavior of four woody species in relation to leaf-specific hydraulic conductance and threshold water potential

    Tree Physiol.

    (1999)
  • J.B. Bradford et al.

    A window of opportunity for climate-change adaptation: easing tree mortality by reducing forest basal area

    Front. Ecol. Environ.

    (2017)
  • E.A. Bray et al.

    Responses to abiotic stresses

  • N. Bréda et al.

    Temperate forest trees and stands under severe drought: a review of ecophysiological responses, adaptation processes and long-term consequences

    Ann. For. Sci.

    (2006)
  • R.T. Brown et al.

    Forest restoration and fire: principles in the context of place

    Conserv. Biol.

    (2004)
  • L.B. Brubaker

    Spatial patterns of tree growth anomalies in the Pacific Northwest

    Ecol.

    (1980)
  • T.N. Buckley

    The control of stomata by water balance

    New Phytol.

    (2005)
  • K.A. Bumbaco et al.

    Three recent flavors of drought in the Pacific Northwest

    J. Appl. Meteorol. Climatol.

    (2010)
  • M.J. Case et al.

    Fine-scale variability in growth-climate relationships of Douglas-fir, North Cascade Range, Washington

    Can. J. For. Res.

    (2005)
  • W.B. Cohen et al.

    Characterizing 23 years (1972–1995) of stand replacement disturbance in western Oregon forests with Landsat imagery

    Ecosystems

    (2002)
  • M.K. Creutzburg et al.

    Forest management scenarios in a changing climate: tradeoffs between carbon, timber, and old forest

    Ecol. Appl.

    (2016)
  • R.O. Curtis et al.

    Timber supply in the Pacific Northwest: managing for economic and ecological values in Douglas-fir forest

    J. For.

    (1996)
  • Curtis, R.O., DeBell, D.S., Miller, R.E., Newton, M.N., St. Clair, B., Stein, W.I., 2007. Silviculture research and the...
  • M.M. Dalton et al.

    Climate Change in the Northwest: Implications for Our Landscapes, Waters, and Communities

    (2013)
  • A.W. D’Amato et al.

    Effects of thinning on drought vulnerability and climate response in north temperate forest ecosystems

    Ecol. Appl.

    (2013)
  • E.H. DeLucia et al.

    Net primary production of a forest ecosystem with experimental CO2 enrichment

    Science

    (1999)
  • J.C. Domec et al.

    Native root xylem embolism and stomatal closure in stands of Douglas-fir and ponderosa pine: mitigation by hydraulic redistribution

    Oecologia

    (2004)
  • Donnegan, J., Campbell, S., Azuma, D. (tech. eds.), 2008. Oregon's forest resources, 2001–2005: Five-year Forest...
  • W.J. Dyck et al.

    Impacts of Forest Harvesting on Long-Term Site Productivity. Springer-Science + Business

    Media

    (1994)
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