scholarly journals Impacts of insect outbreaks on tree mortality, productivity, and stand development

2015 ◽  
Vol 148 (S1) ◽  
pp. S138-S159 ◽  
Author(s):  
David A. MacLean
Keyword(s):  
Mountain Pine Beetle ◽  
Tree Mortality ◽  
Choristoneura Fumiferana ◽  
Population Level ◽  
Historical Record ◽  
Wildlife Habitat ◽  
Insect Population ◽  
Forest Composition ◽  
Stand Development ◽  
Insect Outbreaks

AbstractThe impacts of insect outbreaks on tree mortality, productivity, and stand development in Canada are reviewed, emphasising spruce budworm (Choristoneura fumiferana(Clemens), Lepidoptera: Tortricidae) and mountain pine beetle (Dendroctonus ponderosaeHopkins, Coleoptera: Curculionidae). Reduced growth and survival are a function of insect population and defoliation level. It is feasible to make short-term (annual) predictions of insect population and defoliation based upon sampling, but long-term, multi-year predictions are problematic. Given the historical record, it is expected that outbreaks will occur with relatively predictable frequency and basic host relationships and abiotic constraints will not change dramatically. However, the precision of predictions at fine scales is variable and reduced over time. Relationships between tree growth reduction, survival, and cumulative defoliation or beetle population level are available for major insect species. Understanding insect outbreak effects hinges on mortality, changes in interspecies competition, regeneration, and succession. Altered stand dynamics caused by insects can be interpreted for indicators such as wildlife habitat, old forest, riparian buffer cover, viewscapes, and connectivity. Anthropogenic changes are altering impacts via range expansions, northward shifts, and changes in forest composition. We can better understand effects of insect outbreaks and how best to ameliorate damage through a combination of empirical permanent plot studies, modelling, and manipulative experiments.

Growth dynamics of black spruce in stands located between the 51st and 52nd parallels in the boreal forest of Quebec, Canada

2011 ◽  
Vol 41 (9) ◽  
pp. 1769-1778 ◽  
Author(s):  
Marie-Josée Tremblay ◽  
Sergio Rossi ◽  
Hubert Morin
Keyword(s):  
Boreal Forests ◽  
Black Spruce ◽  
Choristoneura Fumiferana ◽  
Ring Width ◽  
Growth Dynamics ◽  
Stand Dynamics ◽  
Stand Development ◽  
Insect Outbreaks ◽  
Spruce Stands ◽  
Ecological Importance

Despite their ecological importance, the role and effects of insect outbreaks on stand dynamics of the northern boreal forests in North America have still to be demonstrated. The study was conducted between the 51st and 52nd parallels in Quebec, Canada, to identify mechanisms governing regeneration of high-latitude stands by investigating variations in growth of trees during stand development. Chronologies of tree-ring width and individual dynamics of growth in height and volume were assessed in black spruce ( Picea mariana (Mill.) B.S.P) of one even-aged and five uneven-aged stands. Uneven-aged stands contained trees up to 340 years old and representing almost every age class. Several growth reductions were observed that were synchronized between stands and were characterized by high amplitudes but different percentages of affected trees. These reductions were followed by marked growth releases. Even if the absence of nonhost species prevented the building of chronologies that could confirm the origin of growth reductions, the findings suggested that spruce budworm ( Archips fumiferana Clemens [syn.: Choristoneura fumiferana (Clemens)]) outbreaks contribute to the formation and maintenance of the uneven-aged structure of older black spruce stands at high latitudes.

The influence of partial cutting on mountain pine beetle-caused tree mortality in Black Hills ponderosa pine stands

2007 ◽  
Author(s):  
J.M. Schmid ◽  
S.A. Mata ◽  
R.R. Kessler ◽  
J.B. Popp
Keyword(s):  
Ponderosa Pine ◽  
Mountain Pine Beetle ◽  
Tree Mortality ◽  
Black Hills ◽  
Partial Cutting ◽  
Mountain Pine ◽  
Pine Beetle ◽  
Pine Stands

scholarly journals Over half of western United States' most abundant tree species in decline

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Hunter Stanke ◽  
Andrew O. Finley ◽  
Grant M. Domke ◽  
Aaron S. Weed ◽  
David W. MacFarlane
Keyword(s):  
United States ◽  
Tree Species ◽  
Tree Mortality ◽  
Temperate Forests ◽  
Size Structure ◽  
Forest Disturbance ◽  
Population Decline ◽  
Western United States ◽  
Scale Transformation ◽  
Forest Composition

AbstractChanging forest disturbance regimes and climate are driving accelerated tree mortality across temperate forests. However, it remains unknown if elevated mortality has induced decline of tree populations and the ecological, economic, and social benefits they provide. Here, we develop a standardized forest demographic index and use it to quantify trends in tree population dynamics over the last two decades in the western United States. The rate and pattern of change we observe across species and tree size-distributions is alarming and often undesirable. We observe significant population decline in a majority of species examined, show decline was particularly severe, albeit size-dependent, among subalpine tree species, and provide evidence of widespread shifts in the size-structure of montane forests. Our findings offer a stark warning of changing forest composition and structure across the western US, and suggest that sustained anthropogenic and natural stress will likely result in broad-scale transformation of temperate forests globally.

Forest composition, host-population density, and parasitism of spruce budworm Choristoneura fumiferana eggs by Trichogramma minutum

2003 ◽  
Vol 107 (3) ◽  
pp. 215-227 ◽  
Author(s):  
Debora Quayle ◽  
Jacques Régnière ◽  
Naomi Cappuccino ◽  
Alain Dupont
Keyword(s):  
Population Density ◽  
Choristoneura Fumiferana ◽  
Spruce Budworm ◽  
Host Population ◽  
Forest Composition ◽  
Trichogramma Minutum

Response of high-elevation limber pine (Pinus flexilis) to multiyear droughts and 20th-century warming, Sierra Nevada, California, USA

2007 ◽  
Vol 37 (12) ◽  
pp. 2508-2520 ◽  
Author(s):  
Constance I. Millar ◽  
Robert D. Westfall ◽  
Diane L. Delany
Keyword(s):  
20Th Century ◽  
Sierra Nevada ◽  
Mountain Pine Beetle ◽  
Tree Mortality ◽  
High Elevation ◽  
Dwarf Mistletoe ◽  
Lower Growth ◽  
Pinus Flexilis ◽  
Limber Pine ◽  
Temperature And Precipitation

Limber pine ( Pinus flexilis James) stands along the eastern escarpment of the Sierra Nevada, California, experienced significant mortality from 1985 to 1995 during a period of sustained low precipitation and high temperature. The stands differ from old-growth limber pine forests in being dense, young, more even-aged, and located in warmer, drier microclimates. Tree growth showed high interannual variability. Relative to live trees, dead trees over their lifetimes had higher series sensitivity, grew more variably, and had lower growth. Although droughts recurred during the 20th century, tree mortality occurred only in the late 1980s. Significant correlations and interactions of growth and mortality dates with temperature and precipitation indicate that conditions of warmth plus sustained drought increased the likelihood of mortality in the 1985–1995 interval. This resembles a global-change-type drought, where warming combined with drought was an initial stress, trees were further weakened by dwarf mistletoe ( Arceuthobium cyanocarpum (A. Nels. ex Rydb.) A. Nels.), and proximally killed by mountain pine beetle ( Dendroctonus ponderosae Hopkins). However, the thinning effect of the drought-related mortality appears to have promoted resilience and improved near-term health of these stands, which suffered no additional mortality in the subsequent 1999–2004 drought.

scholarly journals Landscape Topoedaphic Features Create Refugia from Drought and Insect Disturbance in a Lodgepole and Whitebark Pine Forest

Forests ◽  
2018 ◽  
Vol 9 (11) ◽  
pp. 715 ◽  
Author(s):  
Jennifer Cartwright
Keyword(s):  
Climate Change ◽  
Mountain Pine Beetle ◽  
Pine Forest ◽  
Boosted Regression Trees ◽  
Pine Forests ◽  
Whitebark Pine ◽  
Insect Outbreaks ◽  
Landscape Characteristics ◽  
Mountain Pine ◽  
Pine Beetle

Droughts and insect outbreaks are primary disturbance processes linking climate change to tree mortality in western North America. Refugia from these disturbances—locations where impacts are less severe relative to the surrounding landscape—may be priorities for conservation, restoration, and monitoring. In this study, hypotheses concerning physical and biological processes supporting refugia were investigated by modelling the landscape controls on disturbance refugia that were identified using remotely sensed vegetation indicators. Refugia were identified at 30-m resolution using anomalies of Landsat-derived Normalized Difference Moisture Index in lodgepole and whitebark pine forests in southern Oregon, USA, in 2001 (a single-year drought with no insect outbreak) and 2009 (during a multi-year drought and severe outbreak of mountain pine beetle). Landscape controls on refugia (topographic, soil, and forest characteristics) were modeled using boosted regression trees. Landscape characteristics better explained and predicted refugia locations in 2009, when forest impacts were greater, than in 2001. Refugia in lodgepole and whitebark pine forests were generally associated with topographically shaded slopes, convergent environments such as valleys, areas of relatively low soil bulk density, and in thinner forest stands. In whitebark pine forest, refugia were associated with riparian areas along headwater streams. Spatial patterns in evapotranspiration, snowmelt dynamics, soil water storage, and drought-tolerance and insect-resistance abilities may help create refugia from drought and mountain pine beetle. Identification of the landscape characteristics supporting refugia can help forest managers target conservation resources in an era of climate-change exacerbation of droughts and insect outbreaks.

scholarly journals How does water yield respond to mountain pine beetle infestation in a semiarid forest?

2021 ◽  
Vol 25 (9) ◽  
pp. 4681-4699
Author(s):  
Jianning Ren ◽  
Jennifer C. Adam ◽  
Jeffrey A. Hicke ◽  
Erin J. Hanan ◽  
Christina L. Tague ◽  
...  
Keyword(s):  
Mountain Pine Beetle ◽  
Tree Mortality ◽  
Hydrologic Model ◽  
Water Yield ◽  
Driving Mechanisms ◽  
Mountain Pine ◽  
Pine Beetle ◽  
Interannual Climate Variability ◽  
Hydrologic Responses

Abstract. Mountain pine beetle (MPB) outbreaks in the western United States result in widespread tree mortality, transforming forest structure within watersheds. While there is evidence that these changes can alter the timing and quantity of streamflow, there is substantial variation in both the magnitude and direction of hydrologic responses, and the climatic and environmental mechanisms driving this variation are not well understood. Herein, we coupled an eco-hydrologic model (RHESSys) with a beetle effects model and applied it to a semiarid watershed, Trail Creek, in the Bigwood River basin in central Idaho, USA, to examine how varying degrees of beetle-caused tree mortality influence water yield. Simulation results show that water yield during the first 15 years after beetle outbreak is controlled by interactions between interannual climate variability, the extent of vegetation mortality, and long-term aridity. During wet years, water yield after a beetle outbreak increased with greater tree mortality; this was driven by mortality-caused decreases in evapotranspiration. During dry years, water yield decreased at low-to-medium mortality but increased at high mortality. The mortality threshold for the direction of change was location specific. The change in water yield also varied spatially along aridity gradients during dry years. In wetter areas of the Trail Creek basin, post-outbreak water yield decreased at low mortality (driven by an increase in ground evaporation) and increased when vegetation mortality was greater than 40 % (driven by a decrease in canopy evaporation and transpiration). In contrast, in more water-limited areas, water yield typically decreased after beetle outbreaks, regardless of mortality level (although the driving mechanisms varied). Our findings highlight the complexity and variability of hydrologic responses and suggest that long-term (i.e., multi-decadal mean) aridity can be a useful indicator for the direction of water yield changes after a disturbance.

scholarly journals Carbon Storage Responses of Subalpine Forests to Moutain Pine Beetle Outbreaks Under Current and Altered Climate Regimes in Western North America

2008 ◽  
Vol 31 ◽  
pp. 93-96
Author(s):  
Daniel Kashain
Keyword(s):  
Carbon Storage ◽  
Mountain Pine Beetle ◽  
Carbon Dynamics ◽  
Stand Development ◽  
Climate Scenarios ◽  
Subalpine Forests ◽  
Outbreak Management ◽  
Forest Carbon Storage ◽  
Pine Beetle ◽  
Landscape Scales

Understanding how climate, disturbances, and carbon storage interact in subalpine forests is critical for assessing the role of this ecosystem in the global carbon budget under altered climate scenarios. Most research to date in western North American forests has focused on wildfire effects on carbon storage and net ecosystem productivity (NEP). The current extensive insect outbreak in this region, however, suggests that insects such as the mountain pine beetle (MPB) are an important driver of carbon dynamics and may determine whether western landscapes are carbon sinks or sources. The overall objective of this study is therefore to understand how MPB outbreaks affect forest carbon storage at stand and landscape scales under multiple climate scenarios. Specific objective include examining how carbon storage changes with stand development following beetle outbreaks, how variability in outbreak extent, frequency, and post-outbreak stand development affect landscape-scale carbon storage, and how beetle outbreaks and climate interact. This research will, for the first time, provide data documenting post-outbreak carbon dynamics under current and altered climate scenarios. These data will provide the basis for developing a carbon-based, ecological rationale for future outbreak management in western forests.

Recruitment patterns following a severe drought: long-term compositional shifts in Patagonian forests

2008 ◽  
Vol 38 (12) ◽  
pp. 3002-3010 ◽  
Author(s):  
María L. Suarez ◽  
Thomas Kitzberger
Keyword(s):  
Vegetation Change ◽  
Forest Canopy ◽  
Tree Mortality ◽  
Forest Composition ◽  
Future Climate Change ◽  
Severe Drought ◽  
Climate Change Scenarios ◽  
Recruitment Pattern ◽  
Recruitment Patterns

Severe droughts have the potential of inducing transient shifts in forest canopy composition by altering species-specific adult tree mortality patterns. However, permanent vegetation change will occur only if tree recruitment patterns are also affected. Here, we analyze how a massive mortality event triggered by the 1998–1999 drought affected adult and sapling mortality and recruitment in a mixed Nothofagus dombeyi (Mirb.) Blume – Austrocedrus chilensis (D. Don) Flor. et Boult. forests of northern Patagonia. Comparing drought-induced and tree-fall gaps, we assessed changes in forest composition, microenvironments, and seedling density and survival of both species. Drought-kill disturbance shifted species composition of both canopy and sapling cohorts in favour of A. chilensis. Drought gaps were characterized by a shadier and more xeric environment, affecting the recruitment pattern of N. dombeyi seedlings. The seedling cohort was composed mostly of A. chilensis, and its survival was always higher than that of N. dombeyi. Additionally, A. chilensis seedlings showed higher plasticity than N. dombeyi seedlings, increasing its root to shoot ratios in drought gaps. The results suggest that extreme drought itself is a strong driving force in forest dynamics, with important imprints on forest landscapes. Future climate-change scenarios, projecting an increased in frequency and severity of droughts, alert us about expected long-term compositional shifts in many forest ecosystems.

Modelling Landscape-level Effects of Reduced Herbicide Use in Two Forests in Northern Ontario

2011 ◽  
Vol 87 (02) ◽  
pp. 290-309 ◽  
Author(s):  
Jennifer Dacosta ◽  
Kandyd Szuba ◽  
F. Wayne Bell ◽  
Tom Moore ◽  
Ken Lennon ◽  
...  
Keyword(s):  
Forest Management ◽  
Scale Up ◽  
Transportation Cost ◽  
Spatial Modelling ◽  
Wildlife Habitat ◽  
Forest Composition ◽  
Wood Supply ◽  
Forest Management Planning ◽  
Herbicide Use ◽  
Landscape Level

In Ontario, forest management planning requires that legal obligations to sustain forest composition and pattern, wildlife habitat, and other values are met, while at the same time addressing, for example, wood supply needs, costs, forest access, and stakeholder concerns. One of the latter is pressure to reduce herbicide use. Stand-level effects of vegetation management alternatives have been documented, but how these effects scale up to the landscape-level and affect the achievement of social, ecological, and economic objectives embedded in forest management plans (FMPs) remains uncertain. We applied nine modelling scenarios in the context of approved FMPs to explore the potential landscape-level effects of replacing herbicide use with an alternative (brush saw) for two large forests in northeastern Ontario. Results of non-spatial and spatial modelling over 60 years suggested that although herbicides are applied to only 25% to 34% of the harvested area in these forests, reductions in use would affect: (i) overall wood supply, with 14% to 44% less conifer and 6% to 17% less hardwood available; (ii) habitat supply, with less habitat for species preferring recent disturbances and more habitat for species preferring mature and older forest; (iii) costs, with wood transportation cost increasing by 16% to 20% and increased spending on silviculture; (iv) size and distribution of cutblocks and disturbance patches, with more small patches; and (v) the extent of the active road network, which would increase.

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