Abstract. Mountain pine beetle (MPB) outbreaks in the western United States result inwidespread 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.
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Mountain pine beetles and ecological imaginaries: The social construction of forest insect disturbance
Mountain Pine Beetle (MPB) outbreaks bear attributions at multiple scales, from the practices of local extractive industries to state and federal forest management to global climate change. Since 1996, an outbreak of MPB has swept across nearly 3.4 million acres in north central Colorado. The area affected is constituted by a heterogeneous group of communities, and provides an opportunity to examine how institutional forces pattern experiences of the natural world and emergent environmental narratives. This work examines the narratives of local community and regional organizations, along with interviews and household survey data to consider culturally situated experiences and framings of the outbreak. Tracing environmental narratives is part of understanding different environmental vulnerabilities, which is essential to developing management regimes that are inclusive and ultimately sustainable.
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- Award ID(s):
- 1733990
- NSF-PAR ID:
- 10152054
- Date Published:
- Journal Name:
- J. Urquhart, C. Potter, and M. Marzano (eds.) Human Dimensions in Forest and Tree Health. London: Palgrave Macmillan
- Page Range / eLocation ID:
- 77–107
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Fuel and restoration treatments seeking to mitigate the likelihood of uncharacteristic high‐severity wildfires in forests with historically frequent, low‐severity fire regimes are increasingly common, but long‐term treatment effects on fuels, aboveground carbon, plant community structure, ecosystem resilience, and other ecosystem attributes are understudied. We present 20‐year responses to thinning and prescribed burning treatments commonly used in dry, low‐elevation forests of the western United States from a long‐term study site in the Northern Rockies that is part of the National Fire and Fire Surrogate Study. We provide a comprehensive synthesis of short‐term (<4 years) and mid‐term (<14 years) results from previous findings. We then place these results in the context of a mountain pine beetle (MPB;
Dendroctonus ponderosae ) outbreak that impacted the site 5–10 years post‐treatment and describe 20‐year responses to assess the longevity of restoration and fuel reduction treatments in light of the MPB outbreak. Thinning treatments had persistently lower forest density and higher tree growth, but effects were more pronounced when thinning was combined with prescribed fire. The thinning+prescribed fire treatment had the additional benefit of maintaining the highest proportion of ponderosa pine (Pinus ponderosa ) for overstory and regeneration. No differences in understory native plant cover and richness or exotic species cover remained after 20 years, but exotic species richness, while low relative to native species, was still higher in the thinning+prescribed fire treatment than the control. Aboveground live carbon stocks in thinning treatments recovered to near control and prescribed fire treatment levels by 20 years. The prescribed fire treatment and control had higher fuel loads than thinning treatments due to interactions with the MPB outbreak. The MPB‐induced changes to forest structure and fuels increased the fire hazard 20 years post‐treatment in the control and prescribed fire treatment. Should a wildfire occur now, the thinning+prescribed fire treatment would likely have the lowest intensity fire and highest tree survival and stable carbon stocks. Our findings show broad support that thinning and prescribed fire increase ponderosa pine forest resilience to both wildfire and bark beetles for up to 20 years, but efficacy is waning and additional fuel treatments are needed to maintain resilience. -
Miller, Eva (Ed.)The recent outbreak of COVID-19, considered as being a lethal pandemic by the World Health Organization, has caused profound changes in the educational system within the U.S and across the world. Overnight, universities and their educators had to switch to a largely online teaching format, which challenged their capacity to deliver learning content effectively to STEM students. Students were forced to adapt to a new learning environment in the midst of challenges in their own lives due to the COVID-19 effects on society and professional expectations. The main purpose of this paper is to investigate faculty perceptions of STEM student experiences during COVID-19. Through a qualitative methodology consisting of one-hour zoom interviews administered to 32 STEM faculty members from six U.S. Universities nationwide, faculty narratives regarding student and faculty experiences during COVID-19 were obtained. The qualitative research approach involved identifying common themes across faculty experiences and views in these narratives. Some of the categories of emerging themes associated with faculty perceptions on student and faculty experiences included: student struggles and challenges, student cheating and the online environment, faculty and student adaptability, faculty and student needs and support, and university resources and support. Best practices to facilitate online teaching and learning employed by STEM faculty were also discussed. Key findings revealed that students and faculty had both positive and negative experiences during COVID-19. Additionally, there was a greater need for consistent policies to improve the online student learning experiences. Recommendations to improve STEM student experiences include increased institutional resources and collaboration between faculty and the university administrators to provide a coherent online learning environment. Preliminary findings also provide insights to enhance institutional adaptability and resilience for improving STEM student experiences during future pandemics. Future research should continue to explore institutional adaptation strategies that enhance STEM student learning during pandemics.more » « less
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Context: Growth releases of individuals that survive disturbances are important compensatory response mechanisms that contribute to ecological resilience. However, the role of fine-scale spatial heterogeneity in shaping compensatory growth responses is poorly understood for many broad-scale disturbances. Objectives: We quantified how fine-scale spatial structure affects individual and aggregate tree growthleading up to and following a severe mountain pine beetle (MPB; Dendroctonus ponderosae) outbreak. We asked: (1) How does individual tree growth vary with tree- and neighborhood-scale characteristics? (2) How do within-stand aggregate growth and overstory recruitment vary with neighborhood-scale characteristics? Methods: We used a spatially explicit long-term monitoring dataset of a subalpine lodgepole pine (Pinus contorta var. latifolia) forest (in Colorado, USA) in which every tree ≥ 5 cm diameter was measured and mapped prior to (1989, 2004) and following (2018) a severe MPB outbreak (2003–2011). We used spatial regression to characterize drivers of growth. Results: Overall, we found strong evidence for post-outbreak compensatory responses across spatial scales. Neighborhood characteristics shaped both individual and aggregate growth, with the magnitude of growth strongly mediated by pre-outbreak neighborhood structure and neighborhood mortality. Variation in tree-scale growth, combined with the spatial arrangement of surviving trees, resulted in highly variable emergent patterns of aggregate growth and recruitment. Conclusion: Our findings highlight the importance of fine-scale landscape configuration in shaping forest resilience. Quantifying compensatory responses in a spatially explicit framework at different scales is critical for modeling post-disturbance forest dynamics, which is increasingly important as climate warms and forest disturbance regimes change.more » « less
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1007/978-3-319-76956-1_4
