Gregory Ettl

Dr. Gregory Ettl


Research Focus & Metrics

Academic Career Length

14Years (2013-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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28 November 2018 in Forests
Verified
Journal Article
Open access
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LALORD AMEYAW
LORD AMEYAW
GEGregory Ettl
Gregory Ettl
KLKristy Leissle
Kristy Leissle
GAGilbert J. Anim-Kwapong
Gilbert J. Anim-Kwapong
This study investigates the knowledge and perception of smallholder cocoa farmers on the potential impacts of climate change on cocoa production in Ghana. It addresses opinions on the inclusion of climate change mitigation strategies (such as Reducing Emissions from Deforestation and Forest Degradation—REDD+) into cocoa production, and potential obstacles and roles of stakeholders in ensuring community acceptance of such strategies in a unique multiple land use area—the Krokosua Hills Forest Reserve. Data from the Ghana Meteorological Agency and through survey of 205 cocoa farmers were assessed with Mann-Kendall, Kruskal Wallis and Mann-Whitney tests. Farmers’ perceptions of changes in climate were notably diverse and did not always match historic weather data, but accurately described increases in temperature and drought which are linked to cocoa productivity. Farmers appreciate the importance of tree maintenance for ecosystem services but were skeptical of financially rewarding climate change strategies which favor tree protection. Cultural practices associated with cocoa production encourage carbon release and may pose a threat to the objectives of REDD+. Farmers’ experience on the land, interactions with other farmers, government extension agents and cocoa buyers all influence cocoa agroforestry practices in the area, and communication through existing entities (particularly extension agents) presents a pathway to community acceptance of climate change mitigation strategies. The study recommends reforms in REDD+ strategies to adopt flexible and participatory frameworks to facilitate adoption and acceptability due to pronounced heterogeneity in community perceptions and knowledge of climate change and related issues.

18 June 2019 in Frontiers in Microbiology
Verified
Journal Article
Open access
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MAMatthew M. Aghai
Matthew M. Aghai
ZKZareen Khan
Zareen Khan
MJMatthew R. Joseph
Matthew R. Joseph
ASAubrey M. Stoda
Aubrey M. Stoda
ASAndrew W. Sher
Andrew W. Sher
SDSharon L. Doty
Sharon L. Doty
Increased frequency of droughts and degraded edaphic conditions decreases the success of many reforestation efforts in the Pacific Northwest. Microbial endophyte consortia have been demonstrated to contribute to plant growth promotion and protection from abiotic and biotic stresses – specifically drought conditions – across a number of food crops but for limited tree species. Our research aimed to investigate the potential to improve establishment of economically and ecologically important conifers through a series of in situ field trials and ex situ simulations. Microbial endophyte consortia from Salicaceae, previously shown to confer drought tolerance, and conifer endophyte strains with potentially symbiotic traits were selected for trials with Douglas-fir (Pseudotsuga menziesii) and western redcedar (Thuja plicata). Reductive experimentation was used to subject seedlings to a spectrum of simulated drought levels or presence/absence of fertilizer, testing hypotheses that endophyte consortia impart improved drought resistance and growth promotion, respectively. Inoculation from Salicaceae consortia significantly (p ≤ 0.05) improved survival among seedlings of both species subject to increasing drought stress, with T. plicata seedlings surviving at twofold higher rates in extreme drought conditions. Both species demonstrated improved growth 540 days after inoculation of seed with conifer derived consortia. In the carefully controlled greenhouse experiments with both species, seedling Fv/Fm and SPAD values remained significantly (p ≤ 0.05) more stable in inoculated treatment groups as stress increased. Our findings confirm that multi-strain consortia may be applied as seed or field amendment to conifers, and the approach is efficient in garnering a positive growth response and can mitigate abiotic stressors.

12 October 2015 in Forests
Verified
Journal Article
Open access
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ZKZareen Khan
Zareen Khan
SKShyam L. Kandel
Shyam L. Kandel
DRDaniela Ramos
Daniela Ramos
GEGregory Ettl
Gregory Ettl
SKSoo-Hyung Kim
Soo-Hyung Kim
SDSharon L Lafferty Doty
Sharon L Lafferty Doty
Douglas-fir (Pseudotsuga menziesii) seedlings are periodically challenged by biotic and abiotic stresses. The ability of endophytes to colonize the interior of plants could confer benefits to host plants that may play an important role in plant adaptation to environmental changes. In this greenhouse study, nursery-grown Douglas-fir seedlings were inoculated with diazotrophic endophytes previously isolated from poplar and willow trees and grown for fifteen months in nutrient-poor conditions. Inoculated seedlings had significant increases in biomass (48%), root length (13%) and shoot height (16%) compared to the control seedlings. Characterization of these endophytes for symbiotic traits in addition to nitrogen fixation revealed that they can also solubilize phosphate and produce siderophores. Colonization was observed through fluorescent microscopy in seedlings inoculated with gfp- and mkate-tagged strains. Inoculation with beneficial endophytes could prove to be valuable for increasing the production of planting stocks in forest nurseries.

25 July 2018 in Forests
Verified
Journal Article
Open access
PDF file
DDDavid Diaz
David Diaz
SLSara Loreno
Sara Loreno
GEGregory Ettl
Gregory Ettl
BDBrent Davies
Brent Davies
Forest management choices offer significant potential to mitigate global climate change and biodiversity loss. To illuminate tradeoffs relevant to policymakers, forest sector stakeholders, and consumers of forest products, we utilize three Key Performance Indicators—average carbon storage in the forest and wood products; cumulative timber output; and discounted cash flow—to compare four alternative management scenarios for Douglas-fir forests on 64 parcels across western Oregon and Washington. These scenarios are designed to meet one of two alternative management objectives: (i) maximize Net Present Value; or (ii) maximize sustained timber yield; according to one of two alternative sets of forest practice constraints: (i) compliance with minimum Oregon/Washington Forest Practices Act (FPA) rules; or (ii) two key requirements (increased green tree retention and wider riparian buffers) of Forest Stewardship Council (FSC) certification. Improved performance in terms of carbon storage for these alternatives generally also corresponded with reduced Net Present Value and timber yields. The gap between FSC and FPA performance indicators was wider in Oregon than Washington, which is primarily attributed to the higher level of stream protection required under Washington versus Oregon FPA rules. We observed consistently higher average carbon storage per cumulative timber output among FSC scenarios relative to business-as-usual, indicating FSC-certified wood carries an embedded carbon benefit. Our findings highlight options for targeted policies to incentivize management that increases carbon storage and minimizes disruptions in timber output, as well as for narrowing the financial gap (or opportunity cost) that would be involved in a transition away from contemporary common practice on industrial timberlands in the coastal Douglas-fir forests of the Pacific Northwest.

26 June 2013 in Forest Science
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Journal Article
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SRSergey S. Rabotyagov
Sergey S. Rabotyagov
STSandor Toth
Sandor Toth
GEGregory Ettl
Gregory Ettl
ECOSEL is a voluntary market framework for private provision of forest ecosystem services. Multiobjective optimization is used in conjunction with a unique fund

24 March 2026 in Forests
Verified
Journal Article
Open access
PDF file
GEGregory Ettl
Gregory Ettl
CBCourtney R. Bobsin
Courtney R. Bobsin
BBBernard T. Bormann
Bernard T. Bormann
DHDano Holt
Dano Holt
There is limited information on the effects of irregular-spaced and clumped planting on forest production and structural diversity. We explored Tagetes patula L. development as a model system to demonstrate stand development under varying planting patterns, and conceptualized in the context of Pseudotsuga menziesii (Mirb.) Franco mesic production forests of the Pacific Northwestern USA. Two variable planting patterns, clumps of 24 plants and of four plants, were compared to square regular patterns in replicate growing boxes. Spatial patterns were compared post-planting and at maturation, along with stand-level metrics and final dry weights, and stand structural statistics were used to compare production and diversity. The clumped spatial structure of 24-plant clumps was maintained to maturity. Groups of four plants maintained clumping at small scales and regular patterns at larger scales. Initial Regular-Square spacing remained at 2 cm at maturity but became indistinguishable from random patterns at larger scales. There was (1) overall greater mean directional index for the Large-Clumped patterns and greater spatial complexity indices for both clumped patterns, (2) greater social class (size) mean mingling index for small clumps, and (3) higher mean dominance index and mean differentiation index and lower crown volume complexity and height-to-diameter ratios for Regular-Square spacing. The structural complexity was accompanied by limited differences in dried weights by plant tissue (total weight, stem, leaf, flower weight) or plant biometric parameters (stem straightness, crown ratio, crown volume, number of leaves and flowers). The results from irregular planted marigold stand development are discussed in the context of increasing forest stand complexity, potentially without compromising productivity.