University of Idaho Forest Regeneration
CURRENT RESEARCH PROJECTS
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Root Growth Potential of Inland Northwest Seedlings
Root growth potential (RGP) is used to evaluate seedling vitality (i.e. free of defect and physiological damage) following nursery culture. We are refining a rapid RGP assessment method using mist chambers in a laboratory with controlled environmental conditions. Research focuses on modifying chamber testing environment, quantifying species-specific and container size-specific new root production, and relationships between RGP results and outplanting performance across the Inland Northwest. This research is funded by PotlatchDeltic Corp., Hancock Forest Management, and the Idaho Department of Lands.
Maternal Environment and Drought-Conditioning Effects on Seedling Root System Architecture & Physiology
Planting seedlings is the first step to reforest recently disturbed sites, yet seedling performance can be poor if they do not quickly acclimate with the planting site. This limits forest productivity and requires substantial investment. One frontier in forestry is identifying tree seedling genotypes and phenotypes that maximize seedling survival and early growth. Projects examining root system of architecture (RSA) are limited for seedlings even though extensive research for agriculture plants shows its importance for maximizing productivity by optimizing resource capture. RSA can be manipulated in the nursery by modifying growing regimes that may affect the RSA following planting. Testing cultural regimes that modify the RSA in the nursery to better acclimate seedlings to drought conditions is important for seedling productivity and many become more important with more frequent, severe, and longer duration droughts. This project will focus on western larch and black walnut for the following objectives: (i) Characterize RSA of seedlings growth under different drought acclimation regimes in the nursery, (ii) Examine partitioning of RSA between intact root plugs and egressed roots in the field, and (iii) Assess the effects of drought acclimation on survival and growth of seedlings in relation to RSA. Our approach to studying seedling RSA includes greenhouse, laboratory, and field studies. RSA will be manipulated in the greenhouse by imposing drought acclimation treatments followed by examining maximum RSA in lab-grown seedlings, and finally examining RSA in the field. Results will improve nursery practices and identify RSA traits important for seedling productivity. This project is funded through USDA National Institute of Food and Agriculture, Agriculture and Food Research Initiative Grant # 2019-67014-29109.
Mountain Huckleberry Responses to Root Herbivory and Biological Control Options
Root herbivores are major horticultural pests often requiring chemical insecticides to control. Infected plants are disposed as they are deemed unacceptable for sale. In seedling crops, healthy roots are important for survival and growth following planting, although some root damage may be acceptable. We lack reliable tools to determine damage thresholds for field planted seedlings, especially those infected with black vine weevil (BVW) in nurseries. We also need better information on the biological control efficacy for BVW and potential residual control of native pests. This project will improve understanding of plant responses to root herbivory by BVW, while comparing chemical and biological control options. We focus on huckleberry, a highly valued shrub species that is widely planted across the Northwest that has declined substantially over the last 50+ years. Our specific objectives include: (i) examine how BVW root damage influences seedling root physiology and growth, and (ii) single and combined applications of chemical insecticides, azadirachtin, and a nematode control BVW and residual control of rusty tussock moth. This project is funded through USDA National Institute of Food and Agriculture, Agriculture and Food Research Initiative Grant # 2020-68008-31404.
Identifying Factors Influencing Post-Planting Seedling Success Across the Inland Northwest
The Inland Northwest plants over 15 million seedling per year. Seedling mortality varies considerably year-to-year and from site-to-site. Our research is examining mortality of survival of Interior Douglas-fir and western larch seedlings across a broad network of plots. Our models are incorporating root growth potential, genetic improvement, initial seedling size, planting season weather, competing vegetation, and soil metrics. Models will be developed into a decision-support system for land managers to enhance reforestation success across the region. This project is funded by the National Science Foundation Awards IIP-1540045 and IIP-1916699.
Seedling Survival and Growth Responses to Post-Planting Competition Control
Post-planting competition removal is often necessary to enhance survival and growth of recently planting seedlings due to prolific re-development of non-tree vegetation following site preparation treatments. Competition intensity differs depending on the cover of the dominant life forms: grasses, ferns, and forbs strongly compete for water in upper soil horizons where the majority of new seedling root growth occurs. This project has two objectives: (i) examine growth and survival responses of western larch and Interior Douglas-fir seedlings following post-planting competition removal designed to target non-native and highly-competitive forbs across a site productivity gradient in northern Idaho, and (ii) examine targeted competition removal intensity on microsite soil moisture and temperature, and seedling growth and survival and low and high productivity sites in Idaho. This project is funded by PotlatchDeltic Corp.
Genetic x Environment Effects on Western Larch Productivity
Western larch is one of the most widely planted conifer species in the Inland Northwes due to desirable wood properties, rapid growth, and disease and insect resistance. This joint project between the Inland Empire Tree Improvement Cooperative (IETIC) and Intermountain Forestry Cooperative (IFC) at the University of Idaho, will examine performance of isolated superior western larch genetics in the greenhouse and in the field. The greehouse component will examine physiological and morphological differences among families. Seedlings will be grown at the University of Idaho Pitkin Tree Nursery, and then outplanted in a field experiment examining the effects of site quality, pure and mixed-genetics planting, and competition control on early stand performance across the region. This project is funded by the National Science Foundation Award IIP-1540045.
Western Larch Response to Thinning Intensity and Understory Vegetation Management
Thinning is proposed to enhance forest vigor, resistance and resilience to biotic and abiotic disturbances, and increase residual tree growth. In the Northern Rockies, thinning typically stimulates the development of understory shrub and herbaceous vegetation The development of understory vegetation may hinder tree responses to thinning due to increased competition for water especially under drought conditions. This project will examine the effects of thinning intensity (unthinned, 170, and 300 residual trees per acre) and understory vegetation management (no control and complete control) on surface and sub-surface soil moisture, tree crown characteristics, and tree and stand growth.This project was funded by the USDA National Institute of Food and Agriculture, McIntire-Stennis project under accession number 1008381.
PAST PROJECTS
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Floristic Diversity across Northern Rockies Right-of-Ways
Rights-of-way (ROW) span thousands of miles across the Inland Northwest alone. These areas are managed to minimize tree cover and promote low-growing communities of shrubs, forbs, ferns, and grasses. ROW often have diverse early-seral composition that that is absent across most of the region where dense canopy cover dominates. In additon, ROWs provide corridors for animals and promote growing conditions conducive to pollinators. We are examining floristic diversity across transmission ROW across the moist forest of the northern Rocky Mountains in Idaho and Montana. This project was funded by Avista Utilities.
Multi-decadal Responses of Moist Northern Rockies Forests to Site Preparation
In 1982, a study was initiated on the USDA Forest Service Priest River Experimental Forest (PREF) in northern Idaho to test the effects of four different site preparation treatments on western white pine and Douglas-fir growth and soil properties. Treatments included (1) no site preparation, (2) scalping which removed the organic horizon, (3) bedding which mixed the organic and upper mineral horizons, and (4) bedding plus vegetation control. Each treatment combination was replicated at two elevations. Tree will be remeasured and combined with previous inventories to assess tree and stand responses to treatments over time. Dendrochronology and destructive sampling will be used to examine changes in stem diameter and height growth, and growth efficiency in response to site preparation treatments. This project was funded by the USDA National Institute of Food and Agriculture, McIntire-Stennis project under accession number 1008381.
Seasonal Trends in Biological Activity of Loblolly Pine and Sweetgum Bark
Pulp and paper processing facilities (and emerging pellet facilities) are a major economic contributor to the economy of the Southeast. Phytochemical extraction from tree bark has the potential to substantially increase revenue generated from these facilities, but fundamental understanding of phytochemical composition and content in tree bark and the effects of environmental variability on phytochemicals is poorly understood for common tree species in the Southeast. The project objective is to assess the effects of season and tree size on phytochemicals in bark of loblolly pine and sweetgum. Bark extractives are being tested for their effects on inhibiting bacterial growth and quenching low-density lipoprotein oxidation. Models are being developed to predict active phytochemical content for each season of the year across a range of tree size.
Loblolly Pine Stable Carbon and Oxygen Isotope Response to Planting Density and Thinning
13-14 year old loblolly pine planting density trials in southern Arkansas are being used to examine the effects of contrasting initial planting densities (200, 450, 700, 1200 trees per acre) and subsequent thinning intensity on foliar stable isotopes to better understand physiological responses to thinning, in particular intrinsic water-use efficiency.
Neighborhood Effects on Shortleaf and Loblolly Pine Productivity
This project examined the effects of neighborhood species composition and inter-tree competition on individual shortleaf and loblolly pine crown characteristics and stem increment. The study was conducted in unmanaged mature (80-120 years old), naturally regenerated pine-hardwood stands on the Upper West Gulf Coastal Plain of southern Arkansas.
Carbon Storage in Managed and Unmanaged Mature Natural-Origin Pine-Hardwood Stands
This project examined trends in aboveground biomass of understory hardwood species using allometric modeling. These models were combined with inventory data data to examine carbon storage in unmanaged and managed (selective overstory tree removal) naturally-regenerated Upper West Gulf Coastal Plain stands in Arkansas. Carbon partitioning between canopy strata, tree species, and vegetation life forms was examined.
Wildlife Habitat Assessment in an Unmanaged Urban Bottomland Hardwood Forest
The Fourche Creek Bottoms is an approximately 2,000 acre tract of unmanaged bottomland hardwood forest adjacent to the city of Little Rock, Arkansas. In 2005, the City of Little Rock partnered with The National Audubon Society to promote diversity and restore the unique natural features of the Fourche Creek Bottoms. Part of this plan was to enhance habitat for neotropical migrating bird species. We collaborated with Audubon to conduct a forest inventory and develop management guidelines to meet the objectives of the Fourche Creek Bottoms. The inventory was completed during the summer of 2014, sampling a variety of habitat attributes, including canopy cover, snag density, and tree species composition. The final report is being used by Audubon and the City of Little Rock to implement habitat restoration treatments, and educational and recreation programs in the Fourche Creek Bottoms. The project was funded by the Audubon Society.
