Source: FOREST SERVICE submitted to
SCOTCH BROOM ALTERS DOUGLAS-FIR COMMUNITY STRUCTURE AND SOIL ECOLOGY: PREVENTION AND MITIGATION THROUGH ALTERNATIVE MANAGEMENT PRACTICES
Sponsoring Institution
National Institute of Food and Agriculture
Project Status
TERMINATED
Funding Source
AFRI COMPETITIVE GRANT
Reporting Frequency
Annual
Accession No.
1000590
Grant No.
2013-67013-21340
Project No.
NC.W-2013-02329
Proposal No.
2013-02329
Multistate No.
(N/A)
Program Code
A1131
Project Start Date
Sep 1, 2013
Project End Date
Aug 31, 2018
Grant Year
2013
Project Director
Harrington, T. B.
Recipient Organization
FOREST SERVICE
201 14TH ST SW YATES BLDG
WASHINGTON,DC 20002-6405
Performing Department
USDA
Non Technical Summary
Scotch broom (Cytisus scoparius) is a non-native, invasive plant species of major concern in Douglas-fir forests of the Pacific Northwest capable of causing long-term changes in soil ecological processes, resource supply, and forest community structure. Relatively little is known about links between management practices and invasion, effects on soil properties, and whether these impacts can be reversed. Specific objectives are to: (1) identify relative contributions of soil disturbance, altered soil and light environments, and seed bank dynamics to broom invasion, (2) determine effects of broom on soil chemical and physical properties, resource supply, and plant community structure, and (3) assess potential recovery of soil properties and native plant communities after broom removal. A combination of manipulative and observational studies will be conducted at three existing research sites that differ in soil texture and nutrient pools. For Objective (1), we will compare five-year development of Scotch broom and planted Douglas-fir among combinations of logging debris, soil disturbance, and herbicide treatments. For Objective (2), soil properties and plant community characteristics will be compared between broom-invaded and non-invaded areas at two sites. For Objective (3), areas will be established at one site in which broom was removed 4 and 10 years previously to evaluate potential soil P depletion, altered soil physical properties, and allelopathic effects. The proposed research assesses a broad variety of ecological processes related to integrated pest management of Scotch broom and then uses links between forestry practices and broom invasion to design strategies to prevent future invasions, control existing infestations, and mitigate the impacts of broom.
Animal Health Component
0%
Research Effort Categories
Basic
80%
Applied
20%
Developmental
0%
Classification

Knowledge Area (KA)Subject of Investigation (SOI)Field of Science (FOS)Percent
2130199107040%
1020110105040%
1230199106020%
Knowledge Area
213 - Weeds Affecting Plants; 123 - Management and Sustainability of Forest Resources; 102 - Soil, Plant, Water, Nutrient Relationships;

Subject Of Investigation
0199 - Soil and land, general; 0110 - Soil;

Field Of Science
1050 - Developmental biology; 1060 - Biology (whole systems); 1070 - Ecology;
Goals / Objectives
Quantify the relative contributions of soil physical disturbance, logging debris abundance, vegetation and seed bank characteristics, and aspects of the soil and light environment to Scotch broom establishment and assess the utility of alternative management strategies (i.e., combined logging debris and herbicide treatments) to limit broom establishment and improve performance of planted Douglas-fir. Determine the effects of Scotch broom invasion on soil chemical and physical properties, resource supply for plant growth (i.e., nutrient supply, water availability), and plant community structure and composition. Assess the recovery of soil properties and native plant communities 4 and 10 years after removal of Scotch broom in Douglas-fir forests.
Project Methods
Methods for Objective 1: Soil and light conditions contributing to broom establishment We willexpand on the recently-installedproject at Dry Bed Creek, as well asconduct laboratory studies, to quantify the effects of different levels of soil disturbance and logging debris after forest harvesting on establishment of Scotch broom. At Dry Bed Creek, the researchincludes a five-year evaluation (2014-2018) of the efficacy of Scotch broom control and associated regeneration performance of planted Douglas-fir following combinations of logging debrisand herbicide treatments.Three components of broom establishment will be monitored annually: seedling density,survival, andgrowth. Soil temperature and water content will be measured continuously. To determine fifth-year treatment effects on broom seed-bank demographics,soil coreswill be collected from each treatment plot in fall 2017, composited and mixed, and kept moist for 90 days in a controlled environment growth chamber. Germinating broom seedlings will be counted at 2-5 day intervals. In spring 2014, an experimentally controlled study will be conducted under full sun conditions to evaluate the effects of different depths of simulatedlogging debris on broom establishment and on soil surface and light environment factors. PVC frames (60 cm x 60 cm) will be built to suspend different depths of Douglas-fir green shootsapproximately 10 cm above plastic boxes filled with soil from two existing study sites near Matlock WA and Molalla OR. Each of five masses of simulated logging debriswill be replicated three times. Beginning at study initiationand continuing for 90 days, measurements of light intensityand spectrawill be taken each month during clear sky conditions. Red/far-red (R/FR) ratios will be calculated for light conditions under each frame. In early 2014, a gradient in R/FR will be constructed within a growth chamber.In two separate studies during2014, fixed populations of broom seed will be germinated at different R/FR in thegrowth chamber study. Treatment effects in the field study will be assessed with mixed effects, repeated measures analysis of variance (ANOVA) and regression, with pre-treatment broom plant density and seed bank density included as covariates when appropriate. Treatment effects in the debris-mass laboratory study will be evaluated with analysis of variance to quantify potential linear or quadratic effects of logging debris mass onsoil temperature, light intensity, and R/FR, as well as on the components of broom establishment. In the growth chamberstudy, the relationship of broom germination to R/FR will be evaluated with regression. Methods for Objective 2: Scotch broom effects on soil properties and plant community characteristics We will identify six paired invaded and non-invaded areas at each of the Matlock and Molalla sites. Withineach area in June 2014, fivesoil samples will be collected by0-15 cm and 15-30 cm depths and composited in the field. Total C and N,exchangeable Ca, Mg, and K,and extractable P will be estimated. Available inorganic N pools and potential N mineralization will be assessed bimonthly throughout the 2014 growing season.Plant community composition and structure in each of broom invaded and non-invaded areas will be assessed within a series of nested square plots (0.01, 0.1, 1, 10, and 100 m2) sharing a common diagonaltoquantify changes in species density with changing sampling area, as well as changes in species composition. Species will be recorded incrementally for each of the nested plots, and cover will bevisually estimated by species within the10-m2 plot.To study Scotch broom effects on soil resource availability and plant community development, a 2x2 factorial treatment design will be installed at Dry Bed Creek in spring 2014 and monitored for 4 years.Factor 1 will be Scotch broom presence or absence, and Factor 2 will be presence or absence of other competing vegetation. Ten replications of each treatment will be randomly applied to 2-m x 2-m plots. One-year-old, container-grown seedlings of broomwill be transplanted to plots assigned to the broom-present treatment, and non-soil-active herbicides (i.e., glyphosate and triclopyr) will be used to remove all vegetation within competing-vegetation-absent treatments. Sensors will be installed within sixreplications of each treatmentto quantify soil temperature and water content, and tension lysimeters will be installed to a depth of 20 cm to characterize soil water chemistry during the growing season as an index of nutrient availability. Plant community structure and composition will be measured using 2-m2 plots centered within each treatment plot.Differences in soil properties between broom invaded and non-invaded soils will be analyzed withANOVA by site, and regression will be used to assess if the magnitude of effect is dependent on aboveground biomass and density of Scotch broom. Mixed effects models with repeated measures ANOVA will be used to assess influence of broom and other vegetation on soil water and nutrient variability in the planted broom study. Methods for Objective 3: Soil and plant community recovery following Scotch broom removal We will use a dual approach composed of direct measurement of soil properties and vegetation at 0-4 and 10 years after broom removal treatments, and indirect assessments of lasting broom effects on native plant biomass with a bioassay experiment using soil with the same post-removal durations. We will remove broom from six 10- x 10-m areasat Matlock and Molalla in the fall of 2013 withtriclopyr ester herbicidefollowed by additional herbicide treatments in subsequent years as needed to ensure complete removal for a 4-year study duration.We will also utilize plots in the existing Matlock study where Scotch broom was removed from known areas in 2007 to assess 10-year effects of broom removal. Soil samples will be collected prior to broom removal and two (2015) and four (2017) years after removal to assess recovery over time. Soils from non-invaded areas will be collected at the same time periods to serve as controls. For analysis of effects 10 years after broom removal (2007) at the Matlock site, we will use archived soil samples which were collected by plot in 2008, in combination with samples collected from those same locations in 2017.For each sample period and location, soil will be collected by0-15 and 15-30 cm depthsat five locations in each plot and composited toestimate total C, N, and P.We will establish a two-way factorial experiment as a pot study within agreenhouse to determine the influence of allelopathic compounds, P depletion, or other nutrient limitation on plant biomass. The experimental design will be as follows: Factor 1 = soil with four durations ofbroominfluence (non-invaded, invaded and never removed for 10 years, invaded and removed4 years previously, and invaded and removed10 years previously),and Factor 2 = three fertilizer treatments (not amended,amended with P fertilizer, and amended with acomplete fertilizer treatment).The 12 treatments will be replicated five times in pot studies for each of three native plant species: Douglas-fir, yarrow, and Roemer's fescue. A fixed number of seeds for eachspecies will be sown per pot and seedling emergence will be measured periodically over a 90-day period. Pots will be randomly placed within a greenhouse and atthe end of the study, seedling survival and biomass (above and below ground) will be measured for each species.We will use pre-removal parameter estimates of soil properties to calculate the change over time relative to control areas, and then use t-tests to determine if changes are significantly different from zero. Treatment effects in the bioassay study will be assessed with ANOVA.

Progress 09/01/13 to 08/31/18

Outputs
Target Audience:For the duration of the project, our target audience has included plant ecologists, invasive plant scientists, forest vegetation managers, silviculturists, regeneration foresters, and invasive plant specialists. Technology transfer has included: (1) presentations at scientific conferences, professional forestry conventions, and forest management field tours, and (2) publications in peer-reviewed scientific journals, trade magazines, and professional society periodicals. During FY18, we successfully communicated the results of our research to: (1) the scientific community and (2) regional vegetation managers. Peer-reviewed journal publications (i.e., Harrington et al. 2018, Peter and Harrington 2018) and formal presentations (i.e., annual meeting of the WSWS) were used to communicate results to the first group, and formal presentations were used to communicate results to the second group (e.g., first annual meeting of the Pacific Northwest Vegetation Management Association). Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? The following FY18 activities are associated with the professional development of Ph.D. student Dave Carter, who completedand successfully defendedhis Ph.D. dissertation in June 2018: 1. Dave submitted a scientific journal manuscript on the Scotch broom addition study for publication in the scientific journal, Biological Invasions. 2. Dave summarized results from the Scotch broom physiology study at the annual convention of the Society of American Foresters (Albuquerque NM, November 2017). 3. Dave interviewed for five academic positions, and he was offered and accepted a tenure-track faculty position in silviculture at Virginia Tech. The research team views this end result as an absolute success: a new scientist was trained via resources provided by the USDA NIFA Grant Program and an intense spirit of collaboration among all team members. Forestry Technician James Dollins helped Tim Harrington to design and set-up the light systems for the red: far-red light study. James also set-up the irrigation system for the Scotch broom soil bioassay study. James attended the annual meeting of the Western Society of Weed Science (Anaheim CA, March 2018). How have the results been disseminated to communities of interest? The results of the research were presented at several scientific conferences in FY18: 1. At the first annual meeting of Pacific Northwest Vegetation Management Conference (Wilsonville OR, October 2017), Tim Harrington gave an invited presentation on vegetation responses to logging debris and herbicide treatments. 2. At the annual convention of the Society of American Foresters (Albuquerque NM, November 2017), Ph.D. student Dave Carter gave a presentation on comparative physiology and growth of Scotch broom and Douglas-fir in response to resource availability. 3. At the annual meeting of the Western Society of Weed Science (Anaheim CA, March 2018), Tim Harrington summarized Scotch broom germination and growth responses to red versus far-red light. Two journal articles were published in Forest Ecology and Management in FY18 that described five-year plant community, planted Douglas-fir, and microclimate responses to logging debris and herbicide treatments on droughty forest site invaded by Scotch broom. What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? Goal 1 (Scotch broom establishment): We initiated and completed the five-year Dry Bed Creek Study, which compared combinations of logging debris and herbicide treatments for their ability to control Scotch broom andothercompeting vegetation and improve performance of planted Douglas-fir. We conducted growth chamber studies to compare effects of red and far-red light on seed germination and seedling growth of Scotch broom. We also determined the effect of light intensity on seed germination. We initiated the three-year Scotch broom risk study to assess how site differences in soil texture and annual precipitation influence Scotch broom invasion and its competitive effects on Douglas-fir. The study will be completed in December 2018. 1. Two peer-reviewed scientific journal articles were published in FY18 from the Dry Bed Creek study (compares logging debris and herbicide treatment combinations on Scotch broom abundance and Douglas-fir performance). 2. The following activities in FY18 were associated with the Scotch broom red/far red (R:FR) study (compares seed germination and seedling growth under two levels of R:FR): - Two germination studies were conducted in growth chambers at the Olympia Forestry Sciences Laboratory outfitted with and without supplemental far-red light (i.e., approximately 730 nm wavelength). Grand Rapids lettuce seed was used as a standard to confirm inhibition of germination via far-red light. Unfortunately, presence of white, red, and blue light in both chambers was sufficient to result in similar lettuce and Scotch broom germination responses regardless of the presence of far-red light in one of the chambers. - A third experiment was conducted with each chamber being assigned to have either red light or far-red light. A strong inhibitory response to lettuce seed germination was found in the far-red light chamber, but Scotch broom seed germination did not differ between red and far-red light chambers. Forty-day growth, however, varied strongly between the two chambers, resulting in a strong reduction in biomass, especially for roots, in the presence of far-red light. - A final growth chamber experiment is currently underway to quantify the effects of light intensity on seed germination. 3. The following activities in FY18 were associated with the Scotch broom risk study (part of Dave Carter's Ph.D. research; compares growth rates and soil water use of Scotch broom and Douglas-fir on 10 sites of differing soil texture in WA and OR): - Stem diameter, total height, and crown width of the sample Scotch broom and Douglas-fir seedlings were re-measured during winter 2017-2018; densities of Scotch broom and Douglas-fir seedlings also were re-measured. - In spring 2018, competing vegetation was controlled via herbicides around three Scotch broom and three Douglas-fir at each site to enable estimation of soil water use by each species. - Soil water, soil temperature, and weather station data were downloaded from each site. Soil water sensors were replaced as needed due to animal damage. - A journal manuscript has been drafted as part of Dave Carter's Ph.D. dissertation. Goal 2 (Scotch broom resource use and soil effects): We initiated and completed the four-year Scotch broom addition study which compared effects of presence and absence of planted Scotch broom and presence and absence of background competing vegetation on microclimate, plant community characteristics, and Scotch broom growth. We initiated and completed the four-year Scotch broom removal study which compared different durations of Scotch broom retention and removal on microclimate and plant community characteristics. Graduate student Dave Carter initiated and completed two-year studies on: (1) comparative physiology of Scotch broom and Douglas-fir as influenced by irrigation and fertilization, and (2) Scotch broom nitrogen fixation as affected by irrigation and phosphorus fertilization. 1. Ajournal manuscript was submitted for publication in FY18 for the Scotch broom addition study (compares microclimate and vegetation responses to presence versus absence of planted broom seedlings with and without control of associated vegetation). 2. The following activities in FY18 were associated with the Scotch broom physiology study (part of Dave Carter's Ph.D. research; compares Scotch broom and Douglas-fir physiology and growth at two levels each of soil water and soil nutrients): - A total of 23 Scotch broom and 22 Douglas-fir seedlings was harvested to determine aboveground biomass. Biomass of each plant was dried to a constantmass at 65°C and weighed. - A journal manuscript has been drafted as part of Dave Carter's Ph.D. dissertation. 3. The following activities in FY18 were associated with the Scotch broom nitrogen fixation study (part of Dave Carter's Ph.D. research; compares growth, total accumulated nitrogen from symbiotic fixation, and physiology of container-grown Scotch broom at two levels of soil water with and without phosphorus fertilization): - The 20 Scotch broom plants in the study were removed from their containers, each plant was separated into root and shoot components, and the roots were washed to remove as much soil as possible. Each biomass component was dried to a constant mass at 65°C and weighed. Ground subsamples of the biomass components were analyzed for total C, N, S, and P concentrations. Soil samples were collected for 0-25 and 25-50 cm depth increments and analyzed for total C, total N, and available P. - Ajournal manuscript has been drafted as part of Dave Carter's Ph.D. dissertation. Goal 3 (Recovery of soils and plant communities impacted by Scotch broom): Soil samples were collected from the Scotch broom removal study at 0, 2, and 4 years to determine how presence versus absence of the species influenced availability of soil nitrogen, phosphorus, and other nutrients. The following activities in FY18 were associated with the Scotch broom removal study (compares microclimate and vegetation responses to removal of 10-year-old Scotch broom in Douglas-fir plantations at Matlock WA and Molalla OR): 1. Co-Investigator Tony D'Amato is preparing a scientific journal manuscript that will summarize plant community and microclimate responses to removal of Scotch broom. 2. Fourth-year soil samples were collected in spring 2018 at each of the Matlock and Molalla study sites. The samples from 0, 2, and 4 years after treatment were analyzed to determine how soil chemistry has changed since removal of Scotch broom. Co-Investigator Robert Slesak is conducting the data analysis and will prepare a manuscript that summarizes the soil responses to removal of Scotch broom. 3. Soil samples were collected from each plot of the Scotch broom removal study at Matlock in April 2018 to provide sufficient growing medium for the Scotch broom soil bioassay study. This 120-day greenhouse study, underway at the Olympia Forestry Sciences Laboratory, was designed to identify how Scotch broom influences the productive capacity of soils and whether removal of the species initiates a recovery process that is beneficial to native plant growth. Three native plant species (Douglas-fir, yarrow, and Roemer's fescue) were germinated in flats and transplanted into 2.3 L pots containing the specific soil treatments. Treatments include a factorial arrangement of four soil treatments (Scotch broom kept out since 2003, Scotch broom removed in 2007, Scotch broom removed in 2013, and Scotch broom never removed since 2003), three fertilizer treatments (non-fertilized, one-time application of triple superphosphate, and bi-weekly application of a complete liquid fertilizer), and three species. The experimental design is a randomized complete block with five replications of 36 treatments. The soil bioassay study will be completed in late August 2018.

Publications

  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Peter, D.H. and T.B. Harrington. 2018. Effects of forest harvesting, logging debris, and herbicides on the composition, diversity and assembly of a western Washington, USA plant community. For. Ecol. Manage. 417: 18-30.
  • Type: Journal Articles Status: Published Year Published: 2018 Citation: Harrington, T.B., R.A. Slesak, and D.H. Peter. 2018. Logging debris and herbicide treatments improve growing conditions for planted Douglas-fir on a droughty forest site invaded by Scotch broom. For. Ecol. Manage. 417: 31-39.
  • Type: Journal Articles Status: Other Year Published: 2018 Citation: Carter, D.R., R.A. Slesak, T.B. Harrington, D.H. Peter, and A.W. DAmato. 2018. Scotch broom (Cytisus scoparius) modifies growing conditions to promote a nonnative community structure. Biological Invasions (in revision).
  • Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: Carter, D.R., R.A. Slesak, T.B. Harrington, and A. DAmato. 2017. Physiology and growth of Scotch broom and Douglas-fir in response to resource availability. Annual convention of the Society of American Foresters. November 15-19, 2017. Albuquerque, NM.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2017 Citation: Harrington, T.B., D.H. Peter, and R.A. Slesak. 2017. Comparative responses of planted Douglas-fir and associated vegetation to logging debris retention and site preparation herbicide treatments. Pacific Northwest Forest Vegetation Management Conference, Wilsonville, OR. November 29-30, 2017.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2018 Citation: Harrington, T.B. 2018. Scotch broom germination and growth responses to red and far-red light: implications to logging debris effects after forest harvesting. Annual meeting of the Western Society of Weed Science. March 12-15, 2018. Anaheim, CA.
  • Type: Conference Papers and Presentations Status: Other Year Published: 2018 Citation: Harrington, T.B. 2018. Forest regeneration and density management issues associated with droughty sites. Annual meeting of the Pacific Northwest Reforestation Council. Vancouver WA. September 27, 2018.
  • Type: Theses/Dissertations Status: Published Year Published: 2018 Citation: Carter, D.R. 2018. Identifying physiological and growth-allocation strategies enabling Scotch broom (Cytisus scoparius (L.) Link) dominance in recently clearcut Douglas-fir forests of the western Pacific Northwest. Ph.D. dissertation, University of Minnesota, Minneapolis.
  • Type: Journal Articles Status: Other Year Published: 2018 Citation: Carter, D.R., R.A. Slesak, T.B. Harrington, and A.W. DAmato. Effects of soil resource limitation on comparative physiology and growth of Scotch broom (Cytisus scoparius) and Douglas-fir (Pseudotsuga menziesii) seedlings. (Target journal to be identified).
  • Type: Journal Articles Status: Other Year Published: 2018 Citation: Carter, D.R., R.A. Slesak, T.B. Harrington, and A.W. DAmato. Effects of irrigation and phosphorus fertilization on soil water use, nitrogen fixation, physiology, and growth of Scotch broom (Cytisus scoparius). (Target journal to be identified).
  • Type: Journal Articles Status: Other Year Published: 2018 Citation: Carter, D.R., R.A. Slesak, T.B. Harrington, and A.W. DAmato. 2018. Soil texture and other site-level factors differentially affect growth of Scotch broom (Cytisus scoparius) and Douglas-fir (Pseudotsuga menziesii) seedlings in the western Pacific Northwest. (Target journal to be identified).
  • Type: Other Status: Other Year Published: 2017 Citation: Slesak, R.A., M.B. Russell, D.R. Carter, and T.B. Harrington. 2017. Identifying soil-site conditions favorable to Scotch broom invasion for adaptive management In Douglas-fir plantation forestry. Proposal submitted to 2017 NIFA CARE Program (not selected for funding).
  • Type: Journal Articles Status: Other Year Published: 2018 Citation: Slesak, R.A., T.B. Harrington, and A.W. DAmato. 2018. Influence of Scotch broom removal on soil chemistry at two Pacific Northwestern forest sites differing in soil texture. (Target journal to be identified).
  • Type: Journal Articles Status: Other Year Published: 2018 Citation: DAmato, A.W., T.B. Harrington, D.H. Peter, and R.A. Slesak. 2018. Influence of Scotch broom removal on microclimate and plant community characteristics at two Pacific Northwestern forest sites. (Target journal to be identified).


Progress 09/01/16 to 08/31/17

Outputs
Target Audience:During FY17, we successfully communicated the results of our research to: (1) weed scientists, primarily those who work on problems related to managed forests and natural areas, (2) weed managers, including those from city, county, and state organizations assigned to prevent, control, or mitigate noxious or otherwise invasive plants, and (3) professional natural resource managers, including those of private industry (e.g., Green Diamond Resource Company, Port Blakely Tree Farms) and public forestry agencies (e.g., Joint Base Lewis-McChord, Washington State Department of Natural Resources) in the Pacific Northwest. Technical publications (i.e., Duncan and Harrington 2016a,b) and formal presentations (i.e., at annual meetings of the SAF, WSWS, and the regional Scotch Broom Ecology and Management Symposium) were used to communicate results to the first two groups, whereas informal presentations and field tours (i.e., CAFS tour) were used to communicate results to the third group. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? The following FY17 activities are associated with the professional development of Ph.D. student Dave Carter, who is currently about midway in his dissertation research. Dave expects to complete his graduate program in June 2018. -Dave is currently preparing a scientific journal manuscript for the Scotch broom addition study. -Dave summarized results from the Scotch broom addition study and initial findings from the Scotch broom physiology study in two presentations at the annual convention of the Society of American Foresters (Madison WI, November 2016). -Project investigators worked with Dave to submit a proposal to the FY17 NIFA Critical Agricultural Research and Extension (CARE) grant program. If funded, the proposal would support post-doctoral work for Dave, additional technology transfer of the Scotch broom research findings (including two workshops and a five-part webinar series), and the second Scotch Broom Ecology and Management Symposium in 2019. -Dave presented a summary of his doctoral research at the annual meeting of the Ecological Society of America (Portland OR, August 2017). Forestry Technician James Dollins assisted Tim Harrington at the annual meeting of the Western Society of Weed Science (Coeur d' Alene ID, March 2017). James helped Tim to moderate the technical session on Weeds of Range and Natural Areas, and he helped Tim to lead a discussion on application of weed competition models using data from the current NIFA grant. How have the results been disseminated to communities of interest? The results of the research were presented at several scientific conferences: -At the annual convention of the Society of American Foresters (Madison WI, November 2016), Ph.D. student Dave Carter summarized findings from the Scotch broom addition study, which was completed in December 2016. Dave Carter also presented a poster on current findings from the Scotch broom physiology study. -At the annual meeting of the Western Society of Weed Science (Coeur d' Alene ID, March 2017): Tim Harrington summarized Douglas-fir responses to logging debris and herbicide treatments from the Dry Bed Creek study, which was completed in December 2016. Dave Peter summarized plant community responses to logging debris and herbicide treatments from the Dry Bed Creek study. As Chair of the section on Weeds of Range and Natural Areas, Tim Harrington lead a discussion on application of weed competition models. He used results from the Dry Bed Creek study as an example. -At the first Scotch Broom Ecology and Management Symposium (Snoqualmie WA, May 2017): Tim Harrington gave a presentation on suppressing Scotch broom establishment by manipulating microclimate with logging debris and herbicides. Tim Harrington also was a member of the Symposium's steering committee, helping with planning and execution of the meeting. Dave Carter presented a poster on the Scotch broom physiology and nitrogen fixation studies. Tim Harrington worked with Celestine Duncan to produce two technical articles on Scotch broom control with herbicide and logging debris treatments. The articles appeared in Dow AgroScience's trade journal, TechLine Invasive Plant News, during fall 2016. Tim Harrington was co-leader of a field tour for the annual meeting of the Center for Advanced Forestry Systems (CAFS) (Portland OR, May 2017). During the tour, located in the Winlock WA area, Tim discussed findings from the NIFA-supported research on Scotch broom. Attendees included approximately 25 people from forest industry and land grant universities. What do you plan to do during the next reporting period to accomplish the goals?Goal 1 (Scotch broom establishment): Tim Harrington, Dave Peter, and Rob Slesak will submit two manuscripts from the Dry Bed Creek study for publication in the scientific journal, Forest Ecology and Management (listed above). Tim Harrington will present results from the Scotch broom red: far red study at the annual meeting of the Western Society of Weed Science (Garden Grove CA, March 2018). Tim Harrington, Dave Carter, James Dollins, and Dave Peter will measure Scotch broom and Douglas-fir growth at the 10 sites of the Scotch broom risk study to assess how available soil water influences broom establishment and growth for a wide range of soil textures. Goal 2 (Scotch broom resource use and soil effects): Dave Carter will complete his dissertation which will include chapters on the Scotch broom physiology study, nitrogen fixation study, and risk study. His dissertation will use a journal manuscript format so that papers can be prepared for direct submission to scientific journals. Dave Carter will submit for publication the following manuscript on the Scotch broom addition study: Carter, D.R., R.A. Slesak, T.B. Harrington, A.W. D'Amato, and D.H. Peter. Effects of invasive Scotch broom on soil water, soil water chemistry, and abundance of associated plant species. To be submitted to Plant and Soil. Rob Slesak will analyze soil chemistry data from the Scotch broom addition study and Dry Bed Creek study and prepare associated manuscripts. Goal 3 (Recovery of soils and plant communities impacted by Scotch broom): Tony D'Amato will develop and submit for publication a manuscript on plant community and microclimate responses to Scotch broom removal in Douglas-fir plantations. Fourth-year soil samples from the Scotch broom removal study will be collected in the fall of 2018. Rob Slesak will analyze all samples from 0, 2, and 4 years after treatment to determine how soil chemistry has changed since removal of Scotch broom. Additional soil samples will be collected from each treatment of the Scotch broom removal study. A 90-day soil bioassay study will be conducted in the greenhouse at the Olympia Forestry Sciences Laboratory in spring 2018 to determine how study treatments (i.e., Scotch broom retained, removed, or never present), with and without nutrient amendments, affect growth and development of several native plant species.

Impacts
What was accomplished under these goals? Goal 1 (Scotch broom establishment): The following activities in FY17 were associated with the Dry Bed Creek study (compares logging debris and herbicide treatment combinations on Scotch broom abundance and Douglas-fir performance). Note that the end of calendar year 2016 was the final year of the study. -The following data were collected: Fourth-year survival and growth of planted Douglas-fir. Final measurements of soil water and soil temperature. Final soil samples collected and analyzed for chemical properties. -The following manuscripts have been drafted and are almost ready for submission to a scientific journal: Peter, D.H. and T.B. Harrington. Effects of clearcutting, debris treatment and vegetation control by herbicide on the composition, diversity and assembly of a western Washington, USA plant community. To be submitted to For. Ecol. Manage. Harrington, T.B., D.H. Peter, and R.A. Slesak. Effects of logging debris and herbicide treatments on microclimate and performance of planted Douglas-fir five years after forest harvesting on a droughty glacial outwash soil. To be submitted to For. Ecol. Manage. The following activities in FY17 were associated with the Scotch broom red/far red ratio (R:FR) study (compares seed germination and seedling growth under two levels of R:FR): -Two growth chambers have been configured at the Olympia Forestry Sciences Laboratory with LED light banks to provide typical light spectra for seed germination (i.e., red, blue, and white light); however, one chamber has additional LED's for far-red light (i.e., approximately 730 nm wavelength). -Supplemental LED bulbs were installed to further increase differences in R:FR between the two chambers. Measurements of light spectra were used to confirm differences in R:FR between the two chambers. -Plant materials for the study consisted of seeds collected and kept separate for 14 individual Scotch broom plants to account for potential genetic variation in seed and seedling responses to variation in R:FR. -Scotch broom germination responses were tested in two 20-day trials. Scotch broom growth responses were tested with a single 40-day trial. The following activities in FY17 were associated with the Scotch broom risk study (part of Dave Carter's Ph.D. research; compares growth rates and soil water use of Scotch broom and Douglas-fir on 10 sites of differing soil texture in WA and OR): -Stem diameter, total height, and crown width of the sample Scotch broom and Douglas-fir seedlings were re-measured during winter 2016-2017; densities of Scotch broom and Douglas-fir seedlings also were re-measured. -In spring 2017, competing vegetation was controlled via herbicides around three Scotch broom and three Douglas-fir at each site to enable estimation of soil water use by each species. -Soil water, soil temperature, and weather station data were downloaded from each site. Soil water sensors were replaced as needed due to animal damage at two of the study sites. -In summer 2017, cover of vegetation by species was estimated visually within a 2- x 2-m plot centered on each sample Scotch broom and Douglas-fir seedling. -Soil nutrient and textural analyses were completed on samples collected from each site; soil bulk density was estimated for each site at 0-15 and 15-30 cm depths. Goal 2 (Scotch broom resource use and soil effects): The following activities in FY17 were associated with the Scotch broom addition study (compares microclimate and vegetation responses to presence vs. absence of planted broom seedlings with and without control of associated vegetation; located adjacent to the Dry Bed Creek Study near Matlock WA). Note that the end of calendar year 2016 was also the final year for this study. -Final soil water and soil temperature data were collected in fall 2016. -Final growth measurements were taken on the planted broom seedlings. -Final soil samples were collected and analyzed along with pretreatment samples for chemical properties (e.g., total C, total N, and extractable macronutrients). -Ph.D. student Dave Carter is developing a journal manuscript that describes microclimate and vegetation responses to addition of Scotch broom with and without control of associated vegetation. The following activities in FY17 were associated with the Scotch broom removal study (compares microclimate and vegetation responses to removal of 10-year-old Scotch broom in Douglas-fir plantations at Matlock WA and Molalla OR). -Soil water, soil temperature, and weather station data were downloaded from each site. Soil water sensors were replaced as needed due to animal damage. -Vegetation cover by species was estimated visually in June 2017. -Light intensity at 50-cm height (via the Decagon AccuPAR sensor) was remeasured in July 2017. -New seedlings of Scotch broom were removed from study plots. The following activities in FY17 were associated with the Scotch broom physiology study (part of Dave Carter's Ph.D. research; compares Scotch broom and Douglas-fir physiology and growth at two levels each of soil water and soil nutrients). -Weed control was maintained throughout the study in 2017 with periodic herbicide applications. -Fertilizer treatments were maintained during the 2017 growing season (weekly applications of liquid fertilizer containing macro- and micronutrients). Irrigation treatments (from the Webster State Nursery system) were maintained during the 2017 growing season. Several broom seedlings damaged or killed by rodents were replanted. -Photosynthesis, transpiration, and water use efficiency were measured on a subsample of the plants at biweekly intervals during May-June and August-September 2017 using a borrowed Li-Cor 6400 infrared gas analyzer. Plant water potential measurements (pre-dawn and midday, via a pressure chamber) were taken during mid-August 2017. -Seed pod number and biomass were measured for each Scotch broom in late June 2017. -Plant growth was measured biweekly throughout the growing season in 2017. -Soil water data were downloaded periodically during 2017. -Light interception by individual Scotch broom and Douglas-fir was measured with a Decagon Accupar sensor in July 2017. These data are being used to estimate light attenuation under each speciesas well as individual plant leaf area index. The following activities in FY17 were associated with the Scotch broom nitrogen fixation study (part of Dave Carter's Ph.D. research; compares growth, total accumulated nitrogen from symbiotic fixation, and physiology of container-grown Scotch broom at two levels of soil water with and without fertilization with phosphorus): -Soil water chemistry was sampled three times during winter 2016-2017 to quantify this portion of the nitrogen pool. Samples were analyzed at the University of Washington soils lab. -Plant growth was measured biweekly throughout summer 2017. -Soil water data were downloaded periodically during 2017. -Photosynthesis, transpiration, and water use efficiency were measured on each Scotch broom at biweekly intervals during May-June and August-September 2017. -During late September 2017, each Scotch broom plant will be harvested for above- and below-ground biomass and total nitrogen per plant. The soil in each pot also will be analyzed for nitrogen concentration to complete the estimates of total accumulated nitrogen. Goal 3 (Recovery of soils and plant communities impacted by Scotch broom): Co-Investigator Tony D'Amato began analyzing the vegetation data from the Scotch broom removal study in preparation for a scientific journal manuscript that will summarize plant community and microclimate responses to removal of Scotch broom.

Publications

  • Type: Conference Papers and Presentations Status: Other Year Published: 2017 Citation: Carter, D.R., R.A. Slesak, T.B. Harrington, A.W. DAmato, and D.H. Peter. 2017. Effects of invasive Scotch broom on soil water, soil water chemistry, and abundance of associated plant species. Annual meeting of the Ecological Society of America. Portland OR. August 6-11, 2017. Oral presentation.
  • Type: Conference Papers and Presentations Status: Other Year Published: 2017 Citation: Harrington, T.B., D.H. Peter, and R.A. Slesak. 2017. Four-year survival and growth responses of planted Douglas-fir to logging debris and herbicide combinations designed to control Scotch broom and other competitors. Annual meeting of the Western Society of Weed Science. Coeur d Alene ID. March 13-16, 2017. Oral presentation.
  • Type: Conference Papers and Presentations Status: Other Year Published: 2017 Citation: Harrington, T.B. 2017. Field tour of Port Blakely company lands near Winlock WA. Discussion of long-term soil productivity research, Scotch broom risk study, and herbicide treatments. Center for Advanced Forestry Systems, 2017 Industrial Advisory Board Annual Meeting. Portland OR. May 2-4, 2017.
  • Type: Conference Papers and Presentations Status: Other Year Published: 2017 Citation: Harrington, T.B. 2017. Suppressing Scotch broom establishment by manipulating microclimate with logging debris and herbicides. Scotch Broom Ecology and Management Symposium. Snoqualmie WA. May 23, 2017. Oral presentation.
  • Type: Conference Papers and Presentations Status: Other Year Published: 2017 Citation: Peter, D.H. and T.B. Harrington. 2017. Differences in plant community assembly of a western Washington forest five years after harvesting with various combinations of logging debris retention and vegetation control. Annual meeting of the Western Society of Weed Science. Coeur d Alene ID. March 13-16, 2017. Oral presentation.
  • Type: Other Status: Published Year Published: 2016 Citation: Duncan, C. and T.B. Harrington. 2016a. Synthetic auxin herbicides control germinating Scotch broom. TechLine Invasive Plant News. Fall 2016: 7.
  • Type: Other Status: Published Year Published: 2016 Citation: Duncan, C. and T.B. Harrington. 2016b. Logging debris and herbicide treatments for controlling Scotch broom. TechLine Invasive Plant News. Fall 2016: 8-9.
  • Type: Conference Papers and Presentations Status: Other Year Published: 2016 Citation: Carter, D.R., R.A. Slesak, T.B. Harrington, and A. DAmato. 2016. Effects of invasive Scotch broom on soil water, soil water chemistry, and vegetation. Annual convention of the Society of American Foresters. Madison WI. November 2-6, 2016. Oral presentation.
  • Type: Conference Papers and Presentations Status: Other Year Published: 2016 Citation: Carter, D.R., R.A. Slesak, T.B. Harrington, and A. DAmato. 2016. Effects of resource limitation on the growth and physiology of Scotch broom and Douglas-fir seedlings. Annual convention of the Society of American Foresters. Madison WI. November 2-6, 2016. Poster presentation.
  • Type: Conference Papers and Presentations Status: Other Year Published: 2016 Citation: Carter, D.R., R.A. Slesak, T.B. Harrington, A.W. DAmato. November 2016. Growth and physiological responses of Scotch broom (Cytisus scoparius) relative to Douglas-fir. Poster presented at the annual PNW Station Management Team/Team Leader meeting. Portland OR. October 25-27, 2017.
  • Type: Conference Papers and Presentations Status: Other Year Published: 2017 Citation: Carter, D.R., R.A. Slesak, T.B. Harrington, and A. DAmato. 2017. Effects of resource limitation on the growth and physiology of Scotch broom and Douglas-fir seedlings. Scotch Broom Ecology and Management Symposium. Snoqualmie WA. May 23, 2017. Poster presentation.


Progress 09/01/15 to 08/31/16

Outputs
Target Audience:During FY16, we successfully communicated the results of our research to: (1) weed scientists, primarily those who work on problems related to managed forests and natural areas, (2) soil scientists interested in long-term soil productivity and potential impacts of non-native invasive plants, and (3) professional natural resource managers, including those of private industry (e.g., Green Diamond Resource Company, Port Blakely Tree Farms) and public forestry agencies (e.g., Joint Base Lewis-McChord, Washington State Department of Natural Resources) in the Pacific Northwest. Publications (i.e., Slesak et al. 2016a,b) and formal presentations (i.e., at annual meetings of the SSSA, WSWS, and SER) were used to communicate results to the first two groups, whereas informal presentations and field tours were used to communicate results to the third group. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided?1. Ph.D. student Dave Carter has developed a dissertation proposal and conducted data analyses that have contributed to his professional development. He will be summarizing results from the Scotch broom addition study and initial findings from the Scotch broom physiology study in two presentations to be given at the annual convention of the Society of American Foresters in Madison WI in November 2016. 2. Ph.D. student Dave Carter wrote and submitted a proposal to Decagon Devices, Inc. (environmental instrument company) to be considered for additional instrumentation to support his research. Unfortunately, the proposal was not recommended for the award. 3. Project investigators worked with Ph.D. student Dave Carter to submit a proposal to the U.S. Forest Service, Special Technology Development Program to provide supplemental funding for the Scotch broom risk study. Unfortunately, the proposal was not funded. How have the results been disseminated to communities of interest?The results of the research were presented at several scientific conferences and in peer reviewed journals as follows: 1. The annual meeting of the Soil Science Society of America (SSSA) (Minneapolis MN, November 2015). -Ph.D. student Dave Carter presented initial findings from the Scotch broom addition study. -Tim Harrington gave an invited presentation on long-term soil productivity (LTSP) research in the Pacific Northwest in which he described Scotch broom and native plant responses to the logging debris and herbicide treatments at the Matlock LTSP and Dry Bed Creek studies. The presentation received the "Best Paper Award" for Division S-7 of the SSSA. 2. The annual meeting of the Western Society of Weed Science (Albuquerque NM, March 2016). Tim Harrington presented second-year findings from the Scotch broom removal studies. 3. A peer-reviewed manuscript (Slesak et al. 2016a) was published in the scientific journal, Plant and Soil, reporting on the effects of Scotch broom on soil chemical properties with focus on soil P fractions. 4. A peer-reviewed manuscript (Slesak et al. 2016b) was published in the scientific journal, Forest Ecology and Management, reporting on 10-year changes in Douglas-fir plantation development resulting from logging debris and herbicide treatments, some of which facilitated invasion of Scotch broom and subsequent changes in plant community structure in the Matlock LTSP study. What do you plan to do during the next reporting period to accomplish the goals? Goal 1 (Scotch broom establishment): 1. Measure 4th-year survival and growth of planted Douglas-fir in the Dry Bed Creek Study. These will be the last measurements prior to data analysis and writing of journal manuscripts on the plant community and planted tree seedling responses to logging debris and herbicide treatments. Preliminary results of the research will be presented by Tim Harrington at the: -triennial meeting of Western Native Plants conference in Vancouver WA in December 2016. -annual meeting of the Western Society of Weed Science in Coeur d'Alene ID in March 2017. 2. Growth chamber study on red/far red light ratios: additional work will occur in FY17 to develop the research methods and conduct the required studies. 3. Measure Scotch broom and Douglas-fir growth in the Scotch broom risk study to assess how available soil water influences broom establishment and growth for a wide range of soil textures. Goal 2 (Scotch broom resource use and soil effects): 1. Collect and analyze post treatment soil samples from the Dry Bed Creek study for comparison with pre-treatment samples to assess change during the 5-year study period. 2. Analyze data from the Scotch broom addition study to assess effects on soil water availability, growth, and soil water chemistry. 3. Continue measurements of soil moisture and temperature in the Scotch broom removal study. 4. Measure physiological and growth responses of Scotch broom and Douglas-fir to irrigation and fertilizer treatments in the Scotch broom physiology study. 5. Measure physiological and growth responses of Scotch broom to irrigation and P amendment treatments in the Scotch broom N-fixation study. Goal 3 (Recovery of soils and plant communities impacted by Scotch broom): 1. Continue measurements of plant species abundance in the Scotch broom removal studies and maintain the specifications of the treatments (e.g., remove new broom seedlings).

Impacts
What was accomplished under these goals? Goal 1 (Scotch broom establishment): 1. The following data were collected in FY16 from the Dry Bed Creek Study near Matlock WA (compares logging debris and herbicide treatment combinations on Scotch broom abundance and Douglas-fir performance): -Third-year survival and growth of planted Douglas-fir. -Density of new Scotch broom seedlings in October 2015. -Bi-weekly measurements of soil water during April-September 2016. -Diurnal measurements of soil temperature (downloaded periodically from i-button sensors). -Vegetation cover by individual plant species in June 2016. 2. Two growth chambers have been configured at the Olympia Forestry Sciences Laboratory to test the effects of varying the ratio of red: far-red light on seed germination of Scotch broom. Pilot studies were conducted in FY15 with seeds from lettuce and Scotch broom, and unfortunately the results were not conclusive. In FY16, Tim Harrington was not able to continue this research because he was assigned to a 6-month detail as an Acting Program Manager for the U.S. Forest Service, Pacific Northwest Research Station. 3. A new "Scotch broom risk study" was established with assistance from Ph.D. student Dave Carter to assess how differences in soil texture and annual precipitation influence Scotch broom invasion and its competitive effects on Douglas-fir: -10 young plantations of Douglas-fir containing Scotch broom were identified in western Washington and Oregon that encompass a range of soil textures and annual precipitation values. -Initial size and other growth parameters of 15 Scotch broom and 15 Douglas-fir seedlings were measured at each site, as well as site descriptors of slope, aspect, and soil series. -Densities of Scotch broom and Douglas-fir seedlings and biomass of the forest floor and down woody debris were estimated. -Soil moisture sensors with hourly logging of data were installed in 3 distinct vegetation conditions to estimate available soil water and how it varies in the presence of Scotch broom, Douglas-fir, and associated vegetation. Soil temperature sensors were installed in the presence and in the absence of associated vegetation at each site. -Cover of vegetation by species was estimated visually in July-August 2016 within a 2x2 m plot centered on each sample Scotch broom and Douglas-fir seedling. Goal 2 (Scotch broom resource use and soil effects): 1. The following data were collected in FY16 from the Scotch broom addition study (located adjacent to the Dry Bed Creek Study near Matlock WA): -Bi-weekly measurements of soil water during April-September. -Diurnal measurements of soil temperature (downloaded periodically from i-button sensors). -Growth measurements of the planted broom seedlings. -Light intensity at 50-cm height (photosynthetically-active radiation, expressed as % of full sun via the Decagon AccuPAR sensor) under each planted Scotch broom in August 2016. -Lysimeter (soil water solution) samples were collected biweekly during November-December 2015 and April-June 2016 until soil drought prevented collection of additional samples. All lysimeter samples were analyzed for concentrations of carbon and macronutrients. 2. The following data were collected from the Scotch broom removal studies (includes two locations with fully replicated studies: Matlock, WA and Molalla, OR): -Diurnal measurements of soil water and soil temperature (downloaded periodically from data loggers and i-button sensors, respectively). -Light intensity at 50-cm height (via the Decagon AccuPAR sensor) in August 2016. 3. A new "Scotch broom physiology study" was initiated with assistance from Ph.D. student Dave Carter to examine the effects of soil water and nutrient availability on Scotch broom and Douglas-fir physiology and growth: -10 replications of a 2x2 factorial design were installed at Webster State Nursery, Olympia WA (immediately adjacent to the Olympia Forestry Sciences Laboratory), and irrigation and fertilization treatments were randomly assigned to planted Douglas-fir and Scotch broom seedlings (includes a total of 51 seedlings per species). -Initial size of each planted seedling was measured and subsequent changes in plant size were recorded at biweekly intervals during summer 2016. -For half of the planted seedlings, soil water sensors were installed to log data at hourly intervals. -Physiological variables of photosynthesis, transpiration, and water use efficiency were collected on half the plants at biweekly intervals from June-August using a borrowed Li-Cor 6400 infrared gas analyzer. Plant water potential measurements (pre-dawn and midday, via a pressure chamber) were taken on a subset of plants during mid-August. -The soil water and nutrient treatments were maintained via the nursery's scheduled irrigation, weekly application of liquid fertilizer, and occasional weed control treatments. 4. A new "Scotch broom nitrogen (N) fixation study" was initiated with assistance from Ph.D. student Dave Carter to examine the effects of soil water and phosphorus (P) availability on N fixation of Scotch broom: -A 2x2 factorial design with irrigation and P amendment treatments was randomly assigned to 5 replications of Scotch broom seedlings planted in 45-gallon pots of sand with little or no N present. -Initial size of each planted seedling was measured and subsequent changes in plant size were recorded at biweekly intervals during summer 2016. -A single application of P fertilizer was applied soon after planting the Scotch broom to simulate non-growth-limiting conditions for this nutrient. -A soil water sensor was installed in each pot to log data at hourly intervals. -Physiological variables of photosynthesis, transpiration, and water use efficiency were collected on each plant at biweekly intervals from June-August using the Li-Cor 6400 infrared gas analyzer. Goal 3 (Recovery of soils and plant communities impacted by Scotch broom): 1. In the Scotch broom removal study, soil samples from 0-15 and 15-30 cm depths were collected in February 2016 to quantify changes in soil chemical properties at 2 years after treatment. Note: 4th-year samples will be collected during winter 2017-18, at which time all samples from 0, 2, and 4 years after treatment will be analyzed for soil chemical properties. -Cover of each plant species was recorded in the Scotch broom addition and Scotch broom removal studies in June 2016. -A manuscript reporting on effects of Scotch broom on soil chemical properties was published in the scientific journal, Plant and Soil, in 2016.

Publications

  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Slesak, R.A., T.B. Harrington, and A.W. DAmato. 2016a. Invasive Scotch broom alters soil chemical properties in Douglas-fir forests of the Pacific Northwest, USA. Plant and Soil 398: 281-289. http://dx.doi.org/10.1007/s11104-015-2662-7
  • Type: Journal Articles Status: Published Year Published: 2016 Citation: Slesak, R.A., T.B. Harrington, D.H. Peter, D.G. DeBruler, S.H. Schoenholtz, and B.D. Strahm. 2016b. Effects of intensive management practices on 10-year Douglas-fir growth, soil nutrient pools, and vegetation communities in the Pacific Northwest, USA. Forest Ecology and Management 365: 22-33. http://dx.doi.org/10.1016/j.foreco.2016.01.019
  • Type: Conference Papers and Presentations Status: Published Year Published: 2015 Citation: Carter, D., R.A. Slesak, T.B. Harrington, and A.W. DAmato. 2015. Effects of invasive Scotch broom on soil water chemistry and the soil microenvironment. Presented at the Soil Science Society of America Annual Meeting, Division S-7, Minneapolis MN, November 15-18, 2015.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2015 Citation: Harrington, T.B., R.A. Slesak, S.M. Holub, S.H. Schoenholtz, and D.H. Peter. 2015. Management implications of organic matter retention after harvesting coast Douglas-fir. Presented at the Soil Science Society of America Annual Meeting, Division S-7, Minneapolis MN, November 15-18, 2015. Note: this presentation received the Best Paper Award for Division S-7.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2016 Citation: Harrington, T.B., R.A. Slesak, D.H. Peter, and A.W. DAmato. 2016. Effects of Scotch broom removal on resource availability and plant community characteristics in Douglas-fir plantations. Annual meeting of the Western Society of Weed Science. Albuquerque NM, March 7-10, 2016.
  • Type: Conference Papers and Presentations Status: Published Year Published: 2016 Citation: Holub, S.M., T.B. Harrington, J.M. Kranabetter, and D.S. Page-Dumroese. 2016. Organic matter removal and soil compaction effects in forests across the Pacific Northwest. Joint annual meeting of the Society for Ecological Restoration (Northwest Region) and Northwest Forest Soils Council. Portland, OR, April 4-8, 2016.


Progress 09/01/14 to 08/31/15

Outputs
Target Audience:During FY15, we successfully communicated the results of our research to: (1) weed scientists, primarily those who work on problems related to managed forests and natural areas, (2) soil scientists interested in long-term soil productivity and potential impacts of non-native invasive plants, and (3) professional natural resource managers, including those of private industry (e.g., Green Diamond Resource Company, Port Blake Tree Farms) and public forestry agencies (e.g., Joint Base Lewis-McChord, Washington Department of Natural Resources) in the Pacific Northwest. Publications and formal presentations were used to communicate results to the first two groups, whereas informal presentations and field tours were used to communicate results to the third group. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? A new Ph.D. student, Dave Carter, was recruited from the University of Maine to work on the project. Davewill present findings on the influence of Scotch broom on soil water, temperature, and chemistry in the 2015 meeting of the Soil Science Society of America. Dave Peter (ecologist, working for Tim Harrington) developed a journal manuscript on three-year vegetation responses in the Dry Bed Creek Study. Tim Harrington will serve as Chair-elect (2016) and Chair (2017) for Project 1 (Weeds of Range and Natural Areas) of the Western Society of Weed Science. Tim Harrington and Rob Slesak were invited to give a presentation at a 2015symposium of the Soil Science Society of America on the role of coarse woody debris in forest ecosystems of the Pacific Northwest. How have the results been disseminated to communities of interest?We have presented results of the research at a variety of forums, including: The Pacific Northwest Invasive Plant Conference (September 2014). Attendees included scientists, university faculty, graduate students, natural resource managers, and invasive plant managers from non-government organizations. The annual meeting of the Soil Science Society of America (November 2014). Attendees included primarily soil scientists and staff from government and university organizations. The annual meeting of the Western Society of Weed Science (March 2015). Attendees included primarily weed scientists and staff from government and university organizations. Published products include two peer-reviewed scientific journal articles and two technical articles. The journal articles appeared/will appear in Weed Technology and Plant and Soil. Technical articles include: (1) a summary of findings from the long-term soil productivity research at Matlock WA and Molalla OR in the Western Forester, a publication of the Oregon and Washington State Societies of American Foresters, and (2) an issue of Science Findings on herbicide treatments for pre-emergent control of Scotch broom and other invasive plant species. Science Findings is, a popularized science update periodical from the USDA Forest Service, Pacific Northwest Research Station. What do you plan to do during the next reporting period to accomplish the goals?Goal 1 (Scotch broom establishment): Measure third-year survival and growth of planted Douglas-fir in the Dry Bed Creek Study. These data will be complete for development of a journal manuscript. Conduct a growth chamber study to determine effects of varying the red/far redratio on Scotch broom seed germination and seedling growth (study was delayed in 2015). Goal 2 (Scotch broom resource use and soil effects): Continue to monitor soil water and soil temperature in the Scotch broom addition study. Measure light intensity under planted broom seedlings,cover by plant species, and soil water chemistry via lysimetry in the Scotch broom addition study. Continue to maintain the specifications of the experimental treatments in the Scotch broom addition and removal studies, such as removal of associated vegetation and removal of new broom seedlings. Work with graduate student, Dave Carter, to study water and nutrient use by Scotch broom in a raised-bed experiment. Otherresearch associated with Dave's graduate program may include field measurements of Scotch broomphysiology, as well as growth chamber studies to quantifyScotch broom's resource requirements. Goal 3 (Recovery of soils and plant communities impacted by Scotch broom): Continue to monitor soil water and soil temperature in the Scotch broom removal studies. Measure light intensity and cover by plant species. Work with graduate student, Dave Carter, to study how differences in soil texture and climate influence invasion and development of Scotch broom and how it competes with native species and affects resultant plant community development and composition.

Impacts
What was accomplished under these goals? Goal 1 (Scotch broom establishment): The following data were collected in FY15 from the Dry Bed Creek Study (compares logging debris and herbicide treatment combinations on Scotch broom abundance and Douglas-fir performance): Second-year survival and growth of planted Douglas-fir. Density of new Scotch broom seedlings in June and July 2015 (final measurement will be October 2015; previously collected data include measurements in June, July, and October of 2012-2014). Soil water was measured bi-weekly during April-September; soil temperature data were downloaded periodically from i-button sensors. A pilot study was conducted in two growth chambers to determine if differences in light quality (i.e., the red/far-red ratio) influence germination of Scotch broom and a cultivar of lettuce. Goal 2 (Scotch broom resource use and soil effects): The following data were collected in FY15 from the Scotch broom addition study (located adjacent to the Dry Bed Creek Study): Soil water was measured bi-weekly during April-September; soil temperature data were downloaded periodically from i-button sensors. Lysimeter samples were collected bi-weekly during November-December 2014 and again during April-June 2015 until soil drought prevented collection of additional samples. All lysimeter samples were analyzed for concentrations of carbon and macronutrients. Growth measurements were taken on the planted broom seedlings at the end of 2014. Light intensity at 50-cm height (photosynthetically-active radiation, expressed as % of full sun via the Decagon AccuPAR sensor) was measured under each planted Scotch broom in July 2015. 2. The following data were collected from the Scotch broom removal studies (two locations: Matlock, WA and Molalla, OR): Soil water and temperature loggers were downloaded periodically during FY15. Light intensity at 50-cm height (via the Decagon AccuPAR sensor) was measured in each plot during July 2015. Goal 3 (Recovery of soils and plant communities impacted by Scotch broom): Soil samples collected in the Scotch broom removal studies in October 2013 were analyzed to quantify potential differences in soil chemistry between "broom retained" and "broom excluded" treatments. Results were summarized in a manuscript that is under consideration for publication by the scientific journal, Plant and Soil. Cover of each plant species was recorded in the Scotch broom additionandScotch broom removal studies in July 2015. A journal manuscript has been drafted that reports three-year vegetation responses to logging debris and herbicide treatments in the Dry Bed Creek Study.

Publications

  • Type: Journal Articles Status: Published Year Published: 2014 Citation: Harrington, T.B. 2014. Synthetic auxin herbicides control germinating Scotch broom (Cytisus scoparius). Weed Technology 28(2): 435-442.
  • Type: Other Status: Published Year Published: 2014 Citation: Harrington, T.B. and S.M. Holub. 2014. Managing for long-term soil productivity in Pacific Northwestern forests. Western Forester 59(3): 1-4.
  • Type: Conference Papers and Presentations Status: Other Year Published: 2014 Citation: Harrington, T.B., D.H. Peter, and R.A. Slesak. 2014. Effects of logging debris and herbicide combinations on forest plant species. Meeting the Challenge: Predicting, Detecting, and Controlling Invasive Plants, University of Washington, Seattle, WA. September 16-17, 2014.
  • Type: Conference Papers and Presentations Status: Other Year Published: 2014 Citation: DeBruler, D.G., S.H. Schoenholtz, B.D. Strahm, R.A. Slesak, and T.B. Harrington. 2014. Soil carbon and nutrient pools: responses to competing vegetation control and harvest residual retention after ten years in two Douglas-fir stands of the Pacific Northwest. Annual meeting of the Soil Science Society of America, November 2-5, Long Beach CA.
  • Type: Conference Papers and Presentations Status: Other Year Published: 2015 Citation: Harrington, T.B., D.H. Peter, and R.A. Slesak. 2015. Two-year survival and growth responses of planted Douglas-fir to logging debris and herbicide combinations designed to control Scotch broom and other competitors. Annual meeting of the Western Society of Weed Science. Portland, OR. March 9-12, 2015.
  • Type: Conference Papers and Presentations Status: Other Year Published: 2015 Citation: Peter, D.H. and T.B. Harrington. 2015. Three-year responses of forest plant species to logging debris and herbicide combinations. Annual meeting of the Western Society of Weed Science. Portland, OR. March 9-12, 2015.
  • Type: Other Status: Published Year Published: 2015 Citation: Harrington, T.B. and D.H. Peter. 2015. Herbicides: an unexpected ally for native plants in the war against invasive species. Science Findings, PNW Research Station, August Issue (no. 176), 5 p.
  • Type: Journal Articles Status: Under Review Year Published: 2015 Citation: Slesak, R.A., T.B.Harrington, and A.W. DAmato. 2015. Invasive Scotch broom alters soil chemical properties in Douglas-fir forests of the Pacific Northwest, USA. Plant and Soil (in review).


Progress 09/01/13 to 08/31/14

Outputs
Target Audience: Plant biologists, ecologists, and soil scientists; foresters andvegetation managers; non-native invasive plant specialists. Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Tim Harrington served as co-organizer, section moderator, and discussion panelist for the following professional meeting: "Meeting the Challenge: Preventing, Detecting, and Controlling Invasive Plants," University of Washington, Seattle WA, September 16-17, 2014. How have the results been disseminated to communities of interest? Research presentations: Harrington, T.B., R.A. Slesak, and A.W. D’Amato. 2014. Scotch broom alters Douglas-fir community structure and soil ecology: Prevention and mitigation through alternative management practices. Annual meeting of the Weed Science Society of America, February 3-6, 2014, Vancouver, BC, Canada. Meeting included a session for reporting progress on NIFA-supported research. Harrington, T.B. and D.H. Peter. 2014. Effects of logging debris and herbicide treatments on abundance of nonnative plant species after forest harvesting in western Washington. Meeting the Challenge: Preventing, Detecting, and Controlling Invasive Plants, Seattle WA, September 16, 2014. Technical presentations: Harrington, T.B. 2013. Considerations for controlling invasive plants in restoration projects. Western Native Plants Conference, Vancouver, WA. December 11, 2013. Harrington, T.B. 2014. Scotch broom research: regeneration, impacts, and control. Forest Chemical Seminar, Wilbur-Ellis, Inc. Presented at meetings in: (1) Albany, OR (February 12) and (2) Chehalis, WA (February 13). Over 80 people attended each of the meetings. Harrington, T.B. 2014. Managing disturbance and debris to benefit the regenerating stand. Annual meeting of the Oregon State Society of American Foresters, Canyonville, OR. April 30-May 1, 2014. Over 300 people were in attendance, including members of forest industry and public forestry agencies. Harrington, T.B. 2014. Treatments for preventing and controlling Scotch broom. Practical Applications in Vegetation Management, Coos Chapter, Oregon State Society of American Foresters, Coos Bay, OR. June 4, 2014. Over 90 people attended the meeting. What do you plan to do during the next reporting period to accomplish the goals? Goal 1: 1. Measure second-year survival and growth of planted Douglas-fir in the Dry Bed Creek Study. 2. Conduct a growth chamber study to determine effects of varying R:FR ratio on Scotch broom seed germination and seedling growth. 3. Conduct statistical analyses of existing data. Goal 2 (Scotch broom additionand Scotch broom removal studies): 1. Continue to monitor soil water and soil temperature. 2.Measure coverby plant species and soil water chemistry from lysimetry. 3. Continue to maintain the specifications of the experimental treatments in the Scotch broom addition and removal studies, such as removalof associated vegetationandremovalof new broom seedlings. 3. Conduct statistical analyses of existing data. Goal 3 (Scotch broom removal study): 1. Conduct astatistical analysis ofsoil chemistry datato determine if differences exist between treatments (1) (broom kept out since 2003) and (2) (broom invaded in 2003). 2. Recruit a Ph.D. student to study effects of Scotch broom on soil chemistry, and the potential to mitigate these effects from removal of the species.

Impacts
What was accomplished under these goals? Goal 1: 1. The following data were collected in FY14 from the Dry Bed Creek Study (compares logging debris and herbicide treatment combinations on Scotch broom abundance and Douglas-fir performance): -First-year survival and growth of planted Douglas-fir (seedlings planted early spring 2013). -Third-year abundance of associated vegetation by species (final measurement; previously collected data includemeasurementsfor 0, 1, and 2 years after installation of the three logging debris treatments in December 2011). -Density of new Scotch broom seedlings in June and July 2014 (final measurement will beOctober 2014; previously collected data include measurements in June, July, and October of 2012 and 2013). - Ongoing measurements of soil water content (5-25 cm depth) and soil temperature (5-cm depth) downloaded periodically from sensors installed within selected plots. 2. Data from the debris depth study (conductedin early 2013) were analyzed, including Scotch broom seedling emergence, survival, and growth and light intensity and spectral characteristics. 3. Two growth chambers were outfitted with LED light banks to test the effects of altered red:far red (R:FR) ratios on Scotch broom seed germination and seedling growth. In one chamber the lightfixturesincluded far redLED's(730 nm wavelength), which wereabsent inthe other chamber. A preliminary trialof Scotch broom germination was conducted to test the feasibility of this experimental approach. Additional modifications will be made to the lightsettings to better manipulate the R:FR ratio, and a more detail experiment will be run in FY15. Goal 2: 1.At the Dry Bed Creek Study site, a Scotch broom addition study was installed in early 2013with the following 2x2 factorial of treatments, each replicated 10 times in 2x2 m plots: presence versus absence of a planted broom seedling with and without control of associated vegetation. To identify potential changes in soil chemistry, pre-treatment soil samples were collected from 6 replications of each treatments at 0-15 and 15-30 cm depth increments. Sensors were installed to measure soil water content (30-cm depth) and soil temperature (15-cm depth)within the same 6 replications of each treatment, and data from these sensors has been downloaded periodically since installation. Tension lysimetersalso wereinstalled withinthe same 6 replications inspring2014, and soil water solution samples were collected biweekly throughout the growing season. Growth measurements were taken on the planted broom seedlings at the end of 2013. 2. A Scotch broom removal study was installed at each of the Matlock and Molalla long-term soil productivity study sites. This study will serve a dual purpose of addressig some of the experimental hypotheses in Goals 2 and 3. Treatments werereplicated 10 times via 3-m radius circular plotsand include: (1) Scotch broom kept out since 2003, (2) Scotch broom invaded in 2003, and (3) Scotch broom invaded in 2003 but removed in fall 2013.At study initiation, stem diameter(s) and heights were measured on existing Scotch broom plants within each plot.Stem cross sections were collected from each plot to age the Scotch broom plants. To identify potential changes in soil chemistry, pre-treatment soil samples were collected fromeach treatment replication at 0-15 and 15-30 cm depth increments. Soil temperature sensors were installed in each treatment replication at 15-cm depth, and soil watersensors were installed at 30-cm depth in each replication of treatments (2) and (3).These sensorswere downloaded periodically during 2014. Goal 3: 1. Soil samples from the Scotch broom removal study are currently being analyzed in the soil testing lab at Virginia Tech to determine baseline values for carbon, nitrogen, and selected cations, as well as to formally compare soil chemistry in treatments (1) and (2). 2. Coverof each plant species was recorded within each plot of boththe Scotch broom additionstudy and the Scotch broom removal study. These data will be used to assess changes in the plant community composition and structure attributable to presence, removal,or absence of Scotch broom.

Publications