Recipient Organization
UNIVERSITY OF WASHINGTON
4333 BROOKLYN AVE NE
SEATTLE,WA 98195
Performing Department
Sustainable Resource Management
Non Technical Summary
Intensive management of the conifer-dominated forests of the Pacific Northwest (PNW) has resulted in millions of acres of largely mono-specific second and third growth forests. These forests have simple vertical structure, low biodiversity, and consequently much lower value of non-timber forest products. Research on establishment of underplanted trees in partial light is needed to increase structural and compositional diversification of Douglas-fir plantations undergoing conversion to multispecies stands. However, the ecology of seedling establishment under existing canopies is poorly understood. The general aim of our research is to address the need for improved structural diversity in managed forest systems through a better understanding of species-specific performance potential of underplanted seedlings. This project extends ongoing research; in this phase we will document physiological differences in seedling performance.
Animal Health Component
(N/A)
Research Effort Categories
Basic
100%
Applied
(N/A)
Developmental
(N/A)
Goals / Objectives
A. Measure the growth and physiological response of 9 species of seedlings to post-harvest environments resulting from alternative (i.e. ecologically minded) silvicultural practices that impact light and water availability (e.g. aggregate or dispersed retention, gaps, corridors, etc.).B. Assess field and control site environmental conditions for use in determining ecophysiological relationships of 9 species of seedlings in the study (i.e. by linking photosynthesis, stem water potential, chlorophyll flouresence measurements from objective A to the environmental data).C. Using statistical analysis, assess and contrast species-specific thresholds of tolerance for planted stock establishment in the study region.
Project Methods
In this project, we will complete the second phase of an existing plan ofresearch: First phase: Completed in 2015The study incorporates the following native tree species of which seed provenance and nursery culture were coordinated to improve regional relevance and reduce confounding effects potentially introduced by nursery culture: Abies grandis, Acer macrophylum, Alnus rubra, Larix occidentalis, Pinus monticola, Pinus ponderosa, Pseudotsuga menziesii, Thuja plicata, and Tsuga heterophyla.Seedlings of each species were planted in replicated plots in three different light regimes selected to represent conditions found in commercial operations in even-aged, mature Douglas-fir stands. Light levels vary from relatively open (i.e., full sun) to subsequent reductions of 30% and 70% available light, respectively, a spectrum that spans potential retention levels following clearcut and partial harvest. In and ex situ trials have been installed in parallel to validate findings with reduced confounding nursery stock and environmental variation. Field research sites include (UW) Pack Forest, the Cedar and Tolt River Watersheds,Elk Heights (near Cle Elum, WA), and control plots at the (UW) Center for Urban Horticulture.Following planting in the spring of 2015, seedlings have been monitored for survival, morphological development (growth), and aboveground physiology (chlorophyll fluorescence, Fv/Fm). The evaluations continued through the autumn of 2015 and will restart in 2016 with additional evaluations that are to be targeted based on this project.Second Phase: Targeted by this projectThis phase of the research projectis planned for spring and summer 2016 and will include assessments of seedling photosynthetic capacity, seasonal variation in water potential, as well as continued monitoring of plant morphology and nutrient translocation. Additionally, a comprehensive assessment of environmental conditions will require hemispherical photography, light readings, local weather data, and assessments of edaphic conditions (i.e. competition, moisture, and substrate).Objective A. Seedlings will be measured throughout the growing season at all field sites and the control site. In situ measurement will take place for all non-destructive assessments including seedling height, root-collar diameter, ocular assessments of vigor and browse, chlorophyll fluorescence, and light curves. Destructive sampling (with the exception of plant moisture stress, which will be measured on site) will be conducted post-harvest at the University of Washington Laboratory facilities in Winkenwerder Hall or at the Center for Urban Horticulture in Seattle, Washington. A subset of samples may be sent to regional laboratories for carbon and nitrogen combustion analysis if costs permit.Objective B. Light sensing ceptometers and hemispheric photography will be employed mid-season to capture the light environment and canopy architecture at field and control sites, respectively. Temperature and precipitation data will be downloaded from regional weather stations and supported by a suite of iButton sensors (collecting temperature and relative humidity at soil and seedling level) to be installed at each plot in Spring of 2016 prior to the start of this phase of the study. Surface soil (10 cm depth) moisture will be assessed using a Campbell Hydrosense™ soil moisture sensor at regular intervals throughout the spring and summer season. Additionally, site features including competing vegetation, soil substrate, microsite features, and any additional ocular assessments of the biophysical environment will be assessed late-spring to mid-summer depending on the weather and precipitation. Finally, an inventory of field sites will complement this phase by providing an assessment of stand density.Objective C. Data will be analyzed using R statistical system (R Core Team, 2015). All morphological, physiological response variables as well as all environmental variables will be classified and analyzed using a one-way ANOVA following each measurement period; pair-wise comparison may be made using Tukey's HSD (α = 0.05). When values fail to meet the assumptions for a general linear model (normality and homogeneity of variances), non-parametric tests will be employed. Nutrient analysis will facilitate the understanding of outcomes from nursery culture and following second year field performance. All data will contribute to dissertation chapters and summary publications as final direct outcomes of this project.