A seed’s successful transition to a seedling depends on the suitability of the surrounding environment. All plants need water, sunlight, favorable temperatures, and soil nutrients to survive. On top of these essentials, interactions with other organisms through competition, herbivory, or disease may also have an impact. The goal of this study is to assess which factors influence tree germination in Washington’s temperate forests. Are there essentials without which seeds fail to complete the pivotal transition between embryo and tree? This question was explored using data collected since 2014 in a 25.6 hectare plot located in the Gifford Pinchot National Forest (WA). The dominant trees here, including Western hemlock and Douglas fir, were the focus species of this study. Forty seed traps distributed throughout the plot collected falling tree seeds so that they could later be identified to species and counted in the lab. Germinants and seedlings were recorded within a square meter adjacent to each seed trap, along with environmental factors such as soil moisture and sun exposure. Regression analyses were used to assess whether germination rates (the proportion of seeds that successfully germinated) were influenced by environmental factors, other organisms, seed densities, or year. While analyses and data collection are ongoing, results thus far indicate a negligible role for soil moisture and sunlight in germination. On the other hand, the presence of other vegetation decreased germination, while the presence of nurse logs increased it. Germination is an important and delicate life stage for every tree, and through their influence on it environmental factors may shape the species composition of these communities. Identifying relevant factors may also provide some ability to anticipate how these trees will respond to the warmer and drier conditions expected to define climate change in the Pacific Northwest.

In many plant species, temperature and herbivory have been shown to affect photosynthetic rates, and thus, capacity for growth. However, few studies have looked at  the combined effects of temperature and herbivory on plant performance. This is important, as increases in temperature and rates of herbivory are predicted to coincide with climate change. To address this issue, Lupinus latifolius, a perennial plant native to the western coast of the United States, was studied. L. latifolius was chosen because it is a nitrogen-fixer, and it can facilitate the growth of other plant species in disturbed habitat. As such, observing how L. latifolius responds to future conditions we expect with climate change can provide insight about how plant communities will respond in the future. In this experiment, two growth chambers were used, and L. latifolius plants were placed in one of four treatment groups. The treatment groups were organized so the combined effects of temperature and herbivory could be compared to the standalone effects of temperature and herbivory. For the herbivory treatments, grasshoppers were used. MultispeQ, a portable plant-phenotyping instrument, was used to capture photosynthetic parameters and relative chlorophyll. Certain morphological traits, such as plant height and leaf mass per area (LMA), were also measured. I expect that higher temperatures will result in higher photosynthetic rates, but that herbivory will have a larger negative impact on photosynthesis. As a result, lower photosynthetic rates are likely to be observed under increased temperature and herbivory. T tests and ANOVA were conducted to determine whether differences between treatments are statistically significant. By conducting this research, we can gain a better understanding of how changes in temperature and herbivory rates associated with climate change can interact to affect plant performance and health.

What drives change in populations of endangered species such as the northern spotted owl (Strix occidentalis caurina)? Despite northern spotted owl populations in Washington declining yearly, variability in year to year population performance suggests that understanding what facilitates a “good” year for this endangered species may improve management practices. It is possible that resource pulses, distinct increases in ephemeral resources occurring at infrequent time intervals, influence this variation. “Masting” is a type of resource pulse in terrestrial ecosystems characterized by large increases in seed or fruit production, which may raise abundance of small mammals that consume seed. For example, northern flying squirrels (Glaucomys sabrinus), have been found to respond positively to mast events from the previous autumn. Because northern flying squirrels are a primary prey item of S. occidentalis, constituting up to 81% of its diet by biomass, spotted owl numbers and seed masting events may be correlated. To elucidate this relationship, I used seed production data collected in Mt. Rainier National Park (MORA) since 2008 by the Hille Ris Lambers Lab, in conjunction with northern spotted owl demographic data from the National Park Service. An estimated 80,000 acres of suitable spotted owl habitat exist in MORA extending to altitudes of 4,800 feet, dominated by Psuedotsuga menziesii, three Abies species, Thuja plicata, and Tsuga heterophylla — trees which mast and may be consumed by small mammals. We hypothesize that a mast event will produce a resource pulse of seeds which may heighten flying squirrel abundance, resulting in increased northern spotted owl population two years after the seed mast event. This hypothesis predicts a positive correlation between seed production and adult northern spotted owl population two years post mast event. This study will improve knowledge of spotted owl population dynamics and potentially improve management protocol of Strix occidentalis caurina in MORA.