Tag: Lucas Silva

Refining cloud exclusion methods in tropical montane forest change detection with Landsat timeseries

Presenter: Sophia Shuler – Geography, Spatial Data Science and Technology

Faculty Mentor(s): Lucas Silva

Session: (In-Person) Poster Presentation

Satellite based remote sensing is one of the most accessible methods for implementing large-scale terrestrial change detection. However, cloud cover contamination of images is a frequent barrier to the use of change detection algorithms, particularly in places where cloud cover is frequent, such as in tropical mountains. In this project, I offer a method for cloud detection that can improve the quality of satellite image time series in tropical regions. Using both a cloud mask and a cloud index, I detected clouds in a set of Landsat-5 TM and Landsat-7 ETM+ time series from a tropical montane forest in Oaxaca, Mexico to a higher degree of accuracy than would be achieved by using the cloud mask alone. This method was used in sequence with the Breaks For Additive Season and Trend (BFAST) method in order to detect forest disturbances. After using a cloud index threshold of 2.8, the percentage of clouds detected increased from 91.8% to 94.4%. Additionally, this method yielded a 161% increase in the number of forest disturbances detected by BFAST. These results are applicable to change detection projects in regions with frequent cloud cover, where accuracy is limited by the climate conditions.

 

Measuring soil respiration in response to enhanced silicate weathering and mycorrhizal associations

Presenter: Emily Scherer – Biology

Faculty Mentor(s): Hilary Rose Dawson, Lucas Silva

Session: (In-Person) Poster Presentation

Enhanced silicate weathering (ESW) is emerging as a top contender to reduce atmospheric carbon and mitigate climate change by accelerating soil C sequestration. However, little is known about ESW’s potential for success on global and regional scales. Applying basalt dust to soil can draw down atmospheric C, boost nutrient availability for crops, and counter soil acidification, yet it may also heighten microbial activity and release soil C via respiration. Arbuscular mycorrhizae (AM), ectomycorrhizae (EcM), and plant community composition can also alter weathering rates. Our research tests soil respiration rates in the presence of basalt dust and mycorrhizal associations in local Willamette Valley soils. We hypothesize that respiration will increase due to the fertilizing effects of basalt but that a faster pace of weathering will result in a net C sink. We predict that respiration and sequestration will be greatest in the presence of EcM fungi. To test this theory, we potted four tree species, each known to form an AM or EcM relationship, in soil mixed with none, low or high concentrations of basalt dust. We measured baseline soil pH, initial C stocks, and nutrients. Currently, we are measuring respiration using a soil CO2 flux chamber. As the project advances, we will measure changes to these variables, plant biomass, and inorganic C stocks. This study will contribute to the literature regarding the potential of ESW to offset anthropogenic C emissions.

Quantifying soil respiration response to planted conifer saplings and associated mycorrhizae

Presenter: Julia Odenthal – Environmental Studies

Faculty Mentor(s): Lucas Silva

Session: (In-Person) Poster Presentation

Forest soils present a crucial opportunity for carbon sequestration to combat rising atmospheric greenhouse gas concentrations. To better understand the impact of tree planting on soil carbon storage within a previously unforested grass field in Oregon’s Willamette Valley, we will measure soil microbial respiration at the base of two conifer seedlings with different mycorrhizal associations: Calocedrus decurrens (arbuscular mycorrhizae; AM) and Pinus ponderosa (ectomycorrhizae; EcM). We will compare these measurements with soil respiration in plowed furrow replicates at a five foot distance from the sample trees and in unplowed pasture. We hypothesize that soil respiration will be higher next to seedlings compared to pasture and disturbed ground, and that AM seedlings will have higher soil respiration rates than EcM seedlings. In addition, we will measure pH, soil carbon, macronutrient, and micronutrient levels at the same locations to compare soil conditions that may alter microbial communities. Microbial function at the roots of planted trees has been shown to have some control on carbon sequestration through enhanced weathering, suggesting that current models may underestimate the carbon storage potential of forested soils. Understanding the potential of carbon sinks is key to properly allocating resources for climate change mitigation. Our data will guide future local tree planting efforts to maximize soil carbon storage.

Does plant community diversity change with terrain steepness in southwestern Oregon?

Presenter: Delaney Kleiner − Biology, Environmental Science

Faculty Mentor(s): Lucas Silva, Brooke Hunter

Session: (In-Person) Poster Presentation

Southwestern Oregon is characterized by complex patterns of plant communities across environmental gradients. Previous research has found the structure and composition of vegetation to be related to the complex geology of this region. In this study, we explore the relation between topography and plant communities by asking if and how vegetation changes across ridgelines of varying steepness. We selected six ridgelines with a gradient of slope steepness (steep to gentle) in Rabbit Mountain, Riddle, Oregon and used quadrat and line-point intercept techniques to quantify vegetation cover by species at each site. We assessed the differences and similarities between plant communities with NMDS (non-metric multidimensional scaling) analysis. We found plant communities on steep ridgelines are significantly different than communities on gentle ridgelines. Studying how landscapes exist in relation to vegetation deepens our understanding of the connectedness of Earth’s processes, emphasizes the interdisciplinary nature of environmental science, and further informs forestry management practices in a time of increasing climate change.

Determining Soil Organic Carbon Values in Association With Vegetation Community Types in the Chewaucan River Basin

Presenter(s): Aaron Lefore − Environmental Science

Faculty Mentor(s): Lucas Silva, Schyler Reis

Poster 71

Research Area: Physical Science

The terrestrial carbon pool, especially soils, have the potential to sequester large amounts of carbon by way of below ground carbon flux. However, the degree of carbon sequestration into soils is dependent upon the structure of the vegetation communities inhabiting them and the unique qualities of the soil itself. This study focuses on below ground carbon concentrations, specifically soil organic carbon (SOC), in relation to vegetation communities in the Chewaucan River Basin in southern Oregon. Over time, management practices within the Chewaucan site have resulted in major vegetation shifts, defined by woody Juniper encroachment, cheatgrass invasion, and dryland agriculture practices. To calculate SOC, cores from the top 10cm of soil were taken from different vegetation community plots across the site that included Juniper, Ponderosa Pine, sagebrush, Juniper/Pine, and alfalfa. Samples were dried to determine bulk density, texture, and Munsell color system rating. Soil sieving separated samples into coarse earth (>2.00mm) and fine earth fractions (< 2.00mm). A loss on ignition (LOI) test was completed on 5.00g fine earth from each sample to determine SOC values. Simple calculations show woody species (Ponderosa, and Juniper) plots having slightly elevated SOC concentrations than shallow rooted species (sagebrush, alfalfa). However, more complex analytical procedures will be completed using R statistical computing that account for multiple variables across all plots. This study has the potential to quantify SOC concentrations of soils that have not previously been analyzed. More importantly, this research could predict changes in SOC within rapidly changing ecosystems like the Chewaucan River Basin.