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Assessing the impacts of disturbances on soil carbon cycling

Project Abstract: 
Project objectives: The overarching goal of this project is to determine the response trajectory of soil carbon cycling processes following disturbances. The specific objective of this project is to examine the impact of disturbance severity on (A) total carbon losses from soil as carbon dioxide, and (B) carbon stored in different soil carbon pools within the soil profile. Project description: Disturbances can disrupt soil processes that regulate the global carbon - climate feedbacks and are also expected to increase in frequency and magnitude over the next decades due to a warmer climate and the intensification of human activities worldwide. These shifts in disturbance regimes (e.g., size, frequency, and severity) will potentially increase the vulnerability of soil carbon storage by disrupting plant-soil interactions and accelerate the emissions of greenhouse gases to the atmosphere. However, the impact of disturbances on belowground carbon cycling has received little attention when compared to aboveground processes, hampering our ability to further advance our understanding of climatic and human- driven impacts on the global carbon cycle. Given that belowground processes are important regulators of global climate and respond to disturbances, understanding how and why disturbances affect belowground carbon cycling is relevant to predictions of disturbance impacts on the global carbon cycle. As part of the FoRTEUnderground research, this project will quantify the impact of disturbance severity on carbon fluxes and storage. Addressing this knowledge gap is critical to generate novel datasets, design new manipulation studies, and inform predictive models which are known to poorly represent disturbances. Thus, understanding how and why soil C cycling responds to disturbances in various ecosystems across the globe is essential to accurately predict ecosystem response to global change. Understanding the impact of these disturbances on soil C storage, however, requires long-term experimental manipulations designed to test the effects of harvest and fire on belowground C cycling. The FoRTE experiment at the University of Michigan Biological Station (UMBS, Pellston, MI) is the ideal site to evaluate the impacts of disturbances on soil C cycling and facilitate development of a conceptual framework for the impacts of disturbances on belowground processes as feedbacks between plants and soils likely drive responses of soil C to disturbances. Leveraging existing FoRTE experiment at the UMBS is ideal for this project as it (a) serves as a natural laboratory for disturbance ecology studies, (b) has a number of researchers with expertise in disturbance ecology, (c) has facilities and resources that can be utilized during field campaigns (i.e., laboratory space, lodging, and dining), and (e) existing datasets (satellite and in situ observations) on canopy structure that are needed for the integration of measurements associated with aboveground ecological attributes and soil C dynamics.
Investigators: 
Status of Research Project: 
Years Active: 
2023 to 2024
Research sites: 
Methods: 
Soil CO 2 efluxes To address objective (A), Dr. Santos plans to visit the UMBS in late April to install eosFD continuous soil CO 2 flux sensors and associated dataloggers across four disturbance severity level treatments (0 or control, 45%, 65, 85%) within one treatment replicate. We will install 2 sensors per severity level and will take advantage of existing infrastructure at the sites. The CO 2 flux sensors will continuously collect soil respiration data for one year or longer, depending on funding. To examine whether there are explanatory relationships between soil respiration and soil properties, Dr. Santos will install water potential and temperature sensors at two depths (7.5 and 20 cm depths) across disturbance replicates and severity level treatments. The data from these sensors will complement the suit of measurements collected from sensors already installed at the site (e.g., soil volumetric moisture). Soil carbon storage To address objective (B) Dr. Santos plans to visit the UMBS in the summer to collect soil samples at different depths (0-15, 15-30, 30-60, 60-100 cm) to evaluate changes in soil C pools across disturbance severity level treatments (0 or control, 45%, 65, 85%). The visit will also include data collection from sensors and any maintenance needed to the infrastructure. Measurements of soil carbon concentration in particulate and mineral-associated organic matter, and microbial biomass will be conducted in Dr. Santos’ lab at ORNL.