Response of plant, microbial, and soil functions to drought and fire in California
California is experiencing changes in precipitation and wildfire regimes. Longer, hotter fire seasons along with extremes in precipitation are expected to continue. Not only do these disturbances affect the productivity and resilience of ecosystems, they also directly impact human health and wellbeing. Soils hold an immense amount of our terrestrial carbon pool, and the microorganisms and minerals in soil affect whether carbon remains in the soil or is released as carbon dioxide. But it is not clear how changing soil moisture and fire regimes will affect how quickly carbon is released as carbon dioxide by microorganisms or how strongly it associates with soil minerals. Our goal is to understand whether the minerals and microbes in soils become less efficient at retaining carbon if they become drier or burned. To this end, we develop and apply methods to quantify how well soil carbon sticks to different soil minerals, and how quickly carbon is decomposed by microorganisms in the context of fire and precipitation disturbances.
Statement of Problem: Soils play a critical role in many ecosystem services that rely on the cycling of carbon and nutrients. Whether or not soils can continue to provide these services is contingent on how much the cycling of carbon and nutrients is altered by expected increases in fire and precipitation variability. However, the dynamic interplay between microbial activity, soil mineralogy, and soil moisture that controls carbon cycling is unconstrained, particularly as we transition to new patterns in fire and precipitation.
Why this Research is Important: Our research improves the basic understanding of how soils and microorganisms will function in California’s future. This information is essential if we want to predict how ecosystems respond to future disturbances. Northern California is incredibly diverse in its geology and climate, which increases complexity but provides an incredible opportunity to disentangle the interacting controls of mineralogy and moisture on microbially driven soil carbon loss and retention. Moreover, understanding of the relative importance of soil mineralogy to organic matter turnover after disturbance will allow for strategic sampling and scaling of site-specific patterns to regional scales.
Objective(s): The objectives of this study are to: (i) parameterize soil carbon cycling with changing soil moisture based on the type of minerals present (e.g. amorphous vs primary) and the way organic matter sticks to the minerals (e.g. adsorption vs in a microbial biofilm); (ii) assess carbon storage and turnover along natural gradients of precipitation, soil moisture, and mineralogy, and (iii) quantify changes in carbon storage and turnover in ecosystems impacted by changing wildfire and soil moisture across diverse lithologies. By achieving these objectives, we will have a more complete understanding of the capacity of soils and microbes to hold onto carbon after disturbance in the complex geological landscape of Northern California.
Methods: We employ a variety of field, laboratory, and data synthesis approaches to quantify the impacts of fire and precipitation on soil biogeochemical processes in the Western U.S. This project uses stable light isotopes (13C, 15N) at natural abundance and enriched levels as a tool to track the formation, recycling, and destabilization of carbon in soils. We quantify carbon as it is transformed by soil microorganisms in the lab and in the field by combining bulk (e.g., dissolved organic matter, total carbon, greenhouse gas production), fraction-based (e.g., sequential dissolutions, size and density fractionation), and spatially resolved (scanning electron microscopy, mid-infrared spectroscopy, Raman spectroscopy) techniques. Our field sites span gradients in soil age (soil chronosequences), precipitation, and disturbance (wildfire) across diverse lithologies in Northern California to link lab process-based measurements to the landscape scale.
Arctic Biogeochemical Response to Permafrost Thaw (ABRUPT)
Forest health and drought response
California is experiencing changes in precipitation and wildfire regimes. Longer, hotter fire seasons along with extremes in precipitation are expected to continue. Not only do these disturbances affect the productivity and resilience of ecosystems, they also directly impact human health and wellbeing. Soils hold an immense amount of our terrestrial carbon pool, and the microorganisms and minerals in soil affect whether carbon remains in the soil or is released as carbon dioxide. But it is not clear how changing soil moisture and fire regimes will affect how quickly carbon is released as carbon dioxide by microorganisms or how strongly it associates with soil minerals. Our goal is to understand whether the minerals and microbes in soils become less efficient at retaining carbon if they become drier or burned. To this end, we develop and apply methods to quantify how well soil carbon sticks to different soil minerals, and how quickly carbon is decomposed by microorganisms in the context of fire and precipitation disturbances.
Statement of Problem: Soils play a critical role in many ecosystem services that rely on the cycling of carbon and nutrients. Whether or not soils can continue to provide these services is contingent on how much the cycling of carbon and nutrients is altered by expected increases in fire and precipitation variability. However, the dynamic interplay between microbial activity, soil mineralogy, and soil moisture that controls carbon cycling is unconstrained, particularly as we transition to new patterns in fire and precipitation.
Why this Research is Important: Our research improves the basic understanding of how soils and microorganisms will function in California’s future. This information is essential if we want to predict how ecosystems respond to future disturbances. Northern California is incredibly diverse in its geology and climate, which increases complexity but provides an incredible opportunity to disentangle the interacting controls of mineralogy and moisture on microbially driven soil carbon loss and retention. Moreover, understanding of the relative importance of soil mineralogy to organic matter turnover after disturbance will allow for strategic sampling and scaling of site-specific patterns to regional scales.
Objective(s): The objectives of this study are to: (i) parameterize soil carbon cycling with changing soil moisture based on the type of minerals present (e.g. amorphous vs primary) and the way organic matter sticks to the minerals (e.g. adsorption vs in a microbial biofilm); (ii) assess carbon storage and turnover along natural gradients of precipitation, soil moisture, and mineralogy, and (iii) quantify changes in carbon storage and turnover in ecosystems impacted by changing wildfire and soil moisture across diverse lithologies. By achieving these objectives, we will have a more complete understanding of the capacity of soils and microbes to hold onto carbon after disturbance in the complex geological landscape of Northern California.
Methods: We employ a variety of field, laboratory, and data synthesis approaches to quantify the impacts of fire and precipitation on soil biogeochemical processes in the Western U.S. This project uses stable light isotopes (13C, 15N) at natural abundance and enriched levels as a tool to track the formation, recycling, and destabilization of carbon in soils. We quantify carbon as it is transformed by soil microorganisms in the lab and in the field by combining bulk (e.g., dissolved organic matter, total carbon, greenhouse gas production), fraction-based (e.g., sequential dissolutions, size and density fractionation), and spatially resolved (scanning electron microscopy, mid-infrared spectroscopy, Raman spectroscopy) techniques. Our field sites span gradients in soil age (soil chronosequences), precipitation, and disturbance (wildfire) across diverse lithologies in Northern California to link lab process-based measurements to the landscape scale.