About

Angela Possinger is an assistant professor in the School of Plant and Environmental Sciences at Virginia Tech. She is a soil scientist with a specialization in soil organic matter biogeochemistry. Her research program focuses on the basic science and applied challenges of building soil organic matter, which serves as a foundation for restoring soil functions in disturbed systems. She is passionate about teaching soil science and aims to connect the importance of soils to students’ interests across disciplines. Dr. Possinger holds a Ph.D. in Soil and Crop Sciences from Cornell University, an M.S. in Biological and Environmental Science from the University of Rhode Island, and a B.S. in Biology from Roger Williams University. She is based at Virginia Tech, located at 220 Ag Quad Lane, Blacksburg, VA. Her contact email is arp264@vt.edu, and her phone number is 540-231-8887.

Research topics

• Environmental science
• Soil science
• Biology
• Geology
• Chemistry
• Ecology
• Environmental chemistry
• Materials science
• Geography
• Mathematics
• Organic chemistry
• Nanotechnology
• Statistics
• Mineralogy
• Cartography
• Geotechnical engineering
• Oceanography
• Chemical engineering

Selected publications

• Taxonomic and multifunctional response of soil microbial communities to wildfire, prescribed fire, and partial harvesting in the Southern Appalachian Mountains, United States

  Frontiers in Forests and Global Change · 2026-01-30

  articleOpen access

  Southern Appalachian forests have varied land-use history and are managed with different objectives, including maintenance of ecosystem services and harvesting timber. Concurrently, this region has experienced long-term wildfire suppression, causing shifts in dominant vegetation (i.e., mesophication) and is projected to have more frequent, severe drought and wildfire activity in the future. Regional wildland fire effects are not well understood in the context of the broader set of management activities, such as partial harvesting and prescribed burning, that influence soil microbial communities and the ecosystem processes they regulate. We use a taxonomic and multifunctional approach to compare soil across four watersheds with different management or disturbance histories: low-severity prescribed burning, high-severity wildfire, fire exclusion, or partial harvesting. Soil microbial community structure was influenced by historical disturbance effects, while ecosystem functions are constrained by resource availability following recent disturbance. Prescribed burns did not change microbial community composition relative to the fire excluded watershed; however, they did increase N availability and N acquisition enzyme activity. Microbial community structure of the post-wildfire and partially harvested watersheds was influenced by environmental filters related to disturbance, although microbial multifunctionality in the post-wildfire watershed was not significantly different from fire excluded and prescribed burned watersheds. The partially harvested watershed exhibited elevated NO 3 − and pH, increased C acquisition enzyme activity, and lowered C use efficiency relative to other watersheds. This study provides context to microbial influences on ecosystem dynamics following both anthropogenic and natural disturbances, helping managers understand the implications of management on forest soils and belowground processes.

  PublisherOA PDFDOI

• Lifting the profile of deep soil carbon in New Zealand’s managed planted forests

  Carbon Balance and Management · 2025-08-14

  articleOpen access

  BACKGROUND: Forest soils are a globally significant carbon-store, including in deep layers (> 30 cm depth). However, there is high uncertainty regarding the response of deep soil organic carbon (DSOC) to climate change and the resulting impact on the total OC budget for forest ecosystems. Managed forests have an opportunity to reduce the risk of DSOC loss with climate change, however, the basic understanding of DSOC is lacking. Planted forests in New Zealand are managed with very limited knowledge of DSOC, both in the amount and the capacity of the soil to continue to store carbon with climate change. In this study, we explore DSOC stocks to at least 2 m depth at 15 planted forest sties in New Zealand. We also explore DSOC radiocarbon age and soil mineralogy, then contextualise our results within international SOC datasets and climate change vulnerability frameworks to identify research priorities for New Zealand's planted forest soils. RESULTS: DSOC stocks and soil mineralogy in New Zealand's planted forests were diverse both horizontally across soil types and vertically throughout the soil profile. Critically, limiting measurements of SOC to the top 30 cm misses more than half of the SOC stocks present to at least 2 m depth (mean 57%; range 33-72%). At depth, mineral-associated OC was the dominant fraction of DSOC (average > 90%) and was on average much older (> 1000 years) than the current planted forest land use (< 100 years). CONCLUSIONS: This small case study highlights that New Zealand's planted forests contain substantial stocks of DSOC, much of which is older than the current forest land use. The deep soils were dominated by reactive metals, and although the age of DSOC suggest long-term stability, the large contribution of reactive metal-mediated SOC stabilisation may indicate vulnerability to warming soil temperatures relative to other climate change factors. There is a pressing need to expand soil sampling to greater depths and establish a robust SOC baseline for New Zealand's planted forests. This is essential for enabling spatial predictions of DSOC dynamics under future climate scenarios, identify the key controls on DSOC persistence, and concomitant impacts on forest ecosystem function and resilience.

  PublisherOA PDFDOI

• The ecological relevance of fast-cycling mineral-associated organic matter – a dynamic pool of 'persistent’ soil carbon and nitrogen

  2025-05-08 · 2 citations

  preprintOpen access

  Longstanding theories and models classify mineral-associated organic matter (MAOM) as the large (~60%) but slow-cycling and persistent portion of the soil organic matter (SOM) pool. Strong physico-chemical interactions and diffusion limitations restrict the turnover of MAOM, allowing carbon and nitrogen bound therein to persist in soil for as long as centuries to millennia. However, MAOM is a chemically and functionally diverse pool with a substantial portion cycling at relatively fast (i.e., minutes to years) timescales. Despite a growing body of evidence for the heterogenous and multi-pool nature of MAOM, we lack consensus on how to conceptualize and directly quantify fast-cycling MAOM and its ecological significance. We demonstrate the dynamic qualities of fast-cycling MAOM vary based on 1) the chemistry of the mineral particles and organic matter, 2) the complex set of interactions between OM and the mineral matrix, and 3) the presence and strength of destabilizing forces that lead to decomposition or loss of MAOM (i.e., plant-microbe interactions, land use change, agricultural intensification, and climate change). Finally, we discuss potential implications and research opportunities for how we measure, manage, and model the dynamic subfraction of this otherwise persistent pool of SOM.

  PublisherOA PDFDOI

• Evidence for the existence and ecological relevance of fast-cycling mineral-associated organic matter

  Communications Earth & Environment · 2025-08-22 · 27 citations

  articleOpen access

  Longstanding theories and models classify mineral-associated organic matter as the large ( ~ 60%) but slow-cycling and persistent portion of soil organic matter. Strong physico-chemical interactions and diffusion limitations restrict the turnover of mineral-associated organic matter, allowing carbon and nitrogen bound therein to persist in soil for as long as centuries to millennia. However, mineral-associated organic matter is a chemically and functionally diverse pool with a substantial portion cycling at relatively fast (i.e., minutes to years) timescales. Despite a growing body of evidence for the heterogenous and multi-pool nature of mineral-associated organic matter, we lack consensus on how to conceptualize and directly quantify fast-cycling mineral-associated organic matter and its ecological significance. We demonstrate that the dynamic qualities of fast-cycling mineral-associated organic matter vary based on 1) the chemistry of the mineral particles and organic matter, 2) the complex set of interactions between organic matter and the mineral matrix, and 3) the presence and strength of destabilizing forces that lead to decomposition or loss of mineral-associated organic matter (i.e., plant-microbe interactions, agricultural intensification, and climate change). Finally, we discuss potential implications and research opportunities for how we measure, manage, and model the dynamic subfraction of this otherwise persistent pool of soil organic matter. The dynamic qualities of fact-cycling mineral-associated organic matter depend on chemistry between minerals and organic matter, their interactions, and the destabilizing forces causing decomposition, according to a review of recent studies on mineral-associated organic matter across ecosystems

  PublisherOA PDFDOI

• Increasing soil respiration in a northern hardwood forest indicates symptoms of a changing carbon cycle

  Communications Earth & Environment · 2025-05-29 · 8 citations

  articleOpen access1st authorCorresponding

  Soil carbon dioxide (CO2) flux, or soil respiration, is a critical control on net ecosystem carbon (C) balance. Using long-term (2002-2020) measurements at the Hubbard Brook Experimental Forest (New Hampshire, U.S.), we show that soil respiration rates have notably increased since ~2015. In 2020, cumulative summer respiration flux was approximately 90% higher than the average summer flux over the 2002–2015 period. The increase in soil respiration cannot be explained directly by temperature or pH change alone. We also found that heterotrophic microbial C mineralization and microbial biomass C have also increased rapidly since ~2015, pointing towards an increase in the bioavailability of organic C substrates. We suggest that these observations are consistent with a hypothetical increase in plant allocation of C belowground in response to changing climatic and soil conditions. Quantification of interactions among co-occurring global change factors (e.g., warming temperatures, increasing atmospheric CO2, and nutrient limitation) is needed to predict how the soil C reservoir will continue to respond to global environmental changes. Soil respiration rates have almost doubled between 2015-2020 with increased heterotrophic microbial carbon mineralization and microbial biomass, suggesting an increase in the bioavailability of organic carbon, according to an analysis of long-term data from the Hubbard Brook Experimental Forest, U.S.

  PublisherOA PDFDOI

• Examining the role of plant root exudates in formation and disruption of soil organo-mineral associations

  2025-01-01

  articleSenior author
  PublisherDOI

• Root exudates simultaneously form and disrupt soil organo-mineral associations

  Communications Earth & Environment · 2024-11-13 · 47 citations

  articleOpen access

  Organic compounds exuded by plant roots can form organo-mineral associations through physico-chemical interactions with soil minerals but can disrupt existing organo-mineral associations by increasing their microbial decomposition and dissolution. The controls on these opposing processes are poorly understood, as are the chemical and spatial characteristics of these associations which may explain gain or loss of organic matter at the root-soil interface termed the rhizosphere. By pulse-labeling with 13C-carbon dioxide, we found that maize root exudates increased organic matter in the rhizosphere clay size fraction and decreased organic matter in the silt size fraction, and that organic matter loss was mitigated by dry conditions. Organic matter associated with rhizosphere clay particles was linked to microbial metabolism of exudates and was more spatially and chemically heterogeneous than non-rhizosphere clay particles. Our findings show that root exudates can simultaneously form and disrupt organo-mineral associations, mediated by mineral size and composition, and soil moisture. Compounds released by plant roots can stimulate carbon storage in clay fraction of soils and carbon loss in the silt fraction of soils at the same time, according to experiments on maize plants labelled with carbon-13.

  PublisherOA PDFDOI

• Root exudates simultaneously form and disrupt soil organo-mineral associations

  Research Square · 2024-06-24 · 4 citations

  preprintOpen access
  PublisherOA PDFDOI

• Climate and Ecosystem Factors Mediate Soil Freeze‐Thaw Cycles at the Continental Scale

  Journal of Geophysical Research Biogeosciences · 2024-11-27 · 14 citations

  articleOpen accessSenior authorCorresponding

  Abstract Freeze‐thaw cycles (FTC) alter soil function through changes to physical organization of the soil matrix and biogeochemical processes. Understanding how dynamic climate and soil properties influence FTC may enable better prediction of ecosystem response to changing climate patterns. In this study, we quantified FTC occurrence and frequency across 40 National Ecological Observatory Network (NEON) sites. We used site mean annual precipitation (MAP) and mean annual temperature (MAT) to define warm and wet, warm and dry, and cold and dry climate groupings. Site and soil properties, including MAT, MAP, maximum‐minimum temperature difference, aridity index, precipitation as snow (PAS), and organic mat thickness, were used to characterize climate groups and investigate relationships between site properties and FTC occurrence and frequency. Ecosystem‐specific drivers of FTC provided insight into potential changes to FTC dynamics with climate warming. Warm and dry sites had the most FTC, driven by rapid diurnal FTC close to the soil surface in winter. Cold and dry sites were characterized by fewer, but longer‐duration FTC, which mainly occurred in spring and increased in number with higher organic mat thickness (Spearman's ⍴ = 0.97, p &lt; 0.01). The influence of PAS and MAT on the occurrence of FTC depended on climate group (binomial model interaction p (χ 2 ) &lt; 0.05), highlighting the role of a persistent snowpack in buffering soil temperature fluctuations. Integrating ecosystem type and season‐specific FTC patterns identified here into predictive models may increase predictive accuracy for dynamic system response to climate change.

  PublisherOA PDFDOI

• Moisture-driven divergence in mineral-associated soil carbon persistence

  Proceedings of the National Academy of Sciences · 2023 · 132 citations

  • Environmental science
  • Soil science
  • Ecology

  Mineral stabilization of soil organic matter is an important regulator of the global carbon (C) cycle. However, the vulnerability of mineral-stabilized organic matter (OM) to climate change is currently unknown. We examined soil profiles from 34 sites across the conterminous USA to investigate how the abundance and persistence of mineral-associated organic C varied with climate at the continental scale. Using a novel combination of radiocarbon and molecular composition measurements, we show that the relationship between the abundance and persistence of mineral-associated organic matter (MAOM) appears to be driven by moisture availability. In wetter climates where precipitation exceeds evapotranspiration, excess moisture leads to deeper and more prolonged periods of wetness, creating conditions which favor greater root abundance and also allow for greater diffusion and interaction of inputs with MAOM. In these humid soils, mineral-associated soil organic C concentration and persistence are strongly linked, whereas this relationship is absent in drier climates. In arid soils, root abundance is lower, and interaction of inputs with mineral surfaces is limited by shallower and briefer periods of moisture, resulting in a disconnect between concentration and persistence. Data suggest a tipping point in the cycling of mineral-associated C at a climate threshold where precipitation equals evaporation. As climate patterns shift, our findings emphasize that divergence in the mechanisms of OM persistence associated with historical climate legacies need to be considered in process-based models.

  PublisherOA PDFDOI

Frequent coauthors

• Johannes Lehmann

  27 shared

• Michael SanClements

  National Ecological Observatory Network

  26 shared

• Adrian C. Gallo

  Oregon State University

  15 shared

• Thiago Massao Inagaki

  13 shared

• L. E. Nave

  Michigan Technological University

  13 shared

• Ingrid Kögel‐Knabner

  Technical University of Munich

  13 shared

• Christopher W. Swanston

  US Forest Service

  12 shared

• Maggie Bowman

  Environmental Molecular Sciences Laboratory

  12 shared

Labs

• School of Plant and Environmental SciencesPI