More Like this

1. Toward a Standardized Method for Quantifying Ecosystem Hot Spots and Hot Moments

   https://doi.org/10.1007/s10021-023-00839-z  

   Walter, Jonathan A. ; Johnson, Robert A. ; Atkins, Jeff W. ; Ortiz, David A. ; Wilkinson, Grace M. ( September 2023 , Ecosystems)
2. Sediment phosphorus composition controls hot spots and hot moments of internal loading in a temperate reservoir

   https://doi.org/10.1002/ecs2.4201  

   Albright, Ellen A. ; Wilkinson, Grace M. ( August 2022 , Ecosphere)
3. Hot Spots and Hot Moments in the Critical Zone: Identification of and Incorporation into Reactive Transport Models

   Arora B., Briggs ; Zarnetske, J. ; Stegen, J. ; Gomez-Velez, J. D. ; Dwivedi, D. ; Steefel, C. ( October 2021 , Biogeochemistry of the Critical Zone)

   Wymore, A. ; Yang, W. ; Silver, W. ; McDowell, B. ; Chorover, J. (Ed.)

   Biogeochemical processes are often spatially discrete (hot spots) and temporally isolated (hot moments) due to variability in controlling factors like hydrologic fluxes, lithological characteristics, bio-geomorphic features, and external forcing. Although these hot spots and hot moments (HSHMs) account for a high percentage of carbon, nitrogen and nutrient cycling within the Critical Zone, the ability to identify and incorporate them into reactive transport models remains a significant challenge. This chapter provides an overview of the hot spots hot moments (HSHMs) concepts, where past work has largely focused on carbon and nitrogen dynamics within riverine systems. This work is summarized in the context of process-based and data-driven modeling approaches, including a brief description of recent research that casts a wider net to incorporate Hg, Fe and other Critical Zone elements, and focuses on interdisciplinary approaches and concepts. The broader goal of this chapter is to provide an overview of the gaps in our current understanding of HSHMs, and the opportunities therein, while specifically focusing on the underlying parameters and processes leading to their prognostic and diagnostic representation in reactive transport models. 

   more » « less
4. Hot Spots and Hot Moments in the Critical Zone: Identification of and Incorporation into Reactive Transport Models

   https://doi.org/https://doi.org/10.1007/978-3-030-95921-0_2  

   Bhavna Arora, Martin A. ( May 2022 , Biogeochemistry of the Critical Zone. Advances in Critical Zone Science)

   Wymore, A.S. (Ed.)

   The Critical Zone encompasses the biosphere and its heterogeneities, with an extremely high differentiation of properties and processes within each compartment from bedrock to canopy, and across terrestrial and aquatic interfaces. Given this complexity, a comprehensive areal characterization of the critical zone environment at multiple temporal resolutions is needed but not always possible, and failing which the ecosystem fluxes, exchange rates and biogeochemical functioning may be under- or over-predicted. The hot spots hot moments (HSHMs) concept provides an opportunity to identify the dominant controls on carbon, nutrients, water and energy exchanges. Hot spots are regions or sites that show disproportionately high reaction rates relative to surrounding area, while hot moments are defined as times that show disproportionately high reaction rates relative to longer intervening time periods (McClain et al. 2003). 

   more » « less
5. Dynamic Controls on Field‐Scale Soil Nitrous Oxide Hot Spots and Hot Moments Across a Microtopographic Gradient

   https://doi.org/10.1029/2019JG005224  

   Krichels, Alexander H. ; Yang, Wendy H. ( November 2019 , Journal of Geophysical Research: Biogeosciences)

   Soil nitrous oxide (N₂O) emissions are highly variable in space and time, making it difficult to estimate ecosystem level fluxes of this potent greenhouse gas. While topographic depressions are often evoked as permanent N₂O hot spots and rain events are well‐known triggers of N₂O hot moments, soil N₂O emissions are still poorly predicted. Thus, the objective of this study was to determine how to best use topography and rain events as variables to predict soil N₂O emissions at the field scale. We measured soil N₂O emissions 11 times over the course of one growing season from 65 locations within an agricultural field exhibiting microtopography. We found that the topographic indices best predicting soil N₂O emissions varied by date, with soil properties as consistently poor predictors. Large rain events (>30 mm) led to an N₂O hot moment only in the early summer and not in the cool spring or later in the summer when crops were at peak growth and likely had high evapotranspiration rates. In a laboratory experiment, we demonstrated that low heterotrophic respiration rates at cold temperatures slowly depleted soil dissolved O₂, thus suppressing denitrification over the 2–3 day timescale typical of field ponding. Our findings show that topographic depressions do not consistently act as N₂O hot spots and that rainfall does not consistently trigger N₂O hot moments. We assert that the spatiotemporal variation in soil N₂O emissions is not always characterized by predictable hot spots or hot moments and that controls on this variation change depending on environmental conditions.

    

   more » « less