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Novel determination of effective freeze–thaw cycles as drivers of ecosystem change
Author(s) -
Boswell Edward P.,
Thompson Anita M.,
Balster Nick J.,
Bajcz Alex W.
Publication year - 2020
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.1002/jeq2.20053
Subject(s) - ftcs scheme , biogeochemical cycle , ecosystem , environmental science , climate change , structural equation modeling , ecology , physical geography , mathematics , differential equation , geography , statistics , biology , differential algebraic equation , mathematical analysis , ordinary differential equation
Abstract Soil freeze–thaw cycles (FTCs) profoundly influence biophysical conditions and modify biogeochemical processes across many northern‐hemisphere and alpine ecosystems. How FTCs will contribute to global processes in seasonally snow‐covered ecosystems in the future is of particular importance as climate change progresses and winter snowpacks decline. Our understanding of these contributions is limited because there has been little consideration of inter‐ and intrayear variability in the characteristics of FTCs, in part due to a limited appreciation for which of these characteristics matters most with respect to a given biogeochemical process. Here, we introduce the concept of effective FTCs: those that are most likely linked to changes in key soil processes. We also propose a set of parameters to quantify and characterize effective FTCs using standard field soil temperature data. To put these proposed parameters into effective practice, we present FTCQuant , an R package of functions that quantifies FTCs based on a set of user‐defined parameter criteria and, importantly, summarizes the individual characteristics of each FTC counted. To demonstrate the utility of these new concepts and tools, we applied the FTCQuant package to re‐analyze data from two published studies to help explain over‐winter changes to N 2 O emissions and wet‐aggregate stability. We found that effective FTCs would be defined differently for each of these response variables and that effective FTCs provided a 76 and 33% increase in model fit for wet‐aggregate stability and cumulative N 2 O emission, respectively, relative to conventional FTC quantification methods focusing on fluctuations around 0 °C. These results demonstrate the importance of identifying effective FTCs when scaling soil processes to regional or global levels. We hope our contributions will inform future deductions, hypothesis generation, and experimentation with respect to expected changes in freeze–thaw cycling globally.