Search

The evolution of disciplinary silos and increasingly narrow disciplinary boundaries have together resulted in one‐sided approaches to the study of land‐atmosphere interactions—a field that requires a bi‐directional approach to understand the complex feedbacks and interactions that occur. The integration of surface flux and atmospheric boundary layer measurements is therefore essential to advancing our understanding. The Land‐Atmosphere 2021 workshop (held virtually, June 10‐11, 2021) involved almost 300 participants from around the world and promoted cross‐discipline collaboration by way of talks from invited speakers, moderated discussions, breakout sessions, and a virtual poster session. The workshop focused on five main theme areas: "big picture" overview, instrumentation and remote sensing, modeling, water, and aerosols and clouds. In talks and breakout groups, there were frequent calls for more AmeriFlux sites to be instrumented for boundary layer height measurements, and for the development of some "super sites" where profiling instruments would be deployed. There was further agreement on the need for the standardization of various datasets. There was also a consensus that funding agencies need to be willing to support the sorts of large projects (including associated instrumentation) which can drive interdisciplinary work. Early‐career scientists, in particular, expressed enthusiasm for working across disciplinary boundaries but noted that there need to be more financial support and training opportunities so they would be better prepared for interdisciplinary work. Investment in these career development opportunities would enable today's cohort of early‐career scientists to advance the frontiers of interdisciplinary work over the next couple of decades. Plain Language Summary: The hypothesis we investigate is that a more collaborative, interdisciplinary approach is needed to advance the science of land‐atmosphere interactions. We provide historical perspective by discussing the evolution of the field of land‐atmosphere interactions but note that in recent decades, narrow disciplinary boundaries have emerged as a barrier to progress. However, synergies between newly developed observational capacities, and the power of a network‐based approach centered around AmeriFlux, have the potential to revolutionize the field over the coming decade. This background provides a summary of the keynote talks presented at the virtual Land‐Atmosphere 2021 workshop, in which 300 scientists from around the world participated this past June. The keynote talks offered a range of perspectives on key knowledge gaps and set up discussions on proposed new measurements and opportunities for future cross‐disciplinary collaboration. The main conclusions emerging from the final plenary discussion session at this workshop include the need to improve the availability and accessibility of key data sets; the need for federal agencies to provide funding support for large, interdisciplinary projects; and the need for training and other career development opportunities, particularly for early career scientists. Our review highlights the key challenges and opportunities facing the field of land‐atmosphere interactions. Key Points: The field of land‐atmosphere interactions can be advanced through emerging technologies to characterize the atmospheric boundary layerCross‐disciplinary research is needed but would require new funding mechanisms to tackle transformative research questionsTraining programs for early career scientists are essential so that they are prepared to work across disciplinary boundaries [ABSTRACT FROM AUTHOR]

In eastern North America, many deciduous forest ecosystems grow at the northernmost extent of their geographical ranges, where climate change could aid or impede their growth. This region experiences frequent extreme weather conditions, allowing us to study the response of these forests to environmental conditions, reflective of future climates. Here we determined the impact of seasonal and annual climate variations and extreme weather events on the carbon (C) uptake capacity of an oak‐dominated forest in southern Ontario, Canada, from 2012 to 2016. We found that changes in meteorology during late May to mid‐July were key in determining the C sink strength of the forest, impacting the seasonal and annual variability of net ecosystem productivity (NEP). Overall, higher temperatures and dry conditions reduced ecosystem respiration (RE) much more than gross ecosystem productivity (GEP), leading to higher NEP. Variability in NEP was primarily driven by changes in RE, rather than GEP. The mean annual GEP, RE, and NEP values at our site during the study were 1,343 ± 85, 1,171 ± 139, and 206 ± 92 g C m−2 yr−1, respectively. The forest was a C sink even in years that experienced heat and water stresses. Mean annual NEP at our site was within the range of NEP (69–459 g C m−2 yr−1) observed in similar North American forests from 2012 to 2016. The growth and C sequestration capabilities of our oak‐dominated forest were not adversely impacted by changes in environmental conditions and extreme weather events experienced over the study period. Plain Language Summary: Globally, forests are an important carbon sink, removing carbon dioxide from the atmosphere on an annual basis. Midlatitude temperate deciduous forests are an important component of the global forest carbon sink, representing ~11% of the global carbon stock. The strength of carbon uptake by these forests remains uncertain under future climate projections. With increasing temperatures and changes in precipitation patterns expected in many regions, tree species may advance north, changing the carbon uptake capacities of local forest ecosystems. In addition, extreme weather events such as heat waves and droughts may place these forests under added stress and reduce their carbon sink capacities. Our study found that despite frequently changing environmental conditions, an oak‐dominated forest, growing at the northernmost extent of temperate deciduous forests within the Great Lakes region of North America, was a strong sink of carbon with mean annual net ecosystem productivity of 2 t of C per hectare per year. Key Points: Seasonal and annual carbon fluxes were studied from 2012 to 2016 at a mature temperate deciduous forest in southern Ontario, CanadaMeteorological conditions over a short midsummer period greatly impacted annual NEPOn average, the forest was an annual carbon sink of 206 ± 92 g C m−2 yr−1 [ABSTRACT FROM AUTHOR]