Seasonal Respiration Carbon Losses Offset by Photosynthetic Carbon Gains During - PowerPoint Presentation

1. Seasonal Respiration Carbon Losses Offset by Photosynthetic Carbon Gains During Anomalous Boreal-Arctic WarmingZhihua Liu, John S. Kimball, Nicholas C. Parazoo, Ashley P. Ballantyne, Wen J. Wang, Nima Madani, Caleb G. Pan, Jennifer D. Watts, Rolf H. Reichle, Oliver Sonnentag, Philip Marsh, Miriam Hurkuck, Manuel Helbig, William Quinton, Donatella Zona, Masahito Ueyama, Hideki Kobayashi, Eugénie S. Euskirchen Contact: Zhihua.liu@mso.umt.edu; Johnk@ntsg.umt.eduResearch QuestionsTo understand the seasonal carbon dynamics and their climatic and environmental controls in high-latitude ecosystems during anomalously warm winter to spring transition in 2015/16 (ΔT = 2.13 ± 2.06 ℃, relative to baseline (2010 to 2014) conditions across Alaska and NW Canada: How does a warm spring affect seasonal CO2 exchange in the boreal-Arctic? Are seasonal dynamics for net CO2 uptake (i.e. photosynthesis minus respiration) congruent with productivity? How sensitive is boreal-Arctic net CO2 exchange to temperature and soil moisture?MethodsNASA Terrestrial Ecology Science Team Meeting, September 23-25, 2019 Fig 1: Conceptual framework showing potential seasonal responses in net ecosystem carbon exchange to boreal-Arctic warm spring anomaly.Fig 2. Environmental and phenological anomaly in 2015 and 2016. Spatial patterns of anomalous snow cover, freeze/thaw, and carbon uptake during the 2015/16 El Niño year. First, second, and third rows show respective spring, fall, and annual anomalies. Fig 3. Site-level (left) and Regional-level (right) comparison in net ecosystem production (NEP) between baseline years (black) and warm years (red) using the different datasets. Shading denotes 1 standard deviation (SD) from the 11 EC locations. Positive (negative) values indicate land as carbon sink (source). Fig 6. Seasonal sensitivity of net ecosystem production (NEP) anomaly to temperature anomaly in boreal and tundra ecoregions, using different datasets, for different seasons. Red symbols denote winter and blue symbols denote spring conditions. Error bars denote 1-SD from the seasonal estimate. Anomaly is calculated as the difference between warm spring years and baseline years.Fig 5. Temperature and soil moisture influence on boreal-Arctic seasonal carbon dynamics using EC measurements for (a) winter (Jan to Mar), (b) spring (May and Jun), and (c) fall (Sep and Oct). Blue denotes tundra region and green denotes boreal regions. Insets show the sensitivity of NEP (gC m-2d-1) to temperature (K), and soil moisture (ESA CCI) anomalies for SMAP L4C simulation (blue) and ACI ensemble (green).Fig 4. Seasonal carbon cycle anomaly across the ABoVE domain for a) NEP (NEP = GPP - ER); b) satellite based observations of ecosystem productivity represented by GPP from SMAP L4C product, and solar-induced chlorophyll fluorescence (SIF) from ESA GOME-2. Anomaly calculated as the difference between warm spring and baseline conditions. Shading denotes 1 spatial SD from the regional monthly means within the domain.To answer question #1: compare warm spring years (average for 2015/16) to baseline (2010-2014) conditions using Eddy Covariance (EC) measurements, NASA SMAP (Soil Moisture Active Passive) Level 4 Carbon (L4C) product, and regional-scale aggregations (using Ensemble Atmospheric CO2 inversions (ACIs), TRENDY ensemble, and L4C simulations).MethodsEnhanced spring CO2 uptake was partially offset by greater winter respiration loss during anomalous warm winter to spring transition, resulting in near-neutral annual net CO2 balance (Fig 3). Seasonal compensation mechanism different for productivity and net ecosystem carbon exchange, implying importance of respiration in mediating productivity and carbon source/sink activity in the boreal-Arctic (Fig 4). Air temperature has dominant influence on net CO2 exchange in spring and winter, while soil moisture has a dominant control on net CO2 exchange in the fall (Fig 5). Net CO2 exchange in boreal forest is more moisture limited than in Arctic tundra (Fig 5 and 6). To answer question #2: compare regional monthly anomaly between net carbon uptake estimates (ACIs, TRENDY ensemble, SMAP L4C) and productivity indicators (SMAP L4C GPP and GOME-2 SIF). To answer question #3: estimate temperature sensitivity (γ: gC m-2 d-1 K-1), and soil moisture sensitivity (θ: : gC m-2 d-1 %-1) using EC measurements. Results and Discussion