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1. Nutrients and temperature additively increase stream microbial respiration

   https://doi.org/10.1111/gcb.13906  

   Manning, David W.; Rosemond, Amy D.; Gulis, Vladislav; Benstead, Jonathan P.; Kominoski, John S. (January 2018, Global Change Biology)
2. Physical and stoichiometric controls on stream respiration in a headwater stream

   https://doi.org/10.5194/bg-20-3353-2023  

   Dorley, Jancoba; Singley, Joel; Covino, Tim; Singha, Kamini; Gooseff, Michael; Van Horn, David; González-Pinzón, Ricardo (January 2023, Biogeosciences)

   Abstract. Many studies in ecohydrology focusing on hydrologictransport argue that longer residence times across a stream ecosystem shouldconsistently result in higher biological uptake of carbon, nutrients, andoxygen. This consideration does not incorporate the potential forbiologically mediated reactions to be limited by stoichiometric imbalances.Based on the relevance and co-dependences between hydrologic exchange,stoichiometry, and biological uptake and acknowledging the limited amountof field studies available to determine their net effects on the retentionand export of resources, we quantified how microbial respiration iscontrolled by the interactions between and the supply of essential nutrients (C, N, and P)in a headwater stream in Colorado, USA. For this, we conducted two rounds ofnutrient experiments, each consisting of four sets of continuous injectionsof Cl− as a conservative tracer, resazurin as a proxy for aerobicrespiration, and one of the following nutrient treatments: (a) N, (b) N+C,(c) N+P, or (d) C+N+P. Nutrient treatments were considered to be knownsystem modifications that alter metabolism, and statistical tests helpedidentify the relationships between reach-scale hydrologic transport andrespiration metrics. We found that as discharge changed significantlybetween rounds and across stoichiometric treatments, (a) transient storagemainly occurred in pools lateral to the main channel and was proportional todischarge, and (b) microbial respiration remained similar between rounds andacross stoichiometric treatments. Our results contradict the notion thathydrologic transport alone is a dominant control on biogeochemicalprocessing and suggest that complex interactions between hydrology, resourcesupply, and biological community function are responsible for drivingin-stream respiration. 

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3. Thermal acclimation dampens the warming-induced increase in ecosystem respiration

   https://doi.org/10.21203/rs.3.rs-5718150/v1  

   Wang, Junna; Reed, David; Classen, Aimee; Knohl, Alexander; Varlagin, Andrej; Ouimette, Andrew; Desai, Ankur; Heinesch, Bernard; Hanson, Chad; Gough, Christopher; et al (January 2025, Research Square)

   na (Ed.)

   Abstract Global warming increases ecosystem respiration (ER), creating a positive carbon-climate feedback. Thermal acclimation, the direct responses of biological communities to reduce the effects of temperature changes on respiration rates, is a critical mechanism that compensates for warming-induced ER increases and dampens this positive feedback. However, the extent and effects of this mechanism across diverse ecosystems remain unclear. By analyzing CO2 flux data from 93 eddy covariance sites worldwide, we observed thermal acclimation at 84 % of the sites. If sustained, thermal acclimation could reduce projected warming-induced nighttime ER increases by at least 25 % across most climate zones by 2041-2060. Strong thermal acclimation is particularly evident in ecosystems at high elevation, with low-carbon-content soils, and within tundra, semi-arid, and warm-summer Mediterranean climates, supporting the hypothesis that extreme environments favor the evolution of greater acclimation potential. Moreover, ecosystems with dense vegetation and high productivity such as humid tropical and subtropical forests generally exhibit strong thermal acclimation, suggesting that regions with substantial CO2 uptake may continue to serve as strong carbon sinks. Conversely, some ecosystems in cold continental climates show signs of enhancing thermal responses, the opposite of thermal acclimation, which could exacerbate carbon losses as climate warms. Our study underscores the widespread yet climate-specific patterns of thermal acclimation in global terrestrial ER, emphasizing the need to incorporate these patterns into Earth System Models for more accurate carbon-climate feedback projections. 

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4. Experimental warming and drying increase older carbon contributions to soil respiration in lowland tropical forests

   https://doi.org/10.1038/s41467-024-51422-6  

   McFarlane, Karis J; Cusack, Daniela F; Dietterich, Lee H; Hedgpeth, Alexandra L; Finstad, Kari M; Nottingham, Andrew T (December 2024, Nature Communications)

   Abstract Tropical forests account for over 50% of the global terrestrial carbon sink, but climate change threatens to alter the carbon balance of these ecosystems. We show that warming and drying of tropical forest soils may increase soil carbon vulnerability, by increasing degradation of older carbon. In situ whole-profile heating by 4 °C and 50% throughfall exclusion each increased the average radiocarbon age of soil CO₂efflux by ~2–3 years, but the mechanisms underlying this shift differed. Warming accelerated decomposition of older carbon as increased CO₂emissions depleted newer carbon. Drying suppressed decomposition of newer carbon inputs and decreased soil CO₂emissions, thereby increasing contributions of older carbon to CO₂efflux. These findings imply that both warming and drying, by accelerating the loss of older soil carbon or reducing the incorporation of fresh carbon inputs, will exacerbate soil carbon losses and negatively impact carbon storage in tropical forests under climate change. 

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5. Copepod respiration increases by 7% per °C increase in temperature: A meta‐analysis

   https://doi.org/10.1002/lol2.10106  

   Heine, Kyle B.; Abebe, Ash; Wilson, Alan E.; Hood, Wendy R. (June 2019, Limnology and Oceanography Letters)