More Like this

1. Assessing trait‐based scaling theory in tropical forests spanning a broad temperature gradient

   https://doi.org/10.1111/geb.12645  

   Enquist, Brian J. ; Bentley, Lisa Patrick ; Shenkin, Alexander ; Maitner, Brian ; Savage, Van ; Michaletz, Sean ; Blonder, Benjamin ; Buzzard, Vanessa ; Espinoza, Tatiana Erika Boza ; Farfan‐Rios, William ; et al ( October 2017 , Global Ecology and Biogeography)

   Tropical elevation gradients are natural laboratories to assess how changing climate can influence tropical forests. However, there is a need for theory and integrated data collection to scale from traits to ecosystems. We assess predictions of a novel trait‐based scaling theory, including whether observed shifts in forest traits across a broad tropical temperature gradient are consistent with local phenotypic optima and adaptive compensation for temperature.

   An elevation gradient spanning 3,300 m and consisting of thousands of tropical tree trait measures taken from 16 1‐ha tropical forest plots in southern Perú, where gross and net primary productivity (GPP and NPP) were measured.

   April to November 2013.

   Plants; tropical trees.

   We developed theory to scale from traits to communities and ecosystems and tested several predictions. We assessed the covariation between climate, traits, biomass and GPP and NPP. We measured multiple traits linked to variation in tree growth and assessed their frequency distributions within and across the elevation gradient. We paired these trait measures across individuals within 16 forests with simultaneous measures of ecosystem net and gross primary productivity.

   Consistent with theory, variation in forest NPP and GPP primarily scaled with forest biomass, but the secondary effect of temperature on productivity was much less than expected. This weak temperature dependence appears to reflect directional shifts in several mean community traits that underlie tree growth with decreases in site temperature.

   The observed shift in traits of trees that dominate in more cold environments is consistent with an ‘adaptive/acclimatory’ compensation for the kinetic effects of temperature on leaf photosynthesis and tree growth. Forest trait distributions across the gradient showed overly peaked and skewed distributions, consistent with the importance of local filtering of optimal growth traits and recent shifts in species composition and dominance attributable to warming from climate change. Trait‐based scaling theory provides a basis to predict how shifts in climate have and will influence the trait composition and ecosystem functioning of tropical forests.

    

   more » « less
2. Ecophysiological Responses of the Intertidal Seaweed Fucus Distichus to Temperature Changes and Reduced Light Driven by Tides and Glacial Input

   https://doi.org/10.1007/s12237-023-01207-9  

   Umanzor, Schery ; Sandoval-Gil, Jose Miguel ; Conitz, Jan ( July 2023 , Estuaries and Coasts)

   Abstract Climate change is influencing the performance and distribution of macroalgae in the marine environment. Although intertidal seaweeds successfully adapt to extreme and rapid abiotic changes, exposure to persistent or prolonged potentially stressful conditions can affect their vitality and productivity. Rapid glacial melt can severely alter seawater physicochemical characteristics for shallow and intertidal seaweed communities on the Alaskan coasts. Understanding how intertidal macroalgae respond to this complex mosaic of stressors is key to assessing their ability to adapt to a climate change scenario. This study assessed whether specific stress responses and acclimation mechanisms were exhibited by the intertidal brown seaweed Fucus distichus subsp. evanescence may enable it to cope with changing temperatures and reduced light availability linked to tides and glacial inputs. We analyzed its physiological performance, including photobiological variables, nutrient content, nitrate uptake, and oxidative stress descriptors under strictly controlled laboratory conditions. Results show that this subspecies of Fucus distichus may be relatively unaffected by changes in light and temperature driven by glacial melt due to the presence of pre-adapted strategies that collectively express wide physiological tolerances. Outcomes provide insights into some of the mechanisms of stress tolerance of this major structuring seaweed across the Alaskan coast. Nonetheless, glacial melt would also lower salinity in coastal water, potentially resulting in osmotic stress and other physiological effects not explored here. 

   more » « less
3. Economic carbon cycle feedbacks may offset additional warming from natural feedbacks

   https://doi.org/10.1073/pnas.1805187115  

   Woodard, Dawn L. ; Davis, Steven J. ; Randerson, James T. ( December 2018 , Proceedings of the National Academy of Sciences)

   As the Earth warms, carbon sinks on land and in the ocean will weaken, thereby increasing the rate of warming. Although natural mechanisms contributing to this positive climate–carbon feedback have been evaluated using Earth system models, analogous feedbacks involving human activities have not been systematically quantified. Here we conceptualize and estimate the magnitude of several economic mechanisms that generate a carbon–climate feedback, using the Kaya identity to separate a net economic feedback into components associated with population, GDP, heating and cooling, and the carbon intensity of energy production and transportation. We find that climate-driven decreases in economic activity (GDP) may in turn decrease human energy use and thus fossil fuel CO₂emissions. In a high radiative forcing scenario, such decreases in economic activity reduce fossil fuel emissions by 13% this century, lowering atmospheric CO₂by over 100 ppm in 2100. The natural carbon–climate feedback, in contrast, increases atmospheric CO₂over this period by a similar amount, and thus, the net effect including both feedbacks is nearly zero. Our work highlights the importance of improving the representation of climate–economic feedbacks in scenarios of future change. Although the effects of climate warming on the economy may offset weakening land and ocean carbon sinks, a loss of economic productivity will have high societal costs, potentially increasing wealth inequity and limiting resources available for effective adaptation.

    

   more » « less
4. Phenotypic adaptation to temperature in the mosquito vector, Aedes aegypti

   https://doi.org/10.1111/gcb.17041  

   Dennington, Nina L. ; Grossman, Marissa K. ; Ware‐Gilmore, Fhallon ; Teeple, Janet L. ; Johnson, Leah R. ; Shocket, Marta S. ; McGraw, Elizabeth A. ; Thomas, Matthew B. ( November 2023 , Global Change Biology)

   Most models exploring the effects of climate change on mosquito‐borne disease ignore thermal adaptation. However, if local adaptation leads to changes in mosquito thermal responses, “one size fits all” models could fail to capture current variation between populations and future adaptive responses to changes in temperature. Here, we assess phenotypic adaptation to temperature inAedes aegypti, the primary vector of dengue, Zika, and chikungunya viruses. First, to explore whether there is any difference in existing thermal response of mosquitoes between populations, we used a thermal knockdown assay to examine five populations ofAe. aegypticollected from climatically diverse locations in Mexico, together with a long‐standing laboratory strain. We identified significant phenotypic variation in thermal tolerance between populations. Next, to explore whether such variation can be generated by differences in temperature, we conducted an experimental passage study by establishing six replicate lines from a single field‐derived population ofAe. aegyptifrom Mexico, maintaining half at 27°C and the other half at 31°C. After 10 generations, we found a significant difference in mosquito performance, with the lines maintained under elevated temperatures showing greater thermal tolerance. Moreover, these differences in thermal tolerance translated to shifts in the thermal performance curves for multiple life‐history traits, leading to differences in overall fitness. Together, these novel findings provide compelling evidence thatAe. aegyptipopulations can and do differ in thermal response, suggesting that simplified thermal performance models might be insufficient for predicting the effects of climate on vector‐borne disease transmission.

    

   more » « less
5. The Duality of Reforestation Impacts on Surface and Air Temperature

   https://doi.org/10.1029/2019JG005543  

   Novick, Kimberly A. ; Katul, Gabriel G. ( March 2020 , Journal of Geophysical Research: Biogeosciences)

   Evidence is mounting that temperate‐zone reforestation cools surface temperature (T_surf), mitigating deleterious effects of climate warming. WhileT_surfdrives many biophysical processes, air temperature (T_a) is an equally important target for climate mitigation and adaptation. Whether reductions inT_surftranslate to reductions inT_aremains complex, fraught by several nonlinear and intertwined processes. In particular, forest canopy structure strongly affects near‐surface temperature gradients, complicating cross‐site comparison. Here the influence of reforestation onT_ais assessed by targeting temperature metrics that are less sensitive to local canopy effects. Specifically, we consider the aerodynamic temperature (T_aero), estimated using a novel procedure that does not rely on the assumptions of Monin‐Obukhov similarity theory, as well as the extrapolated temperature into the surface layer (T_extrap). The approach is tested with flux tower data from a grass field, pine plantation, and mature hardwood stand co‐located in the Duke Forest (North Carolina, USA). During growing season daytime periods,T_surfis 4–6 °C cooler, andT_aeroand near‐surfaceT_extrapare 2–3 °C cooler, in the forests relative to the grassland. During the dormant season, daytime differences are smaller but still substantial. At night, differences inT_aeroare small, and near‐surfaceT_extrapis warmer over forests than grasslands during the growing season (by 0.5 to 1 °C). Finally, the influence of land cover onT_extrapat the interface between the surface and mixed layer is small. Overall, reforestation appears to provide a meaningful opportunity for adaption to warmer daytimeT_ain the southeastern United States, especially during the growing season.

    

   more » « less