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1. Thermal niche variation among individuals of the poison frog, Oophaga pumilio , in forest and converted habitats

   https://doi.org/10.1111/btp.12691  

   Rivera‐Ordonez, Juana M. ; Justin Nowakowski, A. ; Manansala, Adrian ; Thompson, Michelle E. ; Todd, Brian D. ( August 2019 , Biotropica)

   The conversion of natural habitats to human land uses often increases local temperatures, creating novel thermal environments for species. The variable responses of ectotherms to habitat conversion, where some species decline while others persist, can partly be explained by variation among species in their thermal niches. However, few studies have examined thermal niche variation within species and across forest‐land use ecotones, information that could provide clues about the capacity of species to adapt to changing temperatures. Here, we quantify individual‐level variation in thermal traits of the tropical poison frog,Oophaga pumilio, in thermally contrasting habitats. Specifically, we examined local environmental temperatures, field body temperatures (T_b), preferred body temperatures (T_pref), critical thermal maxima (CT_max), and thermal safety margins (TSM) of individuals from warm, converted habitats and cool forests. We found that frogs from converted habitats exhibited greater meanT_bandT_prefthan those from forests. In contrast,CT_maxandTSMdid not differ significantly between habitats. However,CT_maxdid increase moderately with increasingT_b, suggesting that changes inCT_maxmay be driven by microscale temperature exposure within habitats rather than by mean habitat conditions. AlthoughO. pumilioexhibited moderate divergence inT_pref,CT_maxappears to be less labile between habitats, possibly due to the ability of frogs in converted habitats to maintain theirT_bbelow air temperatures that reach or exceedCT_max. Selective pressures on thermal tolerances may increase, however, with the loss of buffering microhabitats and increased frequency of extreme temperatures expected under future habitat degradation and climate warming.

   Abstract in Spanish is available with online material.

    

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2. Increased resource use efficiency amplifies positive response of aquatic primary production to experimental warming

   https://doi.org/10.1111/gcb.13912  

   Hood, James M. ; Benstead, Jonathan P. ; Cross, Wyatt F. ; Huryn, Alexander D. ; Johnson, Philip W. ; Gíslason, Gísli M. ; Junker, James R. ; Nelson, Daniel ; Ólafsson, Jón S. ; Tran, Chau ( October 2017 , Global Change Biology)

   Climate warming is affecting the structure and function of river ecosystems, including their role in transforming and transporting carbon (C), nitrogen (N), and phosphorus (P). Predicting how river ecosystems respond to warming has been hindered by a dearth of information about how otherwise well‐studied physiological responses to temperature scale from organismal to ecosystem levels. We conducted an ecosystem‐level temperature manipulation to quantify how coupling of stream ecosystem metabolism and nutrient uptake responded to a realistic warming scenario. A ~3.3°C increase in mean water temperature altered coupling of C, N, and P fluxes in ways inconsistent with single‐species laboratory experiments. Net primary production tripled during the year of experimental warming, while whole‐stream N and P uptake rates did not change, resulting in 289% and 281% increases in autotrophic dissolved inorganic N and P use efficiency (UE), respectively. Increased ecosystem production was a product of unexpectedly large increases in mass‐specific net primary production and autotroph biomass, supported by (i) combined increases in resource availability (via N mineralization and N₂fixation) and (ii) elevated resource use efficiency, the latter associated with changes in community structure. These large changes in C and nutrient cycling could not have been predicted from the physiological effects of temperature alone. Our experiment provides clear ecosystem‐level evidence that warming can shift the balance between C and nutrient cycling in rivers, demonstrating that warming will alter the important role of in‐stream processes in C, N, and P transformations. Moreover, our results reveal a key role for nutrient supply and use efficiency in mediating responses of primary producers to climate warming.

    

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3. Drought timing and local climate determine the sensitivity of eastern temperate forests to drought

   https://doi.org/10.1111/gcb.14096  

   D'Orangeville, Loïc ; Maxwell, Justin ; Kneeshaw, Daniel ; Pederson, Neil ; Duchesne, Louis ; Logan, Travis ; Houle, Daniel ; Arseneault, Dominique ; Beier, Colin M. ; Bishop, Daniel A. ; et al ( March 2018 , Global Change Biology)

   Projected changes in temperature and drought regime are likely to reduce carbon (C) storage in forests, thereby amplifying rates of climate change. While such reductions are often presumed to be greatest in semi‐arid forests that experience widespread tree mortality, the consequences of drought may also be important in temperate mesic forests of Eastern North America (ENA) if tree growth is significantly curtailed by drought. Investigations of the environmental conditions that determine drought sensitivity are critically needed to accurately predict ecosystem feedbacks to climate change. We matched site factors with the growth responses to drought of 10,753 trees across mesic forests ofENA, representing 24 species and 346 stands, to determine the broad‐scale drivers of drought sensitivity for the dominant trees inENA. Here we show that two factors—the timing of drought, and the atmospheric demand for water (i.e., local potential evapotranspiration;PET)—are stronger drivers of drought sensitivity than soil and stand characteristics. Drought‐induced reductions in tree growth were greatest when the droughts occurred during early‐season peaks in radial growth, especially for trees growing in the warmest, driest regions (i.e., highestPET). Further, mean species trait values (rooting depth and ψ₅₀) were poor predictors of drought sensitivity, as intraspecific variation in sensitivity was equal to or greater than interspecific variation in 17 of 24 species. From a general circulation model ensemble, we find that future increases in early‐seasonPETmay exacerbate these effects, and potentially offset gains in C uptake and storage inENAowing to other global change factors.

    

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4. Evidence for divergence of response in Indica , Japonica , and wild rice to high CO 2 × temperature interaction

   https://doi.org/10.1111/gcb.13279  

   Wang, Diane R. ; Bunce, James A. ; Tomecek, Martha B. ; Gealy, David ; McClung, Anna ; McCouch, Susan R. ; Ziska, Lewis H. ( April 2016 , Global Change Biology)

   HighCO₂and high temperature have an antagonistic interaction effect on rice yield potential and present a unique challenge to adapting rice to projected future climates. Understanding how the differences in response to these two abiotic variables are partitioned across rice germplasm accessions may be key to identifying potentially useful sources of resilient alleles for adapting rice to climate change. In this study, we evaluated eleven globally diverse rice accessions under controlled conditions at two carbon dioxide concentrations (400 and 600 ppm) and four temperature environments (29 °C day/21 °C night; 29 °C day/21 °C night with additional heat stress at anthesis; 34 °C day/26 °C night; and 34 °C day/26 °C night with additional heat stress at anthesis) for a suite of traits including five yield components, five growth characteristics, one phenological trait, and four photosynthesis‐related measurements. Multivariate analyses of mean trait data from these eight treatments divide our rice panel into two primary groups consistent with the genetic classification ofINDICA/INDICA‐like andJAPONICApopulations. Overall, we find that the productivity of plants grown under elevated [CO₂] was more sensitive (negative response) to high temperature stress compared with that of plants grown under ambient [CO₂] across this diversity panel. We report differential response toCO₂× temperature interaction forINDICA/INDICA‐like andJAPONICArice accessions and find preliminary evidence for the beneficial introduction of exotic alleles into cultivated rice genomic background. Overall, these results support the idea of using wild or currently unadapted gene pools in rice to enhance breeding efforts to secure future climate change adaptation.

    

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5. The influence of rising tropospheric carbon dioxide and ozone on plant productivity

   https://doi.org/10.1111/plb.12973  

   Ainsworth, E. A. ; Lemonnier, P. ; Wedow, J. M. ; Tausz‐Posch, ed., S. ( March 2019 , Plant Biology)

   Human activities result in a wide array of pollutants being released to the atmosphere. A number of these pollutants have direct effects on plants, including carbon dioxide (CO₂), which is the substrate for photosynthesis, and ozone (O₃), a damaging oxidant. How plants respond to changes in these atmospheric air pollutants, both directly and indirectly, feeds back on atmospheric composition and climate, global net primary productivity and ecosystem service provisioning. Here we discuss the past, current and future trends in emissions ofCO₂and O₃and synthesise the current atmosphericCO₂and O₃budgets, describing the important role of vegetation in determining the atmospheric burden of those pollutants. While increased atmosphericCO₂concentration over the past 150 years has been accompanied by greaterCO₂assimilation and storage in terrestrial ecosystems, there is evidence that rising temperatures and increased drought stress may limit the ability of future terrestrial ecosystems to buffer against atmospheric emissions. Long‐term Free AirCO₂or O₃Enrichment (FACE) experiments provide critical experimentation about the effects of futureCO₂and O₃on ecosystems, and highlight the important interactive effects of temperature, nutrients and water supply in determining ecosystem responses to air pollution. Long‐term experimentation in both natural and cropping systems is needed to provide critical empirical data for modelling the effects of air pollutants on plant productivity in the decades to come.

    

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