Experimental Warming Research Articles

Life-history adaptation under climate warming magnifies the agricultural footprint of a cosmopolitan insect pest

Climate change is affecting population growth rates of ectothermic pests with potentially dire consequences for agriculture and global food security. However, current projection models of pest impact typically overlook the potential for rapid genetic adaptation, making current forecasts uncertain. Here, we predict how climate change adaptation in life-history traits of insect pests affects their growth rates and impact on agricultural yields by unifying thermodynamics with classic theory on resource acquisition and allocation trade-offs between foraging, reproduction, and maintenance. Our model predicts that warming temperatures will favour resource allocation towards maintenance coupled with increased resource acquisition through larval foraging, and the evolution of this life-history strategy results in both increased population growth rates and per capita host consumption, causing a double-blow on agricultural yields. We find support for these predictions by studying thermal adaptation in life-history traits and gene expression in the wide-spread insect pest, Callosobruchus maculatus; with 5 years of evolution under experimental warming causing an almost two-fold increase in its predicted agricultural footprint. These results show that pest adaptation can offset current projections of agricultural impact and emphasize the need for integrating a mechanistic understanding of life-history evolution into forecasts of pest impact under climate change.

Effect of Experimental Warming on Forage Nutritive Value and Storage in Alpine Meadows at Three Different Altitudes of Nianqing Tanggula Mountain, Northern Tibet: A Long-Term Experience

Effects of climate warming on nutrition quality and storage of alpine grasslands are still controversial, which is not conducive to the management and utilization of alpine grasslands. A long-term warming experiment (with open-top chambers used to elevate temperature) was conducted at three elevations (relatively low, mid-, and high elevations with 4313, 4513, and 4693 m) of Northern Tibet in 2010 to compare the differences in forage nutritional quality and storage response to warming among three elevations and to explore the relationships between forage nutritional quality and production. In 2019, community surveys, observations of forage biomass and nutrition quality, and soil physicochemical properties were carried out. Forage nutrition quality included crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), ether extract (EE), crude ash (Ash), and water-soluble carbohydrate (WSC) content. Warming did not affect community aboveground biomass (AGB) at the three elevations. Warming improved community nutrition quality by increasing community CP content by 25.80% and decreasing community NDF content by 15.51% at the low elevation. In contrast, warming reduced community nutrition quality by increasing community CP, ADF, and NDF contents by 13.45%, 23.68%, and 17.43%, respectively, and decreasing Ash content by 39.50% at the high elevation. Warming did not affect community CP, ADF, NDF, EE, Ash, or WSC contents at the mid-elevation. Warming increased community nutrition storage by increasing community CP, ADF, and NDF storges by 74.69%, 88.18%, and 79.71%, respectively, at the high elevation. Warming did not affect community nutrition storages at the low or mid-elevations. Overall, forbs had higher CP, EE, Ash, and WSC contents and lower ADF and NDF contents compared with graminoids. Community EE content increased with community AGB, but community CP, ADF, NDF, EE, Ash, and WSC contents were not related to community AGB. Therefore, from the low to high elevation, the effects of warming on forage nutrition quality gradually changed from improving to inhibiting. Warming altered rangeland quality by affecting forage nutrition quality rather than forage production. There were no trade-offs between forage nutrition quality and forage production.

Attribution of 2022 August Heavy Precipitation Event in South Korea Using High‐Resolution Pseudo Global Warming Simulations: Sensitivity to Vertical Temperature Changes

AbstractThis study examines the anthropogenic influences on the heavy precipitation event that occurred in early August 2022, South Korea, using a pseudo global warming (PGW) method with a convection‐permitting model. Pseudo global warming experiments for counterfactual natural non‐warming conditions (NAT) were conducted by removing anthropogenic warming patterns from the observations. The anthropogenic warming patterns were estimated from the differences between Coupled Model Inter‐comparison Project Phase 6 historical and historical natural‐only simulations. Two NAT experiments were performed by using the multi‐model mean of all nine models (NATT) and the three models with weaker upper tropospheric warming (NATW). The results show that atmospheric moisture is reduced in both NAT experiments compared to the current‐condition experiments, but that enhanced convective instability due to upper tropospheric cooling offsets the effect of moisture reduction, resulting in similar precipitation responses. This compensation effect becomes weak in NATW, indicating the important role of the vertical profile of anthropogenic warming pattern in PGW‐based attribution experiments.

Effects of in situ experimental warming on metabolic expression in a soft sediment bivalve

Ocean surface temperatures and the frequency and intensity of marine heatwaves are increasing worldwide. Understanding how marine organisms respond and adapt to heat pulses and the rapidly changing climate is crucial for predicting responses of valued species and ecosystems to global warming. Here, we carried out an in situ experiment to investigate sublethal responses to heat spikes of a functionally important intertidal bivalve, the venerid clam Austrovenus stutchburyi. We describe changes in metabolic responses under two warming scenarios (five days and seven days) at two sites (muddy and sandy). Tidal flat warming during every low tide for five days affected the abundance of multiple functional metabolites within this species. The metabolic response was related to pathways such as metabolic energetics, amino acid and lipid metabolism, and accumulation of stress-related metabolites. There was some recovery after cooler weather during the final two days of the experiment. The degree of change was greater in muddy versus sandy sediments. Our findings provide new evidence of the metabolomic response of these important bivalve to heat stress, which could be used for resource managers when implementing strategies to mitigate the impacts of climate change on valuable marine resources.

Antagonistic biotic interactions mitigate the positive effects of warming on wood decomposition.

Global change drivers such as habitat fragmentation, species invasion, and climate warming can act synergistically upon native systems; however, global change drivers can be neutralized if they induce antagonistic interactions in ecological communities. Deadwood comprises a considerable portion of forest carbon, and it functions as refuge, nesting habitat and nutrient source for plant, animal and microbial communities. We predicted that thermophilic termites would increase wood decomposition with experimental warming and in forest edge habitat. Alternately, given that predatory ants also are thermophilic, they might limit termite-mediated decomposition regardless of warming. In addition, we predicted that a non-native, putative termite-specialist ant species would decrease termite activity, and consequently decomposition, when replacing native ants. We tested these hypotheses using experimental warming plots (~ 2.5°C above ambient) where termites, and their ant predators, have full access and vary in abundance at microscales. We found that termite activity was the strongest control on decomposition of field wood assays, with mass loss increasing 20% with each doubling of termite activity. However, both native and non-native ant abundance increased with experimental warming and, in turn, appeared to equally limit termite activity and, consequently, reduced wood decomposition rates. As a result, experimental warming had little net effect on the decomposition rates-likely because, although termite activity increased somewhat in warmed plots, ant abundances increased more than five times as much. Our results suggest that, in temperate southern U.S. forests, the negative top-down effects of predatory ants on termites outweighed the potential positive influences of warming on termite-driven wood decomposition rates.

Neighbor effects on population growth rate differ among populations due to variation in demographic rate sensitivities in Sedum lanceolatum

Population growth rates will respond to an environmental driver only if the driver impacts demographic rate(s) and the population is sensitive to impacted demographic rate(s). If populations vary in the sensitivity of population growth rate to demographic rates, the effect of an environmental driver on population growth rate could vary across populations, even if the effect of the driver on demographic rates does not vary across populations. Here, we use five years of demographic data of a common alpine plant, including data from a neighbor removal experiment and a climate warming experiment, to quantify the relative contribution of neighbor effects on demographic rates versus sensitivity of population growth rate to demographic rates to across‐population variation in neighbor effects on population growth rate. We find neighbor effects on population growth rate vary significantly across populations, and this effect is driven primarily by variation in sensitivity of population growth rate to demographic rates across populations. Further, results from our climate warming experiment suggests variation in sensitivity across populations is partly driven by temperature differences. Our results highlight the importance of considering changes in the sensitivity of population growth rate to demographic rates across space, and show how changes in sensitivity can contribute to spatial variation in the effects of a driver on population growth rate.

Decline in diversity of tropical soil fauna under experimental warming.

Climate change is exacerbating a global decline in biodiversity. Numerous observational studies link rising temperatures to declining biological abundance, richness and diversity in terrestrial ecosystems, yet few studies have considered the highly diverse and functionally significant communities of tropical forest soil and leaf litter fauna. Here, we report major declines in the order-level richness and diversity of soil and leaf litter fauna following three years of experimental whole-profile soil warming in a tropical forest. These declines were greatest during the dry season, suggesting that warming effects could be exacerbated by drought. Contrary to findings from higher latitudes, total faunal abundance increased under warming, and these effects were paralleled by major shifts in community composition. These responses were driven by increased dominance of a relatively small number of thermophilic taxa, and of oribatid mites in particular. Our study provides direct experimental evidence that warming causes diversity declines and compositional shifts for tropical forest soil and leaf litter fauna, a result with potential consequences for soil functions and biogeochemical cycles, and that highlights the vulnerability of tropical biodiversity to climate change.

The Response of Tropopause-Overshooting Convection over North America to Climate Change

Abstract Recent field campaigns, observational studies, and modeling work have demonstrated that extratropical tropopause-overshooting convection has a substantial and previously underestimated impact on stratospheric water vapor concentrations. This necessitates improved understanding of how tropopause-overshooting convection will respond to a warming climate. A growing body of research indicates that environments conducive to severe thunderstorms will occur more often and be increasingly unstable in the future, but no study has examined how this may be related to increased overshooting. To rectify this, this study leverages an existing pseudo–global warming (PGW) experiment to evaluate potential future changes in tropopause-overshooting convection over North America. We examine two 10-yr simulations consisting of 1) a retrospective period (2003–12) forced by ERA-Interim initial and boundary conditions (the control simulation) and 2) the same retrospective period with CMIP5 ensemble-mean high-end emission scenario climate changes added to the initial and boundary conditions (the PGW simulation). Tropopause-overshooting convection in the control simulation is validated against observed overshoots from both ground-based radar observations in the United States and GOES observations over North America. The model is shown to effectively simulate the observed regional distribution, annual cycle, and diurnal cycle of tropopause-overshooting convection. In the PGW simulation, tropopause-overshooting convection is found to increase more than 250% across the model domain, and the projected seasonal period of frequent tropopause-overshooting convection is shown to extend into late summer. Additionally, tropopause-overshooting convection with extreme tropopause-relative heights (>4 km) is more frequent in a warmed climate scenario.

Heating up the roof of the world: tracing the impacts of in-situ warming on carbon cycle in alpine grasslands on the tibetan plateau

Abstract Climate warming may induce substantial changes in ecosystem carbon cycle, particularly for those climate-sensitive regions, such as alpine grasslands on the Tibetan Plateau. By synthesizing findings from in-situ warming experiments, this review elucidates the mechanisms underlying the impacts of experimental warming on carbon cycle dynamics within these ecosystems. Generally, alterations in vegetation structure and prolonged growing season favor strategies for enhanced ecosystem carbon sequestration under warming conditions. Whilst warming modifies soil microbial communities and their carbon-related functions, its effects on soil carbon release fall behind the increased vegetation carbon uptake. Despite no significant accumulation of soil carbon stock has been detected upon warming, notable changes in its fractions indicate potential shifts in carbon stability. Future studies should prioritize deep soil carbon dynamics, the interactions of carbon, nitrogen, and phosphorus cycles under warming scenarios, and the underlying biological mechanisms behind these responses. Furthermore, the integration of long-term warming experiments with Earth system models is essential for reducing the uncertainties of model predictions regarding future carbon-climate feedback in these climate-sensitive ecosystems.

A Test of Functional Balance Theory for Wetland Biomass Allocation in a Global Change Experiment

AbstractForecasts of root growth and carbon sequestration under global change are compromised by uncertainty in how plants will allocate biomass between above and belowground pools. Here, we develop a simple model to assess whether functional balance theory can explain a complex biomass allocation response observed in a brackish marsh under experimental warming and elevated CO2. Our model shows how treatment‐driven changes in nitrogen supply and demand can explain divergent observations of root growth (i.e., maximum responses under intermediate warming and elevated CO2). The model also reveals a surprising interaction between warming and eutrophication, where enhanced N loading to coastal marshes may reduce adverse impacts of warming on root growth. Our findings provide a mechanistic basis for incorporating biomass allocation into forecast models of marsh evolution. They also provide a general example of using ecological theory to decompose complex net responses observed in multi‐factor global change experiments into constituent processes.

Colonization and extinction lags drive non‐linear responses to warming in mountain plant communities across the Northern Hemisphere

Global warming is changing plant communities due to the arrival of new species from warmer regions and declining abundance of cold‐adapted species. However, experimentally testing predictions about trajectories and rates of community change is challenging because we normally lack an expectation for future community composition, and most warming experiments fail to incorporate colonization by novel species. To address these issues, we analyzed data from 44 whole‐community transplant experiments along 22 elevational gradients across the Northern Hemisphere. In these experiments, high‐elevation communities were transplanted to lower elevations to simulate warming, while also removing dispersal barriers for lower‐elevation species to establish. We quantified the extent and pace at which warmed high‐elevation communities shifted towards the taxonomic composition of lower elevation communities. High‐elevation plant communities converged towards the composition of low‐elevation communities, with higher rates under stronger experimental warming. Strong community shifts occurred in the first year after transplantation then slowed over time, such that communities remained distinct from both origin and destination control by the end of the experimental periods (3‐9 years). Changes were driven to a similar extent by both new species colonization and abundance shifts of high‐elevation species, but with substantial variation across experiments that could be partly explained by the magnitude and duration of experimental warming, plot size and functional traits. Our macroecological approach reveals that while warmed high‐elevation communities increasingly resemble communities at lower elevations today, the slow pace of taxonomic shifts implies considerable colonization and extinction lags, where a novel taxonomic composition of both low‐ and high‐elevation species could coexist for long periods of time. The important contribution of the colonizing species to community change also indicates that once dispersal barriers are overcome, warmed high‐elevation communities are vulnerable to encroachment from lower elevation species.

Spatial and temporal variations in respiration rates under experimental warming in alpine meadows of Gangotri National Park, Western Himalaya

The Indian Himalayan region is highly vulnerable to climate warming, which might impact ecological processes and carbon fluxes. Soil respiration (SR), primary component of Ecosystem respiration (ER), is the largest carbon efflux. Despite this, impacts of warming on diurnal respiration rates in alpine meadows of the Indian Himalayan Region remains unexplored. With an emphasis on diurnal patterns, we investigated the spatial and temporal variations in respiration rates under experimental warming in the alpine meadows of Gangotri National Park, Western Himalaya using 18 Open Top Chambers (OTCs) across three sites during May to September 2023. Significant impacts of experimental warming on diurnal SR and ER were observed, with varied site-specific responses. Peak respiration occurred around 12:00 h, followed by a decline in the evening. In both experimental warming and ambient control conditions, ER showed a positive relationship with soil temperature (ST) and a negative relationship with soil water content (SWC). Notably, ant activity was observed as a contributing factor to increased SR in certain plots, highlighting the role of biotic interactions in soil respiration dynamics. We used linear mixed-effects models to assess the contributions of various microclimatic factors to respiration rates. Microclimatic parameters explained about 4.4% and 8% of the variability in SR and ER respectively, which jumped to 85.3% and 85.7% when including spatio-temporal variations. These findings underscore the critical importance of considering spatio-temporal variability and biotic interactions when assessing the influence of microclimatic factors on respiration dynamics in alpine ecosystems. The substantial increase in explanatory power when considering these variations highlights the complex interactions between environmental heterogeneity and ecological processes. This study provides valuable insights into the ecological impacts of climate change in the Indian Himalayan region, demonstrating that experimental warming resulting in a 1.7 °C increase in overall air temperature significantly alters respiration dynamics, thereby emphasizing the urgent need to further investigate the resilience of these alpine meadow ecosystems under changing climatic conditions.

Photosynthetic Responses of Peat Moss (Sphagnum spp.) and Bog Cranberry (Vaccinium oxycoccos L.) to Spring Warming.

The rising global temperature makes understanding the impact of warming on plant physiology in critical ecosystems essential, as changes in plant physiology can either help mitigate or intensify climate change. The northern peatlands belong to the most important parts of the global carbon cycle. Therefore, knowledge of the ongoing and future climate change impacts on peatland vegetation photosynthesis is crucial for further refinement of peatland or global carbon cycle and vegetation models. As peat moss (Sphagnum spp.) and bog cranberry (Vaccinium oxycoccos L.) represent some of the most common plant functional groups of peatland vegetation, we examined the impact of experimental warming on the status of their photosynthetic apparatus during the early vegetation season. We also studied the differences in the winter to early spring transition of peat moss and bog cranberry photosynthetic activity. We have shown that peat moss starts photosynthetic activity earlier because it relies on light-dependent energy dissipation through the winter. However, bog cranberry needs a period of warmer temperature to reach full activity due to the sustained, non-regulated, heat dissipation during winter, as suggested by the doubling of photosystem II efficiency and 36% decrease in sustained heat dissipation between the mid-March and beginning of May. The experimental warming further enhanced the performance of photosystem II, indicated by a significant increase in the photosystem II performance index on an absorption basis due to warming. Therefore, our results suggest that bog cranberry can benefit more from early spring warming, as its activity is sped up more compared to peat moss. This will probably result in faster shrub encroachment of the peatlands in the warmer future. The vegetation and carbon models should take into account the results of this research to predict the peatland functions under changing climate conditions.

Indirect effects of warming via phenology on reproductive success of alpine plants

Abstract Climate warming has induced pronounced shifts in the phenology of alpine plants worldwide, yet the impact of these changes on plant reproduction remains unclear, although phenology plays a vital role in reproduction. Based on a 7‐year field warming and altered precipitation experiment initiated in 2017, we measured three reproductive phenological events and seven reproductive traits of six dominant species, belonging to two flowering functional groups, to assess the effects of climate change on reproductive phenology and the reproductive consequence of changing the phenology in an alpine meadow on the eastern Tibetan Plateau from 2021 to 2023. Warming significantly advanced the start of flowering in early‐spring flowering (ESF) and mid‐summer flowering (MSF) plants, while the fruiting period of ESF plants remained stable. Furthermore, warming led to a decrease in the number of seeds and productivity of alpine plants, while seed size remained stable. Phenological changes regulate the reproductive success of alpine plants. Specifically, the start of flowering for ESF plants and the start of fruiting for MSF plants regulated the number of seeds and productivity of the two flowering functional groups, respectively. The increase in phenological niche overlap and intensification of interspecific competition, caused by different phenological responses of the flowering functional groups to warming, also are key factors contributing to the decline in seed production of alpine plants. Synthesis. These results demonstrate that the reproductive success of alpine plants would be decreased by earlier reproduction under climate warming, and alpine plants tend to maintain stable seed size in response to climate change. Our study emphasizes the important regulatory and indicative role of reproductive phenology in the sexual reproduction of alpine plants under future climate change.

Soil microfauna mediate multifunctionality under multilevel warming in a primary forest.

Soil microfauna play a crucial role in maintaining multiple functions associated with soil phosphorous, nitrogen and carbon cycling. Although both soil microfauna diversity and multifunctionality are strongly affected by climate warming, it remains unclear how their relationships respond to different levels of warming. We conducted a 3-year multilevel warming experiment with five warming treatments in a subtropical primary forest. Using infrared heating systems, the soil surface temperature in plots was maintained at 0.8, 1.5, 3.0 and 4.2°C above ambient temperature (control). Our findings indicated that low-level warming (+0.8-1.5°C) increased soil multifunctionality, as well as nematode and protist diversity, compared with the control. In contrast, high-level warming (+4.2°C) significantly reduced these variables. We also identified significant positive correlations between soil multifunctionality and nematode and protist diversity in the 0-10 cm soil layer. Notably, we found that soil multifunctionality and protist diversity did not change significantly under 3.0°C warming treatment. Our results imply that a temperature increase of around 3°C may represent a critical threshold in subtropical forests, which is of great importance for identifying response measures to global warming from the perspective of microfauna in the surface soil. Our findings provide new evidence on how soil microfauna regulate multifunctionality under varying degrees of warming in primary forests.

A Dynamical Interpretation of the Intensification of the Winter North Atlantic Jet Stream in Reanalysis

Abstract Jet streams play an important role in determining weather variability and extremes. A better understanding of the mechanisms driving long-term changes in the jet is essential to successfully anticipate extreme meteorological events. This study analyzes the intensification trend of the North Atlantic jet using the ERA5 reanalysis and investigates the dynamical mechanisms involved. The results highlight the importance of an increase in diabatic heating in the free troposphere below the jet entrance over the Gulf Stream sector. This change in diabatic heating modifies the jet directly and produces a local intensification and a slight poleward shift. A two-dimensional frontal-geostrophic model illustrates this mechanism by considering the enhanced diabatic heating associated with the baroclinic growth of extratropical cyclones. The change in diabatic heating also affects the jet indirectly by increasing the mean baroclinicity and subsequent eddy momentum flux convergence. This indirect mechanism has also an effect downstream, where there is an acceleration of the jet core and reduced westerlies along the flanks, reducing the width of the jet. An idealized warming experiment confirms this mechanism by determining the jet response downstream of an idealized land–sea contrast. Finally, using a single-model ensemble of fully coupled climate simulations, we show that the differences in the evolution of the North Atlantic jet are related to the latitude of the increase in baroclinicity, which has a large spread. What emerges from the model hierarchy is a consistent dynamical chain of mechanisms associated with the intensification trend of the North Atlantic jet stream.

Climate Warming Impacts Tuttuk (Caribou) Forage Availability in Tongait (Torngat) Mountains, Labrador

Tuttuk [caribou (Rangifer tarandus)] populations are in decline across Canada, making them a major conservation concern for Inuit of Nunatsiavut (Northern Labrador) and Nunavik (Northern Quebec). This study investigates changes to caribou forage over 14-years at two tundra sites in northern Nunatsiavut, Labrador. We ask: 1) How much of the total vegetation is suitable caribou forage and how has this changed with time and experimental warming; and 2) Which forage species are most affected by recent climate change? At control and warming plots, we identified selected, edible, and avoided caribou forage based on published literature, and modeled observed changes in forage availability. We found that the relative frequency of selected winter forage was lower than summer forage at both sites. Caribou appear to be more forage limited in the winter than summer, and birch (Betula spp.), and ericaceous shrub species (Vaccinium spp.), increased over time. Our research provides valuable insight into recent changes in caribou forage availability and develops a novel methodology that can be applied across other caribou ranges. This knowledge will inform conservation and management measures by helping identify possible forage limitations and can contribute to recovery targets across Nunatsiavut and ultimately the social-ecological resilience of northern communities.

Invasive plants grow taller under experimental warming, but mediated effects of biotic interactions are species‐specific

Understanding the responses of non‐native plants to climate change while accounting for biotic interactions is key to predicting and mitigating future invasion risks. Non‐native invasive plants may benefit from or decline in the face of climate change, relative to native competitors. Non‐native plants might also suffer less than native plants from natural enemies such as herbivores, which could give non‐natives a competitive advantage. However, we lack an understanding of how non‐native plants will compete with native plants in a warming climate, while accounting for the effects of herbivore pressure. To test the potential interactions between warming, herbivore pressure and competition, we set up a common‐garden experiment in Trondheim, Norway, using five non‐native plants growing either alone or in competition with a native plant community. These plants were subjected to herbivore exclusion and artificial warming treatments, using open‐top chambers. We found that under warming, three non‐native species had greater biomass and all five species were taller than when grown without warming. Competition with native species reduced the biomass of three non‐native species and herbivore exclusion resulted in taller plants for three non‐native species. Native community biomass was not affected by either warming or herbivore exclusion. Furthermore, the native community was not affected by competition with any non‐native plant except Centaurea montana, which resulted in lower native community biomass, suggesting that C. montana is likely to be the most detrimental of these non‐native species to native communities. Competition with natives reduced the positive effects of warming on biomass for only one species, Alchemilla mollis. Our study strongly suggests that a warming climate may benefit invasive plants more than native plants, but for some species these effects will be mediated by biotic interactions in idiosyncratic ways, depending on the identity of both native and non‐native species. This will present a challenge to predicting plant invasion success under climate change while accounting for biotic interactions.

Nitrogen regulated reactive oxygen species metabolism of leaf and grain under elevated temperature during the grain-filling stage to stabilize rice substance accumulation

Rational additional nitrogen is an important agronomic measure to cope with the adverse effects of warming on rice production. However, the mechanism by which nitrogen mitigated the adverse impact of substance accumulation due to elevated temperature is poorly clarified. Therefore, in this study, a field warming experiment during grain filling and 60 kg·ha−1 of additional nitrogen was established. Under elevated temperature, panicle temperature was higher and increased more substantially than leaf temperature. However, nitrogen application did not significantly reduce the leaf, panicle, and canopy temperatures. Additional nitrogen under elevated temperature delayed the decline of chlorophyll, maintained leaf photosynthesis, and prolonged grain-filling period to alleviate the decrease of starch due to warming. Hydrogen peroxide (H2O2) was sensitive to elevated temperature in leaves and grains. However, application of nitrogen under elevated temperature improved the activity of antioxidant enzymes to mitigate the increase of H2O2, resulting in a 30.31 % and 45.33 % decrease of H2O2 in leaves and grains compared to elevated temperature, respectively. Elevated temperature promoted the expression of heat-responsive genes, especially HSP16.9 and HSP26.7, which were consistently increased in response to warming at 5–30d after flowering. In addition, the expression of HSP16.9 at 5d and 10d after flowering and HSP26.7 at 10d after flowering was further increased with nitrogen application under elevated temperature. Therefore, HSP may be the key regulator of grain response to warming with additional nitrogen under elevated temperature. In conclusion, the relevant results revealed the physiological mechanism of nitrogen to guarantee substance accumulation and provided new ideas for cultivation measures to protect against the likely scenario of global warming.

Hotter Temperatures Reduce the Diversity and Alter the Composition of Woody Plants in an Amazonian Forest.

Rapid warming and high temperatures are an immediate threat to global ecosystems, but the threat may be especially pronounced in the tropics. Although low-latitude tree species are widely predicted to be vulnerable to warming, information about how tropical tree diversity and community composition respond to elevated temperatures remains sparse. Here, we study long-term responses of tree diversity and composition to increased soil and air temperatures at the Boiling River-an exceptional and unique "natural warming experiment" in the central Peruvian Amazon. Along the Boiling River's course, geothermally heated water joins the river, gradually increasing water temperature and subsequently warming the surrounding forest. In the riparian forests along the Boiling River, mean annual and maximum air temperatures span gradients of 4°C and 11°C, respectively, over extremely short distances (< 1 km), with the hottest temperatures matching those predicted for much of the Amazon under future global warming scenarios. Using a new network of 70 woody plant inventory plots situated along the Boiling River's thermal gradient, we observed a ca. 11% decline in tree α-diversity per 1°C increase in mean annual temperature. We also found that the tree communities growing under elevated temperatures were generally more thermophilic (i.e., included greater relative abundances of species from hotter parts of the Amazon) than the communities in cooler parts of the gradient. Based on patterns at the Boiling River, we hypothesize that global warming will lead to dramatic shifts in tree diversity and composition in the lowland Amazon, including local extinctions and biotic attrition.