To assess the time-dependent stress evidence in dynamic allocation of physiological metabolism of Nilaparvata lugens nymphs in response to elevated CO₂, we measured the time-dependent allocation of nutrient compositions and physiological metabolism in the bodies of N. lugens at 1h, 4h and 12h under elevated CO₂. Elevated CO₂ significantly increased the contents of nutrient compositions (protein, glucose and total amino acids) and catalase (CAT) enzyme activity in the body of N. lugens at 12h relative to 1h and 4h (P < 0.05). Significantly higher genes expression levels of acetylcholinesterase (AChE), heat shock protein (HSP70) and vitellogenin gene (vg) were observed in the body of N. lugens compared with those in ambient CO₂ at 4h (P < 0.05). These results showed that there was an instantaneous reaction of N. lugens nymphs to elevated CO₂, which indicated N. lugens may enhance stress defense response to future increasing CO₂ levels.

To assess the effects of elevated concentrations of carbon dioxide (CO2) and ozone (O3) on the growth of two mid-successional oak species native to East Asia, Quercus mongolica var. crispula and Quercus serrata, we measured gas exchange and biomass allocation in seedlings (initially 1-year-old) grown under combinations of elevated CO2 (550 μmol mol−1) and O3 (twice-ambient) for two growing seasons in an open-field experiment in which root growth was not limited. Both the oak species showed a significant growth enhancement under the combination of elevated CO2 and O3 (indicated by total dry mass; over twice of ambient-grown plants, p < .05), which probably resulted from a preferable biomass partitioning into leaves induced by O3 and a predominant enhancement of photosynthesis under elevated CO2. Such an over-compensative response in the two Japanese oak species resulted in greater plant growth under the combination of elevated CO2 and O3 than elevated CO2 alone.

The anatomical and chemical characteristics of sweetgum were studied after 11 years of elevated CO2 (544 ppm, ambient at 391 ppm) exposure. Anatomically, branch xylem cells were larger for elevated CO2 trees, and the cell wall thickness was thinner. Chemically, elevated CO2 exposure did not impact the structural components of the stem wood, but non-structural components were significantly affected. Principal component analysis (PCA) was employed to detect differences between the CO2 treatments by considering numerous structural and chemical variables, as well as tree size, and data from previously published sources (i.e., root biomass, production and turnover). The PCA results indicated a clear separation between trees exposed to ambient and elevated CO2 conditions. Correlation loadings plots of the PCA revealed that stem structural components, ash, Ca, Mg, total phenolics, root biomass, production and turnover were the major responses that contribute to the separation between the elevated and ambient CO2 treated trees.

Elevated CO₂ concentrations can change the multi-level nutritional relationship of the ecosystem through the cascading effect of the food chain. To date, few studies have investigated the effects of elevated CO₂ concentration on the Araneae species through the tritrophic system. Hylyphantes graminicola (Araneae: Linyphiidae) is distributed widely in Asia and is a dominant predator in cotton fields. This study investigated chemical components in the food chain of cotton (Gossypium hirsutum)—cotton aphid (Aphis gossypii)—predator (H. graminicola) and compared the development, reproduction, and predation of H. graminicola under ambient (400 ppm) and elevated concentration of CO₂ (800 ppm). The results showed that the elevated CO₂ concentration increased the chemicals of cotton and cotton aphid, but it did not affect the nutrients, development, reproduction, and predation of the spider. However, the survival rate of the spider was significantly decreased in elevated CO₂. The results will further our understanding of the role of natural enemies in an environment with elevated CO₂ concentration.

Mean oceanic CO₂ values have already risen and are expected to rise further on a global scale. Elevated pCO₂ (eCO₂) changes the bacterial community in seawater. However, the ecological association of seawater microbiota and related geochemical functions are largely unknown. We provide the first evidence that eCO₂ alters the interaction patterns and functional potentials of microbiota in rearing seawater of the swimming crab, Portunus trituberculatus. Network analysis showed that eCO₂ induced a simpler and more modular bacterial network in rearing seawater, with increased negative associations and distinct keystone taxa. Using the quantitative microbial element cycling method, nitrogen (N) and phosphorus (P) cycling genes exhibited the highest increase after one week of eCO₂ stress and were significantly associated with keystone taxa. However, the functional potential of seawater bacteria was decoupled from their taxonomic composition and strongly coupled with eCO₂ levels. The changed functional potential of seawater bacteria contributed to seawater N and P chemistry, which was highlighted by markedly decreased NH₃, NH₄⁺-N, and PO₄³⁻-P levels and increased NO₂⁻-N and NO₃⁻-N levels. This study suggests that eCO₂ alters the interaction patterns and functional potentials of seawater microbiota, which lead to the changes of seawater chemical parameters. Our findings provide new insights into the mechanisms underlying the effects of eCO₂ on marine animals from the microbial ecological perspective.

We utilized volcanic CO₂ vents at Castello Aragonese off Ischia Island as a natural laboratory to investigate the effect of lowered pH/elevated CO₂ on the bioactivities of extracts from fleshy brown algae Sargassum vulgare C. Agardh. We analysed the carbohydrate levels, antioxidant capacity, antibacterial, antifungal, antiprotozoal, anticancer properties and antimutagenic potential of the algae growing at the acidified site (pH ∼ 6.7) and those of algae growing at the nearby control site Lacco Ameno (pH∼8.1). The results of the present study show that the levels of polysaccharides fucoidan and alginate were higher in the algal population at acidified site. In general, extracts for the algal population from the acidified site showed a higher antioxidant capacity, antilipidperoxidation, antibacterial, antifungal, antiprotozoal, anticancer activities and antimutagenic potential compared to the control population. The increased bioactivity in acidified population could be due to elevated levels of bioactive compounds of algae and/or associated microbial communities. In this snapshot study, we performed bioactivity assays but did not characterize the chemistry and source of presumptive bioactive compounds. Nevertheless, the observed improvement in the medicinal properties of S. vulgare in the acidified oceans provides a promising basis for future marine drug discovery.

Concentrations of atmospheric carbon dioxide have been continuously increasing, and more investigations are needed in regard to the responses of various plants to the corresponding climatic conditions. In particular, potential variations in phytoremediation efficiency induced by global warming have rarely been investigated. Objective of this research was to evaluate the changes in phytoremediation efficiency of Noccaea caerulescens exposed to different concentrations of CO2. The concentrations of CO2 in the elevated CO2 treatments were adjusted to 550 ± 50 ppm to match the level of atmospheric CO2 predicted in 2050–2070. Compared to ambient controls (400 ppm), biomass yields and metal concentrations of N. caerulescens increased under elevated CO2 conditions, thus indicating that the phytoremediation efficiency of the species could increase in higher CO2 environment. In addition, water soluble and exchangeable Pb and Cu concentrations in soils decreased under elevated CO2 conditions, which reduced the leaching risks of the metals. The concentrations of malondialdehyde (MDA) of N. caerulescens decreased to different degrees with the increased CO2 concentrations. The overall findings suggested that elevations in CO2 can reduce the oxidative damage caused by metals in this species. The phytoremediation efficiency of N. caerulescens grown in multiple metal-enriched soils could be enhanced with global warming.

Responses of streamflow and nutrient export to changing climate conditions should be investigated for effective water quality management and pollution control. Using downscaled climate projections and the Soil and Water Assessment Tool (SWAT), we projected future streamflow, sediment export, and riverine nutrient export in the St. Croix River Basin (SCRB) during 2020–2099. Results show substantial increases in riverine water, sediment, and nutrient load under future climate conditions, particularly under the high greenhouse gas emission scenario. Intensified water cycling and enhanced nutrient export will pose challenges to water quality management and affect multiple Best Management Practices (BMPs) efforts, which are aimed at reducing nutrient loads in SCRB. In addition to the physical impacts of climate change on terrestrial hydrology, our analyses demonstrate significant reductions in ET under elevated atmospheric CO₂ concentrations. Changes in plant physiology induced by climate change may markedly affect water cycling and associated sediment and nutrient export. Results of this study highlight the importance of examining climate change impacts on water and nutrient delivery for effective watershed management.

Historical increases in emissions and atmospheric deposition of oxidized and reduced nitrogen (N) provided the impetus for extensive, global-scale research investigating the effects of excess N in terrestrial and aquatic ecosystems, with several regions within the Eastern Deciduous Forest of the United States found to be susceptible to negative effects of excess N. The Clean Air Act and associated rules have led to decreases in emissions and deposition of oxidized N, especially in eastern U.S., representing a research challenge and opportunity for ecosystem ecologists and biogeochemists. The purpose of this paper is to predict changes in the structure and function of North American forest ecosystems in a future of decreased N deposition. Hysteresis is a property of a system wherein output is not a strict function of corresponding input, incorporating lag, delay, or history dependence, particularly when the response to decreasing input is different from the response to increasing input. We suggest a conceptual hysteretic model predicting varying lag times in recovery of soil acidification, plant biodiversity, soil microbial communities, forest carbon (C) and N cycling, and surface water chemistry toward pre-N impact conditions. Nearly all of these can potentially respond strongly to reductions in N deposition. Most responses are expected to show some degree of hysteresis, with the greatest delays in response occurring in processes most tightly linked to “slow pools” of N in wood and soil organic matter. Because experimental studies of declines in N loads in forests of North America are lacking and because of the expected hysteresis, it is difficult to generalize from experimental results to patterns expected from declining N deposition. These will likely be long-term phenomena, difficult to distinguish from other, concurrent environmental changes, including elevated atmospheric CO₂, climate change, reductions in acidity, invasions of new species, and long-term vegetation responses to past disturbance.

Glomalin-related soil protein (GRSP), which contains glycoproteins produced by arbuscular mycorrhizal fungi (AMF), as well as non-mycorrhizal-related heat-stable proteins, lipids, and humic materials, is generally categorized into two fractions: easily extractable GRSP (EE-GRSP) and total GRSP (T-GRSP). GRSP plays an important role in soil carbon (C) sequestration and can stabilize heavy metals such as lead (Pb), cadmium (Cd), and manganese (Mn). Soil contamination by heavy metals is occurring in conjunction with rising atmospheric CO2 in natural ecosystems due to human activities. However, the response of GRSP to elevated CO2 combined with heavy metal contamination has not been widely reported. Here, we investigated the response of GRSP to elevated CO2 in the rhizosphere of Robinia pseudoacacia L. seedlings in Pb- and Cd-contaminated soils. Elevated CO2 (700 μmol mol−1) significantly increased T- and EE- GRSP concentrations in soils contaminated with Cd, Pb or Cd + Pb. GRSP contributed more carbon to the rhizosphere soil organic carbon pool under elevated CO2 + heavy metals than under ambient CO2. The amount of Cd and Pb bound to GRSP was significantly higher under elevated (compared to ambient) CO2; and elevated CO2 increased the ratio of GRSP-bound Cd and Pb to total Cd and Pb. However, available Cd and Pb in rhizosphere soil under increased elevated CO2 compared to ambient CO2. The combination of both metals and elevated CO2 led to a significant increase in available Pb in rhizosphere soil compared to the Pb treatment alone. In conclusion, increased GRSP produced under elevated CO2 could contribute to sequestration of soil pollutants by adsorption of Cd and Pb.