Global Change Biology最新文献

Climate change is altering precipitation regimes that control nitrogen (N) cycling in terrestrial ecosystems. In ecosystems exposed to frequent drought, N can accumulate in soils as they dry, stimulating the emission of both nitric oxide (NO; an air pollutant at high concentrations) and nitrous oxide (N₂O; a powerful greenhouse gas) when the dry soils wet up. Because changes in both N availability and soil moisture can alter the capacity of nitrifying organisms such as ammonia-oxidizing bacteria (AOB) and archaea (AOA) to process N and emit N gases, predicting whether shifts in precipitation may alter NO and N₂O emissions requires understanding how both AOA and AOB may respond. Thus, we ask: How does altering summer and winter precipitation affect nitrifier-derived N trace gas emissions in a dryland ecosystem? To answer this question, we manipulated summer and winter precipitation and measured AOA- and AOB-derived N trace gas emissions, AOA and AOB abundance, and soil N concentrations. We found that excluding summer precipitation increased AOB-derived NO emissions, consistent with the increase in soil N availability, and that increasing summer precipitation amount promoted AOB activity. Excluding precipitation in the winter (the most extreme water limitation we imposed) did not alter nitrifier-derived NO emissions despite N accumulating in soils. Instead, nitrate that accumulated under drought correlated with high N₂O emission via denitrification upon wetting dry soils. Increases in the timing and intensity of precipitation that are forecasted under climate change may, therefore, influence the emission of N gases according to the magnitude and season during which the changes occur.

Effectively modeling the impact of climate change on any population requires careful consideration of diverse pressures. Potential changes in interactions with other species must be accounted for. As communities reassemble and shifts in abundance and distribution cascade throughout ecosystems, cumulative impacts on species of conservation concern need to be explicitly examined. A structured qualitative analysis of alternative responses to climate change across the food web can play a valuable role in the design and interpretation of quantitative models. A particular advantage of qualitative network analysis is the ease with which a wide range of scenarios representing structural and quantitative uncertainties can be explored. We tested 36 plausible representations of connections among salmon and key functional groups within the marine food web using qualitative network models. The scenarios differed in how species pairs were connected (positive, negative, or no interaction) and which species responded directly to climate change. Our analysis showed that certain configurations produced consistently negative outcomes for salmon, regardless of the specific values for most of the links. Salmon outcomes shifted from 30% to 84% negative when consumption rates by multiple competitor and predator groups increased following a press perturbation from climate. This scenario aligns with some recent observations during a marine heatwave. Feedbacks between salmon and mammalian predators were particularly important, as were indirect effects connecting spring- and fall-run salmon. We also identified which links most strongly influenced salmon outcomes in other scenarios. Our results emphasize the importance of structural uncertainty in food webs and demonstrate a tool for exploring it, paving the way for more targeted and effective research planning.

Climate change and biological invasions are among the most important drivers of biodiversity and ecosystem change. Despite major advances in understanding their ecological impacts, these drivers are often considered individually, overlooking their possible complex interrelationship. By applying structural equation modeling to an extensive nationwide dataset of 430 fish communities across 257 French lakes, we investigated how taxonomic, size, and trophic diversities are impacted by climate warming and exotic species occurrence. Our goal was to compare their relative signature or lasting impacts after these factors had taken effect and to determine whether climate warming and biological invasions mediate the current state of community diversities. Drawing on a set of interconnected hypotheses, we suggest that biological invasions could be an important indirect effect of climate warming. This aspect must be considered to fully grasp the overall effects of climate change, beyond just its direct thermal impacts. Our results support our hypothesis that climate warming negatively impacts size and trophic diversities. However, these effects are mostly mediated by the warming-induced increase in exotic species richness, which, in turn, promotes total species richness. These results suggest that exotic species have a substantial role in determining the impact of climate change, obscuring the diversity patterns predicted by temperature alone. We conclude that the impacts of climate change cannot be understood without considering its mediated effects via biological invasions, underscoring the need to grasp their intertwined roles in predicting and managing ecological consequences.

Changing environmental conditions are leading to shifts in the timing of seasonal events globally. In the ocean, environmental cues affecting larval fish (ichthyoplankton) abundance may not be synchronized with factors optimizing larval and juvenile survival, making the study of ichthyoplankton phenology in the context of a changing environment critical. In the southern California Current Ecosystem (CCE), a major eastern boundary current upwelling system, significant long-term shifts in larval fish phenology have been previously observed. To assess the stability of these estimates and extend them to the northern CCE, we evaluated multidecadal trends in ichthyoplankton abundance for 57 species from the California Cooperative Oceanic Fisheries Investigations (CalCOFI) and 25 species from the Newport Hydrographic Line (NH Line). We show that on average, larval fish phenology in the southern CCE has continued to advance with an estimated rate of −0.18 ± 0.05 day year⁻¹ from 1951 to 2022, while phenology in the northern CCE has advanced at a rate of −0.48 ± 0.26 day year⁻¹ from 1996 to 2023. Thirty-nine percent of species showed significant advancing phenology, 12% exhibited delayed phenology, and 49% showed no long-term linear change. A comparison analysis showed that species in these groups had similar rates of change between the two locations for the 1997–2017 period. Phenological shifts in the southern CCE tracked changes in the phenology of upper ocean temperature, zooplankton, and upwelling. These variables poorly explained shifts in the northern CCE, where short-term effects of the El Niño–Southern Oscillation and the 2014–2016 marine heatwave on ichthyoplankton phenology were observed for some species. This research highlights regional variability and continuing phenological shifts in one of the world's most productive marine ecosystems.

Ecosystem restoration is urgently needed to restore, maintain, or increase valued ecosystem services provided by natural habitats. However, the provision of services in restored habitats, in comparison to natural, undegraded habitats, and the time required for them to be generated, is uncertain. Here, for the first time in coastal (or to our knowledge, any) ecosystems, we systematically outline why and how to characterize pathways of ecosystem service recovery following restoration. Using real-world and theoretical examples, mainly from coastal habitats, we outline seven key components required to characterize ecosystem service trajectories. These components are the baseline rate and variability of ecosystem service provisioning, and the trend type, direction, rate, time to natural equivalence and variability of restored ecosystem service provisioning. These components provide novel insights into the development of ecosystem services and values over time, and their use can help in planning on-ground restoration projects and monitoring regimes, valuing ecosystem services, and determining restoration success.

Human-induced environmental changes are altering forest productivity and species composition, significantly impacting tree physiology, growth, water uptake, and nutrient acquisition. Investigating the intricate interplay between plant physiology and environmental shifts, we analyzed tree-ring isotopes (δ¹³C, δ¹⁸O, and δ¹⁵N) to track long-term trends in intrinsic water-use efficiency (iWUE) and nitrogen availability for European beech, Norway spruce, and silver fir in a unique old-growth temperate mountain forest since 1501 ce. Our findings reveal that Norway spruce, a dominant species, exhibited iWUE saturation, exacerbated by acidic precipitation, resulting in growth declines during periods of high acidic air pollution and increased drought frequency. In contrast, deep-rooted, deciduous European beech demonstrated physiological resilience to acid deposition, benefiting from lower dry deposition of precipitation acidity and thriving under conditions of increased nitrogen deposition and elevated air temperatures, thereby sustaining stem growth regardless of potential climatic limitations. Silver fir showed the most dynamic response to acidic air pollution, with contemporary adaptations in leaf gas exchange allowing accelerated stem growth under cleaner air conditions. These different species responses underscore shifts in species competition, with European beech gaining dominance as Norway spruce and silver fir decline. Furthermore, the influence of ontogeny is evident, as tree-rings exhibited lower initial iWUE values and higher δ¹⁵N, reflecting changes in nitrogen uptake dynamics and the ecological role of tree age. Our study integrates tree-growth dynamics with physiological and nutrient availability trends, revealing the pivotal role of atmospheric chemistry changes in shaping the competitive dynamics and long-term growth trajectories of dominant tree species in temperate forests.