Frontiers in Ecology and the Environment最新文献

Stream drying is happening globally, with important ecological and social consequences. Most examples of stream drying come from systems influenced by dam operations or those with highly exploited aquifers. Stream drying is also thought to be driven by anthropogenic climate change; however, examples are surprisingly limited. We explored flow trends from the five recognized Mediterranean-climate regions of the world with a focus on unregulated (non-dammed or non-diverted) streams with long-term gauge records. We found consistent evidence of decreasing discharge trends, increasing zero-flow days, and steeper downward discharge trends in smaller basins. Beyond directional trends, many systems have recently undergone shifts in flow state, including some streams that have transitioned from perennial to intermittent flow states. Our analyses provide evidence of stream drying consistent with climate change but also highlight knowledge gaps and challenges in empirically and statistically documenting flow regime shifts. We discuss the myriad consequences of losing flow and propose strategies for improving detection of and adapting to flow change.

While considered ecological generalists in most aspects of their life history, horseshoe crabs (Limulus polyphemus) have traditionally been regarded as reproductive habitat specialists, given that spawning is thought to occur primarily on beaches where conditions for embryonic development are considered optimal. Observations of horseshoe crabs spawning in other habitats were deemed isolated and the behavior non-adaptive. Here, we used spawning and egg surveys to compare the use of beach and salt marsh habitats for spawning by the horseshoe crab in three US states along the Atlantic coast. We found similar spawning and egg densities in both habitats but were more likely to find eggs in marsh habitats, indicating that spawning in marsh habitats is common and geographically widespread. These results suggest that the conservation of salt marshes may be critical for the protection of this species and that management strategies should be revised to incorporate this generalist behavior.

The world's rangelands and drylands are undergoing rapid change, and consequently are becoming more difficult to manage. Big data and digital technologies (digital tools) provide land managers with a means to understand and adaptively manage change. An assortment of tools—including standardized field ecosystem monitoring databases; web-accessible maps of vegetation change, production forecasts, and climate risk; sensor networks and virtual fencing; mobile applications to collect and access a variety of data; and new models, interpretive tools, and tool libraries—together provide unprecedented opportunities to detect and direct rangeland change. Accessibility to and manager trust in and knowledge of these tools, however, have failed to keep pace with technological advances. Collaborative adaptive management that involves multiple stakeholders and scientists who learn from management actions is ideally suited to capitalize on an integrated suite of digital tools. Embedding science professionals and experienced technology users in social networks can enhance peer-to-peer learning about digital tools and fulfill their considerable promise.

Climate change is altering fire regimes and post-fire conditions, contributing to relatively rapid transformation of landscapes across the western US. Studies are increasingly documenting post-fire vegetation transitions, particularly from forest to non-forest conditions or from sagebrush to invasive annual grasses. The prevalence of climate-driven, post-fire vegetation transitions is likely to increase in the future with major impacts on social–ecological systems. However, research and management communities have only recently focused attention on this emerging climate risk, and many knowledge gaps remain. We identify three key needs for advancing the management of post-fire vegetation transitions, including centering Indigenous communities in collaborative management of fire-prone ecosystems, developing decision-relevant science to inform pre- and post-fire management, and supporting adaptive management through improved monitoring and information-sharing across geographic and organizational boundaries. We highlight promising examples that are helping to transform the perception and management of post-fire vegetation transitions.

While hiking in the Carolinas of the southeastern US, I was baffled by curious strands emerging from the forest floor, covered in fresh snow. Later, I learned that I had observed “needle ice” (see image), a form of ice that is related to a different phenomenon known as “hair ice”.

Hair ice, also called ice wool or frost beard, originates from the fungus Exidiopsis effusa. In 1918, Alfred Wegener (who earlier had proposed continental drift theory) suggested a fungus as the suspected source of the delicate strands of hair ice. However, E effusa was not identified as the responsible fungal agent until 2015 by Hofmann et al., whose seminal work (Biogeosciences 2015; doi.org/10.5194/bg-12-4261-2015) provides an excellent review of discoveries related to hair ice, including: (i) E effusa's gossamer-like hair ice is fragile (disintegrating if handled) and ephemeral (lasting for hours or a few days under ideal conditions); (ii) E effusa emerges only from decomposing branches of broadleaf trees and in temperatures at or below 0°C; (iii) the fungus has been reported in multiple countries between the latitudes of 45° and 55°N; (iv) the mycelium of E effusa appears to provide the supporting structure for the hairs of ice, which have a diameter of around only 0.02 mm; (v) hair ice forms from a dense concentration of mycelium, drawing water from the porous substrate of the wood; (vi) a recrystallization inhibitor is likely responsible for the stabilization of the fine hairs; and (vii) E effusa's fruiting body typically appears macroscopically weeks later on the wood surface as a thin, white rot coating.

The specimen featured in the accompanying photograph is needle ice. Often mistaken for hair ice, needle ice is a related ice type that grows from soil instead of wood, has slightly stiffer needles, and forms columns (Mätzler C, Wagner G, Preuss G, and Hofmann D. 2013. Enlightening the mystery of hair ice. IAP Research Report 2013-01-MW. Bern, Switzerland: Institute of Applied Physics, University of Bern). The source of needle ice formations is not associated with a fungus; rather, it is groundwater, which rises to the surface by capillary action and freezes. The phenomenon occurs in areas that experience frequent thaw–freeze cycles (Cold Regions Sci Technol 1988; doi.org/10.1016/0165-232X(88)90076-6). Needle ice is also recognized as a cause of soil disturbance, though its unusual appearance, like that of hair ice, is especially captivating.

Special thanks to Diana Hofmann for help with identification.

While conducting field research on plants in China's western Sichuan Plateau during July 2022, we observed the perennial herb Przewalskia tangutica (Solanaceae) with pocket-like green bracts (hereafter, “green pockets” or simply “pockets”). Each plant had multiple green pockets, and each green pocket contained a single fruit along its interior base. Interestingly, we found that the pocket would naturally fall off the plant once its fruit was mature. Then, as the pocket—now disconnected from its plant—gradually desiccated, it became so light that it could easily be blown far away by the wind. A few days after gaining its independence, the pocket almost entirely decayed, leaving only a mesh-like framework of veins, thereby allowing the seeds to escape. This finding suggests that the pocket plays a role in seed dispersal and promotes the spread of P tangutica, an imperiled species found at high elevations and subject to overharvesting due to its medicinal properties. However, some questions remain unanswered. Because each pocket has a small mouth-like opening at its top, if rain falls into a pocket, does it affect fruit and seed development? Does the green pocket contribute resources (such as carbon and energy) to fruit and seed development through photosynthesis? Was the evolution of the pocket driven by harsh physical conditions (such as low temperatures, ultraviolet radiation from intense sunlight, or heavy rains) on the plateau? Does the pocket provide protection against potential seed predators?

In mixed-species groups, moray eels (Muraenidae) can function as focal species, hunting for prey within the deep interstices of reefs and, in the process, flushing out potential prey that are then vulnerable to attack by the moray's companions. On 7 December 2021, we observed an unusually large mixed-species hunting group of piscivorous fishes, composed of 26 bluefin trevally (Caranx melampygus), two black jack (Caranx lugubris), and three whitetip reef sharks (Triaenodon obesus) following a single yellow-edged moray (Gymnothorax flavimarginatus) at dusk along the deep (21 m) reef–sand margin off Manuelita Island in Isla del Coco National Park (Pacific Costa Rica). The moray entered a crevice (indicated by the arrow, in the top image) in an isolated coral framework while the primary hunting group circled the vicinity in both clockwise and counterclockwise directions, and the sharks entered and exited the crevice for about seven minutes before dispersing with only the moray remaining. The association of the hunting group may have enabled its members to encounter disturbed prey and then to provoke the moray to continue swimming and hunting, and thus flush out additional prey at other nearby locations. Current understanding remains limited for how predators determine trade-offs for hunting in groups versus individually, how predators share information related to group formation and dissolution, and what the outcomes of such behaviors are in terms of individual fitness. How short-term mutualisms such as these shape the functional relationships between predators and prey in fish communities is an area in need of enhanced attention, given the existing threats to large predators from overfishing and the need to conserve species interactions as a component of ecosystem management.

Future dynamics of biological invasions are highly uncertain because they depend on multiple social–ecological drivers. We used a scenario-based approach to explore potential management options for invasive species in Europe. During two workshops involving a multidisciplinary team of experts, we developed a management strategy arranged into 19 goals relating to policy, research, public awareness, and biosecurity. We conceived solutions for achieving these goals under different plausible future scenarios, and identified four interrelated recommendations around which any long-term strategy for managing invasive species can be structured: (1) a European biosecurity regime, (2) a dedicated communication strategy, (3) data standardization and management tools, and (4) a monitoring and assessment system. Finally, we assessed the feasibility of the management strategy and found substantial differences among scenarios. Collectively, our results indicate that it is time for a new strategy for managing biological invasions in Europe, one that is based on a more integrative approach across socioeconomic sectors and countries.