Key Ecological Processes Research Articles

Extreme climate events can slow down litter breakdown in streams

Extreme temperatures have increased in intensity, duration and frequency in the last century, with potential consequences on key ecological processes such as organic matter breakdown. Many stream ecosystems are fueled by the breakdown of terrestrial leaf litter, which is exposed to atmospheric conditions for certain periods of time before entering the stream. Thus, extreme warming or freezing events may affect the litter physicochemical structure, which could translate into altered breakdown within the stream. The above prediction was tested by exposing litter of common riparian tree species in southern Chile to freezing (−20 oC; dry or wet litter) or heating (40 oC) and comparing breakdown with control litter exposed to room temperature (20 oC), separating the effects of different breakdown agents (i.e., leaching, microorganisms and detritivores). The greatest effects were found in wet litter subjected to freezing; this treatment significantly increased leaching in the short term (48 h) and slowed down breakdown in the long term (30 days), mostly due to the inhibition of microbial breakdown. Heating also retarded microbial breakdown, but the effect was smaller. Our results suggest that short-term extreme temperatures—particularly cold ones—have the potential to slow down litter breakdown in streams, which will most likely impact global biogeochemical cycles where streams play a key role.

Ocean currents and the population genetic signature of fish migrations.

Animal migrations are a fascinating and global phenomenon, yet they are often difficult to study and sometimes poorly understood. Here, we build on classic ecological theory by hypothesizing that some enigmatic spawning migrations across coastal marinehabitats can be inferred from the population genetic signature of larval dispersal by ocean currents. We test this assumption by integrating spatially realistic simulations of alternative spawning migration routes, associated patterns of larval dispersal, and associated variation in the population genetic structure of eastern Australian sea mullet (Mugil cephalus). We then use simulation results to assess the implications of alternative spawning destinations for larval replenishment, and we contrast simulated against measured population genetic variation. Both analyses suggest that the spawning migrations of M.cephalus in eastern Australia are likely to be localized (approximately 100km along the shore), and that spawning is likely to occur in inshore waters. Our conclusions are supported by multiple lines of evidence available through independent studies, but they challenge the more traditional assumption of a single, long-distance migration event with subsequent offshore spawning in the East Australian Current. More generally, our study operationalizes classic theory on the relationship between fish migrations, ocean currents, and reproductive success. However, rather than confirming the traditionally assumed adaptation of migratory behavior to dominant ocean current flow, our findings support the concept of a genetically measurable link between fish migrations and local oceanographic conditions, specifically water temperature and coastal retention of larvae. We believe that future studies using similar approaches for high resolution and spatially realistic ecological-genetic scenario testing can help rapidly advance our understanding of key ecological processes in many other marine species.

Understanding the Evolutionary Ecology of host--pathogen Interactions Provides Insights into the Outcomes of Insect Pest Biocontrol.

The use of viral pathogens to control the population size of pest insects has produced both successful and unsuccessful outcomes. Here, we investigate whether those biocontrol successes and failures can be explained by key ecological and evolutionary processes between hosts and pathogens. Specifically, we examine how heterogeneity in pathogen transmission, ecological and evolutionary tradeoffs, and pathogen diversity affect insect population density and thus successful control. We first review the existing literature and then use numerical simulations of mathematical models to further explore these processes. Our results show that the control of insect densities using viruses depends strongly on the heterogeneity of virus transmission among insects. Overall, increased heterogeneity of transmission reduces the effect of viruses on insect densities and increases the long-term stability of insect populations. Lower equilibrium insect densities occur when transmission is heritable and when there is a tradeoff between mean transmission and insect fecundity compared to when the heterogeneity of transmission arises from non-genetic sources. Thus, the heterogeneity of transmission is a key parameter that regulates the long-term population dynamics of insects and their pathogens. We also show that both heterogeneity of transmission and life-history tradeoffs modulate characteristics of population dynamics such as the frequency and intensity of “boom–bust" population cycles. Furthermore, we show that because of life-history tradeoffs affecting the transmission rate, the use of multiple pathogen strains is more effective than the use of a single strain to control insect densities only when the pathogen strains differ considerably in their transmission characteristics. By quantifying the effects of ecology and evolution on population densities, we are able to offer recommendations to assess the long-term effects of classical biocontrol.

Vegetation Pattern Modulates Ground Arthropod Diversity in Semi-Arid Mediterranean Steppes.

The ecological functioning of dryland ecosystems is closely related to the spatial pattern of the vegetation, which is typically structured in patches. Ground arthropods mediate key soil functions and ecological processes, yet little is known about the influence of dryland vegetation pattern on their abundance and diversity. Here, we investigate how patch size and cover, and distance between patches relate to the abundance and diversity of meso-and microarthropods in semi-arid steppes. We found that species richness and abundance of ground arthropods exponentially increase with vegetation cover, patch size, and patch closeness. The communities under vegetation patches mainly respond to patch size, while the communities in the bare-soil interpatches are mostly controlled by the average distance between patches, independently of the concurrent changes in vegetation cover. Large patches seem to play a critical role as reserve and source of ground arthropod diversity. Our results suggest that decreasing vegetation cover and/or changes in vegetation pattern towards small and over-dispersed vegetation patches can fast lead to a significant loss of ground arthropods diversity in drylands.

Seed dispersal networks in tropical forest fragments: Area effects, remnant species, and interaction diversity

AbstractSeed dispersal interactions involve key ecological processes in tropical forests that help to maintain ecosystem functioning. Yet this functionality may be threatened by increasing habitat loss, defaunation, and fragmentation. However, generalist species, and their interactions, can benefit from the habitat change caused by human disturbance while more specialized interactions mostly disappear. Therefore, changes in the structure of the local, within fragment, networks can be expected. Here we investigated how the structure of seed dispersal networks changes along a gradient of increasing habitat fragmentation. We analyzed 16 bird seed dispersal assemblages from forest fragments of a biodiversity‐rich ecosystem. We found significant species–, interaction–, and network–area relationships, yet the later was determined by the number of species remaining in each community. The number of frugivorous bird and plant species, their interactions, and the number of links per species decreases as area is lost in the fragmented landscape. In contrast, network nestedness has a negative relationship with fragment area, suggesting an increasing generalization of the network structure in the gradient of fragmentation. Network specialization was not significantly affected by area, indicating that some network properties may be invariant to disturbance. Still, the local extinction of partner species, paralleled by a loss of interactions and specialist–specialist bird–plant seed dispersal associations, suggests the functional homogenization of the system as area is lost. Our study provides empirical evidence for network–area relationships driven by the presence/absence of remnant species and the interactions they perform.Abstract in Spanish is available with online material.

Increased spatial-genetic structure in a population of the clonal aquatic plant Sagittaria latifolia (Alismataceae) following disturbance.

The spatial genetic structure (SGS) of plant populations is determined by the outcome of key ecological processes, including pollen and seed dispersal, the intensity of local resource competition among newly recruited plants, and patterns of mortality among established plants. Changes in the magnitude of SGS over time can provide insights into the operation of these processes. We measured SGS in a population of the clonal aquatic plant, Sagittaria latifolia that had been disturbed by flooding, both before and after the flood. Over the four-year interval between measurements, we found substantial changes in the magnitude of SGS. In the first measurement (pre-flood), SGS was weak, even over short distances. By contrast, there was substantial SGS in the second measurement (post-flood), particularly over short distances. This change in SGS was accompanied by near complete turnover in the genotypic composition of the population. The genotypic richness of the population (the number of unique clones scaled by the sample size) was halved over the four-year interval. The clonal subrange-the distances between shoots within clones-also shrank considerably, with more than 5% of shoots having clone-mates at distances >10 m before the flood, but fewer than 5% of shoots having clone-mates at distances beyond 2 m afterwards. Clonal turnover and the re-establishment of SGS in clonal populations are both expected following local extirpation and recruitment. These data reveal the genetic signatures of disturbance and a subsequent flush of seedling recruitment and clonal expansion.

Regional context and dispersal mode drive the impact of landscape structure on seed dispersal.

Land-use change modifies the spatial structure of tropical landscapes, shaping global biodiversity patterns. Yet, it remains unknown how key ecological processes, such as seed dispersal, can be affected by changes in landscape patterns, and whether such effects differ among regions with different climate and disturbance intensity. We assessed the effect of five landscape metrics (forest cover, matrix openness, forest edge density, forest fragmentation, and interpatch distance) on the seed rain recorded in two Mexican fragmented regions (20 forest sites per region): the more deforested, defaunated, and windy Los Tuxtlas rainforest (LTX), and the better-preserved Lacandona rainforest (LAC). We quantified the proportions of dispersed tree species and their seeds, separately evaluating wind- and animal-dispersed species. Our findings support the hypothesis that forest loss is more important than fragmentation per se, negatively impacting the seed rain in both regions. As expected, landscape patterns were comparatively more important for wind-dispersed seeds in LTX, probably because of stronger wind events in this region. Specifically, proportions of wind-dispersed seeds and species decreased with increasing edge density, suggesting that forest edges prevent dispersal of wind-dispersed species, which may occur if edges create physical barriers that limit wind flow. This pattern can also be caused by source limitation in landscapes with more forest edges, as tree mortality rates usually increase at forest edges. The wind-dispersed seed rain was also positively related to matrix openness, especially in LTX, where wind flow can be favored by the dominance of treeless anthropogenic matrices. Surprisingly, the proportion of animal-dispersed seeds in LTX was positively related to matrix openness and patch isolation, suggesting that seed dispersers in more deforested regions may be forced to concentrate in isolated patches and use the available habitat more intensively. Yet, as expected, patch isolation limited wind-dispersed seeds in LAC. Therefore, dispersal (and potentially regeneration) of wind-dispersed trees is favored in regions exposed to stronger wind events, especially in landscapes dominated by regularly shaped patches surrounded by open areas. Conversely, animal-dispersed seeds are primarily favored by increasing forest cover. Preventing forest loss is therefore critical to promote animal seed dispersal and forest recovery in human-modified rainforests.

Fungistatic effect of agrochemical and pharmaceutical fungicides on non-target aquatic decomposers does not translate into decreased fungi- or invertebrate-mediated decomposition

Leaf litter decomposition is a key ecological process in freshwater ecosystems. Fungi, particularly aquatic hyphomycetes, play a major role in organic matter turnover and constitute a pivotal node in detrital food webs. The extensive use of antifungal formulations, which include agrochemicals and pharmaceuticals, is a threat to biodiversity and may affect non-target microbial and invertebrate decomposer communities. Using a laboratory approach, we assessed the effects of tebuconazole (agrochemical), clotrimazole and terbinafine (pharmaceuticals) on aquatic communities and on the decomposition of plant litter. Alder leaves were colonized by natural microbiota in a clean stream, and then exposed in microcosms to 8 concentrations of each fungicide (10 to 1280 μg L−1). Fungicides led to shifts in species dominance in all tested concentrations, but no effects on leaf decomposition were observed. In addition, tebuconazole and clotrimazole strongly reduced fungal biomass and reproduction, whilst terbinafine stimulated fungal reproduction at lower concentrations but had no measurable effects on fungal biomass. Subsequently, the indirect effects of the fungicides were assessed on the next trophic level (detritivore invertebrates), by evaluating leaf consumption by a specialist (Allogamus sp.) and a generalist (Chironomus riparius) species, when feeding on fungicide-preconditioned leaves. The feeding activity of C. riparius and Allogamus sp. was not affected, and as expected, specialists were more efficient than generalists in exploring leaves as a dietary resource. However, results indicated that these fungicides have direct negative effects on microbial decomposers, and thus may compromise ecosystem functions on the long term.

Effects of Hydrological Connectivity on Snail Assemblages in the Intertidal Zone of Coastal Wetlands

Hydrological connectivity controls the patterns of invertebrate assemblages in wetland ecosystems. With degradation of intertidal wetlands, artificial freshwater release has become an important restoration technique. Hydrological connectivity with tidal creeks is also a key ecological process for intertidal wetlands. However, how hydrologic connectivity affects snail assemblages remains poorly investigated in intertidal wetlands. We studied the differences in snail assemblages in wetlands to understand the effects of hydrological connectivity, wetland to river, and wetland to ocean. We found freshwater connectivity can transform intertidal snail assemblages into freshwater snail assemblages; restored wetlands primarily had freshwater snail species and natural intertidal wetlands mainly supported marine or salt-adapted snail species. Cluster analysis, nMDS plot and ANOSIM analysis showed snail assemblages were influenced strongly by hydrological connectivity. Stenothyra glabra, Oncomelania sp. and Nassarius festivus were indicators of natural intertidal wetlands. Hippeutis cantori, Radix swinhoei and Succinea pfeifferi were indicators of restored wetlands. Our results suggest natural hydrological connectivity with the ocean needs to be maintained when attempting to restore intertidal wetlands. Without this connection, connecting impaired wetlands only to rivers, may not achieve restoration of natural biotic assemblages.

Nest association between two predators as a behavioral response to the low density of rodents

AbstractMany birds nest in association with aggressive birds of other species to benefit from their protection against predators. We hypothesized that the protective effect also could extend to foraging resources, whereby the resultant resource-enriched habitats near a nest of aggressive raptors could be an alternative cause of associations between nesting bird species with non-overlapping foraging niches. In the Arctic, the Rough-legged Hawk (Buteo lagopus) and the Peregrine Falcon (Falco peregrinus) are 2 raptor species with non-overlapping food resources that have been reported to nest sometimes in close proximity. Since nesting Peregrine Falcons are very aggressive, they may protect the small rodent prey near their nests from predation, and Rough-legged Hawks could use these hot spots as a nesting territory. In 2 regions in low Arctic Russia we found that (1) the nesting territories of Peregrine Falcons were indeed enriched with small rodents as compared to control areas, (2) the probability of nest association between the 2 raptors increased when rodent abundance was generally low in the region where hawks did not use alternative prey, and (3) hawk reproductive success increased when nesting close to Peregrine Falcons. These results suggest that implications of aggressive nest site defense in birds in certain cases may involve more mechanisms than previously explored. A key ecological process in tundra, rodent population cycles, may explain the occurrence and adaptive significance of a specific behavior pattern, the nesting association between 2 raptor species.

Key perspectives on early successional forests subject to stand-replacing disturbances

In forests subject to stand-replacing disturbances, early successional stands can provide important habitats for a range of species not typically present in long-undisturbed areas. Compared to old-growth forests, the habitat values of – and key ecological processes in – early successional forests have been less studied, perhaps due to a perception that early successional forests revert to a homogenous “clean slate” following stand-replacing disturbances. In this paper, we draw on 36 years of long-term research in the Mountain Ash (Eucalyptus regnans) and Alpine Ash (Eucalyptus delegatensis) forests of south-eastern Australia, together with examples from elsewhere around the world, to show that not all kinds of early successional forests are created equal. We argue that the ecological values of early successional forests can be profoundly affected by six inter-related factors: (1) The evolutionary context and environmental domain of a given ecosystem. (2) Successional stage and condition of a forest stand prior to disturbance. (3) Disturbance intensity, severity and type (e.g. wildfire versus clearcutting). (4) Post-disturbance conditions including climate and weather. (5) Post-disturbance management (e.g. salvage logging) which can have significant impacts on biological legacies. And, (6) The relative spatial extent and spatial arrangement of early and late successional forest across a landscape. These factors can influence ecological values directly, or through effects on the types, amount and spatial patterns of biological legacies present in early successional forest. We present a conceptual model highlighting the inter-relationships between these factors and illustrate its use through a detailed case study.Strategies to improve the management of early successional forests include: (1) Identifying the species associated with post-disturbance environments and the reasons why they occur in such environments. (2) Understanding the types, numbers, and spatial patterns of biological legacies that remain after natural disturbance. (3) Identifying critical areas that should be excluded from logging or other human disturbance. (4) Limiting the extent of post-disturbance activities like salvage logging that undermine the ecological values of, and ecosystem processes in, early successional forests. And, (5) Balancing the relative amounts of early successional versus late successional forest in a given landscape or region to ensure that a variety of forest types are present at any given time, and that critical biological legacies are retained. Paradoxically, ensuring that landscapes support extensive areas of late successional forest is critical so that future early successional forests are not devoid of the biological legacies necessary for ecosystem function and recovery.

Cultivable fungi from deep-sea oil reserves in the Gulf of Mexico: Genetic signatures in response to hydrocarbons

The estimation of oil spill effects on marine ecosystems is limited to the extent of our knowledge on the autochthonous biota. Fungi are involved in key ecological marine processes, representing a major component of post-spill communities. However, information on their functional capacities remains lacking. Herein we analyzed cultivable fungi from sediments in two oil-drilling regions of the Gulf of Mexico for their ability to tolerate and use hexadecane and 1-hexadecene as the sole carbon sources; and to evaluate gene expression profiles of key hydrocarbonoclastic taxa during utilization of these hydrocarbons. The isolated fungi showed differential sensitivity patterns towards the tested hydrocarbons under three different concentrations. Remarkably, six OTUs (Aureobasidium sp., Penicillium brevicompactum, Penicillium sp., Phialocephala sp., Cladosporium sp. 1 and 2) metabolized the tested alkane and alkene as the sole carbon sources, confirming that deep-sea fungal taxa are valuable genetic resources with potential use in bioremediation. RNA-seq results revealed distinctive gene expression profiles in the hydrocarbonoclastic fungus Penicillium sp. when using hexadecane and 1-hexadecene as the sole carbon sources, with up-regulation of genes involved in transmembrane transport, metabolism of six-carbons carbohydrates, and nitric oxide pathways.

Causes and consequences of inverse density-dependent territorial behaviour and aggression in a monogamous mammal.

Territoriality is an important process shaping population dynamics, and the defence of a territory is crucial for individuals to increase the duration of territory occupancy and, consequently, reproductive success. However, little is known about how the frequency of territory intrusions and subsequent territorial behaviours and aggression by territory owners are affected by external factors, such as population density. This is important because it can affect mate change (the replacement of one pair member) and dispersal, a key ecological process. The aim of this study was to investigate the behavioural and spatial response of territory owners to intruder pressure as a function of population density in a territorial, monogamous mammal, the Eurasian beaver (Castor fiber). Using a combination of GPS technology, scent experiments, camera trap data and tail scar observations from an individual-based long-term study, we investigated the factors influencing spatial movement patterns by territory owners in response to a simulated intruder and the factors affecting territory intrusions. We found consistent inverse density-dependent patterns in territorial behaviours and evidence of conspecific aggression. At lower densities, territory owners detected more simulated intrusions, showed more territorial reactions and experienced increased conspecific aggression as indicated by tail scars, suggesting increased intruder pressure. Inverse density-dependent territorial behaviour and aggression suggest a potential mechanistic link between inverse density-dependent natal dispersal and mate change. At low population densities, increased dispersal amplifies intruder pressure, leading to the observed increases in territorial behaviours, conspecific aggression and previously observed mate turnover, which in turn might increase natal dispersal. Our study demonstrates how population density can affect the behaviour and space use of individuals, which is important for territory occupancy and fitness.

Capturing the big picture of Mediterranean marine biodiversity with an end-to-end model of climate and fishing impacts

The Mediterranean Sea is one of the main hotspots of marine biodiversity in the world. The combined pressures of fishing activity and climate change have also made it a hotspot of global change amidst increasing concern about the worsening status of exploited marine species. To anticipate the impacts of global changes in the Mediterranean Sea, more integrated modelling approaches are needed, which can then help policymakers prioritize management actions and formulate strategies to mitigate impacts and adapt to changes. The aim of this study was to develop a holistic model of marine biodiversity in the Mediterranean Sea with an explicit representation of the spatial, multispecies dynamics of exploited resources subject to the combined influence of climate variability and fishing pressure. To this end, we used the individual-based OSMOSE model (Object-oriented Simulator of Marine ecOSystEms), including 100 marine species (fish, cephalopods and crustaceans) representing about 95% of the total declared catch, at a high spatial resolution (400 km2) and a large spatial scale (the entire Mediterranean basin) – the first time such a resolution and scale have been modelled. We then combined OSMOSE with the NEMOMED 12 physical model and the Eco3M-S biogeochemical low trophic level model to build the end-to-end model, OSMOSE-MED. We fitted OSMOSE-MED model with observed or estimated biomass and commercial catch data using a likelihood approach and an evolutionary optimization algorithm. The outputs of OSMOSE-MED were then verified against observed biomass and catch data, and compared with independent datasets (MEDITS data, diet composition and trophic levels). The model results – at different hierarchical levels, from individuals to the scale of the ecosystem – were consistent with current knowledge of the structure, functioning and dynamics of the ecosystems in the Mediterranean Sea. While the model could be further improved in future iterations, all the modelling steps – the comprehensive representation of key ecological processes and feedback, the selective parameterization of the model, and the comparison with observed data in the validation process – strengthened the predictive performance of OSMOSE-MED and thus its relevance as an impact model to explore the future of marine biodiversity under scenarios of global change. It is a promising tool to support ecosystem-based fishery management in the Mediterranean Sea.

Light environment drives the shallow‐to‐mesophotic coral community transition

AbstractLight quality is a crucial physical factor driving coral distribution along depth gradients. Currently, a 30 m depth limit, based on SCUBA regulations, separates shallow and deep mesophotic coral ecosystems (MCEs). This definition, however, fails to explicitly accommodate environmental variation. Here, we posit a novel definition for a regional or reef‐to‐reef outlook of MCEs based on the light vs. coral community–structure relationship. A combination of physical and ecological methods enabled us to clarify the ambiguity in relation to the mesophotic definition. To characterize coral community structure with respect to the light environment, we conducted wide‐scale spatial studies at five sites along shallow and MCEs of the Gulf of Eilat/Aqaba (0–100 m depth). Surveys were conducted by technical‐diving and drop‐cameras, in addition to one year of light spectral measurements. We quantify two distinct coral assemblages: shallow (<40 m) and MCEs (40–100 m), exhibiting markedly different relationships with light. The depth ranges and morphology of 47 coral genera were better explained by light than depth, mainly, due to photosynthetically active radiation (PAR) and ultraviolet radiation (UVR) (1% at 76 and 36 m, respectively). Branching coral species were found mainly at shallower depths, that is, down to 36 m. Among the abundant upper‐mesophotic specialist corals, Leptoseris glabra, Euphyllia paradivisa, and Alveopora spp. were found strictly between 40 and 80 m depth. The only lower‐mesophotic specialist, Leptoseris fragilis, was found deeper than 80 m. We suggest that shallow coral genera are light‐limited below a level of 1.25% surface PAR and that the optimal PAR for mesophotic communities is at 7.5%. This study contributes to moving MCE ecology from a descriptive phase into identifying key ecological and physiological processes structuring MCE coral communities. Moreover, it may serve as a model enabling the description of a coral zonation worldwide on the basis of light quality data.

Responses and feedback of the Tibetan Plateau’s alpine ecosystem to climate change

The Tibetan Plateau, also known as the “third pole of the Earth”, houses a diverse array of alpine-ecosystem types and serves as a critical ecological security shield for China and even for many other regions of Asia. In recent decades, the rapid climate change in the Tibetan Plateau has led to profound changes in the structure and functioning of its ecosystem. Such changes in the ecosystem of the Tibetan Plateau can not only profoundly impact the environment of the high plateau itself but also extend significant influence over that of surrounding areas. With the continuous growth of data obtained via long-term in situ monitoring, manipulative experiments, satellite remote sensing, and model simulations, scientists have recently made significant advances in the research on the responses and feedback of the Tibetan Plateau’s alpine ecosystem to climate change. Aiming to identify knowledge gaps and to stimulate future research, we provide a comprehensive review of past efforts to understand how climate change has impacted the Tibetan Plateau’s alpine ecosystem, which in turn also provides feedback to the climate. In particular, we focus on the impacts of climate change on the structure and functioning of the ecosystem, including vegetation phenology, treeline position, species biodiversity, ecosystem productivity, and carbon sink, along with feedback involving vegetation changes to the regional climate and hydrology through local and teleconnected biophysical loops. A number of key findings emerge based on cumulative knowledge from old as wells as recent researches. (1) Climate warming during the past several decades has significantly advanced spring vegetation phenology in the Tibetan Plateau. (2) Further, warming has significantly shifted the treeline upward with varying amplitudes that may have been regulated by other factors such as precipitation and interspecific interactions. (3) The plant-community structure of the Tibetan Plateau’s alpine steppe ecosystem is sensitive to climate change, with climate warming considerably reducing its biodiversity and species abundance. However, for the alpine-meadow ecosystem, the impact of climate warming on the diversity and species abundance is still inconclusive. (4) Furthermore, warming has significantly increased vegetation productivity, which can consequently lead to an enhanced carbon sink. Such warming-induced carbon accumulation by vegetation is higher in alpine meadows than in alpine steppes. However, the effect of climate change on soil carbon stock remains highly uncertain mainly because of the high spatial heterogeneity of soil properties and lack of information regarding deep-layer soil processes. (5) Warming-induced vegetation greening of the Tibetan Plateau provides an overall cooling effect countering the local warming and modulates the local and far-reaching precipitation patterns through teleconnected feedback to the East Asian monsoon. In particular, the modeling results suggest that this greening trend of the Tibetan Plateau increases precipitation in South China but reduces precipitation in the region between the Yellow and Yangtze Rivers. Even with the recent significant progress in the study on the ecosystem-climate interaction in the Tibetan Plateau, many knowledge gaps remain. These gaps provide opportunities for future research, which needs to expand and optimize long-term ecological observation networks to improve the understanding of key ecological processes and deepen the comprehension of the response and acclimation mechanisms of the alpine ecosystem under the influence of climate warming. The knowledge enhancement thus obtained will provide important guidelines for improving ecosystem management and safeguarding the ecological security in the Tibetan Plateau.

Population density of the spur-thighed tortoise Testudo graeca declines after fire in north-western Africa.

Fire is a key ecological process in several biomes worldwide. Over recent decades, human activities (e.g. rural abandonment, monoculture plantations) and global warming are magnifying the risk of fire, with changes in fire intensity and frequency. Here, we offer the first study that examines the impact of fire on the spur-thighed tortoise Testudo graeca living in a native cork oak forest and pine plantation in north-western Africa. A total of 44 transects (22 burnt and 22 unburnt) were sampled at 8 sites affected by fires of natural cork oak forest and pine plantation with 8 surveys per site in 2015–2017 (264 hours of sampling effort). Tortoise densities were estimated with line-transect distance sampling. The detection probability of tortoises was higher in burnt (0.915) than unburnt (0.474) transects. The density of tortoises was negatively associated with elevation and declined with fire by c. 50% in both forest types. The negative response of T. graeca to fire should be considered in conservation planning of this species in north-western Africa in a future scenario of changes in fire regime.

Intraspecific diversity affects stress response and the ecological performance of a cosmopolitan aquatic fungus

Abstract Fungi play an important role in organic matter turnover and ensure key ecosystem services in freshwaters. The relationships between intraspecific fungal diversity and key ecological processes remain largely unknown. We examined the effects of intraspecific diversity of Articulospora tetracladia, a cosmopolitan fungal decomposer thriving on plant detritus in streams. Alder leaves were inoculated with 1 or mixtures of 2–8 fungal strains for 35 d, and leaf litter decomposition and fungal reproduction were quantified in the presence and absence of 2 mg L−1 of cadmium (Cd), a common stressor in polluted streams. Intraspecific diversity and identity affected fungal reproduction, but not leaf decomposition. Under metal stress, leaf decomposition slightly increased with intraspecific diversity. Fungal reproduction increased with intraspecific diversity and was greater in mixed assemblages, either in the absence or presence of Cd. Effect size of intraspecific diversity was higher under Cd stress for fungal reproduction, but no differences were found for leaf mass loss, with or without metal. The impacts of intraspecific diversity loss may jeopardize fungal survival and fungal functions, namely microbial leaf decomposition and leaf litter condition for invertebrate shredders in streams, particularly under metal stress.

Social-Ecological Functional Types: Connecting People and Ecosystems in the Argentine Chaco

Sustainability science recognizes the importance of the integrated assessment of the ecological and social systems in land-use planning. However, most studies so far have been conceptual rather than empirical. We developed a framework to characterize the social-ecological systems heterogeneity according to its functioning through the identification of social–ecological functional types (SEFT). The SEFT framework builds on the plant, ecosystem and agent functional type approaches, taking a step forward to integrate the dimensions of social–ecological systems into an operational product to characterize administrative units in a hierarchical way. To illustrate this novel framework, we described the heterogeneity of SEFT in the Argentine Chaco by clustering administrative entities. This area is a global deforestation hotspot and has diverse social actors that harness ecosystem services in multiple, and sometimes contrasting and conflictive, ways which determines an urgent need for land-use planning. We combined data from national census and remote sensing to identify SEFT by clustering census tracts based on 17 input variables that integrate key human, ecological and interaction processes across landscapes. We identified three classes and eight subclasses of SEFT. Ecological variables defined the first level of heterogeneity (classes), while human variables and the variables of interactions between the human and ecological components defined a second level of heterogeneity (subclasses). The degree of anthropization and mean annual productivity were important variables to explain the first two axes in the ordination (32% of the total variance). This framework offers a conceptually novel and comprehensive approach to understand the spatial heterogeneity of social–ecological systems functioning, which could play a pivotal role to support conservation or land-use planning in rural areas.

Ecosystem-based reference points under varying plankton productivity states and fisheries management strategies

Abstract In the context of ecosystem-based fisheries management, which should consider changing and uncertain environmental conditions, the development of ecosystem-based biological reference points (EBRPs) to account for important multi-species (MS) interactions, fishery operations, and climate change, is of paramount importance for sustainable fisheries management. However, EBRPs under varying plankton productivity states and fisheries management strategies are seldom developed, and the ecosystem effects of these changes are still largely unknown. In this study, ecosystem-based FMSY (fishing mortality rate at MSY) values were estimated within an end-to-end ecosystem model (OSMOSE) for three focused fish species (Pacific Herring, Clupea pallasii; Pacific Cod, Gadus macrocephalus; Lingcod, Ophiodon elongatus) under three plankton productivity states of differing plankton biomass at high, current, and low levels. In addition, ecosystem effects were compared across different plankton productivity and fisheries management strategies with the latter consisting of two fishery scenarios (i.e. single-species-focused (SS) and MS-focused), various fishing mortality rates, and two harvest policies (with and without harvest control rules, HCRs). Main findings of this study include: (i) plankton productivity change affected the values of ecosystem-based FMSY, which increased as plankton productivity states changed from low to high plankton biomass; (ii) ecosystem-based FMSY for Pacific Herring and Pacific Cod stocks increased when fishery scenarios shifted from SS-focused to MS-focused; (iii) fisheries management incorporating HCR yielded more stable system catch and system biomass; and (iv) high plankton biomass combined with fisheries management using HCR could maintain stable ecosystem production and sustainable fisheries. Based on our findings, we highlight possible adaptive fisheries management strategies in the face of future climate and ocean changes. Overall, EBRPs complement SS stock assessments by incorporating key ecological processes and ecosystem properties, thus providing supporting evidence for better incorporation of ecosystem considerations into scientific advice for sustainable fisheries management.