309 research outputs found

    Asymmetric warming significantly affects net primary production, but not ecosystem carbon balances of forest and grassland ecosystems in northern China

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    We combine the process-based ecosystem model (Biome-BGC) with climate change-scenarios based on both RegCM3 model outputs and historic observed trends to quantify differential effects of symmetric and asymmetric warming on ecosystem net primary productivity (NPP), heterotrophic respiration (Rh) and net ecosystem productivity (NEP) of six ecosystem types representing different climatic zones of northern China. Analysis of covariance shows that NPP is significant greater at most ecosystems under the various environmental change scenarios once temperature asymmetries are taken into consideration. However, these differences do not lead to significant differences in NEP, which indicates that asymmetry in climate change does not result in significant alterations of the overall carbon balance in the dominating forest or grassland ecosystems. Overall, NPP, Rh and NEP are regulated by highly interrelated effects of increases in temperature and atmospheric CO2 concentrations and precipitation changes, while the magnitude of these effects strongly varies across the six sites. Further studies underpinned by suitable experiments are nonetheless required to further improve the performance of ecosystem models and confirm the validity of these model predictions. This is crucial for a sound understanding of the mechanisms controlling the variability in asymmetric warming effects on ecosystem structure and functioning

    The Chord-Normalized Expected Species Shared (CNESS)-distance represents a superior measure of species turnover patterns

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    1. Measures of β-diversity characterizing the difference in species composition between samples are commonly used in ecological studies. Nonetheless, commonly used dissimilarity measures require high sample completeness, or at least similar sample sizes between samples. In contrast, the Chord-Normalized Expected Species Shared (CNESS) dissimilarity measure calculates the probability of collecting the same set of species in random samples of a standardized size, and hence is not sensitive to completeness or size of compared samples. To date, this index has enjoyed limited use due to difficulties in its calculation and scarcity of studies systematically comparing it with other measures. 2. Here, we developed a novel R function that enables users to calculate ESS (Expected Species Shared)-associated measures. We evaluate the performance of the CNESS index based on simulated datasets of known species distribution structure, and compared CNESS with more widespread dissimilarity measures (Bray-Curtis index, Chao-Sørensen index, and proportionality based Euclidean distances) for varying sample completeness and sample sizes. 3. Simulation results indicated that for small sample size (m) values, CNESS chiefly reflects similarities in dominant species, while selecting large m values emphasizes differences in the overall species assemblages. Permutation tests revealed that CNESS has a consistently low CV (coefficient of variation) even where sample completeness varies, while the Chao-Sørensen index has a high CV particularly for low sampling completeness. CNESS distances are also more robust than other indices with regards to undersampling, particularly when chiefly rare species are shared between two assemblages. 4. Our results emphasize the superiority of CNESS for comparisons of samples diverging in sample completeness and size, which is particular important in studies of highly mobile and species-rich taxa where sample completeness is often low. Via changes in the sample size parameter m, CNESS furthermore cannot only provide insights into the similarity of the overall distribution structure of shared species, but also into the differences in dominant and rare species, hence allowing additional, valuable insights beyond the capability of more widespread measures

    Estimating the number of species shared by incompletely sampled communities

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    There are numerous ways to estimate the true number of species in a community based on incomplete samples. Nonetheless, comparable approaches to estimate the number of species shared between two incompletely sampled communities are scarce. Here, we introduce the ‘total expected species shared' (TESS) measure and provide the R function for its calculation. Based on parametric asymptotic models, TESS provides estimates of the true number of species shared between incompletely sampled communities based on abundance data. We compare TESS results with abundance-based non-parametric methods in terms of precision and accuracy, using different simulated sampling scenarios. We further calculate TESS using an empirical dataset, highlighting changes in accuracy and precision with increasing sample size. We also demonstrate how TESS values can be combined with species richness estimators in turnover estimates using traditional β-diversity indices. Our results show that mean values of TESS reliably approximate the true shared species number for varying sample completeness scenarios, with both accuracy and precision increasing with increasing sample completeness. Overall, we demonstrate the viability of TESS in estimations of the true number of species shared between two incompletely sampled communities. We also stress the importance of a sufficient sample size for the accuracy of estimates – requiring sampling designs that carefully balance sampling effort per site with the number of sampling sites

    Diverse locations and a long history: historical context for urban leopards (Panthera pardus) in the early Anthropocene from Seoul, Korea

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    While the urban landscapes of the early Anthropocene may appear hostile to large carnivores, humans and leopards (Panthera pardus) are known to co-inhabit major urban centres like Mumbai (India), Nairobi (Kenya) and Johannesburg (South Africa). We provide evidence that the presence of leopards in urban landscapes is not, however, a new phenomenon and has occurred repeatedly over the early history of the Anthropocene. Using records of Amur leopards (P. p. orientalis) in Seoul, Korea, at the end of the 19th century, a capital city and major urban centre with a high human population density, we explore socio-cultural, political and ecological factors that may have facilitated human-leopard co-occurrence in an urban landscape and the factors that eventually led to the leopards' extirpation. We suggest that, in the absence of unsustainable levels of persecution by humans, leopards are able to persist in urban landscapes which contain small patches of dense vegetation and have sufficient alternative food supplies. In light of the continued expansion of urban landscapes in the 21st century and increasing conservation focus on the presence of large carnivore populations there, this paper provides historical context to human co-existence with leopards in urban landscapes during the Anthropocene – and what we can learn from it for the future

    Nocturnal pollinators strongly contribute to pollen transport of wild flowers in an agricultural landscape

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    Dramatic declines in diurnal pollinators have created great scientific interest in plant–pollinator relationships and associated pollination services. Existing literature, however, is generally focused on diurnal pollinating insect taxa, especially on Apidae (Hymenoptera) and Syrphidae (Diptera) pollinators, while nocturnal macro-moths that comprise extremely species-rich flower-visiting families have been largely neglected. Here, we report that in agricultural landscapes, macro-moths can provide unique, highly complex pollen transport links, making them vital components of overall wild plant–pollinator networks in agro-ecosystems. Pollen transport occurred more frequently on the moths' ventral thorax rather than on their mouthparts that have been traditionally targeted for pollen swabbing. Pollen transport loads suggest that nocturnal moths contribute key pollination services for several wild plant families in agricultural landscapes, in addition to providing functional resilience to diurnal networks. Severe declines in richness and abundance of settling moth populations highlight the urgent need to include them in future management and conservation strategies within agricultural landscapes

    Open-canopy ponds benefit diurnal pollinator communities in an agricultural landscape: implications for farmland pond management

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    1. Declines in pollinating invertebrates across intensively cultivated landscapes linked to reductions in flower-rich habitats constitute a key threat to biodiversity conservation and the provision of ecosystem services. Over recent decades, many ponds in agricultural landscapes have become overgrown with woody vegetation, resulting in heavily shaded, flower-poor pond basins and margins. Restoration of farmland ponds through removal of sediment and encroaching woody vegetation (canopy management) from pond margins greatly enhances freshwater biodiversity. Nevertheless, the consequences of pond management for pond-margin plants and pollinating insects remain poorly understood. Here, we studied these effects for ponds in Norfolk, eastern England. 2. We compared richness, abundance and composition of pollinating insects (hymenopterans and syrphids) and insect-pollinated plant communities between open-canopy pond systems subjected to either (i) long-term regular management of woody vegetation or (ii) recent restoration by woody vegetation and sediment removal with those communities at (iii) ponds dominated by woody vegetation. 3. Canopy management increased the richness and abundance of pollinators and insect-pollinated plants. Pollinator richness and abundance was best explained by improvements in flower resources at open-canopy ponds. Management most strongly influenced hymenopteran communities. 4. Ponds represent important semi-natural habitats for insect-pollinated plant and pollinator communities in farmland. To enhance food resources, diversity and abundance of diurnal pollinators, conservation management at ponds should aim for mosaics of ponds at different successional stages with a high proportion of early successional open-canopy ponds. Agricultural ponds are emerging as important habitats not only for aquatic biodiversity, but also for terrestrial species, thus warranting their prioritisation in future agri-environment schemes

    Sustainability Dynamics of Traditional Villages: A Case Study in Qiannan Prefecture, Guizhou, China

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    Rapid urbanization has greatly changed traditional villages in rural areas of China. This paper aims to assess sustainability and obtain its spatio–temporal dynamics, analyze the cause of sustainability changing conditions, and offer suggestions on the sustainable development of traditional villages. We integrated human disturbances into a minimum cumulative resistance (MCR) model based on land use, landscape patterns, and ecosystem service (ES) provision in order to evaluate the sustainability dynamics of traditional villages between 1995 and 2015 in the Qiannan Prefecture, China. The results showed that pronounced declines in sustainability were limited to the northern and eastern regions, where the degradation of forest ecosystems and the rapid increase in construction land have resulted in landscape fragmentation and ES decline. We suggest that scientific land use development plans and ecological restoration should be implemented to protect the ecosystem and improve the sustainability of traditional villages in Qiannan Prefecture

    Does China’s increasing coupling of ‘urban population’ and ‘urban area’ growth indicators reflect a growing social and economic sustainability?

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    Over the last four decades, China has experienced rapid parallel economic development and urbanization, leading to internal mass -migrations of its people from increasingly marginalized rural areas to urban centers where job opportunities and wealth are now concentrated. We compare the relative temporal growth trends in population-related and land-(i.e., area-) related urbanization systems to evaluate China's urbanization in the context of the ‘New-Type’ Urbanization Program (2014–2020). Based on coupling coordination models, we observed that the two systems were overall slightly decoupled since spatial urban expansion commonly outgrew urban population growth, but the degree of coordination between the two parameters was increasing. Employing exploratory spatial data analysis, we revealed that a high degree of coupling coordination has spread from Eastern to Western provinces. Urban planning and land policies have contributed to an increasing urban vegetation cover and the control of excessive urban land expansions. While China's urbanization appears to have become increasingly sustainable due to the increasing degree of coupling coordination between its subsystems, ongoing urban expansions require strong oversight to limit the environmental impacts of the country's sprawling mega-cities

    Local category-specific gamma band responses in the visual cortex do not reflect conscious perception

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    Which neural processes underlie our conscious experience? One theoretical view argues that the neural correlates of consciousness (NCC) reside in local activity in sensory cortices. Accordingly, local category-specific gamma band responses in visual cortex correlate with conscious perception. However, as most studies manipulated conscious perception by altering the amount of sensory evidence, it is possible that they reflect prerequisites or consequences of consciousness rather than the actual NCC. Here we directly address this issue by developing a new experimental paradigm in which conscious perception is modulated either by sensory evidence or by previous exposure of the images while recording intracranial EEG from the higher-order visual cortex of human epilepsy patients. A clear prediction is that neural processes directly reflecting conscious perception should be present regardless of how it comes about. In contrast, we observed that although subjective reports were modulated both by sensory evidence and by previous exposure, gamma band responses solely reflected sensory evidence. This result contradicts the proposal that local gamma band responses in the higher-order visual cortex reflect conscious perception

    Disentangling effects of abiotic factors and biotic interactions on cross-taxon congruence in species turnover patterns of plants, moths and beetles

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    High cross-taxon congruence in species diversity patterns is essential for the use of surrogate taxa in biodiversity conservation, but presence and strength of congruence in species turnover patterns, and the relative contributions of abiotic environmental factors and biotic interaction towards this congruence, remain poorly understood. In our study, we used variation partitioning in multiple regressions to quantify cross-taxon congruence in community dissimilarities of vascular plants, geometrid and arciinid moths and carabid beetles, subsequently investigating their respective underpinning by abiotic factors and biotic interactions. Significant cross-taxon congruence observed across all taxon pairs was linked to their similar responses towards elevation change. Changes in the vegetation composition were closely linked to carabid turnover, with vegetation structure and associated microclimatic conditions proposed causes of this link. In contrast, moth assemblages appeared to be dominated by generalist species whose turnover was weakly associated with vegetation changes. Overall, abiotic factors exerted a stronger influence on cross-taxon congruence across our study sites than biotic interactions. The weak congruence in turnover observed particularly between plants and moths highlights the importance of multi-taxon approaches based on groupings of taxa with similar turnovers, rather than the use of single surrogate taxa or environmental proxies, in biodiversity assessments
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