Decline In Richness Research Articles

Fagus diversification in China in relation to East Asian monsoon evolution

When and how the extraordinary species diversity in subtropical East Asia formed is intensely debated, and the available evidence is often inconsistent. In this study, we evaluate the effects of pre- and post- Quaternary events on the evolutionary and biogeographic history of Chinese beech (Fagus species that now occur in China) to gain new insights into the historical establishment and future fate of the East Asian subtropical forest (EASF). A series of approaches and datasets were used to reconstruct biogeographic and evolutionary history of the Chinese beech. They include phylogeography based on the polymorphisms of the complete chloroplast genomes, species distribution models, and a large palaeobiogeographic dataset including 59 pre-Quaternary fossil records, 296 Quaternary fossil records and 3515 modern pollen records. Our multidisciplinary approach suggests that (i) Chinese beech has dispersed to subtropical East Asia and diversified in the early Miocene when the Asian monsoon (AM) intensified; (ii) the last post-glacial warming resulted in limited poleward displacement but significant contraction at southern and lower elevations; (iii) the poleward dispersal of Chinese beech was limited by drought in the early growing season in temperate China, controlled by the East Asian summer monsoon. Our results support the hypothesis that the establishment of the EASF is closely related to the evolution of the AM. More importantly, we suggest that with continued climate warming (e.g., during the last post-glacial period or under current climate change), the monsoon probably hindered rather than promoted the persistence of deciduous beech species, resulting in a decline in species richness.

Response of the Patagonian floras to climatic cooling during Oligocene−Miocene transition and the expansion of Antarctic glaciation

Pulses of Antarctic ice sheet expansion and associated climatic deterioration are thought to have driven major shifts in the world's flora during the Cenozoic Era. However, the rarity of fossils from well-constrained sedimentary strata in high palaeolatitudes makes it difficult to explore to these vegetation shifts directly. In this study, we infer changing patterns of floristic richness through the Oligocene−Miocene cooling event (∼23 Ma), based on analysis of terrestrial palynological samples in the radiometrically-constrained sediments of the Río Guillermo Formation of southern Patagonia. Our fossil assemblages include plant families typical of modern Magellanic subpolar forests such as Nothofagaceae, Podocarpaceae, Araucariaceae, and Myrtaceae. Adjusted for sample completeness (or coverage), our floristic richness estimates are, on average, higher than those from modern subpolar forests yet considerably lower than any other Paleogene or Neogene palynological records published elsewhere from the continent. The transient Oligocene−Miocene cooling episode, whose effects were probably intensified in southern Patagonia due to its close proximity to the glaciated Antarctic Peninsula, may have contributed to the steep decline in floristic richness. We infer that most Gondwanan plant relicts that survived across the Oligocene−Miocene transition endured through subsequent Neogene climatic fluctuations and contribute to present-day Magellanic subpolar forests. Our study highlights how precisely-dated fossil assemblages and robust diversity methods can be used to track biodiversity shifts in response to past climate change.

Using high-throughput sequencing to investigate summer truffle consumption by chipmunks in relation to retention forestry

Intensive management of forests for wood modifies forest biodiversity, affecting the composition of plant and animal communities as well as microorganisms such as bacteria and fungi. Ectomycorrhizal fungi (EMF) form mutualistic relationships with trees, but there is evidence that the abundance and diversity of EMF declines under intensive forest management. The dispersal of some EMF, including that of truffles, depends on small mammals consuming their fruiting bodies and dispersing spores through feces. To better understand provisioning of this ecosystem service within intensively managed forests, we applied high-throughput, DNA amplicon sequencing to scat collected from Townsend’s chipmunks (Neotamias townsendii) inhabiting retention patches in recently clearcut-conifer stands. Across two summers, we collected 165 chipmunk scat samples from 43 clearcut-conifer stands in the Pacific Northwest (USA). We identified 81 truffle species representing 16 families, which included many rare and uncommon taxa. Retention patch sizes varied from 9 to 222 trees (0.002–0.83 ha) but we did not detect an effect of retention patch size on the richness of truffles in chipmunk scat samples. However, truffle richness was slightly higher in scat samples collected from chipmunks in retention patches compared to individuals sampled in adjacent clearcuts. Furthermore, the abundance of certain truffle species in chipmunk scat varied in relation to retention patch size and location (riparian or upland), suggesting retention forestry practices may influence truffle community composition. Throughout the sampling season, we detected a 44% decline in truffle species richness and a significant reduction in abundance (i.e., sequence reads) for > 50% of common truffle taxa. Our application of high-throughput sequencing of scat effectively captured variation in truffle species consumption by chipmunks. Our results confirm that common small mammals play an important role in the dispersal of EMF across recently logged forests (<8 years since harvest) and indicate that retaining relatively small (∼10 tree) green-tree patches may promote truffle dispersal by providing small mammal habitat.

Climate-driven loss of taxonomic and functional richness in Brazilian Atlantic Forest anurans

Climate change is one of the key drivers of the dramatic erosion of global biodiversity. Poikilothermic organisms, such as amphibians, are particularly prone to alterations in temperature and precipitation and are therefore expected to be severely impacted by global climate change. We evaluated: i) the potential effects of climate change on taxonomic and functional richness of amphibians in the Atlantic Forest of Brazil, and ii) tested whether forest-dependent and open area species responded differently to climatic stressors. We applied an ensemble forecasting approach using point locality data to establish predictive maps of taxonomic and functional richness for different IPCC AR5 scenarios with two Representative Concentration Pathway trajectories (RCP 4.5 and RCP 8.5) at two temporal projections (2050 and 2070). A significant decline in both taxonomic and functional richness of Atlantic Forest amphibians is expected over the coming decades under the evaluated climate scenarios. The core areas projected to maintain significantly high anuran richness in both components were in coastal high-altitude localities. We found negative effects (losses) to be more pronounced for taxonomic richness. Model outcomes indicate significant losses in both forest and open area species. A few remaining high-altitude sites will then play an important role as potential climatic refuges to safeguard anuran diversity, requiring a dynamic landscape approach as conservation strategy.

Linking soil phosphorus fractions to abiotic factors and the microbial community during subalpine secondary succession: Implications for soil phosphorus availability

Soil phosphorus (P) availability plays a critical role in sustaining ecosystem productivity during vegetation succession. However, our understanding of the factors driving soil P dynamics along this process, particularly in cold regions like the Tibetan Plateau, remains poorly limited. To address this, we sampled soils from four vegetation types along a secondary successional gradient (grassland → shrubland → secondary forests → primary forests) in the subalpine region of the Tibetan Plateau. Our aim was to investigate the drivers of soil P dynamics along the successional gradient. We assessed soil P dynamics by analyzing sequential soil P fractions using a modified Hedley fractionation procedure. Our results revealed significant increases in the concentrations of total inorganic P (Pi) (58.3%), Resin-Pi (93.5%), NaHCO3-Pi (63.1%), and HCl-Pi (81.7%) along the successional gradient. In contrast, we did not observe any significant changes in total P or residual P concentration along the successional gradient. Soil organic P (Po; dominated by c. HCl-Po) initially increased by 16.7% but then exhibited a subsequent decrease by 37.5% during secondary succession. The observed increase in Pi was found to be linked to the accrual in soil organic carbon during vegetation succession. Conversely, the decrease in soil Po concentration was associated with the decline in vegetation richness and fungal richness along the successional gradient. Additionally, we identified the increased relative abundance of Basidiomycota, Mortierella and Russula as potential contributors to the decrease in the soil Po concentration in the late, mid, and late successional stages, respectively. Overall, our study underscores the joint influence abiotic factors and the microbial community on soil P dynamics during vegetation succession. These findings provide valuable insights into the processes influencing soil nutrient availability in cold regions such as the Tibetan Plateau.

Human activities and environmental variables drive infaunal community structure and functioning in West African mangroves

In West African tropical estuaries, such as the Saloum Delta (Senegal), mangroves provide specific socio-economic functions including various natural food resources for local human populations. Mangrove-habitat loss is therefore of great concern, in terms of conservation and management, and highlights the need to study West African mangrove under human-induced pressures. Based on data from 2007 to 2008, this study aimed to establish a conditions report for two of the main Southern West Senegal mangroves areas: the Sine Saloum and the Petite Côte. We assessed the influence of environmental variables and human-induced pressures (i.e. shellfish harvesting and heavy metals (potentially toxic elements, PTEs)) on infaunal community structure and functions through trait-based approaches.Reflecting for example changing seasons and hypersaline events, the Saloum environmental variables and their temporal dynamics greatly impacted infaunal communities in the subtidal zone. In the intertidal area, closer to anthropogenic disturbances, pressures related to human activities took precedence over environmental variables in explaining infaunal community structure. Shellfish harvesting resulted in a significant decrease (p < 0.05) in total macrofaunal abundance (933.79 ± 626.34 ind m−2 in unexploited stations compared to 140.92 ± 71.99 ind m−2 in exploited stations; mean ± SE) in addition to a decline in biomass and taxonomic richness. Intertidal species composition was affected by both shellfish harvesting and PTEs. PTEs were also associated with a significant decrease in functional diversity and particularly with a change in macrofaunal living habits. The combination of an RLQ and fourth-corner analysis highlighted a significant association between feeding modes and sediment grain size in both tidal areas.This study provides a needed deeper understanding of the unintended effects of human activities on infaunal communities and their functioning, in a highly valuable system for humans. Pinpointed factors driving infaunal community structure and functions provide important insights for future research, as well as reference points for the implementation of management measures.

Human-modified landscapes driving the global primate extinction crisis.

The world's primates have been severely impacted in diverse and profound ways by anthropogenic pressures. Here, we evaluate the impact of various infrastructures and human-modified landscapes on spatial patterns of primate species richness, at both global and regional scales. We overlaid the International Union for the Conservation of Nature (IUCN) range maps of 520 primate species and applied a global 100 km2 grid. We used structural equation modeling and simultaneous autoregressive models to evaluate direct and indirect effects of six human-altered landscapes variables (i.e., human footprint [HFP], croplands [CROP], road density [ROAD], pasture lands [PAST], protected areas [PAs], and Indigenous Peoples' lands [IPLs]) on global primate species richness, threatened and non-threatened species, as well as on species with decreasing and non-decreasing populations. Two-thirds of all primate species are classified as threatened (i.e., Critically Endangered, Endangered, and Vulnerable), with ~86% experiencing population declines, and ~84% impacted by domestic or international trade. We found that the expansion of PAST, HFP, CROP, and road infrastructure had the most direct negative effects on primate richness. In contrast, forested habitat within IPLs and PAs was positively associated in safeguarding primate species diversity globally, with an even stronger effect at the regional level. Our results show that IPLs and PAs play a critical role in primate species conservation, helping to prevent their extinction; in contrast, HFP growth and expansion has a dramatically negative effect on primate species worldwide. Our findings support predictions that the continued negative impact of anthropogenic pressures on natural habitats may lead to a significant decline in global primate species richness, and likely, species extirpations. We advocate for stronger national and international policy frameworks promoting alternative/sustainable livelihoods and reducing persistent anthropogenic pressures to help mitigate the extinction risk of the world's primate species.

Changes in the wild bee community (Hymenoptera: Apoidea) over 100 years in relation to land use: a case study in a protected steppe habitat in Eastern Austria

The wild bee community of a sand steppe habitat in Eastern Austria was surveyed in the years 2018 and 2019, complemented with historical data from over 100 years, and analyzed in relation to land use change. The mapping of land use categories was based on historical aerial photographs and orthophotos. Changes in bee community composition were analyzed by a multivariate statistical approach and took ecological traits into account (lecty, nesting type, habitat requirements, flight period, parasitism). In total, 310 bee species were recorded in the area, with the oldest records dating back to 1882. The bee species composition differed significantly among four defined time periods. Across the two most intensively sampled time periods (1931–1966 vs 2001–2021), a decline in species richness of over 50% was observed. We observed a disproportionally high decline of steppe- and sand-associated species, and a distinct shift from ground nesting species to above-ground nesting species. The area covered with woods increased from 1966 to 2018, while the total area covered with grassland and fallows decreased slightly between 1966 and 1994. The oligolectic species assemblage was specialized on Dipsacaceae, Brassicaceae and Fabaceae in the two earlier periods, and on Asteraceae and specifically on Carduoideae during the two later ones.Implications for insect conservationstronger reference to historic land management practices as short time periods of intensive grazing and small-scaled, staggered mowing would be desirable to improve the habitat quality. More drastic measures, such as removal of the topsoil in some parts and changes in the landscape re-establishing exposure to wind erosion, might be necessary, if the area is to be fully restored to the condition it was in a century ago.

Are the same factors determining biodiversity in cities across different regions? Comparing drivers of urban bird richness patterns in Southern Asia vs. Western Europe

AbstractAccording to general urban ecological understanding, bird species richness declines in highly urban areas due to the increasing extent of built-up areas, and decreasing proportions of green areas. However, this hypothesis is mainly based on studies conducted in cities located in the Global North and rarely in the Global South. We aimed to assess whether existing conceptual understandings of drivers of bird species richness patterns within cities are similar across different regions, specifically Southern Asia (in the Global South) vs. Western Europe (in the Global North). Using avian occurrence data drawn from GBIF (gbif.org), we estimated resident bird species richness in 943 selected grid cells (each cell corresponding to approximately 1 km2 area) distributed in 24 cities, 13 in Southern Asia and 11 in Western Europe. We applied generalised linear mixed models to relate resident bird richness with different explanatory variables of gradients of urbanisation, habitat and climatic factors using the selected grid cells as sampling units. Our results showed that bird richness declined with increasing human built-up and settlement extent (imperviousness) in both regions, but this relationship was stronger in Southern Asia compared to Western Europe. Bird richness also sharply declined in urban areas located far from inland waterbodies, but only in Southern Asia. Our findings suggest that high imperviousness drives bird richness decline, but this process appears to be more pronounced in regions where rapid urbanisation is ongoing. Urban planning integrating green spaces throughout cities is crucial in Southern Asia, as it is in Western Europe, to benefit both people and biodiversity.

Female-biased introductions produce higher predicted population size and genetic diversity in simulations of a small, isolated tiger (Panthera tigris) population

Isolation of wildlife populations represents a key conservation challenge in the twenty-first century. This may necessitate consideration of translocations to ensure population viability. We investigated the potential population and genetic trajectory of a small, isolated tiger (Panthera tigris) population in Thailand’s Dong Phayayen-Khao Yai forest complex across a range of scenarios. Using an individual-based, spatially-explicit population modelling approach, we simulate population and genetic trajectories and evaluate the relative impact of translocations from a related population. Population and genetic trajectories in our study were most sensitive to sex and number of individuals translocated and translocation frequency. Translocation of females produced consistently higher population, allelic richness, and heterozygosity compared to equal numbers of males. Despite population increases, declines in allelic richness and heterozygosity across simulations were stark, with simulations predicting a mean decline of allelic richness and heterozygosity of 46.5% and 53.5% without intervention, respectively. Translocations of four females every generation or every other generation were required to prevent substantial heterozygosity declines. While translocations could increase population size, they may fail to prevent long-term loss of genetic diversity in small populations unless applied frequently. This reinforces the importance of incorporating realistic processes of genetic inheritance and gene flow in modelling small populations.

Large‐scale sampling of beetle communities in Laos shows that conversion of natural forests into plantations leads to a decline in family richness and abundance

AbstractRapid economic development can pose a threat to the biodiversity of tropical countries. In Laos, this is manifested by the conversion of natural forests into plantations, even though this area is one of the biodiversity hotspots of Southeast Asia. Beetle communities can be good indicators of the impact of anthropogenic pressure on natural ecosystems. In this study, we analyzed for the first time a large‐scale inventory of Coleoptera to assess the ecological and anthropogenic drivers of beetle communities in Laos. We examined beetle communities (described at the family level) across the country, located in distinct habitat types, in order to understand the impact of the conversion of natural forest into plantations. We found that beetle abundance had declined in plantations compared to natural forests. At the same time, we observed fewer beetle families in plantations overall, but at the scale of sampling sites there was no difference in local richness compared to natural forests, suggesting a homogenization of beetle communities in anthropogenic habitats. Although results are certainly sensitive to our coarse classification of beetle specimens into families, the negative impact of the conversion of natural tropical forests into agriculture area can still be clearly demonstrated. Our findings highlight that it is possible to make use of unstructured large‐scale inventories to explore how beetle communities responds to landscape changes induced by human activities. We suggest that sampling beetle communities can be used as an ecological indicator to monitor anthropogenic impacts on tropical ecosystems.

Comparison of survey methods for fungi using metabarcoding and fruit body inventories in an altitudinal gradient.

Metabarcoding of environmental samples is nowadays an established method in biodiversity research. When it comes to studying fungal populations in various ecotypes, fruit body inventories are the traditional method to assess the diversity of fungal communities. In this study, both methods-metabarcoding of soil samples and a traditional fruit body inventory-were conducted on 144 sample plots in an altitudinal gradient in the Bavarian Forest (Germany) and the results were compared. Metabarcoding detected significantly more species than the traditional fruit body inventory. The majority of taxa recorded in the fruit body inventory belonged to the Basidiomycota, whereas in the metabarcoding data, the distribution of species between Basidiomycota and Ascomycota was approximately balanced. Species of several orders forming inconspicuous or hypogeous fruit bodies were detected only by metabarcoding, while several wood decomposers were recorded only in the fruit body inventory. The proportion of detected wood-colonising species with melanized spores was considerably higher with metabarcoding than with the fruit body inventory, where more than 70% of recorded wood-colonisers had hyaline spores. Based on the metabarcoding data, a decline of species richness with increasing altitude was evident, but this was not visible in the fruit body inventory data. Detrended correspondence analyses yielded similar results for relative species community similarities with both survey methods.

The Filtering Effect of Oil Palm Plantations on Potential Insect Pollinator Assemblages from Remnant Forest Patches

Extensive oil palm plantations worldwide are dependent on insect pollination, specifically by introduced African weevils (Elaidobius spp.). The effectiveness of these weevils has been questioned following poor pollination and yield loss in Malaysia. Indigenous thrip (Thysanoptera) species, and moths (Lepidoptera) in the genus Pyroderces, may also be pollinators of oil palm, while the role of bees (Hymenoptera) and flies (Diptera) is unknown. The potential of native pollinators remains uncertain because of the almost total clearing of forest habitat from oil palm landscapes. In this study, we investigate the value of small high conservation value (HCV) forests as sources of potential native insect pollinators of oil palm in northern Sarawak. We further examine the filtering effect of oil palm-dominated landscapes on the species assemblages of six potential pollinator insect orders: Blattodea, Coleoptera, Diptera, Hemiptera, Hymenoptera and Lepidoptera. Orders differed in both species composition and abundance between forest and oil palm plantations, with an average of 28.1% of species unique to oil palm. Oil palm presented a soft permeable boundary to Coleoptera, Hymenoptera and Lepidoptera. Their species richness and abundance differed little between habitats with distance, despite species turnover. In contrast, oil palm presented a harder boundary to Diptera with a decline in both species richness and abundance with distance into oil palm. The abundance of the oil palm weevil (Elaedobius kamerunicus) was low compared to the native dominants, but similar to levels displayed by native thrips that may be pollinators of oil palm. The functional diversity of well-known pollinator guilds—bees and flies—was similar in forest and oil palm, suggesting that potential pollinators may yet exist among native orders of insects. Contrary to the prevailing opinion, even small forest patches in oil palm landscapes may provide native pollinator pressure.

Assessing the importance of species and their assemblages for the biodiversity-ecosystem multifunctionality relationship.

Biodiversity changes, such as decline in species richness and biotic homogenization, can have grave consequences for ecosystem functionality. Careful investigation of biodiversity-ecosystem multifunctionality linkages with due consideration of conceptual and technical challenges is required to make the knowledge practically useful in managing social-ecological systems. In this paper, we introduced different methods to assess perspectives regarding the issue of diversity-multifunctionality, including a possible multifunctional redundancy/uniqueness, and the influences of the number and identity of functions on multifunctionality. In particular, we aimed to align methods with detecting the mechanisms underpinning diversity- multifunctional relationships that are free from statistical biases. Based on a set of novel methods that excluded analytical biases resulting from differences in the number and identities of multiple functions considered, we found that a substantial portion of species disproportionately supported ecosystem functions and that the diversity effects on multifunctionality were more markedly observed when more functions were considered. These results jointly emphasize that individual species are, to some extent, both functionally unique as well as redundant, highlighting the complexity and necessity for managed assemblages to retain high levels of diversity. We also observed that the relative magnitude of uniqueness or redundancy can differ between species and functions and therefore should be defined in a multifunctional context. We further found that only a small subset of species was identified as significantly less important, especially at low levels of multifunctionality. Taken together, given the low level of multifunctional redundancy we identified, we stress that unraveling the hierarchical roles of biodiversity at different levels, such as individual species and their assemblages, should be a high research priority, in both theory and practice. This article is protected by copyright. All rights reserved.

Cefquinome shows a higher impact on the pig gut microbiome and resistome compared to ceftiofur

Cephalosporins are licensed for treatment of severe bacterial infections in different species. However, the effect of these antimicrobials on the fecal microbiome and potential spread of resistance-associated genes causes great concern. This highlights the need to understand the impact of cephalosporins on the porcine fecal microbiome and resistome. A combination of long-read 16S rRNA gene and shotgun metagenomic sequencing was applied to investigate the effect of conventional treatment with either ceftiofur (3 mg.kg−1 intramuscular, 3 consecutive days) or cefquinome (2 mg.kg−1 intramuscular, 5 consecutive days) on the porcine microbiome and resistome. Fecal samples were collected from 17 pigs (6 ceftiofur treated, 6 cefquinome treated, 5 control pigs) at four different timepoints. Treatment with ceftiofur resulted in an increase in Proteobacteria members on microbiome level, while on resistome level selection in TetQ containing Bacteroides, CfxA6 containing Prevotella and blaTEM-1 containing Escherichia coli was observed. Cefquinome treatment resulted in a decline in overall species richness (α-diversity) and increase in Proteobacteria members. On genus level, administration of cefquinome significantly affected more genera than ceftiofur (18 vs 8). On resistome level, cefquinome resulted in a significant increase of six antimicrobial resistance genes, with no clear correlation with certain genera. For both antimicrobials, the resistome levels returned back to the control levels 21 days post-treatment. Overall, our study provides novel insights on the effect of specific cephalosporins on the porcine gut microbiome and resistome after conventional intramuscular treatment. These results might contribute to better tailoring of the most ideal treatment strategy for some bacterial infections.

Assessing the application of the revised Remane Model to fish species in a fluvially dominated cool-temperate southern African coastal system

Estuaries are ecologically important areas which support a variety of aquatic species, particularly marine and estuarine fish species. This study represents a case study of the Orange River and Estuary (ORE) to understand patterns in fish assemblages and diversity trends that were compared to the revised Remane Model predictions in an estuary with poor marine fish species richness. A total of 30 species were recorded in the River continuum that comprised 14 freshwater, 10 marine and six estuarine species. Species diversity revealed seasonal variation in fish assemblages during the high-flow and low-flow seasons but not inter-annually. The results revealed that species diversity is lower in higher salinity areas when compared to low salinity areas. These patterns are consistent with the biogeographical trend of decreasing species richness along the South African coast from east to west, however, inconsistent with Remane predictions. The extremely low marine fish richness at its lower end and the extremely large freshwater influx at its upper end are the primary causes of the inconsistency. This may reflects the unsuitability of the Remane model for the Orange Estuary. In comparison to similar river-dominated South African estuaries, the ORE has a low marine species richness. When compared to more conventional South African estuaries, the ORE has a unique biotic environment with low fish species richness of estuarine-associated marine species adjacent to the Benguela upwelling zone and therefore the region does not offer suitable habitat for such species. As a result, the ORE is not a good candidate to test the Remane Model. The data does, however, confirm the left-hand part of the Remane model, which shows a decline in the fish species richness of freshwater fish species as salinity rises towards mesohaline and polyhaline levels.

Climate change drives substantial decline of understorey species richness and abundance in Norway spruce forests during 32 years of vegetation monitoring

AbstractQuestionsObservations in permanent forest vegetation plots in Norway and elsewhere indicate that complex changes have taken place over the period 1988–2020. These observations are summarised in the “climate‐induced understorey change (CIUC)” hypothesis, i.e. that the understorey vegetation of old‐growth boreal forests in Norway undergoes significant long‐term changes and that these changes are consistent with the ongoing climate change as an important driver. Seven testable predictions were derived from the CIUC hypothesis.LocationNorway.MethodsVegetation has been monitored in a total of 458 permanently marked plots, each 1 m2, in nine old‐growth forest sites dominated by Picea abies at intervals of 5–8 years over the 32‐year study period. For each of the 52 combinations of site and year, we obtained response variables for the abundance of single species, abundance and species density of taxonomic–ecological species groups and two size classes of cryptogams, and site species richness. All of these variables were subjected to linear regression modelling with site and year as predictors.ResultsMean annual temperature, growing‐season length and the number of days with precipitation were higher in the study period than in the preceding ca. 30‐year period, resulting in increasingly favourable conditions for bryophyte growth. Site species richness decreased by 13% over the 32‐year study period. On average, group abundance of vascular plants decreased by 24% (decrease in forbs: 38%). Patterns of group abundance change differed among cryptogam groups: although peat‐moss abundance increased by 39%, the abundance of mosses, hepatics and lichens decreased by 13%, 49% and 67%, respectively. Group abundance of small cryptogams decreased by 61%, whereas a 13% increase was found for large cryptogams. Of 61 single species tested for abundance change, a significant decrease was found for 43 species, whereas a significant increase was found only for 6 species.ConclusionsThe major patterns of change in species richness, group species density and group abundance observed over the 32‐year study period accord with most predictions from the CIUC hypothesis and are interpreted as direct and indirect responses to climate change, partly mediated through changes in the population dynamics of microtine rodents. The more favourable climate for bryophyte growth explains the observed increase for a few large bryophyte species, whereas the decrease observed for small mosses and hepatics is interpreted as an indirect amensalistic effect, brought about by shading and burial in mats of larger species and accelerated by reduced fine‐scale disturbance by microtine rodents. Indirect effects of a thicker moss mat most likely drive the vascular plant decline although long‐term effects of tree‐stand dynamics and former logging cannot be completely ruled out. Our results suggest that the ongoing climate change has extensive, cascading effects on boreal forest ecosystems. The importance of long time‐series of permanent vegetation plots for detecting and understanding the effects of climate change on boreal forests is emphasised.

Context-dependent responses of terrestrial invertebrates to anthropogenic nitrogen enrichment: A meta-analysis.

Anthropogenic increases in nitrogen (N) concentrations in the environment are affecting plant diversity and ecosystems worldwide, but relatively little is known about N impacts on terrestrial invertebrate communities. Here, we performed an exploratory meta-analysis of 4365 observations from 126 publications reporting on the richness (number of taxa) or abundance (number of individuals per taxon) of terrestrial arthropods or nematodes in relation to N addition. We found that the response of invertebrates to N enrichment is highly dependent on both species' traits and local climate. The abundance of arthropods with incomplete metamorphosis, including agricultural pest species, increased in response to N enrichment. In contrast, arthropods exhibiting complete or no metamorphosis, including pollinators and detritivores, showed a declining abundance trend with increasing N enrichment, particularly in warmer climates. These contrasting and context-dependent responses may explain why we detected no overall response of arthropod richness. For nematodes, the abundance response to N enrichment was dependent on mean annual precipitation and varied between feeding guilds. We found a declining trend in abundance with N enrichment in dry areas and an increasing trend in wet areas, with slopes differing between feeding guilds. For example, at mean levels of precipitation, bacterivore abundance showed a positive trend in response to N addition while fungivore abundance declined. We further observed an overall decline in nematode richness with N addition. These N-induced changes in invertebrate communities could have negative consequences for various ecosystem functions and services, including those contributing to human food production.

Stagewise collapse of biotic communities and its relations to oxygen depletion along the north margin of Nanpanjiang Basin during the Permian–Triassic transition

The process of marine ecosystem collapse during the Permian–Triassic mass extinction may have varied in different paleogeographic settings and the intensity of oxygen depletion changed with different water depths. It remains largely unknown about the detailed biotic community collapse and its relation to paleo-redox condition in the deep-water basin. At the Kejiao section in the Nanpanjiang Basin of South China, the continuous sedimentation sequences and complete fossil records from the Changhsingian of Permian to the lowest Triassic provide a unique opportunity to study the progressive biotic crisis associated with oxygen deficiency in a deep-water setting. Here, we document high-resolution records of both the biodiversity dataset of different taxa and the redox data from the Kejiao section to achieve a new understanding of ecosystem deterioration associated with changes of redox conditions. The redox evolution revealed by changes in pyrite framboid size and morphology shows a change trend from lower dysoxic to oxygenated, and then to dysoxic interrupted by oxygenated and anoxic conditions in the late Changhsingian, and ending with euxinic conditions in the earliest Triassic. 60 species in 41 genera from radiolarians, bivalves, brachiopods and cephalopods were identified in the section and their occurrences show two pulses of extinction. The first pulse corresponds to the reduction in species richness of planktonic radiolarians and nektonic cephalopods, and the second pulse is documented by the wipe out of benthic brachiopods and remnant nektonic cephalopods and the decline in the species richness of benthic bivalves. This indicates the collapse of plankton and most nekton communities is ahead of the counterpart of benthos in the deepwater setting, supporting what observed in other sections in South China. The plankton and nekton communities inhabited water columns and the benthic community dwelled in the bottom water. Thus, the stagewise collapse of communities might be contributed by the expansion/migration, in particular, the downward expansion of Oxygen Minimum Zone (OMZ) documented by the information from pyrite framboids and the sedimentation.

Determining Tipping Points and Responses of Macroinvertebrate Traits to Abiotic Factors in Support of River Management.

Although the trait concept is increasingly used in research, quantitative relations that can support in determining ecological tipping points and serve as a basis for environmental standards are lacking. This study determines changes in trait abundance along a gradient of flow velocity, turbidity and elevation, and develops trait-response curves, which facilitate the identification of ecological tipping points. Aquatic macroinvertebrates and abiotic conditions were determined at 88 different locations in the streams of the Guayas basin. After trait information collection, a set of trait diversity metrics were calculated. Negative binomial regression and linear regression were applied to relate the abundance of each trait and trait diversity metrics, respectively, to flow velocity, turbidity and elevation. Tipping points for each environmental variable in relation to traits were identified using the segmented regression method. The abundance of most traits increased with increasing velocity, while they decreased with increasing turbidity. The negative binomial regression models revealed that from a flow velocity higher than 0.5 m/s, a substantial increase in abundance occurs for several traits, and this is even more substantially noticed at values higher than 1 m/s. Furthermore, significant tipping points were also identified for elevation, wherein an abrupt decline in trait richness was observed below 22 m a.s.l., implying the need to focus water management in these altitudinal regions. Turbidity is potentially caused by erosion; thus, measures that can reduce or limit erosion within the basin should be implemented. Our findings suggest that measures mitigating the issues related to turbidity and flow velocity may lead to better aquatic ecosystem functioning. This quantitative information related to flow velocity might serve as a good basis to determine ecological flow requirements and illustrates the major impacts that hydropower dams can have in fast-running river systems. These quantitative relations between invertebrate traits and environmental conditions, as well as related tipping points, provide a basis to determine critical targets for aquatic ecosystem management, achieve improved ecosystem functioning and warrant trait diversity.