Trends In Abundance Research Articles

Monitoring within-patch, flying season population dynamics of an endangered mire-dwelling dragonfly, Petalura gigantea (Odonata: Petaluridae)

ABSTRACT Understanding within-patch seasonal demographics of patchily distributed odonates is fundamental to understanding aspects of their behaviour, ecology, and landscape-scale population dynamics. Such knowledge underpins effective conservation management and is dependent upon appropriate survey methods. The objective of this study was to understand the within-patch, flying season, population dynamics of imagos of the endangered mire-dwelling dragonfly, Petalura gigantea, using a modified Pollard Walk, a line transect survey technique. Relative abundance of imagos was monitored at nominally weekly intervals, by sex, across the duration of the flying season in six mire patches in the Blue Mountains, New South Wales. There was a preponderance of adult males and a relatively consistent trend in changing relative abundance of adult males compared to females within mire habitat across all surveys, with a marked seasonal peak in male abundance, confirming that surviving adult females generally occupy non-mire habitat other than for reproduction. This study confirmed the utility of this technique to monitor changing relative abundance of adult males within mire patches across a flying season, and potentially, for comparison among years for a separate, longitudinal, landscape-scale study. Successful use of the technique is contingent upon a sound understanding of the species’ habitat preferences and behaviour, with caveats for survey timing and weather protocols, to satisfy minimum requirements for detectability, repeatability, and replicability. The technique could be used, with species- and habitat-specific modifications, for monitoring other patchily distributed odonates, including petalurids, and contribute to their improved conservation management.

When good turns to bad and alien predators appear: The dynamics of biodiversity change in boreal waterbird communities

Temporal patterns of biodiversity are often difficult to interpret because of our limited understanding of how communities vary through time and how processes drive this variation. A further challenge with dynamic systems is choosing an appropriate baseline against which biodiversity change is judged. We used abundance time series of breeding waterbirds in eutrophic lakes in Finland for 1946–2022 to study the dynamics of biodiversity change in local communities and the relative role of two presumed main drivers, i.e. eutrophication and alien predators, in contributing to historical and recent trends in local abundances and biodiversity. We set the cut-off for the historical and recent study periods in the mid-1980 s, because the systematic monitoring of breeding waterbirds in Finland started in 1986 and recent analyses of biodiversity change and population trends in European boreal waterbird communities are mainly based on time series and data gathered since 1986. Both species richness and the total abundance of waterbirds in local communities showed contrasting trends between historical (gathered before the mid-1980 s) and current (gathered after the mid-1980 s) community time series, with the current time series indicating a decline and the historical time series indicating an increase. The abundances of habitat specialists (species preferring eutrophic lakes) and habitat generalists (species using both eutrophic and oligotrophic lakes) showed a corresponding difference between the current and historical time series. The local extinction rates were higher among habitat specialists than among habitat generalists. The trend indices for wetland-nesting species (highly vulnerable to predation by two alien species (the raccoon dog, Nyctereutes procyonoides, and American mink, Neovison vison) in terms of nest site) abundances were more negative than the trend indices of species nesting further away from waterbodies (less vulnerable to predation by two alien species). In addition, bottom-feeding species (presumably more sensitive to negative impacts of eutrophication) did not show more negative population trends than surface-feeding species (presumably less sensitive to negative impacts of eutrophication). Regardless of equal sensitivity to negative impacts of eutrophication, two species highly vulnerable to two alien predators showed more negative population trends than a less vulnerable species. The results suggest that increased predation has been an important driver of the population and biodiversity declines in the studied waterbird communities. The mid-1980 s may not provide an ecologically appropriate baseline against which changes in the populations and biodiversity of boreal waterbird communities are judged.

Impacts of a century of land‐use change on the eutrophication of large, shallow, prairie Lake Manitoba in relation to adjacent Lake Winnipeg (Manitoba, Canada)

Abstract Evaluation of large lake response to centennial changes in land use and climate can be complicated by high spatial and hydrological complexity within their catchments, particularly in regions of low relief. Furthermore, large lakes can exhibit abrupt changes in structure and function that obscure causes of eutrophication. We provide the first quantification of historical trends in lake production, cyanobacterial abundance, sediment geochemistry and diatom composition since c. 1800 in Lake Manitoba, the 29th largest lake in the world, and compared them to Lake Winnipeg, a morphologically similar, adjacent basin with a 10‐fold larger catchment and an abrupt increase in production around 1990. Before 1900, Lake Manitoba was mesotrophic, with low sedimentary concentrations of carbon, phosphorus, nitrogen, cyanobacteria and algal pigments, as well as assemblages of low‐light‐adapted benthic diatoms. Analysis of pigment time‐series with hierarchical generalised additive models revealed that Lake Manitoba eutrophied during 1900–1930 as a consequence of the development of intensive agriculture within its local catchment, but thereafter exhibited stable cyanobacterial densities with limited expansion of N2‐fixing cyanobacteria despite persistent eutrophication. Lake Manitoba did not undergo an abrupt change as seen in Lake Winnipeg. These findings suggest that catchment size had little influence on water quality degradation and that nutrient influx from proximal agricultural sources was sufficient to initially degrade these large prairie lakes. The abrupt change in Lake Winnipeg around 1990 required additional intensification of local land use that did not occur in the Lake Manitoba catchment.

Monitoring wildlife population trends with sample counts: a case study on the Alpine ibex (Capra ibex)

Monitoring population dynamics is of fundamental importance in conservation but assessing trends in abundance can be costly, especially in large and rough areas. Obtaining trend estimations from counts performed in only a portion of the total area (sample counts) can be a cost‐effective method to improve the monitoring and conservation of species difficult to count.We tested the effectiveness of sample counts in monitoring population trends of wild animals, using as a model population the Alpine ibex Capra ibex in the Gran Paradiso National Park (Italy), both with computer simulations and using historical count data collected over the last 65 years. Despite sample counts failed to correctly estimate the true population abundance, sampling half of the target area could reliably monitor the trend of the target population. In case of strong changes in abundance, an even lower proportion of the total area could be sufficient to identify the direction of the population trend. However, when there is a high yearly trend variability, the required number of samples increases and even counting in the entire area can be ineffective to detect population trends. The effect of other parameters, such as which portion of the area is sampled and detectability, was lower, but these should be tested case by case.Sample counts could therefore constitute a viable alternative to assess population trends, allowing for important, cost‐effective improvements in the monitoring of wild animals of conservation interest.

Seasonal Dynamics of Microphytobenthos Distribution in Three Ecotopes on a Mussel Farm (Black Sea)

As the production of cultured bivalve mollusks is increasing worldwide, there is a growing need to study the biodiversity and ecology of microalgae in the mariculture zones. This study presents multiannual data (obtained in 2015–2016 and 2018–2020) on the species composition, abundance, biomass, and community structure of microphytobenthos from three mussel farm ecotopes (mussel shells, the epiphyton of twenty macroalgal species, and sediments under collectors). In total, 150 microalgal taxa were found, including 135 diatom species with a predominance of benthic (76%), marine (65%), and cosmopolite (30%) ones. In all habitats, 10 potentially harmful species and 44 indicators of organic pollution were noted. The maximum values on the mussel shells (abundance N = 119 × 103 cells/cm2 and biomass B = 0.0489 mg/cm2) were recorded in winter with the dominance of Tabularia fasciculata; in summer, the epiphyton was on the brown alga Nereia filiformis (N = 1001 × 103 cells/cm2 and B = 2.06 mg/cm2) with the dominance of toxic Pseudo-nitzschia seriata, on the red alga Phyllophora crispa (N = 1118 × 103 cells/cm2 and B = 3.24 mg/cm2) with the dominance of T. fasciculata, and in sediments (N = 104 × 103 cells/cm3 and B = 0.046 mg/cm3) with the dominance of T. fasciculata and Bacillaria paxillifer. Statistically significant effects of the ecotope and sampling season on the diatom composition were noted. The strongest effect of temperature is observed for the mussel shell diatoms, for which the trend of abundance and biomass increase in winter and their decrease in summer is most noticeable. But in sediments, the effect of the season is reflected only in the permanent changes of the microalgae species composition. For the epiphyton, it was shown that it is temperature, rather than substrate macrophyte species, that affects its numerical structure.

Climatology, Long‐Term Trend and Solar Response of Na Density Based on 28 Years (1990–2017) of Midlatitude Mesopause Na Lidar Observation

AbstractThe climatology of earth's Na density over Fort Collins, CO (41°N, 105°W) based on nocturnal Na lidar observations between 1990 and 1999 was reported by She et al. (2000, https://doi.org/10.1029/2000gl003825). Based on a continued 28‐year data set between 1990 and 2017 with the latter part observed over Logan, UT (42N, 112W), we update the seasonal variations between 80 and 110 km. This data set is also used to deduce long‐term responses of Na density (profile) between 75 and 110 km, showing a positive linear trend between 75 and 93 km (with maximum ∼2.87 × 108 m−3/decade at 87 km); it turns negative before approaching zero at 110 km (with minimum ∼−2.96 × 107 m−3/decade at 100 km). The associated solar response is also positive for the altitude range in question (with maximum ∼5.20 × 106 m−3/SFU at 91 km). We also derived the 28‐year mean Na layer column abundance, centroid altitude, and root mean square width to be 3.92 ± 2.14 1013 m−2, 91.3 ± 1.0 km, and 4.62 ± 0.56 km, respectively, and deduced long‐term trend and solar cycle responses of column abundance and centroid altitude, respectively to be 7.81 ± 1.63%/decade and 16.9 ± 2.8%/100SFU, and −355 ± 35 m/decade and −1.94 ± 0.69 m/SFU. We explained conceptually how positive long‐term responses in Na density led to positive responses in column abundance and negative responses in centroid altitude.

Insight in molecular degradation patterns and co-metabolism during rose waste co-composting

Composting is recognized as a sustainable waste management strategy. However, little is known about green waste, and specifically rose waste, degradation patterns during composting. This study aimed (1) to gain insight in the underlying decomposition patterns during rose waste composting and (2) to identify co-metabolisms of ligneous material. Five different compost mixtures were tested ranging from pure rose waste to mixtures with tomato waste, kalanchoe waste or mature compost added. Samples were taken during a six-month experiment and analyzed by pyrolysis-GC/MS. The temporal trends in the relative abundance of 10 different compound groups were measured. Lignin and aliphatic compounds together accounted for ≥ 50% of the quantified pyrolysis products, but with changing contributions during composting. The relative abundance of polysaccharides and terpenes strongly decreased with more than 60% in the first 2 months. The simultaneous decrease in relative abundance of lignin and polysaccharides during initial composting phase indicated co-metabolism of lignin. The results from this study showed that while the presence of lignin is commonly regarded as a challenge in composting, it actually undergoes degradation through distinct mechanisms at the various composting stages.

Temporal changes in the individual size distribution modulate the long‐term trends of biomass and energy use of North American breeding bird communities

AbstractAimThe frequency of different body sizes in an ecological community (the individual size distribution, or ISD) is a key link between the number of individual organisms present in a community and community function—total biomass or total energy use. If the ISD changes over time, the dynamics of community function may become decoupled from trends in abundance. Understanding how, and how often, the ISD modulates the relationship between abundance, biomass and energy use is of critical importance to understand biodiversity trends in the Anthropocene. Here, we conduct the first macroecological‐scale analysis of this type for avian communities.LocationNorth America, north of Mexico.Time Period1989–2018.Major Taxa StudiedBreeding birds.MethodsWe used species' traits to generate annual ISDs for bird communities in the North American Breeding Bird Survey. We compared the long‐term trends in total biomass and energy use to the trends generated from a null model of an unchanging ISD.ResultsTrends in biomass have been evenly split between increases and decreases, but the trends predicted by the null model were dominated by decreases. A substantial number of communities have undergone a shift in the ISD favouring larger bodied species, resulting in a less negative trend in biomass than would be expected had the ISD remained static. Trends in energy use more closely paralleled the null model.Main ConclusionsTaking changes in the ISD into account qualitatively changes the continental‐scale picture of how biomass and energy use have changed over the past 30 years. For North American breeding birds, shifts in species composition favouring larger bodied species may have partially offset declines in standing biomass driven by losses of individuals over the past 30 years.

Long‐term patterns of fish community structure and decline in native species in a Colorado River reservoir, Arizona and Nevada

AbstractObjectiveThe Colorado River has undergone substantial anthropogenic modifications, and a suite of nonnative species have been introduced since the 1800s; consequently, native fish communities are severely imperiled. We examined temporal patterns in fish community structure in Lake Mohave (i.e., lower Colorado River basin) over 40 years from 1980 to 2020.MethodsWe examined long‐term abundance and richness trends and the trajectory of fish community structure in multivariate space to assess stability and turnover using results from biannual (spring and autumn) trammel‐net monitoring over 40 years from 1980 to 2020.ResultNonnative fishes were established prior to sampling, precluding the ability to determine historical fish community structure. Bonytail Gila elegans and Razorback Sucker Xyrauchen texanus were the only two remaining native fishes, and both declined precipitously in abundance through time. However, a repatriation program initiated in 1991 prevented Razorback Sucker from extirpation, while reintroduction efforts for Bonytail have failed. Both wild populations are gone. Total catch per unit effort showed a negative relationship from 1980 to 2020, whereas total species richness showed no relationship. Long‐term abundance trends at the species level indicated three nonnative species (i.e., Gizzard Shad Dorosoma cepedianum, Yellow Bullhead Ameiurus natalis, and Smallmouth Bass Micropterus dolomieu) increased, nine decreased, and three showed no relationship. Fish community composition exhibited low stability and moderate turnover and shifted directionally through time in multivariate space, with the formation of three clusters, possibly indicating alternative states.ConclusionThe contemporary fish community shows little resemblance to the endemic ichthyofauna that has historically occupied the Colorado River, and the Razorback Sucker is the only remaining native species due to recovery efforts. Continued adaptive management will be required to preserve the most genetically diverse Razorback Sucker population in the Colorado River system, especially while coexisting with an unstable nonnative fish community.

Molecule-based quantification of dissolved organic matter sources in high-arsenic groundwater

Compositions of dissolved organic matter (DOM) in high-arsenic groundwater are usually sourced from the recharged groundwater DOM and the in-situ mobilized organic matter (OM) from aquifer sediments. However, relative importance of the two sources in DOM remains unclear. To quantify sources of DOM, Fourier transform ion cyclotron resonance mass spectrometry was used to analyze molecular characteristics of groundwater DOM and water-soluble organic matter (WSOM) in sediments along an inferred groundwater flow path in the Hetao Basin, China. Results showed that dissolved arsenic concentrations gradually increased from 1.92 to 402 μg/L along the flow path, being mainly due to the DOM degradation-triggered Fe(III) oxide reduction. The DOM molecules being unique to the background groundwater represented the in-situ mobilized OM, which showed the similar abundance to the DOM molecules being common to its depth-matched WSOM. An increasing trend of the relative abundance of the in-situ mobilized OM to the total DOM molecules along the flow path was recognized (from 0 % to 44.5 %). This suggests that the relative contribution of the in-situ mobilized OM to the groundwater DOM increased along with dissolved arsenic concentration. Furthermore, the biodegradable pool among the in-situ mobilized OM was significantly positively correlated with dissolved arsenic, indicating that this in-situ mobilized OM exhibited a dominant role in groundwater arsenic enrichment. The study provides novel insights into contribution of the in-situ mobilized OM to DOM and arsenic mobility in groundwater systems.

Changes in the Endophytic Bacterial Community of Brassica rapa after Application of Systemic Insecticides.

Insecticides not only control target pests but also adversely affect non-target communities including humans, animals, and microbial communities in host plants and soils. The effect of insecticides on non-target communities, especially endophytic bacterial communities, remains poorly understood. Two phases of treatments were conducted to compare the trends in endophytic bacterial response after insecticide application. Endophytic bacteria were isolated at 2 and 4 weeks after germination. Most insecticide treatments showed a declining trend in bacterial diversity and abundance, whereas an increasing trend was observed in the control. Therefore, insecticide use negatively affected non-target endophytic bacterial communities. Bacillus spp. was mostly dominant in the early stage in both insecticide treatment and control groups. Nevertheless, in the matured stage, mostly bacteria including Pseudomonas spp., Priestia spp. were dominant in groups treated with high insecticide concentrations. Therefore, plants can regulate and moderate their microbiome during their lifecycle depending on surrounding environmental conditions.

Seasonal dynamics of floral composition and flower visitors in a subtropical alpine ecosystem in Taiwan

AbstractFlowering phenology of alpine plant communities and seasonal dynamics of flower visitors have been scarcely studied in the tropical/subtropical alpine regions. We report flowering phenology, flower production, and flower‐visiting insects in an alpine site of central Taiwan. Throughout the research period (2017–2018), we recorded flowering phenology of 130 plant species, flower production of 81 species, and 15,127 insects visiting alpine flowers. Most of the alpine plants were visited by dipteran insects and/or hymenopteran insects. The seasonal patterns of flowering were more apparent in bee‐visited plants compared to fly‐visited plants in which the flowering of bee‐visited plants clearly increased as the season progressed. About 63% of flower visitors were dipteran insects (syrphid and non‐syrphid flies), and 30% were hymenopteran insects (mostly bumble‐bee workers). Although the seasonal trend in fly abundance was less clear between years, bumble‐bee abundance consistently increased in the middle to late seasons, reflecting colony development. There was a positive correlation between bee abundance and the number of flowering species of bee‐visited plants, but there was no correlation between fly abundance and the number of flowering species of fly‐visited plants throughout the season. These results suggest that the flowering phenology of subtropical alpine communities is influenced by the seasonal availability of pollinators. Bumble bees, syrphid flies, and non‐syrphid flies had wide ranges of foraging flowers, but their niche overlap was relatively small. Because cold‐adapted bumble bees are threatened by climate change in Taiwan, plant–pollinator interactions may be disturbed by global warming.

Decline and Extinction of the Italian Agile Frog Rana latastei from Core Areas of Its Range.

Detecting the trends of species and populations is fundamental to identifying taxa with high conservation priority. Unfortunately, long-term monitoring programs are challenging and often lacking. The Italian agile frog Rana latastei is endemic to Northern Italy and adjacent countries, is considered vulnerable by the IUCN, and is protected at the European level. However, quantitative estimates of its decline are extremely scarce. In this study, we document the trends in abundance and distribution of Rana latastei within Monza Park, which currently represents the area closer to the type locality of the species and holds unique genetic features. Wetlands within the park were monitored from 2000 to 2023; counts of egg clutches were taken as a measure of reproductive output and the abundance of breeding females. In 2000, the species occurred over a significant proportion of the park. Total abundance showed strong yearly variation but remained rather constant from 2000 to 2019. However, Rana latastei disappeared from the park around 2021 and was never detected in 2022-2023. The decline is probably related to the joint effect of multiple factors, including the conversion of breeding sites for farming, inappropriate water management, invasive alien species, and severe drought. The local extinction of Rana latastei occurred despite legal protection, highlighting the need for more effective and stringent tools for the conservation of European biodiversity.

Simulation-based assessment of the performance of hierarchical abundance estimators for camera trap surveys of unmarked species

Knowledge on animal abundances is essential in ecology, but is complicated by low detectability of many species. This has led to a widespread use of hierarchical models (HMs) for species abundance, which are also commonly applied in the context of nature areas studied by camera traps (CTs). However, the best choice among these models is unclear, particularly based on how they perform in the face of complicating features of realistic populations, including: movements relative to sites, multiple detections of unmarked individuals within a single survey, and low detectability. We conducted a simulation-based comparison of three HMs (Royle-Nichols, binomial N-mixture and Poisson N-mixture model) by generating groups of unmarked individuals moving according to a bivariate Ornstein–Uhlenbeck process, monitored by CTs. Under a range of simulated scenarios, none of the HMs consistently yielded accurate abundances. Yet, the Poisson N-mixture model performed well when animals did move across sites, despite accidental double counting of individuals. Absolute abundances were better captured by Royle-Nichols and Poisson N-mixture models, while a binomial N-mixture model better estimated the actual number of individuals that used a site. The best performance of all HMs was observed when estimating relative trends in abundance, which were captured with similar accuracy across these models.

Distribution of microplastic contamination in the major tributaries of the Yellow River on the Loess Plateau

Microplastic pollution in rivers had gained increased attention worldwide. However, the differences in microplastic characteristics among major tributaries of large rivers and the environmental factors influencing these characteristics remain uncertain. Through field investigation and indoor experiments, the distribution of microplastics and their driving factors were investigated at 96 sampling sites along the three main tributaries (Huangfuchuan, Wuding and Yan River) of the Yellow River in the Loess Plateau. The results revealed that the average microplastic abundance followed this order: Yan River (430.30 items kg−1) > Wuding River (145.09 items kg−1) > Huangfuchuan River (253.33 items kg−1). The abundance was lower than that in most parts of the world. There was a generally increasing trend in average microplastic abundance from upstream to downstream in the three rivers. The most frequently observed microplastic colors observed were black and white, and the most common polymer type were PE and PS in all three rivers. The dominant shape and size in the three rivers were fiber and particles measuring 0.5–5.0 mm, all accounting for more than half of the total microplastic content. The microplastic abundance, shape, and size were primarily influenced by mean annual precipitation and population density. This relationship can be attributed to the fact that increased population density driven by higher demand and consumption of plastic products, while augmented rainfall aggravated the occurrence of floods and provided conditions for plastic degradation and accumulation. This study will provide fundamental data for pollution assessing and ecological protection of the Yellow River, and provide a certain reference for future management and protection on the Loess Plateau.

Long-Term Trends in Seasonality and Abundance of Three Key Zooplankters in the Upper San Francisco Estuary

Zooplankton provide critical food for threatened and endangered fish species in the San Francisco Estuary (estuary). Reduced food supply has been implicated in the Pelagic Organism Decline of the early 2000s, and further changes in zooplankton abundance, seasonality, and distribution may continue to threaten declining fishes. While we have a wealth of monitoring data, we know little about the abundance trends of many estuary zooplankton species. To fill these gaps, we reviewed past research and then examined trends in seasonality and abundance from 1972 to the present of three key but understudied zooplankton species (Bosmina longirostris, Acanthocyclops spp., and Acartiella sinensis) that play important roles in the estuary food web. We fit Bayesian generalized additive mixed models of each taxon’s relationship with salinity, seasonality, year, and geography on an integrated database of zooplankton monitoring in the upper estuary. We found marked changes in the seasonality and overall abundance of each study species. Bosmina longirostris no longer peaks in abundance in the fall months, Acanthocyclops spp. precipitously declined in all months and lost its strong relationship with salinity, and A. sinensis adult abundance has become more strongly related to salinity while juveniles have developed wider seasonal abundance peaks. Through these analyses, we have documented the relationship of each species with salinity and seasonality since the beginning of monitoring or their introduction, thus increasing our understanding of their ecology and importance in the estuary. These results can inform food-web models, be paired with fish data to model the contributions of these species toward fish abundance trends and be mirrored to elucidate other species’ trends in future studies.

Zooarchaeological evidence for livestock management in (earlier) Neolithic Europe: Outstanding questions and some limitations of current approaches

With the increasingly routine recovery of faunal remains from archaeological excavations and zooarchaeological analysis of such assemblages by macroscopic and, more recently, biomolecular methods, we now have an unprecedented wealth of evidence for early European livestock management at local, regional and continental scales. We can identify broad geographical and temporal trends in the relative abundance, size and mortality patterns of different livestock species, and have more piecemeal evidence for their diet, mobility and seasonality of reproduction and for human exploitation of their secondary as well as primary products. Conversely, we have little if any direct zooarchaeological evidence for the scale of livestock management and this, coupled with disagreement regarding the intensity of secondary products usage, hinders consensus on the contribution of livestock to human subsistence in Neolithic Europe. It is proposed here that most domestic ruminants in Neolithic Europe were managed for non-specialised exploitation of a mixture of carcass and secondary products and, drawing on a range of indirect proxies, that livestock were mostly kept in small numbers. It follows that the direct dietary contribution of domestic animals to Neolithic human subsistence will normally have been subordinate to that of grain crops and secondary to their role in supporting cultivation and social dynamics. If these propositions are accepted, some recent attempts to interpret regional (and diachronic) variation in zooarchaeological evidence in terms of latitudinal contrasts in climate and vegetation may be ill-founded. In conclusion, it is argued that sound interpretation of the wealth of zooarchaeological data now available, as evidence for early European animal keeping, requires their integration with other lines of archaeological, bioarchaeological and palaeoecological investigation in the context of broader models of Neolithic subsistence, land use and political economy. The approach advocated, while illustrated with examples from Neolithic Europe, is of wider geographical relevance and, despite its critical tone, this assessment of the state of the field is essentially optimistic.

Chemical abundances of the young inner-disc open cluster NGC 6705 observed by APOGEE: sodium-rich and not α-enhanced

ABSTRACT Previous results in the literature have found the young inner-disc open cluster NGC 6705 to be mildly α-enhanced. We examined this possibility via an independent chemical abundance analysis for 11 red-giant members of NGC 6705. The analysis is based on near-infrared APOGEE spectra and relies on LTE calculations using spherical model atmospheres and radiative transfer. We find a mean cluster metallicity of $\rm [Fe/H] = +0.13 \pm 0.04$, indicating that NGC 6705 is metal-rich, as may be expected for a young inner-disc cluster. The mean α-element abundance relative to iron is $\rm \langle [\alpha /Fe]\rangle =-0.03 \pm 0.05$, which is not at odds with expectations from general Galactic abundance trends. NGC 6705 also provides important probes for studying stellar mixing, given its turn-off mass of M ∼ 3.3 M⊙. Its red giants have low 12C abundances ([12C/Fe] = −0.16) and enhanced 14N abundances ([14N/Fe] = +0.51), which are key signatures of the first dredge-up on the red giant branch. An additional signature of dredge-up was found in the Na abundances, which are enhanced by [Na/Fe] = +0.29, with a very small non-LTE correction. The 16O and Al abundances are found to be near-solar. All of the derived mixing-sensitive abundances are in agreement with stellar models of approximately 3.3 M⊙ evolving along the red giant branch and onto the red clump. As found in young open clusters with similar metallicities, NGC 6705 exhibits a mild excess in the s-process element cerium with $\rm [Ce/Fe] = +0.13\pm 0.07$.

Population dynamics in Taiwan from the Neolithic to early historic periods (5000–100 cal BP): Linking cultural developments and environmental change

To reconstruct population dynamics in Taiwan between 5000 and 100 cal BP, we analysed spatial-temporal changes in archaeological site abundance and size (area). The results suggest that population growth was discontinuous throughout the study region and that the main spatial differences in population trends were between eastern/northern and western Taiwan. Comparison of settlement data shows that population trends in Taiwan and different regions in continental China were partly parallel. We contrast these data with political, economic, settlement, and climatic developments in continental China, when considering possible factors that influenced these demographic relationships. In addition, we examined published palaeoenvironmental time series from the broader study region to explore human-environment interactions. This revealed that proxy records of human activities (agriculture, deforestation) correlate with the derived trends in site abundance and area. Furthermore, we hypothesise that the inferred sparse settlement in eastern Taiwan during 2700–1800 cal BP is related to climate change. An increase in seasonal rainfall and high-intensity precipitation events in late summer and autumn, due to long-term changes in summer monsoon precipitation and El Niño–Southern Oscillation intensity, likely resulted in unfavourable hydrological conditions for crop cultivation in this part of the study region.

Positive population trends among meso‐ and megaherbivores follow intensive conservation efforts in Volcanoes National Park, Rwanda

It is unclear whether the remarkable recovery of mountain gorillas Gorilla beringei beringei in the Virunga Mountains, East Africa, that followed decades of intensive conservation efforts, is indicative of positive trends in abundance and distribution of other large mammals (meso‐ and megaherbivores). Positive population trends are particularly relevant for globally threatened elephants Loxodonta sp., as conservation and research efforts have predominantly focused on populations that range in lowland savanna ecosystems rather than the smaller but ecologically and genetically unique populations found in the Virunga montane ecosystems. We used marked pellet group counts in dung clearance plots to determine the density/abundance and distribution of three mesoherbivores (buffalo, black‐fronted duiker, bushbuck) and one megaherbivore (elephant) in Volcanoes National Park (VNP; covering part of the Virunga Mountains), Rwanda, in July–September 2008 and 2021. We estimated that elephants and duiker populations saw a minor increase between 2008 and 2021 while densities of buffalo and bushbuck increased substantially over the course of the past decade. We also found no evidence of substantial distributional shifts for elephants but observed increases in densities of the other species in the southwestern parts of the VNP. Overall, density estimates for all species were much higher in both 2008 and 2021 than in a previous survey in 2004, which suggests that meso‐ and megaherbivores have largely recovered from a steep decline in numbers towards the end of the 20th century, possibly benefitting from the same protection efforts that benefitted mountain gorillas.