Species-specific Density Research Articles

Understanding filamentous cyanobacteria and their adaptive niches in Lake Honghu, a shallow eutrophic lake

Freshwater lakes globally are witnessing an escalation in the frequency and intensity of cyanobacterial harmful blooms. However, underlying factors influencing the succession or coexistence of cyanobacteria, especially filamentous ones, remain poorly understood. Lake Honghu, a Ramsar Wetland of International Importance with degrading aquatic ecological quality, served as a case study to elucidate the intricate relationship between environmental changes and cyanobacterial dynamics. Our analysis revealed a significant increase in the dominance of filamentous cyanobacteria, marked by high spatiotemporal variability in community structure. This dominance of filamentous diazotrophic cyanobacteria is attributed to a decrease in the ratio of dissolved inorganic nitrogen to total phosphorus and their capacity to utilize organic phosphorus in phosphorus-deficient conditions. Species-specific density variations were linked to diverse environmental factors, with total nitrogen or total phosphorus concentration remaining as a crucial factor influencing dominant cyanobacterial density fluctuations. The dominance of low-temperature-tolerant Aphanizomenon and Pseudanabaena was evident in spring and winter, whereas Dolichospermum and Cylindrospermopsis, which prefer higher temperatures, thrived in summer and autumn. Additionally, non-algal turbidity and heterogeneity can potentially alter the competitive outcome among filamentous cyanobacteria or foster coexistence under conditions of elevated temperatures and nutrient limitation. This study predicts that filamentous cyanobacteria may spread and persist in lakes spanning a wide trophic range. Current findings enhance our comprehension of the dynamic responses exhibited by filamentous bloom-forming cyanobacteria in the face of environmental changes within shallow eutrophic lakes and provide valuable insights for lake managers involved in the remediation of degraded shallow lakes.

What the Hakes? Correlating Environmental Factors with Hake Abundance in the Gulf of Maine

According to the latest estimates, the Gulf of Maine is currently warming faster than 99% of the world’s oceans. As a result, this region has become an ideal location for research into the effects that warming has on the historical fisheries that make up this ocean basin. Both white hake (Urophycis tenuis) and red hake (Urophycis chuss) are common Gulf of Maine groundfish species, distributed both inshore and offshore. While these two species are closely related phycid hakes, white hake stocks are recognized in the Gulf of Maine as rebuilding, while red hake are above target biomass levels. As a species commonly found throughout the Gulf of Maine that prefers cooler waters (4–12°C), we hypothesize the effects of climate change might influence stock behavior, such as changes in species distribution. We used generalized additive models (GAMs) to describe the relationship between hake abundance and environmental conditions using bottom temperature, bottom salinity, depth, and catch data contributed by the Maine Department of Marine Resources during their Maine – New Hampshire Inshore Trawl Surveys of the last 22 years (2000 – 2021). Our results reveal species-specific preferences for bottom temperature (white hake ~9 to ~13℃, red hake < 12℃) and depth (white hake ~55 to ~100m, red hake > ~65m), with no significant correlation to bottom salinity. Spatially over time, white hake abundance displayed a gradual center of gravity northward, while red hake rapidly increased inshore. Overall, these results highlight species-specific density changes in inshore distribution, consistent with previous studies, with considerable implications on future management strategies in this region.

A seven-year study of large mammal populations in the Sahel, West Africa

The dry savannahs of the Sahelian vegetation zone house a remarkable community of large mammals that have been less studied than their counterparts in the eastern Africa. Here we examine some aspects of the ecology of a community of twenty different large mammal species in a savannah of Burkina Faso, for a relatively long-term period (seven years). We observed remarkable interannual differences in terms of (i) number of contacts and (ii) their groups size (range of groups). Nonetheless, the calculated Kilometric Index of Abundance, with all species pooled, showed a relatively stable value of 0.88–1 individual per Km, apart in 2012 when it decreased to 0.7. GLM models on the observed number of contacts and group sizes revealed that there were significant effects of the species, but neither of the year nor of the season. Remarkable species-specific density fluctuations throughout time were observed when applying the DISTANCE methodology to the dataset. The sex ratio showed great fluctuations between the years and by species, even if there was a general predominance of females.

Blooming Forbs Utilized by Breeding-Season Danaus plexippus in the USA North-Central Region

Danaus plexippus (monarch butterfly) populations in North America east of the Rocky Mountains are in decline due to loss of habitat containing Asclepias spp. (milkweed) and blooming forbs. To support D. plexippus recovery, habitat restoration efforts use seed mixes designed to maintain a diversity of species that bloom over the breeding and migration periods. The extent to which these species are uniquely attractive to foraging D. plexippus is unclear. We conducted observational studies at areas in Iowa USA with varying densities and diversities of Asclepias spp. and floral resources to help inform conservation management practices. Forty-two blooming forb species were present across four sites (2-4-ha) in Boone and Story counties from June through September in 2020. Many of the species present are commonly found in pollinator seed mixes. The number of blooming forbs species per site varied from 12 to 24 across the four months; the minimum and maximum density of species-specific inflorescences ranged from 8.45 to 36.3 inflorescence/m2. We observed D. plexippus nectaring on 27 of the 42 species across the sites. Based on total feeding events observed and the species-specific density of inflorescences, Asclepias syriaca, Asclepias verticillata, Helianthus grosseserratus, and Cirsium vulgare were favored for nectaring at each site where they were present. Additional species were favored in some, but not all, sites including Symphyotrichum pilosum, Eupatorium altissimum, Trifolium pratense, Echinacea pallida, and Verbena urticifolia. Findings suggest variation in preference may be due, in part, to site-specific and surrounding landscape features. Future studies on D. plexippus foraging behavior could address the interacting roles of habitat and landscape features, as well as species-specific flower size and shape, scent, nutrition, and nectar abundance. While forb utilization is likely influenced by site- and plant-specific features, preferred species we observed are typically included in recommended native seed mix designed to ensure blooms from June through September to support migratory and non-migratory, breeding D. plexippus.

Population dynamics of the Manyara monkey (Cercopithecus mitis manyaraensis) and vervet monkey (Chlorocebus pygerythrus) in Lake Manyara National Park, Tanzania.

Estimating population densities and their trends over time is essential for understanding primate ecology and for guiding conservation efforts. From 2011 through to 2019, we counted two guenon species during seasonal road transect surveys in Lake Manyara National Park: the Tanzania-endemic Manyara monkey Cercopithecus mitis manyaraensis (International Union for Conservation of Nature and Natural Resources, IUCN, Red List category of "endangered") and the vervet monkey Chlorocebus pygerythrus (Red List category of "least concern"). To account for imperfect detectability, we analysed the data in a line distance sampling framework, fitted species-specific detection functions, and subsequently estimated seasonal densities. To test for seasonal differences and yearly trends in the species-specific density estimates, we fitted generalized additive models. Seasonal point density estimates fluctuated considerably during the 9years (2011-2019) of our study, ranging from 3 to 29 individuals km for Manyara monkeys and from 19 to 83 individuals km for vervet monkeys. Densities of both taxa did not differ seasonally, and we did not detect marked directional population trends. Our study illustrates the utility and limitations of line distance sampling for long-term primate monitoring. Beyond informing primate ecology and management, our results highlight the conservation importance of Lake Manyara National Park for primate conservation.

Settling velocity and pollination dynamics in Diarrhena obovata, a grass of temperate forest edges and understories

Pollen from a naturally occurring population of the forest grass species Diarrhena obovata was successfully captured in a series of pollen traps to understand the timing of anthesis and the dispersal mechanics of wind pollination in an example of the flowering plant family Poaceae. Scanning electron microscopy was used to identify the pollen surface ornamentation as microechinate-areolate. The spherical grains have a diameter of 38.74 μm. The settling velocity calculated by Stoke’s Law was 4.48 cm s-1, but physical measurement by drop tower experiments resulted in 3.77 ± 0.15 cm s-1 (sd). The surface ornamentation observed in D. obovata pollen is not expected to alter drag forces considerably but the reduction of settling velocity may be a result of species-specific pollen grain density. In forest grasses an improvement in settling velocity may be adaptive in overcoming dispersal constraints in an environment where trees obstruct wind speeds and create more turbulence.

Relation of pine crop damage to species-specific density in a multi-ungulate assemblage

Deer management in forest ecosystems requires information on deer densities and impacts to inform culling decisions with a known target density for acceptable damage levels. In multi-ungulate assemblages, managers need knowledge of relative impacts by different species or guilds. In an extensive (195 km2) conifer forest in eastern England, we related Scots pine (Pinus sylvestris) leader damage (% dominant shoots browsed) in 48 restocked stands (1–3 years growth) over multiple years (n = 79 observations) to species-specific annual muntjac (Muntiacus reevesi), roe (Capreolus capreolus), fallow (Dama dama) and “large deer” densities (composite of annual fallow and multi-year mean red deer Cervus elaphus) using generalized mixed effects models. Forest-wide density surface models were calibrated through intensive annual thermal imaging distance transects and local densities around stands resampled within confidence bounds. Models also examined effects of ground vegetation and hare presence (Lepus europaeus). More pine leaders were browsed at higher fallow or large deer densities (22% and 18%, respectively, increased leader damage across inter-quartile range). Leader damage intensity was not influenced by ground vegetation, hares, muntjac (across the range 8.3–41.6 individuals km−2) or roe deer density (1.7–19.4 individuals km−2). To reduce pine crop damage to economically acceptable levels, managers need to reduce fallow deer to a density as low as 0.6 individuals km−2 (CI = 0.06–1.44, which is considered impractical) or reduce combined large deer density to 2.3 (CI = 1.18–3.46) individuals km−2. Reducing muntjac or roe abundance would minimally affect leader damage in this system, but may be important for other tree species. Multi-species deer management requires species-specific understanding of impacts and robust density estimates.

Sleep Disordered Breathing and Recurrent Tonsillitis Are Associated With Polymicrobial Bacterial Biofilm Infections Suggesting a Role for Anti-Biofilm Therapies.

BackgroundThe underlying pathogenesis of pediatric obstructive sleep disordered breathing (SDB) and recurrent tonsillitis (RT) are poorly understood but need to be elucidated to develop less invasive treatment and prevention strategies.MethodsChildren aged between 1- and 16-years undergoing adenoidectomy, tonsillectomy or adenotonsillectomy for SDB (n=40), RT alone (n=18), or both SDB and RT (SDB+RT) (n=17) were recruited with age-matched healthy controls (n=33). Total bacterial load and species-specific densities of nontypeable Haemophilus influenzae (NTHi), Staphylococcus aureus, Streptococcus pyogenes, Streptococcus pneumoniae and Moraxella catarrhalis were measured by qPCR in nasopharyngeal swabs, oropharyngeal swabs, adenoid and tonsillar tissue from children with SDB, SDB+RT and RT, and in naso- and oro- pharyngeal swabs from healthy children. A subset of tonsil biopsies were examined for biofilms using 16S rRNA FISH (n=3/group).ResultsThe 5 bacterial species were detected in naso- and oro- pharyngeal samples from all children. These species were frequently detected in adenotonsillar tissue (except S. aureus, which was absent in adenoids) from children with SDB, SDB+RT and RT. NTHi and S. aureus were observed in tonsils from 66.7-88.2% and 33.3-58.8% of children respectively. Similar total and species-specific bacterial densities were observed in adenotonsillar tissue from children with SDB, SDB+RT or RT. Nasopharyngeal and oropharyngeal swabs were more likely to have multiple bacterial species co-detected than adenotonsillar tissue where one or two targeted species predominated. Polymicrobial biofilms and intracellular bacteria were observed in tonsils from children with adenotonsillar disease.ConclusionsAntimicrobials, particularly anti-biofilm therapies, may be a strategy for managing children with SDB.

Human and environmental associates of local species-specific abundance in a multi-species deer assemblage

Understanding how habitat, landscape context, and human disturbance influence local species-specific deer density provides evidence informing strategic management of increasing deer populations. Across an extensive (187 km2) heterogeneous forest-mosaic landscape in eastern England, spatially explicit density surface models of roe deer Capreolus capreolus and introduced muntjac Muntiacus reevesi were calibrated by thermal imaging distance sampling (recording 1590 and 400 muntjac and roe deer groups, respectively, on 567 km of driven transects). Models related deer density to local habitat composition, recreational intensity, and deer density (roe deer models controlled for muntjac density and vice versa) at a local grain across 1162 composite transect segments, incorporating geographical coordinates accounting for spatial autocorrelation. Abundance of both species was lower in localities with more grasslands (inter-quartile, IQ, effect size: roe −2.9 deer/km2; muntjac −2.9 deer/km2). Roe abundance (mean = 7 deer/km2, SD = 6) was greater in localities with more young stands (IQ effect size, + 1.3 deer/km2) and lower at localities with more recreationists (−1.1 deer/km2). Muntjac density (mean = 21 deer/km2, SD = 10) was greater in localities with more recreationists (+ 2.4 deer/km2), with more mature (≥ 46 years) stands (+ 1.5 deer/km2), or calcareous soil (+ 7.1 deer/km2). Comparison of models incorporating candidate variables and models comprising geographical coordinates only shows candidate variables to be weak predictors of deer densities. Adapting forest management to manipulate habitat and recreational access may influence local deer densities, but only subtly: effect sizes are not sufficient to mitigate deer impacts through planting vulnerable tree crops in areas avoided by deer. Effective culling remains the most viable management option.

Development of reproductive potential in protogynous coral reef fishes within Philippine no-take marine reserves.

Empirical evidence for increases in the reproductive potential (egg output per unit area) of coral reef fish in no-take marine reserves (NTMRs) is sparse. Here, we inferred the development of reproductive potential in two species of protogynous reef fishes, Chlorurus bleekeri (Labridae: Scarinae) and Cephalopholis argus (Epinephelidae), inside and outside of Philippine NTMRs. We estimated key reproductive parameters and applied these to species-specific density and length data from 17 NTMRs (durations of protection 0-11 years) and paired fished sites (controls) in a space-for-time substitution approach. For C. argus, we also used density and length data collected almost annually over 29 years from a NTMR and an adjacent control at Apo Island. The results suggest that C. bleekeri can develop 6.0 times greater reproductive potential in NTMRs than controls after 11 years of protection, equivalent to approximately 582,000 more eggs produced 500 m-2 inside NTMRs. Enhancement of reproductive potential in C. argus was not evident after 11 years in the space-for-time substitution. At Apo Island NTMR, reproductive potential of C. argus increased approximately 6-fold over 29 years but NTMR/control ratios in reproductive potential decreased through time (from 3.2 to 2.4), probably due to spillover of C. argus from the NTMR to the control. C. argus was estimated to produce approximately 113,000 more eggs 500 m-2 inside Apo Island NTMR at the 29th year of protection. Ratios of reproductive potential between NTMR and controls in C. bleekeri and C. argus were often greater than corresponding ratios in density or biomass. The study underscores the importance of species-specific reproductive life history traits that drive variation in the development of larval fish subsidies that originate from NTMRs.

Effects of Habitat Restoration on Fish Communities in Urban Streams

Geomorphological alterations, hydrological disconnectivity and water pollution are among the dominant pressures affecting ecological integrity in urban streams. River restoration approaches often involve utilising in-stream structures to encourage flow heterogeneity and promote habitat diversity. However, few studies examine the success of such projects. In this study, fish density, biomass and community structure at paired restored and unrestored reaches across five tributaries of the River Thames were examined. Fish density varied among rivers and reaches but was generally higher at restored sites. Restored sites also exhibited higher overall fish biomass, attributed mainly to the presence of brown trout (Salmo trutta L.) at the River Wandle. Despite higher density and biomass values at restored sites, the community structure analysis did not identify strong links between either river or restoration status using either species-specific density or biomass. Our results highlight that although reach-scale restoration can lead to localised increases in species density and biomass, this may chiefly be due to aggregation owing to preferential habitats created through restoration activities at these sites. Over larger spatial scales, significant improvements to species richness and diversity are likely to be limited due to the poor water quality and disconnected nature of these urban streams. Whilst reach-scale restoration clearly has the potential to provide preferential habitats for fish species, future efforts should focus on improving connectivity for fish across the wider Thames basin network by removing barriers to passage, improving water quality, restoring watershed processes and creating well-connected, diverse habitats which can facilitate the survival of a wide array of fish species throughout their life cycle.

Canopy Disturbances Catalyse Tree Species Shifts in Swiss Forests

Widely observed inertia of forest communities contrasts with climate change projections that suggest dramatic alterations of forest composition for the coming decades. Disturbances might be a key process to catalyse changes in tree species composition under environmental change by creating opportunities for ‘new’ species to establish. To test this assumption, we compared two assessments (1993–1995, 2009–2017) from the Swiss National Forest Inventory to evaluate which forests were opened by natural canopy disturbance (that is, wind, insect outbreaks, fire and drought) and if these disturbances altered tree species composition both in terms of species-specific basal area and recruitment densities. Natural disturbances affected 14% of the Swiss forests within 25 years, with wind and insect outbreaks being the most frequent (75%) and fire and drought being rare (< 1.5%). Disturbances led to a shift from conifer to broadleaf tree species at low elevation, in particular in dense Picea abies stands, but no change was observed at higher elevations. The composition of undisturbed sites persisted during the same period. Our results demonstrate that undisturbed forests widely resist changes in tree species composition as an effect of direct ingrowth by stand-forming species. Disturbance events seem necessary to create opportunities for climatically ‘better suited and site-adapted’ species to (re-)establish and therefore potentially catalyse tree species turnover under environmental changes. We detected a reduction of tree species that were—centuries ago—cultivated outside their primary natural range, in particular P. abies, or depended on traditional management practices (Pinus sylvestris, Castanea sativa), which may inform us on how the projected increase in disturbance frequency and severity might filter tree species composition and hereby alter forest structure.

Species-specific basic stem-wood densities for twelve indigenous forest and shrubland species of known age, New Zealand

Background: Tree carbon estimates for New Zealand indigenous tree and shrub species are largely based on mean basic stem-wood densities derived from a limited number of trees, often of unspecified age and from a limited number of sites throughout New Zealand. Yet stem-wood density values feed directly into New Zealand’s international and national greenhouse gas accounting. We augment existing published basic stem-wood density data with new age-specific values for 12 indigenous forest and shrubland species, including rarely obtained values for trees &lt;6-years old, across 21 widely-distributed sites between latitudes 35° and 46° S, and explore relationships commonly used to estimate carbon stocks. Methods: The volume of 478 whole stem-wood discs collected at breast height (BH) was determined by water displacement, oven dried, and weighed. Regression analyses were used to determine possible relationships between basic stem-wood density, and tree height, root collar diameter (RCD), and diameter at breast height (DBH). Unbalanced ANOVA was used to determine inter-species differences in basic stem-wood density in 5-yearly age groups (i.e. 0–5 years, 6–10 years etc.) (P&lt;0.05). As specific taxa of Kunzea ericoides (Myrtaceae) has only been identified at some study sites we combine the data from each site, and use the term Kunzea spp. We compare our age- and species-specific results with existing published data where age is specified versus non-age-specific values. Results: Kunzea spp. and Leptospermum scoparium exhibited positive correlations between basic stem-wood density and tree height, RCD, and DBH. No relationships were established for Melicytus ramiflorus, Coprosma grandiflora, Weinmannia racemosa ?6-years old, or for Podocarpus totara, Agathis australis, Vitex lucens, and Alectryon excelsus &lt;6-years old. Dacrydium cupressinum and Prumnopitys ferruginea &lt;6-years old exhibited a significant positive relationship with DBH only, while for Dacrycarpus dacrydioides, each correlation was negative. Irrespective of age, basic stem-wood density is not different between the hardwood species L. scoparium and Kunzea spp. but is significantly greater (P=0.001) than that of the remaining, and predominantly softwood species of equivalent age. For Kunzea spp., L. scoparium, Coprosma grandiflora, Weinmannia racemosa, and Melicytus ramiflorus ?6-years old there was no evidence that basic stem-wood density increased with tree age, and values were within the range of published and unpublished data. For naturally reverting stands of Kunzea spp. located between latitudes 35° to 46° S, basic stem-wood density values tended to increase with decreased elevation and increased temperature. Conclusions: Increasing basic wood density values in Kunzea spp. with decreased elevation and increased temperature suggest that where local data are available its use would improve the accuracy of biomass estimates both locally and nationally. Furthermore, refining biomass estimates for existing communities of mixed softwood species, stands of regenerating shrubland, and new plantings of indigenous species will require additional basic stem-wood density values for scaling from stem wood volume to total stand biomass.

Growth–density relationship in mixed stands – Results from long-term experimental plots

Forest management mainly controls wood growth through the regulation of stand density. Knowledge of the growth–density relationship is based on numerous studies in pure stands. Currently, in times of more climate plasticity and more nature-oriented forests, silviculture with mixed stands is demanded of forest policy. It is well known that the competition mechanisms in mixed stands are different to those of pure stands. Hence, the question arises for forest managers whether the regulation of density must be different, too.In an attempt to answer this question, we investigated 481 stand surveys from 124 long-term experimental plots of European beech stands, mixed with conifers and also broadleaf trees. With generalized additive models, we estimated the influence of the density on stand volume growth and how it changed with stand development and shade tolerance of the admixed species. The density of the mixed stands was given on a relative scale. 100% density took into account the maximum species-specific density plus a mixed stand specific addition.We found that mixed stands have a constant growth level in the medium- to high-density phase (70–100%). Although we have tried to take into account the higher density in mixed stands, 10% of the stands outperformed the 100% benchmark and exhibited a growth gain in this over-dense phase (>100%). Finally, the growth-density response resembles a cubic function with a saddle or optimum between medium- to high-density phase and an increase of growth in the low-density and the over-density phase. The inclusion of stand development led to the oblation of the growth–density response in younger ages. The admixture of shade-intolerant species with beech caused a more intensified cubic course of the relationship.Finally, we could show that a short-term decrease of the density also has an effect on growth. In terms of growth, weak thinnings are better than severe thinnings. Thinnings from above have a significant positive effect on growth, especially for longer observation periods of up to 10 years.We concluded that mixed stands need an adapted thinning compared to pure stands. Regular, weak thinnings from above with a very high stand density enables maximum volume growth gains in European beech mixed stands. We could show that the growth-density relationship is conceptually different to pure stands, because mixing effect causes density section above 100%. However, the study emphasizes the need for a systematic experimental setup for a better understanding of intraspecific interactions at different densities.

Macroinvertebrates as umbrella species on sandy beaches

The aim of the present study was to investigate macroinvertebrates from sandy beaches according to their umbrella potential worldwide. A meta-analysis was performed on a global scale, including 13 marine ecoregions. Community richness and species-specific density of 235 beaches and 726 surveys were retrieved from 48 articles. An index (UI) to select umbrella species was applied according to three categories: percentage of co-occurring species (PCS), median rarity (RAR) and sensitivity to human impacts (DS), which was based on a common statistic representing the magnitude of disturbances in meta-analysis (response ratios). PCS, RAR and DS of the umbrella species were compared with the median ± 95% confidence intervals calculated for all other non-umbrella species. Umbrella potential was higher for species co-occurring in different beach types. Most umbrella taxa responded negatively to human disturbances. These taxa also showed higher percentage of co-occurring species than the mean value (±95% confidence intervals) of non-umbrella species. Macroinvertebrates were ecological indicators of human disturbances and umbrella species, suggesting a good cost-benefit relationship for their application in beach monitoring. The baseline provided in the present study on applying the concept of umbrella species on sandy beaches supports the usefulness of these species in the restoration of urban beaches, monitoring of beaches with social-ecological conflicts and their full protection into reserves.

Monitoring deer food and browsing in forests: Coherence and discrepancies between national and local inventories

Field-based monitoring of deer food availability and browsing on recruiting forest trees is a necessary but labour-intensive task. We explored how such estimates from a low-resolution multipurpose national forest inventory (NFI) (plot density 0.3 km−2) corresponded with estimates from local inventories that specifically and in greater detail monitor the availability of deer food and browsing intensity (LFI) (plot density 2–3 km−2).We used NFI and LFI data from 16 moose Alces alces ranges (mean area 276 ± SE 69 km2) in southern Norway. Only the height segment 30–130 cm of browsable trees could be obtained from the NFI data, while moose can browse trees from 30 to 300 cm in height. According to the LFI, the browse species did not have similar proportions of their browsable stems below 130 cm. Using only the stems from heights of 30–130 cm overestimated the availability of RAS (rowan, aspen and sallow) relative to birch (silver birch and downy birch) and Scots pine.The browsable biomass per stem of each species also varied between ranges, which introduces uncertainty to the food availability estimates that are based on stems only. Nevertheless, the NFI density of stems at 30–130 cm heights can be a useful index for species-specific comparisons of browse availability across ranges, because the variations between ranges in stem densities outweighed the biomass variations per stem. The NFI and LFI estimates of the species-specific densities of stems at 30–130 cm heights were significantly related and close to isometric (1:1), especially for RAS and pine.We did not find strong relationships between NFI and LFI in the browsing intensity (i.e. proportion of shoots that were browsed during the winter). The explained variation was only 11% (R2) for RAS (p = 0.281) and 32% for pine (p = 0.028). This was likely due to the small sample sizes of browsed trees in the NFI and methodological differences between the NFI and LFI in how browsing intensity is estimated. ConclusionsUsing data from national forest inventories can be an efficient but low-resolution way to monitor browse availability for deer, provided that the monitoring includes the full range of tree heights reachable for the deer (e.g., 30–300 cm for moose). It is also a prerequisite that the number of NFI plots is sufficient to cover the spatial variability of the area. Regarding browsing intensities, adjustments in both the NFI and LFI approaches are needed to make the two monitoring schemes more comparable.

Drawn out of the shadows: Surveying secretive forest species with camera trap distance sampling

Abstract With animal species disappearing at unprecedented rates, we need an efficient monitoring method providing reliable estimates of population density and abundance, critical for the assessment of population status and trend. We deployed 160 camera traps (CTs) systematically over 743 locations covering 17,127 km2 of evergreen lowland rainforest of Salonga National Park, block South, Democratic Republic of the Congo. We evaluated the applicability of CT distance sampling (CTDS) to species different in size and behaviour. To improve precision of estimates, we evaluated two methods estimating species' availability (‘A’) for detection by CTs. We recorded 16,700 video clips, revealing 43 different animal taxa. We estimated densities of 14 species differing in physical, behavioural and ecological traits, and extracted species‐specific availability from available video footage using two methods (a) ‘ACa’ (Cappelle et al. [2019] Am. J. Primatol., 81, e22962) and (b) ‘ARo’ (Rowcliffe et al. [2014] Methods Ecol. Evol. 5, 1170). With sample sizes being large enough, we found minor differences between ACa and ARo in estimated densities. In contrast, low detectability and reactivity to the camera were main sources of bias. CTDS proved efficient for estimating density of homogenously rather than patchily distributed species. Synthesis and applications. Our application of camera trap distance sampling (CTDS) to a diverse vertebrate community demonstrates the enormous potential of this methodology for surveys of terrestrial wildlife, allowing rapid assessments of species' status and trends that can translate into effective conservation strategies. By providing the first estimates of understudied species such as the Congo peafowl, the giant ground pangolin and the cusimanses, CTDS may be used as a tool to revise these species' conservation status in the IUCN Red List of Threatened Species. Based on the constraints we encountered, we identify improvements to the current application, enhancing the general applicability of this method.

Evaluating spatio-temporal dynamics of multiple fisheries-targeted populations simultaneously: A case study of the Bohai Sea ecosystem in China

Development of joint species distribution models allows for improved and simultaneous estimates of various metrics for evaluating spatio-temporal patterns in multi-population dynamics, as essential tools for promoting ecosystem management and conservation. However, such tools are rarely used to simultaneously evaluate the spatio-temporal dynamics of multiple fisheries-targeted populations in an ecosystem. This study aims to fill this gap with a case study of the Bohai Sea in China. A joint dynamic species distribution model was developed to estimate the distributions of 13 major fish and invertebrate populations in the Bohai Sea, using data from bottom trawl surveys conducted in spring during 2014 to 2018. We calculated the spatial ranges (i.e., the distance within which correlation coefficients between locations are always larger than 10%) for spatial variation and spatio-temporal variation in species-specific densities of this fished community. The model-based density estimates for these populations were used to calculate the mean center of density, effective area occupied, and total abundance index for each population by year. Results showed that the spatial ranges were respectively 84 km and 94 km for spatial and spatio-temporal variation in the distributions of targeted populations, suggesting large variability in the community structure at a distance >100 km. Fish populations showed larger fluctuations in the mean center of density and effective area occupied than crustaceans and cephalopods, while most of the 13 populations tended to shift northeastward to deeper waters over the five years. Additionally, 12 of the 13 populations showed a sharp increase in total abundance in the spring of 2017 under the force of increasingly conservational fisheries management since 2017. In 2018, the total abundance indices remained high for most fish populations, but showed an abrupt decrease for all six of the invertebrate populations. These results indicate that major fish and invertebrate populations in a simplified ecosystem could differ in their responses to habitat changes, management or other human activities in a rapid manner, suggesting a demand for adaptive fisheries management at system scale for degraded/declining ecosystems worldwide.

Responses of a wild ungulate assemblage to anthropogenic influences in Manas National Park, India

Large carnivores have experienced significant global range contractions and recovering their populations is often contingent on increasing prey abundances. In Manas National Park (MNP), following nearly two decades of ethnopolitical conflict, studies document that populations of both prey and predators were depressed. Here we assess the status of wild ungulates in a section of MNP (Bansbari-Bhuyanpara) that has remained conflict-free for over a decade. For seven ungulate species, we estimate species-specific densities using distance-based sampling, assess species-specific space-use patterns in relation to habitat variables within an occupancy framework and examine patterns of temporal activity in relation to times when people access the park for resources. Further, by comparing temporal activity patterns of ungulates between MNP, a site where local communities access the park for resources, and Kaziranga National Park, where human use of the park is minimal, we examine if species activity is altered in response to human presence. We estimate that currently Bansbari-Bhuyanpara ranges of MNP support 42.66 (34.16–51.16) individual ungulates/km2. Our results highlight that current patterns of human access within the park affect both spatial and temporal behaviour of these species. Although we estimate a relatively high recovery potential for tigers in MNP given current prey densities, we suggest that further ungulate population recoveries could be supported in the park. With several ungulate species experiencing range-wide declines, efforts to minimize non-lethal human disturbances on these species also need to be considered to ensure that predator-prey systems remain intact.

Community-based wildlife management area supports similar mammal species richness and densities compared to a national park.

Community‐based conservation models have been widely implemented across Africa to improve wildlife conservation and livelihoods of rural communities. In Tanzania, communities can set aside land and formally register it as Wildlife Management Area (WMA), which allows them to generate revenue via consumptive or nonconsumptive utilization of wildlife. The key, yet often untested, assumption of this model is that economic benefits accrued from wildlife motivate sustainable management of wildlife. To test the ecological effectiveness (here defined as persistence of wildlife populations) of Burunge Wildlife Management Area (BWMA), we employed a participatory monitoring approach involving WMA personnel. At intermittent intervals between 2011 and 2018, we estimated mammal species richness and population densities of ten mammal species (African elephant, giraffe, buffalo, zebra, wildebeest, waterbuck, warthog, impala, Kirk's dik‐dik, and vervet monkey) along line transects. We compared mammal species accumulation curves and density estimates with those of time‐matched road transect surveys conducted in adjacent Tarangire National Park (TNP). Mammal species richness estimates were similar in both areas, yet observed species richness per transect was greater in TNP compared to BWMA. Species‐specific density estimates of time‐matched surveys were mostly not significantly different between BWMA and TNP, but elephants occasionally reached greater densities in TNP compared to BWMA. In BWMA, elephant, wildebeest, and impala populations showed significant increases from 2011 to 2018. These results suggest that community‐based conservation models can support mammal communities and densities that are similar to national park baselines. In light of the ecological success of this case study, we emphasize the need for continued efforts to ensure that the BWMA is effective. This will require adaptive management to counteract potential negative repercussions of wildlife populations on peoples' livelihoods. This study can be used as a model to evaluate the effectiveness of wildlife management areas across Tanzania.