Effect of sand mining on riparian landcover transformation in Dallung-Kukou catchment of the White Volta basin, Ghana

Rapid urbanization has increased demand for sand in the construction industry to meet housing and infrastructure needs of urban population. The Dallung-Kukuo catchment of the White Volta River Basin is a major sand mining site for the construction industry in Tamale and other peri-urban communities. On the contrary, the river serves as a major source of water supply to the population. Riparian vegetation is essential to water protection, but research has focused extensively on the impact of sand mining on water quality in the river basin. The present study employed GIS and remote sensing techniques coupled with in-situ vegetation sampling to assess riparian land cover changes from 1990 to 2021. Land cover images of the catchment revealed a 14.9% increase in sand mining area, while river bed area and woodland cover decreased by 0.7% and 20%, respectively, from 1990 to 2021. A comparison of woody plant diversity also showed a higher Shannon diversity index in the unmined area of the riparian zone (3.0) compared to the sand mining area (2.0). Environmental Protection Agency and traditional authorities should intensify monitoring to protect the White Volta basin from unsustainable exploitation.

Worse sleep and increased energy expenditure yet no movement changes in sub-urban wild boar experiencing an influx of human visitors (anthropulse) during the COVID-19 pandemic

Expansion of urban areas, landscape transformation and increasing human outdoor activities strongly affect wildlife behaviour. The outbreak of the COVID-19 pandemic in particular led to drastic changes in human behaviour, exposing wildlife around the world to either reduced or increased human presence, potentially altering animal behaviour. Here, we investigate behavioural responses of wild boar (Sus scrofa) to changing numbers of human visitors to a suburban forest near Prague, Czech Republic, during the first 2.5 years of the COVID-19 epidemic (April 2019-November 2021). We used bio-logging and movement data of 63 GPS-collared wild boar and human visitation data based on an automatic counter installed in the field. We hypothesised that higher levels of human leisure activity will have a disturbing effect on wild boar behaviour manifested in increased movements and ranging, energy spent, and disrupted sleep patterns. Interestingly, whilst the number of people visiting the forest varied by two orders of magnitude (from 36 to 3431 people weekly), even high levels of human presence (>2000 visitors per week) did not affect weekly distance travelled, home range size, and maximum displacement of wild boar. Instead, individuals spent 41 % more energy at high levels of human presence (>2000 visitors per week), with more erratic sleep patterns, characterised by shorter and more frequent sleeping bouts. Our results highlight multifaceted effects of increased human activities ('anthropulses'), such as those related to COVID-19 countermeasures, on animal behaviour. High human pressure may not affect animal movements or habitat use, especially in highly adaptable species such as wild boar, but may disrupt animal activity rhythms, with potentially detrimental fitness consequences. Such subtle behavioural responses can be overlooked if using only standard tracking technology.

Using dynamic data reconciliation to improve the performance of PID feedback control systems with Gaussian/non-Gaussian distributed disturbance and measurement noise

For a stochastic PID feedback control system, the uncertainty of the working environment often leads to the unsatisfied performance of the system, which does not meet the profit requirements. The working environment generally includes external disturbance and measurement noise, etc. Gaussian distributed measurement noise and disturbances are widely considered while non-Gaussian distributed measurement noise and disturbances are rarely considered. In this paper, the performance degradation of Gaussian/non-Gaussian disturbances and measurement noise on a stochastic PID feedback system is considered and analyzed. An efficient method, dynamic data reconciliation (DDR) is developed to filter measurement noise and disturbances and improve the performance of the stochastic PID feedback control system. By utilizing model-based and measured information, DDR avoids time delays in output estimation. With the detailed theoretical analysis and simulation verification, the effectiveness of the proposed DDR technology on the stochastic PID feedback control system is verified. Compared with conventional exponential filters, DDR can achieve better control performance. The proposed DDR is also used for the control system of the DC-AC​ converter. The improved effect of DDR on the output quality is demonstrated by the results.

Colonisation after disturbance on artificial structures: The influence of timing and grazing

Artificial structures are poor surrogates of natural rocky shores, meaning they generally support depauperate assemblages. These differences may result from a combination of recruitment processes, biotic interactions, and structuring by environmental factors. In this study, plots were cleared on two seawalls and two natural shores at two separate timepoints - in August 2020 (summer) and February 2021 (winter) - and monitored over one year to determine the influence of timing of disturbance on recruitment and succession. Additional plots were cleared at one of the seawalls at a single timepoint in August 2020, and exclusion cages were installed to determine the influence of grazing pressure on colonisation; these were monitored for 18 months. Disturbance during winter resulted in higher concentrations of all biofilm components up to 3 months, but did not impact benthic community composition beyond this point. Grazer exclusion on artificial structures increased biofilm concentrations and influenced community composition in comparison to plots on artificial structures without exclusion, while communities on natural surfaces differed in terms of species composition to those on artificial plots at 12 months. We conclude that the timing of routine maintenance works on artificial structures may impact initial biofilm abundances. Furthermore, while grazing pressure does influence community structure on artificial structures, this alone is not sufficient to explain biological differences between artificial structures and natural shores.

A novel framework for vegetation change characterization from time series landsat images

Understanding terrestrial ecosystem dynamics requires a comprehensive examination of vegetation changes. Remote sensing technology has been established as an effective approach to reconstructing vegetation change history, investigating change properties, and evaluating the ecological effects. However, current remote sensing techniques are primarily focused on break detection but ignore long-term trend analysis. In this study, we proposed a novel framework based on a change detection algorithm and a trend analysis method that could integrate both short-term disturbance detection and long-term trends to comprehensively assess vegetation change. With this framework, we characterized the vegetation changes in Zhejiang Province from 1990 to 2020 using Landsat and landcover data. Benefiting from combining break detection and long-term trend analysis, the framework showcased its capability of capturing a variety of dynamics and trends of vegetation. The results show that the vegetation was browning in the plains while greening in the mountains, and the overall vegetation was gradually greening during the study period. By comparison, detected vegetation disturbances covered 57.71% of the province's land areas (accounting for 66.92% of the vegetated region) which were mainly distributed around the built-up areas, and most disturbances (94%) occurred in forest and cropland. There were two peak timings in the frequency of vegetation disturbances: around 2003 and around 2014, and the proportions of more than twice disturbances in a single location were low. The results illustrate that this framework is promising for the characterization of regional vegetation growth, including long-term trends and short-term features. The proposed framework enlightens a new direction for the continuous monitoring of vegetation dynamics.

Anchor scour from shipping and the defaunation of rocky reefs: A quantitative assessment

Anchor scour from shipping is increasingly recognised as a global threat to benthic marine biodiversity, yet no replicated ecological assessment exists for any seabed community. Without quantification of impacts to biota, there is substantial uncertainty for maritime stakeholders and managers of the marine estate on how these impacts can be managed or minimised. Our study focuses on a region in SE Australia with a high proportion of mesophotic reef (>30 m), where ships anchor while waiting to enter nearby ports. Temperate mesophotic rocky reefs are unique, providing a platform for a diversity of biota, including sponges, ahermatypic corals and other sessile invertebrates. They are rich in biodiversity, provide essential food resources, habitat refugia and ecosystem services for a range of economically, as well as ecologically important taxa. We examined seven representative taxa from four phyla (porifera, cnidaria, bryozoan, hydrozoa) across anchored and 'anchor-free' sites to determine which biota and which of their morphologies were most at risk. Using stereo-imagery, we assessed the richness of animal forest biota, morphology, size, and relative abundance. Our analysis revealed striking impacts to animal forests exposed to anchoring with between three and four-fold declines in morphotype richness and relative abundance. Marked compositional shifts, relative to those reefs that were anchor-free, were also apparent. Six of the seven taxonomic groups, most notably sponge morphotypes, exhibited strong negative responses to anchoring, while one morphotype, soft bryozoans, showed no difference between treatments. Our findings confirm that anchoring on reefs leads to the substantial removal of biota, with marked reductions of biodiversity and requires urgent management. The exclusion of areas of high biological value from anchorages is an important first step towards ameliorating impacts and promoting the recovery of biodiversity.

Anthropogenically driven spatial niche partitioning in a large herbivore assemblage

Understanding how human activity can influence species distributions and spatial niche partitioning between sympatric species is a key area of contemporary ecology. Extirpations of large mammalian populations, the result of a 15-year civil war, within the Gorongosa National Park in Mozambique, have been followed by an extended period of restoration. The species-specific recovery of these populations has provided an ideal system to identify how niche partitioning between coexisting species is altered as a consequence of extreme disturbance events. Here, we aimed to understand how distribution patterns of grazing herbivores, as well as spatial niche overlap between them, changed between the pre- and post-war scenarios. We focused on the following four grazer species: buffalo (Syncerus caffer); sable (Hippotragus niger); waterbuck (Kobus ellipsiprymnus); and zebra (Equus quagga). Using long-term aerial survey data, we quantified range size for each species, as well as spatial niche overlap between each species pair, for pre- and post-war periods. Range size of buffalo and zebra decreased drastically from the pre-war period; with both species inhabiting subsets of their historical distribution in the park. Sable and waterbuck have both colonised historically avoided habitat, with waterbuck doubling their pre-war range size. Spatial overlap between all four grazers pre-war was significantly high, indicating niche similarity; however, this decreased in the post-war period, with some species pairs displaying spatial niche dissimilarity. Our findings highlight how population responses to anthropogenic disturbance can result in significant alterations to species' distributions, with consequences for patterns of niche similarity.

The behavior of Broad-tailed hummingbirds is altered by cycles of human activity in a forested area converted into agricultural land

Background

By changing the circumstances in which animals make their behavioral decisions, weekly cycles of human activity might cause changes in wildlife behavior. For example, when there is more human activity in a location, animals may become more vigilant, which can decrease the time they spend foraging, or roam farther from home, leading to increased home range size. Overall, there has been little exploration of how animal species living in locations that have undergone land use change are affected by the temporal dynamics of human activity levels. In this study, we aimed to analyze the effect of the weekend on agricultural activities and hummingbird territorial activity. We examined differences between weekdays and weekends in factors previously shown to follow weekly cyclical patterns, such as pedestrian presence, traffic, and the presence of domestic animals. We hypothesized that territorial hummingbirds would respond to these weekly cycles of human activity by altering their behavior.

Methods

We studied Broad-tailed hummingbird territories in forested areas that had been transformed to agriculture lands in central Mexico. We evaluated whether territorial individuals changed their behaviors (i.e., chases of intruders, foraging within their territory, number of intruders allowed to forage in the territory) in response to variation between weekdays and weekends in the number of pedestrians, cyclists, dogs, farm animals and vehicles.

Results

We found that the level of agriculture-related human activities showed a weekly cycle at our study site. On weekdays there was higher traffic of pedestrians, cyclists, dogs, farm animals and vehicles, compared to the weekends. Hummingbirds responded to these weekday-weekends differences by changing their territorial behavior. Compared to weekends, on weekdays hummingbirds showed a decrease in defense (number of chases) as well as the use of their territory (number of flowers visited), which allowed increased access to intruders (number of visited flowers by intruders).

Conclusions

Our findings suggest that variation in agriculture-related human activities between weekdays and weekends can alter the territorial behavior of hummingbirds. Behavioral shifts seem to be related to these human activity cycles, leading hummingbirds to reduce chases and feeding during weekdays when human activity is highest, but increasing both behaviors during times of minimal disturbance.

Acute stress and restricted diet reduce bill-mediated heat dissipation in the song sparrow (Melospiza melodia): implications for optimal thermoregulation

We used thermal imaging to show that two environmental factors - acute stress and diet - influence thermoregulatory performance of a known thermal window, the avian bill. The bill plays important roles in thermoregulation and water balance. Given that heat loss through the bill is adjustable through vasoconstriction and vasodilation, and acute stress can cause vasoconstriction in peripheral body surfaces, we hypothesized that stress may influence the bill's role as a thermal window. We further hypothesized that diet influences heat dissipation from the bill, given that body condition influences the surface temperature of another body region (the eye region). We measured the surface temperature of the bills of song sparrows (Melospiza melodia) before, during and after handling by an observer at 37°C ambient temperature. We fed five birds a restricted diet intended to maintain body mass typical of wild birds, and we fed six birds an unrestricted diet for 5 months prior to experiments. Acute stress caused a decrease in the surface temperature of the bill, resulting in a 32.4% decrease in heat dissipation immediately following acute stress, before recovering over approximately 2.3 min. The initial reduction and subsequent recovery provide partial support for the hemoprotective and thermoprotective hypotheses, which predict a reduction or increase in peripheral blood flow, respectively. Birds with unrestricted diets had larger bills and dissipated more heat, indicating that diet and body condition influence bill-mediated heat dissipation and thermoregulation. These results indicate that stress-induced vascular changes and diet can influence mechanisms of heat loss and potentially inhibit optimal thermoregulation.

Nitrogen and light regulate symbiotic nitrogen fixation by a temperate forest tree

Symbiotic nitrogen fixation (SNF) is a critical mechanism of ecosystem recovery, and in forests of the eastern United States, the most common tree species that supports SNF is black locust (Robinia pseudoacacia L.). Despite its prevalence, black locust's fixation strategy-whether it maintains fixation at a constant rate (obligate fixation) or reduces its fixation rate (facultative fixation)-is unknown. Here, we examined how nitrogen and light control SNF by black locust, by growing seedlings under two nitrogen levels and across four levels of light. Seedlings were harvested after 12 weeks to determine biomass changes, nodule activity, and photosynthetic rates. Black locust seedlings increased biomass growth with increasing light, but only in the absence of nitrogen addition, while seedling root:shoot (biomass) modestly declined with increasing light regardless of nitrogen level. We found that black locust behaved like a facultative fixer, and regulated fixation by excising or maintaining nodules, and by controlling nodule biomass and activity. Specifically, nitrogen addition reduced seedling investment in nodule biomass (g g^-1) by 63%, and reduced seedling allocation to nitrogen fixation (µmol C₂H₄ g^-1 h^-1) by 66%. In contrast, light affected nitrogen fixation through two indirect pathways. First, light increased plant growth, and hence nitrogen demands, which caused an increase in nitrogen fixation proportional to biomass. Second, light increasd photosynthetic activity, which was positively associated with nodule activity, but only in the absence of nitrogen addition. Our findings for how black locust regulates SNF can improve predictions of ecosystem SNF under the changing environmental conditions.

The stimulatory effect and mechanism of low-dose lanthanum on soybean leaf cells

Light rare earth elements (LREEs) have been long used in agriculture (i.e., mainly via aerially applied LREE fertilizers) based on the fact that low-dose LREEs promote plant growth. Meanwhile, the toxic effects of low-dose LREEs on organisms have also been found. However, the cellular and molecular mechanism of low-dose LREEs acting on organisms remain unclear. Plants are at the beginning of food chains, so it is critical to uncover the cellular and molecular mechanism of low-dose LREEs on plants. Here, lanthanum (La) and soybean were the representatives of LREEs and plants, respectively. The effects of low-dose La on soybean leaves were investigated, and the stimulatory effect and mechanism of low-dose LREEs on leaf cells were revealed. Specifically, clathrin-mediated endocytosis (CME) activated by low-dose La is an influx channel for La in soybean leaf cells. The intracellular La and La-activated CME jointly disturbed multiple forms of intracellular homeostasis, including metallic element homeostasis, redox homeostasis, gene expression homeostasis. The disturbed homeostasis either stimulated cell growth or caused damage to the plasma membrane of soybean leaf cells. These results provide new insights for clarifying the cellular and molecular mechanisms of low-dose LREEs as a class of stimulators instead of nutrients to stimulate plants.

Assessing the effects of survey-inherent disturbance on primate detectability: Recommendations for line transect distance sampling

Habitat destruction and over-hunting are increasingly threatening the arboreal primates of Central Africa. To establish effective conservation strategies, accurate assessments of primate density, abundance, and spatial distribution are required. To date, the method of choice for primate density estimation is line transect distance sampling. However, primates fleeing human observers violate methodological assumptions, biasing the accuracy of resulting estimates. In this study, we used line transect distance sampling to study five primate species along 378 km of transects in Salonga National Park, Democratic Republic of the Congo. We tested the effect of different levels of survey-inherent disturbance (i.e., cutting) on the number of observed (i) primate groups, and (ii) individuals within groups, by counting groups at three different time lags after disturbance of the transect, (i) a minimum of 3 h, (ii) 24 h, (iii) a minimum of 3 days. We found that survey-inherent disturbance led to underestimated densities, affecting both the number of encountered groups and of observed individuals. However, the response varied between species due to species-specific ecological and behavioral features. Piliocolobus tholloni and Colobus angolenis resumed an unaltered behavior only 24 h after disturbance, while Lophocebus aterrimus, Cercopithecus ascanius, and Cercopithecus wolfi required a minimum of 10 days. To minimize bias in density estimates, future surveys using line transect distance sampling should be designed considering survey-inherent disturbance. We recommend evaluating the factors driving primate response, including habitat type, niche occupation, and hunting pressure, peculiar to the survey-specific area and primate community under study.

A field study of the surface disturbance effects of animals and motor vehicles on aeolian sediment emission from a silty playa surface

Dry playa surfaces can be extremely vulnerable to disturbance which breaks their surface crusts resulting in increased aeolian sand and dust emissions. Trampling by livestock and motor vehicles is an important source of this disturbance. The Hamoun Lakes in the Sistan region of Iran are a major source area of dust storms which are causing damage to infrastructure and communities. This study performed portable wind tunnel tests of controlled surface disturbance by animals (cow, sheep) and motor vehicles (automobile, motorcycle) on a silty playa surface of Hamoun Saberi lake. The aim of this study was to assess the effect of different levels of trampling and disturbed surfaces by both vehicles and livestock on dust emission at wind speeds of 6 and 12 m s^-1. A significant increase of sediment emission was found with increased number of passes of vehicles and livestock and the degree of surface disturbance, more so at the high wind speed (12 m s^-1). No significant differences were observed between a 10-20% disturbance level and an undisturbed surface, but statistically significant differences became apparent when disturbances reached 50-60% to 90-100% compared to undisturbed surfaces. Greater emission rates were reached by disturbances provided by automobile and cow compared to motorcycle and sheep, indicating greater trampling effects of automobile and cow likely related to greater weight and larger footprint. The automobile was the most surface-destructive of the four anthropogenic disturbances, providing emission in a lower number of passes compared to the motorcycle, cow and sheep. Better management of vehicle and livestock allocation on playas subject to disturbance, such as the Hamoun Lakes, will be a useful strategy to reduce disturbance and the frequency and intensity of dust storms.

Convergence in floodplain pond communities indicates different pathways to community assembly

Disturbance can strongly influence ecosystems, yet much remains unknown about the relative importance of key processes (selection, drift, and dispersal) in the recovery of ecological communities following disturbance. We combined field surveys with a field experiment to elucidate mechanisms governing the recovery of aquatic macroinvertebrates in habitats of an alluvial floodplain following flood disturbance. We monitored macroinvertebrates in 24 natural parafluvial habitats over 60 days after a major flood, as well as the colonization of 24 newly-built ponds by macroinvertebrates over 45 days in the same floodplain. We examined the sources of environmental variation and their relative effects on aquatic assemblages using a combination of null models and Mantel tests. We also used a joint species distribution model to investigate the importance of primary metacommunity structuring processes during recovery: selection, dispersal, and drift. Contrary to expectations, we found that beta diversity actually decreased among natural habitats over time after the flood or the creation of the ponds, instead of increasing. This result was despite environmental predictors showing contrasting patterns for explaining community variation over time in the natural habitats compared with the experimental ponds. Flood heterogeneity across the floodplain and spatial scale differences between the experimental ponds and the natural habitats seemingly constrained the balance between deterministic and stochastic processes driving the ecological convergence of assemblages over time. While environmental selection was the dominant structuring process in both groups, biotic interactions also had a prominent influence on community assembly. These findings have profound implications towards understanding metacommunity structuring in riverscapes that includes common linkages between disturbance heterogeneity, spatial scale properties, and community composition.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00027-023-00957-9.

Are really Nature-Based Solutions sustainable solutions to design future cities in a context of global change? Discussion about the vulnerability of these new solutions and their probable unsustainable implementation

The urban ecosystem is a very challenging environment that faces many problems such as various pollutions, higher temperatures than its surroundings or flooding risks due to soil sealing. Nature-based solutions (NBS) seem to be good option to address these problems, while simultaneously offering benefits for facing climate change and the biodiversity crisis. Despite their potential, NBS can be threatened by various urban disturbance, namely: land use change, pollution, or invasive species. These disturbances can have multiple consequences on urban NBS, such as causing changes in plant characteristics/traits, altering the services they provide, and even make certain plant populations disappear, etc. In turn, these consequences may even jeopardize the solutions themselves, which then may no longer solve the problems they originally targeted. To avoid this, NBS should be eco-designed, i.e. designed in function of their environment. Their management should be adaptive and should also take into consideration the evolution of climatic and anthropogenic factors. The choice of species should not be left to chance or random: In this sense, is it better to plant native species for biodiversity conservation or exotic species that are more likely to resist global changes? Is it better to find resistant or ruderal species that have proven themselves in the face of certain disturbances? In any case, it would be good to diversify any NBS to have a better chance of survival in the face of global changes.

Comprehensive analysis of the migration and transformation of nutrients between sediment and overlying water in complex habitat systems

Under the influence of environmental change, disturbance and other external conditions, sediments release internal nutrients to the overlying water and become a contamination source in the lake. Complex habitat systems provide a unique opportunity for determining the influences of environmental changes in lakes. In this study, Baiyangdian Lake (BYDL) was divided into different habitat systems (connected water areas, river courses, reed fields, lotus ponds, fishponds, farmland, and thorps) based on the influence of natural and artificial activities. The physical and chemical properties of overlying water and sediment in different habitat systems were investigated. In addition, statistical analytical methods were used to analyze the relationship between sediment characteristics and overlying water parameters in different habitat systems. The results showed that nitrogen and phosphorus in the overlying water could accumulate in the sediments, while disturbance was one of the main factors affecting the release of nutrients from sediments. Disturbance promoted the suspension of sediments and increased the oxygen content, thereby facilitating the internal release of nutrients. However, there were also some differences in the process of internal release of nutrients between the habitat systems. Nitrogen in the overlying water was closely related to the source of organic matter (r > 0.950), especially in the ponds (including lotus ponds, reed fields, and fishponds), and phosphorus was mainly influenced by turbidity (r > 0.870). In the river course (p = 0.198, n = 26), the disturbance and increase in pH promoted the internal release of nutrients from the sediments (contributions of 35.2 % and 25.1 %, respectively). In the ponds, the aquatic macrophytes reduced the release of nitrogen and phosphorus in sediments. Overall, this study provides more information on the migration and transformation of nutrients between sediment and overlying water in lakes with multiple habitats.

Patch and matrix characteristics determine the outcome of ecosystem engineering by mole rats in dry grasslands

Background

Burrowing mammals are important ecosystem engineers, especially in open ecosystems where they create patches that differ from the surrounding matrix in their structure or ecosystem functions.

Methods

We evaluated the fine-scale effects of a subterranean ecosystem engineer, the Lesser blind mole rat on the vegetation composition of sandy dry grasslands in Hungary. In this model system we tested whether the characteristics of the patch (mound size) and the matrix (total vegetation cover in the undisturbed grassland) influence the structural and functional contrasts between the mounds and the undisturbed grasslands. We sampled the vegetation of 80 mounds and 80 undisturbed grassland plots in four sites, where we recorded the total vegetation cover, and the occurrence and cover of each vascular plant species. We used two proxies to characterise the patches (mounds) and the matrix (undisturbed grassland): we measured the perimeter of the mounds and estimated the total vegetation cover of the undisturbed grasslands. First, we compared the vegetation characteristics of the mounds and the surrounding grasslands with general linear models. Second, we characterised the contrasts between the mounds and the undisturbed grassland by relative response indices (RRIs) of the vegetation characteristics studied in the first step.

Results

Species composition of the vegetation of the mounds and undisturbed grasslands was well separated in three out of the four study sites. Mounds were characterised by lower vegetation cover, lower cover of perennial graminoids, and higher diversity, and evenness compared to undisturbed grasslands. The contrast in vegetation cover between mounds and undisturbed grasslands increased with decreasing patch size. Increasing vegetation cover in the matrix grasslands increased the contrasts between the mounds and undisturbed grasslands in terms of total cover, perennial graminoid cover, diversity, and evenness. Our results suggest that mole rat mounds provide improved establishment conditions for subordinate species, because they are larger than other types of natural gaps and are characterised by less intense belowground competition. The ecosystem engineering effect, i.e., the contrast between the patches and the matrix was the largest in the more closed grasslands.

Negative impacts of human disturbances on the seed bank of subalpine forests are offset by climatic factors

Precipitation and temperature in the subalpine region have increased dramatically in recent decades due to global warming, and human disturbances have continued to impact the vegetation in the region. Seed bank plays an important role in population recovery, but there are few studies on the synergistic effects of human disturbances and climate change on seed bank. We analyzed the synergistic effects of human disturbances and climate change on seed bank samples from 20 sites in the subalpine coniferous forest region using grazing and logging as the disturbance intensity gradient and precipitation and temperature as climate variables. The species diversity of aboveground vegetation all changed significantly (p < 0.05) with precipitation, temperature and disturbance level, while the seed bank richness and density did not. Furthermore, the species composition of the seed bank varied significantly less than that of the aboveground vegetation at different levels of disturbance (p < 0.001). Thus, seed bank showed a strong buffering capacity against the risk of local extinction caused by environmental changes that shift the species composition and diversity of aboveground vegetation. In addition, soil and litter are important influences controlling seed bank density in subalpine forests, and the results of structural equation modelling suggest that both disturbance and climate change can indirectly regulate the seed bank by changing the physicochemical properties of soil and litter. We conclude that increases in precipitation and temperature driven by climate change can buffer the negative effects of disturbances on the seed bank.

Long-term effects of forest fires on fungal community and soil properties along a hemiboreal Scots pine forest fire chronosequence

We studied long-term effects of forest fires on the dynamics of soil fungal community along a post-fire chronosequence in hemiboreal Scots pine stands in north-western Estonia. Effects of fire on soil and fungi were studied on six sites that differed in time since fire (10, 21, 36, 67, 78 and 181 years ago), without further management interventions. Soil fungal communities along the chronosequence were dominated by soil saprotrophs and ectomycorrhizal (EcM) fungi. Across the chronosequence, the most dominant phylum was Ascomycota. The most abundant OTUs were identified as Umbelopsis sp., Hyaloscyphaceae sp. and Pezoloma ericae with relative abundances of 9.5, 8.9 and 6.8 %, respectively. Fungal species richness was similar among sample areas except in the area where fire occurred 36 years ago, where it was significantly lower. There were considerable differences in EcM fungal species composition along the chronosequence. The most recently burned site had Piloderma sphaerosporum, Pseudotomentella sp. and Clavulinaceae sp. as most abundant EcM OTUs while in three oldest burned areas Clavulinaceae sp. and Cortinarius sp. were abundant. Soil C and N stocks were lower in the most recently burned area but differences with other areas were not statistically significant. Soil pH had a significant effect on fungal species composition. Older areas had substantially lower pH compared to more recently burned areas.

Exploring fine-scale assembly of ectomycorrhizal fungal communities through phylogenetic and spatial distribution analyses

Ectomycorrhizal fungi (EMF) form symbiotic relationship with the roots of host plants. EMF communities are composed of highly diverse species; however, how they are assembled has been a long-standing question. In this study, we investigated from a phylogenetic perspective how EMF communities assemble on Pinus densiflora seedlings at different spatial scales (i.e., seedling scale and root tip scale). P. densiflora seedlings were collected from different habitats (i.e., disturbed areas and mature forests), and their EMF communities were investigated by morphotype sequencing and next-generation sequencing (NGS). To infer assembly mechanisms, phylogenetic relatedness within the community (i.e., phylogenetic structure) was estimated and spatial distribution of EMF root tips was analyzed. The EMF communities on pine seedlings were largely different between the two habitats. Phylogenetically restricted lineages (Amphinema, /suillus-rhizopogon) were abundant in the disturbed areas, whereas species from diverse lineages were abundant in the mature forests (Russula, Sebacina, /tomentella-thelephora, etc.). In the disturbed areas, phylogenetically similar EMF species were aggregated at the seedling scale, suggesting that disturbance acts as a powerful abiotic filter. However, phylogenetically similar species were spatially segregated from each other at the root tip scale, indicating limiting similarity. In the mature forest seedlings, no distinct phylogenetic signals were detected at both seedling and root tip scale. Collectively, our results suggest that limiting similarity may be an important assembly mechanism at the root tip scale and that assembly mechanisms can vary across habitats and spatial scales.

Gray whale density during seismic surveys near their Sakhalin feeding ground

Oil and gas development off northeastern Sakhalin Island, Russia, has exposed the western gray whale population on their summer-fall foraging grounds to a range of anthropogenic activities, such as pile driving, dredging, pipeline installation, and seismic surveys. In 2015, the number of seismic surveys within a feeding season surpassed the level of the number and duration of previous seismic survey activities known to have occurred close to the gray whales' feeding ground, with the potential to cause disturbance to their feeding activity. To examine the extent that gray whales were potentially avoiding areas when exposed to seismic and vessel sounds, shore-based teams monitored the abundance and distribution of gray whales from 13 stations that encompassed the known nearshore feeding area. Gray whale density was examined in relation to natural (spatial, temporal, and prey energy) and anthropogenic (cumulative sound exposure from vessel and seismic sounds) explanatory variables using Generalized Additive Models (GAM). Distance from shore, water depth, date, and northing explained a significant amount of variation in gray whale densities. Prey energy from crustaceans, specifically amphipods, isopods, and cumaceans also significantly influenced gray whale densities in the nearshore feeding area. Increasing cumulative exposure to vessel and seismic sounds resulted in both a short- and longer-term decline in gray whale density in an area. This study provides further insights about western gray whale responses to anthropogenic activity in proximity to and within the nearshore feeding area. As the frequency of seismic surveys and other non-oil and gas anthropogenic activity are expected to increase off Sakhalin Island, it is critical to continue to monitor and assess potential impacts on this endangered population of gray whales.

J, Martínez-Aguilar S, Viloria-Gómora L. Changes in whistle parameters of two common bottlenose dolphin ecotypes as a result of the physical presence of the research vessel

In the presence of vessels, dolphins have been found to change their habitat, behavior, group composition and whistle repertoire. The modification of the whistle parameters is generally considered to be a response to the engine noise. Little is known about the impact of the physical presence of vessels on dolphin acoustics. Whistle parameters of the coastal and oceanic ecotypes of common bottlenose dolphins in La Paz Bay, Mexico, were measured after the approach of the research vessel and its engine shutdown. Recordings of 10 min were made immediately after turning off the engine. For analysis, these recordings were divided from minute 0 to minute 5, and from minute 5:01 to minute 10. The whistles of the oceanic ecotype showed higher maximum, minimum and peak frequency in the second time interval compared to the first one. The whistle rate decreased in the second time interval. The whistles of the coastal ecotype showed no difference between the two time intervals. The physical presence of the research vessel could have induced a change in the whistle parameters of the oceanic dolphins until habituation to the vessel disturbance. The oceanic ecotype could increase the whistle rate and decrease the whistle frequencies to maintain acoustic contact more frequently and for longer distances. The coastal ecotype, showing no significant changes in the whistle parameters, could be more habituated to the presence of vessels and display a higher tolerance.

Effects and response of the Cerrado ground-layer to frost along the canopy cover gradient

Frost effects on savanna plant communities have been considered as analogous to those from fire, both changing community structure and filtering species composition. However, while frost impacts have been well-studied for the woody component of savannas, it is still poorly explored for the ground-layer community. Here, we investigated effects of frost in the Cerrado along a gradient of tree cover, focusing on ground-layer plant species, near the southern limit of the Cerrado in Brazil. We aimed to elucidate if the pattern already described for the tree layer also extends to the ground layer in terms of mimicking the effects of fire on vegetation structure and composition. We assessed how damage severity differs across species and across the tree-cover gradient, and we examined the recovery process after frost in terms of richness and community structure along the canopy cover gradient. Frost caused immediate and widespread dieback of the perennial ground-layer, with greatest impact on community structure where tree cover was lowest. However, frost did not reduce the number of species, indicating community resilience to this natural disturbance. Although frost mimicked the effects of fire in some ways, in other ways it differed substantially from fire. Unlike fire, frost increases litter cover and decreases the proportion of bare soil, likely hindering crucial processes for recovery of plant populations, such as seed dispersal, seed germination and plant resprouting. This finding calls attention to the risk of misguided conclusions when the ground layer is neglected in ecological studies of tropical savannas and grasslands.

Elevational changes in productivity of saplings relate to distribution of two congeneric tree species

Elevational changes in vegetation are associated with changes in environmental factors, an example of which is provided by the shade-tolerant Abies mariesii and less shade-tolerant Abies veitchii, which dominate forests at high and low elevations, respectively, in subalpine zones of central Japan. In this study, we sought to establish the factors underlying the differential elevational dominance of these two species from the perspective of sapling growth and survival. It is assumed that the growth and survival of saplings is greater at higher rates of surplus production (the value obtained by subtracting the minimum net production to maintain the current sapling leaf mass from the total net production), as sapling leaf mass gradually declines with time if saplings cannot maintain the current sapling leaf mass, thereby increasing the risk of premature mortality. In this regard, we aimed to verify the following two hypotheses: (1) at low elevations, the surplus production rate of A. veitchii is greater than that of A. mariesii in canopy gaps, and vice versa in the forest understory; and (2) at high elevation, the surplus production rate of A. mariesii is greater than that of A. veitchii in both forest understory and canopy gaps. The results obtained in this study were consistent with our two stated hypotheses. In addition, at the low elevation site, the rate of the growth in height of A. veitchii in canopy gaps was greater than that of A. mariesii, indicating that A. veitchii can dominate after disturbance at low elevations. The findings of this study indicate that the differential elevational distribution of the two Abies species can be attributed to interspecific differences in surplus production rates. We believe that these findings will be useful for predicting changes in the distribution of vegetation in response to climate change.

Combining lanthanum-modified bentonite (LMB) and submerged macrophytes alleviates water quality deterioration in the presence of omni-benthivorous fish

Bioturbation by omni-benthivorous fish often causes sediment resuspension and internal nutrient loading, which boosts phytoplankton growth and may lead to a shift of clear water lakes to a turbid state. Removal of large-sized omni-benthivorous individuals is a lake restoration measure that may revert lakes from a turbid to a clear water state, yet the rapid reproduction of small omni-benthivorous fish in tropical and subtropical shallow lakes may impede such lake recovery. In lake restoration, also a combination of lanthanum-modified bentonite (LMB) and planting submerged macrophytes has been used that may synergistically improve lake water quality. How the combined effect works in the presence of small omni-benthivorous fish has not been studied, which is needed given the high abundances of small omni-benthivorous fish in (sub)tropical lakes. We conducted a two-by-two factorial mesocosm experiment with and without the submerged macrophytes Vallisneria natans and with and without LMB, all in the presence of small crucian carp. At the end of the experiment, turbidity in the V. natans, LMB and combined LMB + V. natans treatments had decreased by 0.8%, 30.3% and 30.9%, respectively, compared with the controls. In addition, the nitrogen (N) and phosphorus (P) release from the sediment in the combined LMB + V. natans treatments had decreased substantially, by 97.4% and 94.3%, respectively, compared with the control. These N and P fluxes were also significantly lower in the combined LMB + V. natans treatments than in the sole LMB treatment (88.1% and 82.3%) or the V. natans treatment (93.2% and 90.3%). Cyanobacteria in the overlying water in the combined LMB + V. natans treatments significantly decreased by 84.1%, 63.5% and 37.0%, respectively, compared with the control and the sole LMB and V. natans treatments. Our results show that LMB and submerged macrophytes complement each other in effectively improving the water quality, even in the presence of small omni-benthivorous fish.