Reduced Species Richness Research Articles

The effects of livestock grazing on vegetation in a semiarid grassland: a test of three hypotheses

AbstractQuestionsLivestock grazing is an important driver of plant diversity in grasslands. Different mechanisms summarized in three main hypotheses have been proposed to explain its varying effects depending on productivity. The insufficient compensation hypothesis (ICH) states that livestock causes the extinction of species that cannot compensate for biomass removal in unproductive sites, reducing species richness. The competitive release hypothesis (CRH) states that livestock increases plant diversity by attenuating competition, especially in productive environments. In the convergent evolution hypothesis (CEH), livestock has minor effects on diversity in unproductive sites because plants that endure stress are pre‐adapted to grazing. These hypotheses have rarely been compared formally, and have mostly been tested on large spatial scales. Here we simultaneously test these hypotheses on a local scale.LocationNatural semi‐arid grassland, Oaxaca, Mexico.MethodsWe performed a long‐term exclosure experiment, recording plant diversity annually over 17 years. In 2017 we measured species richness over a grazing intensity gradient. We used linear mixed‐effects models, nestedness and beta‐diversity analyses to evaluate diversity and composition in relation to grazing and productivity.ResultsPlant diversity generally increased with grazing intensity. In line with CRH, species richness increased as grazing became more intensive due to a progressive incorporation of increasingly poor competitors to the community, with a seemingly stronger effect under high productivity. This suggests that herbivores limit competitive species and prevent competitive exclusion. ICH may play a secondary role because the effect was reversed in low productivity inside exclosures.ConclusionsOur finding implies that in productive sites, the exclusion of livestock can be detrimental to plant diversity as a lack of grazing accelerates competitive exclusion. By contrast, in limiting environments, grazing can preserve diversity if livestock are kept at low stocking densities. Our results show that small‐scale variations in productivity need to be considered when designing livestock management.

Short-Interval, Severe Wildfires Alter Saproxylic Beetle Diversity in Andean Araucaria Forests in Northwest Chilean Patagonia

The occurrence of short-interval, severe wildfires are increasing drastically at a global scale, and appear as a novel phenomenon in areas where fire historically returns in large time lapses. In forest ecosystems, these events induce drastic changes in population dynamics, which could dramatically impact species diversity. Here, we studied the effect on diversity of recent short-interval, severe wildfires (SISF), which occurred in rapid succession in the summers of 2002 and 2015 in Chilean Northern Patagonian Araucaria–Nothofagus forests. We analyzed the diversity of deadwood-dependent (i.e., saproxylic) and fire-sensitive beetles as biological indicators across four conditions: 2002-burned areas, 2015-burned areas, SISF areas (i.e., burned in 2002 and again in 2015), and unburned areas. Saproxylic beetles were collected using window traps in 2017 to 2019 summer seasons. To investigate the mechanisms underpinning the fire-related disturbance of the assemblage, we evaluated the effects of post-fire habitat quality (e.g., dead wood decomposition) and quantity (e.g., burned dead wood volume and tree density) on the abundances and species richness of the entire assemblage and also multiple trophic groups. Compared with the unburned condition, SISF drastically reduced species richness, evenness, and Shannon’s diversity and altered the composition of the saproxylic beetle assemblages. The between-condition variation in composition was accounted for by a species replacement (turnover) between SISF and 2015-burned areas, but both species replacement and extinction (nestedness) between SISF and unburned areas. Dead wood decomposition and tree density were the variables with the strongest effects on the abundance and species richness of the entire saproxylic beetle assemblage and most trophic groups. These results suggest that SISF, through degraded habitat quality (dead wood decomposition) and quantity (arboreal density), have detrimental impacts on diversity and population dynamics of saproxylic beetle assemblages. Therefore, habitat loss is a central mechanism underpinning fire-related biodiversity loss in these forest ecosystems.

Bird Communities in Coastal Areas. Effects of Anthropogenic Influences and Distance From the Coast

Urbanization effects have been studied all over the world, documenting impact in species richness, abundances and changes in species communities. Birds have been broadly used as study models. In general, urbanization affects birds, reducing species richness, especially in the urban core, and increasing species richness in areas with intermediate levels of disturbance, such as suburbs. Urbanization also changes species assemblages depending on urban characteristics and resources available, creating habitats for different species. Even when more than half of the cities in the world are on the coast, the effects of urbanization on habitat use of terrestrial and marine birds in coastal urban environments has received little attention. We hypothesized that coastal cities would present different bird diversity in modified marine areas and modified inland areas as terrestrial and marine ecosystems coexist. We predict that modified marine areas will have higher species richness than modified inland areas and natural marine areas. For bird assemblages, we expect to find similar species compositions between sites with similar habitat characteristics more than closeness. We compare habitat use of marine and terrestrial avifauna in the human-modified coastal city of Valparaiso, Chile, characterized by a range of urban developments within city boundaries. We specifically compare corrected bird abundance in six different possible habitats for birds, according to distance to the coast, and human influence. Bird counts (50 m fixed radius) were conducted in winter and spring of 2019. Bird species richness and abundances, corrected by the probability of detection, were estimated. Additionally, species composition and occupancy of bird species in those habitats were calculated. Results show that coastal urban cities can provide different habitats for bird species. Modified inland habitats differ from semi-natural inland habitats and from the modified beaches in species richness and species composition. Environmental heterogeneity in coastal cities seems to allow the coexistence of marine and terrestrial bird species, showing differences in species richness and bird assemblages for marine-inland environments and natural- modified habitats. Results highlight the need to consider these factors for urban planning in order to conserve bird diversity in coastal urban areas.

Native forest metacommunity structures in Uruguay shaped by novel land-use types in their surroundings.

We explore the effect of land‐use change from extensively used grasslands to intensified silvi‐ and agricultural monocultures on metacommunity structure of native forests in Uruguay. We integrated methods from metacommunity studies, remote sensing, and landscape ecology to explore how woody species distribution was influenced by land‐use change from local to regional scale. We recorded richness and composition of adult and juvenile woody species from 32 native forests, created land‐use maps from satellite image to calculate spatial metrics at landscape, class, and patch levels. We also analyzed the influence of land use pattern, climate, topography, and geographic distance between sites (d) on metacommunity, and created maps to visualize species richness and (dis)similarity between communities across the country. Woody species communities were distributed in a discrete pattern across Uruguay. Precipitation and temperature seasonality shaped species distribution pattern. Species richness and community dissimilarity increased from West to East. Latitude did not influence these patterns. Number of patches, landscape complexity, and interspersion and juxtaposition indexes determine woody species distribution at landscape level. Increasing areas covered by crops and timber plantation reduced species richness and increased community dissimilarity. The spatial metrics of native forest fragments at patch level did not influence metacommunity structure, species richness, and community dissimilarity. In conclusion, Uruguayan native forests display a high range of dissimilarity. Pressure of neighborhood land uses was the predominant factor for species assemblages. Conserving landscape structures that assure connectivity within and among native forest patches is crucial. On sites with rare target species, the creation of alliances between governmental institution and landowner complemented by incentives for biodiversity conservation provides opportunities to advance in species protection focused on those less tolerant to land‐use change.

Assessing long-term nutrient and lime enrichment effects on a subtropical South African grassland

Nutrient enrichment influences grassland ecosystem structure, typically manifested by reduced species richness and increased productivity. Quantifying the long-term impacts of nutrient enrichment on grasslands contributes to understanding eutrophication effects on grassland, particularly for grasslands adapted to low soil nutrient status. Overextended time periods, nutrient enrichment may modify soil fertility. The Ukulinga Grassland Nutrient Experiment situated on a natural C4 grassland was set up in 1951 on the Ukulinga research farm, South Africa. Continuously applied treatments on plots measuring 2.7 × 9 m include combinations of nitrogen at 0, 7, 14 and 21 g m−2 per annum, phosphorus at 0 and 2.8 g m−2 per annum and lime at 0 and 225 g m−2 applied every five years. Nitrogen sources included ammonium sulphate (acidifying) and limestone ammonium nitrate (less acidifying). Grass species composition was influenced by both nitrogen forms. In contrast, forb species composition was more sensitive to LAN. We found evidence of nitrogen limitation on aboveground net-primary production. However, species richness (for grass and forbs) declined with increasing ammonium sulphate levels, owing to increased soil acidity and high aluminium concentrations. Aluminium toxicity can affect overall species composition by replacing Al-sensitive species with Al-tolerant species on site.

The effects of soil solarization and application of a Trichoderma biocontrol agent on soil fungal and prokaryotic communities

AbstractSoil solarization and biological control are two management strategies that have been used globally to manage soil‐borne plant pathogens. However, the broader effects of these strategies on soil microbial communities have not been well described. Soil prokaryotic and fungal communities were investigated by environmental DNA amplicon sequencing as part of field trials conducted in San Rafael, CA, and in Corvallis, OR. We examined microbial community changes following soil solarization, amendment with the biocontrol agent Trichoderma asperellum (TA), or solarization followed by application of the biocontrol agent. Soil solarization caused significant changes to prokaryotic and fungal communities by reducing species richness and diversity. Soil water potential was determined to be a significant factor affecting the prokaryotic community. Application of TA to solarized or nonsolarized soil did not significantly alter the microbial communities. However, solarization resulted in diminished microbial densities that appeared to enhance subsequent establishment of the biocontrol agent. This study revealed how specific environmental variables of heat intensity and soil moisture contribute to changes in the abundance of individual taxa and taxonomic groups.

Recently introduced Wolbachia reduces bacterial species richness and reshapes bacterial community structure in Nilaparvata lugens.

Wolbachia has been developed as an effective tool to suppress insect pests and arbovirus transmission. Recently, the brown planthopper Nilaparvata lugens, a serious agricultural pest, has been successfully transinfected with Wolbachia wStri strain from Laodelphax striatellus. However, before conducting the field experiments, the impacts of wStri on the bacterial microbiota in N. lugens and how it differs from native Wolbachia wLug strain have not been clarified. Here, we found that wStri reduced bacterial diversity and shaped bacterial community structure more than wLug in both developmental stage and different adult tissues. Overall, the relative abundance of Wolbachia was negatively correlated with bacterial diversity, but the bacterial diversity gradually decreased only when the relative abundance of Wolbachia was higher than 60%. Further analysis found that wStri reduced species richness of other bacteria but not their evenness. wStri infection also affected many bacterial functions (e.g., amino acid metabolism & signaling and cellular processes) in the developmental stages, with a stronger effect than wLug in nymphs. Moreover, although Wolbachia occupied a high relative abundance in infected individuals, Acinetobacter was consistently a core part of microbiome. These results showed the significant impacts of recently introduced wStri on bacterial microbiota in N. lugens, with the effects differing from native wLug. This study will aid in understanding the relationship between Wolbachia, its host and the host's microbiota, and provide a reference for future field experiments.

The Effect of Salmon Food-Derived DOM and Glacial Melting on Activity and Diversity of Free-Living Bacterioplankton in Chilean Patagonian Fjords.

Fjord ecosystems cycle and export significant amounts of carbon and appear to be extremely sensitive to climate change and anthropogenic perturbations. To identify patterns of microbial responses to ongoing natural and human-derived changes in the fjords of Chilean Patagonia, we examined the effect of organic enrichment associated with salmon aquaculture and freshening produced by glacial melting on bacterial production (BP), extracellular enzymatic activity (EEA), and community diversity of free-living bacterioplankton. We assayed the effects of salmon food-derived dissolved organic matter (SF-DOM) and meltwaters through microcosm experiments containing waters from Puyuhuapi Fjord and the proglacial fjords of the Southern Patagonia Icefield, respectively. Rates of BP and EEA were 2 times higher in the presence of SF-DOM than in controls, whereas the addition of autochthonous organic matter derived from diatoms (D-DOM) resulted in rates of BP and EEA similar to those measured in the controls. The addition of SF-DOM also reduced species richness and abundance of a significant fraction of the representative taxa of bacterioplankton of Puyuhuapi Fjord. In the proglacial fjords, bacterioplankton diversity was reduced in areas more heavily influenced by meltwaters and was accompanied by moderate positive changes in BP and EEA. Our findings strongly suggest that SF-DOM is highly reactive, promoting enhanced rates of microbial activity while could be influencing the diversity of bacterioplankton communities in Patagonian fjords with a strong salmon farming activity. These findings challenge the traditional view of phytoplankton production as the primary source of labile DOM that fuels heterotrophic activity in coastal ecosystems impacted by anthropogenic organic enrichment. Given the intensive local production of salmon, we analyze the significance of this emerging source of rich “allochthonous” organic substrates for autotrophic/heterotrophic balance, carbon exportation, and hypoxia in Patagonian fjords. The effect of human DOM enrichment can be enhanced in proglacial fjords, where progressive glacial melting exerts additional selective pressure on bacterioplankton diversity.

Zooplankton variability and possible oceanographic anomalies from 1996 to 2009 on the south coast of Brazil.

The analysis of 14 years of sampling data on the zooplankton community in southern Brazil showed a tendency toward increased density and reduced species richness. This behavior could be a response to a prolonged period of negative sea surface temperature (SST) anomalies in the Pacific Ocean and the ENSO phenomenon. The persistence of the La Niña phenomenon between 2001 and 2008 was associated with a higher incidence of stress from southwest winds and a greater reach of the front of the La Plata River plume, with possible responses being lower temperatures in the summer/autumn and lower salinities in the winter/spring in the study area. Under these conditions, one response in the zooplankton community was larger copepod domains. This group was responsible for specific changes in the community, with an increase in the population of Acartia tonsa while populations of species with more thermophilic characteristics showed a decrease. It cannot be disregarded, however, that possible interactions between different abiotic and biotic forces acting in the environment may have influenced the structure of the community. It remains unknown whether a new steady state has been established in the environment or whether there has been a return to initial conditions.

Noise pollution effect on composition of avian structure in different urban gradients

Extreme urbanization producing high noise level reduces species richness across different taxa. The present study is an effort to document the noise level of two urban educational campuses of Bhubaneswar and its effect on avifaunal composition. Point count sampling method was found to be most suitable. Around 49 species of birds including 6 migratory belonging to 9 orders and 28 families were recorded. Campus 1 was recorded higher noise level than campus 2. The higher bird species richness and abundance in Campus 2 predicts that the urban environment with green space provides a better habitat for birds due to more structured vegetation cover as well as less noise level. Noise level found to be negatively correlated with bird richness and abundance, which explaining, higher the noise level, lower the bird richness. This knowledge can help the city planners to select suitable place for making green spaces and sustainable habitat for the birds.

Logging effects on parasitic infections in a swamp rat (Malacomys edwardsi) in West Africa

AbstractHabitat disturbance can have negative impacts on biodiversity, such as reducing species richness. The effects of habitat disturbances on parasite infections of host species, potentially altering their survival rate and thus abundance, are less well known. We examined the influence of forest logging in combination with seasonality, host abundance, host body condition, and host sex, on the community composition of gastrointestinal parasites infecting Edward’s swamp rat, Malacomys edwardsi. Community composition of parasites did not differ between logged and undisturbed sites, but the abundance of some nematodes (i.e., Ascaris and hookworm) was higher in undisturbed than logged sites. The higher abundance of these nematode species implies a changed host-parasite relationship, thus potentially influencing host persistence.

The impact of Scn1a deficiency and ketogenic diet on the intestinal microbiome: A study in a genetic Dravet mouse model

PurposeThe gut-brain axis has been discussed as a possible factor contributing to ictogenesis and epilepsy. While recent preclinical studies have proposed a link between the antiseizure effect of a ketogenic diet (KD) and alterations to the gut microbiota, there is a knowledge gap about microbial composition as a result of Scn1a genetic deficiency and how this is affected by KD in Dravet syndrome. MethodsA large-scale microbiome analysis using 16S rRNA gene sequencing was performed in fecal samples collected from wildtype and Dravet mice fed either control diet (CD) or KD. Microbial alterations associated with the Dravet phenotype or triggered by KD exposure were identified. ResultsThe comprehensive microbial analysis revealed pronounced alterations in gut microbiota between wildtype and Dravet mice. The regulation of Chao index indicated a reduced species richness in Dravet mice when compared to wildtype controls. The ratio between Firmicutes and Bacteroidetes phyla was increased in mice with the Dravet genotype, therefore implying a microbial dysbiosis in these animals. Following the switch to CD or KD, several bacteria phyla and genera were regulated in Dravet mice. Interestingly, an increased abundance of the Clostridium genus and a decreased abundance of the Romboutsia genus showed a significant correlation with the severity of the phenotype in Dravet mice. KD increased the abundance of Firmicutes and reduced the abundance of Bacteroidetes phyla in Dravet mice. The degree of these microbial alterations correlated with the reduction in the frequency and duration of motor seizures in these animals. ConclusionIn conclusion, the comprehensive microbial analysis demonstrated pronounced alterations in the gut microbiota with evidence of a gut dysbiosis as a consequence of the Scn1a genetic deficiency. Exposure to KD affected the gut microbiome in Dravet mice. Interestingly, abundance of selected genera correlated with the seizure phenotype of Dravet mice. Future studies investigating the functional relevance of disease-associated and KD-triggered changes would be essential to confirm the relevance of these findings.

Antigonon leptopus invasion is associated with plant community disassembly in a Caribbean island ecosystem

Invasions by non-native plant species are widely recognized as a major driver of biodiversity loss. Globally, (sub-)tropical islands form important components of biodiversity hotspots, while being particularly susceptible to invasions by plants in general and vines in particular. We studied the impact of the invasive vine A. leptopus on the diversity and structure of recipient plant communities on the northern Caribbean island St. Eustatius. We used a paired-plot design to study differences in species richness, evenness and community structure under A. leptopus-invaded and uninvaded conditions. Community structure was studied through species co-occurrence patterns. We found that in plots invaded by A. leptopus, species richness was 40–50% lower, and these plots also exhibited lower evenness. The magnitude of these negative impacts increased with increasing cover of A. leptopus. Invaded plots also showed higher degrees of homogeneity in species composition. Species co-occurrence patterns indicated that plant communities in uninvaded plots were characterized by segregation, whereas recipient plant communities in invaded plots exhibited random co-occurrence patterns. These observations suggest that invasion of A. leptopus is not only associated with reduced species richness and evenness of recipient communities in invaded sites, but also with a community disassembly process that may reduce diversity between sites. Given that A. leptopus is a successful invader of (sub-)tropical islands around the globe, these impacts on plant community structure highlight that this invasive species could be a particular conservation concern for these systems.

Mowing and warming effects on grassland species richness and harvested biomass: meta-analyses

Climate and management affect grassland plant diversity but studies vary regarding the magnitude of changes in plant species richness. Here we develop a comprehensive understanding of species richness modification due to management (mowing) and climate (warming) variations worldwide, and present the results of two meta-analyses from 999 and 1793 records (articles). Recorded articles had at least one experiment with a case-control design. The results show that both mowing (43 articles) and warming (34 articles) modify species richness, which on average increased by c. 32% with once-a-year mowing (against no mowing) and declined by c. 13% with warming (against ambient temperature). Our meta-analysis on the mowing regime supports the humped-back model, with one or two cuts per year being the level of disturbance optimising species richness. We also observed that warming-induced reduction in species richness is lower in dry climates (< 300 mm yr-1) and at low elevations (< 1000 m a.s.l.). Where available, we accounted for harvested biomass as a concomitant variable and we found that overall it decreased by c. 21% (mowing) and increased by c. 11% (warming). The evidence provided of an opposite response of species richness and harvested biomass to disturbance is consistent with the competitive-exclusion hypothesis of negatively correlated patterns between the two outcomes (high taxonomic diversity with low biomass production, and vice versa). The reported difficulties in finding representative studies in previous meta-analyses and in the present ones highlight the need to orient future research towards long-term experiments on the combined effects of mowing and warming for a more robust inference of environmental and management constraints on grassland performance.

Deltaic floodplain wetland vegetation dynamics along the sediment surface elevation gradient and in response to disturbance from river flooding and hurricanes in Wax Lake Delta, Louisiana, USA

Herbaceous wetland vegetation species percent cover data collected over five growing seasons (2007–2011) was used to define unique species assemblages along the elevation gradient of deltaic islands in the actively prograding deltaic floodplain wetlands in the Wax Lake Delta, a major distributary of the Mississippi River. The passage of Hurricanes Gustav and Ike in September 2008 as well as a major river flood in spring of 2011 provided an opportunity to quantify the response and recovery of the vegetation community following disturbances of varying intensities. Two significant persistent species assemblages were observed from 2007 through 2011. The higher elevation species assemblage occurred above mean low water (MLW; –0.04 m NAVD88). While the lower elevation species assemblage occurred at elevations ranging from –0.47 to 0.30 m NAVD88. These unique lower and higher elevation species assemblages overlap at intertidal elevations. Hurricanes Gustav and Ike drastically reduced aboveground vegetation and percent cover immediately following the storms particularly for lower elevation species. No aboveground cover was observed for Sagittaria latifolia, Nelumbo lutea, Potamogeton nodosus, or Submerged Aquatic Vegetation (SAV) in any of the sampling stations following the hurricanes, compared to pre-hurricane aboveground cover mean ranging from 2 to 5%. Sagittaria platyphylla aboveground cover decreased from a pre-hurricane mean of 12.5% to <1% following the hurricanes. In subsequent years the community composition for all species returned to pre-disturbance cover, with the significant species assemblages returning within two years. In 2011 the major river flood resulted in disturbance that reduced species richness within both assemblages, likely related to differences in flood tolerance of vegetation species, with Nelumbo lutea cover expanding from a mean of 10% cover in the year prior to the flood to 22.5% following the flood. Vegetation community composition was shown to be robust to major river floods and hurricane storm surge passage.

Changes in community functional structure and ecosystem properties along an invasion gradient of Ligustrum lucidum

AbstractQuestionsIt is well documented that invasive alien plants can reduce species richness and diversity and modify the composition of invaded communities. However, our knowledge on the impacts of invasive alien plants on the community functional structure and ecosystem properties and the mechanisms underlying these changes is more limited. We evaluated how the community functional structure and ecosystem properties change along a gradient of Ligustrum lucidum abundance.LocationSubtropical mountain forest in NW Argentina.MethodsWe conducted tree vegetation sampling in 164 plots distributed along a gradient of L. lucidum abundance. For L. lucidum and for the most abundant tree species in these plots we estimated six functional traits (specific leaf area, leaf tensile strength, leaf nitrogen concentration, leaf water potential, wood density and maximum plant height), as well as their relative growth rates. Then, we calculated indices of community functional structure (community‐weighted means for each trait; richness, evenness, divergence and dispersion). We explored the extent to which the invasive success of L. lucidum and its impact may be attributed to niche differentiation or to fitness superiority. Finally, we explored how L. lucidum abundance alters ecosystem properties.ResultsSome indicators of community functional structure changed linearly while others tended to saturate along the invasion gradient. L. lucidum has a higher growth rate than resident species and it lays close to the periphery, but within the limits of the functional space defined by resident trees. L. lucidum tends to displace more functionally similar resident species. Soil moisture and N content declined, while soil C:N increased with L. lucidum abundance.ConclusionsOur findings suggest that both niche differentiation and fitness superiority contribute to explain the invasion success of L. lucidum and the changes in functional structure of the community along the gradient of L. lucidum abundance with evident impacts on ecosystem properties.

Fungal diversity in selected coastal mangrove ecosystems in East Berbice Corentyne, Guyana, South America

There is limited data on the fungal diversity in mangrove ecosystems in Guyana. This study investigated fungal diversity during the dry season in three selected coastal mangrove ecosystems along the Corentyne Coast of East Berbice, Guyana. Sampling was conducted within randomly established 50 m x 50 m plots containing 20 mini transects of length 12.5 m x 10 m in the overwash mangrove ecosystem at each of six study sites within the three study locations. Samples retrieved from the study plots included leaf, bark, soil and fruiting bodies. These were placed into separate bags and labelled appropriately. Environmental parameters were recorded at each study plot. Fruiting bodies were used to identify macrofungal species, and the leaf, bark and soil were used to prepare cultures from which microfungal samples were identified. The species that were identified were used to compile a checklist of fungal species, and diversity indices were calculated. A total of thirty (30) species were recorded, nine (9) of which were microfungi identified from the cultured samples and twenty-one (21) species were identified from macrofungal fruiting bodies retrieved at the study sites. The results further revealed that an increase in pH and salinity and a decrease in temperature resulted in an increase in species richness. Tidal activity also appeared to reduce species richness. Aspergillus, Rhizopus and Trichoderma were the dominant species at the three study sites with high relative species abundance. There also appeared to be some instances of substrate specificity.

Biotic homogenization increases with human intervention: implications for mangrove wetland restoration

The large‐scale conversion of natural mangroves to aquaculture reduces species richness and diversity. Large areas of abandoned aquaculture ponds in areas where mangroves formerly predominated in China and southeast Asia represent important potential effective targets for mangrove restoration. Here, we empirically assessed the α‐diversity (species richness) and β‐diversity (variation in community composition) of mangrove, macrobenthos, fish and waterbird in a tropical mangrove bay on Hainan Island, China. We compared sites subjected to different pond‐to‐mangrove restoration programs more than 20 years ago (passive restoration without planting and active restoration with planting) to nearby reference site with natural mangrove forests and mudflats. To better understand how β‐diversity responds to restoration, we also distinguished between β‐diversity turnover and nestedness (richness difference). In general, α‐diversity values for both fish and waterbird communities and β‐diversity values for the mangrove, macrobenthos and waterbird communities were lower at the restoration sites than at the reference site, suggesting that the strong homogenizing effects of anthropogenic habitat alternation were still apparent after more than 20 years since aquaculture ceased. In addition, spatial turnover, not nestedness, dominated total β‐diversity both across the whole study area and at individual sites, suggesting that multiple processes, such as environmental filtering, helped to shape multi‐taxa community structures. Moreover, we found no evidence that planting in the abandoned ponds, in addition to standard hydrological restoration, supported greater species diversity of taxa like macrobenthos and waterbird than the naturally regenerated site after more than 20 years' recovery. Our results underline the importance of avoiding the conversion of natural mangrove stands to aquaculture wherever possible and the urgent need to design effective mangrove restoration techniques in tropical Asia.

Reconciling biodiversity with timber production and revenue via an intensive forest management experiment.

Understanding how land-management intensification shapes the relationships between biodiversity, yield, and economic benefit is critical for managing natural resources. Yet, manipulative experiments that test how herbicides affect these relationships are scarce, particularly in forest ecosystems where considerable time lags exist between harvest revenue and initial investments. We assessed these relationships by combining 7 yr of biodiversity surveys (>800 taxa) and forecasts of timber yield and economic return from a replicated, large-scale experiment that manipulated herbicide application intensity in operational timber plantations. Herbicides reduced species richness across trophic groups (-18%), but responses by higher-level trophic groups were more variable (0-38% reduction) than plant responses (-40%). Financial discounting, a conventional economic method to standardize past and future cash flows, strongly modified biodiversity-revenue relationships caused by management intensity. Despite a projected 28% timber yield gain with herbicides, biodiversity-revenue trade-offs were muted when opportunity costs were high (i.e., economic discount rates ≥7%). Although herbicides can drive biodiversity-yield trade-offs, under certain conditions, financial discounting provides opportunities to reconcile biodiversity conservation with revenue.

Birds diversity and faunogenetic structure of avifauna in forests parks of two megalopolises (Ukraine)

Background. In the 21st century, landscape transformation processes are underway in large cities, which affects the stability of wildlife habitats. Habitat transformations often reduce species richness due to a decrease in the population sizes of some species, and therefore, small in number and rare species are eliminated from bird communities. Rare species can have unique consortive relationships, which makes them particularly important for the long-term ecosystem functioning. A study of the avifauna of forest parks makes it possible to develop an algorithm for the coexistence of human and birds. Methods. The number and distribution of birds were determined by route counting. The total length of the fixed route was 5.7 km in Kyiv and 3.5 km in Kharkiv. On each route, observations were carried out annually with three repetitions during the nesting period when the birds are most attached to their habitats (end of April–May–June). The average data for the total study period (2013–2017) were calculated for each city. For the average number, the standard deviation was calculated. An analysis of the faunogenetic structure of avifauna was carried out according to the method developed by V.P. Belik. A faunogenetic complex is a group of animal species associated by a common origin with ecosystems of a certain landscape-geographical zone. We also classified bird species into ecological groups according to the patterns of microhabitat choice. To compare the α-diversity of bird in the forest-park zones of cities, a number of commonly accepted indices that express the correlation between the number and density of species were calculated: 1) Berger–Parker dominance index: DBP = Nimax / N; 2) Shannon diversity index: H´ = -∑(Pi × LnPi); 3) Pielou evenness index: E = H´ / LnS; where: Nі– the number of each species; Nimax – the maximum value of Nі; N = ∑Ni – the total number of all species (pairs/km); Pi = Ni / N – the ratio of each species; S – total number of the species. Results. The study presents a comparative analysis of diversity and faunogenetic structure of avifauna in the forest park zones of Kyiv and Kharkiv, inhabited by 71 breeding species of birds that belong to 10 orders. In the eastern region, the proportion of birds of the boreal and the European forest-steppe complex decreases, but the share of the desert-mountain complex increases. The fauna of the European nemoral complex dominates (32.8 % in Kyiv and 40.4 % in Kharkiv). The basis of the communities are dendrophils: 83.6 % (n = 67) in Kyiv and 82.7 % (n = 52) in Kharkiv. The dominant species in all forest parks are the great tit (Parus major) and chaffinch (Fringilla coelebs). Conclusions. The differences in the faunogenetic structure of bird communities are due to the proximity of model forest parks on the territory of Kyiv to the forest natural geographical zone, and on the territory of Kharkiv to the steppe, which leads in the eastern region to a decrease in the proportion of birds of the boreal and the European forest-steppe complex while the proportion of desert-mountain complex increases. Dendrophils predominate significantly, and the share of sclerophils and limnophils in total is less than 20 % of the bird community in the forest parks of each city. As a consequence of the fragmentation of the Kiev forest park zone, the diversity of nesting birds communities in the forest-park zone of Kyiv is slightly lower than of Kharkiv, and the pressure of the dominant species is more significant.