Species Diversity Of Communities Research Articles

Community composition drives siderophore dynamics in multispecies bacterial communities

BackgroundIntraspecific public goods are commonly shared within microbial populations, where the benefits of public goods are largely limited to closely related conspecifics. One example is the production of iron-scavenging siderophores that deliver iron to cells via specific cell envelope receptor and transport systems. Intraspecific social exploitation of siderophore producers is common, since non-producers avoid the costs of production but retain the cell envelope machinery for siderophore uptake. However, little is known about how interactions between species (i.e., interspecific interactions) can shape intraspecific public goods exploitation. Here, we predicted that strong competition for iron between species in diverse communities will increase costs of siderophore cooperation, and hence drive intraspecific exploitation. We examined how increasing microbial community species diversity shapes intraspecific social dynamics by monitoring the growth of siderophore producers and non-producers of the plant-growth promoting bacterium Pseudomonas fluorescens, embedded within tree-hole microbial communities ranging from 2 to 15 species.ResultsWe find, contrary to our prediction, that siderophore production is favoured at higher levels of community species richness, driven by increased likelihood of encountering key species that reduce the growth of siderophore non-producing (but not producing) strains of P. fluorescens.ConclusionsOur results suggest that maintaining a diverse soil microbiota could partly contribute to the maintenance of siderophore production in natural communities.

Assessment of reptile response to habitat degradation in arid and semi-arid regions

Reptiles are essential components of global biodiversity and dynamic ecosystems due to their ecological roles and functions. However, they face significant vulnerability to anthropogenic disturbances and habitat degradation, resulting in their classification as the third most threatened vertebrate group globally. The current study examines reptile response to anthropogenic habitat degradation in the highly biodiverse Souss-Massa National Park (SMNP), located on the North African Atlantic coast. During 2021 and 2022, linear transects were established within four habitat categories experiencing varying degrees of vegetation cover degradation (undegraded, slightly degraded, moderately degraded, and highly degraded), caused by livestock overgrazing and vegetation clearance. Based on the comparisons of the Normalized Difference Vegetation Index means, the vegetation cover differed significantly among the selected habitat categories, with a noticeable reduction in the natural vegetation cover as the level of habitat degradation increased. The visual encounter survey technique was used to search a total of 96 transects, with each of the studied habitat categories being represented by 24 transects. Species richness, diversity, abundance, composition and similarities of reptile communities were determined and compared between habitat categories. During the study period, 11 species (438 individuals) were encountered, accounting for 48 % of SMNP reptile fauna. Species richness, diversity and abundance differed significantly among habitat categories, with the lowest means recorded in the highly degraded areas. Reptiles responded differently to habitat degradation based on their taxonomic levels, thus indicating a species-specific impact of degradation. Species composition varied considerably among habitat categories, with highly degraded areas displaying significant differences and the lowest degree of similarity when compared to all other categories (p = 0.0006). Anthropogenic alterations in reptile abundance distribution and species occurrence likely account for the observed differences in species composition within the different habitat categories. The reported reptile responses to habitat degradation might be attributed to factors associated with natural vegetation, such as food availability, microhabitat preferences, or interactions with other species. Exploring these factors in future research could provide further insights into the mechanisms driving reptile community responses to habitat degradation. Such data can provide valuable information for implementing effective conservation measures to prevent anthropogenic habitat degradation and protect threatened species in arid and semi-arid areas.

Loss of native herbivores triggers diversity decline of ephemeral plant communities

AbstractAimEvaluate the temporal changes in species diversity, composition, and structure of ephemeral plant communities and the seed bank in response to long‐term herbivore exclusion over 11 years in plots with and without herbivores.LocationNorth‐central Chile.MethodsWe obtained information on ephemeral vegetation cover in August and September using the intercept point method and recorded seed abundance in April. The Bosque Fray Jorge National Park Long‐Term Socio‐Ecological Research (LTSER) provided these records covering 11 years (2009–2019). From the original experiment of 20 plots, we used eight plots divided into two treatments: four plots allowed free access to all herbivores (with herbivores), while the other four plots excluded herbivores (without herbivores).ResultsWe found that Hill–Shannon diversity increased in plant communities with herbivores and a temporal increase in the cover of the dominant species, Plantago hispidula, under herbivore exclusion. In wet years, species richness and temporal turnover of plant communities increased independently of treatment. Although seed abundance differed among treatments and years, population structure remained constant over time and among treatments, suggesting that the seed bank acts as a buffer against shocks that modify plant community dynamics. Structural equation modeling revealed that precipitation, via its positive effects on Plantago hispidula, increases native plant richness to a greater extent than herbivores. However, in the absence of herbivores, precipitation directly affects native species richness. Moreover, we found that precipitation also influences the native species richness of the seed bank, both directly and indirectly, although its impacts exhibit a time lag.ConclusionsOur study demonstrates that the temporal dynamics of ephemeral plant communities and seed banks in semi‐arid ecosystems are strongly coupled to climate variability, highlighting the vulnerability of these communities to biodiversity loss and climate change.

Plant diversity and ecosystem multifunctionality of different degraded grasslands in alpine meadows of Maqu

AbstractThe relationship between biodiversity and ecosystem multifunctionality (EMF) is critical to understanding the dynamics of ecosystem services. Several studies have investigated alterations in multiple ecosystem functions under grassland degradation and its relationship with taxonomic diversity. However, how multidimensional biodiversity (taxonomic, functional, and phylogenetic diversity) and abiotic factors mediate EMF in degraded alpine meadows has yet to be well been explored. In this study, alpine meadows with different degrees of degradation were investigated in Maqu County, Gansu Province, China. The average and multi‐threshold methods were used to quantify EMF, while structural equation modeling (SEM) was used for statistical analysis. The results show that: (1) Degradation of alpine meadows has altered the species composition and diversity of plant communities. (2) Taxonomic, functional, and phylogenetic diversity were all significantly and positively correlated with EMF, and species richness, functional richness and Faith's PD effectively drive EMF within thresholds of 22%–75%, 20%–86% and 42%–72%, with maximum effects of 0.29, 0.33 and 0.12, respectively. (3) Degradation of alpine meadows directly and significantly reduced EMF, and mediated indirectly through plant diversity and soil abiotic factors. The multifunctionality index for different degrees of degradation showed non‐degraded (60.89) > light degraded (37.84) > moderate degraded (−14.17) > heavy degraded (−48.55). The results of this study reveal the relative importance of multidimensional plant diversity in predicting EMF of degraded alpine meadows, and potential mechanisms by which plant diversity and abiotic factors mediate the effects of alpine meadow degradation on EMF.

Microbial diversity and potential health risks of household municipal solid waste in China: A case study in winter during outbreak of COVID-19

Microbial (bacteria and fungi) community structures and their distributions in urban household municipal solid waste (HMSW) were characterized in a sampling campaign in 38 cities of China covering 5 climatic zones. All samples were collected from garbage containers in residential communities during the Winter of 2022, from January 11 to 26. A total of 247 bacterial genera belonging to 22 phyla were identified among the samples. Firmicutes (44.3 %), Bacteroidetes (33.77 %) and Proteobacteria (21.54 %) were the top 3 dominant phyla, and Arcicella (33.11 %) and Leuconostoc (21.87 %) were the dominant genera. Meanwhile, 124 fungal genera from 7 fungal phyla were detected. Ascomycota was the most dominant phylum, with an average relative abundance of 77.31 %. Hanseniaspora (24.03 %), Debaryomyces (13.47 %), Candida (12.18) were the top 3 dominant fungal genera. Alpha-diversity analysis showed that the species richness and diversity of bacterial and fungal communities of HMSW samples belonging to different climatic zones did not differ significantly. Nonmetric multidimensional scaling (NMDS) analysis confirmed that climatic had an effect on microbial communities but did not show a significant correlation. In addition, the distribution of microbial community in different samples from the same climate zone varied considerably, suggesting the HMSW source play important role in shaping microbial community composition. Considering that residential HMSW is relatively fresh, we speculates that the original microorganisms residing in different components of HMSW are key influencing factor for the community, while the reshaping force driven by environmental conditions are relatively weak. In addition, the study identified 13 bacterial and 16 fungal pathogens with Pseudomonas putida (0.25 %) and Sclerotinia sclerotiorum (2.12 %) as the most abundant potential pathogenic bacteria and fungi, respectively. These findings provide valuable information for characterizing microbial features and potential risks of HMSW in its management system.

DNA metabarcoding reveals spatial and temporal variation of fish eye fluke communities in lake ecosystems

Eye flukes (Diplostomidae) are diverse and abundant trematode parasites that form multi-species communities in fish with negative effects on host fitness and survival. However, the environmental factors and host-related characteristics that determine species diversity, composition, and coexistence in such communities remain poorly understood. Here, we developed a cost-effective cox1 region-specific DNA metabarcoding approach to characterize parasitic diplostomid communities in two common fish species (Eurasian perch and common roach) collected from seven temperate lakes in Estonia. We found considerable inter- and intra-lake, as well as inter-host species, variation in diplostomid communities. Sympatric host species characterization revealed that parasite communities were typically more diverse in roach than perch. Additionally, we detected five positive and two negative diplostomid species associations in roach, whereas only a single negative association was observed in perch. These results indicate that diplostomid communities in temperate lakes are complex and dynamic systems exhibiting both spatial and temporal heterogeneity. They are influenced by various environmental factors and by host-parasite and inter-parasite interactions. We expect that the described methodology facilitates ecological and biodiversity research of diplostomid parasites. It is also adaptable to other parasite groups where it could serve to improve current understanding of diversity, distribution, and interspecies interactions of other understudied taxa.

Sympatric primate seed dispersers and predators jointly contribute to plant diversity in a subtropical forest.

Mutualistic and antagonistic plant-animal interactions differentially contribute to the maintenance of species diversity in ecological communities. Although both seed dispersal and predation by fruit-eating animals are recognized as important drivers of plant population dynamics, the mechanisms underlying how seed dispersers and predators jointly affect plant diversity remain largely unexplored. Based on mediating roles of seed size and species abundance, we investigated the effects of seed dispersal and predation by two sympatric primates (Nomascus concolor and Trachypithecus crepusculus) on local plant recruitment in a subtropical forest of China. Over a 26month period, we confirmed that these primates were functionally distinct: gibbons were legitimate seed dispersers who dispersed seeds of 44 plant species, while langurs were primarily seed predators who destroyed seeds of 48 plant species. Gibbons dispersed medium-seeded species more effectively than small- and large-seeded species, and dispersed more seeds of rare species than common and dominant species. Langurs showed a similar predation rate across different sizes of seeds, but destroyed a large number of seeds from common species. Due to gut passage effects, gibbons significantly shortened the duration of seed germination for 58% of the dispersed species; however, for 54% of species, seed germination rates were reduced significantly. Our study underlined the contrasting contributions of two primate species to local plant recruitment processes. By dispersing rare species and destroying the seeds of common species, both primates might jointly maintain plant species diversity. To maintain healthy ecosystems, the conservation of mammals that play critical functional roles needs to receive further attention.

Community structure and species diversity dynamics of a subtropical evergreen broad-leaved forest in China: 2005 to 2020

Here, we characterize the temporal and spatial dynamics of forest community structure and species diversity in a subtropical evergreen broad-leaved forest in China. We found that community structure in this forest changed over a 15-year period. Specifically, renewal and death of common species was large, with the renewal of individuals mainly concentrated within a few populations, especially those of Aidia canthioides and Cryptocarya concinna. The numbers of individual deaths for common species were concentrated in the small and mid-diameter level. The spatial distribution of community species diversity fluctuated in each monitoring period, showing a more dispersed diversity after the 15-year study period, and the coefficient of variation on quadrats increased. In 2010, the death and renewal of the community and the spatial variation of species diversity were different compared to other survey years. Extreme weather may have affected species regeneration and community stability in our subtropical monsoon evergreen broad-leaved forests. Our findings suggest that strengthening the monitoring and management of the forest community will help better understand the long- and short-term causes of dynamic fluctuations of community structure and species diversity, and reveal the factors that drive changes in community structure.

Effects of Changing Restoration Years on Soil Nutrient Traits and Plant Community Diversity in a Phosphate Mining Area

The thinning vegetation and soil erosion problems left behind by extractive mining have caused serious environmental pollution, and vegetation restoration is one of the effective strategies to counter them. To study the effects of vegetation restoration on plant community species diversity, soil carbon, nitrogen and phosphorus, and the response of their plant community succession, four communities of different ages (1, 7, 10, 40) and one natural forest (>50 years) in the Kunyang phosphate mine were selected, and the analysis was carried out using the methods and protocols for plant community inventory. The species composition was recorded, and soil was collected from 0–60 cm in each community to determine the response of soil nutrients and plant diversity to the restoration process. The results show that the species richness of the community increases with the restoration year, the species composition at 40 years of restoration is similar to that of the natural forest, and the Shannon–Wiener diversity index in the tree layer at 40 years of restoration is greater than in the natural forest. Soil pH showed a decreasing trend with restoration year, and TP and AP increased with increasing time series. And the linear stepwise regression analysis showed that soil pH, soil organic carbon (SOC), total phosphorous (TP), available phosphorous (AP), and restoration year were the main factors of plant diversity. Compared to restoration of 10 years, TP and AP at the restoration of 40 years increased to 11.9–20.0 g∙kg−1 and 33.4–75.5 mg∙kg−1. The SOC of the community reached a maximum at 40 years of restoration, 1.5, 2.8, and 2.4 times higher at 0–20 cm, 20–40, and 40–60 cm, respectively, than at 1 year. The organic carbon fraction increased with the restoration year in an ‘N’ pattern, and mineral-associated organic carbon (MOC) and unstable organic carbon fraction decreased at 10 years and 40 years of restoration. The SOC of natural forests decreased, but stable organic carbon increased. The soil pH, SOC, and organic carbon fraction of the communities decreased with increasing soil depth, while TP and AP increased with increasing soil depth at the later period of restoration. In general, with extended restoration years, 40 years plant of restoration in phosphate mines can be expected to allow for plant community succession to climax community, and the key influence on plant diversity are the phosphorus and stable carbon fractions. These results are expected to facilitate the future basis for vegetation succession and restore systems during mining area restoration.

Reclaimed saline‐alkali paddy field may be a hotspot of methane and ammonia emissions

AbstractSalinization and alkalization are global environmental issues, and a growing area of saline‐alkali land has been developed as paddy fields. However, the information on the characteristics and driving mechanisms of greenhouse gas (i.e., methane (CH4), carbon dioxide (CO2) and nitrous oxide (N2O)) and ammonia (NH3) emissions from paddy fields with different saline‐alkali levels is limited. We conducted a 137‐day mesocosm experiment to investigate these issues using light (L), moderate (M), and heavy (H) saline‐alkali soils with a history of reclamation of 20, 4 and 2 years, respectively. The results demonstrated that both the cumulative CH4 and NH3 fluxes in H treatment were significantly (p < 0.05) higher than L. While, the increasing saline‐alkali levels reduced the cumulative CO2 and N2O fluxes, respectively. With the increasing saline‐alkali levels, the species richness and diversity of microbial communities decreased. High saline‐alkali level inhibited the growth of ammonia‐oxidizing archaea, resulting in less N2O produced by nitrification, thus reducing N2O emission. Cumulative CH4 flux and the mcrA gene copy numbers showed a significant (p < 0.05) negative correlation. The gene copy number in H treatment was lower than M and L, respectively. The highest global warming potential and greenhouse gas intensity were observed in H treatment. Overall, recently reclaimed saline‐alkali paddy field with an initial heavy saline‐alkali level may be a hotspot of farmland CH4 and NH3 emissions, highlighting the necessity of optimizing water and fertilizer management for controlling these gas emissions at the initial stage of developing saline‐alkali lands into paddy fields.

Fitness and niche differences are both important in explaining responses of plant diversity to nutrient addition.

Plant species loss due to eutrophication is a common phenomenon in temperate perennial grasslands. It occurs in a non-random fashion and is usually explained by increased competitive size asymmetry between co-occurring winner (tall species with optima in productive habitats) and loser species (small-statured plants typical for unproductive habitats). It remains unclear why nutrient addition decreases diversity in communities consisting of losers only, whereas it has little effect on winner-only communities. Here, I used the framework of modern coexistence theory to explore fertilization-driven changes in fitness and niche differences between different combinations of field-identified winner (W) and loser (L) species. I experimentally estimated competition parameters for plant species pairs constructed from a pool of eight species, including pairs of species from the same (WW, LL) and different species categories (LW) grown for approximately two years in control and fertilized conditions. Concurrently, I also followed plant species diversity in mesocosm communities constructed from the same species pool (four-species communities including winners, losers, or both) exposed to control and nutrient addition. I found that nutrient addition can reduce but, unexpectedly, also promote species coexistence depending on the type of species pairs. Whereas nutrient addition eroded coexistence of losers with winners, but also with other losers, treatment had the opposite effect on the persistence of winner species. Fertilization induced large fitness differences between species in loser-winner and loser-loser combinations, but had little effect on the fitness differences of species within the winner-winner combination. In addition, the persistence of winner pairs was promoted by larger niche differences compared to loser species, irrespective of soil nutrients. The differences in how nutrient addition modified coexistence at the pairwise level was reflected by differences in evenness of multispecies communities assembled from the corresponding species categories. These results suggest that the effect of eutrophication on plant species richness cannot simply be explained by an increased competitive asymmetry. To fully understand the effect of fertilization on the diversity of temperate grasslands, interspecific and intraspecific interactions should be explored while considering differences in species' ecological optima. This article is protected by copyright. All rights reserved.

Species composition and diversity of waterbird communities in Important Bird and Biodiversity Area (IBA) of South West Johor Coast, Malaysia

Abstract. Fauzi NA, Munian K, Shah AKMK, Norazlimi NA. 2023. Species composition and diversity of waterbird communities in Important Bird and Biodiversity Area (IBA) of South West Johor Coast, Malaysia. Biodiversitas 24: 3471-3480. Mangroves play a crucial role in supporting intertidal flats and providing habitats that enrich benthic communities, which in turn serve as feeding grounds for coastal waterbirds. However, the degradation of mangrove habitats caused by coastal reclamation activities indirectly impacts prey availability and, consequently, the populations of waterbirds. The coastline habitat along the Important Bird and Biodiversity Area (IBA) of the South West Johor Coast is currently under threat due to new and ongoing development projects involving large-scale reclamation activities. Therefore, this research was conducted to study the diversity and abundance of waterbirds and their relationship with prey availability. The study was conducted in three coastal mudflat sites along the South West Johor Coast, namely Tanjung Piai, Pontian Kechil, and Muar, from November 2020 to May 2021. The direct observation technique was used to determine the abundance of waterbirds, while the benthic core sampling method was employed to assess prey availability in all study sites. In total, 3,717 individual waterbirds, comprising 17 species, were counted across the three study sites. The study confirmed a significant positive relationship between the abundance of waterbirds and prey availability (R2=0.501). The results of this study serve as important baseline data and references for the conservation of waterbirds along the South West Johor Coast. Through the study, we believe that the relevant authorities are able to formulate sound conservation strategies to preserve the habitat for a vast diversity of waterbirds.

Effects of long‐term mowing on species diversity, biomass and composition of plant community in a semi‐arid grassland in northeastern China

AbstractQuestionsHow does long‐term, moderate‐intensity mowing affect plant community diversity, biomass, and composition in semi‐arid grasslands? And what are the underlying mechanisms that drive differences in plant community structure and functions between mowed and unmowed grasslands?LocationA semi‐arid grassland in Jilin Province, northeastern China.MethodsIn a 30‐year experiment, we investigated long‐term effects of mowing on the grassland ecosystem in northeastern China by comparing plant community diversity, biomass, and composition between mowed and unmowed permanent plots across six grasslands.ResultsLong‐term mowing did not affect plant species richness, but increased species evenness by 29%. Mowing had little effects on above‐ground (shoot) and below‐ground (root) biomass. The unchanged above‐ground biomass in the mowed areas was attributed to a trade‐off between biomass of grasses and forbs: mowing significantly increased forb biomass by 50%, but reduced grass biomass by 20% and the grass to forb biomass ratio by 46%. Mowing also reduced biomass of the dominant Leymus chinensis grass by 24% and litter biomass by 56%. Regression analyses indicated that the species evenness was negatively affected by L. chinensis biomass and litter biomass.ConclusionsThis study demonstrates that, although long‐term moderate mowing has limited effects on plant species richness and plant biomass, such a managed strategy can greatly reduce the dominance of grass species and allow the growth of forb species, leading to a higher species evenness in the plant community. This win–win situation promotes forage production for farmers while increasing plant diversity for conservation, suggesting that current mowing tactics can be a sustainable management practice in this ecosystem. However, the continuous loss of plant litter because of mowing may have negative influences on soil nutrient availability in the long run. From this perspective, a short‐term halt in mowing or fertilization that allows plants and soil nutrients to recover could represent a more optimal protocol for management.

Density vs. Cover: Which is the better choice as the proxy for plant community species diversity estimated by spectral indexes?

Recent studies have shown the crucial role of plant cover in the spectral signals of remote sensing images. However, how plant species cover affects the spectral-species diversity relationship remains largely unknown. To clarify this, we conducted a study in wetlands and obtained high spatial resolution multispectral images collected by unmanned aerial vehicles (UAVs). Quadrat information was obtained through a field survey. The traditional species diversity indexes and Hill numbers of each quadrat were computed by species density and cover. The mean, standard deviation, and coefficient of variation of the normalized difference vegetation index (NDVI) were computed based on the multispectral images. We employed univariate and multivariate regression models to assess the ability of spectral information to predict species diversity and the explanatory degree of variables to the multivariate regression models were decomposed. The results showed that rather than species density, spectral indexes were more strongly related to species diversity indexes computed by species cover, and the robustness and universality of the methods that predict plant species diversity based on spectral indexes have been improved by considering species cover. Meanwhile, in light of the flexibility of Hill numbers that assign different weights to dominant and rare species in the community, we believe that Hill numbers are the better choice in the spectral-species diversity studies, which can suitable to various communities with different density-cover relationships. In addition, our study also provided an insightful perspective for future spectral-plant species diversity research.

Diversity of lithophytic moss species in karst regions in response to elevation gradients.

The distribution pattern of species diversity along various elevation gradients reflects the biological and ecological characteristics of species, distribution status and adaptability to the environment. Altitude, a comprehensive ecological factor, affects the spatial distribution of species diversity in plant communities by causing integrated changes in light, temperature, water and soil factors. In Guiyang City, we studied the species diversity of lithophytic mosses and the relationships between species and environmental factors. The results showed that: (1) There were 52 species of bryophytes in 26 genera and 13 families within the study area. The dominant families were Brachytheciaceae, Hypnaceae and Thuidiaceae. The dominant genera were Brachythecium, Hypnum, Eurhynchium, Thuidium, Anomodon and Plagiomnium; The dominant species were Eurohypnum leptothallum, Brachythecium salebrosum, Brachythecium pendulum etc. The number of family species and dominant family genera increased first and then decreased with the increase of altitude, and their distribution in elevation gradient III (1334-1515m) was the largest, with 8 families, 13 genera and 21 species. The elevation gradient I (970-1151m) was the least species distributed, with 5 families, 10 genera and 14 species. The dominant species with the largest number in each elevational gradient were Eurohypnum leptothallum, Brachythecium pendulum, Brachythecium salebrosum and Entodon prorepens; (2) There were five kinds of life forms in different elevation gradients, including Wefts, Turfs, Mat, Pendants and Tail. Among them, wefts and turfs appeared in all elevations, while a small amount of Pendants appeared in the area of elevational gradient I (970-1151m), and the most abundant life form was found in the range of elevational gradient III (1334-1515m); (3) Patrick richness index and Shannon-Wiener diversity index were highly significantly (p<0.01) positively correlated, both of which increased and then decreased with elevation, reaching a maximum at elevation gradient III (1334-1515m); The Simpson dominance index had a highly significant (p<0.01) negative correlation with the Patrick richness index and the Shannon-Wiener diversity index, which showed a decreasing and then increasing trend with increasing altitude; Pielou evenness index showed no discernible trend; (4) β diversity study revealed that while the similarity coefficient tended to decrease with increasing altitude, the species composition of bryophytes increased. The elevation gradient II (1151-1332m) and elevation gradient I (970-1151m) shared the most similarities, whereas elevation gradient III (1515-1694m) and elevation gradient I shared the least similarities (970-1151m). The findings can enrich the theory of the distribution pattern of lithophytic moss species diversity at distinct elevation gradients in karst regions, and serve a scientific and reasonable reference for restoring rocky desertification and protecting biodiversity there.

Impacts of Forest Management on the Biodiversity and Sustainability of Carya dabieshanensis Forests

Natural secondary Carya dabieshanensis forests comprise the natural wealth of the Dabie Mountains, which maintain the ecological balance of this region and enhance the incomes of farmers. However, forest ecosystems are being increasingly challenged due to increasing long-term anthropogenic development and management. Elucidating the impacts of management intensity and duration on the diversity and stability of vegetation communities in natural secondary Carya dabieshanensis forests is of great significance toward achieving sustainable forest management. For this study, we compared the effects of three forest management intensities (no management (CK), extensive management (EM), and intensive management (IM)), and five management durations (0, 3, 8, 15, and 20 y) on species diversity and the stability of vegetation communities (trees, shrubs, and herbaceous layers) of a Carya dabieshanensis forest. Our results revealed that the diversity of the vegetation communities continued to decline following the onset of management activities. The diversity, dominance, evenness, and richness indices of the vegetation communities decreased by 53.37%–62.77%, 46.04%–59.17%, 32.58%–53.55%, and 50.18%–51.30%, respectively, after 20 y of forest management. Intensive management translated to species diversity loss more so than extensive management. All vegetation communities of the forest stands under study were generally unstable; however, the stability they did have was not at risk under greater management intensity and duration, and neither did greater species diversity enhance it. This study provides new evidence to support the non-synchronicity of species diversity and community stability in forest resident vegetation communities. Since the species diversity and structural composition of tree layers have a positive effect on community stability, so we suggest that both extensive and intensive forest lands need to retain or replant more tree species other than Carya dabieshanensis.

Climate-smart forestry in the world’s drylands: A review of challenges and opportunities

Land degradation and desertification are widespread across the world’s drylands. These processes are substantially affected by climatic change, with long-term and severe droughts on the one hand, and high intensity rainstorms and devastating floods on the other hand. Simultaneously, land-use change and mismanagement practices have led to processes of accelerated soil erosion, depletion of soil organic carbon pools, and the degradation of extensive drylands. Forestry has been accepted as an effective means for restoring degraded drylands, and for attaining a range of regulating, provisioning, supporting, and cultural ecosystem services. Specifically, forestry is widely perceived as an effective means for soil erosion control, organic carbon sequestration, microclimate improvement, and climate change mitigation. However, forestry in drylands often proves to generate substantial environmental challenges, resulting in deterioration of ecosystem functions and health. The objective of this essay is to review the challenges and opportunities induced by dryland afforestation and reforestation, and highlight the need to attain climate-smart strategies for establishing and managing these land-uses. Particularly, tree species invasion and allelopathy, which are common in dryland forestry projects, jeopardize species richness and diversity of native vegetation communities. Further, the challenges linked with tree invasiveness necessitate predicting the distribution of potentially invasive species and foreseeing their impacts on the recipient ecosystems under projected climate change scenarios. The effect of allelopathy is significant under limited water availability conditions and is expected to be determined by the expanding drylands and intensifying aridity worldwide. Therefore, judicious selection of tree species should not only focus on ones with high water-use efficiency, low flammability, high pest resistance, and fast growth, but also on low invasiveness and allelopathic capacities. Insights of this essay may be used by land managers, stakeholders, and policy makers involved in environmental development of drylands.

СОСТОЯНИЕ ПЛАНКТОННЫХ СООБЩЕСТВ НИКОЛЬСКОГО УСТЬЯ РЕКИ СЕВЕРНАЯ ДВИНА В ОСЕННИЙ ПЕРИОД 2022 ГОДА

The work is part of the environmental monitoring of the Nikolskaya estuary. Severnaya Dvina, carried out in 2022, with the aim of comprehensive research of aquatic biological resources and their environment. Information was obtained on the species diversity and structure of plankton communities of the studied object belonging to the drainage basin of the Severnaya Dvina River. The taxonomic composition of phytoplankton and zooplankton in the navigation period of 2022 is shown. Species diversity was assessed using the Shannon index, based on the relative abundance of species, the Menhinik, index, which determines species richness, the average abundance and biomass of phytoplankton of the Nikolsky Estuary were determined. The Pantle-Bukka saprobity index was calculated to assess the pollution of natural waters. According to observations, 53 algae taxa with a rank below the genus and 21 zooplankton organisms have been registered. It was found that the basis of algoflora was diatoms. Copepoda copepods formed the basis of the zooplankton community. New data on the state of phytoplankton and zooplankton communities can serve as an informational and methodological basis for the development of environmental monitoring programs for aquatic ecosystems in the region.

DISTRIBUTION PATTERN OF TREMATODES IN A LARGE SETTLEMENT OF THE PONTO-AZOV MOLLUSK LITHOGLYPHUS NATICOIDES (C. PFEIFFER 1828) (GASTROPODA, HYDROBIIDAE) FROM THE UPPER SECTION OF THE UGLICH RESERVOIR (UPPER VOLGA BASIN)

The Ponto-Azov gastropod mollusk Lithoglyphus naticoides (C. Pfeiffer, 1828) naturalized in the Uglich Reservoir relatively recently (in 2013-2015). The main objective of this study is a comparative analysis of the species diversity and structure of trematode communities in different biotopes, occupied by L. naticoides after the initial phase of its spread in the upper section of this water body (downstream the city of Dubna), characterized by a complex hydrological regime. Approximate coordinates of the geographical center of the large settlement of L. naticoides are 56°53ʹN, 37°25ʹE. It is found that by 2019-2021 the average density of L. naticoides in this settlement reached a consistently high value of about 450 ind./m2. Judging by the variability of shell height in adult mature L. naticoides individuals, even within the same settlement, optimum habitat conditions for this mollusk differ significantly in different biotopes. In a comparative aspect, data from two main hydrobiological sampling locations are considered: in the open part of the reservoir and at the mouth of a large tributary - the Dubna River. It is shown that at both locations the species composition of trematodes in L. naticoides is similar and includes, in particular, parthenitae of Apophallus muehlingi (Jägerskiöld, 1899), Apophallus (= Rossicotrema ) donicus (Skrjabin et Lindtrop, 1919), Parasymphylodora markewitschi Kulakowskaja, 1947, Nicolla skrjabini (Iwanitzky, 1928). However, Sanguinicola volgensis (Razin, 1929) parthenitae, dominant in L. naticoides in the open part of the reservoir, is not found in the sample of mollusks from the mouth of the Dubna River. As compared to the sampling site in the open part of the reservoir, at the mouth of the Dubna River the level of infection with parthenitae of other species is significantly lower: N. skrjabini and P. markewitschi - 7 times, Apophallus spp. - 8 times, Xiphidiocercaria sp. - 13 times. The ratio of males to females among mature individuals of L. naticoides turns out to be close to 1:1, which is usual for many freshwater mollusks. In general, the high occurrence (the infection prevalence - the proportion of infected individuals in the host sample P±SE, %) in the open part of the reservoir indicates the presence of prerequisites for serious outbreaks of helminthoses: Xiphidiocercaria sp. (9.16±2.52%), Apophallus spp. (11.45±2.78%), P. markewitschi (7.63±2.32%), N. skrjabini (7.63±2.32%), S. volgensis (63.36±4.21%). At the same time, according to the data obtained, further spread of L. naticoides in some tributaries of reservoirs in the Upper Volga basin may not have such serious parasitological consequences.

Unveiling the transition from niche to dispersal assembly in ecology

A central goal in ecology is to understand what maintains species diversity in local communities. Classic ecological theory1,2 posits that niches dictate the maximum number of species that can coexist in a community and that the richness of observed species will be below this maximum only where immigration is very low. A new alternative theory3,4 is that niches, instead, dictate the minimum number of coexisting species and that the richness of observed species will usually be well above this because of ongoing immigration. We conducted an experimental test to discriminate between these two unified theories using a manipulative field experiment with tropical intertidal communities. We found, consistent with the new theory, that the relationship of species richness to immigration rate stabilized at a low value at low immigration rates and did not saturate at high immigration rates. Our results suggest that tropical intertidal communities have low niche diversity and are typically in a dispersal-assembled regime where immigration is high enough to overfill the niches. Observational data from other studies3,5 suggest that these conclusions may generalize to other ecological systems. Our new experimental approach can be adapted for other systems and be used as a ‘niche detector’ and a tool for assessing when communities are niche versus dispersal assembled.