Lower Species Richness Research Articles

Comparison of Environmental DNA Metabarcoding and a Traditional Survey Method for Assessing Fish Diversity and Distribution Along Salinity Gradient in an Urban Brackish Reservoir, China

With the decrease in fish diversity, the monitoring of fish has become a current research hotspot. Here, the fish diversity and spatial distribution along a salinity gradient (0.28‰–3.32‰) in Xinglinwan Reservoir, China, were investigated using eDNA and the TSM. With the combination of both methods, 12 species from 6 orders, 9 families, and 11 genera were observed. The invasive species Oreochromis niloticus had the highest relative abundance, accounting for 56.91% in the TSM and 89.80% in eDNA, respectively. eDNA detected 83.33% of the species detected using the TSM, and an additional six species (50.0% of the total species) were detected via only eDNA. Moreover, eDNA supplemented the unavailable abundance data from the TSM. The TSM revealed that the diversity and relative abundance of fish inhabiting seawater and brackish water increased with an increase in salinity, but this was not found using eDNA. Thus, our study highlights that Xinglinwan Reservoir has a low species richness and is suffering from the great harm of ecological invasion. Our findings also show that eDNA could be reliable for providing a comprehensive picture of fish, but discriminating the spatial heterogeneity of fish communities is a challenge for its widespread adoption in lentic brackish systems.

Suitability of invasive gobies as paratenic hosts for acanthocephalans of the genus Pomphorhynchus sp.

Ponto-Caspian gobies became highly abundant in many regions outside their native distribution range (e.g. in the Rhine River system). In the newly invaded habitats, the parasite communities of the invasive gobies are characterized by a lower species richness compared to their native range. Interestingly, acanthocephalans of the genus Pomphorhynchus are highly abundant, although they do not become mature and mostly remain encapsulated in the abdominal cavity as preadults. Thus, gobiids could either represent a dead-end host for Pomphorhynchus sp. declining its population (dilution effect) or act as a paratenic host that could increase the infection pressure if the infected gobies are preyed upon by appropriate definitive hosts (spill back). To determine which of the 2 scenarios the gobiids contribute to, we conducted 2 infection experiments using smaller and larger individuals of the definitive host chub (Squalius cephalus), infected with preadults of Pomphorhynchus sp. collected from the abdominal cavity of Neogobius melanostomus. The results showed that preadults were able to complete their development and mature in the definitive host with mean recovery rates of 17.9% in smaller and 27.0% in larger chubs. Successful infections were observed in 62.0% and 80.0% of the smaller and larger chubs, respectively. Our study demonstrated that gobies can theoretically serve as a paratenic host for acanthocephalans of the genus Pomphorhynchus, and that infection might spill back into the local fish community if infected gobies are preyed upon by suitable definitive hosts of Pomphorhynchus sp. such as large barbel or chub.

Nutrients, isolation and lack of grazing limit plant diversity in restored wetlands

Abstract Agricultural intensification has led to the loss of most natural wetlands from human‐dominated landscapes but, in recent decades, wetland restoration has gained traction worldwide. Restoration of suitable habitat conditions is hampered by nutrient residues from decades of high‐input farming, by continued input of nutrients from surrounding farmland and by incomplete restoration of natural hydrology. We assessed the effect of wetland restoration and disturbance (grazing) on vascular plant and bryophyte diversity in restored wetlands in Denmark at plot and landscape scales. Compared to near‐natural wetlands, we found a lower species richness and community uniqueness in restored wetlands, but we also found that grazing had a positive effect on vascular plant richness in restored wetlands. The size of the local species pool, presence of near‐natural habitat prior to restoration and near‐natural restored hydrology all had positive effects on plant diversity, whereas high soil iron and nitrogen had negative effects. Synthesis and applications: Restoration of plant diversity in wetlands is challenging, but our results point to potential remedies: plan restoration areas near colonisation sources of the target biota, restore hydrology to near‐natural conditions, discontinue nutrient loads from surrounding arable land and restore near‐natural grazing regimes. Bryophytes may be particularly useful as indicators for successful restoration of wetlands.

Sandy beach macrofauna along the shore of Fiji: low species richness due to beach morphodynamics or low productivity in coastal waters?

Sandy beach macrofauna along the shore of Fiji: low species richness due to beach morphodynamics or low productivity in coastal waters?

Effects of weed management on soil metagenomic composition in cultivated chickpea fields

Abstract Non-chemical methods, including mechanical and manual weed management are important for improving crop yields and preserving soil microbial diversity. In Tunisia, chickpea cultivation uses a combination of these methods to suppress weeds. This study aimed to evaluate the impact of weeding practices on chickpea (Cicer arietinum L. cultivar REBHA) yield and soil microbial diversity. Field experiments were conducted at the Technical Center for Biological Agriculture in Essaida, Tunisia, using six plots with manual and no weeding treatments. Chickpea yield was measured, and soil samples were collected for metagenomic analysis. Floristic surveys identified 13 weed species, with Chenopodium album L., Rumex acetosa L., and Urtica dioica L. being the most dominant. Seed yield ranged from 23.2 to 26.2 qls/ha in non-weeded plots and from 25.1 to 30.1 qls/ha in weeded plots, showing an increase in yield (11.75%) with manual weeding.
Soil metagenomics revealed changes in bacterial community composition between the two treatments. The dominant phylum was Pseudomonadota, whose relative abundance increased from 24.88% in non-weeded plots to 34.76% in weeded plots. Alpha diversity indices showed lower species richness and diversity in weeded soils, with 62000 OTUs in weeded plots compared to 43202 OTUs in non-weeded plots. Betaproteobacteria and Alphaproteobacteria exhibited higher OTU counts in weeded soils. The Simpson diversity index was lower in non-weeded soils (0.025) than in weeded soils (0.075), indicating a more irregular microbial distribution in non-weeded plots. Thus, manual weeding improved chickpea yield and altered the soil bacterial community, increasing diversity in key microbial taxa. This study highlights the complex interaction between weed management practices and soil microbial ecosystems, which may influence crop productivity.

High functional vulnerability across the world’s deep-sea hydrothermal vent communities

At the nearly pristine hydrothermal vents of the deep sea, highly endemic animals depend upon bacteria nourished by hydrothermal fluids that emerge as outflows from the seafloor. These animals are remarkable in tolerating extreme conditions, including high heat, toxic reduced sulfide, and low oxygen. Here, we test whether the extreme vent environment has selected for functionally similar species across the world's deep ocean, despite well-established global geographic patterns of high phylogenetic distinctness. High functional redundancy in species pools within regions suggests that the extreme environments select for species with specific traits. Yet, some regions emerge as functional hotspots where species pools with distinct functional trait compositions may represent geological idiosyncrasies of the habitats. Moreover, many species are functionally unique, an outcome of low species richness in a system where the species pool is small at all scales. Given the high proportion of functionally unique species, simulated species extinctions indicate that species losses would rapidly translate to the elimination of functionally irreplaceable species and could tip vent systems to functional collapse. Ocean changes and human-induced threats are expected to significantly impact many vent species as human activities expand in the remote deep sea. The opportunity exists now to take precautionary actions to limit the rates of extinction now ubiquitous in more accessible areas of Earth.

Small Streams Support Beta Diversity in Neotropical Fish Assemblages in the Upper Paraná River Basin

ABSTRACTVariation in species composition along an environmental gradient (β‐diversity) can inform our understanding of biodiversity patterns and species composition. Beta diversity can be partitioned into species contributions to beta diversity (SCBD) and local contributions to beta diversity (LCBD). While SCBD describes the variations in species composition among samples, LCBD measures the uniqueness of a biological community within a larger ecosystem. Recently developed metrics enabled the estimation of species contribution to total beta diversity (SCBD) and the contribution of individual sites to total beta diversity (LCBD). Utilising these metrics, a one‐time survey of 275 sampling points within four sub‐basins of the Upper Paraná River Hydrographic Basin (low‐flow streams, < 5 m3/s) was conducted to assess fish community composition. Our results show that limnological influences at different scales contribute to higher LCBD. However, land use and species richness were not directly linked to this outcome, suggesting that sites with fewer fish species along sub‐basins contributed to higher beta diversity. It was concluded that beta diversity is more influenced by limnological characteristics and the position of sampling sites along the longitudinal gradient than that based on variations in species composition (SCBD). Moreover, high LCBD values were even found in portions of the gradient with lower species richness. This means that small streams in the sub‐basins of the upper Paraná River are unique and are comprised of varied habitats that contribute to increasing diversity. As such, they should be seen as a target in the development of environmental policies designed to conserve their pristine condition.

Evaluating Environmental Programs: Long-Term Monitoring of Crustacean Assemblages in a Polluted Estuary

We assessed the environmental quality of the Odiel-Tinto estuary, one of the most polluted in the world, by analysing the spatial variation of subtidal soft-bottom crustacean assemblages from 2000 to 2016. Our primary goal was to evaluate whether corrective measures implemented since 1986 have resulted in significant ecological improvement. The assemblages were structured according to the natural gradient from the estuary to the marine environment. Throughout the study, the assemblages exhibited low species richness and abundance (e.g., over 3 species and 180 individuals/m2 in the inner areas; 19 species and 510 individuals/m2 in the mouth zone). However, 2016 saw an increase in both species number and total abundance (e.g., over 5 and 24 species in the inner and mouth areas, respectively). Despite these observations, the Odiel-Tinto system harboured fewer species (24 species) compared to nearby estuaries like the Guadiana and Guadalquivir (over 50 species). Although there were signs of changes in the estuary over the sampling periods (e.g., a slight increase in richness and diversity in 2016 compared to 2002 and 2004), these fluctuations are likely characteristic of a highly dynamic environment rather than indications of genuine ecological recovery. These findings highlight the need for a long-term monitoring program, which should also encompass intertidal mudflats due to their higher density and biomass, easy accessibility, and reduced exposure to the impacts of recurrent maintenance dredging of the navigation channel.

Interannual differences vs small-scale spatiotemporal variability of spring zooplankton in the Crimean marine hypersaline lake

Ecosystems in the shallow marine hypersaline environment, such as marine lakes, are among the most changeable and have significantly lower species richness than freshwater and marine. It could be assumed that the intricate interconnections in hypersaline water ecosystems are easier to understand than in other aquatic ecosystems. Interannual differences vs small-scale spatiotemporal variabilities were studied in the spring zooplankton of hypersaline Lake Moynaki from 2019 to 2023. Salinity, water temperature, wind speed and direction were measured along with zooplankton sampling. The average spring wind speed and water temperature varied significantly from year to year, seemingly with a certain cyclicity. In total, 17 species were noted in zooplankton. The copepods Acanthocyclops vernalis and Arctodiaptomus salinus were not previously recorded in the lake. Bottom species were found in the plankton, among which the oligochaete Nais pseudobtusa, the gastropod Bittium reticulatum, and dragonfly larvae Gomphus sp. had not previously been found in the lake. Only four species, Gammarus aequicauda, Eucypris mareotica, Moina salina, and Cletocamptus retrogressus were regularly observed en masse. On average, the total zooplankton abundance near the windward shore was 2 times higher than that near the leeward shore and the abundance of individual species was from 2 to 5 times higher. If the values near only one coast were used, then the range of interannual differences would be underestimated or overestimated by approximately 2–4 times. Based on the zooplankton similarity in different years, all years except 2019, are grouped into a single cluster. Various changes are occurring in the lake, which are difficult to present as a complete picture of the cause-and-effect relationships that determine them.

Elevational and Seasonal Patterns of Plant-Hummingbird Interactions in a High Tropical Mountain.

Tropical mountain ecosystems harbor diverse biological communities, making them valuable models for exploring the factors that shape ecological interactions along environmental gradients. We investigated the spatial and temporal drivers of plant-hummingbird interaction networks across three forest types (pine-oak, fir, and subalpine) along a tropical high mountain gradient in western Mexico (2400 to 3700 m.a.s.l.). We measured species abundance, diversity, morphology, and interaction frequencies. Plant diversity metrics significantly declined in the highest elevation subalpine forest, whereas hummingbird diversity remained consistent across elevations. Interaction networks were similarly nested across elevations, but they were more specialized in the subalpine forest, where lower plant species richness and higher floral abundance led to greater resource partitioning among hummingbirds. Plant-hummingbird networks were larger and less specialized during the dry season, driven by greater species diversity and abundance. Species turnover explained network variation along the elevational gradient, while interaction rewiring and the arrival of migratory hummingbirds explained changes between seasons. Phenological overlap was the most important driver of the observed variation in interaction frequencies across elevations and seasons. Flower abundance had a minor influence on interaction frequencies at low- and mid-elevation networks, and hummingbird abundance was significant for dry- and rainy-season networks. Morphological matching was significant in the low-elevation forest and in the dry season. Plant phylogenetic relatedness had negligible effects on interaction patterns, but hummingbird phylogeny influenced feeding preferences in high-elevation and rainy-season networks. Our findings highlight the role of species turnover, interaction rewiring, and phenological overlap in structuring plant-hummingbird networks, with specific effects of abundance, morphology, and phylogeny varying with elevation and season. High-elevation ecosystems play a crucial role as reservoirs of floral resources for both resident and migratory hummingbirds during resource-scarce periods, emphasizing their importance in maintaining biodiversity in tropical mountain gradients.

Edinburgh postpartum depression scores are associated with vaginal and gut microbiota in pregnancy

BackgroundPrenatal and postpartum depression may be influenced by the composition of host associated microbiomes. As such, the objective of this study was to elucidate the relationship between the human gut or vaginal microbiomes in pregnancy with prenatal or postpartum depression. Methods140 female participants were recruited at their first prenatal visit and completed the Edinburgh Postnatal Depression Scale (EPDS) to screen for depression and anxiety, in addition the EPDS was completed one month postpartum. Vaginal and stool biospecimens were collected in the third trimester, analyzed using 16S rRNA gene sequencing, and assessed for alpha and beta diversity. Individual taxa differences and clustering using the k-medoids algorithm enabled community state type classification. ResultsParticipants with higher postpartum EPDS scores had higher species richness and lower abundance of L. crispatus in the vaginal microbiota compared to those with lower EPDS scores. Participants with a higher prenatal EPDS score had lower species richness of the gut microbiome. Participants with a vaginal community state type dominated by L. iners had the highest mean prenatal EPDS scores, whereas postpartum EPDS scores were similar regardless of prenatal vaginal state type. LimitationsOur small sample size and participant's self-report bias limits generalizability of results. ConclusionsDepression in the prenatal and postpartum period is associated with the composition and diversity of the gut and vaginal microbiomes in the third trimester of pregnancy. These results provide a foundational understanding of the microbial relationships between maternal health and depression for identifying potential therapeutic treatments.

Spatiotemporal Changes and Recovery of Benthic Macroinvertebrate Communities after the Hebei Spirit Oil Spill in the Subtidal Area around the Taean Peninsula in South Korea

Marine oil pollution is a significant environmental issue that significantly threatens ocean ecosystems. It occurs frequently and has devastating consequences for marine life, coastal habitats, and human communities. We examined the recovery of benthic macroinvertebrate communities in shallow subtidal areas following the Hebei Spirit oil spill around the Taean Peninsula, South Korea, in 2007. Benthic macroinvertebrates were collected seasonally from 15 survey sites between 2008 and 2015. Immediately after the spill in 2008, species richness and density of benthic macroinvertebrates decreased by 66.7% and 37.0%, respectively, compared to before the oil spill in 2007. Cluster analysis based on benthic macroinvertebrate communities delineated the communities from 2008 to 2009 as a distinct cluster characterized by markedly low species richness. Communities from other periods exhibited spatiotemporal variability based on the sampling location and sediment characteristics. By 2011, species richness and density had recovered to levels similar to those in 2007, which was particularly pronounced regarding the resurgence of arthropods and mollusks. Notably, populations of amphipods that are particularly sensitive to oil, such as Urothoe sp. and Byblis spp., showed signs of recovery in 2011; however, recovery of the benthic community at the site nearest to the oil spill area, was not evident until July 2013, as indicated by the benthic opportunistic polychaete amphipod index. This underscores that prolonged time periods are required for communities to fully recuperate after oil spills.

Isolation limits spring pollination in a UK fragmented landscape

Animal-mediated pollination determines the reproductive success of most flowering plants; this process however can be disrupted by environmental degradation, with habitat loss and fragmentation highlighted as a top driver of pollination deficits. Despite being a pervasive stressor worldwide, we still have rather limited empirical evidence on its effects on pollination services, especially for early spring pollination syndromes. We investigate this using a potted plant phytometry experiment in which we placed English Bluebell (Hyacinthoides non-scripta)—a species largely pollinated in spring—into a fragmented woodland habitat. We selected 51 woodland patches which varied in both size and distance from each other and placed 153 pots of bluebell plants in the patches for c.4 weeks to measure pollination. The woodlands were located in a matrix of grassland, the latter being of low plant species richness and overall in the patches, woodland plants showed a positive species-area relationship. We collected traits on bluebell reproduction, these included the number, size, quality of seeds, the number of seed capsules and the number of flowers that failed to set any seeds. We found that seed traits responded differently to patch area and isolation. Patch isolation negatively affected the number of seeds and capsules, whilst it did not affect the size and quality of seeds. Patch area had no effect on any traits, suggesting that patch area might not necessarily be a factor that affects pollination in this species. The number of flowers that failed to set seed was unaffected by either patch area or isolation. Our study suggests that woodland fragmentation impacts the pollination of understory spring flowering plants. Our results highlight the use of multiple traits of phytometer plants to evaluate pollination and the importance of connectivity in maintaining pollination services in small-fragmented landscapes.

Mangrove forest ecological function is influenced by the environmental settings and the benthic fauna composition

Benthic communities perform many important roles within mangrove ecosystems and are responsible for facilitating many of the functions attributed to mangrove forests. For instance, they are instrumental in mediating mangrove system productivity, and provide crucial food for juvenile nekton. Despite their importance, very few studies have investigated the benthic community of mangrove forests, and among those the results are inconsistent. This variability manifests in strong location effects, with low organism density and species richness in Indo-Pacific mangroves, compared to West Atlantic sites. These regional difference are confounded by differences in within-region environmental settings (e.g. rainfall, tidal range, spatial location along the coastal mosaic), and this complicates the development of a clear understanding of underlying consistencies. To assess the influence of contrasting environmental influences on the benthic community of mangrove forests we studied the benthic community of Rhizophora stylosa forests at two coastal estuaries and along the shores of two islands within a 75 km radius. The results showed that the community composition differed among settings, with several taxa only occurring at one of the two forests type. Furthermore, Peracarida, a common prey found in the gut of juvenile fish, was only found through the island forests, but never observed within the estuarine forests. This indicates that environmental setting can play a key role in determining the nature of mangrove benthic assemblages and their potential ecological roles. Consequently, caution is required when attributing the ecological roles of mangrove forests without accounting for changes in settings. Additionally, we only investigated a single mangrove species within the same climatic region, meaning that even greater variability is likely when the full range of mangrove types, conditions and areas are assessed. Understanding this variation is important because it implies that mangrove forest restoration projects are unlikely to achieve their desired outcomes unless setting-specific conditions are understood and taken into account.

Investigating the Effect of Bacilli and Lactic Acid Bacteria on Water Quality, Growth, Survival, Immune Response, and Intestinal Microbiota of Cultured Litopenaeus vannamei.

Shrimp is one of the most important aquaculture industries. Therefore, we determined the effect of nitrifying-probiotic bacteria on water quality, growth, survival, immune response, and intestinal microbiota of Litopenaeus vannamei cultured without water exchange. In vitro, only Bacillus licheniformis used total ammonia nitrogen (TAN), nitrites, and nitrates since nitrogen bubbles were produced. TAN decreased significantly in the treatments with B. licheniformis and Pediococcus pentosaceus and Leuconostoc mesenteroides, but no differences were observed in nitrites. Nitrates were significantly higher in the treatments with bacteria. The final weight was higher only with bacilli and bacilli and LAB treatments. The survival of shrimp in the bacterial treatments increased significantly, and superoxide anion increased significantly only in lactic acid bacteria (LAB) treatment. The activity of phenoloxidase decreased significantly in the treatments with bacteria compared to the control. Shrimp treated with bacilli in the water showed lower species richness. The gut bacterial community after treatments was significantly different from that of the control. Linoleic acid metabolism was positively correlated with final weight and superoxide anion, whereas quorum sensing was correlated with survival. Thus, bacilli and LAB in the water of hyperintensive culture systems act as heterotrophic nitrifers, modulate the intestinal microbiota and immune response, and improve the growth and survival of shrimp. This is the first report on P. pentosaceus and L. mesenteroides identified as nitrifying bacteria.

Rock outcrops as interglacial refugia for plants: Ecological evidence from the forest‐steppe transition of Patagonia

AbstractIn the forest‐steppe transition of Patagonia from Argentina, the intense physical variability promotes the occurrence of contrasting vegetation units, among which is the saxicolous meadow developed on rock outcrops. In temperate and tropical regions, these geoforms of highly variable climate and topography, and poor soil development play an ecological and evolutionary role disproportionate to their reduced area. In Aguas Frías (38°46′S, 70°54′W), the range, diversity, density and adaptation of vascular plant species growing in the saxicolous meadow were compared to those of the surrounding steppe, forest and hygrophilous meadow. We hypothesize that rock outcrops exhibit a compositionally and functionally divergent, cold‐adapted flora of a previously more widespread distribution, allowing them to be categorized as refugia for species whose range retreated during the current interglacial. In comparison to the other units, the saxicolous meadow exhibited a small area, low plant cover, high total, native and rare species richness, high density and diversity of species, high richness of unique families and species and an exclusive presence of (rock) ferns. It also presented a high richness of endemic species with more extreme latitudinal and altitudinal distribution, particularly >46° S and >3000 m a.s.l. The similarity of species between the saxicolous meadow and the other units was low. Chamaephytes and nanophanerophytes were dominants, hemicryptophytes and geophytes were infrequent and mesophanerophytes and therophytes were absent. Equivalent results in terms of area of rock outcrops, and origin, strategy, composition, diversity and range of species were found in different regions. The biological and physical attributes would allow these outcrops to be characterized as reduced habitats of high diversity which could be acting as refugia for cold‐adapted plants. Conservation actions must prevent and mitigate the effects of fire, biological invasion and cattle grazing that represent the current threats to this ecosystem.

Typical earthworm assemblages of European ecosystem types

AbstractFor nature conservation and planning, terrestrial ecosystems are commonly classified based on their plant communities. Although soils are fundamental to ecosystem functioning, ecosystem classifications based on soil organisms are rare, and it is poorly understood whether their assemblage compositions follow existing classification schemes. We examined whether commonly used ecosystem types capture variation in earthworm (Lumbricidae) assemblages—a crucial biotic component of soil ecosystems. To this end, we created four ecosystem classifications by combining large‐scale climatic classifications (Biogeographic Regions [BGR] and Holdridge Life Zones [HLZ]) with small‐scale land cover classifications (CORINE Land Cover [CLC] and European Nature Information System [EUNIS]). European earthworm assemblage data from the sWORM and Edaphobase databases were analysed for variation in composition within and among ecosystem types, using Permutational Analysis of Variance and Analysis of Similarities. Additionally, we used Typical Species Analysis to establish typical earthworm assemblages (TAs) for each ecosystem type. Ecosystem classifications using the BGR explained more variance than HLZ, but HLZ showed a higher separation of assemblages between ecosystem types. The differentiation between Atlantic and Continental climates in the BGR could explain the superiority over the HLZ, which had only one category for the cool temperate zone of our study region. The typical assemblages contained on average six species, with some habitat generalists present in most. This study shows that combinations of ecosystem properties from different spatial scales can be used to distinguish between earthworm assemblages at the European level. However, earthworm assemblages across Europe were highly similar due to low species richness and the dominance of a few widespread species. This limits the possibility of applying TAs on large spatial scales, for example, for environmental monitoring. We suggest that future studies should explore the use of more species‐rich groups of soil organisms to characterize ecosystem types.

Grasslands support more diverse and resilient earthworm communities to climate change than croplands in Central Europe

Diversity and community composition of earthworms, key drivers of ecosystem functions, are increasingly threatened by global change, including climate and land-use change. However, empirical evidence for interactions of these concurrent drivers in affecting earthworm communities is scarce. Here, we investigated the effects of an experimentally imposed climate change scenario, including warming and altered precipitation patterns, and land use with two croplands (both conventional farming and organic farming characterize a three-year crop rotation) and two grasslands (intensively-used meadow and extensively-used meadow) on earthworm communities across different seasons and years in a field experiment. Compared with grasslands, earthworms in croplands have lower species richness (-26 %), abundance (-80 %), and biomass (-73 %), particularly the abundance of juveniles (-83 %) and Aporrectodea rosea (-76 %) as well as the biomass of juveniles (-84 %), A. rosea (-72 %), Octolasion cyaneum (-47 %), and Lumbricus terrestris (-83 %). Due to extreme droughts in Central Europe from 2018 to 2020, earthworm abundance and biomass were low across land-use types, but in grassland they increased (abundance: +80 %; biomass: +85 %) in 2021 presumably due to increased moisture conditions. Main effects of experimental climate change and intensified management practices as well as interaction of experimental climate change and land use on abundance and biomass of earthworms were non-significant. Notably, experimental climate change and land use interactively altered earthworm community composition, with the most pronounced difference between ambient and future climate in croplands than in grasslands. This indicates that earthworm community composition more sensitively reflects changes in environmental conditions than earthworm abundance and biomass, but the latter two negatively responded to prolonged drought conditions. Our results indicate that grasslands have a higher resilience of earthworm populations to buffer adverse environmental conditions than croplands. Overall, this study provides a comprehensive overview of the response of earthworms to inter-annual climatic variability and experimental climate change under different land-use types.

Unraveling microbial community variation along a salinity gradient and indicative significance to groundwater salinization in the coastal aquifer

Saltwater intrusion poses a global environmental challenge in coastal regions, profoundly influencing groundwater microbial communities and biogeochemical processes. This study aims to elucidate the origin of groundwater salinity and understand the response of microbial interactions to groundwater salination through stable isotopes and 16S rDNA gene sequencing. The findings reveal a significant increase in groundwater TDS from inland to the coastline, ranging from 0.5 g/L to 144.6 g/L. Ionic relationship and isotopic fractionation indicate that the high salinity in groundwater originates not only from paleo–seawater but also from the dissolution of halite. Salty groundwater exhibits lower species richness and diversity than fresh groundwater. TDS, SO42–, and NO2– are the pivotal factors shaping the microbial community of salty groundwater, while NO3– and H2SiO3 are dominant variables influencing fresh groundwater community. This study identifies the order Alteromonadales, family Alteromonadaceae, and genus Marinobacter as potential biomarkers of seawater or paleo–seawater sources. Phylogenetic molecular network analysis of microbial communities illustrates that groundwater salinization results in a more compact microbial network but enhances microbial interactions. Predicted functional genes indicate that sulfate reduction genes (sat, met3, aprA, aprB, dsrA, and dsrB) are more abundant in salty groundwater than in fresh groundwater, suggesting a high metabolic potential for sulfate. These results elucidate the pivotal role of groundwater salinization in microbial community evolution, shaping specific functional zones in coastal groundwater.

Impacts of spatiotemporal urban expansion on the species richness and functional traits of adults and sapling woody trees and shrubs of urban remnant forest patches

Remnant urban forests, or scattered patches of forest within urban areas, serve as crucial biodiversity reservoirs. Investigating how urban environments influence biodiversity within these forests is essential for enhancing conservation strategies. This study examined data from 15 remnant forest patches in Guiyang, China, to assess the impacts of spatiotemporal urban expansion on species richness and functional traits across different life forms and ontogenetic stages in both interior and edge habitats of these patches. Employing generalized linear regression models, we examined variables including the intensity of urban expansion, road density, type of expansion, compound terrain complexity, and the interplay between urbanization levels and the timeframe of urban development. Our results indicated that increased urban expansion intensity positively affected the species richness of shrubs, yet negatively influenced tree richness. Furthermore, high urbanization levels were associated with lower species richness in adult trees and the species in the sapling and shrub layers with high seed mass traits when the duration of urbanization was prolonged. Additionally, we observed that edge-expansion type urban growth notably increased the risk of losing species with resource-conservation traits compared to leapfrog growth patterns. These outcomes highlight the detrimental effects of intensive urban expansion and edge-expansion growth on the conservation of woody plants, especially those characterized by resource conservation traits. They also draw attention to the delayed impacts of urbanization on plant diversity. In response, we advocate for the reduction of urban expansion intensity and control over edge-expansion growth patterns to protect plant diversity in remnant forests. It is also critical to prioritize the conservation of remnant forest patches located in areas that have undergone extensive urbanization for prolonged periods, as these are particularly vulnerable to biodiversity loss.