Habitat Heterogeneity Research Articles

Analysis of the Diversity of Corticolous Lichens Associated with Tree Trunks in the Understories of Four Tropical Dry Forests of the Atlántico Department in Colombia

Tropical dry forests (TDFs) are unique ecosystems with high biodiversity, including a rich variety of lichen species. Lichens are sensitive to environmental changes and can serve as bioindicators of ecosystem health. This study examined the diversity of lichen communities at four TDF sites in the Atlántico Department of Colombia. More than 700 tree lichen specimens were collected and identified at the four sites. A total of 135 species of lichens were identified, of which 19 are possibly undescribed. The most diverse sites were Usiacurí and Repelón, both protected areas with relatively well-preserved forests. The findings of this study demonstrate that the Atlántico TDFs host a large diversity of lichens, with a significant number of records of new species. The observed differences in species composition between sites highlight the importance of habitat heterogeneity and anthropogenic pressures on lichen communities. The results emphasize the need for conservation strategies to protect these ecologically valuable lichen communities within the Atlántico TDFs.

Tectonic and climatic controls on plant biodiversity in the Hengduan Mountains, China

Mountainous regions contain some of the most dynamic landscapes in the world and host a majority of the global biodiversity hotspots. The Hengduan Mountains, located at the syntax of Eurasia and India, have a complex geological history associated with the hyperdiverse assemblage of species. Tectonics and geomorphic and climate processes in the Hengduan Mountains may have jointly caused the emergence of high biodiversity. We propose three mechanisms that may promote high-level montane biodiversity: habitat creation, habitat disruption, and habitat oscillations. We mapped species richness patterns for seed plants and computed phylogenetic endemism across the entire Hengduan region. We developed a set of geomorphic metrics regarding these mechanisms to link plant richness and phylogenetic endemism patterns. By estimating the component of species richness due to habitat heterogeneity, we isolate the component due to tectono-geomorphic processes. We found that regions of exceptionally high species richness are explained by a combination of habitat heterogeneity and tectono-geomorphic processes, while glaciation and high climate change velocity are associated with low richness, thus contributing to recent extinction. We interpret the richness of biodiversity hotspots in the Hengduan Mountains in terms of climatic and tectonic processes.

Unraveling global species richness patterns of the Lysmatidae family: a multi-scale and multi-hypothesis ecological approach

While diversity gradients are well-explored in macroecology, factors shaping species richness at broad scales remain debated. We investigated the species richness of the decapod family Lysmatidae across 4 spatial scales: realm, province, ecoregion, and local (2° × 2° grid cells). We tested 4 ecological hypotheses: physiological stress (PSH), resource availability (RAH), habitat heterogeneity (HHH), and anthropogenic impact (AIH). Occurrence data (52 Lysmatidae species) and environmental variables (salinity, temperature, primary productivity, bathymetry, coral richness, anthropogenic impact index) were obtained from online databases and literature. Fifteen regression models, incorporating spatial filters, were tested to assess the hypotheses. The highest Lysmatidae species richness occurred in the Tropical Atlantic and Central Indo-Pacific realms. Richness varied with scale, with the highest values in the transition between the tropical and subtropical zones. Bathymetry was associated with Lysmatidae richness across all scales, especially at local and ecoregional scales, while coral richness was related to province and realm scales. HHH explained Lysmatidae richness patterns at the realm scale. Variables related to PSH and AIH were associated with richness at the ecoregion and province scales. Our study emphasized the importance of scale in biodiversity research, influencing richness patterns in Lysmatidae, and pointed to bathymetry, coral richness, and temperature range as the main drivers of richness. As this study showed a relationship between Lysmatidae richness, coral richness, and temperature at 3 spatial scales, this family may be susceptible to the effects of climate change, such as tropicalization of subtropical zones and defaunation of tropical ecosystems, including coral reefs.

Individual return patterns of spawning flannelmouth sucker (Catostomus latipinnis) to a desert river tributary

Tributaries provide temporal and spatial habitat heterogeneity in river networks that can be critical for parts of the life history of a species. Tributary fidelity can benefit individual fish undergoing spawning migrations by reducing time and energy spent exploring new areas and leveraging previous experience, but anthropogenic activities that fragment or degrade these systems can eliminate those benefits. We used multistate models based on passive integrated transponder (PIT) detection data from 2013 to 2023 to estimate the proportion of flannelmouth suckers (Catostomus latipinnis) migrating to a tributary, McElmo Creek, from the mainstem San Juan River for spawning. Survival varied among years and among states. The top model for migration probability included sex, with males slightly more likely to migrate (0.93 vs 0.90), and the next model identified interannual variation in migration probability ranging from 0.875 to 0.999 across years, indicating high site fidelity. Individuals showed consistency in relative arrival timing across years, with the highest correlation generally during years with greater spring discharge and extended tributary residence time. Successful tributary spawning may be important for the maintenance of the mainstem San Juan River flannelmouth sucker population, but site fidelity may be maladaptive where tributaries are vulnerable to human alterations.

Plant virus community structuring is shaped by habitat heterogeneity and traits for host plant resource utilisation.

Host plants provide resources critical to viruses and the spatial structuring of plant communities affects the niches available for colonisation and disease emergence. However, large gaps remain in the understanding of mechanisms that govern plant-virus disease ecology across heterogeneous plant assemblages. We combine high-throughput sequencing, network, and metacommunity approaches to test whether habitat heterogeneity in plant community composition corresponded with virus resource utilisation traits of transmission mode and host range. A majority of viruses exhibited habitat specificity, with communities connected by key generalist viruses and potential host reservoirs. There was an association between habitat heterogeneity and virus community structuring, and between virus community structuring and resource utilisation traits of host range and transmission. The relationship between virus species distributions and virus trait responses to habitat heterogeneity was scale-dependent, being stronger at finer (site) than larger (habitat) spatial scales. Results indicate that habitat heterogeneity has a part in plant virus community assembly, and virus community structuring corresponds to virus trait responses that vary with the scale of observation. Distinctions in virus communities caused by plant resource compartmentalisation can be used to track trait responses of viruses to hosts important in forecasting disease emergence.

Remotely Sensed Variables Predict Grassland Diversity Better at Scales Below 1,000 km as Opposed to Abiotic Variables That Predict It Better at Larger Scales

AbstractGlobal spatial patterns of vascular plant diversity have been mapped at coarse grain based on climate‐dominated environment–diversity relationships and, where possible, at finer grain using remote sensing. However, for grasslands with their small plant sizes, the limited availability of vegetation plot data has caused large uncertainties in fine‐grained mapping of species diversity. Here we used vegetation survey data from 1,609 field sites (>4,000 plots of 1 m2), remotely sensed data (ecosystem productivity and phenology, habitat heterogeneity, functional traits and spectral diversity), and abiotic data (water‐ and energy‐related, characterizing climate‐dominated environment) together with machine learning and spatial autoregressive models to predict and map grassland species richness per 100 m2 across the Mongolian Plateau at 500 m resolution. Combining all variables yielded a predictive accuracy of 69% compared with 64% using remotely sensed variables or 65% using abiotic variables alone. Among remotely sensed variables, functional traits showed the highest predictive power (55%) in species richness estimation, followed by productivity and phenology (48%), spectral diversity (48%) and habitat heterogeneity (48%). When considering spatial autocorrelation, remotely sensed variables explained 52% and abiotic variables explained 41%. Moreover, Remotely sensed variables provided better prediction at smaller grain size (<∼1,000 km), while water‐ and energy‐dominated macro‐environment variables were the most important drivers and dominated the effects of remotely sensed variables on diversity patterns at macro‐scale (>∼1,000 km). These findings indicate that while remotely sensed vegetation characteristics and climate‐dominated macro‐environment provide similar predictions for mapping grassland plant species richness, they offer complementary explanations across broad spatial scales.

Soil Properties and Rhizosphere Microbes Community Structure Reveal Nitrogen Uptake Preferences and Nitrogen Use Efficiency of Two Ecotypes of Paphiopedilum micranthum

Paphiopedilum micranthum, an IUCN Red List species, is discontinuously distributed in the karst limestone mountain of southwest China and exhibits ecological specialization, typically through lithophytic and terrestrial ecotypes. Whether the distribution of rhizosphere bacteria and fungi in these different habitats is random or reflects soil preferences requires further investigation. A total of 73 samples from the core distribution areas in China, representing all habitats in two sites, were analyzed for soil differences by comparing edaphic properties and microbial community structure based on high-throughput sequencing of bacterial 16S rRNA genes and fungal ITS region sequences, alongside soil physiochemical data. The results showed no significant differences in microbial community richness and diversity across the heterogeneous habitats. However, significant differences in taxa were observed across various habitats. Dominant bacterial phyla included Actinobacteriota, Proteobacteria and Acidobacteriota, with dominant genera such as Crossiella, Pseudonocardia, 67-14, Mycobacterium and RB41. The primary fungal phyla were Basidiomycota and Ascomycota, featuring prominent genera such as Phlegmacium, Archaeorhizomyces, Trechispora, and Lepiota. There were 16 bacterial genera and 13 fungal genera associated with nitrogen transformation and fixation. Alkali-hydrolyzed nitrogen (AN) was identified as a main driver of soil bacterial and fungal community variation. Based on an analysis of soil physicochemical properties, ammonium nitrogen content was consistently higher than nitrate nitrogen across different habitats. Furthermore, across all heterogeneous habitats, P. micranthum showed no significant differences in nitrate nitrogen, ammonium nitrogen, or their ratio. The nitrogen-use efficiency of P. micranthum ranged from 7.73% to 9.87%, with the highest efficiency observed in the terrestrial habitat of Shedu. These results suggest that P. micranthum prefers habitats rich in organic matter and nitrogen, showing a preference for ammonium nitrogen uptake in natural conditions. Heterogeneous habitats affect plant nitrogen-use efficiency as well as changes in microbial community composition.

Geographic and ecological effects on species richness of liverworts worldwide

Liverworts are one of the oldest lineages of the extant land plants but the geographic patterns and ecological determinants of their species richness have not yet been studied at a global scale until now. Here, using a comprehensive global database, we find that regional species richness of liverworts in general 1) shows a clear latitudinal diversity pattern, 2) is highest in mountains, presumably reflecting the effects of habitat heterogeneity and the occurrence of cloud forest, 3) is more strongly influenced by contemporary climate than by climate change during the Quaternary, 4) is more strongly affected by precipitation‐related than by temperature‐related variables, reflecting the poikilohydric nature of liverworts and hence their water‐dependence, and 5) is more strongly affected by climate extremes than by climate seasonality. However, we find regional deviations from these general patterns, especially in the Southern Hemisphere where the distinct arrangement of land masses leads to different climatic patterns and thus climate–species richness relationships. Compared with other major land plant lineages, liverworts show the same importance of precipitation‐related factors as ferns, whereas in angiosperms temperature also plays an important role, reflecting the different physiological adaptations of these groups to drought and cold stress, and providing insights into the different evolutionary pathways taken by these lineages.

Spatial and temporal characterization of Aedes albopictus oviposition activity in candidate urban settings for sterile insect technique testing in La Reunion Island

BackgroundUnderstanding of mosquito spatiotemporal dynamics is central to characterize candidate field sites for the sterile insect technique (SIT) testing, and is critical to the effective implementation and evaluation of pilot sterile male release programs. Here, we present a detailed description of Aedes albopictus (Skuse) egg-laying activity over a 6-year period in urban areas identified as potential SIT testing sites on Reunion Island.MethodWeekly entomological collections using ovitraps were carried out in residential and adjacent uninhabited habitats in two urban areas, Duparc and Bois Rouge, in the municipality of Sainte Marie, Reunion Island. Time-series data incorporating the frequency of positive ovitraps and the total number of eggs/ovitrap recorded each time at each locality during the study period from May 2013 to December 2018 were analyzed with multifaceted statistical approaches including descriptive statistics and spatiotemporal analyses incorporating the role of climatic factors on overall ovitrap productivity.ResultsDuring the ovitrap survey, the proportion of egg-positive ovitraps differed among study sites (χ2 = 50.21, df = 2, P < 0.001), being relatively lower in Duparc (89.5%) than in Bois-Rouges (95.3%) and the adjacent buffer zone (91.2%). Within each neighborhood, Ae. albopictus egg abundance varied by month in a roughly seasonal pattern marked by a single peak occurring more regularly February each year, a decline at the onset of the austral winter in July, followed by a period of lower ovitrap productivity in August and September. Fluctuation in both positivity rate and eggs densities per ovitraps were related to annual and seasonal variations in local temperature and rainfall (P < 0.001 in all cases). The spatial analysis also captured substantial between- and within-habitats heterogeneity, whereby the overall ovitrap productivity was higher in residential areas than in the buffer zone.ConclusionsCollectively, these results reveal that the distribution of Ae. albopictus oviposition activity is shaped by local habitat heterogeneity and seasonal climatic factors. Overall, this study provides baseline insights into the reproductive dynamics of Ae. albopictus, which would assist in planning locally tailored SIT interventions, while addressing concerns related to focal areas of high egg-laying intensity and potential immigration of females from natural areas.

Distribution Patterns of Urban Spontaneous Vegetation Diversity and Their Response to Habitat Heterogeneity: A Case Study of Five Cities in Heilongjiang Province, China.

Spontaneous vegetation is an important component of urban biodiversity and an excellent agent for exploring the mutual feedback mechanism between urbanization and urban ecosystems. Rapid urbanization has had a significant impact on the composition, structure, and distribution patterns of urban spontaneous vegetation diversity. Studying the diversity distribution patterns and causes of urban plant communities is beneficial for understanding the formation and maintenance mechanisms of plant diversity in specific urban habitats. This study selected five cities in different climate subregions of Heilongjiang Province as research targets and conducted field research using uniform sampling and typical sampling methods. The composition, distribution pattern, and driving factors of spontaneous vegetation were analyzed. The results showed the following: (1) A total of 633 examples of spontaneous vegetation were recorded, belonging to 93 families and 341 genera, mainly consisting of herbaceous plants and native plants. (2) The diversity index and similarity index of spontaneous vegetation in gravel-type abandoned land habitats are higher than those in other habitat types, while the diversity index of spontaneous vegetation in trees and shrubs is lower, and there is no significant difference in regards to different habitats. (3) Urban population density is a key factor affecting the diversity of native plants, while woody plant coverage, patch area, and landscape trait index are key factors affecting non-native plants. (4) The results of canonical correspondence analysis (CCA) showed that the total explanatory power of environmental characteristic factors in regards to the distribution pattern of spontaneous vegetation was 7.5%. The closest distance between adjacent patches, the coverage of woody plants in patches, the distance from the city edge, the patch area, and the surface impermeability of the buffer zones were key factors affecting the distribution of dominant species in spontaneous vegetation communities. The research results will provide an important reference for the conservation of urban biodiversity and the construction of low-maintenance urban green space plant landscapes in Heilongjiang Province.

Drivers of nest site selection and breeding success in an Alpine ground-nesting songbird

AbstractBirds breeding in high-Alpine habitats must select a suitable breeding site and achieve successful reproduction within a restricted time. During four breeding seasons, we monitored nest sites of the Northern Wheatear (Oenanthe oenanthe), a high-Alpine long-distance migrant. We investigated how ecological factors predicted the selection of a site for nesting within the home range, using conditional logistic regression. Birds preferred south-exposed productive pastures on gentle slopes, interspersed with non-vegetated ground and human-made rockpiles. The direct vicinity of conspecific nests was avoided, as were shrubby or north-exposed areas. We investigated if habitat also influenced breeding success. We analysed the impact of environmental factors on breeding success, which was primarily driven by predation. The probability of the brood fledging successfully decreased on north-exposed slopes or on areas with low coverage of non-vegetated ground. The vicinity of conspecific nests did not have a clear effect. Further, we describe how breeding success varied within and between years. Within years, replacement broods had a higher breeding success. The apparent absence of variation in breeding success between years and a delay of the breeding period in the year with late spring onset suggest a high level of tolerance with respect to inter-annual variation of meteorological conditions. Since the preferred habitat is still widely available in the Alps and given the negative population trends in Western Europe, the Alpine range might serve as a refuge for the Northern Wheatear, as long as low-intensity management and heterogenous habitats are maintained.

Temporal niche partitioning as a potential mechanism for coexistence in two sympatric mesopredator sharks

Global marine biodiversity declines require bold and ambitious plans to safeguard ecosystem services. Overfishing, habitat loss and projected climate impacts have yielded deleterious effects on marine predators, in particular, driving increasing threat of extinction for many shark species with implications for ecosystem health. Identifying and protecting critical habitat areas for sharks is fundamental to their protection, and may allow for species recovery. Here we use baited remote underwater video stations to investigate spatial and temporal patterns of habitat use by sharks in a Special Area of Conservation (SAC) that is centrally important to the regional blue economy in the UK, the Cardigan Bay SAC. Our results show heterogeneous spatial habitat use and temporal trends in habitat sharing between smallspotted catsharks Scyliorhinus canicula and nursehounds S. stellaris. Nearshore reef habitats are substantially more important than non-reef habitats for both species. The relative abundance of each species, however, is roughly inversely seasonally proportional, with S. canicula and S. stellaris relative abundance highest in March and September, respectively. Temporal niche partitioning may be an important mechanism in marine systems, but has not been widely investigated in sympatric shark communities. These findings are directly relevant for ongoing development of the Welsh Marine Evidence Strategy (2019-2025) and the Welsh National Marine Plan, particularly to inform spatial planning to strengthen the role of SAC management design in protecting important shark areas.

Early Hominin Paleoenvironments and Habitat Heterogeneity

Environmental changes are often cited as the main driver of hominin evolutionary events, including major adaptive events such as bipedalism. Thus, researchers are particularly interested in the paleoenvironment of early hominins. The previous prevailing idea that hominins originated in expanding savannas is contradicted by the association of the earliest hominins with more closed and mesic (i.e., moderately wet) habitats. The Pliocene homi-nins that followed lived in a variety of habitats characterized by high levels of heterogeneity and permanent sources of water. This article reviews what we know of Mio-Pliocene hominin paleoenvironments, discusses the nature of the observed habitat heterogeneity associated with early hominins and implications for hominin paleoecology, and considers the challenges we face in showing a causative relationship between environmental change and major evolutionary events.

Elevational patterns of bird alpha and beta diversity in Haba Snow Mountain, Southwestern China: Implication for conservation

Understanding environmental patterns of species diversity is essential for nature reserve planning and biodiversity conservation. In this study, we explored the birds’ alpha and beta diversity along the elevational gradients in Haba Snow Mountain Nature Reserve (hereafter, HBSM), a global biodiversity hotspot, and studied which environmental factor is the main driver in explaining alpha and beta diversity patterns. Our results indicated that taxonomic, functional, and phylogenetic alpha diversity consistently exhibited hump-shaped patterns with similar peaks. After controlling for species richness, both functional and phylogenetic alpha diversity increased with elevation, and the peaks at 3400–3700 m. Mean pairwise functional distance remained nearly constant along the elevation band, whereas mean pairwise phylogenetic distance shown hump-shaped pattern, and the predicted MPD peaked at the fifth band (3100–3400 m a.s.l). The functional and phylogenetic structure of bird communities in HBSM were more clustered along the elevation gradients, suggesting environmental filtering likely drove the assembly processes. Additionally, primary productivity (NDVI and/or habitat heterogeneity) and/or precipitation were robust predictors of variation in most diversity metrics. For multiple-site beta diversity, we observed that high turnover component in taxonomic, functional, and phylogenetic dimensions, indicating distinct bird assemblages across various elevational bands. In pairwise beta diversity, the spatial turnover of taxonomic and phylogenetic aspects was higher than nestedness, revealing species replacement occurs relatively frequently between evolutionarily related species with similar niche and functional traits. Overall, our findings highlight the importance of considering both different dimensions and multifaceted diversity when assessing elevational patterns of bird diversity. This study also provides valuable insights into the structuring mechanisms of bird communities and informs conservation planning along elevational gradients in HBSM, and offers a comprehensive case on species richness along elevational gradients.

CURRENT STATUS OF SCABIOSA ISETENSIS POPULATIONS IN CENTRAL KAZAKHSTAN

The paper presents the results of studying the structure of 6 populations of Scabiosa isetensis growing in Central Kazakhstan. The floristic composition of communities, the ratio of life forms, ecological groups and age spectrum were evaluated. The floristic composition of the populations was 79 species from 56 genera and 23 families, of which the leading are the families of Asteraceae and Fabaceae. Herbaceous perennials predominate among life forms, mesophytes and xerophytes by ecological groups. Such a spectrum of families in populations with Scabiosa isetensis and ecological and biomorphic composition is a vivid indicator of the degree of habitat heterogeneity. Analysis of Jaccard's similarity indices showed similarity in species composition between populations 4 and 5; 1 and 2; 3 and 6, which is explained by similar habitat conditions. All studied populations are characterized by a single type of ontogenetic spectrum - left-handed type with predominance of juvenile individuals, i.e. populations with Scabiosa isetensis are young, developing, and suitable for practical use.

Ptačí diverzita v historickém zámeckém parku – implikace pro ochranu biodiverzity v hospodářských lesích

Long-term trends of abundance and diversity of forest birds have been very stable over past decades in European managed forests. It can be caused by high heterogeneity on habitat scale. In European cultural landscapes, there is another habitat very similar to managed forests, and that is a historic manor park. The parks can even show higher bird diversity than managed forests. However, there is an evident knowledge gap related to long-term changes of bird abundance and diversity in the habitats of manor parks. In this study we observed long-term changes of bird community in the historic manor park Čechy pod Kosířem (Czech Republic) using comparison of bird territory mapping in 2022–2023 with older bird studies in this locality. We gained an overview of bird community changes in the manor park for the period of 1997–2023. Results show that the bird community in historic manor park was remarkably unvarying in abundance and diversity. Historic manor parks can be considered as important refuges for forest bird diversity in cultural landscapes. We discuss the research implications for conserving bird diversity in managed forests especially in connection with large old trees preservation providing heterogeneity of nest habitats.

To breed or not to breed: Territory occupancy is predicted by reproductive performance and habitat heterogeneity.

Species life history and anthropogenic influence are important drivers of population performance and viability in human-dominated ecosystems. How these factors affect habitat selection and occupancy in long-lived species is an important topic for their conservation. Long-term datasets are needed for establishing the underlying drivers of this process. In this 22 year-long study, we conducted annual surveys of Bonelli's eagle in the east of the Iberian Peninsula. During this period, 42.8% of the known territories remained unoccupied. Territories with a higher likelihood of raising two chicks over time were stable, evidenced by a lower coefficient of variation in productivity, and were more likely to remain occupied. Moreover, territories with lower habitat diversity, dominated by coniferous forest or agricultural fields, and those located further away from the coast and at higher altitudes showed lower rates of occupancy (i.e., unoccupied >3 consecutive years). To validate these associations, we monitored space use of 22 individuals equipped with Global Positioning System/Global System for Mobile (GPS/GSM) transmitters, which confirmed that eagles selected for open habitats (mainly scrublands and transitional woodland-scrubs) intermixed with forest areas within their home ranges. In contrast, individuals avoided areas dominated by agricultural, urban, and continuous forests for breeding in line with the observations for unoccupied territories. Our results highlight the important interplay between natural and anthropogenic factors, which also have important implications for other raptor species. Preservation of the most productive territories and the re-occupancy of unoccupied territories along with reducing threats in the preferred habitats are fundamental actions that should be taken immediately to sustain viable populations. Potential management actions include enhancing natural prey density through habitat restoration and conservation, mitigating threats and reducing mortality risks due to power lines, fences, poisoning, and maintaining habitat heterogeneity important to eagles' hunting activities.

Characteristics of Phytoplankton Community Structure in Lakes of Wetlands Dominated by Different Aquatic Plants and Its Driving Factors

In wetland ecosystems, small shallow lakes are critical transition zones of land and water, which are usually dominated by aquatic plants with different growth forms. However, the differences and key influencing factors of phytoplankton communities in shallow lakes dominated by different aquatic plants are unclear. On this basis, nine surveys were conducted at five sampling sites of three lakes in Zhangye National Wetland Park from June to November in 2022, which were respectively dominated by the emergent Phragmites australis （LL）, the submerged Potamogeton perfoliatus （CL）, and the floating-leaved Nymphaea tetragona （SL）. During the study period, the three lakes showed obvious habitat differences. A total of 237 species of phytoplankton in seven phyla and 93 genera were identified in the three lakes, including 189 species, 151 species, and 147 species in the LL, CL, and SL lakes, respectively. Among them, Ulnaria acus, Scenedesmus quadricauda, Achnanthidium minutissimum, Nitzschia stagnorum, Navicula radiosa, and Gymnodinium aeruginosum were shared dominant species of all three lakes, indicating that they had strong environmental adaptability, whereas Navicula lanceolala, Encyonopsis cesatii, and Eunotia diodon and Cymbella aequalis were only dominant in the CL, LL, and SL lakes, respectively. Simultaneously, these dominant algae appeared with obviously distinct statuses of niche width, niche overlap, and interspecific correlation among the three lakes. Using principal coordinate analysis （PCoA） and permutational multivariate analysis of variance （PERMANOVA）, significant differences were found in algal community composition among the three lakes （P<0.001）. Multiple regression on （dis）similarity matrices analysis （MRM） showed that the heterogeneity of phytoplankton communities among the three lakes was positively affected by NO3--N and pH and negatively affected by dissolved oxygen （DO） and was closely positively correlated with the abundance of six dominant species, namely, S. quadricauda, U. acus, N. stagnorum, Pseudoanabaena sp., Merismopedia punctata, and A. minutissimum. These results indicate that aquatic plants with different growth types could affect the composition, structure, and stability of phytoplankton communities in the same habitat with them by shaping their habitat heterogeneity. Therefore, selecting specific growth types of aquatic plants for aquatic ecosystem restoration in wetland construction and management will be conducive to regulate the state of water habitat and phytoplankton community structure effectively.

Hydrogeomorphic response of steep streams following severe wildfire in the Western cascades, Oregon

AbstractSevere wildfire may alter steep mountain streams by increasing peak discharges, elevating sediment and wood inputs into channels, and increasing susceptibility to landslides and debris flows. In the Pacific Northwest, where mean annual precipitation is high and mean fire‐return intervals range from decades to centuries, understanding of steep stream response to fire is limited. We evaluate the hydrologic and geomorphic response of ~100‐m‐long steep stream reaches to the large‐scale and severe 2020 fires in the Western Cascade Range, Oregon. In the two runoff seasons after the fires, peak flows in burned reaches were below the 2‐year recurrence interval flood, a level sufficient to mobilize the median grain size of bed material, but not large enough to mobilize coarser material and reorganize channel morphology. Sediment inputs to study streams consisted of two road‐fill failure landslides, slumps, sheetwash, and minor bank erosion; precipitation thresholds to trigger debris flows were not exceeded in our sites. There was a 50% increase in the number of large wood pieces in burned reaches after the fires. Changes in fluxes of water, sediment, and wood induced shifts in the balance of sediment supply to transport capacity, initiating a sequence of sediment aggradation and bed‐material fining followed by erosion and bed‐material coarsening. Gross channel form showed resilience to change, and an unburned reference reach exhibited little morphologic change. Post‐fire recruitment of large wood will likely have long‐term implications for channel morphology and habitat heterogeneity. Below‐average precipitation during the study period, combined with an absence of extreme precipitation events, was an important control on channel responses. Climate change may have a complex effect on stream response to wildfire by increasing the propensity for both drought and extreme rain events and by altering vegetation recovery patterns.

Oyster reefs as habitat for aquatic macrofauna in a Gulf of Mexico estuary: biotic complexity at spatial, ecological, and demographic scales

Oysters are important marine foundation species across the world, particularly in estuaries of the Gulf of Mexico. One important function of oysters in estuaries is the provision of 3-dimensional habitat that is used by a wide range of species. In this study, the biotic diversity of mid-bay intertidal oyster reefs found in a Gulf of Mexico estuary was examined at nested ecological and demographic scales. Fishery-independent data collections made in East Matagorda Bay, Texas, USA, were used to compare community structure and diversity at mid-bay reefs to undifferentiated shoreline habitats. Despite similar diversity metrics, there were differences in community structure that were driven by differences in spatial habitat use by several common species. Below the community scale, demographic differences in spotted seatrout Cynoscion nebulosus habitat use were observed, with smaller and younger individuals found along reefs, and larger and older individuals found along shorelines. This finding was more pronounced for male spotted seatrout in the spring. The observed spatial habitat use patterns at nested ecological scales (community, inter-species, intra-species) highlight the importance of oyster reefs for maintaining diversity in Gulf of Mexico estuaries, and more broadly support the notion that heterogeneity in localized habitats drives biotic diversity at the estuary scale. Conservation of oyster reefs as critical habitat should be considered along with conservation of oysters themselves when balancing the ecological value of oysters against the commercial value of oyster fisheries.