Abundance Of Dominant Species Research Articles

Mulching practices alter the bacterial-fungal community and network in favor of soil quality in a semiarid orchard system

The study aimed to investigate how mulching practices can improve soil quality by altering microbial community composition and the interrelations among its members. The experiment was conducted for 7 years (from 2012 to 2018) in an apple (Malus domestica cv. Fuji) orchard located on the Loess Plateau, China. Four treatments were applied: conventional tillage (CT), intercrop ryegrass (Lolium perenne L.) cover (RE), inter-row cornstalk mulch (CS), and black ground fabric mulch (BF). The results indicated that compared to CT treatment, all the three mulching practices significantly increased soil moisture content. The RE and CS treatments improved soil organic matter content by 11.8% and 36.5%, respectively, and CS treatment also increased available nitrogen content in soil by 42.0% compared with CT treatment. The soil environmental heterogeneity under different mulching practices shaped the microbial community structure and the dominant populations. All the mulching practices significantly increased the operational taxonomic unit (OTU) abundance and alpha diversity of fungi, and positively affected bacterial richness. Network analyses showed that the microbial structure was significantly affected by soil water and microbial biomass nitrogen. Interestingly, based on network correlation analysis among microorganisms, the BF treatment reduced competition between bacteria, whereas RE treatment increased their cooperation, however, the CS treatment not only promoted cooperation between fungi, but also increased correlations between fungi and bacteria. Finally, our results indicated that mulching practices not only increased the diversity of microorganisms and abundance of dominant species, but also promoted the interrelations among microorganisms in favor of soil quality.

Changes in Epilithic Algae Community and Its Relationship with Environmental Factors in the Meixi River, a Tributary of the Three Gorges Reservoir

To explore the relationship between the community of epilithic algae and environmental factors in tributaries of the Three Gorges Reservoir region, the epilithic algae and related environment factors were investigated from 26 sampling sites in Meixi River, a tributary of the Three Gorges Reservoir region, during flood period (August 2016), drought period (November 2016), and normal water period (March 2017). Results showed that 106 species (including varieties) belonging to 47 genera and 5 families were identified from 26 sampling sites during the three periods. Among these, 73 species belonged to 38 genera and 5 families in the flood period, 67 species belonged to 36 genera and 4 families in the drought period, and 63 species belonged to 33 genera and 4 families in the normal water period. Nineteen, 17, and 18 dominant species were identified during the flood period, drought period, and normal water period, respectively. The main dominant species were Achnanthes sp., Aphanizomenon sp., and Phormidium sp. in the flood period; Achnanthes sp., Gomphonema sp., and Microcystis sp. in the drought period; and Gomphonema sp., Nitzschia sp., and Chroococcus sp. in the normal water period. Moreover, species such as Cocconeis placentula, Achnanthes sp., Gomphonema subclavatum, G. parvulum, Navicula parva, and G. constrictum were determined to be the common dominant species during the three periods. Redundancy analysis revealed that the changes in the relative abundance of dominant species in the backwater sections were significantly related to the electrical conductivity, dissolved oxygen, pH, total phosphorus, and total nitrogen, and the relative abundance of dominant species in the natural sections was mainly related to the electrical conductivity, pH, total phosphorus, temperature, and velocity. Moreover, a different relationship with the environmental factors was determined among the three periods. However, a negative correlation between total phosphorus and the relative abundances in G. parvulum, G. constrictum, and Achnanthes sp. and a positive correlation between pH and the relative abundances in G. parvulum, G. constrictum, and Achnanthes sp. were found during the three periods. These results indicated that the differences in the hydrological regime and environmental factors in the Three Gorges Reservoir played an important role on the composition of epilithic algae community and led to a significant change in the community structure of epilithic algae.

Temporal variation in effect sizes in a long-term, split-plot field experiment.

Ecological field experiments initiate successional and evolutionary changes among resident species, yet effect sizes are often reported as if they were constants. Few ecological studies have addressed their questions through long-term, experimental approaches, and many questions remain unanswered regarding temporal patterns in ecological effect sizes. We document temporal variation in effect sizes in response to pulse and press manipulations in a long-term factorial field experiment at Nash's Field, England. The experiment comprises seven treatments applied in a split-plot design to test the single and interactive effects of herbivory by insects, molluscs, and rabbits, liming, nutrient limitation (applied as press experiments), competition (exclusion of grasses or herbs with specific herbicides), and seed limitation (pulse experiments) on plant community dynamics. The response of all vascular plant species was followed for two decades. High species richness was positively related to the minus-grass herbicide in the first decade and negatively related to both nitrogen addition and the abundance of dominant species in both decades. Many significant effects appeared quickly, but some large effects were not detected until year 15. Press experiments produced some long-lasting effects, but effect sizes changed due to both idiosyncratic "year effects" and secular trends. For pulse experiments, most effects, including positive and negative responses to herbicide application and the invasion of most of the sown species, disappeared quickly. However, some endured or grew monotonically, such as the invasion of two sown species that benefited from particular combinations of the press treatments. The fastest effects to appear were the responses from established species. Many of these responses were negative, likely resulting from reduced niche dimensionality and competitive exclusion by new dominant species. Contrarily, one of the largest community-level effects took well over a decade to appear: the natural invasion by one species, which responded to a four-way interaction between experimental treatments. The insights gained from individual effects increased with the duration of the lag before their first appearance, drawing attention to the importance of long-term, manipulative field experiments. This experiment also reinforces the point that factorial experiments are the most insightful way to explore ecological interactions.

Dominant Species Abundance, Vertical Structure and Plant Diversity Response to Nature Forest Protection in Northeastern China: Conservation Effects and Implications

The conservation of species diversity and improvement of forest structure are essential roles of the Natural Reserve Policy and the Natural Forest Protection Program (NFPP) in China. However, the long-term effects of NFPP are still not well-defined, and a natural reserve (Liangshui) and surrounding region were surveyed as a proxy of NFPP for approaching the protection effects. Our results showed that long-term conservation significantly altered the dominant species in the herb layer (80% of species), followed by shrub (58%) and tree layers (50%); there was a 1.6-8.0-fold increase in abundance in Corylus shrubs, Acer trees and Carex grass, but a 1.3–10.0-fold abundance decrease in larch trees, Athyrium herbs and Lonicera shrubs. In contrast, tree species diversity and distribution evenness increased by 31% and 23.4% in the reserve, respectively. Forest protection in the reserve also led to the forest structural alteration with the observation of larger-sized trees and shorter herbs, but relatively sparse forests (smaller tree density). Structural equation modeling manifested that the reserve directly altered forest structure, at a coefficient of 0.854, nearly two-fold higher than its impact on diversity (0.459) and dominant species (−0.445). The most affected parameters were plant size (trees and herbs) and tree density related to forest structure, tree diversity, herb richness and evenness for diversity traits, and Oxalidaceae and Rosaceae for dominant species. This study provides basic data that can be used to evaluate the impact of the nature reserve in NE China, and these findings can be used to guide the implementation of NFPP in the long-term in the future.

Spatial Sampling Grain Shapes Conclusions about Community Structure and Dynamics

Long-term monitoring is an integral part of land management and biodiversity conservation. Sampling grain, a key component of monitoring design, can impact conclusions about spatial patterns in composition, but less is known about how sampling grain influences our ability to detect temporal compositional dynamics.To evaluate how sampling grain affects conclusions about temporal dynamics, we analyzed vegetation data from permanently marked transects in a sagebrush-steppe ecosystem. Each transect was monitored for 9 y at three sampling grains: point-intercept, 15 × 15 cm sampling frame, and 60 × 60 cm sampling frame. We investigated grain-dependent patterns in diversity, functional group representation, and multivariate compositional change.Inferred community dynamics were strongly affected by sampling grain. Large grains had the greatest richness and detection frequencies for nearly all species. Almost all additional species detected at larger grains were forbs, the life form that comprises most of the species richness in this system. Mean compositional change was lower and temporal compositional change was more pronounced when based on data acquired at larger sampling grains. Small sampling grains result in undersampling, which biases measurements of community dynamics. These grains can provide reasonable estimates for coarse metrics such as the abundance of dominant species, but often fail to capture changes in nondominant species. We recommend that natural resource managers sample multiple grains based on the scales of the processes they are interested in monitoring.

Some patterns in distribution of the ground beetles (Coleoptera, Carabidae) at the agrocenoses of Ukraine

According to the habitat layers, ground beetles of agrocenoses of Ukraine were divided on three groups: preferential inhabitants of the soil (geobios), inhabitants of the surface of the soil and plant litter (stratobios) and preferential inhabitants of the plants (phytobios). Ground beetles of geobios were represented with about 20 species, from which only five species were relatively numerous. About 370 species were registered in stratobios (about 90 are dominants or subdominants). The inhabitants of the plant layer encompassed about 10 species, but most of them were rare in agrocenoses. Most spring zoophagous species of Carabidae (mainly species of the genus Poecilus) are characterized by a low level of aggregation (Ka = 0.25–0.35). A higher degree of aggregation was recorded for small species of ground beetles (Bembidion, Microlestes) and some mixophagous (Amara similata, A. aenea, Harpalus distinguendus). At summer, the higher level of aggregation was registered (Ka = 0.35–0.46), especially for summer-autumn group of ground beetles (Calathus ambiguus, C. melanocephalus, Harpalus rufipes) and some multi-seasonal species (Pterostichus melanarius). An essential factor affecting the distribution of ground beetles on the field is the density of the plants. On the plots with rare vegetation the accumulation of thermophilous and mesoxerophilous species (Poecilus crenuliger, P. koyi, P. puncticollis) was observed (significant correlation). Higher number of mesophilous and mesohygrophilous Carabidae (Bembidion properans, Poecilus cupreus, P. punctulatus) are registered on the plots with dense vegetation, especially during reproduction period. An increase in the number and diversity of the Carabidae are observed in relatively small fields (up to 50–60 ha), bordered by forest belts or natural biotops. In large fields (more than 100 ha) surrounded by similar crops, the abundance of dominant species of Carabidae was significantly decreased.

Compensatory effects stabilize the functioning of Baltic brackish and salt marsh plant communities

The variation in plant species abundances and in community composition appears to be a basic ecological trigger that determines changes in community functionality and resilience. Particularly, fluctuations in abundance of dominant species might indicate major changes in resource use and ecosystem functioning. Here we use quantitative surveys of Baltic brackish and salt marsh plant communities to infer how variability in species abundances and environmental conditions influence plant assimilation rates and whether compensatory effects in abundance mask variability in functionality. The variability in species richness and assimilation rates was negatively correlated with average soil organic matter content and moisture and positively correlated with soil pH. It was independent of the variability in soil conditions. The abundances of rare species and species of intermediate abundances increased with increasing community wide assimilation rates. Our findings indicate that the strength of compensatory mechanisms that stabilise assimilation rates in salt marsh environments heavily depend on soil conditions. In the present study sites benign soil conditions stabilized assimilation rates while more stressful conditions caused synchronous fluctuations in total abundance and assimilation.

PHYTODIVERSITY OF THE RESEARCH TERRITORY OF THE EDUCATIONAL AND SCIENTIFIC STATIONARY OF THE ODESA I. I. MECHNIKOV NATIONAL UNIVERSITY

Problem Statement and Purpose. Biological and landscape diversity is considered as the fundamental property of natural complexes, which ensures their stability and manifests itself at different levels of their hierarchy. One of the types of biodiversity is phytodiversity which is the variety of plants. The stability of geosystems directly depends on the number of species of living organisms that form a complex relationship within the supply chain and struggle for survival. The more species is the higher stability of the system. This means that in the case of loss of one species, there is a high probability that another species will assume its functions. If species are not enough the ecosystem will lose one link, resulting in an imbalance. Finally, the geosystem can be completely destroyed.The purpose of the study is the estimation of the phytodiversity of the area, which for a long time (more than 15 years) is not involved in human activity, as well as the determination of changes in the conditionally natural system in a three-year interval. The main tasks are quantitative and qualitative estimation of the species diversity of grassy plants of the geosystem, analysis of weather conditions, analysis of individual geocomponents.Data & Methods. The investigations were carried out within the area which is located on the left slope of the Labushna Valley of the southwestern exposition. The slope has a complicated profile. Its length is about 400 m, average slope is 8 °. The area is surrounded by fields of crop rotation. It is situated on the territory of the Educational and Scientific Stationary of the Odessa I. I. Mechnikov National University.The study of biodiversity of grassy plants was carried out along the 5 m transect (strips), laid from top to bottom of the slope. On transect, plant groups were distinguished by external signs. Within each group, a standard geobotanical research was carried out, during which species of plants, the abundance of each species (in %), dominant species, composition and height of plantations, projective coverage (in %) were determined. Such studies were conducted in 2015 and 2018.The time of observation is the third decade of June. Two rows of data are obtained for calculations and estimation of phytogenic diversity.Also, in the study floristic germination and index of adventitious species are calculated on the basis of the species composition. Abundance of dominant species in two years of research was estimated on the Drude scale.Results. The Stationary was organized in 1980 for to study the conditions of the forest-steppe landscapes, and the regime of excessively moist soils (wetlands, mochars), as well as their melioration. The vegetation of the territory is represented by the diversity of grasses, grass, cereal, leguminous grass and legume-cereal dry meadows, overgrown areas with a predominance of cane and various species of ascension and broadleaf elderberry-ash-oak, maple-ash-oak and birch leaf-cherryoak forests.The total cultivation of the Baltic Stationary is 55.4%. Forest areas, including peat and sloping anti-erosion plantings, occupy 21.6% of the area. The total area of conventionally natural areas which are not used for arable land and not occupied by forests and settlements is 17.49 sq. km, or 13.4% of the area.The investigated area is characterized by a high diversity of plant species. The alternation of plant groups is subject to a certain spatial pattern associated with external factors (human impact, groundwater level, weather conditions) and internal features of the area (shape and exposition of the slope, soil cover). The value of the Sierressen floristic germination (58 %) indicates a high similarity of species during the years of study, from which it can be concluded that the geosystem of the area is sustainable enough. According to the values of the index of adventitious species, the plant groups contain a significant proportion of the adventitious species (18 % in 2015 and 27 % in 2018).

Dominant Bivalve in an Exposed Sandy Beach Regulates Community Structure Through Spatial Competition

Fluctuations in abundance of dominant species can cause competitive release of resources with consequences on community structure and functioning. In the present study, changes in the intertidal macroinfauna community of an exposed sandy beach were evaluated during two contrasting periods characterized by low and high densities of the yellow clam Amarilladesma mactroides. The increase in clam abundance and biomass was associated with a significant decrease in abundance of the rest of the community. In particular, a decline was observed for the pea crab Austinixa patagoniensis, a commensal species that lives in the burrows of the shrimp Sergio mirim. Our study demonstrates that fluctuations in clam abundance lead to long-term changes in community structure, suggesting the presence of competitive interactions. The environmental stability over the two periods strengthens the hypothesis that the competition between species is crucial for shaping the ecological community. Stable isotope analysis allows discarding trophic competition as mechanism of exclusion. Image maps reveal complementary distribution of species, showing the relevance of the spatial competition, which is mediated by changes in abundance of a third species. Indeed, high densities of A. mactroides reduce the available area for the establishment of the S. mirim burrows, limiting the foraging behavior of its commensal, the pea crab. Such an interaction drives density-dependent exclusion of the pea crab from the intertidal zone following the establishment of the yellow clam population. This study illustrates that spatial competition triggered by the increase of a bed-forming species can have community-wide consequences in exposed sandy beaches.

Fish larvae as indicator species of interannual environmental variability in a subtropical transition area off the Baja California peninsula

The aim of this work was to determine if the variation patterns in the abundance of dominant species of fish larvae in the transition zone off Bahía Sebastián Vizcaíno, Mexico, could be used as indicators of interannual environmental variability, and how larval fish assemblages respond to this environmental variability during the period 1997–2013. With the 16 years of plankton data in the southern region of the California Current System, anomaly curves of larval abundance were calculated, from which the temporal abundance patterns of the dominant fish larvae of the mesopelagic, epipelagic and demersal environments were obtained. Classification and ordination analyses were carried out to obtain the larval fish assemblages as well as their relations with environmental variables (sea surface temperature, surface salinity, concentration of Chlorophyll-a and zooplanktonic volume) and climatic indexes (ONI, MEI, PDO and NPGO). Results showed a high positive correlation between the mesopelagic abundance with MEI and PDO indices, demonstrating their affinity with warm oceanic waters, while there were not statistically significant correlation between the climatic indexes and the epipelagic (Sardinops sagax and Engraulis mordax) or demersal species (Synodus lucioceps). The interannual variability of the abundance of three dominant mesopelagic species (Vinciguerria lucetia, Diogenichthys laternatus and Cyclothone signata) show that these species had a clearer response to environmental variability than epipelagic and demersal species. Trends in the abundance of mesopelagic species larvae and their high correlation values with the environmental variables used, demonstrate their potential as indicators of environmental change of the pelagic ecosystem in the transitional area off Bahía Sebastián Vizcaíno.

Spatiotemporal Dynamics of Free-Living and Particle-Associated Vibrio Communities in the Northern Chinese Marginal Seas.

Vibrio species are associated with human health and play important roles in the carbon cycle. The interest in the Vibrio ecology in marine pelagic environments has increased in recent years, and the correlations between the Vibrio community structure and various environmental factors have been demonstrated. However, the identification of planktonic Vibrio species and their relationship with particulate matter are unclear. Here, we elucidated the spatiotemporal dynamics of Vibrio diversity and in relation to environmental factors in the northern Chinese marginal seas, which feature complex and ever-changing environmental conditions. Vibrio abundance derived from quantitative PCR analysis was higher in summer (∼1.4 × 106 copies liter-1) than in winter (∼1.9 × 105 copies liter-1). Interestingly, the average amount of free-living (on a 0.22-μm-pore-size filter membrane) Vibrio was higher (∼3.89 times) than that of particle-associated Vibrio (on a 3-μm-pore-size filter membrane), making it likely that the preferential lifestyle of the planktonic Vibrio community was free living. Shifts in Vibrio community composition identified by high-throughput amplicon sequencing of the Vibrio-specific 16S rRNA gene were observed at both spatial and temporal scales, which were mainly driven by temperature, dissolved oxygen, ammonium, salinity, nitrite, and phosphate. The most prominent operational taxonomic units in summer were closely related to Vibrio campbellii and Vibrio caribbeanicus and shifted to those affiliated with Vibrio atlanticus in winter. Our study demonstrated abundant and diverse Vibrio populations in the northern Chinese marginal seas, contributing to a better understanding of their potential ecological roles in these ecosystems.IMPORTANCE The dynamics of Vibrio communities have been shown in many marine habitats that are close to land, including estuary or harbor areas. Here, we investigated the spatiotemporal dynamics of Vibrio populations in the northern Chinese marginal seas, spanning a wide spatial scale. We showed that the abundances of the Vibrio population in the present study were higher than those in most previously studied areas and that Vibrio species are more likely to adopt a free-living lifestyle. Moreover, our results expanded upon previous results by showing a clear shift in the dominant Vibrio species from summer to winter, which was mainly attributable to the reduction in the abundance of dominant species in summer. Overall, this work contributes to the understanding of the ecology of the Vibrio communities in the marginal seas.

Response of soil bacterial communities to moisture and grazing in the Tibetan alpine steppes on a small spatial scale

As the Third Pole of the world, the Tibetan Plateau provides a typical alpine grassland environment for soil bacteria with its unique frigid and arid climate. Owing to clear changes in spatial moisture and increased grazing intensity, moisture and livestock grazing have become key factors influencing the microbial communities. Accordingly, we investigated the diversity and composition of soil bacteria in a selected alpine grassland within the dual gradients of moisture and grazing using high-throughput sequencing. Our results showed that grazing changed the soil bacterial diversity and composition, whereas moisture only influenced the relative abundance of the segmental community at the small spatial scale. Species richness was found to be increased by moderate grazing compared with that by high or low-grazing intensity. The relative abundance of dominant species and β-diversity of soil bacteria both showed differences with heavy, moderate, and low grazing. Some dominant bacteria were altered with the moisture content. However, there were no significant differences according to the moisture gradient in terms of the overall bacterial β diversity and composition. These results might be taken account into the small spatial scale as well as the compensation of grazing to moisture on this scale. This work provides new insights into the soil bacterial response to moisture gradients and grazing intensity in alpine steppe habitat.

The gut microbiota heterogeneity and assembly changes associated with the IBD

Inflammatory bowel disease (IBD) is an immunologically mediated disease and may be caused by abnormal immunological response to gut microbes. Although several studies on the ecological changes associated with IBD, such as community diversities, were reported, no previous studies have investigated the changes in the spatial heterogeneity and the mechanism of community assembly of the gut microbiota associated with IBD. In the present study, we first applied the Taylor’s power law extensions to compare the community spatial heterogeneity between the gut microbial communities of the IBD patients and those of the healthy individuals. We found that the community spatial heterogeneity of gut microbiota in IBD patients is slightly lower than in the healthy individuals. This finding suggests that IBD may lower the spatial heterogeneity of gut microbiota, possibly via lowering the abundance of dominant species. We further applied the neutral theory of biodiversity to comparatively investigate the community assembly and diversity maintenance of the gut microbiota with and without IBD, and our application suggested that deterministic factors such as host immunity should be dominant forces shaping gut microbiota assembly, and diseases such as IBD may not be strong enough to change the trend set by the deterministic host factors.

Overwintering of ladybirds (Coleoptera: Coccinellidae) on Scots pine in Central Europe

We surveyed ladybirds (Coleoptera: Coccinellidae) in 10 stands of Scots pine (Pinus sylvestris), all monoculture stands 5-100 years old, in western Slovakia, Central Europe, over two successive periods, October 2013 - March 2014 and October 2014 - March 2015. The winter in each period was exceptionally mild. Ladybirds were collected from the lower branches of pine trees using beating trays and were present in 61% of the 1040 samples (one sample containing ladybirds from 20 branches, 1 m long each). In total 3965 individuals of 20 species were recorded. Non-conifer dwelling species associated with broadleaved trees or herbaceous plants prevailed (45% of species), followed by conifer specialists (40%) and generalists (15%). Although 13 species were found at least in one winter month, December, January or February, only four of them, Exochomus quadripustulatus, Coccinella septempunctata, Harmonia axyridis and Hippodamia variegata, were recorded continually during both winters. The number of species, the abundance of all ladybirds and the abundance of dominant species (E. quadripustulatus, C. septempunctata and H. axyridis) decreased from late autumn towards winter and remained lowest during this most adverse time of the year for ladybirds. Overwintering species assemblages of ladybirds changed over time and varied with age of pine stand. Our results suggest that Scots pine in Central Europe supports species rich assemblages of ladybirds from late autumn to early spring and, being widely distributed, it could be suited to winter surveying of ladybirds at large spatial scales to reveal behavioural and ecological responses of species to changing weather or different climates.

Responses of benthic foraminifera to changes of temperature and salinity: Results from a laboratory culture experiment

The effects of temperature and salinity on intertidal foraminiferal community under laboratory conditions are poorly understood. We designed a two-factor crossed experiment in which foraminiferal communities were cultured at different temperatures (6, 12, and 18°C) and salinities (15, 20, 25, and 30 psu) for 10 weeks. In total, 2616 living (stained) specimens were obtained and analyzed. Foraminiferal abundance ranged from 9 to 202 individuals/ 10 g wet weight of sediment. The highest abundance was obtained at 12°C, 25 psu and the lowest at 6°C, 15 psu. Statistical results demonstrated that temperature affected foraminiferal community more significantly than salinity. Most foraminiferal community parameters (abundance, species richness, Margalef index, and Shannon-Wiener diversity) were significantly positively correlated to temperature, but not to salinity, whereas Pielou’s evenness was significantly negatively correlated to both temperature and salinity. The interactive effect of temperature and salinity on foraminiferal abundance was significant. In addition, with increasing temperature, the species composition shifted from hyaline Rotaliida to porcellaneous Miliolida. The abundance of dominant species (e.g., Ammonia aomoriensis , A. beccarii , and Quinqueloculina seminula ) showed significant positive correlations to temperature. Our study indicated that the intertidal foraminiferal community responds sensitively and rapidly to the changes of salinity and, especially, temperature by shifting foraminiferal species composition and altering the community parameters.

Effects of trampling on intertidal mussel beds: importance of disturbance intensity

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 606:231-235 (2018) - DOI: https://doi.org/10.3354/meps12770 NOTE Effects of trampling on intertidal mussel beds: importance of disturbance intensity María M. Mendez1,2,*, Juan P. Livore1, Gregorio Bigatti1,2,3 1Laboratorio de Reproducción y Biología Integrativa de Invertebrados Marinos (IBIOMAR-CCT CONICET CENPAT), U9120ACV Puerto Madryn, Argentina 2Universidad Nacional de la Patagonia San Juan Bosco, Sede Puerto Madryn, U9120ACV Puerto Madryn, Argentina 3Universidad Espíritu Santo, 092301 Samborondón, Ecuador *Corresponding author: mendez@cenpat-conicet.gob.ar ABSTRACT: Trampling is one of the most frequent forms of human disturbance on rocky shores. This activity may directly reduce the abundance of dominant species, indirectly promote changes in the abundance of associated species and ultimately affect biological interactions. We assessed the effects of different intensities of human trampling on Brachidontes spp. mussel beds, a dominant feature on rocky intertidal flats of southwestern Atlantic coasts. We experimentally applied 6 levels of trampling intensity on a Patagonian rocky shore. Simulated trampling intensity ranged from 0 to 600 tramples per day, and plots were disturbed replicating local usage patterns (i.e. austral summer weekend recreation). By the end of the experiment, Brachidontes spp. coverage decreased as a result of increasing intensities of trampling and mostly replaced by bare rock. Even the lowest experimental intensity produced a loss of more than 40% of coverage. Changes in coverage were generally immediate and occurred after the first 2 trampling events, regardless of disturbance intensity. Our findings highlight that as few as 5 people walking on the mid-intertidal flat can produce a decline of the mussel bed cover in a specific area. Our findings also alert to the urgency of implementing effective management actions in this and other frequented areas dominated by similar habitat-forming species. KEY WORDS: Disturbance · Trampling · Mussel beds · Rocky shores · Southwestern Atlantic Full text in pdf format PreviousNextCite this article as: Mendez MM, Livore JP, Bigatti G (2018) Effects of trampling on intertidal mussel beds: importance of disturbance intensity. Mar Ecol Prog Ser 606:231-235. https://doi.org/10.3354/meps12770 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 606. Online publication date: November 15, 2018 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2018 Inter-Research.

Can late flushing trees avoid attack by moth larvae in temperate forests?

We investigated moth larvae (Lepidoptera) developing in temperate forests in Central Europe shortly after the tree budburst (the “brumata-viridana complex”). Larvae were collected in southern Slovakia in May 2015 and May 2016 from young and mature trees of late flushing Quercus cerris L. and early flushing Q. pubescens Willd. Although Q. cerris yielded fewer species (40 species) than Q. pubescens (47 species), the rarefied number of species and the Chao index suggested a similar number of species on mature trees of both oak species. Both the total number of moth larvae in assemblages and the abundance of dominant species (pests) were significantly lower on Q. cerris than Q. pubescens. The results suggest the release of Q. cerris with delayed budburst from heavy infestations by folivorous moth larvae. Knowledge obtained can be applied in silvicultural and horticultural practices aimed to protect and maintain forest, fruit, and ornamental trees.

Ecosystem multifunctionality increases with beta diversity in restored prairies.

The loss of biodiversity at local and larger scales has potentially dramatic effects on ecosystem functioning. Many studies have shown that ecosystem functioning depends on biodiversity, but the role of beta diversity, spatial variation in community composition, is less clear than that of local-scale (alpha) diversity. To test the hypothesis that beta diversity would increase ecosystem multifunctionality through variation in species functional traits, we gathered data on plant community composition, plant functional traits, and seven ecosystem functions across 29 restored prairies. We found that averaged multifunctionality (mean of seven ecosystem functions) increased with both taxonomic beta diversity and functional beta diversity. The abundance of the dominant species, big bluestem, played a more minor role, suggesting a limited role for the selection effect. Neither taxonomic nor functional alpha richness was associated with multifunctionality, though this finding may be sensitive to the identity of the functions included because alpha diversity was associated with some individual functions in opposing directions. These findings suggest that in systems structured largely by natural processes, beta diversity (a patchwork of functionally different plant communities) and dominant species abundance may be more important than alpha diversity in fostering ecosystem multifunctionality. These findings suggest the need for an increased focus on community heterogeneity to reestablish functional ecosystems during restoration.

Spatial heterogeneity and seasonal structure of physical factors and benthic species in a tropical coastal lagoon, Celestun, Yucatan Peninsula

Spatial heterogeneity is an attribute of ecosystems that plays a central role in ecological theory, as it can be an explanatory factor for numerous processes that result in recognizable spatial structure. The aims of this study were to determine the potential presence of recognizable spatial structure in the distribution and abundance of dominant benthic species and to examine whether this spatial variability is explained by habitat-specific factors. The study was performed at Celestun, a coastal lagoon with a marked horizontal salinity gradient, based upon historical data obtained seasonally during the 1998–1999 annual cycle. Sampling was carried out in the inner zone of the lagoon, which is considered the steadiest and most homogeneous zone. Physicochemical factors were recorded in order to characterize the habitat, and benthic macroinfauna were collected to assess species composition and abundance. The benthic assemblage we sampled included 23 species, dominated in terms of abundance by mollusks, two gastropods, and one bivalve. One-way ANOVA and geostatistical analysis determined that the species and measured factors were not distributed homogeneously in this zone but were instead spatially structured in the form of patches and gradients that varied over time. A generalized linear model identified the factors (water salinity, organic matter, and sand) that explained between 17% and 30% of the variance in abundance of dominant species depending on the season. These results provide important information about the ecological quality of the lagoon inner zone and the tolerance of species to environmental factors.

Impact of sheep grazing intensity on vegetation at the Arid Karoo Stocking Rate Trial after 27 years, Carnarvon, South Africa

Sustained heavy grazing is expected to result in degradation and loss of biodiversity in drylands but long-term experiments which assess the impact of management practises on biodiversity are necessary. The effects of stocking rate (SR) on vegetation composition, abundance of different plant functional groups (PFGs), abundance of dominant species, and plant diversity were investigated after 27 years at a long-term SR trial. Vegetation composition was investigated using Canonical Correspondence Analysis and General Linear Models. Stocking rate and time had significant effects on species composition. Increases over time were apparent for total plant cover, palatable shrub cover, and perennial grass cover, annual grass cover decreased over time, whereas other PFGs and rangeland condition showed no trend over time. Greater stocking rates resulted in lower total plant cover, palatable and unpalatable shrub cover, perennial grasses, and annual herbaceous species. Higher annual rainfall resulted in higher total plant cover, while greater preceding three-month rainfall benefitted annual grasses and annual herbaceous species. Plant diversity seemed unaffected by SR. Vegetation structure did not seem to be influenced by SR after 27 years. Our study confirms the slow rate at which vegetation change occurs in drylands and highlights the importance of long-term monitoring trials.