Heterogeneity In Species Composition Research Articles

Correlation between Woody Species and Environmental Variables in a Tropical Forest in Central Laos

The tropical forest biome serves as a significant focal point for conservation endeavors. However, understanding the variations in woody plant composition and the underlying driving factors remains limited. The vegetation gradient within Phou Khao Khouay (PKK) National Park in central Laos presents an intriguing environmental model for investigating these patterns. This study, conducted within PKK National Park, aims to classify woody plant communities of three different forest types: mixed deciduous forest (MDF), dry evergreen forest (DEF), and mixed coniferous forest (MCF), utilizing both the phytosociology approach and multivariate analysis. Data from 32 permanent plots (each measuring 50 m × 50 m) were analyzed, revealing 5,477 tree individuals with a diameter at breast height (DBH) ≥ 5 cm, representing 194 woody species from 64 families and 133 genera. The results indicate significant diversity at the family and genus levels, identifying four distinct plant communities and 44 indicator species based on Tichy and Chytry's phi coefficient method. Stability characterizes the MCF forest type, while the stands of DEF and MDF exhibit differentiation into three communities each. Notably, high heterogeneity in species composition and environmental conditions is evident, with elevation and soil nutrient levels (specifically total phosphorus and total potassium) emerging as primary influencers on species coexistence. The study also highlights correlations between woody plant species composition and topographic and soil variables. These findings underscore the importance of identifying microhabitats conducive to growing and conserving woody plant species within PKK National Park for future research and conservation efforts.

An ecological and evolutionary approach to arboreal communities under different environmental stress conditions

Biodiversity distribution patterns and the ecological processes underlying them reflect how organisms respond to abiotic and biotic factors that interact across both space and time. In this study, we aimed to test the hypothesis that small-scale environmental variations shape ecological and phylogenetic patterns in arboreal communities through environmental filters created by the specific conditions of each environment examined. We investigated a mosaic of Atlantic forest environments, analyzing species composition, community dynamics, and phylogenetic relationships among the various environments. This approach provided valuable insight into how environmental factors influence the ecological differentiation of these communities. Variations in conditions and resources produced environmental filters that resulted in significant small-scale heterogeneity in species composition, community dynamics, and evolutionary relationships among the environments. By considering the dynamic interations between biotic and abiotic factors, we conclude that the prevailing environmental conditions at these sites play a crucial role in shaping the behavior and distribution of the species that inhabit them.

Improving restoration outcomes of boreal Sphagnum-dominated peatlands after peat-extraction: The key role of phosphorus fertilization

Fertilization is a common and effective restoration practice for some ecosystems. However, there are still knowledge gaps about the long-term effectiveness and impact of phosphorus fertilization during the restoration of degraded boreal Sphagnum peatlands using the Moss Layer Transfer Technique. Data gathered from 114 peatland sectors restored 1 to 25 years ago, encompassing around 2900 surveyed plots in Eastern Canada, were analyzed to investigate the influence of fertilization on plant re-establishment (cover, height, and aboveground biomass accumulation) and community composition. Fertilization with a low phosphorus dosage (1.64 g P m−2) of granular phosphate rock (P2O5; NPK 0–13-0) proved to accelerate peatland vegetation recovery by favoring a shift in plant community composition towards a Sphagnum dominance. This shift was encouraged by the fast colonization of Polytrichum strictum after fertilization, a nurse plant that stabilizes the peat substrate and facilitates the subsequent establishment of Sphagnum. Phosphorus fertilization increased by 42 % Sphagnum cover 25-year post-restoration and increased approximately by 15 % aboveground biomass accumulation 20-year post-restoration. Conversely, without fertilization, the success of restoration and long-term vegetation trajectories were uncertain. Phosphorus fertilization led to an increase in plant richness in the first 5 to 10 years after restoration and enhanced spatial heterogeneity in species composition throughout the later stages of restoration (20–25 years), suggesting that fertilization may foster dynamic, diverse plant communities. This study emphasizes fertilization's key role in restoring boreal Sphagnum peatland plant communities, especially in areas prone to episodes of freeze-thaw cycles, strongly advocating for the mandatory inclusion of phosphorus fertilization in the restoration process.

Alpha and beta diversity jointly drive the aboveground biomass in temperate and tropical forests.

Changes in biodiversity often affect ecosystem functioning. However, most previous biodiversity and ecosystem functioning (BEF) studies have generally been limited to very small spatial grains. Thus, knowledge regarding the biodiversity-ecosystem functioning relationships across spatial scales is lacking. Moreover, the multiscale nature of biodiversity, and specifically β diversity (i.e., spatial heterogeneity in species composition) was still largely missing in BEF studies. Here, using the vegetation and functional trait data collected from four 6-ha forest dynamics plots (FDPs) in temperate and tropical forests in China, we examine the scale-dependent relationships between tree diversity and the aboveground biomass (AGB), as well as the roles of species spatial heterogeneity in determining the AGB. In tropical forests, the effect of species richness on AGB decreased with spatial grains, while functional dominance played a stronger role at larger spatial grains. In temperate forests, positive relationship between diversity and AGB occurred at all spatial grains, especially on smaller scales. In both temperate and tropical forests, β diversity was positively correlated with AGB, but weaker than α diversity in determining AGB. Overall, complementarity and selection hypothesis play dominant role in determining AGB in temperate and tropical forests, respectively. The roles of these underlying mechanisms are more pronounced with increasing spatial scales. β diversity, a hitherto underexplored facet of biodiversity, is likely to increase ecosystem functions by species spatial turnover and should not be neglected in BEF explorations. Our findings have practical implications for forest management and demonstrate that biotic heterogeneity plays an important positive role in ecosystem functioning.

Current knowledge concerning distribution of freshwater planktonic, littoral and benthic Rotifera and microcrustacea (Cladocera, Copepoda and Ostracoda) in Central America and the Caribbean

Central America and the Caribbean, at the northern limit of the Neotropical region, is made up of a narrow strip of land and numerous islands, with a complex geological history, represents an important biogeographic connection between North and South America and contains diverse freshwater environments, including high mountain and lowlands lakes and wetlands. We examined literature reports and databases for freshwater planktonic, benthic and littoral Rotifera and microcrustacea distribution in the area in order to update, unify and summarize disparate information that has accumulated since Collado et al.’s initial contribution in 1984 that listed 369 specific and infraspecific taxa. We used the most common databases and keywords to locate papers on Rotifera, Cladocera, Ostracoda and Copepoda and found 457 new records from more than 200 study sites that list 92 genera and 782 species, as well as over 30 infraspecific taxa, for the region. These included 84%, 53%, 37% and 21% respectively, of known neotropical species of these groups. Analysis using the Sorensen-Dice Similarity Index showed high heterogeneity in species composition for the area and hierarchical clustering suggests three groups for the Caribbean islands. Lack of resources has hindered the formal publication of research. We conclude that a collaborative effort is needed to produce scientists capable of combining taxonomic information with ecological studies to enhance understanding of anthropogenic impacts on water resources.

Diversity, Structural, and Regeneration Analysis of Woody Species in the Afromontane Dry Forest of Harego, Northeastern Ethiopia

The study was conducted in the Harego dry Afromontane forest, Northeastern Ethiopia, to analyze woody species composition, diversity, structure, and regeneration status. To collect the vegetation data, a total of 67 sample plots measuring 400 m 2 20 m × 20 m were laid systematically. Species identity, abundance, height, and diameter at breast height (DBH) were recorded for each sample plot. Diversity, structural, and regeneration status were analyzed for the forest. A total of 50 woody species representing 35 families and 44 genera were identified and recorded. According to the IUCN Red List Category, Rhus glutinosa A. Rich and Prunus africana (Hook.f.) Kalkm. are vulnerable species. Fabaceae was the dominant family, and of the total species, 27 were shrubs, 19 were trees, and 4 were climbers. The species accumulation curve indicates that the majority of plant species in the study area were captured by our sampling efforts. The values of true Shannon (N1 = 17) and true Simpson (N2 = 11) indicate that species in the Harego forest are more or less evenly distributed. The abundance-frequency ratio of all woody species (WI = >0.05) indicates the heterogeneity of species composition. The total density and basal area were 4400 stems ha−1 and 9.66 m2 ha−1, respectively. The majority of the species fallen into the lower IVI classes. The diameter and height class distribution revealed an inverted J-shape. The increase in population demand and disturbance shows a high variation in stand structure and hampered natural regeneration, which needs immediate conservation actions.

Habitat filtering and inferred dispersal ability condition across‐scale species turnover and rarity in Macaronesian island spider assemblages

AbstractAimHabitat diversity has been linked to the diversity and structure of island communities, however, little is known about patterns and processes within habitats. Here we aim to determine the contributions of habitat type and inferred dispersal frequency to the differences in taxonomic structure between assemblages in the same island habitat.LocationThe Macaronesian archipelagos (Azores, Madeira, the Canary Islands and Cabo Verde).TaxonSpiders (Araneae).MethodsWe established forest and dry habitat sites (each with five plots) on two islands per archipelago. We collected spiders using standardised sampling protocols. We tested the differences in beta diversity separately for each habitat and for each inferred category of ballooning (an aerial dispersal strategy) frequency across geographic scales through nested non‐parametric permutational multivariate analyses of variance. We then tested whether ballooning and habitat influenced heterogeneity in species composition (dispersion in beta diversity) in the two habitat types. We analysed the effects of habitat and ballooning on species abundance distribution (SAD) and rarity by fitting Gambin models and evaluating the contribution of ballooning categories to SAD.ResultsCommunities of the same archipelago and habitat were taxonomically more similar, and beta diversity increased with geographic scale, being greater in dry habitats. There was greater species replacement among assemblages in dry habitats than in forests, with greater differences for rare ballooners. There were no differences in SAD between habitats although dry habitat sites seemed to harbour more species with low abundances (rare species) than forests.Main conclusionsHabitat type does not only condition the differences between spider assemblages of the same habitat but also the scale at which they occur. These differences may be determined by the heterogeneity in the physical structure of each habitat as well as how much this structure facilitates aerial dispersal (ballooning), and should be considered in theories/hypotheses on island community assembly as well as in conservation strategies.

Plant\u2013plant interactions and local patterns of diversity from semi-arid to subalpine Mediterranean plant communities

An understanding of the diversity spatial organization in plant communities provides essential information for management and conservation planning. In this study we investigated, using a multi-species approach, how plant–plant interactions determine the local structure and composition of diversity in a set of Mediterranean plant communities, ranging from semi-arid to subalpine habitats. Specifically, we evaluated the spatial pattern of diversity (i.e., diversity aggregation or segregation) in the local neighborhood of perennial plant species using the ISAR (individual species–area relationship) method. We also assessed the local pattern of beta-diversity (i.e., the spatial heterogeneity in species composition among local assemblages), including the contribution of species turnover (i.e., species replacement) and nestedness (i.e., differences in species richness) to the overall local beta-diversity. Our results showed that local diversity segregation decreased in the less productive plant communities. Also, we found that graminoids largely acted as diversity segregators, while forbs showed more diverse neighborhoods than expected in less productive study sites. Interestingly, not all shrub and dwarf shrub species aggregated diversity in their surroundings. Finally, an increase in nestedness was associated with less segregated diversity patterns in the local neighborhood of shrub species, underlining their role in creating diversity islands in less productive environmental conditions. Our results provide further insights into the effect of plant–plant interactions in shaping the structure and composition of diversity in Mediterranean plant communities, and highlight the species and groups of species that management and conservation strategies should focus on in order to prevent a loss of biodiversity.

An increasing role of pyrethroid-resistant Anopheles funestus in malaria transmission in the Lake Zone, Tanzania

Anopheles funestus is playing an increasing role in malaria transmission in parts of sub-Saharan Africa, where An. gambiae s.s. has been effectively controlled by long-lasting insecticidal nets. We investigated vector population bionomics, insecticide resistance and malaria transmission dynamics in 86 study clusters in North-West Tanzania. An. funestus s.l. represented 94.5% (4740/5016) of all vectors and was responsible for the majority of malaria transmission (96.5%), with a sporozoite rate of 3.4% and average monthly entomological inoculation rate (EIR) of 4.57 per house. Micro-geographical heterogeneity in species composition, abundance and transmission was observed across the study district in relation to key ecological differences between northern and southern clusters, with significantly higher densities, proportions and EIR of An. funestus s.l. collected from the South. An. gambiae s.l. (5.5%) density, principally An. arabiensis (81.1%) and An. gambiae s.s. (18.9%), was much lower and closely correlated with seasonal rainfall. Both An. funestus s.l. and An. gambiae s.l. were similarly resistant to alpha-cypermethrin and permethrin. Overexpression of CYP9K1, CYP6P3, CYP6P4 and CYP6M2 and high L1014S-kdr mutation frequency were detected in An. gambiae s.s. populations. Study findings highlight the urgent need for novel vector control tools to tackle persistent malaria transmission in the Lake Region of Tanzania.

Disturbances by the European ground squirrel enhance diversity and spatial heterogeneity of plant communities in temperate grassland

Fossorial rodents are recognized as diversity drivers in grassland ecosystems and are therefore considered ecosystem engineers and keystone species. However, there is a lack of evidence regarding this function for species in temperate grasslands, especially one of the most threatened, the European ground squirrel. We examined the effect of the European ground squirrel on plant species composition and diversity along the disturbance gradient mediated by their different population density and subsequently different disturbance intensity. We evaluated the effect of ground squirrel disturbance on plant diversity patterns in two plant communities with different species richness to determine whether the same pattern exists in contrasting habitats. In each plant community, we established transect of 25 × 250 m composed of 10 quadrats with different disturbance intensities of the ground squirrels. Vascular plant species were recorded in 320 plots of 1 m2. The distribution of individual species along the ground squirrel-mediated disturbance gradient was analysed using redundancy analysis. Diversity measures were calculated and modelled as a function of disturbances using generalized additive models. We observed significant compositional changes in plant communities accompanied by a reduction in dominant graminoid cover and a non-decreasing trend in forb cover along the disturbance gradient in both types of communities. We found that increasing disturbance activity leads to an increase in diversity at coarse spatial scale (625 m2) and spatial heterogeneity in species composition of both species-poor and species-rich plant community. The fine-scale (1 m2) diversity increased significantly only in species-poor community. Our results demonstrate that the European ground squirrel can be deservedly labelled as an important ecosystem engineer and keystone species promoting the diversity and heterogeneity of European temperate grasslands.

Conservation status of Mediterranean coastal dune habitats: anthropogenic disturbance may hamper habitat assignment

Coastal dunes are rich in habitats with a high heterogeneity in species composition. Though widely recognized as very fragile and dynamic ecosystems, they are systematically overexploited. In addition, mismanagement contributes making these habitats highly endangered, especially in the Mediterranean area. In this study, an impoverished dune system was used to investigate whether the lack of indicator species, including characteristic, main diagnostic, alien and non-typical, could mislead habitat assignment. Coastal dune plant communities used in this study are embedded into a high anthropogenic pressure territory, primarily due to the vicinity to a city and by hosting bathing facilities. A cluster analysis based on 49 vegetation plots (releves) was performed in order to assign dune vegetation units to EU habitats (92/43/EEC Habitat Directive) and corresponding phytosociological units. Eight habitat types were classified and two of them were of priority importance. Twelve plant communities belonging to eight different phytosociological classes were recognized. The plant cover value of characteristic, main diagnostic, alien and non-typical plant species, was used to assess the conservation status of each habitat type. Despite the presence of well-preserved plant community, almost all habitats were in unfavourable conservation status. Furthermore, a floristic impoverishment and a zonation interruption on the stabilized dunes were found. This study underlines the difficulty to identify typical coastal dune plant communities and associated habitats when anthropogenic disturbance dramatically changes the environmental conditions. Specific conservation and management actions for the sustainable maintenance of these endangered habitats are suggested.

Conservation of the Mediterranean coastal pine woodlands: How can management support biodiversity?

Forest management decisions may have unintentional effects on what they were originally not designed for, including effects on woodland species and communities. In protected areas of coastal dune woodlands, some sites are fenced as a part of forestry management. In this study, we hypothesised that different states of disturbance (disturbed vs non-disturbed) created by fencing generate unintentional heterogeneity in species composition (and possibly richness) in plant communities and soil biota. We surveyed vascular plants, oribatid mites and soil properties in fenced and nearby non-fenced places in protected coastal pine woodlands in Italy. The fenced areas were undisturbed for at least 30 years, whereas the non-fenced areas were subjected to thinning and trampling. Effects of fencing on community composition and soil properties were assessed by (distance based) redundancy analysis. Congruence between plant and mite community composition in response to fencing was tested using a series of (partial) Mantel tests. Finally, linear mixed-effects models were used to study species richness. Both plant and mite community composition showed a significant congruent response to fencing. Species richness of plants decreased due to fencing, while that of mites was unaffected. We conclude that the fencing of small areas creates biotic heterogeneity and increases beta diversity in the Mediterranean coastal woodlands. Therefore, we support the use of fencing as a relatively cheap and effective method of conservation management for maintaining the biodiversity of both above- and belowground communities in the coastal pine woodlands of the Mediterranean area.

Modelling spatial biodiversity in the world’s largest mangrove ecosystem—The Bangladesh Sundarbans: A baseline for conservation

AbstractAimMangrove forests are among the most threatened and rapidly vanishing, but poorly understood ecosystems. We aim to uncover the variables driving mangrove biodiversity and produce baseline biodiversity maps for the Sundarbans world heritage site—the Earth's largest contiguous mangrove ecosystem.LocationThe Bangladesh Sundarbans, South Asia.MethodsWe collected species abundance, environmental and disturbance data from 110 permanent sample plots (PSPs) covering the entire Bangladesh Sundarbans (6,017 km2). We applied generalized additive models to determine the key variables shaping the spatial distributions of mangrove diversity and community composition. Biodiversity maps were constructed using covariate‐driven habitat models, and their predictive performances were compared with covariate‐free (i.e., direct interpolation) approaches to see whether the inclusion of habitat variables bolster spatial predictions of biodiversity or whether we can rely on direct interpolation approaches when environmental data are not available.ResultsHistorical forest exploitation, disease, siltation and soil alkalinity were the key stressors causing loss of alpha and gamma diversity in mangrove communities. Both alpha and gamma diversity increased along the downstream‐to‐upstream and riverbank‐to‐forest interior gradients. Mangrove communities subjected to intensive past tree harvesting, disease outbreaks and siltation were more homogeneous in species composition (beta diversity). In contrast, heterogeneity in species composition increased along decreasing salinity and downstream‐to‐upstream gradients. We find that the surviving biodiversity hotspots (comprising many globally endangered tree species) are located outside the established protected area network and hence open to human exploitation. We therefore suggest bringing them immediately under protected area management.Main conclusionsWe provide the first habitat‐based modelling and mapping of alpha, beta and gamma diversity in threatened mangrove communities. In general, habitat‐based models showed better predictive ability than the covariate‐free approach. Nevertheless, the small margin of differences between the approaches demonstrates the utility of direct interpolation approaches when environmental data are unavailable.

Spatial heterogeneity in species composition constrains plant community responses to herbivory and fertilisation.

Environmental change can result in substantial shifts in community composition. The associated immigration and extinction events are likely constrained by the spatial distribution of species. Still, studies on environmental change typically quantify biotic responses at single spatial (time series within a single plot) or temporal (spatial beta diversity at single time points) scales, ignoring their potential interdependence. Here, we use data from a global network of grassland experiments to determine how turnover responses to two major forms of environmental change - fertilisation and herbivore loss - are affected by species pool size and spatial compositional heterogeneity. Fertilisation led to higher rates of local extinction, whereas turnover in herbivore exclusion plots was driven by species replacement. Overall, sites with more spatially heterogeneous composition showed significantly higher rates of annual turnover, independent of species pool size and treatment. Taking into account spatial biodiversity aspects will therefore improve our understanding of consequences of global and anthropogenic change on community dynamics.

Waterbird community composition in relation to lake physical traits and wetland limnological conditions in the Amazon basin

The mechanisms governing assemblages and the maintenance of biodiversity in tropical environments remain disputed. Two hypotheses were tested for waterbird communities in the Amazonian wetlands: (1) waterbird richness and gradients in species composition differ in Amazonian white- and black-water lakes, and are influenced by variation in lake-to-lake differences in characteristics including area, perimeter, shape, and isolation; (2) waterbird assemblages are also influenced by neighboring water-body richness (rivers, channels, ponds, and other lakes) and location of lakes in the wetlands in relation to the tributary rivers. Bird surveys were conducted using a boat in 264 lakes stretching over 1,000 km of Amazon River floodplains. The hypotheses were tested using multivariate ordination analysis, followed by multiple linear models, to evaluate how bird richness (number of species) and species composition (which species) are affected by abiotic lake characteristics. At a local scale, lake perimeter, area, and shape affected local heterogeneity in species composition of the bird community, whereas at larger scales differences among sites in water-body richness and black- and white-water types were associated with variation in waterbird richness. The patterns found indicate that lake limnological attributes influence local heterogeneity in waterbird communities within Amazonian floodplains.

¿Blanco, negro o escala de grises? Determinación de la contribución relativa del nicho ecológico y la teoría neutral en los ensambles de especies

According to the niche theory, species assemblies should reflect biotic and abiotic local conditions. In turn, the neutral theory of biodiversity stands that species are equivalent and that local species assembly is the product of colonization and extinction rates. After some years of debate, nowadays, ecologists agree that purely niche or neutral assemblies rarely occur in nature and, in turn, that the rule are assemblies somewhere in the middle. A niche assembly is the product of interspecific interactions or environmental forcing, while a neutral assembly is derived from intrinsic population dynamics (e.g., colonization and extinction rates). The beta-diversity concept (it has various definitions, but all of them share the idea of a link between local [alpha] and regional [gamma] diversity, and, thus, refers to the heterogeneity in species composition between places or times) has become particularly popular during the last decade. It is used to analyze a great variety of systems in different ways. In particular, it gained attention as a tool to differentiate niche- vs neutral-based species assembly. This could be easily addressed using ad hoc neutral models. A pure neutral assembly should exhibit a variability in species composition similar to that expected by randomly selecting species from the regional pool (gamma diversity) for each sample (alpha diversity). The more deviant from the variability expected by chance, the more niche-based assembly. We have greatly expanded our knowledge of the factors that promote one or the other type of assembly. However, there is still much more to elucidate, like how neutral vs. niche assembly is influenced by the interaction between factors, spatio-temporal relationships or if there are scale-dependent variations. In this review, we analyze the potential uses and methodologies associated with this emerging topic in community ecology and discuss some related and interesting scientific questions that remain unanswered. https://doi.org/10.25260/EA.18.28.1.0.622

Temporal heterogeneity increases with spatial heterogeneity in ecological communities.

Heterogeneity is increasingly recognized as a foundational characteristic of ecological systems. Under global change, understanding temporal community heterogeneity is necessary for predicting the stability of ecosystem functions and services. Indeed, spatial heterogeneity is commonly used in alternative stable state theory as a predictor of temporal heterogeneity and therefore an early indicator of regime shifts. To evaluate whether spatial heterogeneity in species composition is predictive of temporal heterogeneity in ecological communities, we analyzed 68 community data sets spanning freshwater and terrestrial systems where measures of species abundance were replicated over space and time. Of the 68 data sets, 55 (81%) had a weak to strongly positive relationship between spatial and temporal heterogeneity, while in the remaining communities the relationship was weak to strongly negative (19%). Based on a mixed model analysis, we found a significant but weak overall positive relationship between spatial and temporal heterogeneity across all data sets combined, and within aquatic and terrestrial data sets separately. In addition, lifespan and successional stage were negatively and positively related to temporal heterogeneity, respectively. We conclude that spatial heterogeneity may be a predictor of temporal heterogeneity in ecological communities, and that this relationship may be a general property of many terrestrial and aquatic communities.

Non‐interacting impacts of fertilization and habitat area on plant diversity via contrasting assembly mechanisms

AbstractAimThe local‐ and regional‐based forms of anthropogenic change reducing grassland diversity are generally identified, but these scale‐dependent processes tend to co‐occur with unclear interactive effects. Here, we explicitly test how common local and regional perturbations simultaneously affect plant alpha and beta diversity in a multiyear community assembly experiment using fragments of grassland habitat of various sizes. We hypothesized that local disturbances and decreasing patch size would interact, suppressing local diversity while homogenizing composition among patches.LocationNorth America.MethodsWe conducted a three‐year grassland assembly experiment, factorially manipulating local perturbation (nitrogen addition and mowing) and patch area for 36 patches over 13 ha. We quantified the individual and interactive effects of these local and regional factors on plant alpha and beta diversity within (quadrat scale) and among patches (patch scale). We also used a null model approach to disentangle between stochastic‐ and niche‐based assembly mechanisms.ResultsWe detected a gradient of assembly outcomes driven by two non‐interacting factors—the effects of N fertilization on alpha (negative) and beta (positive) diversity regardless of spatial scale and the scale‐dependant effect of increasing patch size on alpha (positive) and beta (positive) diversity. These effects unfolded over time, with the constraints on richness and composition shifting from dispersal‐based during the first sampling year to perturbation‐and size‐based factors at year two and three. Fertilization effects were driven by a mixture of deterministic (i.e., selection at the species level) and stochastic (i.e., random extinctions) processes resulting in a decline in local richness but an increase in spatial heterogeneity in species composition. Area appeared to influence alpha diversity mainly via stochastic “sampling effect”—larger patches represented a larger sample of the regional pool. Niche‐based processes, however, led to convergence in beta diversity among smaller patches driving a positive overall effect of area on beta diversity.Main conclusionOur results illustrate how diversity regulation in contemporary grasslands can be simultaneously shaped by local and regional factors acting additively but via contrasting assembly mechanisms that operate at different spatial and temporal scales.

The Structural and Functional Capacity of Ruminal and Cecal Microbiota in Growing Cattle Was Unaffected by Dietary Supplementation of Linseed Oil and Nitrate.

Microorganisms in the digestive tract of ruminants differ in their functionality and ability to use feed constituents. While cecal microbiota play an important role in post-rumen fermentation of residual substrates undigested in the rumen, limited knowledge exists regarding its structure and function. In this trial we investigated the effect of dietary supplementation with linseed oil and nitrate on methane emissions and on the structure of ruminal and cecal microbiota of growing bulls. Animals were allocated to either a CTL (control) or LINNIT (CTL supplemented with 1.9% linseed and 1.0% nitrates) diet. Methane emissions were measured using the GreenFeed system. Microbial diversity was assessed using amplicon sequencing of microbial genomic DNA. Additionally, total RNA was extracted from ruminal contents and functional mcrA and mtt genes were targeted in amplicon sequencing approach to explore the diversity of functional gene expression in methanogens. LINNIT had no effect on methane yield (g/kg DMI) even though it decreased methane production by 9% (g/day; P < 0.05). Methanobrevibacter- and Methanomassiliicoccaceae-related OTUs were more abundant in cecum (72 and 24%) compared to rumen (60 and 11%) irrespective of the diet (P < 0.05). Feeding LINNIT reduced the relative abundance of Methanomassiliicoccaceae mcrA cDNA reads in the rumen. Principal component analysis revealed significant differences in taxonomic composition and abundance of bacterial communities between rumen and cecum. Treatment decreased the relative abundance of a few Ruminococcaceae genera, without affecting global bacterial community structure. Our research confirms a high level of heterogeneity in species composition of microbial consortia in the main gastrointestinal compartments where feed is fermented in ruminants. There was a parallel between the lack of effect of LINNIT on ruminal and cecal microbial community structure and functions on one side and methane emission changes on the other. These results suggest that the sequencing strategy used here to study microbial diversity and function accurately reflected the absence of effect on methane phenotypes in bulls treated with linseed plus nitrate.

Limited effects of low-intensity forest management on ant assemblages in southwestern Amazonian forests

One important strategy to conciliate forest conservation and economic development is the use of reduced-impact logging techniques. Here we evaluated the effects of low-intensity forest management on ant assemblages and vegetation structure in a managed area in the southeast of Acre State, Brazil. Ground-dwelling and arboreal ants, and several forest-structure descriptors were sampled in nine paired areas located in control (unlogged) and logged areas in 2005, 2007 and 2009. None of the forest structure predictors were related with either the treatment or the time since logging. However, some ant assemblage’ descriptors were related with logging activities. Arboreal and ground-dwelling ant species richness was similar between unlogged and logged areas, but more ground-dwelling ant species were found in areas logged in 2005 compared with areas logged in 2009. Ground-dwelling ant assemblage composition differed between treatments (logged and unlogged) and year of logging, but species composition heterogeneity was similar between areas. Arboreal ant assemblage composition was not related with treatment and year of logging, but assemblage composition was more heterogeneous in managed areas, suggesting that species that forage on the understory vegetation may be more resilient than ground-dwelling species. The general results of functional group approach suggest that changes of species composition between control and managed areas are more related with differences in ant species occurrence than ant species richness. Selective logging had limited effect on both vegetation descriptors and ant assemblage structure, suggesting that the conciliation of impact reduction techniques with low intensity extraction seems a promising alternative for sustainable logging activity in tropical forests.