Relationship between seedling emergence and species frequency on a gradient of ground cover density in an abandoned pasture

1991 ◽  
Vol 69 (7) ◽  
pp. 1397-1401 ◽  
Author(s):  
R. J. Reader
Keyword(s):  
Community Structure ◽  
Spatial Variation ◽  
Key Words ◽  
Seedling Emergence ◽  
Ground Cover ◽  
Old Field ◽  
Community Members ◽  
Species Frequency ◽  
Close Relationship ◽  
Cover Density

Seedling emergence may be suppressed by dense ground cover causing species frequency to vary where ground cover ranges from moderate to dense. An experiment was conducted to determine how many community members showed matching patterns of variation in seedling emergence and frequency on a gradient of ground cover density in an abandoned pasture. Seedling emergence and species frequency were recorded on ridges, where ground cover was moderately dense, and in hollows, where ground cover was much denser. Eight of the 10 species examined showed ridge-hollow variation in seedling emergence and seven of the eight species showed a matching pattern of ridge-hollow variation in their frequency. When ground cover was removed experimentally, seedling emergence increased more in hollows than on ridges for all but one of the eight species. This suggests that ridge-hollow variation in seedling emergence resulted from greater suppression of seedling emergence by ground cover in hollows than on ridges. The close relationship between ridge-hollow variation in seedling emergence and species frequency in the community studied here indicates that models of spatial variation in community structure need to include spatial variation in seedling emergence as well as plant survival. Key words: ground cover, old field, seedling emergence.

Control of seedling emergence by ground cover: a potential mechanism involving seed predation

1991 ◽  
Vol 69 (9) ◽  
pp. 2084-2087 ◽  
Author(s):  
R. J. Reader
Keyword(s):  
Field Experiment ◽  
Seed Predation ◽  
Daucus Carota ◽  
Plant Biomass ◽  
Seedling Emergence ◽  
Ground Cover ◽  
Taraxacum Officinale ◽  
Potential Mechanism ◽  
Old Field ◽  
Seed Predators

The presence of ground cover (i.e., plant biomass and litter) could restrict seedling emergence by providing a habitat for seed predators. To test this hypothesis, a field experiment was conducted with three old-field forbs (Daucus carota, Centaurea nigra, Taraxacum officinale). Ground cover was either removed or left in place and sown seeds of the three forbs were either protected from predators or left unprotected. Where seeds were protected from predators, seedling emergence did not improve when ground cover was removed. Where seeds were not protected from seed predators, seedling emergence did improve significantly for all three species when ground cover was removed. Apparently, seed predators removed more unprotected seeds where ground cover was present than absent, thereby reducing seedling emergence. These results are consistent with the hypothesis that ground cover could restrict seedling emergence by providing a habitat for seed predators. Key words: old field, seedling emergence, seed predation.

scholarly journals Metagenome-assembled genomes infer potential microbial metabolism in alkaline sulphidic tailings

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Wenjun Li ◽  
Xiaofang Li
Keyword(s):  
Community Structure ◽  
Mine Tailings ◽  
Fluorescent In Situ Hybridization ◽  
High Throughput Sequencing ◽  
Microbial Consortia ◽  
Metabolic Reconstruction ◽  
Metal Release ◽  
Community Members ◽  
Oxidative Stresses

Abstract Background Mine tailings are hostile environment. It has been well documented that several microbes can inhabit such environment, and metagenomic reconstruction has successfully pinpointed their activities and community structure in acidic tailings environments. We still know little about the microbial metabolic capacities of alkaline sulphidic environment where microbial processes are critically important for the revegetation. Microbial communities therein may not only provide soil functions, but also ameliorate the environment stresses for plants’ survival. Results In this study, we detected a considerable amount of viable bacterial and archaeal cells using fluorescent in situ hybridization in alkaline sulphidic tailings from Mt Isa, Queensland. By taking advantage of high-throughput sequencing and up-to-date metagenomic binning technology, we reconstructed the microbial community structure and potential coupled iron and nitrogen metabolism pathways in the tailings. Assembly of 10 metagenome-assembled genomes (MAGs), with 5 nearly complete, was achieved. From this, detailed insights into the community metabolic capabilities was derived. Dominant microbial species were seen to possess powerful resistance systems for osmotic, metal and oxidative stresses. Additionally, these community members had metabolic capabilities for sulphide oxidation, for causing increased salinity and metal release, and for leading to N depletion. Conclusions Here our results show that a considerable amount of microbial cells inhabit the mine tailings, who possess a variety of genes for stress response. Metabolic reconstruction infers that the microbial consortia may actively accelerate the sulphide weathering and N depletion therein.

scholarly journals Spatial and Temporal Variation in Microbial Diversity and Community Structure in a Contaminated Mangrove Wetland

2020 ◽  
Vol 10 (17) ◽  
pp. 5850
Author(s):  
Jiaojiao Ma ◽  
Ting Zhou ◽  
Chunyu Xu ◽  
Dawen Shen ◽  
Songjun Xu ◽  
...  
Keyword(s):  
Community Structure ◽  
Spatial Variation ◽  
Temporal Variation ◽  
Bacterial Diversity ◽  
Diversity Index ◽  
Total Carbon ◽  
Spatial And Temporal Variation ◽  
Rrna Gene ◽  
Mangrove Wetland ◽  
Mangrove Soils

Field and laboratory investigations were conducted to characterize bacterial diversity and community structure in a badly contaminated mangrove wetland adjacent to the metropolitan area of a megacity in subtropical China. Next-generation sequencing technique was used for sequencing the V4–V5 region of the 16s rRNA gene on the Illumina system. Collectively, Proteobacteria, Chloroflexi, Planctomycetes, Actinobacteria and Bacteroidetes were the predominant phyla identified in the investigated soils. A significant spatial variation in bacterial diversity and community structure was observed for the investigated mangrove soils. Heavy metal pollution played a key role in reducing the bacterial diversity. The spatial variation in soil-borne heavy metals shaped the spatial variation in bacterial diversity and community structure in the study area. Other environmental factors such as total carbon and total nitrogen in the soils that are affected by seasonal change in temperature could also influence the bacterial abundance, diversity and community structure though the temporal variation was relatively weaker, as compared to spatial variation. The bacterial diversity index was lower in the investigated site than in the comparable reference site with less contaminated status. The community structure in mangrove soils at the current study site was, to a remarkable extent, different from those in the tropical mangrove wetlands around the world.

Contrôle des impacts du camping en milieu forestier

1985 ◽  
Vol 61 (5) ◽  
pp. 351-357 ◽  
Author(s):  
Jean-Claude Ruel ◽  
Marius Pineau ◽  
Louis Bélanger
Keyword(s):  
Key Words ◽  
Site Selection ◽  
Forest Cover ◽  
Soil Density ◽  
Ground Flora ◽  
Forested Areas ◽  
Monitoring Treatment ◽  
Cover Density ◽  
Recreation Impact

Much of the deterioration observed on many campgrounds in forested areas is closely linked to the presence of the camper. Thus, ground flora cover and composition, forest cover density and vigour, soil density and permeability are affected. Appropriate actions could be taken to reduce undesirable alterations: proper site selection, concentration of the utilization, deterioration monitoring, treatment of the vegetation and modification of the camper's behaviour. Key words: camping; recreation, impact.

scholarly journals Interhemispheric consistency of scale-dependent spatial variation in the structure of intertidal rocky-shore communities

2018 ◽  
Author(s):  
Alexis Catalán ◽  
Nelson Valdivia ◽  
Ricardo Scrosati
Keyword(s):  
Community Structure ◽  
Spatial Variation ◽  
Spatial Scales ◽  
Vertical Gradient ◽  
Sampling Interval ◽  
Biological Variation ◽  
Rocky Intertidal ◽  
Vertical Variation ◽  
Horizontal Variation ◽  
Sampling Intervals

In rocky intertidal environments, the vertical gradient of abiotic stress generates, directly or indirectly, significant spatial variation in community structure. Along shorelines within biogeographic regions, abiotic changes also generate horizontal biological variation, which when measured at large sampling intervals may surpass vertical biological variation. Little is known, however, on how vertical variation compares with horizontal variation measured at multiple spatial scales in habitats with similar environmental conditions. Here, we compare spatial variability in rocky-intertidal communities between vertical stress gradients and three horizontal spatial scales (sampling interval) across habitats experiencing the same wave exposure on the Northwest Atlantic (NWA) and Southeast Pacific (SEP) coasts. For both regions, the vertical variation in species richness and composition (Raup-Crick and Bray-Curtis indices) was higher than the variation measured at all horizontal scales, from a few cm to hundreds of km. The patterns of variation in community structure matched those of abundance for the dominant sessile organisms, the foundation species Ascophyllum nodosum (seaweed) in NWA and Perumytilus purpuratus (mussel) in SEP. This interhemispheric comparison reveals the tight link between environmental and biological variation, indicating that studies comparing spatial scales of biological variation must consider the underlying environmental variation in addition to simply scale alone.

scholarly journals Interhemispheric consistency of scale-dependent spatial variation in the structure of intertidal rocky-shore communities

2018 ◽  
Author(s):  
Alexis Catalán ◽  
Nelson Valdivia ◽  
Ricardo Scrosati
Keyword(s):  
Community Structure ◽  
Spatial Variation ◽  
Spatial Scales ◽  
Vertical Gradient ◽  
Sampling Interval ◽  
Biological Variation ◽  
Rocky Intertidal ◽  
Vertical Variation ◽  
Horizontal Variation ◽  
Sampling Intervals

In rocky intertidal environments, the vertical gradient of abiotic stress generates, directly or indirectly, significant spatial variation in community structure. Along shorelines within biogeographic regions, abiotic changes also generate horizontal biological variation, which when measured at large sampling intervals may surpass vertical biological variation. Little is known, however, on how vertical variation compares with horizontal variation measured at multiple spatial scales in habitats with similar environmental conditions. Here, we compare spatial variability in rocky-intertidal communities between vertical stress gradients and three horizontal spatial scales (sampling interval) across habitats experiencing the same wave exposure on the Northwest Atlantic (NWA) and Southeast Pacific (SEP) coasts. For both regions, the vertical variation in species richness and composition (Raup-Crick and Bray-Curtis indices) was higher than the variation measured at all horizontal scales, from a few cm to hundreds of km. The patterns of variation in community structure matched those of abundance for the dominant sessile organisms, the foundation species Ascophyllum nodosum (seaweed) in NWA and Perumytilus purpuratus (mussel) in SEP. This interhemispheric comparison reveals the tight link between environmental and biological variation, indicating that studies comparing spatial scales of biological variation must consider the underlying environmental variation in addition to simply scale alone.

Plant Community Structure and Composition in Uneven-aged Stands of Loblolly-Shortleaf Pine at Four Basal Area Levels

1995 ◽  
Vol 19 (2) ◽  
pp. 84-88 ◽  
Author(s):  
Philip A. Tappe ◽  
Michael D. Cain ◽  
T. Bently Wigley ◽  
Derik J. Reed
Keyword(s):  
Community Structure ◽  
Plant Community ◽  
Basal Area ◽  
Ground Cover ◽  
Control Treatment ◽  
Plant Community Structure ◽  
Shortleaf Pine ◽  
Single Tree ◽  
Single Tree Selection ◽  
Four Levels

Abstract The effects of overstory pine basal area on plant community structure and composition were assessed in uneven-aged stands of loblolly and shortleaf pines (Pinus taedaL. and P. echinata Mill.) in southern Arkansas. Basal area treatments were 40, 60, 80, and 100 ft2/ac for the merchantable pine component (>3.5 in. dbh) and were maintained on a 6 yr cutting cycle using single-tree selection. Assessments of plant communities were made 10 yr after a single hardwood control treatment. The four levels of pine basal area had no effect on percent ground cover of most plants <3 ft tall, but ground cover from graminoids decreased as pine basal area increased. Vertical cover above loft height increased 33% as overstory basal area increased from 40 to 100 ft2/ac, but basal area had no effect on horizontal cover in height zones between 0 and 10ft. It is concluded that uneven-aged stands of loblolly-shortleaf pine with merchantable basal areas of from 40 to 100 ft²/ac may support similar plant species in the understory and consequently probably provide similar habitat requirements for a variety of game and nongame wildlife. South. J. Appl. For. 19(2):84-88.

scholarly journals Benthic ecology of the northeastern Chukchi Sea. Part II. Spatial variation of megafaunal community structure, 2009–2010

2013 ◽  
Vol 67 ◽  
pp. 67-76 ◽  
Author(s):  
Arny L. Blanchard ◽  
Carrie L. Parris ◽  
Ann L. Knowlton ◽  
Nicole R. Wade
Keyword(s):  
Community Structure ◽  
Spatial Variation ◽  
Chukchi Sea ◽  
Benthic Ecology
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