Differences in the distributions of three species of helicid snail in the limestone district of Derbyshire

1970 ◽  
Vol 176 (1043) ◽  
pp. 131-159 ◽  
Keyword(s):  
Species Composition ◽  
Heavy Rainfall ◽  
Plant Cover ◽  
Cepaea Nemoralis ◽  
Arianta Arbustorum ◽  
Open Woodland ◽  
Carboniferous Limestone ◽  
Made In ◽  
Main Factor

A study on the relative distributions of Cepaea nemoralis (L.), C. hortensis (Müll) and Arianta arbustorum (L,), has been made in three areas on the Carboniferous Limestone of Derbyshire, the Wye valley, Matlock and Dovedale. Samples were made by collecting these species at a large number of sites in different habitats, and also by transects through selected areas. In all the areas studied, the proportion of A. arbustorum in the samples increases with in­creasing plant cover, and is greater on north- than on south-facing slopes. A . arbustorum is commonest, and occupies the widest range of habitats, in the western parts of the Wye valley, which has heavy rainfall. It becomes rarer and more restricted in drier areas farther east. Varia­tions in humidity rather than temperature appear to be the main factor affecting the distribu­tion of this species relative to Cepaea , with A.arbustorum preferring the wetter habitats. Other studies on distribution, survival and behaviour tend to support this conclusion. The proportion of C. nemoralis in Cepaea tends to increase with decreasing plant cover in all areas, but there are important exceptions. Short rough herbage has less C. nemoralis than would be expected from the plant cover, and open woodland has more. These two habitats, with the highest heterogeneity of plant cover within sampling sites, also have the highest proportion of samples containing both species of Cepaea , while the most uniform habitats have the least. This, and other differences of distribution between the three areas, suggest that some of the differences in the distributions of C. nemoralis and C. hortensis are due to competition between them. Although aspect and rainfall have little effect on species composition in Cepaea, C. hortensis predominates in wetter habitats, suggesting that humidity is also an important factor affecting distribution. The transects show that changes in species composition with habitat and aspect occur over short distances.

Kyiv park "Nivki" and "Teremki" forests and ecological analysis of their habitats

2014 ◽  
Vol 25 (3-4) ◽  
pp. 53-68
Author(s):  
I. V. Goncharenko ◽  
H. M. Holyk
Keyword(s):  
Standard Deviation ◽  
Species Composition ◽  
Human Impact ◽  
Soil Nitrogen ◽  
Beta Diversity ◽  
Plant Cover ◽  
Alpha Diversity ◽  
Light Regime ◽  
Individual Species ◽  
Anthropogenic Pressure

Cenotic diversity and leading ecological factors of its floristic differentiation were studied on an example of two areas – Kyiv parks "Nivki" and "Teremki". It is shown that in megalopolis the Galeobdoloni-Carpinetum impatientosum parviflorae subassociation is formed under anthropogenic pressure on the typical ecotope of near-Dnieper hornbeam oak forests on fresh gray-forest soils. The degree of anthropogenic transformation of cenofloras can be estimated by the number of species of Robinietea and Galio-Urticetea classes, as well as neophytes and cultivars. Phytoindication for hemeroby index may be also used in calculation. We propose the modified index of biotic dispersion (normalized by alpha-diversity) for the estimation of ecophytocenotic range (beta-diversity) of releves series. We found that alpha-diversity initially increases (due to the invasion of antropophytes) at low level of antropogenic pressure, then it decreases (due to the loss of aboriginal species) secondarily with increasing of human impact. Also we found that beta-diversity (differential diversity) decreases, increasing homogeneity of plant cover, under the influence of anthropogenic factor. Vegetation classification was completed by a new original method of cluster analysis, designated as DRSA («distance-ranked sorting assembling»). The classification quality is suggested to be validated on the "seriation" diagram, which is а distance matrix between objects with gradient filling. Dark diagonal blocks confirm clusters’ density (intracluster compactness), uncolored off-diagonal blocks are evidence in favor of clusters’ isolation (intercluster distinctness). In addition, distinction of clusters (syntaxa) in ordination area suggests their independence. For phytoindication we propose to include only species with more than 10% constancy. Furthermore, for the description of syntaxonomic amplitude we suggest to use 25%-75% interquartile scope instead of mean and standard deviation. It is shown that comparative analysis of syntaxa for each ecofactor is convenient to carry out by using violin (bulb) plots. A new approach to the phytoindication of syntaxa, designated as R-phytoindication, was proposed for our study. In this case, the ecofactor values, calculated for individual releves, are not taken into account, however, the composition of cenoflora with species constancies is used that helps us to minimize for phytoindication the influence of non-typical species. We suggested a syntaxon’s amplitude to be described by more robust statistics: for the optimum of amplitude (central tendency) – by a median (instead of arithmetic mean), and for the range of tolerance – by an interquartile scope (instead of standard deviation). We assesses amplitudes of syntaxa by phytoindication method for moisture (Hd), acidity (Rc), soil nitrogen content (Nt), wetting variability (vHd), light regime (Lc), salt regime (Sl). We revealed no significant differences on these ecofactors among ecotopes of our syntaxa, that proved the variant syntaxonomic rank for all syntaxa. We found that the core of species composition of our phytocenoses consists of plants with moderate requirements for moisture, soil nitrogen, light and salt regime. We prove that the leading factor of syntaxonomic differentiation is hidden anthropogenic, which is not subject to direct measurement. But we detect that hidden factor of "human pressure" was correlated with phytoindication parameters (variables) that can be measured "directly" by species composition of plant communities. The most correlated factors were ecofactors of soil nitrogen, wetting variability, light regime and hemeroby. The last one is the most indicative empirically for the assessment of "human impact". We establish that there is a concept of «hemeroby of phytocenosis» (tolerance to human impact), which can be calculated approximately as the mean or the median of hemeroby scores of individual species which are present in it.

scholarly journals Researches on Grain Harvesting Machines

1970 ◽  
Vol 66 (1) ◽  
Author(s):  
Mariana DUMITRU
Keyword(s):  
Forward Speed ◽  
Combine Harvester ◽  
Made In ◽  
Main Factor

The purpose of the paper is to present some researches made on the mechanisms of the combine for cutting, feeding and threshing. There are presented the floating cutter bar, the combine with a spike-tooth cylinder and rotary separation, the combine with dual threshing and separating rotors. Some of the adjustments are made on the finger sensors for cutter bar. One of the most important adjustment is that made in order to reduce harvest loss. Forward speed is one of the main factor in optimizing the performance of a combine harvester. The method used in the paper is that of direct observing and measuring made on different component parts of combines.

Rarely Seen Fishes Captured in Hudson Submarine Canyon

1974 ◽  
Vol 31 (2) ◽  
pp. 231-234
Author(s):  
R. L. Haedrich ◽  
P. T. Polloni
Keyword(s):  
Species Composition ◽  
Submarine Canyon ◽  
Abundant Species ◽  
Antimora Rostrata ◽  
Benthic Fishes ◽  
Made In

The alepocephalid Rouleina mollis (Koehler 1896), the ophidiid Xyelacyba myersi Cohen 1961, and the two macrourids Nezumia longebarbatus (Roule and Angel 1933) and Sphagemacrurus grenadae (Parr 1946) were trawled in Hudson Submarine Canyon (ca. 39°18′N 72°00′W) between 1500 and 1960 m on the bottom. These records constitute considerable extensions of the known ranges. The eretmophorid Halargyreus johnsoni Günther 1862, previously recorded from Hudson Canyon but unknown elsewhere in the area, was also taken. The trawl haul which captured these noteworthy species took, in addition, 290 specimens in 18 species of deep benthic fishes. Abundant species included Antimora rostrata, Synaphobranchus kaupi, Alepocephalus agassizi, Nezumia bairdii, Dicrolene intronigra, and Aldrovandia phalacra. These species also predominated in a catch made in a similar haul at the same place 4 yr previously, suggesting that the species composition of such deep-living canyon assemblages is quite stable.

Seasonal variation in soil seed bank size and species composition of selected habitat types in Maputaland, South Africa

Bothalia ◽  
2007 ◽  
Vol 37 (2) ◽  
pp. 249-258 ◽  
Author(s):  
M. J. S. Kellerman ◽  
M. W. Van Rooyen
Keyword(s):  
South Africa ◽  
Seasonal Variation ◽  
Species Composition ◽  
Seed Bank ◽  
Soil Seed Bank ◽  
Woody Species ◽  
Forest Edge ◽  
Seed Banks ◽  
Habitat Types ◽  
Open Woodland

Seasonal variation in seed bank size and species composition of five selected habitat types within the Tembe Elephant Park. South Africa, was investigated. At three-month intervals, soil samples were randomly collected from five different habitat types: a, Licuati forest; b, Licuati thicket; c, a bare or sparsely vegetated zone surrounding the forest edge, referred to as the forest/grassland ecotone; d, grassland; and e, open woodland. Most species in the seed bank flora were either grasses, sedges, or forbs, with hardly any evidence of woody species. The Licuati forest and thicket soils produced the lowest seed densities in all seasons.  Licuati forest and grassland seed banks showed a two-fold seasonal variation in size, those of the Licuati thicket and woodland a three-fold variation in size, whereas the forest/grassland ecotone maintained a relatively large seed bank all year round. The woodland seed bank had the highest species richness, whereas the Licuati forest and thicket soils were poor in species. Generally, it was found that the greatest correspondence in species composition was between the Licuati forest and thicket, as well as the forest/grassland ecotone and grassland seed bank floras.

scholarly journals Testing for consistency in the impacts of a burrowing ecosystem engineer on soil and vegetation characteristics across biomes

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
M. A. Louw ◽  
N. S. Haussmann ◽  
P. C. le Roux
Keyword(s):  
Species Composition ◽  
Ecosystem Engineer ◽  
Environmental Gradients ◽  
Plant Cover ◽  
Ecosystem Engineers ◽  
Conservation Strategies ◽  
Annual Rainfall ◽  
Mesic Grassland ◽  
Vegetation Characteristics ◽  
Semi Arid

AbstractThe impacts of ecosystem engineers may be expected to vary along environmental gradients. Due to some resources being more limited in arid than in mesic environments, disturbances created by burrowing mammals are expected to have a greater ameliorating effect in arid environments, with larger differences in microhabitat conditions expected between burrows and undisturbed areas. The aim of this study was to test if the impacts of a medium-sized burrowing mammal, the aardvark, on soil properties (soil temperature, moisture and compaction) and vegetation characteristics (plant cover, species richness and species composition) are consistent across three biomes that differ strongly in annual rainfall. Burrowing affected soil and vegetation attributes, but the direction and magnitude of these biogeomorphological impacts were not consistent across the different biomes. For example, plant species composition was altered by burrowing in the arid scrubland and in the mesic grassland, but not in the semi-arid savannah. Contrary to expectations, the difference in the impacts of burrowing between biomes were not related to rainfall, with burrowing having strong, albeit different, impacts in both the arid scrubland and the mesic grassland, but weaker effects in the semi-arid savannah. It appears, therefore, that the impacts of these biogeomorphic agents may be site-specific and that it may be difficult to predict variation in their biotic and abiotic effects across environmental gradients. As a result, forecasting the impacts of ecosystem engineers under different conditions remains a challenge to management, restoration and conservation strategies related to these types of species.

After the fence: vegetation and topsoil condition in grazed, fenced and benchmark eucalypt woodlands of fragmented agricultural landscapes

2011 ◽  
Vol 59 (4) ◽  
pp. 369 ◽  
Author(s):  
Suzanne M. Prober ◽  
Rachel J. Standish ◽  
Georg Wiehl
Keyword(s):  
Species Composition ◽  
Plant Species ◽  
Plant Cover ◽  
Agricultural Landscapes ◽  
Livestock Grazing ◽  
Nutrient Concentrations ◽  
Plant Species Composition ◽  
Exotic Plant ◽  
Native Plant ◽  
Plant Richness

Emerging ecological theory predicts that vegetation changes caused by introduction of livestock grazing may be irreversible after livestock are removed, especially in regions such as Australia that have a short evolutionary exposure to ungulate grazing. Despite this, fencing to exclude livestock grazing is the major tool used to restore vegetation in Australian agricultural landscapes. To characterise site-scale benefits and limitations of livestock exclusion for enhancing biodiversity in forb-rich York gum (Eucalyptus loxophleba Benth. subsp. loxophleba)–jam (Acacia acuminata Benth.) woodlands, we compared 29 fenced woodlands with 29 adjacent grazed woodlands and 11 little-grazed ‘benchmark’ woodlands in the Western Australian wheatbelt. We explored the following two hypotheses: (1) fencing to exclude livestock facilitates recovery of grazed woodlands towards benchmark conditions, and (2) without additional interventions after fencing, complete recovery of grazed woodlands to benchmark conditions is constrained by ecological or other limits. Our first hypothesis was supported for vegetation parameters, with fenced woodlands being more similar to benchmark woodlands in tree recruitment, exotic plant cover, native plant cover, native plant richness and plant species composition than were grazed woodlands. Further, exotic cover decreased and frequency of jam increased with time-since-fencing (2–22 years). However, we found no evidence that fencing led to decline in topsoil nutrient concentrations towards concentrations at benchmark sites. Our second hypothesis was also supported, with higher topsoil nutrient concentrations and exotic plant cover, and lower native plant richness in fenced than in benchmark woodlands, and different plant species composition between fenced and benchmark woodlands. Regression analyses suggested that recovery of native species richness is constrained by exotic species that persist after fencing, which in turn are more persistent at higher topsoil nutrient concentrations. We conclude that fencing to exclude livestock grazing can be valuable for biodiversity conservation. However, consistent with ecological theory, additional interventions are likely to be necessary to achieve some conservation goals or to promote recovery at nutrient-enriched sites.

Experimental Study on the Influence of the Grinding Wheel Topography on Grinding Chatter and Grinding Surface Waveness

2009 ◽  
Vol 416 ◽  
pp. 472-476 ◽  
Author(s):  
Ze Yu Weng ◽  
Bo Lu ◽  
Hong Wu You ◽  
Hong Gang Ding ◽  
Yong Cai ◽  
...  
Keyword(s):  
Experimental Study ◽  
Experimental Research ◽  
Grinding Wheel ◽  
Grinding Chatter ◽  
Wheel Topography ◽  
Grinding Wheel Topography ◽  
Grinding Machine ◽  
The Relationship ◽  
Made In ◽  
Main Factor

This paper describes the experimental results of the relationship between grinding wheel topography and grinding chatter and surface waveness on the precise surface grinding machine. The inner relationship between the grinding chatter and grinding surface waveness has been analyzed. The experimental research results show that the grinding depth is a main factor which affects grinding chatter and grinding surface waveness on the grinding surface. Thus a further exploration has been made in the formative mechanism of grinding chatter and grinding surface waveness.

scholarly journals Unassisted establishment of biological soil crusts on dryland road slopes

Web Ecology ◽  
2019 ◽  
Vol 19 (1) ◽  
pp. 39-51 ◽  
Author(s):  
Laura Concostrina-Zubiri ◽  
Juan M. Arenas ◽  
Isabel Martínez ◽  
Adrián Escudero
Keyword(s):  
Species Composition ◽  
Soil Properties ◽  
Vascular Plant ◽  
Plant Cover ◽  
Critical Role ◽  
Biological Soil Crusts ◽  
Functional Structure ◽  
Ecosystem Recovery ◽  
Natural Habitats ◽  
Soil Crusts

Abstract. Understanding patterns of habitat natural recovery after human-made disturbances is critical for the conservation of ecosystems under high environmental stress, such as drylands. In particular, the unassisted establishment of nonvascular plants such as biological soil crusts or biocrust communities (e.g., soil lichens, mosses and cyanobacteria) in newly formed habitats is not yet fully understood. However, the potential of biocrusts to improve soil structure and function at the early stages of succession and promote ecosystem recovery is enormous. In this study, we evaluated the capacity of lichen biocrusts to spontaneously establish and develop on road slopes in a Mediterranean shrubland. We also compared taxonomic and functional diversity of biocrusts between road slopes and natural habitats in the surroundings. Biocrust richness and cover, species composition, and functional structure were measured in 17 road slopes (nine roadcuts and eight embankments) along a 13 km highway stretch. Topography, soil properties and vascular plant communities of road slopes were also characterized. We used Kruskal–Wallis tests and applied redundancy analysis (RDA) to test the effect of environmental scenario (road slopes vs. natural habitat) and other local factors on biocrust features. We found that biocrusts were common in road slopes after ∼20 years of construction with no human assistance needed. However, species richness and cover were still lower than in natural remnants. Also, functional structure was quite similar between roadcuts (i.e., after soil excavation) and natural remnants, and topography and soil properties influenced species composition while environmental scenario type and vascular plant cover did not. These findings further support the idea of biocrusts as promising restoration tools in drylands and confirm the critical role of edaphic factors in biocrust establishment and development in land-use change scenarios.

scholarly journals Effect of monsoon depression of east coast at some distant region in west

MAUSAM ◽  
2021 ◽  
Vol 49 (4) ◽  
pp. 453-460
Author(s):  
ASOI LAL ◽  
R. S. SUNDAR
Keyword(s):  
Heavy Rainfall ◽  
East Coast ◽  
Third Sector ◽  
Wave Model ◽  
Wide Spread ◽  
Easterly Wave ◽  
Rainfall Occurrences ◽  
Normal Rainfall ◽  
Distant Region ◽  
Made In

Whenever a vortex or system of low or depression forms over head bay during Monsoon months, the west coast experiences heavy rainfall. These heavy rainfall occurrences are usually higher than the normal rainfall. An attempt has been made in this study to visualise the easterly wave model during monsoon months with the help of satellite imageries. The rain is expected heavy and wide spread over Madhya Maharashtra and South Gujarat when third sector of the wave covers these areas, as visualised in satellite wave and depression or vortex lies in the 5th or 6th sector of the wave.

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