Journal articles on the topic 'Environmenal gradient'
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1
Jacobucci, G. B., A. Z. Güth, A. Turra, and F. P. P. Leite. "Influence of a narrow depth gradient and season on the morphology, phenology, and epibiosis of the brown alga Sargassum cymosum." Journal of the Marine Biological Association of the United Kingdom 91, no. 4 (December 9, 2010): 761–70. http://dx.doi.org/10.1017/s0025315410001633.
Abstract:
Temporal and spatial fluctuations of environmental parameters are normally assigned as causes of variations in morpho-phenological characters of seaweeds and in their epibionts, but formal tests of such hypotheses are lacking, especially in narrow gradients. The present study evaluated the influence of a very small depth gradient (1 to 3 m) and of subtle seasonality characteristic of tropical areas on morpho-phenological traits and on the occurrence of sessile epiphytic organisms using a controlled orthogonal sampling design in a sublittoral population of the tropical brown alga Sargassum cymosum. Four temporal samples were obtained over a one-year period at three depths using nine replicates. The wet weight, maximum length, number of primary and secondary branches, and proportion of secondary branches with receptacles were recorded. Epibiosis was estimated by visual evaluation of percentage cover on secondary branches. Algal morphology varied as a function of the period of the year (weaker effect) and depth (stronger effect) but in different ways for each variable analysed. In general, fronds tended to be shorter, heavier, and more ramified in shallower areas. In relation to time, the morphological characters tended mostly to present higher values in January (summer) and/or April (autumn). Frequency of receptacles did not depend on algal morphology and depth at all but varied in time, although only in the deepest area. Epibiosis also did not depend on algal morphology but varied in relation to time (stronger effect) and, to a lesser extent, depth (weaker effect). The effect of time upon epibiosis also depended on the biological group analysed. These data support the hypothesis that algal morphology varies in relation to period of the year and depth, even under small temporal and spatial environmenal gradients.
2
Catling, PC, and RJ Burt. "Studies of the Ground-Dwelling Mammals of Eucalypt Forests in South-Eastern New South Wales: the Effect of Environmental Variables on Distribution and Abundance." Wildlife Research 22, no. 6 (1995): 669. http://dx.doi.org/10.1071/wr9950669.
Abstract:
The distribution and abundance of ground-dwelling mammals was examined in 13 areas within 500 000 ha of eucalypt (Eucalyptus) forest in SE New South Wales. Data are presented on the distribution and abundance of species in relation to 3 environmental gradient types involving 9 variables: 2 direct gradients (temperature, rainfall); 6 indirect gradients (aspect, steepness of slope, position on slope, landform profile around the site, altitude, season) and a resource gradient (lithology). Many species of ground-dwelling mammal of the forests of SE New South Wales were present along all gradients examined, although wide variation in abundance occurred for some species. Eight species were correlated with direct gradients and all species were correlated with at least one indirect gradient. There was wide variation and species diversity with lithology, but the variation was not related to nutrient status. Although variations in abundance occurred along environmental gradients, the composition of the ground-dwelling mammal fauna in SE New South Wales forests changed little. A fourth gradient type, the substrate gradient (biomass of plants), had the greatest effect, because in the short-term disturbances such as logging and fire play an important role. Disturbance can have a profound influence on the substrate gradient, but no influence on environmental gradients. The results are discussed in relation to the arboreal mammals and avifauna in the region and Environmental and Fauna Impact studies and forest management.
3
Stine, Caleb A., and Jennifer M. Munson. "Autologous Gradient Formation under Differential Interstitial Fluid Flow Environments." Biophysica 2, no. 1 (January 4, 2022): 16–33. http://dx.doi.org/10.3390/biophysica2010003.
Abstract:
Fluid flow and chemokine gradients play a large part in not only regulating homeostatic processes in the brain, but also in pathologic conditions by directing cell migration. Tumor cells in particular are superior at invading into the brain resulting in tumor recurrence. One mechanism that governs cellular invasion is autologous chemotaxis, whereby pericellular chemokine gradients form due to interstitial fluid flow (IFF) leading cells to migrate up the gradient. Glioma cells have been shown to specifically use CXCL12 to increase their invasion under heightened interstitial flow. Computational modeling of this gradient offers better insight into the extent of its development around single cells, yet very few conditions have been modelled. In this paper, a computational model is developed to investigate how a CXCL12 gradient may form around a tumor cell and what conditions are necessary to affect its formation. Through finite element analysis using COMSOL and coupled convection-diffusion/mass transport equations, we show that velocity (IFF magnitude) has the largest parametric effect on gradient formation, multidirectional fluid flow causes gradient formation in the direction of the resultant which is governed by IFF magnitude, common treatments and flow patterns have a spatiotemporal effect on pericellular gradients, exogenous background concentrations can abrogate the autologous effect depending on how close the cell is to the source, that there is a minimum distance away from the tumor border required for a single cell to establish an autologous gradient, and finally that the development of a gradient formation is highly dependent on specific cell morphology.
4
He, W. M., and R. M. Callaway. "The potential for misleading correlations in single-factor analysis of complex gradients." Web Ecology 9, no. 1 (December 21, 2009): 77–81. http://dx.doi.org/10.5194/we-9-77-2009.
Abstract:
Abstract. Gradient analysis is an important tool for describing patterns in ecology. Natural environmental gradients are complex combinations of factors, suggesting that gradientsshould, when possible, be analyzed in multi-factorial ways. We searched papers published in Ecology, Global Change Biology, Journal of Ecology, Oecologia, Oikos, and Journal of Vegetation Science from January 2001 to December 2005, and found 133 papers matching two keywords: “gradient analysis” and “environmental gradient”. Of these, 86 utilized single-factor correlation analyses between ecological entities and natural environmental gradients. Thus the use of single-factor correlations in studies of natural environmental gradients is widespread despite the potential of this approach to overemphasize the importance of the particular factor chosen. We reanalyzed a data set from the literature, provided a example of contrasting analyses, and analyzed our own data with both single- and multiple-factor analyses to demonstrate how single-factor correlation can result in correlations that provide incomplete analysis. Integrated multi-factor approaches to studying natural environmental gradients cannot solve all analytical problems when two or more important variables are correlated, but are likely to better test the relative importance of factors driving ecological patterns.
5
Souza, Fernanda M., Eliandro R. Gilbert, Kalina M. Brauko, Luciano Lorenzi, Eunice Machado, and Mauricio G. Camargo. "Macrobenthic community responses to multiple environmental stressors in a subtropical estuary." PeerJ 9 (December 7, 2021): e12427. http://dx.doi.org/10.7717/peerj.12427.
Abstract:
We assessed how multi- and univariate models reflect marine environmental health based on macrobenthic community responses to three environmental stressor categories: hydrodynamics, organic enrichment and metal contamination. We then compared the models with the benthic index AMBI (AZTI Marine Biotic Index). Macrobenthic community and physicochemical variables were sampled at 35 sites along Babitonga Bay, a subtropical estuary in Southern Brazil. Distance-based linear modelling identified depth, grain size and organic matter as well as Cu and Zn as key stressors affecting the macrobenthos. Using canonical analysis of principal coordinates (CAP), we developed three multivariate models based on the variability in community composition, creating stress gradients. The metal gradient showed better correlation with the benthic community. Sediment quality indices (Geoaccumulation Index and Contamination Factor) showed a low to moderate contamination status, with higher concentrations for Cr, Ni and Zn at the inner areas of the bay. According to AMBI, Babitonga Bay has a “good” environmental health status, and the AMBI values show stronger correlations with the hydrodynamic and organic enrichment gradients (r = 0.50 and r = 0.47) rather than the metal gradient (r = 0.29). Lumbrineridae polychaetes (not included in the AMBI list) and Scoloplos sp. were negatively related to the metal contamination gradient and were considered sensitive, while Sigambra sp., Magelona papillicornis, the gastropod Heleobia australis and species of the crustacean order Mysida were positively related to the gradient and considered tolerant to higher concentrations of metals in the sediment. Despite the inconsistency in the ecological classification provided by AMBI and its relationship with the metal gradient, our results suggest that the environmental quality was satisfactory for the studied gradients. The metal gradient showed the weakest correlation to AMBI. In such cases, the ecological classification of taxa by the index should be evaluated under the perspective of the action of inorganic genotoxic contaminants represented by metals.
6
Connor, Stephanie J., Alexa C. Alexander-Trusiak, and Donald J. Baird. "Vulnerability of diatom communities in the Peace–Athabasca Delta to environmental change." PeerJ 6 (August 9, 2018): e5447. http://dx.doi.org/10.7717/peerj.5447.
Abstract:
Habitat degradation associated with resource development is a major ecological concern, particularly in Canada’s boreal zone where limited information on biodiversity is available. Habitat degradation can lead to reductions in biodiversity and ecosystem function, especially when drivers of variability and diversity patterns have not been identified for a region of interest. In this study, the distribution of diatom genera in the Peace–Athabasca Delta in northeastern Alberta was examined in relation to seasonal, geographic, and alkalinity gradients. Grab samples of six abiotic variables (total dissolved nitrogen, total dissolved phosphorus, dissolved iron, turbidity, pH, and specific conductance (SPC)) were taken from 12 remote wetlands over three sampling periods, and regressed against an ordination of diatom community composition to identify key environmental drivers of diatom community variation. Indirect gradient analysis identified two major gradients among sites. First, separation of sites among sampling periods showed successional seasonal changes in diatom community composition. Second, separation of sites from the Peace sub-delta and Birch sub-delta showed a gradient of geographic separation. Direct gradient analysis failed to explain the underlying drivers of these two gradients, but did show that alkalinity is a key driver of diatom community composition in the Embarras sub-delta, and that these sites could be particularly vulnerable to community changes associated with acidification.
7
Campos-Cerqueira, Marconi, and T. Mitchell Aide. "Changes in the acoustic structure and composition along a tropical elevational gradient." Journal of Ecoacoustics 1, no. 1 (December 6, 2017): 1. http://dx.doi.org/10.22261/jea.pnco7i.
Abstract:
Elevational gradients influence the distribution and composition of animal species and can provide useful information for the development of conservation strategies in the context of climate change. Despite an increase in studies of species diversity along elevational gradients, there is still a lack of information about community responses to environmental gradients, in part because of the logistical limitations of sampling multiple taxa simultaneously. One solution is to use passive acoustic monitoring (PAM) to acquire and analyze information from different animal taxa simultaneously along an entire elevational gradient. To improve our understanding of how environmental gradients influence patterns of animal communities and to test the relationship between soundscapes and animal composition we investigated how variation in bird and anuran composition affect the acoustic structure and composition of the soundscapes along an elevation gradient. We used PAM deploying portable acoustic recorders along three elevational transects in the Luquillo Mountains (LM), Puerto Rico. We found that elevation plays a major role in structuring the acoustic community and that the soundscape composition reflected the same patterns of anuran and bird distribution and composition along the elevational gradient. This study shows how different animal taxa respond to environmental gradients and provide strong evidence for the use of soundscapes as a tool to describe and compare species distribution and composition across large spatial scales.
8
Bogale Worku, Belachew, Melese Genete Muluneh, and Tesfaye Molla. "Influence of Elevation and Anthropogenic Disturbance on Woody Species Composition, Diversity, and Stand Structure in Harego Mountain Forest, Northeastern Ethiopia." International Journal of Forestry Research 2023 (November 17, 2023): 1–17. http://dx.doi.org/10.1155/2023/8842408.
Abstract:
Environmental variables like elevation affect species composition, diversity, distribution, density, and horizontal and upward growth. Ecologists are constantly working to better understand how species diversity varies along elevational gradients, particularly in mountainous ecosystems. Therefore, the purpose of this research was to examine the species’ horizontal and vertical structural diversity along the Harego Mountain Forest’s elevational gradient. The area was categorized into lower, middle, and upper elevations. A total of 67 (20 m × 20 m) plots were created along gradients of elevation 2,079–2,516 meters above sea level (m a.s.l.). Information for floristic composition, diversity, stand structure, and environmental variables were measured and recorded for each plot over the three elevational gradients. Data on anthropogenic disturbances were visually evaluated for every plot in every gradient of elevation. For the diversity analysis, Hill’s diversity statistics were employed. To find significant variations between the three elevational gradients in terms of Hill’s diversity number, stand structure, and environmental variables, the one-way analysis of variance with SPSS version 26 at the 0.05 level of significance was carried out. The finding revealed that 50 woody plants that belonged to 35 families and 44 genera in the 67 sample plots with an elevation of 2,079 to 2,516 were identified. Shrubs were dominant in each elevational gradient. Species richness, abundance, and Hill’s diversity number were all significantly ( p < 0.05 ) greater in the upper elevational gradient of the forest. On the other hand, all stand structures were significantly ( p < 0.05 ) higher in the middle elevational gradient. The effect of anthropogenic disturbances and environmental variables were clearly observed in the lower and upper elevational gradients than in the middle elevation. As a result, there were fewer seedlings, saplings, trees, and shrubs in the gradients of lower and higher elevations. For the conservation of the forest, it is crucial to pay special attention to biotic elements at lower elevations and abiotic factors at higher elevations. Accordingly, involving the local community in forest management, reducing anthropogenic pressure in and around the Harego Mountain Forest through tree planting in farmlands and woodlots and implementing physical soil and water conservation structures are recommended.
9
Allen, Robert B., and Robert K. Peet. "Gradient analysis of forests of the Sangre de Cristo Range, Colorado." Canadian Journal of Botany 68, no. 1 (January 1, 1990): 193–201. http://dx.doi.org/10.1139/b90-026.
Abstract:
Interrelationships between dominant compositional and environmental gradients were studied using 186 forest stands sampled on the east slope of the Sangre de Cristo Range, Colorado. Detrended correspondence analysis and detrended canonical correspondence analysis were used to analyze indirect and direct gradients, respectively. The dominant compositional gradient was strongly correlated with elevation. Increasing elevation was associated with decreasing soil pH and percent base saturation, and increasing total soil N. Ordination of stands stratified by elevation showed the major compositional gradient within each elevation class was strongly correlated with a topographic moisture index. Most soil variables correlated with this gradient in low and high elevation classes. In mid-elevation forests, a third compositional gradient correlated with soil pH, percent base saturation, and potential solar radiation. In these forests, Pinus contorta and Pseudotsuga menziesii were associated with acidic soils on north-facing slopes, whereas Populus tremuloides and Abies concolor were associated with base-rich soils on south-facing slopes. Ordination axes accounted for least variation in comparatively young mid-elevation forests. A plausible explanation is that the mid-elevation forests represent an unpredictable stage in forest development where competition has not yet had sufficient time to sort species along environmental gradients.
10
Olthoff, Adriana E., Carolina Martínez-Ruiz, and Josu G. Alday. "Niche Characterization of Shrub Functional Groups along an Atlantic-Mediterranean Gradient." Forests 12, no. 8 (July 24, 2021): 982. http://dx.doi.org/10.3390/f12080982.
Abstract:
The identification of the factors controlling the understory species distribution and abundance is essential to understand the ecology and dynamics of natural forests and their management response. We assess the relationships between environmental gradients and shrub functional groups distribution patterns and niche characteristics in a transitional area between the Eurosiberian and Mediterranean biogeographic regions in Northern Spain. Here, 772 plots from the 3rd Spanish National Forest Inventory were used. Shrub functional groups respond to the same complex environmental gradients as trees, i.e., the north-south climatic gradient and a slope gradient. Unimodal response curves of shrub functional groups and families dominate along both gradients, providing evidence of successful functional turnover. Similar to tree species, the niche location of functionally related shrubs is close. Functional groups occupying environments with sharp contrast or transitional environments have the broadest niches, whereas those specialized functional groups occupying localized habitats showed the narrowest niches. The knowledge of shrub species distributions and niche characteristics along complex environmental gradients will improve our ability to discuss potential conservation management goals or threats due to land-use changes and future climate change.
11
Lookingbill, Todd R., and Dean L. Urban. "Gradient analysis, the next generation: towards more plant-relevant explanatory variables." Canadian Journal of Forest Research 35, no. 7 (July 1, 2005): 1744–53. http://dx.doi.org/10.1139/x05-109.
Abstract:
The long history of gradient analysis is anchored in the observation that species turnover can be described along elevation gradients. This model is unsatisfying in that elevation is not directly relevant to plants and the ubiquitous "elevation gradient" is composed of multiple intertwined environmental factors. We offer an approach to landscape-scale vegetation analysis that disentangles the elevation gradient into its constituent parts through focused field sampling and statistical analysis. We illustrate the approach for an old-growth watershed in the Oregon Western Cascades. Our initial model of this system supports the common observation that forest community types are highly associated with specific elevation bands. By replacing elevation and other crude environmental proxy variables with estimates of more direct and resource gradients (radiation, temperature, and soil moisture), we create a vegetative model with stronger explanatory power than the proxy model in both cross-validation analysis and validation using an independent data set. The resulting model is also more biologically interpretable, which provides more meaningful insight into potential forest response to environmental change (e.g., global climate change scenarios). Acquiring a better mechanistic understanding of the relationship between plant communities and environmental predictor variables presents the next great challenge to community ecologists conducting gradient studies at landscape scales.
12
Økland, R. H., and E. Bendiksen. "The vegetation of the forest-alpine transition in the Grunningsdalen area, Telemark, S. Norway." Sommerfeltia 2, no. 1 (November 1, 1985): 1–171. http://dx.doi.org/10.2478/som-1985-0002.
Abstract:
Abstract This study is divided into two parts. The general part contains a review of theories of the nature of vegetation. It is concluded that present evidence points in the direction of species individuality and vegetational continuum as responses to continuous environmental gradients, on a regional, and mostly also on a local scale. Accordingly, a gradient approach to classification of the forest and alpine vegetation of the investigated area was designed as an alternative to traditional phytosociological classification. The importance of the concept of corresponding vegetation types in different regions is stressed. It is argued that four environmental gradients explain the major variation in Southern Norwegian forest and alpine vegetation. In the special part, the vegetation of the Grunningsdalen area is treated. Two gradients, the vertical gradient and the complex-gradient topographic moisture snow cover, are considered sufficient to explain the major variation in forest and alpine vegetation in the area. The vegetation is classified into 16 site-types by division of the gradients into four zones (according to altitude) and four series (according to moisture - snow cover) by means of floristic criteria known to reflect particular ecological conditions. For each of the site-types a description of the vegetation and an extensive comparison with corresponding Fennoscandian vegetation is given. On the basis of results from the present study area regional variation in Southern Norwegian poor vegetation corresponding to the xeric, subxeric, and submesic series, and phytosociological classification in the forestalpine transition are discussed. Various numerical classification and ordination methods are used in an analysis of the floristic composition of the site-types and the autecology of the species. The main phytosociological gradient in the investigated vegetation runs from dry and high altitude to wet and low altitude, most closely approaching the moisture gradient. Diversity relations are discussed. It is strongly emphasized that a hierarchic system is unable to give a consistent classification of a vegetation that must be regarded as a multidimensional network of variation along environmental gradients. Viewed in the light of the results of this study, a gradient approach to classification seems most suitable for a variety of Fennoscandian ecosystems.
13
BROWN, GARETT M. "LITHOLOGICAL AND PALEOCOMMUNITY VARIATION ON A MISSISSIPPIAN (TOURNAISIAN) CARBONATE RAMP, MONTANA, USA." PALAIOS 36, no. 3 (March 30, 2021): 95–114. http://dx.doi.org/10.2110/palo.2020.050.
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ABSTRACT The ecological structure of ancient marine communities is impacted by the environmental gradients controlling assemblage compositions and the heterogeneous distribution of sediment types. Closely spaced, replicate sampling of fauna has been suggested to mitigate the effects of such heterogeneity and improve gradient analyses, but this technique has rarely been combined with similar sampling of lithologic data. This study analyses lithological and faunal data to determine the environmental gradients controlling the composition of Mississippian fossil assemblages of the lower Madison Group in Montana. Eighty-one lithological and faunal samples were collected from four stratigraphic columns in Montana, which represent the deep-subtidal, foreshoal, and ooid-shoal depositional environments within one third-order depositional sequence. Cluster analysis identifies three distinct lithological associations across all depositional environments—crinoid-dominated carbonates, peloidal-crinoidal carbonates, and micritic-crinoidal carbonates. Cluster analysis and nonmetric multidimensional scaling (NMS) identifies a highly diverse brachiopod biofacies and a solitary coral-dominated biofacies along an onshore-offshore gradient. Carbonate point count data and orientation of solitary corals indicate that substrate and wave energy are two potential variables that covary with the onshore-offshore gradient. Overlaying lithological information on the NMS indicates a secondary gradient reflecting oxygen that is expressed by increasing bioturbation and gradation from brown to dark gray carbonates to medium-light gray carbonates. Taken together, these findings demonstrates how combining closely spaced, replicate sampling of lithologic and faunal data enhances multivariate analyses by uncovering underlying environmental gradients that control the variation in fossil assemblages.
14
Wright, Kristopher K., and Judith L. Li. "From continua to patches: examining stream community structure over large environmental gradients." Canadian Journal of Fisheries and Aquatic Sciences 59, no. 8 (August 1, 2002): 1404–17. http://dx.doi.org/10.1139/f02-113.
Abstract:
We present an approach that integrates a conceptual framework with multivariate ordination techniques and traditional parametric analyses to examine biotic and abiotic gradients in stream ecosystems. Ordinations were used to examine multivariate patterns along an environmental gradient, with individual variables used to interpret those patterns across spatial scales. The conceptual framework provides a consistent context to compare community distributions and consequently allows for hypothesis testing using ordinations. To illustrate the approach, we examined the physical template, fish and benthic macroinvertebrate communities, and algal biomass and production along a 1st- through 5th-order stream gradient in eastern Oregon. We hypothesized that longitudinal distributions of physical habitat characteristics, fishes, macroinvertebrates, and periphyton would reflect highly variable, discontinuous gradients. Multivariate patterns were determined by rotating nonparametric ordinations to a common set of variables and comparing them to conceptual models of (i) an ideal continuum, (ii) a random distribution, and (iii) discrete patches. Physical habitat and fishes reflected strong longitudinal gradients, macroinvertebrates were the most patchy, and algal biomass and production were highly variable. Distributions of individual variables from site and stream-order perspectives revealed how different factors, potentially influencing stream communities, may be continuous or patchy depending on spatial scale.
15
Daco, Laura, Guy Colling, and Diethart Matthies. "Altitude and latitude have different effects on population characteristics of the widespread plant Anthyllis vulneraria." Oecologia 197, no. 2 (October 2021): 537–49. http://dx.doi.org/10.1007/s00442-021-05030-6.
Abstract:
AbstractWidespread plants may provide natural models for how population processes change with temperature and other environmental variables and how they may respond to global change. Similar changes in temperature can occur along altitudinal and latitudinal gradients, but hardly any study has compared the effects of the two types of gradients. We studied populations of Anthyllis vulneraria along a latitudinal gradient from Central Europe to the range limit in the North and an altitudinal gradient in the Alps from 500 m to the altitudinal limit at 2500 m, both encompassing a change in annual mean temperature of c. 11.5 °C. Plant size and reproduction decreased, but plant density increased along both gradients, indicating higher recruitment and demographic compensation among vital rates. Our results support the view that demographic compensation may be common in widespread species in contrast to the predictions of the abundant centre model of biogeography. Variation in temperature along the gradients had the strongest effects on most population characteristics, followed by that in precipitation, solar radiation, and soil nutrients. The proportion of plants flowering, seed set and seed mass declined with latitude, while the large variation in these traits along the altitudinal gradient was not related to elevation and covarying environmental variables like annual mean temperature. This suggests that it will be more difficult to draw conclusions about the potential impacts of future climate warming on plant populations in mountains, because of the importance of small-scale variation in environmental conditions.
16
Nhalil, Hariharan, Moty Schultz, Shai Amrusi, Asaf Grosz, and Lior Klein. "High Sensitivity Planar Hall Effect Magnetic Field Gradiometer for Measurements in Millimeter Scale Environments." Micromachines 13, no. 11 (November 2, 2022): 1898. http://dx.doi.org/10.3390/mi13111898.
Abstract:
We report a specially designed magnetic field gradiometer based on a single elliptical planar Hall effect (PHE) sensor, which allows measuring magnetic field at nine different positions in a 4 mm length scale. The gradiometer detects magnetic field gradients with equivalent gradient magnetic noises of ∼958, ∼192, ∼51, and ∼26 nT/m√ Hz (pT/mm√Hz) at 0.1, 1, 10, and 50 Hz, respectively. The performance of the gradiometer is tested in ambient conditions by measuring the field gradient induced by electric currents driven in a long straight wire. This gradiometer is expected to be highly useful for the measurement of magnetic field gradients in confined areas for its small footprint, low noise, scalability, simple design, and low costs.
17
Turon, Xavier, Ruth Martí, and Maria J. Uriz. "Chemical bioactivity of sponges along an environmental gradient in a Mediterranean cave." Scientia Marina 73, no. 2 (March 17, 2009): 387–97. http://dx.doi.org/10.3989/scimar.2009.73n2387.
18
Thundathil, Rohith, Florian Zus, Galina Dick, and Jens Wickert. "Assimilation of GNSS tropospheric gradients into the Weather Research and Forecasting (WRF) model version 4.4.1." Geoscientific Model Development 17, no. 9 (May 3, 2024): 3599–616. http://dx.doi.org/10.5194/gmd-17-3599-2024.
Abstract:
Abstract. In this study, we have incorporated tropospheric gradient observations from a Global Navigation Satellite Systems (GNSS) ground station network into the Weather Research and Forecasting (WRF) model through a newly developed observation operator. The experiments aim at testing the functionality of the developed observation operator and at analyzing the impact of tropospheric gradients on the sophisticated data assimilation (DA) system. The model was configured for a 0.1° mesh over Germany with 50 vertical levels up to 50 hPa. Our initial conditions were obtained from the National Centers for Environmental Prediction (NCEP) Global Forecast System (GFS) data at 0.25° resolution, and conventional observations were obtained from the European Centre for Medium-Range Weather Forecasts (ECMWF), restricted to mainly surface stations and radiosondes. We selected approximately 100 GNSS stations with high data quality and availability covering Germany. We performed DA every 6 h for June and July 2021. Four experiments were conducted: (1) a control run assimilating only conventional observations; (2) an impact run assimilating zenith total delays (ZTDs) on top of the control run; (3) an impact gradient run assimilating ZTDs and gradients on top of the control run; and (4) a gradient run assimilating only gradients on top of the control run. The error for the impact run was reduced by 32 % and 10 % for ZTDs and gradients, whereas the error for the impact gradient run was reduced by 35 % and 18 %, respectively. The gradient errors for the gradient run were nearly equal to those of the impact gradient. Overall, the newly developed operator for the WRFDA system works as intended. In particular, the combined assimilation of gradients and the ZTDs led to a notable improvement in the humidity field at altitudes above 2.5 km. With the operator codes developed and freely available to the WRF users, we aim to trigger further GNSS tropospheric gradient assimilation studies.
19
Bush, Andrew M., and Roderic I. Brame. "Multiple paleoecological controls on the composition of marine fossil assemblages from the Frasnian (Late Devonian) of Virginia, with a comparison of ordination methods." Paleobiology 36, no. 4 (2010): 573–91. http://dx.doi.org/10.1666/07022.1.
Abstract:
Ecological ordination can reveal gradients in the species composition of fossil assemblages that can be correlated with paleoenvironmental gradients. Ordinations of simulated data sets suggest that nonmetric multidimensional scaling (NMDS) generally produces less distorted results than detrended correspondence analysis (DCA). We ordinated 113 brachiopod-dominated samples from the Frasnian (Late Devonian) Brallier, Scherr, and lower Foreknobs Formations of southwest Virginia, which represent a range of siliciclastic marine paleoenvironments. A clear environmental signal in the ordination results was obscured by (apparently) opportunistic species that occurred at high abundance in multiple environments; samples dominated by these species aggregated in ordination space regardless of paleoenvironmental provenance. After the opportunist-dominated samples were removed, NMDS revealed a gradient in species composition that was highly correlated with substrate (grain size); a second, orthogonal gradient likely reflects variation in disturbance intensity or frequency within grain-size regimes. Additional environmental or ecological factors, such as oxygenation, may also be related to the gradients. These two gradients, plus the environmental factors that controlled the occurrence of opportunistic species, explain much of the variation in assemblage composition in the fauna. In general, the composition of fossil assemblages is probably influenced by multiple paleoecological and paleoenvironmental factors, but many of these can be decomposed and analyzed.
20
van Son, Thijs Christiaan, Rune Halvorsen, Karl Norling, Torgeir Bakke, Maria Kaurin, and Fredrik Melsom. "Identification of Fine-Scale Marine Benthic Ecoclines by Multiple Parallel Ordination." Journal of Marine Biology 2014 (2014): 1–23. http://dx.doi.org/10.1155/2014/462529.
Abstract:
The species-environment relationship is a fundamental structural property of natural ecosystems. Marine sedimentary macrofauna is known to be structured by a range of environmental variables; however, the mechanisms by which environmental variables covary to form complex-gradients (i.e., groups of intercorrelated environmental variables), and how these are related to coenoclines (i.e., gradients in species composition), remain poorly understood. We classified our study area into geomorphological features that were used for stratified sampling of macrofaunal polychaetes, molluscs, and echinoderms. The resulting species-by-site matrix was subjected to indirect gradient analysis by a multiple parallel ordination strategy, using detrended correspondence analysis and nonmetric multidimensional scaling. One major and one minor coenocline were identified. Based on the correlation between complex-gradients and the main coenocline we hypothesise the existence of two ecoclines that we have termedPeriodic hypoxiaandPeriodic physical forcing. We conclude that a combination of recurrent (periodical) and extreme events is likely to determine the variation found in the species composition of marine sedimentary ecosystems. Based on the results of our study, we conclude that indirect gradient analysis is a useful tool for enhancement of our basic mechanistic understanding of the processes governing the compositional structure of marine sediment communities.
21
Costa, Alan N., Emilio M. Bruna, and Heraldo L. Vasconcelos. "Do an ecosystem engineer and environmental gradient act independently or in concert to shape juvenile plant communities? Tests with the leaf-cutter ant Atta laevigata in a Neotropical savanna." PeerJ 6 (October 9, 2018): e5612. http://dx.doi.org/10.7717/peerj.5612.
Abstract:
Background Ecosystem engineers are species that transform habitats in ways that influence other species.While the impacts of many engineers have been well described, our understanding of how their impact varies along environmental gradients remains limited. Although disentangling the effects of gradients and engineers on biodiversity is complicated—the gradients themselves can be altered by engineers—doing so is necessary to advance conceptual and mathematical models of ecosystem engineering. We used leaf-cutter ants (Atta spp.) to investigate the relative influence of gradients and environmental engineers on the abundance and species richness of woody plants. Methods We conducted our research in South America’s Cerrado. With a survey of plant recruits along a canopy cover gradient, and data on environmental conditions that influence plant recruitment, we fit statistical models that addressed the following questions: (1) Does A. laevigata modify the gradient in canopy cover found in our Cerrado site? (2) Do environmental conditions that influence woody plant establishment in the Cerrado vary with canopy cover or proximity to A. laevigata nests? (3) Do A. laevigata and canopy cover act independently or in concert to influence recruit abundance and species richness? Results We found that environmental conditions previously shown to influence plant establishment in the Cerrado varied in concert with canopy cover, but that ants are not modifying the cover gradient or cover over nests. However, ants are modifying other local environmental conditions, and the magnitude and spatial extent of these changes are consistent across the gradient. In contrast to prior studies, we found that ant-related factors (e.g., proximity to nests, ant changes in surface conditions), rather than canopy cover, had the strongest effect on the abundance of plant recruits. However, the diversity of plants was influenced by both the engineer and the canopy cover gradient. Discussion Atta laevigata in the Cerrado modify local conditions in ways that have strong but spatially restricted consequences for plant communities. We hypothesize that ants indirectly reduce seedling establishment by clearing litter and reducing soil moisture, which leads to seed and seedling desiccation. Altering soil nutrients could also reduce juvenile growth and survivorship; if so these indirect negative effects of engineering could exacerbate their direct effects of harvesting plants. The effects of Atta appear restricted to nest mounds, but they could be long-lasting because mounds persist long after a colony has died or migrated. Our results support the hypothesis that leaf-cutter ants play a dominant role in Cerrado plant demography. We suggest the ecological and economic footprint of these engineers may increase dramatically in coming decades due to the transformation of the Cerrado by human activities.
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Hall, Catherine J., and Carolyn W. Burns. "Environmental gradients and zooplankton distribution in a shallow, tidal lake." Fundamental and Applied Limnology 154, no. 3 (July 1, 2002): 485–97. http://dx.doi.org/10.1127/archiv-hydrobiol/154/2002/485.
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Økland, T. "Vegetation-environment relationships of boreal spruce forests in ten monitoring reference areas in Norway." Sommerfeltia 22, no. 1 (May 1, 1996): 1–355. http://dx.doi.org/10.2478/som-1996-0001.
Abstract:
Abstract Vegetational and environmental monitoring of boreal spruce forest was initiated in 1988, as a part of the programme “Contrywide Monitoring of Forest Health” at the Norwegian Institute of Land Inventory (NIJOS). As a basis for monitoring, relationships between trees, understory vegetation and environmental conditions (vertical relationships) were analysed for each of ten reference areas. The reference areas were selected to span regional gradients, in climatic conditions and deposition of airborne pollutants, in old-growth, so-called “bilberry-dominated”, “small-fem” and “low-herb”, also paludified, spruce forests south of the Polar Circle. Fifty 1-m2 meso sample plots, randomly chosen within ten 50-m2 macro sample plots in each reference area, were subjected to vegetation analysis, using frequency in subplots as species abundance measure. Environmental (including soil chemical) and tree parameters were recorded for meso as well as macro sample plots. The main vegetational gradients were found by parallel use of DCA and LNMDS ordination methods and subjected to environmental interpretation, mainly by means of non-parametric correlation analyses. DCA and LNMDS in most cases revealed the same main gradients in vegetation, but outliers were more frequent in LNMDS ordinations, due to higher vulnerability of this method to plots with deviating number of species. A complex-gradient in nutrient conditions, with pH and the concentration of nitrogen as the most constantly contributing variables, but with considerable between-area variation with respect to important cations, was evident in nine reference areas. Soil moisture varied along the second vegetational gradient in most areas. In the three most humid reference areas, the Ca concentration was related to variation in soil moisture and gradients from below to between trees, while unrelated or inversely related to the same vegetational gradient as pH. Species abundances were plotted on plot positions in DCA ordinations in order to summarize the species· responses to environmental variation in each area. Variation in vegetation in the total data set (500 meso sample plots) was partitioned onto two sets of explantory variables (environmental and climatic/geographical) by use of CCA, in order to find the relative importance of environmental and climatic/geographical variation. The fraction of variation exclusively explained by environmental variables was about 1 7%, while only 5% of the variation was explained exclusively by climatic variables. The variation shared by both sets of variables was about 8%. The main vegetational gradients and environmental/climatic/geographical complex-gradients in the total data set were found by DCA and subsequent interpretation of axes. The main complex-gradients found by separate analyses of data from each reference area, were reflected along the DCA axes in total ordinations, but differences between areas with respect to positions along both environmental and climatic/geographical gradients were also evident. Meso plot occurrences of selected species were plotted in a DCA ordination of the total data set, with variation exclusively due to climatic/geographical variables removed, in order to express regional similarities and differences in the species· responses to the environment. The different patterns of species· distributions in the DCA ordination were discussed in the light of their use as indicators of specified environmental conditions.
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Keil, Matthias S. "Smooth Gradient Representations as a Unifying Account of Chevreul's Illusion, Mach Bands, and a Variant of the Ehrenstein Disk." Neural Computation 18, no. 4 (April 1, 2006): 871–903. http://dx.doi.org/10.1162/neco.2006.18.4.871.
Abstract:
Recent evidence suggests that the primate visual system generates representations for object surfaces (where we consider representations for the surface attribute brightness). Object recognition can be expected to perform robustly if those representations are invariant despite environmental changes (e.g., in illumination). In real-world scenes, it happens, however, that surfaces are often overlaid by luminance gradients, which we define as smooth variations in intensity. Luminance gradients encode highly variable information, which may represent surface properties (curvature), nonsurface properties (e.g., specular highlights, cast shadows, illumination inhomogeneities), or information about depth relationships (cast shadows, blur). We argue, on grounds of the unpredictable nature of luminance gradients, that the visual system should establish corresponding representations, in addition to surface representations. We accordingly present a neuronal architecture, the so-called gradient system, which clarifies how spatially accurate gradient representations can be obtained by relying on only high-resolution retinal responses. Although the gradient system was designed and optimized for segregating, and generating, representations of luminance gradients with real-world luminance images, it is capable of quantitatively predicting psychophysical data on both Mach bands and Chevreul's illusion. It furthermore accounts qualitatively for a modified Ehrenstein disk.
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Jeglum, John K., and Fangliang He. "Pattern and vegetation–environment relationships in a boreal forested wetland in northeastern Ontario." Canadian Journal of Botany 73, no. 4 (April 1, 1995): 629–37. http://dx.doi.org/10.1139/b95-067.
Abstract:
A forested wetland data set from northeastern Ontario, consisting of species cover and environmental measures in 43 stands, was analyzed with canonical correspondence analysis. Results showed two main vegetational gradients related to factor complexes of peat depth – moisture (mire margin to mire expanse) and pH–calcium. Stands within each of the vegetation types were positioned closely, and gradients of types were similar to those from earlier analyses, suggesting the validity of a previous classification. Axis I of the ordination was highly related to peat depth, several elements (Al, Fe, and Cu), loss on ignition, bulk density, and water content in peat. Axis II was highly related to loss on ignition, depth of fibric layer, pH, and several elements (Ca, Mg, Mn, and N). The number of species in a plot was strongly correlated to the pH–calcium gradient, whereas vegetation cover was strongly correlated to the peat depth – moisture gradient. Analysis with detrended correspondence analysis gave results very similar to canonical correspondence analysis, suggesting that there was a relatively high correspondence between vegetational and environmental gradients. Environmental measures were partitioned into physical and chemical attributes, to detect the relative contribution to vegetational variation. Both physical and chemical variables were important, and 81% of the variation in vegetation was explained by the environmental measures. Key words: boreal forest, multivariate analysis, Ontario, wetlands, vegetation pattern, diversity.
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Minor, Maria A., Sergey G. Ermilov, Omid Joharchi, and Dmitriy A. Philippov. "Using Spectral Indices Derived from Remote Sensing Imagery to Represent Arthropod Biodiversity Gradients in a European Sphagnum Peat Bog." Arthropoda 1, no. 1 (December 31, 2022): 35–46. http://dx.doi.org/10.3390/arthropoda1010006.
Abstract:
Monitoring of peatlands is an important conservation issue. We investigated communities of soil mites (Acari: Oribatida, Mesostigmata) inhabiting a relatively undisturbed European boreal mire characterized by a mosaic of oligotrophic and meso-eutrophic areas. We assess the potential of using remote sensing approach as a mapping and predictive tool for monitoring productivity and arthropod biodiversity in a peat bog. In georeferenced plots, Acari biodiversity, water table level, water pH and plot productivity class on the oligotrophic-eutrophic gradient were recorded. Data from the Landsat 8 OLI sensor were used to calculate several spectral indices known to represent productivity and surface moisture gradients in terrestrial ecosystems. We then explored the relationship between spectral indices, environmental gradients and biodiversity of mites. We found that several spectral indices were significantly and consistently correlated with local environmental variables and biodiversity of soil mites. The Excess Green Index performed best as a predictor of plot trophic class on the oligotrophic-eutrophic gradient and showed significant relationship with Oribatida diversity in 2016. However, following hot summer in 2019, there was no significant relationship between abundance and species richness of Oribatida and remotely sensed data; there was a weak correlation between abundance of Mesostigmata and spectral indices which represent surface moisture gradient (e.g., Normalised Difference Moisture Index). We discuss advantages and challenges of using spectral indices derived from remote sensing imagery to map biodiversity gradients in a peatland.
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Wana, Desalegn, and Carl Beierkuhnlein. "Responses of plant functional types to environmental gradients in the south-west Ethiopian highlands." Journal of Tropical Ecology 27, no. 03 (March 10, 2011): 289–304. http://dx.doi.org/10.1017/s0266467410000799.
Abstract:
Abstract:Plant functional types across environmental gradients can be considered as a powerful proxy that reveals vegetation–environment relationships. The objectives of this study were to investigate the response in the relative abundance of plant functional types along altitudinal gradients and to examine the relationship of plant functional types to environmental variables. The study was conducted in the Gughe-Amaro Mountains, in the south-west Ethiopian highlands. We established 74 plots with an area of 400 m2(20 × 20 m) each along altitudinal ranges between 1000 and 3000 m asl. Data on site environmental conditions and on the abundance of plant functional types were analysed using the constrained linear ordination technique (RDA) in order to identify the relationships between plant functional types and environmental variables. Altitude, soil organic carbon, soil sand fraction and surface stone cover were significantly related to the relative abundance of plant functional types across the gradient. Tussocks and thorns/spines were abundant in lower altitudinal ranges in response to herbivory and drought while rhizomes and rosettes were abundant at higher altitudes in response to the cold. Generally our results show that topographic attributes (altitude and slope) as well as soil organic carbon play an important role in differentiating the relative abundance of plant functional types in the investigated gradient. Thus, considering specific plant functional types would provide a better understanding of the ecological patterns of vegetation and their response to environmental gradients in tropical regions of Africa prone to drought.
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Jacob, Staffan, and Delphine Legrand. "Phenotypic plasticity can reverse the relative extent of intra- and interspecific variability across a thermal gradient." Proceedings of the Royal Society B: Biological Sciences 288, no. 1953 (June 30, 2021): 20210428. http://dx.doi.org/10.1098/rspb.2021.0428.
Abstract:
Intra- and interspecific variability can both ensure ecosystem functions. Generalizing the effects of individual and species assemblages requires understanding how much within and between species trait variation is genetically based or results from phenotypic plasticity. Phenotypic plasticity can indeed lead to rapid and important changes of trait distributions, and in turn community functionality, depending on environmental conditions, which raises a crucial question: could phenotypic plasticity modify the relative importance of intra- and interspecific variability along environmental gradients? We quantified the fundamental niche of five genotypes in monocultures for each of five ciliate species along a wide thermal gradient in standardized conditions to assess the importance of phenotypic plasticity for the level of intraspecific variability compared to differences between species. We showed that phenotypic plasticity strongly influences trait variability and reverses the relative extent of intra- and interspecific variability along the thermal gradient. Our results show that phenotypic plasticity may lead to either increase or decrease of functional trait variability along environmental gradients, making intra- and interspecific variability highly dynamic components of ecological systems.
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Bocquet, F., D. Helmig, B. A. Van Dam, and C. W. Fairall. "Evaluation of the flux gradient technique for measurement of ozone surface fluxes over snowpack at Summit, Greenland." Atmospheric Measurement Techniques Discussions 4, no. 1 (February 14, 2011): 1021–59. http://dx.doi.org/10.5194/amtd-4-1021-2011.
Abstract:
Abstract. A multi-step procedure for investigating ozone surface fluxes over polar snow by the tower gradient method was developed and evaluated. These measurements were then used to obtain four months of turbulent ozone flux data at the Summit research camp located in the center of the Greenland ice shield. Turbulent fluxes were determined by the aerodynamic gradient method incorporating tower measurements of (a) ozone gradients measured by commercial ultraviolet absorption analyzers, (b) ambient temperature gradients using aspirated thermocouple sensors, and (c) wind speed gradients determined by cup anemometers. All gradient instruments were regularly inter-compared by bringing sensors or inlets to the same measurement height. The developed protocol resulted in an uncertainty on the order of 0.1 ppbv for 30-min averaged ozone gradients that were used for the ozone flux calculations. This protocol facilitated a lower sensitivity threshold for the ozone flux determination of −8 × 10−3 μg m−2 s−1, respectively ~0.01 cm s−1 for the ozone deposition velocity for typical environmental conditions encountered at Summit. Uncertainty in the 30-min ozone exchange measurements (evaluated by the Monte Carlo statistical approach) was on the order of 10−2 cm s−1. This uncertainty typically accounted to ~20–100% of the ozone exchange velocities that were determined. These measurements are among the most sensitive ozone deposition determinations reported to date. This flux experiment, deployed at Summit for a period of four months, allowed for measurements of the relatively low ozone uptake rates encountered for polar snow, and thereby the study of their environmental and seasonal dependencies.
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Bocquet, F., D. Helmig, B. A. Van Dam, and C. W. Fairall. "Evaluation of the flux gradient technique for measurement of ozone surface fluxes over snowpack at Summit, Greenland." Atmospheric Measurement Techniques 4, no. 10 (October 25, 2011): 2305–21. http://dx.doi.org/10.5194/amt-4-2305-2011.
Abstract:
Abstract. A multi-step procedure for investigating ozone surface fluxes over polar snow by the tower gradient method was developed and evaluated. These measurements were then used to obtain five months (April–August 2004) of turbulent ozone flux data at the Summit research camp located in the center of the Greenland ice shield. Turbulent fluxes were determined by the gradient method incorporating tower measurements of (a) ozone gradients measured by commercial ultraviolet absorption analyzers, (b) ambient temperature gradients using aspirated thermocouple sensors, and (c) wind speed gradients determined by cup anemometers. All gradient instruments were regularly inter-compared by bringing sensors or inlets to the same measurement height. The developed protocol resulted in an uncertainty on the order of 0.1 ppbv for 30-min averaged ozone gradients that were used for the ozone flux calculations. This protocol facilitated a lower sensitivity threshold for the ozone flux determination of ∼8 × 10−3μg m−2 s−1, respectively ∼0.01 cm s−1 for the ozone deposition velocity for typical environmental conditions encountered at Summit. Uncertainty in the 30-min ozone exchange measurements (evaluated by the Monte Carlo statistical approach) was on the order of 10−2 cm s−1. This uncertainty typically accounted to ~20–100% of the ozone exchange velocities that were determined. These measurements are among the most sensitive ozone deposition determinations reported to date. This flux experiment allowed for measurements of the relatively low ozone uptake rates encountered for polar snow, and thereby the study of their environmental and spring-versus-summer dependencies.
31
Wang, Qiming, Kun Yang, Lixiao Li, and Yanhui Zhu. "Assessing the Terrain Gradient Effect of Landscape Ecological Risk in the Dianchi Lake Basin of China Using Geo-Information Tupu Method." International Journal of Environmental Research and Public Health 19, no. 15 (August 5, 2022): 9634. http://dx.doi.org/10.3390/ijerph19159634.
Abstract:
The assessment of landscape ecological risk (LER) in different terrain gradients is beneficial to ecological environmental protection and risk management in different terrain gradients. Due to the impact of urban expansion, the landscape pattern of the Dianchi Lake basin (DLB) changed obviously, resulting in significant spatial difference of LER. At present, the LER assessment of the DLB is not clear, and the evolution mechanism of LER in different terrain gradients has not been revealed. Based on the LER assessment model, the geo-information Tupu method, the terrain niche gradient, and distribution index, this paper analyzed the LER and its terrain gradient effect in the DLB of China. The conclusions are as follows: (1) Since 1995, the land use type has mainly changed from grassland and cultivated land to construction land in the DLB of China. (2) The LERs in the DLB of China were mainly low, med low, and med high due to the transformation of land use type. The dominance distribution of the low and high LER was obviously constrained by terrain gradient. While the dominance distribution of med-low LER expanded to med-high terrain gradient, the dominance distribution of the med-high LER decreased to med-low terrain gradient. (3) The Tupu LERs were mainly a stable type of “medium” risk and anaphase change type of “med-high to medium” risk. The dominant distribution regions of the stable type, the prophase change type, and the continuous change type were relatively stable; the anaphase and middle change type expanded to the higher terrain gradient, and the repeated change type decreased to the med-high terrain gradient. In the process of ecological risk management and protection in the DLB, attention should be paid to the water area structure and LER control in med-high and high terrain gradients.
32
Qi, Rui, Xiayan Zhou, Zihao Li, Yongzhong Ye, Zhiliang Yuan, Fengqin Liu, Yizhen Shao, Dongwei Wei, and Yun Chen. "Plant Diversity Distribution along an Urbanization Gradient and Relationships with Environmental Factors in Urban Agglomerations of Henan Province, China." Diversity 16, no. 1 (January 15, 2024): 53. http://dx.doi.org/10.3390/d16010053.
Abstract:
Urbanization induces rapid plant environmental modifications, leading to alterations in plant diversity distribution patterns and plant homogenization. However, how plant diversity is distributed along urbanization gradients in regional urban agglomerations and its relationship with environmental factors are not well defined. In three nearby Henan Province Chinese cities—Zhengzhou, Kaifeng, and Zhongmu—along an urbanization gradient, the distribution pattern of plant diversity was quantified. Both native and non-native plants found in urban green spaces were taken into consideration. A total of 176 plant quadrats were selected and separated into three urbanization gradient types using space-constrained hierarchical clustering: urban core, urban suburb, and urban outskirt. Polynomial fitting was used to characterize the spatial distribution patterns of plants along the urbanization gradient, and Pearson correlation and the Mantel test were employed to examine the effects of environmental factors, including longitude, latitude, altitude, distance from the urban center, temperature, and illumination, on plant diversity. A total of 313 vascular plant species, comprising 137 woody species and 176 herbaceous species, were examined. Along the three urbanization gradients, remarkable variations in plant diversity for woody and herbaceous species were observed. The spatial patterns of plant diversity were consistent across cities, whereas woody plants and herbaceous plants displayed the opposite behavior. Distance to the city center and temperature were the most substantial environmental effect factors for the diversity of woody plants, whereas light factors had a major impact on herbaceous plants. These findings show different life-type plants are affected differently by urbanization, and they offer managers and planners a recommendation for increasing urban plant diversity by executing various interventions throughout the urban gradient.
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Zhu, Chun, Yong Mei Xiong, Xu Dong Ma, Xian Dong Ke, and Zhi Yao Su. "Indicator Species Analysis of Forest Communities along a Disturbance Gradient in Guangzhou, China." Applied Mechanics and Materials 195-196 (August 2012): 1275–82. http://dx.doi.org/10.4028/www.scientific.net/amm.195-196.1275.
Abstract:
In order to reveal the effect of disturbance on species composition and detect indicator species for disturbance gradients, we conducted an investigation of urban forest communities along a disturbance gradient in Guangzhou, China. Species richness in the tree layer and understory had no significant difference among disturbance gradients, but Simpson index, Shannon-Weiner index and Evenness index varied significantly.species diversity index decreased with disturbance gradient. Multi-Response Permutation Procedures (MRPP) revealed high significance in species composition of both tree and understory layer among different disturbance gradients. Twelve species from the tree layer and 25 from the understory were detected to characterize the forest communities with a certain disturbance regime by Indicator Species Analysis (ISA). Indicator species help enhance our understanding of species-environment relationship, and the ecological response of indicator species to disturbance can be used for monitoring forest environmental change.
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Tattersall, Glenn J., and Robert G. Boutilier. "Behavioural oxy-regulation by cold-submerged frogs in heterogeneous oxygen environments." Canadian Journal of Zoology 77, no. 6 (October 10, 1999): 843–50. http://dx.doi.org/10.1139/z99-049.
Abstract:
Amphibians overwintering in ice-covered aquatic environments encounter levels of hypoxia that present significant challenges to the maintenance of aerobic metabolism. Earlier laboratory experiments showed that cold-submerged frogs will seek out lower temperatures when confronted with severe hypoxia. This so-called behavioural hypothermia response effectively reduces the aerobic metabolic rate and thereby minimises the lactic acidosis associated with oxygen lack. The results of these previous experiments suggest that frogs overwintering in hypoxic environments have the capacity to exploit thermal gradients under the ice to forestall the onset of anaerobiosis. What is not yet known is whether overwintering frogs can detect and therefore react to the large isothermal oxygen gradients that also exist under the ice. To determine the behavioural response of frogs to dissolved oxygen, the movements of submerged animals were followed for 6 h in an aquatic chamber that presented a linear horizontal oxygen gradient (14-130 mmHg) at two constant temperatures (1.5 and 7°C). At both temperatures, frogs spent significantly less time in regions of the tank that were hypoxic than they did in the same regions when no oxygen gradient was present. Submerged frogs also showed an overall preference for oxygen levels above their critical oxygen partial pressures for the aerobic metabolic rate (41 mmHg at 1.5°C and 76 mmHg at 7°C). Thus, cold-submerged frogs not only respond to oxygen gradients, but they do so in a fashion that favours oxygen uptake and aerobic metabolism. This "behavioural oxy-regulation," although slow-acting, would appear to be adequate for frogs responding to the progressively developing oxygen and temperature gradients in their natural overwintering environments.
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Scott, D. "Dryland legumes: perspectives and problems." NZGA: Research and Practice Series 11 (January 1, 2003): 27–36. http://dx.doi.org/10.33584/rps.11.2003.2996.
Abstract:
The different perspectives or concepts involved in developing legumes for dryland pastoral systems is commented on in relation to: N-fixation versus animal feed; root nodule bacteria requirements; large introduced legume flora compared with indigenous; species niche in relation to environmental gradients of moisture, temperature, fertility, and grazing; species adaptation along the decreasing fertility gradient from fine-root nutrient scavenging grasses, N-fixers, mycorrhiza, and proteoid roots; interaction of N- fixation with soil organic matter; establishment; determinants of pastures legume composition; and the possible role of allelopathy. Key words: dryland, environmental gradients, legumes, N-fixation, pasture composition
36
Ebale, Marsh Reginald Bico, Jonathan Ogayon Hernandez, and Crusty Estoque Tinio. "Leaf Traits of Parashorea malaanonan Along Elevational Gradient in Mount Makiling Forest Reserve, Philippines." Jurnal Sylva Lestari 12, no. 1 (November 17, 2023): 38–53. http://dx.doi.org/10.23960/jsl.v12i1.798.
Abstract:
Studying leaf trait variation and relationships along elevational gradients will enhance our understanding of how plants respond to changing environmental conditions. Thus, we analyzed the leaf traits variation in ecologically and economically important Parashorea malaanonan and the potential influence of environmental covariables (rainfall, relative humidity, and air temperature) on leaf traits along an elevational gradient in Mount Makiling Forest Reserve (MMFR). Three sampling sites were selected based on elevation, i.e., low (400–500 masl), mid (500–600 masl), and high (> 600 masl). The leaf samples were collected from seedlings, saplings, and adult trees of P. malaanonan. There was no significant variation in most of the measured leaf traits, leaf area (LA), specific leaf area (SLA), leaf thickness (LT), leaf length-to-width ratio (L:W) across sampling sites, except vein density (VD). The SLA and LT at high elevations are significantly and negatively correlated (r2 = 0.7396). The environmental covariables had a significant (p < 0.05) impact on the leaf traits of P. malaanonan. The observed variation in some leaf traits may have been influenced by the elevation gradient and its associated environmental conditions. Thus, P. malaanonan may have developed adaptive mechanisms to cope with the changing environment. Keywords: conservation, elevational gradients, environmental variables, leaf traits, Parashorea malaanonan
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Xiao, Li, Jialiang Zhang, Wei Huang, Juli Carrillo, Evan Siemann, and Jianqing Ding. "Tallow tree allocates contrasting secondary chemicals in response to varying environments along elevational gradients." Journal of Plant Ecology 13, no. 3 (April 3, 2020): 295–303. http://dx.doi.org/10.1093/jpe/rtaa014.
Abstract:
Abstract Aims Understanding how tree species regulate multiple types of secondary chemicals along elevational gradients is critical for elucidating the physiological and ecological strategies of plants in response to varying biotic and/or abiotic environments. This study aims to examine how Chinese tallow tree (Triadica sebifera) allocates resources to the production of different secondary chemicals in response to varying environments across elevational gradients. Methods We conducted field surveys of different herbivore feeding guilds and their damage rates on Chinese tallow trees along an elevational gradient in China and measured secondary chemicals (tannins and flavonoids) in damaged and undamaged leaves. Important Findings The odds of a leaf being damaged (chewing or scarring) decreased with elevation. Flavonoid concentrations increased with elevation in undamaged leaves but decreased with elevation in damaged leaves, with quercitrin contributing most strongly to this pattern, likely as results of plant responding to changing biotic or abiotic stresses along elevational gradients. Tannin concentrations did not vary with elevation, so undamaged leaves had relatively lower tannin to flavonoid ratios at high elevation than at low elevation. Our study reveals variation in herbivory and contrasting trends in plant secondary metabolism along an elevation gradient and highlights the importance of simultaneously considering multiple types of secondary chemicals in plant physiological and ecological strategies.
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Eilertsen, O. "Vegetation patterns and structuring processes in coastal shell-beds at Akerøya, Hvaler, SE Norway." Sommerfeltia 12, no. 1 (June 1, 1991): 1. http://dx.doi.org/10.2478/som-1991-0001.
Abstract:
Abstract The vegetation of shell-beds is studied in an island on the coast of Skagerak, SE Norway. Within this restricted area 125 sample plots, 1 m2 each, were distributed by a restricted random procedure. Frequency in subplots and percentage cover were used for estimation of species abundance. A set of 33 environmental variables was obtained from each sample plot. Ecological gradients corresponding to the main vegetational gradients are identified by means of DCA ordination results correlated with environmental data. DCA ordination results are further interpreted by the use of an earlier classification of the vegetation and by application of Grime’s strategy concept. The following complex gradients were recognized: ( 1) the primary successional gradient, influenced by variables dependent on site age, e.g. elevation, distance from the sea, and rate of decomposition of mollusc shells, (2) the secondary successional gradient, from open meadow vegetation via open shrub vegetation to dense shrub vegetation, highly correlated with variables independent of site age, e.g intensity of grazing, (3) the nutrient availability gradient, and (4) the soil moisture gradient. Interpretation of relations between coenoclines and environmental variables was performed by Kendall rank correlation and relationships among ecological variables analysed by PCA ordination. Direct gradient analysis by rh-DCCA is used as a supplement to DCA. The ratio between the rh-DCCA eigenvalue of the first ordination axis and the corresponding eigenvalue of the first residual (unconstrained) axis is used to quantify the importance of each environmental variable. The performed multivariate analyses show that the successional pathways on shell-bed shores are dependent on the grazing pressure. The relative importance of the following structuring processes is discussed: (1) interspecific interaction (competition, coexistence and facilitation), (2) destabilizing factors (disturbance and fluctuations), (3) stress, and (4) chance. Ordination and association analyses shows that Juniperus communis is the most important structuring species in the material. Grazing is necessary to reduce overgrowth by junipers and to maintain a high species diversity. The field data are used for inspection of the performance of different rescaling and detrending options, available with DCA ordination. Non-linear rescaling appears to be less influenced by deviant sample plots as compared to linear rescaling, and the S.D. units of the axes produced by non-linear rescaling are considered better interpretable in terms of a unimodal model of species responses to ecological gradients. Available options for detrending by polynomials are shown to be inferior to the detrending by segments option, as polynomial detrending may impose a polynomial distortion on the point configuration in the ordination space.
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Økland, R. H., and O. Eilertsen. "Vegetation-environment relationships of boreal coniferous forests in the Solhomfjell area, Gjerstad, S Norway." Sommerfeltia 16, no. 1 (March 1, 1993): 1–259. http://dx.doi.org/10.2478/som-1993-0002.
Abstract:
Abstract The understory vegetation (vascular plants, bryophytes and lichens) in an area dominated by boreal coniferous forests is subjected to detailed ecological analysis. Two hundred meso sample plots (1 m2) are used as basis for vegetation sampling, and provided with measurements of 33 environmental variables. Species abundance is recorded as frequency in 16 subplots. Parallel DCA and 2-dimensional LNMDS ordinations of meso sample plots were largely identical, both provided two coenocline axes interpretable in ecological terms. The first axis is interpreted as the response to a broad-scale topographical complex-gradient, made up of two independent complex-gradients; (1) a topography-soil depth complex-gradient in the pine forest (running from lichen-rich pine forests to submesic Vaccinium myrtillus-dominated spruce forests), and (2) a complex-gradient in soil nutrient status in the spruce forest. The second axis, mainly affecting the species composition of the bottom layer, is interpreted as a fine-scale paludification gradient. The causes of variation along these gradients are discussed: Desiccation tolerance is considered to act directly on the physiology of vascular plant species, setting their limits towards xeric sites. Similarly, cryptogams with optima in the more mesic sites are considered to be excluded from drier sites by physiological tolerance. Limits of cryptogams towards more mesic sites are, however, considered to be set by competitive ability (growth rates) in accordance with the competitive hierarchy theory. N availability is assumed to be the most important factor for differentiation of vascular plants along the nutrient gradient, while bryophytes are expected to respond to a complex of factors, including structural properties of the humus layer. Increasing N accumulation in the humus towards xeric sites may indicate oversaturation due to deposition of airborne NO3- or NH>4 +. Fine-scale paludification, mainly of a soligenous type, occurred in sloping terrain with shallow soil. The cryptogams apparently make up a competitive hierarchy also along the paludification gradient. No other coenoclines could be identified by analysis of 0.0625 m2 micro sample plots, most probably because the response of vegetation to micro-scale environmental gradients (probably most important: the variation in microtopography) not essentially different from the meso-scale gradients, and because the importance of random processes increase towards finer scales. Structuring processes are discussed with reference to the observed patterns. The lack of a closed bottom layer in almost all sample plots is considered a strong indication of high importance of fine-scale disturbance and density-independent mortality in the investigated system, while interspecific competition is of lower importance. The methodology in vegetation ecological studies is discussed with particular reference to monitoring. The potential of an integrated concept using permanent plots, parallel investigation of vegetation and environmental parameters, and gradient analysis, is stressed. Several suggestions for future studies, based on this integrated approach, are made.
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Lancaster, Jill, Barbara J. Downes, and Alena Glaister. "Interacting environmental gradients, trade-offs and reversals in the abundance - environment relationships of stream insects: when flow is unimportant." Marine and Freshwater Research 60, no. 3 (2009): 259. http://dx.doi.org/10.1071/mf08226.
Abstract:
Flow is often presumed to determine the distribution of stream invertebrates across stream beds. When temperatures are high, however, dissolved oxygen (DO) and its interactions with other environmental gradients may be more important. Field surveys were carried out in summer at two sites in a sand-bed stream in south-east Australia. Using quantile regression, we quantified the abundance–environment relationships of a caenid mayfly and an ecnomid caddisfly, and determined whether DO, fine detritus or velocity was the dominant limiting variable, and to gain insight into the causal mechanisms. Local densities of caenids were driven by food resources (detritus) at a site with a short DO gradient. The relationship was completely reversed where long DO and detritus gradients interacted, and here DO appeared to limit density. Densities of ecnomids were limited by prey-rich detritus patches at both sites. The velocity gradient did not explain the distribution patterns in either species. Ecnomid diet altered with changes in the spatial distribution of caenids between sites; caenids were the dominant prey at one site, but proportionately fewer were consumed where there was a negative spatial overlap of predators and prey. These results show that invertebrate responses to environmental gradients can be complex and that flow may be unimportant.
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Sabel, Clive E., John F. Pearson, Deborah F. Mason, Ernest Willoughby, David A. Abernethy, and Bruce V. Taylor. "The latitude gradient for multiple sclerosis prevalence is established in the early life course." Brain 144, no. 7 (March 11, 2021): 2038–46. http://dx.doi.org/10.1093/brain/awab104.
Abstract:
Abstract The strongest epidemiological clue that the environment at the population level has a significant impact on the risk of developing multiple sclerosis is the well established, and in many instances, increasing latitudinal gradient of prevalence, incidence and mortality globally, with prevalence increasing by up to 10-fold between the equator and 60° north and south. The drivers of this gradient are thought to be environmental with latitude seen as a proxy for ultraviolet radiation and thus vitamin D production; however, other factors may also play a role. Several important questions remain unanswered, particularly when in the life course is the gradient established, does lifetime migration mitigate or exacerbate previously reported latitude gradients at location of diagnosis, and do factors such as sex or multiple sclerosis disease phenotype influence the timing or significance of the gradient? Utilizing lifetime residence calendars collected as part of the New Zealand National Multiple Sclerosis Prevalence Study, we constructed lifetime latitudinal gradients for multiple sclerosis from birth to prevalence day in 2006 taking into account migration internally and externally and then analysed by sex and multiple sclerosis clinical course phenotype. Of 2917 individuals living in New Zealand on prevalence day, 7 March 2006, with multiple sclerosis, 2127 completed the life course questionnaire and of these, 1587 were born in New Zealand. All cohorts and sub-cohorts were representative of the overall multiple sclerosis population in New Zealand on prevalence day. We found that the prevalence gradient was present at birth and was, in fact, stronger than at census day, and the slope of the gradient persisted until the age of 12 before gradually declining. We found that internal and external migration into New Zealand had little, if any, effect on the gradient except to decrease the significance of the gradient somewhat. Finally, we found as we had reported previously, that the lifetime prevalence gradients were largely driven by females with relapse onset multiple sclerosis. These findings confirm for the first time the importance of early life environmental exposures in the risk of multiple sclerosis indicating strongly that exposures as early as in utero and at birth drive the latitudinal gradient. Consequently, prevention studies should be focused on high-risk individuals and populations from the earliest possible time points especially, when appropriate, on females.
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Marchant, R., LA Barmuta, and BC Chessman. "Influence of sample quantification and taxonomic resolution on the ordination of macroinvertebrate communities from running waters in Victoria, Australia." Marine and Freshwater Research 46, no. 2 (1995): 501. http://dx.doi.org/10.1071/mf9950501.
Abstract:
The influence of sample quantification and taxonomic resolution on the ordination of macroinvertebrate communities from nine Victorian rivers was examined by progressively reducing the degree of detail in the original data (species level, quantitative). Five additional data sets were created that consisted of binary (presence or absence) data on species, quantitative or binary data on families, and quantitative data on PET (plecopteran, ephemeropteran and trichopteran) species or families. Ordinations were performed with detrended correspondence analysis (DCA) and semi-strong hybrid multi-dimensional scaling (SSH). With both ordination techniques, the ordinations of each data set (including the original) revealed the same three underlying gradients. An altitudinal gradient consistently achieved the highest correlations with the ordinations (r = 0.71-0.93), followed by a substratum gradient (r = 0.50-0.88) and a combined pH and conductivity gradient (r = 0.47-0.76). Each of the five less-complete data sets thus provides an adequate degree of detail for ordination analysis and subsequent interpretation of environmental gradients.
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Zhang, Zhonghua, Li Ma, Xiaoyuan Yang, Qian Zhang, Yandi She, Tao Chang, Hongye Su, et al. "Biodiversity and Ecosystem Function under Simulated Gradient Warming and Grazing." Plants 11, no. 11 (May 27, 2022): 1428. http://dx.doi.org/10.3390/plants11111428.
Abstract:
Biodiversity and ecosystem functions and their relationship with environmental response constitute a major topic of ecological research. However, the changes in and impact mechanisms of multi-dimensional biodiversity and ecosystem functions in continuously changing environmental gradients and anthropogenic activities remain poorly understood. Here, we analyze the effects of multi-gradient warming and grazing on relationships between the biodiversity of plant and soil microbial with productivity/community stability through a field experiment simulating multi-gradient warming and grazing in alpine grasslands on the Tibetan Plateau. We show the following results: (i) Plant biodiversity, soil microbial diversity and community productivity in alpine grasslands show fluctuating trends with temperature gradients, and a temperature increase below approximately 1 °C is beneficial to alpine grasslands; moderate grazing only increases the fungal diversity of the soil surface layer. (ii) The warming shifted plant biomass underground in alpine grasslands to obtain more water in response to the decrease in soil moisture caused by the temperature rise. Community stability was not affected by warming or grazing. (iii) Community stability was not significantly correlated with productivity, and environmental factors, rather than biodiversity, influenced community stability and productivity.
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Fadziso, Takudzwa. "Overcoming the Vanishing Gradient Problem during Learning Recurrent Neural Nets (RNN)." Asian Journal of Applied Science and Engineering 9, no. 1 (December 31, 2020): 197–208. http://dx.doi.org/10.18034/ajase.v9i1.41.
Abstract:
Artificial neural nets have been equipped with working out the difficulty that arises as a result of exploding and vanishing gradients. The difficulty of working out is worsened exponentially particularly in deep learning understanding. With gradient-oriented learning approaches the up-to-date error gesture has to “flow back in time” throughout the response links to previously feedbacks for designing suitable feedback storage. To address the gradient vanishing delinquent, adaptive optimization approaches are given. With adaptive learning proportion, the adaptive gradient classifier switches the constraint for substantial hyper factor fine-tuning. Based on the numerous outstanding advances that recurrent neural nets (RNN) have added in the erstwhile in the field of Deep Learning. The objective of this paper is to have a concise synopsis of this evolving topic, with a focus on how to over the vanishing gradient problems during learning RNN. There are four types of methods adopted in this study to provide solutions to the gradient vanishing problem and they include approaches that do not employ gradients; approaches that enforce larger gradients, approaches that work at a higher level, and approaches that make use of unique structures. The inaccuracy flow for gradient-oriented recurrent learning approaches was hypothetically examined. This analysis exhibited that learning to link long-term lags can be problematic. Cutting-edge approaches to solving the gradient vanishing difficulty were revealed, but these methods have serious disadvantages, for example, practicable only for discrete data. The study deep-rooted that orthodox learning classifiers for recurrent neural networks are not able to learn long-term lag complications at a reasonable interval.
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Lyu, Lixin, Susanne Suvanto, Pekka Nöjd, Helena M. Henttonen, Harri Mäkinen, and Qi-Bin Zhang. "Tree growth and its climate signal along latitudinal and altitudinal gradients: comparison of tree rings between Finland and the Tibetan Plateau." Biogeosciences 14, no. 12 (June 23, 2017): 3083–95. http://dx.doi.org/10.5194/bg-14-3083-2017.
Abstract:
Abstract. Latitudinal and altitudinal gradients can be utilized to forecast the impact of climate change on forests. To improve the understanding of how these gradients impact forest dynamics, we tested two hypotheses: (1) the change of the tree growth–climate relationship is similar along both latitudinal and altitudinal gradients, and (2) the time periods during which climate affects growth the most occur later towards higher latitudes and altitudes. To address this, we utilized tree-ring data from a latitudinal gradient in Finland and from two altitudinal gradients on the Tibetan Plateau. We analysed the latitudinal and altitudinal growth patterns in tree rings and investigated the growth–climate relationship of trees by correlating ring-width index chronologies with climate variables, calculating with flexible time windows, and using daily-resolution climate data. High latitude and altitude plots showed higher correlations between tree-ring chronologies and growing season temperature. However, the effects of winter temperature showed contrasting patterns for the gradients. The timing of the highest correlation with temperatures during the growing season at southern sites was approximately 1 month ahead of that at northern sites in the latitudinal gradient. In one out of two altitudinal gradients, the timing for the strongest negative correlation with temperature at low-altitude sites was ahead of treeline sites during the growing season, possibly due to differences in moisture limitation. Mean values and the standard deviation of tree-ring width increased with increasing mean July temperatures on both types of gradients. Our results showed similarities of tree growth responses to increasing seasonal temperature between latitudinal and altitudinal gradients. However, differences in climate–growth relationships were also found between gradients due to differences in other factors such as moisture conditions. Changes in the timing of the most critical climate variables demonstrated the necessity for the use of daily-resolution climate data in environmental gradient studies.
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Karpowicz, Maciej, and Jolanta Ejsmont-Karabin. "Influence of environmental factors on vertical distribution of zooplankton communities in humic lakes." Annales de Limnologie - International Journal of Limnology 54 (2018): 17. http://dx.doi.org/10.1051/limn/2018004.
Abstract:
The influence of vertical environmental gradients on zooplankton communities was studied in five humic lakes with the high availability of food resources (phytoplankton and bacterioplankton) and low fish pressure. The factors that inhibit the development of large zooplankton in humic lakes are currently widely debated. We have found that relatively productive humic lakes do not offer many niches for zooplankton because of the sharp thermal gradient which results in a shallow layer of oxygenated waters. The results of this study indicated that different taxonomic groups of zooplankton are determined by a different set of environmental variables. This phenomenon explains very low species richness of zooplankton and a possibility of their coexistence in the narrow oxygenated layer. We concluded that due to sharp thermal gradient in humic lakes biomass of herbivores may be reduced which could promote development of phytoplankton.
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Holt, Emily A., Bruce McCune, and Peter Neitlich. "Macrolichen communities in relation to soils and vegetation in the Noatak National Preserve, Alaska." Botany 87, no. 3 (March 2009): 241–52. http://dx.doi.org/10.1139/b08-142.
Abstract:
Macrolichen community structure and its relation to environment in the Noatak National Preserve, Alaska, is described using a two-way stratified random sample. We found 201 macrolichen taxa. Two primary gradients in lichen species composition were related to substrate pH and vegetation physiognomy, grading from forests to high alpine communities. Site characteristics associated with the first community gradient are soil moisture and exposure. Both ends of this gradient, including protected forests and densely shrubby sites at one end and exposed, high elevation alpine sites at the other end, are relatively dry and well-drained. The mid-region of this gradient consists of mesic, lowland tundra habitats. The second gradient, related to substrate pH, is driven by the presence of Sphagnum moss contrasting with calcareous soils and bedrock. Combining these two gradients of lichen community composition, we found six groups of plots using two-way cluster analysis. Further, division of macrolichen species occurring in five or more plots yielded seven species groups, based on a combination of environmental factors and species distribution characteristics. This snapshot of macrolichen communities in Arctic Alaska serves as an important baseline for future comparisons to environments altered by changing climate and land use.
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Lowen, J. Benjamin, Devorah R. Hart, Ryan R. E. Stanley, Sarah J. Lehnert, Ian R. Bradbury, and Claudio DiBacco. "Assessing effects of genetic, environmental, and biotic gradients in species distribution modelling." ICES Journal of Marine Science 76, no. 6 (April 8, 2019): 1762–75. http://dx.doi.org/10.1093/icesjms/fsz049.
Abstract:
Abstract To develop more reliable marine species distribution models (SDMs), we examine how genetic, climatic, and biotic interaction gradients give rise to prediction error in marine SDM. Genetic lineages with distinct ecological requirements spanning genetic gradients have yet to be treated separately in marine SDM, which are often constrained to modeling the potential distribution of one biological unit (e.g. lineage or species) at a time. By comparing SDM performance for the whole species or where observation and predictions were partitioned among geographically discontinuous genetic lineages, we first identified the appropriate biological unit for modeling sea scallop. Prediction errors, in particular contiguous omissions at the northern range margins were effectively halved in genetic lineage SDM (Total error=15%) verses whole species SDM. Remaining SDM prediction error was strongly associated with: i) Sharp climatic gradients (abrupt and persistent spatial shifts in limiting temperatures) found within continental shelf breaks and bottom channels. ii) A biotic gradient in the predation of sea scallop juveniles by the sand star within the Hudson Shelf USA. Our findings highlight how the accuracy of marine SDM is dependent on capturing the appropriate biological unit for modeling (e.g. lineages rather than species) and adequately resolving limiting abiotic and biotic interaction gradients.
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Gehrke, PC. "Clinotactic responses of Larval Silver Perch (Bidyanus bidyanus) and Golden Perch (Macquaria ambigua) to simulated environmental gradients." Marine and Freshwater Research 41, no. 4 (1990): 523. http://dx.doi.org/10.1071/mf9900523.
Abstract:
Larval silver perch (Bidyanus bidyanus) and golden perch (Macquaria ambigua) were subjected to gradients of light, depth, flow and wood leachate from river red gum (Eucalyptus camaldulensis) as well as a control treatment with no gradient. Both species were strongly attracted to light, while golden perch larvae were also attracted to river red gum and were carried downstream by water flow. Neither species displayed any response to depth. Gradient responses of silver perch were significantly more variable (P < 0.05) than those of golden perch, which may result in silver perch larvae being more widely distributed in floodplain habitats. Golden perch larvae may be more closely associated with inundated river red gum than silver perch larvae.
50
Jiang, Hongchen, Liuqin Huang, Ye Deng, Shang Wang, Yu Zhou, Li Liu, and Hailiang Dong. "Latitudinal Distribution of Ammonia-Oxidizing Bacteria and Archaea in the Agricultural Soils of Eastern China." Applied and Environmental Microbiology 80, no. 18 (July 7, 2014): 5593–602. http://dx.doi.org/10.1128/aem.01617-14.
Abstract:
ABSTRACTThe response of soil ammonia-oxidizing bacterial (AOB) and archaeal (AOA) communities to individual environmental variables (e.g., pH, temperature, and carbon- and nitrogen-related soil nutrients) has been extensively studied, but how these environmental conditions collectively shape AOB and AOA distributions in unmanaged agricultural soils across a large latitudinal gradient remains poorly known. In this study, the AOB and AOA community structure and diversity in 26 agricultural soils collected from eastern China were investigated by using quantitative PCR and bar-coded 454 pyrosequencing of theamoAgene that encodes the alpha subunit of ammonia monooxygenase. The sampling locations span over a 17° latitude gradient and cover a range of climatic conditions. TheNitrosospiraandNitrososphaerawere the dominant clusters of AOB and AOA, respectively; but the subcluster-level composition ofNitrosospira-related AOB andNitrososphaera-related AOA varied across the latitudinal gradient. Variance partitioning analysis showed that geography and climatic conditions (e.g., mean annual temperature and precipitation), as well as carbon-/nitrogen-related soil nutrients, contributed more to the AOB and AOA community variations (∼50% in total) than soil pH (∼10% in total). These results are important in furthering our understanding of environmental conditions influencing AOB and AOA community structure across a range of environmental gradients.