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Экология водотоков

Гидрология и разнообразие водотоков.

Структура турбулентности в водотоках.


Authors: Sandjensen-K Mebus-JR

Микромасштабная структура подвижности воды в речных зарослях макрофитов.

Fine-Scale Patterns of Water Velocity Within Macrophyte Patches in Streams

OIKOS 1996, Vol 76, Iss 1, pp 169-180

Abstract:

Rooted macrophytes in temperate lowland streams are often

distributed in monospecific patches which control Row, carbon

fluxes, and the abundance of invertebrates and fish. Small high-

resolution hot-wire probes provided detailed measures of flow

velocities within and around macrophyte patches of four plant

species of contrasting morphologies in Danish streams. Flow

velocity declined rapidly at the surface of the plant patches

and species with large leaf area on bushy shoots (e.g.

Callitriche cophocarpa and Elodea canadensis) reduced the Row

more than species with stream-lined, strap-formed leaves (e.g.

Sparganium emersum). Variable Row-resistance resulted in Row

velocities at 2 cm above the sediment which were Ii-fold lower

inside C. cophocarpa patches than upstream of the parches,

whereas no significant differences in near-bed velocities were

found inside and outside the more open patches of S. emersum.

The reduced velocity within flow-resistant parches remains

sufficiently fast (i.e. <1 cm s(-1)) to prevent carbon depletion

and oxygen accumulation and should be optimal to photosynthesis

and plant growth. The deflected Row is accelerated around the

patches and contributes to form a mosaic of highly variable

plant cover, Bow and substrate conditions. These relations have

important implications for Row resistance, areal expansion of

patches and spatial variability of sediment and invertebrate

composition in streams.

Гидрология водотоков: влияние масштаба.


Authors: Poff-NL

Гидрогеография незарегулированных водотоков США и связь масштаба с некоторыми гидрологическими параметрами.

A Hydrogeography of Unregulated Streams in the United-States and an Examination of Scale-Dependence in Some Hydrological Descriptors

FRESHWATER BIOLOGY 1996, Vol 36, Iss 1, pp 71-91

Abstract:

1. Relatively undisturbed streams in continental U.S.A. were classified according to variation in ten ecologically relevant hydrological characteristics. Measures of flow variability and predictability for average conditions, as well as for low- and high-flow extremes, were extracted from long-term (15-58-year) daily streamflow data for 806 streams.

2. Two groups of sites were analysed: all 806 sites and a subset of 420 'best' sites. For each group, cluster analysis identified ten distinctive stream types, seven permanent and three intermittent. The geographical clustering exhibited by the stream types indicated regional differences in climatic and geological features. A bootstrapping technique applied to the permanent stream classes showed the majority of them were statistically robust.

3. The derived classification of U.S. streams based on ecologically relevant hydrological characteristics provides a comprehensive catalogue of small to mid-size streams that, according to ecological theory, may differ in major aspects of their ecological organization. The classification provides a basis for hypothesis generation and affords an objective framework for matching streams for purposes of comparative ecological investigations.

4. A subset of 118 streams from the ten classification groups was selected to determine whether certain hydrological variables often used by ecologists to make cross-system comparisons are sensitive to the temporal coarseness of the hydrological time series used to derive the variables. The three hydrological variables considered were streamflow predictability, streamflow variability and flood timing.

5. Streamflow predictability (using Colwell's Index) was calculated at daily, weekly, monthly and seasonal time stales. Estimates of predictability showed either no change across time scales, a gradual and consistent increase across time scales, or a maximum value at the monthly time scale. Coefficient of variation of streamflow was calculated at daily, weekly, monthly, seasonal, and annual time steps. Daily values were always greatest for all streams. Some groups showed minimum variability at the monthly scale, others at the seasonal. Timing of daily peak flows could be detected with 50-90% accuracy across stream groups using coarser grain monthly and annual hydrographic data.

6. Inferences about hydrological similarity among streams across broad geographical scales can be sensitive to choice of time scale used in the hydrological characterization.

Влияние масштаба рассмотрения.

Влияние масштаба рассмотрения.


Authors: Lancaster-J

Влияние масштаба на хищничество и нарушения в пятнистой среде.

Scaling the Effects of Predation and Disturbance in a Patchy Environment

OECOLOGIA 1996, Vol 107, Iss 3, pp 321-331

Abstract:

The effects of hydraulic disturbances on the impact of two

predatory benthic invertebrates on their prey were examined in a

stream at two distinct spatial scales. At the scale of small

habitat patches (0.0625 m(2)), hydraulic patch type was an

important determinant of the microdistribution of prey and

predators. Prey abundances were similar across all patch types

at baseflow, but local densities were higher in patches

identified as low-flow refugia after periods of high and

fluctuating flow. The microdistribution pattern of predatory

larvae of a caddisfly, Plectrocnemia conspersa, was similar to

that of its prey, whereas predatory larvae of an alderfly,

Sialis fuliginosa, did not shift their microdistribution

significantly with discharge and were always most abundant in

low-flow refugia. There was little evidence of an aggregative

response of predators with prey, even though both predators and

prey are mobile. Both predator species showed similar patch-

specific patterns of per capita consumption rates: uniform

consumption-rates across hydraulic patch types at low and

moderate flows, but highest in flow refugia during high flows.

Species-specific patterns, however, were apparent in the

magnitude and direction of differences between consumption rates

during disturbance events, and in comparable patches at base

flow: At high flow, consumption rates for P. conspersa were

exaggerated (3.9 times higher) in flow refugia but ''at par'' in

other patches; for S. fuliginosa they were ''at par'' in flow

refugia but reduced in other patches (up to 3.3. times lower).

These differences may be related to species-specific foraging

behaviours (search vs ambush predators) and the influence of

prey movements on feeding success. Using the patch-scale results

only, it is difficult to predict the effects of physical

disturbance on predation intensity at the larger scales of whole

habitats, populations or communities. At the large scale (>200

m(2)), net predator impacts were estimated over the stream

reach, using a spatially explicit model that accounts, in an

additive way, for habitat heterogeneity and patch-specific

responses of predators and prey. The relationship between

predator impact over the whole reach and hydraulic disturbance

differed for the two predators. The predator impact of S.

fuliginosa decreased with increasing hydraulic disturbance, as

predicted by the harsh-benign hypothesis. There was no

directional trend for P. conspersa, however, and maximum

predator impact may occur at intermediate disturbance levels.

For the prey community in this stream, predation pressure from

S. fuliginosa appears to fluctuate directly with the discharge

hydrograph, whereas predation from P. conspersa may be more

persistent. Flow refugia may play a dual role in the sructure of

stream communities by preventing catastrophic mortality of

animals (predators and prey) from physical forces during

disturbances, and by maintaining (or perhaps increasing)

predation pressure. Summing the effects of species interactions

in small habitat patches to the larger scale of a whole stream

reach indicates that the scale of approach influences the

observed patterns and their implied underlying process.


Влияние масштаба рассмотрения.


Authors: Carter-JL Fend-SV Kennelly-SS

Структура сообщества речного макробентоса в трех масштабах местообитания (США).

The Relationships Among 3 Habitat Scales and Stream Benthic Invertebrate Community Structure

FRESHWATER BIOLOGY 1996, Vol 35, Iss 1, pp 109-124

Abstract:

1. The relationships between three habitat scales and lotic

invertebrate species composition were investigated for the 15

540 km(2) Yakima River basin in south-central Washington, U.S.A.

2. The three spatial scales were sample (the sampled

riffle), reach (a length of ten-twenty stream widths) and

segment (a length of stream of nearly uniform slope and valley

form having no change in stream order).

3. Physical variables were highly correlated between scales

and expressed a relationship between altitude, basin form and

small-scale physical structure.

4. Multiple discriminant function analyses indicated that

segment- and reach-scale variables discriminated among species-

defined groups better than sample-scale variables.

5. Species composition varied along a complex altitudinal

gradient of changing basin form and resultant land use.

6. There was no clear relationship between species richness

and altitude on a site basis. However, when viewed at the basin

scale, maximum richness was observed at the transition between

montane and valley sites.


Структура местообитаний, влияние масштаба.


Authors: Robson-BJ

Структура местообитания и сила трофических взаимодействий в быстрой реке - масштабные эффекты.

Habitat Architecture and Trophic Interaction Strength in a River-Riffle - Scale Effects

OECOLOGIA 1996, Vol 107, Iss 3, pp 411-420

Abstract:

Invertebrate algal grazer densities were manipulated in a

temperate river to discover the impact of differences in riffle-

scale architectural complexity on the strength of the trophic

interaction between grazers and epilithic algae. Animal

densities were manipulated by manual removal in architecturally

complex boulder-cobble riffles and simpler bedrock riffles, with

the complexity of smaller-scale architecture held constant.

Responses in algal density were recorded before and after a

month of manipulations, together with grazer colonization rate

and body sizes. The experiment was carried out in winter and

again in summer. The interaction between grazers and algae

differed between habitats and seasons. In winter, when algae

were growing, the more complex riffle-scale architecture in the

boulder-cobble riffles created a refuge from grazing for algae.

This was probably the result of the movement abilities of the

grazers interacting with habitat architecture, and potentially

also due to the control of predatory fish densities by habitat

architecture resulting in greater predation pressure on grazers

in boulder-cobble riffles. Therefore the impact of highly

complex riffle-scale architecture was to weaken the strength of

the trophic interaction between algae and their grazers by

reducing grazer densities, while potentially strengthening the

trophic interaction between grazers and their fish predators.


Разномасштабные факторы, реки США


04.03-04А2.142. Относительное влияние переменных, изучаемых в разных масштабах, на речных микробеспозвоночных в экорегионах США Северные озера и Леса. Relative influence of variables at multiple spatial scales on stream macroinvertebrates in the Northern Lakes and Forest ecoregion, U.S.A. / Weigel Brian M., Wang Lizhu, Rasmussen Paul W., Butcher Jason T., Stewart Paul M., Simon Thomas P., Wiley Michael J. // Freshwater Biol. - 2003. - 48, № 8. - С. 1440_ѕ1461. - Англ.

Изучено 94 р-на в экорегионах Северные озера и Леса, к-рые охватывают штаты Миннесота, Висконсин и Мичиган. Идентифицировали влияние различных факторов на речных макробеспозвоночных в масштабах водосбора, отрезка реки и прибрежья. В масштабах водосборов учитывали растительный покров, геологические особенности и грунтовые воды, в масштабах отдельных отрезков реки _ѕ гидрохимические показатели, морфологию русла и речные биотопы; в масштабах прибрежья _ѕ тип растительного покрова на разных расстояниях от реки. Р-цию микробеспозвоночных оценивали по 22 биоценотическим показателям и относительной численности и присутствия/отсутствия 66 видов. Суммированы данные, полученные в результате исследований в разных пространственных шкалах. Наблюдается иерархия влияния разных масштабов. Переменные в рамках водосборов и отрезков реки одинаково влияют на структурные показатели биоценозов, а на относительную численность таксонов и их присутствие/отсутствие в большей степени влияет переменные в масштабах отдельных участков реки. Полученные данные следует учитывать при реабилитации и менеджменте речных экосистем. США, Wisconsin Dep. of Natural Resources, Bureau of Integrated Sci. Services, 1350 Femrite Dr., Monona, WI 53716, E-mail: brian.weigel@dnr.state.wi.us. Ил. 5. Табл. 4. Библ. 55.



Мультимасштабный анализ, реки Испании


04.03-04А2.145. Мультимасштабное изучение пространственного распределения сообществ речных макробеспозвоночных. Multiscale patterns of spatial variation in stream macroinvertebrate communities / Boyero Luz // Ecol. Res. - 2003. - 18, № 4. - С. 365_ѕ379. - Англ.

В двух горных реках изучали численность, видовое богатство, выровненность, процент поденок, веснянок и ручейников и таксономический состав сообществ макробеспозвоночных в разных пространственных масштабах: трех отрезках реки в каждом речном бассейне, трех перекатах в каждом сегменте, трех участках в каждом перекате и трех пробах в каждом участке. Значимые различия наблюдались гл. обр. в масштабах пробы и переката, однако разные показатели варьировали в разных масштабах различно. Влияние факторов окружающей среды очень велико, но различно в разных пространственных масштабах, в связи с чем для полного изучения структуры макробеспозвоночных необходимы исследования в разных пространственных шкалах. Испания, Dep. de Biodiversidad y Biol. Evolutiva, Museo Nacional de Ciencias Naturales, 28006 Madrid. Email: luz@mncn.csic.es. Ил. 5. Табл. 4. Библ. 24. Прилож. 2.



Влияние масштаба и географии, Н.Зеландия


04.01-04А2.213. Влияние масштаба и географии на связи между составом речного сообщества и ландшафтными характеристиками; описание и прогнозирование. The influence of scale and geography on relationships between stream community composition and landscape variables: Description and prediction / Townsend Colin R., Doledec Sylvain, Norris Richard, Peacock Kathi, Arbuckle Chris // Freshwater Biol. - 2003. - 48, № 5. - С. 768_ѕ785. - Англ.

Проанализированы существующие базы данных по рыбам и макробеспозвоночным в связи с новой ГИС по физическим факторам для установления связи между структурой речных сообществ и физическими факторами, определяемыми на трех уровнях: в масштабе водосбора, отрезка реки и субстрата. Для макробеспозвоночных главную роль играют природные факторы, измеряемые в масштабах водосбора (рельеф, диаметр бассейна и др.), а также тип землепользования (процент пастбищ в прибрежной зоне). Для рыб основное значение имеют также природные факторы, но на более низком уровне, большее влияние оказывает тип землепользования. Географическое местоположение играет роль в изменчивости развития некоторых макробеспозвоночных. Отмечено соответствие данных, полученных путем математических расчетов и наблюдаемых в природе. Новая Зеландия, Zool. Dep., Univ. of Otago, PO Box 56, Dunedin, E-mail: colin.townsend@stonebow.otago.ac.nz. Ил. 3. Табл. 5. Библ. 49.




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