Окружающие ландшафты водотоков

Водотоки: влияние прибрежной растительности

HYDROBIOLOGIA 1994, Vol 294, Iss 1, pp 65-85

Abstract:

Information on the ecology of New Guinea streams is meagre,

and data are needed on the trophic basis of aquatic production

in rivers such as the Sepik in Papua New Guinea which have low

fish yields. This study investigates the relationship between

riparian shading (from savanna grassland to primary rainforest),

algal and detrital food, and macroinvertebrate abundance and

community structure in 6 Sepik River tributary streams. A

particular aim was to elucidate macroinvertebrate community

responses to changes in riparian conditions. All streams

supported diverse benthic communities, but morphospecies

richness (overall total 64) was less than in streams on the

tropical Asian mainland; population densities of benthic

invertebrates, by contrast, were similar to those recorded

elsewhere. Low diversity could reflect limited taxonomic

penetration, but may result from the absence of major groups

(Plecoptera, Heptageniidae, Ephemerellidae, Psephenidae,

Megaloptera, etc.) which occur on the Asian mainland.

Population densities of all 19 of the most abundant

macroinvertebrate taxa varied significantly among the 6 study

streams, but community composition in each was broadly similar

with dominance by Baetidae and (in order of decreasing

importance), Leptophlebiidae, Orthocladiinae, Elmidae and

Hydropsychidae. Principal components analysis (PCA) undertaken

on counts of abundant macroinvertebrate taxa clearly separated

samples taken in two streams from the rest. Both streams

contained high detrital standing stocks and one was completely

shaded by rainforest. Stepwise multiple-regression analysis

indicated that population densities of the majority of abundant

taxa (11 out of 19) across streams (10 samples per stream; n =

60) were influenced by algae and/or detritus, although standing

stocks of these variables were not clearly related to riparian

conditions. When regression analysis was repeated on mean

counts of taxa per stream (dependent variables) versus features

of each stream as a whole (thus n = 6), % shading and detritus

were the independent variables yielding significant regression

models most frequently, but pH, total-nitrogen loads and algae

were also significant predictors of faunal abundance. Further

regression analysis, undertaken separately on samples (n = 10)

from each stream, confirmed the ability of algae and detritus to

account for significant portions of the variance in

macroinvertebrate abundance, but the significance of these

variables varied among streams with the consequence that

responses of individual taxa to algae or detritus was site-

specific.

Community functional organization - revealed by

investigation of macroinvertebrate functional feeding groups

(FFGs) - was rather conservative, and streams were codominated

by collector-gatherers (mean across 6 streams = 43%) and grazers

(36%), followed by filter-feeders (15%) and predators (7%). The

shredder FFG was species-poor and comprised only 0.4% of total

macroinvertebrate populations; shredders did not exceed 2% of

benthic populations in any stream. PCA of FFG abundance data

was characterized by poor separation among streams, although

there was some evidence of clustering of samples from unshaded

sites. The first 2 PCA axes accounted for 84% of the variation

in the data suggesting that the poor separation resulted from

the general similarity of FFG representation among streams.

Although stepwise multiple-regression analysis indicated that

algae and detritus accounted for significant proportions of the

variations in population density and relative abundance of some

FFGs, the response of community functional organization to

changes in riparian conditions and algal and detrital food base

was weak - unlike the deterministic responses that may be

typical of north-temperate streams.

Приречные ландшафты.

Volume 47 Issue 4 Page 501 - April 2002

Riverine landscapes: taking landscape ecology into the water

JOHN A. WIENS

1.Landscape ecology deals with the influence of spatial pattern on ecological

processes. It considers the ecological consequences of where things are located in

space, where they are relative to other things, and how these relationships and their

consequences are contingent on the characteristics of the surrounding landscape

mosaic at multiple scales in time and space. Traditionally, landscape ecologists have

focused their attention on terrestrial ecosystems, and rivers and streams have been

considered either as elements of landscape mosaics or as units that are linked to the

terrestrial landscape by flows across boundaries or ecotones. Less often, the

heterogeneity that exists within a river or stream has been viewed as a `riverscape' in

its own right.

2.Landscape ecology can be unified about six central themes: (1) patches differ in

quality (2) patch boundaries affect flows, (3) patch context matters, (4) connectivity

is critical, (5) organisms are important, and (6) the importance of scale. Although

riverine systems differ from terrestrial systems by virtue of the strong physical force

of hydrology and the inherent connectivity provided by water flow, all of these

themes apply equally to aquatic and terrestrial ecosystems, and to the linkages

between the two.

3.Landscape ecology therefore has important insights to offer to the study of

riverine ecosystems, but these systems may also provide excellent opportunities for

developing and testing landscape ecological theory. The principles and approaches

of landscape ecology should be extended to include freshwater systems; it is time

to take the `land' out of landscape ecology.

Приречные ландшафты.

Riverine landscape diversity

J. V. WARD, K. TOCKNER, D. B. ARSCOTT & C. CLARET

1. This review is presented as a broad synthesis of riverine landscape diversity,

beginning with an account of the variety of landscape elements contained within

river corridors. Landscape dynamics within river corridors are then examined in the

context of landscape evolution, ecological succession and turnover rates of

landscape elements. This is followed by an overview of the role of connectivity and

ends with a riverine landscape perspective of biodiversity.

2. River corridors in the natural state are characterised by a diverse array of

landscape elements, including surface waters (a gradient of lotic and lentic

waterbodies), the fluvial stygoscape (alluvial aquifers), riparian systems (alluvial

forests, marshes, meadows) and geomorphic features (bars and islands, ridges and

swales, levees and terraces, fans and deltas, fringing floodplains, wood debris

deposits and channel networks).

3. Fluvial action (erosion, transport, deposition) is the predominant agent of

landscape evolution and also constitutes the natural disturbance regime primarily

responsible for sustaining a high level of landscape diversity in river corridors.

Although individual landscape features may exhibit high turnover, largely as a

function of the interactions between fluvial dynamics and successional phenomena,

their relative abundance in the river corridor tends to remain constant over

ecological time.

4. Hydrological connectivity, the exchange of matter, energy and biota via the

aqueous medium, plays a major though poorly understood role in sustaining riverine

landscape diversity. Rigorous investigations of connectivity in diverse river systems

should provide considerable insight into landscape-level functional processes.

5. The species pool in riverine landscapes is derived from terrestrial and aquatic

communities inhabiting diverse lotic, lentic, riparian and groundwater habitats

arrayed across spatio-temporal gradients. Natural disturbance regimes are

responsible for both expanding the resource gradient in riverine landscapes as well

as for constraining competitive exclusion.

6. Riverine landscapes provide an ideal setting for investigating how complex

interactions between disturbance and productivity structure species diversity

patterns.

Приречные ландшафты.

Volume 47 Issue 4 Page 601 - April 2002

Large wood and fluvial processes

A. M. GURNELL, H. PIEGAY, F. J. SWANSON & S. V. GREGORY

1. Large wood forms an important component of woodland river ecosystems. The

relationship between large wood and the physical characteristics of river systems

varies greatly with changes in the tree species of the marginal woodland, the climatic

and hydrological regime, the fluvial geomorphological setting and the river and

woodland management context.

2. Research on large wood and fluvial processes over the last 25years has focussed

on three main themes: the effects of wood on flow hydraulics; on the transfer of

mineral and organic sediment; and on the geomorphology of river channels.

3. Analogies between wood and mineral sediment transfer processes (supply,

mobility and river characteristics that affect retention) are found useful as a

framework for synthesising current knowledge on large wood in rivers.

4. An important property of wood is its size when scaled to the size of the river

channel. Small channels are defined as those whose width is less than the majority

of wood pieces (e.g. width

widths greater than the size of most wood pieces (e.g. width

piece length), and `Large' channels are wider than the length of all of the wood

pieces delivered to them.

5. A conceptual framework defined here for evaluating the storage and dynamics of

wood in rivers ranks the relative importance of hydrological characteristics (flow

regime, sediment transport regime), wood characteristics (piece size, buoyancy,

morphological complexity) and geomorphological characteristics (channel width,

geomorphological style) in `Small', `Medium' and `Large' rivers.

6. Wood pieces are large in comparison with river size in `small' rivers, therefore

they tend to remain close to where they are delivered to the river and provide

important structures in the stream, controlling rather than responding to the

hydrological and sediment transfer characteristics of the river.

7. For `Medium' rivers, the combination of wood length and form becomes critical

to the stability of wood within the channel. Wood accumulations form as a result of

smaller or more mobile wood pieces accumulating behind key pieces. Wood

transport is governed mainly by the flow regime and the buoyancy of the wood.

Even quite large wood pieces may require partial burial to give them stability, so

enhancing the importance of the sediment transport regime.

8. Wood dynamics in `Large' rivers vary with the geometry of the channel (slope

and channel pattern), which controls the delivery, mobility and breakage of wood,

and also the characteristics of the riparian zone, from where the greatest volume of

wood is introduced. Wood retention depends on the channel pattern and the

distribution of flow velocity. A large amount is stored at the channel margins. The

greater the contact between the active channel and the forested floodplain and

islands, the greater the quantity of wood that is stored.

Приречные ландшафты.

The fauna of dynamic riverine landscapes

C. T. ROBINSON, K. TOCKNER & J. V. WARD

1.Riverine landscapes are heterogeneous in space (complex mosaic of habitat

types) and time (expansion and contraction cycles, landscape legacies). They are

inhabited by a diverse and abundant fauna of aquatic, terrestrial and amphibious

species.

2.Faunal distribution patterns are determined by interactive processes that reflect the

landscape mosaic and complex environmental gradients. The life cycles of many

riverine species rely upon a shifting landscape mosaic and other species have

become adapted to exploit the characteristically high turn-over of habitats.

3.The complex landscape structure provides a diversity of habitats that sustains

various successional stages of faunal assemblages. A dynamic riverine landscape

sustains biodiversity by providing a variety of refugia and through ecological

feedbacks from the organisms themselves (ecosystem engineering).

4.The migration of many species, aquatic and terrestrial, is tightly coupled with the

temporal and spatial dynamics of the shifting landscape mosaic. Alternation of

landscape use by terrestrial and aquatic fauna corresponds to the rise and fall of the

flood. Complex ecological processes inherent to intact riverine landscapes are

reflected in their biodiversity, with important implications for the restoration and

management of river corridors.

Приречные ландшафты.

Aquatic invertebrates in riverine landscapes

BJORN MALMQVIST

1.Riverine systems consist of a mosaic of patches and habitats linked by diverse

processes and supporting highly complex communities. Invertebrates show a high

taxonomic and functional diversity in riverine systems and are in several ways

important components of these systems. Their distribution patterns, movements

and effects on ecological flows, testify to their importance in various landscape

ecological processes. This paper reviews the invertebrate literature with respect to

patterns and processes in the riverine landscape.

2.The distribution of invertebrates in riverine habitats is governed by a number of

factors that typically act at different scales. Hence, the local community structure

can be seen as the result of a continuous sorting process through environmental

filters ranging from regional or catchment-wide processes, involving speciation,

geological history and climate, to the small-scale characteristics of individual

patches, such as local predation risk, substratum porosity and current velocity.

3.Dispersal is an important process driving invertebrate distribution, linking different

ecological systems across boundaries. Dispersal occurs within the aquatic habitat

as well as into the terrestrial surrounding, and also over land to other waterbodies.

New genetic techniques have contributed significantly to the understanding of

aquatic invertebrate dispersal and revealed the importance of factors such as

physical barriers, synchrony of emergence and taxonomic affiliation.

4.Invertebrates affect the cycling of nutrients and carbon by being a crucial

intermediate link between primary producers, detritus pools or primary consumers,

and predators higher up in the trophic hierarchy. Suspension feeders increase the

retention of carbon. The subsidies of aquatic invertebrates to the terrestrial

ecosystem have been shown to be important, as are reciprocal processes such as

the supply of terrestrial invertebrates that fall into the water.

5.Future studies are needed both to advance theoretical aspects of landscape

ecology pertaining to the invertebrates in riverine systems and to intensify the

experimental testing of hypotheses, for example with respect to the scaling of

processes and to linkages between the terrestrial and aquatic systems. Another

promising avenue is to take advantage of naturally steep environmental gradients,

and of systems disturbed by humans, such as regulated rivers. By comparison with

unimpaired reference sites, the mechanisms involved might be identified. The use of

`natural' experiments, especially where environmental gradients are steep, is another

technique with great potential.

Приречные ландшафты.

Terrestrial invertebrates inhabiting lowland river floodplains of Central Amazonia

and Central Europe: a review

JOACHIM ADIS & WOLFGANG J. JUNK

1.Amazonian terrestrial invertebrates produce high population densities during

favourable periods and may suffer a drastic decrease during occasional floods and

droughts. However, the monomodal, predictable flood pulse of the larger

Amazonian rivers favours the development of morphological (respiratory organs,

wing-dimorphism), phenological (synchronization of life cycles, univoltine mode of

life), physiological (flooding ability, gonad dormancy, alternating number of

developmental stages), and behavioural adaptations (migration, temporal diving)

with numerous interactions.

2.In lowlands of Central Europe, the flood pulse of large rivers is less predictable

than in Central Amazonia and is superimposed by the seasonal light/temperature

pulse (summer/winter regime). Some terrestrial invertebrates show physiological

resistance against inundation or drought, phenologies fitting the normal annual

rhythm of water level fluctuation (quiescence or diapause of eggs or adult

invertebrates), high dispersal ability and migration. However, most species survive

simply using a `risk strategy', combining high reproduction rates, dispersal and

reimmigration following catastrophic events.

3.The diversity of species in terrestrial invertebrates is lower in lowland riverine

ecosystems of Central Amazonia and Central Europe compared with the respective

uplands because of flood stress in these systems. However, floodplains in Central

Amazonia possess a greater number of endemic species in comparison with Central

European floodplains because of long periods of fairly stable climatic conditions in

comparison with large palaeoclimatic changes in Central Europe.

Водотоки: влияние лесной сукцессии на сообщество бентоса.

Freshwater Biology

Volume 39 Issue 1 Page 151 - February 1998

Long-term recovery of a mountain stream from clear-cut logging:

the effects of forest succession on benthic invertebrate community structure

Michael K. Stone* AND J. Bruce Wallace

1. Changes in benthic invertebrate community structure following 16years of forest

succession after logging were examined by estimating benthic invertebrate

abundance, biomass and secondary production in streams draining a forested

reference and a recovering clear-cut catchment. Benthic invertebrate abundance was

three times higher, and invertebrate biomass and production were two times higher

in the disturbed stream.

2. Comparison of invertebrate community abundance 1, 5 and 16years after clear-

cutting indicated that the proportion of scrapers had decreased, whereas shredders

had increased. Functional group percentage similarity indicated that the invertebrate

community in the disturbed stream 16years after clear-cutting was more similar to

the reference than to that found earlier in the disturbed stream.

3. The five indices calculated from data collected over the past 16years, as well as

the abundance, biomass and production data collected during this study, proved to

be of differing value in assessing recovery of the disturbed stream from logging.

Percent dominant taxon and EPT (Ephemeroptera, Plecoptera and Trichoptera)

taxon richness failed to show any initial differences between reference and disturbed

streams, indicating that these indices may not be useful for measuring recovery

from logging. The percentage Baetis and shredder-scraper indices showed

significant differences only during the 1977 study and suggest recovery (no

difference between reference and disturbed) by 1982. The North Carolina Biotic

Index showed continued differences during 1982 in the riffle and depositional

habitats and recovery by 1993. Total macroinvertebrate abundance, biomass and

production, as well as EPT abundance, indicated continued differences between the

reference and disturbed streams in the 1993 study.

Влияние деревьев на речной бентос.

Lester P J. Mitchell S F. Scott D.

Institution

Dep. Biol., Queen's Univ., Kingston, ON K7L 3N6, Canada.

Title

Substrate and shade: Mechanisms of willow tree influence on the

macroinvertebrate community of Heeney Creek, South Island, New Zealand.

Source

Archiv Fuer Hydrobiologie 136(2). 1996. 145-158.

Experiments were conducted in an effort to isolate the relative

contributions of substrate size distribution and shading to the reduction

in macroinvertebrate abundance associated with riparian willows in Heeney

Creek, New Zealand. The effect was apparently not related to the

availability of food. Periphyton primary production was not significantly

different among open, artificially shaded, and willow shaded sites, in

spite of the intense shading, and previous studies have indicated that

allochthonous food sources are more important to invertebrates at the

willow-shaded sites than at the open sites. An experiment in which the

substrate size distributions associated with willow-shaded and open sites

were reconstituted in containers, and incubated in the stream for

colonisation, indicated that there were significant effects of substrate

type. These were, however, relatively minor. The major effect was from

another, undetermined factor associated with willows, as the containers at

artificially shaded sites had higher abundances than at willow shaded

sites, regardless of substrate type. Willows are known to produce a

variety of compounds that inhibit the feeding of terrestrial animals, and

we postulate that exudates from their roots may similarly affect the

invertebrates in small, closely overgrown streams such as Heeney Creek.

Влияние прибрежных деревьев.

Authors: Lester-PJ Mitchell-SF Scott-D

Субстратное и теневое влияние деревьев ивы

на макробентос ручья Хени, Новая Зеландия.

Substrate and Shade - Mechanisms of Willow Tree Influence on the Macroinvertebrate Community of Heeney Creek, South-Island, New-Zealand

ARCHIV FUR HYDROBIOLOGIE 1996, Vol 136, Iss 2, pp 145-158

Abstract:

Experiments were conducted in an effort to isolate the

relative contributions of substrate size distribution and

shading to the reduction in macroinvertebrate abundance

associated with riparian willows in Heeney Creek, New Zealand.

The effect was apparently not related to the availability of

food. Periphyton primary production was not significantly

different among open, artificially shaded, and willow shaded

sites, in spite of the intense shading, and previous studies

have indicated that allochthonous food sources are more

important to invertebrates at the willow-shaded sites than at

the open sites. An experiment in which the substrate size

distributions associated with willow-shaded and open sites were

reconstituted in containers, and incubated in the stream for

colonisation, indicated that there were significant effects of

substrate type. These were, however, relatively minor. The major

effect was from another, undetermined factor associated with

willows, as the containers at artificially shaded sites had

higher abundances than at willow shaded sites, regardless of

substrate type. Willows are known to produce a variety of

compounds that inhibit the feeding of terrestrial animals, and

we postulate that exudates from their roots may similarly affect

the invertebrates in small, closely overgrown streams such as

Heeney Creek.

Приречные ландшафты.

Freshwater Biology

Volume 47 Issue 4 Page 867 - April 2002

Re-establishing and assessing ecological integrity in riverine landscapes

M. JUNGWIRTH, S. MUHAR & S. SCHMUTZ

1. River-floodplain systems are among the most diverse and complex ecosystems.

The lack of detailed information about functional relationships and processes at the

landscape and catchment scale currently hampers assessment of their ecological

status.

2. Intensive use and alteration of riverine landscapes by humans have led to severe

degradation of river-floodplain systems, especially in highly industrialised countries.

Recent water-related regulations and legislation focussing on high standards of

ecological integrity back efforts to restore or rehabilitate these systems.

3. Most restoration projects in the past have suffered from a range of deficits,

which pertain to project design, the planning process, the integration of associated

disciplines, scaling issues and monitoring.

4. The so-called `Leitbild' (i.e. a target vision) assumes a key role in river restoration

and the assessment of ecological integrity in general. The development of such a

Leitbild requires a multistep approach. Including explicitly the first step that defines

the natural, type-specific reference condition (i.e. a visionary as opposed to an

operational Leitbild), has great practical advantages for restoration efforts, primarily

because it provides an objective benchmark, as is required by the European Water

Framework Directive and other legal documents.

5. Clearly defined assessment criteria are crucial for evaluating ecological integrity,

especially in the pre- and postrestoration monitoring phases. Criteria that reflect

processes and functions should play a primary role in future assessments, so as to

preserve and restore functional integrity as a fundamental component of ecological

integrity.

6. Case studies on the Kissimmee River (U.S.A.), the Rhine River (Netherlands and

Germany), and the Drau River (Austria) are used to illustrate the fundamental

principles underlying successful restoration projects of river-floodplain systems.

жүктеу/скачать 1.21 Mb.

Достарыңызбен бөлісу: