ALBERT — All Library Books, journals and Electronic Records Telegrafenberg

1

Electronic Resource

The relation between wave exposure and distribution of emergent vegetation in a eutrophic lake (1987)

WEISNER, STEFAN E. B.

Oxford, UK : Blackwell Publishing Ltd

Freshwater biology 18 (1987), S. 0

add to mindlist on the mindlist

Details

ISSN: 1365-2427

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: SUMMARY 1. Maximum water depth penetration and changes in horizontal distribution during 39 years of the emergent vegetation in a eutrophic lake in southern Sweden were investigated.2. The capacity of the emergent vegetation to penetrate into deeper water areas was found to be higher at wave exposed than al sheltered sites.3. Differences in biomass and biomass allocation of the dominant speeies. Phragmites australis, between an exposed and a sheltered site suggest that horizontal expansion towards deeper water at sheltered sites is limited by unfavourable substrate conditions.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1365-2427.1987.tb01338.x

Permalink

	Location	Call Number	Expected	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

2

Electronic Resource

Dynamics of submerged macrophyte populations in response to biomanipulation (2001)

Strand, John A. ; Weisner, Stefan E. B.

Oxford UK : Blackwell Science Ltd

Freshwater biology 46 (2001), S. 0

add to mindlist on the mindlist

Details

ISSN: 1365-2427

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Biology

Notes: 1. A 6-year study (1992–97) of changes in submerged vegetation after biomanipulation was carried out in the eutrophicated Lake Finjasjön, Southern Sweden. Ten sites around the lake were revisited each year. At each site five samples of above-ground biomass were taken at 10 cm water depth intervals. An investigation of the seed bank at the 10 sites, and a grazing experiment where birds and large fish were excluded was also conducted.2. Between 1992 and 1996, in shallow areas (water depth 〈 3 m), vegetation cover increased from 〈 3 to 75% and above-ground biomass from 〈 1 to 100 g DW m–2. Mean outer water depth increased from 0.3 to 2.5 m. Elodea canadensis and Myriophyllum spicatum accounted for 〉 95% of the increase in biomass and plant cover. The following year (1997), however, cover and above-ground biomass decreased, mainly attributable to the total disappearance of E. canadensis. Secchi depth increased after biomanipulation until 1996, but decreased again in 1997.3. Total and mean number of submerged species increased after biomanipulation, probably as a result of the improved light climate. However, after the initial increase in species number there was a decrease during the following years, possibly attributed to competition from the rapidly expanding E. canadensis and M. spicatum. The lack of increase in species number after the disappearance of E. canadensis in 1997 implies that other factors also affected species richness.4. A viable seed bank was not necessary for a rapid recolonization of submerged macrophytes, nor did grazing by waterfowl or fish delay the re-colonization of submerged macrophytes.5. Submerged macrophytes are capable of rapid recolonization if conditions improve, even in large lakes such as Finjasjön (11 km2). Species that spread by fragments will increase rapidly and probably outcompete other species.6. The results indicate that after the initial Secchi depth increase, probably caused by high zooplankton densities, submerged vegetation further improved the light climate. The decrease in macrophyte biomass in 1997 may have caused the observed increase in phosphorus and chlorophyll a, and the decrease in Secchi depth. We suggest that nutrient competition from periphyton, attached to the macrophytes, may be an important factor in limiting phytoplankton production, although other factors (e.g. zooplankton grazing) are also of importance, especially as triggers for the shift to a clear-water state.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1046/j.1365-2427.2001.00746.x

Permalink

	Location	Call Number	Expected	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

3

Electronic Resource

Decoupling of cascading trophic interactions in a freshwater, benthic food chain (1996)

Brönmark, Christer ; Weisner, Stefan E. B.

Springer

Oecologia 108 (1996), S. 534-541

add to mindlist on the mindlist

Details

ISSN: 1432-1939

Keywords: Interaction strength ; Predation ; Ponds ; Snails ; Periphyton

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Food chain theory provides explicit predictions for equilibrium biomasses among trophic levels in food chains of different lengths. Empirical studies on freshwater benthic food chains have typically been performed on chains with up to three levels and in field experiments with limited spatial and temporal scale. Here we use a “natural snapshot experiment” approach to study equilibrium biomass and abundance among trophic levels in natural ponds differing only with respect to fish assemblage structure. Forty-four ponds were surveyed for their densityand biomass of fish, snails and periphyton. Ponds were divided into three categories based on fish assemblage: ponds with no fish (two trophic levels), ponds with molluscivorous fish (three trophic levels) and ponds that also had piscivorous fish (four trophic levels). Ponds without fish had a high density and biomass of snails and a low biomass of periphyton, whereas snails were scarce and periphyton biomass was high in ponds with molluscivorous fish. In the presence of piscivores, molluscivore populations consisted of low numbers of large individuals. Snail assemblages in piscivore ponds were characterised by relativelyhigh densities of small-bodied detritivorous species and periphyton biomass was not significantlydifferent from ponds with three trophic levels. Thus, predictions from classic food chain theory were upheld in ponds with up to three trophic levels. In ponds with four trophic levels, however, there was a decoupling of the trophic cascade at the piscivore-molluscivore level. Gape-limited piscivory, predation on snails by molluscivores that have reached an absolute size refuge from predation, and changes in food preferences of the dominant snails are suggested to explain the observed patterns.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00333731

Permalink

	Location	Call Number	Expected	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

4

Electronic Resource

Effects of an organic sediment on performance of young Phragmites australis clones at different water depth treatments (1996)

Weisner, Stefan E. B.

Springer

Hydrobiologia 330 (1996), S. 189-194

add to mindlist on the mindlist

Details

ISSN: 1573-5117

Keywords: Phragmites australis ; reed decline ; growth ; biomass allocation ; nutrient uptake ; eutrophication

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Performance of young Phragmites australis plants was examined after 7 weeks on an artificial nutrient-enriched inorganic substrate and on the same substrate to which an organic sediment from a eutrophic lake was added, at three different water depth treatments. Growth decreased, and proportional allocation of biomass to roots increased, with the addition of sediment. These differences were significant in shallow and deep water, but not at a medium depth. Concentrations of phosphorus and nitrogen in plant biomass decreased, and concentration of iron increased, with addition of sediment. The effects of sediment addition may have resulted from a decreased availability of nutrients in the substrate or from an impaired root functioning. Nutrient exhaustion in the substrate, due to a fast plant growth, can explain the relatively strong effects in shallow water. Deep water, on the other hand, probably restricted oxygen transport to the roots, resulting in an impaired root functioning in the low-redox sediment environment. The results show that, especially in relatively deep water, growth of undisturbed plants of P. australis may be inhibited by eutrophication of sediments, probably because of an impaired root functioning in sediments containing reduced toxic compounds (e.g. ferrous iron).

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00024207

Permalink

	Location	Call Number	Expected	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

5

Electronic Resource

Wave exposure related growth of epiphyton: implications for the distribution of submerged macrophytes in eutrophic lakes (1996)

Strand, John A. ; Weisner, Stefan E. B.

Springer

Hydrobiologia 325 (1996), S. 113-119

add to mindlist on the mindlist

Details

ISSN: 1573-5117

Keywords: Potamogeton pectinatus ; epiphyton ; submerged macrophytes ; production ; distribution ; eutrophic lakes

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract The distribution of submerged macrophytes in eutrophic lakes has been found to be skewed towards sites with intermediate exposure to waves. Low submerged macrophyte biomass at exposed sites has been explained by, for instance, physical damage from waves. The aim of this study was to investigate if lower biomass at sheltered sites compared to sites with intermediate exposure to waves can be caused by competition from epiphyton. Investigations were performed in eutrophic lakes in southern Sweden. Samples of submerged macrophytes and epiphytic algae on the macrophytes were taken along a wave exposure gradient. The amount of epiphyton (AFDW) per macrophyte biomass decreased with increased exposure. Biomass of submerged macrophytes, on the other hand, increased with increased exposure until a relatively abrupt disappearance of submerged vegetation occurred at high exposures. Production of epiphytic algae was monitored on artificial substrates from June to September at a sheltered and an exposed site in three lakes. It was higher at sheltered sites compared with exposed sites. We suggest that epiphytic algae may be an important factor in limiting the distribution of submerged macrophytes at sheltered sites in eutrophic lakes.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00028271

Permalink

	Location	Call Number	Expected	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

6

Electronic Resource

Indirect effects of fish community structure on submerged vegetation in shallow, eutrophic lakes: an alternative mechanism (1992)

Brönmark, Christer ; Weisner, Stefan E. B.

Springer

Hydrobiologia 243-244 (1992), S. 293-301

add to mindlist on the mindlist

Details

ISSN: 1573-5117

Keywords: Fish ; community structure ; vegetation ; eutrophic lakes

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract The loss of submerged macrophytes during eutrophication of shallow lakes is a commonly observed phenomenon. The proximate reason for this decline is a reduction of available light due to increasing phytoplankton and/or epiphyton biomass. Here we argue that the ultimate cause for the transition from a macrophyte-dominated state to a phytoplankton-dominated state is a change in fish community structure. A catastrophic disturbance event (e.g. winterkill) acting selectively on piscivores, cascades down food chains, eventually reducing macrophyte growth through shading by epiphyton, an effect that is reinforced by increasing phytoplankton biomass. The transition back from the phytoplankton to the macrophyte state depends on an increase in piscivore standing stock and a reduction of planktivores. A conceptual model of these mechanisms is presented and supported by literature data and preliminary observations from a field experiment.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00007045

Permalink

	Location	Call Number	Expected	Availability

Others were also interested in ...

Paper (German National Licenses)

Fulltext

7

Electronic Resource

Rhizome dynamics and resource storage in Phragmites australis (1992)

Granéli, Wilhelm ; Weisner, Stefan E. B. ; Sytsma, Mark D.

Springer

Wetlands ecology and management 1 (1992), S. 239-247

add to mindlist on the mindlist

Details

ISSN: 1572-9834

Keywords: biomass ; carbohydrates ; nitrogen ; phosphorus ; Phragmites australis ; potassium ; reed ; rhizome ; translocation ; wetland

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Seasonal changes in rhizome concentrations of total nonstructural carbohydrates (TNC), water soluble carbohydrates (WSC), and mineral nutrients (N, P and K) were monitored in two Phragmites australis stands in southern Sweden. Rhizome biomass, rhizome length per unit ground area, and specific weight (weight/ length ratio) of the rhizomes were monitored in one of the stands. Rhizome biomass decreased during spring, increased during summer and decreased during winter. However, changes in spring and summer were small (〈 500 g DW m-2) compared to the mean rhizome biomass (approximately 3000 g DW m−2). Winter losses were larger, approximately 1000 g DW m-2, and to a substantial extent involved structural biomass, indicating rhizome mortality. Seasonal changes in rhizome length per unit ground area revealed a rhizome mortality of about 30% during the winter period, and also indicated that an intensive period of formation of new rhizomes occurred in June. Rhizome concentrations of TNC and WSC decreased during the spring, when carbohydrates were translocated to support shoot growth. However, rhizome standing stock of TNC remained large (〉 1000 g m−2). Concentrations and standing stocks of mineral nutrients decreased during spring/ early summer and increased during summer/ fall. Only N, however, showed a pattern consistent with a spring depletion caused by translocation to shoots. This pattern indicates sufficient root uptake of P and K to support spring growth, and supports other evidence that N is generally the limiting mineral nutrient for Phragmites. The biomass data, as well as increased rhizome specific weight and TNC concentrations, clearly suggests that “reloading” of rhizomes with energy reserves starts in June, not towards the end of the growing season as has been suggested previously. This resource allocation strategy of Phragmites has consequences for vegetation management. Our data indicate that carbohydrate reserves are much larger than needed to support spring growth. We propose that large stores are needed to ensure establishment of spring shoots when deep water or stochastic environmental events, such as high rhizome mortality in winter or loss of spring shoots due to late season frost, increase the demand for reserves.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00244929

Permalink