摘要:

Aquatic macroinvertebrates were collected from two sections of Sink Branch, a central Florida stream disturbed by surface mining, channelization and grazing. Benthic organisms were sampled over a twelve month period with “stovepipe” substrate cores, drift nets, dip nets and multiple plate artificial substrate samplers. Species richness, organism density and Shannon-Weiner species diversity values were calculated for each sample. Sample variability was estimated by calculating coefficients of variation. With the exception of the dip nets which were considerably more diverse, none of the methods revealed significant differences in the diversity of samples. The four sampling devices did not census the number of species (species richness) equally well; the order of effectiveness was dip nets > drift nets > multiplates > substrate cores. There were no significant differences in variability of the species richness data among sampling techniques or among samples collected by the same technique. Organism density measured with substrate core and multiplate samplers was identical between sample types. Organism densities in the drift net, multiplate and core samples did not vary over time. A comparison of the coefficients of variation for the density data indicated that there were no significant differences in variability between sample techniques. Our results suggest that artificial substrate samplers may not reduce sampling variability in sandy Coastal Plain streams. In addition, the decision to use any of a variety of sampling techniques should be based on the nature of the assessment since sampling devices differ in the types of data they produce.

ISSN:0270-5060    

DOI:10.1080/02705060.1985.9665112

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

Allochthonous processes of three low-order southeast Alaska streams, exhibiting a range of riparian vegetation and successional stages occurring before and after logging, were compared. Leaf-litter traps were used to estimate annual litter input. Leaf processing rates were measured by confining known amounts of leaf material in litter bags. Instream woody debris and stored and transported organics were also estimated. Annual litter inputs ranged from 52 g AFDW-m−2on a clearcut watershed to 295 g AFDW.m−2on a logged and deciduously revegetated watershed. All deciduous species tested (red alder—Alnus rubra, black cottonwood—Populus trichocarpa, salmonberry—Rubrus spectabilis) had fast post-leaching processing rates (k > 0.01), while western hemlock (Tsuqa heterophylla) was processed slowly (k < 0.005). The logged watersheds contained the largest amount of woody debris. Stored particulate organic matter (POM) was generally 2 or more times greater in depositional than erosional areas. Seasonal changes in stored POM were most obvious in erosional areas. Transported POM was highest in a logged watershed revegetated with deciduous riparian species.

ISSN:0270-5060    

DOI:10.1080/02705060.1985.9665113

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

An investigation in the upper Colorado River near Parachute, Colorado revealed temporal variations in the amount of important fish habitats. Quantitative measures of habitat area were related to flow. The relationships developed between flow and surface area of specific habitats revealed the existence of critical thresholds. The implications of these results could be important in the management of the Colorado River system for wildlife and human consumptive and non-consumptive uses.

ISSN:0270-5060    

DOI:10.1080/02705060.1985.9665114

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The development of attached algal communities in a lowland stream in central Sweden was investigated with reference to differing levels of grazing pressure. An enclosure-exclosure method was used to measure periphytic biomass accrual and community structure in the presence of low, natural, and high densities of the gastropodTheodoxus fluviatilis. A highly significant difference (p < .01) in chlorophylla, carbon, and nitrogen was observed between chambers with low grazer density and those with natural and high grazer densities. Chambers with natural and high densities ofT. fluviatilishad lower percent composition of filamentous green algae (mainlyCladophora) and lower C/N ratios in the periphyton.

ISSN:0270-5060    

DOI:10.1080/02705060.1985.9665115

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

摘要:

The annual growth of submersed macrophytes in Eau Galle Reservoir, Wisconsin, was measured during 1981.Ceratophyllum demersumL. andPota-mogeton pectinatusL. collectively comprised approximately 94% of maximum macrophyte standing crop. Much of the macrophyte standing crop, accrued during the summer, senesced during the early fall. However,C. demersum, persisted into the winter. Major senescence in this species occurred prior to spring thaw. Epiphyte biomass comprised a large portion (up to 33%) of macrophyte biomass, and in combination with phytoplankton, may have limited the growth of submersed macrophytes by light attenuation. Areal densities (g m−2) of N, P, and K in macrophyte tissue changed primarily as a function of change in standing crop rather than due to changes in respective tissue nutrient concentrations. Release of tissue nutrients associated with macrophyte decay potentially occurred as two separate annual events of senescence. The significance of the submersed macrophyte community of Eau Galle reservoir in nutrient cycling appears to be relatively minor, because of the persistence ofC. demersuminto the winter, but more importantly due to the periodically riverine nature of this system. Nutritional conditions in most reservoirs are probably much less influenced by internal loading associated with macrophyte decay than in natural lakes.

ISSN:0270-5060    

DOI:10.1080/02705060.1985.9665116

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

ISSN:0270-5060    

DOI:10.1080/02705060.1985.9665117

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

ISSN:0270-5060    

DOI:10.1080/02705060.1985.9665118

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor

ISSN:0270-5060    

DOI:10.1080/02705060.1985.9665101

出版商:Taylor & Francis Group    

年代:1985

数据来源: Taylor