摘要:

The density and biomass of epiphytic macroinvertebrates onEichhornia crassipes, Nuphar luteum, Panicum hemitomon, Paspalidium geminatum, Ceratophyllum demersum, Utriculariaspp. andHydrilla vertlcillatawere determined In Orange and Henderson lakes, Florida, during December 1982 and February, April, June and August 1983. Density and biomass of epiphytic macroinvertebrates ranged from 6 to 9714 individuals kg−1wet weight of plant and 2 to 3118 mg dry weight kg−1wet weight of plant, respectively, among macrophyte species. The quantities of epiphytic macroinvertebrates were greater on floating and submergent plants than on emergent plants. Abundant invertebrate taxa included Hirudinea, Gastropoda, Amphipoda, Odonata, Trichoptera, and Diptera. There were significant (P <0.05) temporal variations in the abundance of invertebrates; however, consistent temporal trends were not evident.

ISSN:0270-5060    

DOI:10.1080/02705060.1987.9664649

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Habitat factors were correlated with species richness for three guilds of lotic macroinvertebrates within the drainage basin of the Middle Fork of the Salmon River, Idaho. Species richness of filter feeders and scrapers increased with stream size whereas no significant longitudinal pattern was evident for gatherers. Annual variation in stream flow was inversely correlated with species richness for both filter feeders and scrapers, and food abundance was positively associated with scraper species richness. These relationships were consistent with the habitat templet concept of Southwood (1977). In contrast, our descriptive data gave no support for alternative, nonequilibrium models of community organization.

ISSN:0270-5060    

DOI:10.1080/02705060.1987.9664650

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Processing of maple leaf, grass and fern packs (MLP, GP and FP) was investigated in a riffle area of Canagagigue Creek, Ontario where the stream flows through a small woodlot surrounded by agricultural fields. Processing was faster in spring at higher water temperatures than in autumn and % weight loss in general was in the order MLP > FP > GP. Loss of C in MLP was greater (P < 0.01) than in GP and FP in spring and autumn, whereas % N and % P content was greater (P < 0.01) in MLP than FP and GP (% N of FP in autumn was an exception) and was in the order MLP > FP > GP. Colonization of GP by invertebrates was greater (P < 0.05) than that of MLP in spring (GP > FP > MLP), but no difference was seen in autumn (MLP > GP > FP).Baetispreferred to colonize MLP (P < 0.05) than GP and FP, whereas snails,Physa, preferred GP and FP (P < 0.05) to MLP. These plant litters were not only processed at different rates, but exhibited marked differences in nutrient dynamics.

ISSN:0270-5060    

DOI:10.1080/02705060.1987.9664651

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Larval fish assemblages drifting in the open channels and those in adjacent macrophyte beds differed in standing stock and species composition. Standing stocks were approximately 160 times higher in the macrophyte beds than in the open channels during the day but, due to an increase in the number of drifting larvae, only 13 times higher in the macrophyte beds than in the open channels at night. Larvae concentrated in the interior of the macrophyte beds rather than at the ecotone between the macrophyte beds and the open channels.Notropisspp. andLepomisspp. predominated in the drift whileNotropisspp.,Elassoma zonatum, Erimyzon succetta, andLepomisspp. predominated in the macrophyte beds. Drift among all taxa involved only small postlarvae. The drift ofLepomisspp. larvae appeared to be associated with dispersal from the nest at the time of yolk sac depletion.

ISSN:0270-5060    

DOI:10.1080/02705060.1987.9664652

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

We compared three methods for determining the chlorophyllacontent of several aquatic macrophytes. Extraction with DMSO (dimethyl sulfoxide; 100%) yielded chlorophyllavalues which were equivalent to or slightly greater than the values for samples extracted with 90% acetone or 90% methanol. Chlorophyllaextraction with DMSO was somewhat more efficient than methanol or acetone depending on the species examined. Chlorophyllain DMSO extracts appeared to be more stable over time. The DMSO procedure is relatively quick and does not require maceration or centrifugation of the sample, and appears to be suitable for a variety of submersed aquatic macrophytes.

ISSN:0270-5060    

DOI:10.1080/02705060.1987.9664653

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

This study provides: (a) first-known estimates of potential N2O release from aerobic riverine deposits; (b) evidence that simultaneous measures of gas formation and N-transformations can be used to gain insights into mechanisms controlling N2O formation in natural environments; and (c) suggestions for improvements in experimental approaches.

ISSN:0270-5060    

DOI:10.1080/02705060.1987.9664654

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Using a coulometric titration technique, carbon content was determined in biotic and abiotic samples collected in Pool 19 of the upper Mississippi River. With the exception of waterfowl tissue, biotic samples contained substantially less organic carbon than the 50% assumed a priori. Inorganic carbon in soft tissues of biota was not quantitatively significant. Organic carbon content in substratum samples varied among habitats from which the samples were collected.

ISSN:0270-5060    

DOI:10.1080/02705060.1987.9664655

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

A population of brown bullheads (Ictalurus nebulosusLeuseur) in Muskellunge Lake, New York was investigated to determine population density, age structure, sex ratio, fecundity, survivorship, growth, and the intrinsic rate of population increase. The population density estimate was 887 (664 ≤ N ≤ 1424) per ha. The instantaneous rate of survivorship for females (0.26) was significantly lower than the rate for males (0.33). Fecundity averaged 2169 (1841 ≤ N ≤ 2497) per female. Differences in fecundities among individuals were not correlated with differences in weight or length. The number of eggs produced per gram of weight decreased with fish size. We hypothesize that lower female survivorship is related to higher reproductive effort, and examine a natural selection mechanism to explain variations in fecundity. Population characteristics were summarized in a life table, although this analysis may have been influenced by fluctuations in year class strength.

ISSN:0270-5060    

DOI:10.1080/02705060.1987.9664656

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

Studies were conducted to identify the common phytophagous insects that feed onTyphaspp. (cattails) in Minnesota and to quantify the extent of insect herbivory in natural stands. Six lepidopterans and two aphids were noted to feed onTyphashoots. The most common herbivorous insect in natural stands was the miner-borerArchanara oblongaGrt. (Lepidoptera: Noctuidae). The noctuidBellura obliquaWalk, was the most common miner-borer in newly planted cultivated stands. NineteenTyphastands were sampled in midsummer to quantify the extent of insect herbivory. Overall, about 15 percent of shoots showed some evidence of insect herbivory. Eight percent of damaged shoots had damage to upper leaves attributable to lepidopteran miner-borers (chieflyA. oblonga). Five percent of shoots had stem damage. Less than one percent of shoots were damaged by leaf-chewing insects.Typha latifoliastands were more heavily infested than those ofT. angustifoliaorT. glauca. Stands located in southern Minnesota were much more heavily infested than those in northeastern Minnesota. Water depth and shoot nitrogen content did not have a significant effect on infestation rate. The majority of infested shoots suffered minor damage (i.e., <20% reduction in leaf area). Much of the damage caused by lepidopteran miner-borers was indirect. Although naturalTyphastands and small cultivated plots are occasionally susceptible to heavy infestations of phytophagous insects, it seems unlikely that insect pests would hamperTyphabio-energy production in Minnesota.

ISSN:0270-5060    

DOI:10.1080/02705060.1987.9664657

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor

摘要:

In a five-week greenhouse investigation, variations in growth and morphology of monoecious and dioeciousHydrilla[Hydrilla verticillata(L. f.) Royle] were compared over a range of temperatures, 12 to 32 C, on an inorganic sediment and on an organic sediment. For these bio-types, total biomass production was severely restricted at 16 C and below, with thermal optima for growth occurring between 28 and 32 C. Total biomass, shoot number, and shoot length for each biotype were greater on the inorganic sediment than on the organic sediment. At higher temperatures, dioeciousHydrillalengthened more extensively than monoeciousHydrilla; however, the latter produced higher shoot densities and tuber numbers under most experimental conditions. MonoeciousHydrillaappears to be better adapted to moderate temperatures than dioeciousHydrilla, and its potential distribution may include sediments less favorable for growth of the dioecious biotype.

ISSN:0270-5060    

DOI:10.1080/02705060.1987.9664658

出版商:Taylor & Francis Group    

年代:1987

数据来源: Taylor