摘要:

A symposium was held at the 10thannual meeting of the North American Lake Management Society to discuss methods of aquatic vegetation quantification and its application to an aquatic plant management program. Topics discussed at this symposium included the importance of accurate taxonomic identifications, the use of transect and biomass sampling methods, development of manipulative experiments to evaluate management techniques, and advances in remote sensing for aquatic plant quantification. These technical approaches were then illustrated in an ongoing governmental aquatic plant management program. Techniques used for aquatic plant quantification and the importance of vegetation quantification to an ongoing management program are summarized.

ISSN:1040-2381    

DOI:10.1080/07438149309354265

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Biomass quantification techniques are widely used in research on aquatic vegetation, but less often applied to monitor aquatic vegetation or assess specific control techniques. The application of these techniques to both assessing nuisance problems, and evaluating control tactics is discussed using case histories. The proper methods for developing a sampling regime, locating sample points, collecting samples, and analyzing data are reviewed. Critical factors such as quadrat size and sample frequency and number are discussed in depth. The purpose of biomass sampling programs within the context of management plans is to tailor the level of effort to the scale of the management effort, and to appropriately assess or predict effects of the management tactics utilized.

ISSN:1040-2381    

DOI:10.1080/07438149309354266

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Line transects often provide a practical basis for quantitative, nondestructive sampling of aquatic vegetation; here four types of line transect arrangements are briefly compared: 1) transects perpendicular to the shoreline have been widely used, but may oversample nearshore areas where shorelines are convex; 2) transects parallel to each other at regular intervals may provide the best basis for mapping an area; but 3) parallel transects at (stratified) random intervals may reasonably represent different areas within the site and avoid possible biases of regular sampling. The tendency of all three methods to oversample some depth ranges and to combine data from different community types may be obviated by using 4) transects along depth contours near a given shoreline of nearly uniform exposure. Line transects may in some cases be sampled with a line intercept method, which is probably best suited for floating-leaved species, but most often a belt transect consisting of contiguous quadrats is more practical. For each sampling unit, data may be gathered on species presence or percent cover, although the former may yield more information per unit effort. Five field examples are given to illustrate sampling schemes, macrophyte community heterogeneity, and straightforward data summary procedures.

ISSN:1040-2381    

DOI:10.1080/07438149309354267

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Field experiments may be useful for researchers and managers concerned with aquatic plants. Since experimental design and statistical analysis are closely related, this paper discusses statistical and practical considerations for conducting and evaluating field experiments with aquatic plants. Special emphasis is given to the analysis of variance, assumptions required for its use, and concepts related to it (e.g., statistical power, means comparison procedures, treatment structure, pseudoreplication, etc.). The paper concludes with a brief introduction to papers in the literature which illustrate the use of field experiments for studying aquatic plants.

ISSN:1040-2381    

DOI:10.1080/07438149309354268

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Correct identification of vascular aquatic plants is extremely important when studying waters for various management policies. The plants should be thoroughly examined by a person familiar with aquatic flora who is able to interpret technical botanical keys, because many taxa are similar in appearance. Misidentification often leads to possible eradication of an important or rare species from a body of water.

ISSN:1040-2381    

DOI:10.1080/07438149309354269

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Management of Eurasian watermilfoil (Myriophyllum spicatumL.), which was introduced to British Columbia, Canada, about 1970, incorporates various technologies and approaches. Monitoring of Eurasian watermilfoil since 1972 has required development of phytochemical means to distinguishMyriophyllumtaxa, extensive and often repeated surveys of over 1500 lakes, and establishment of a large herbarium and database. Field survey methods have been used extensively to evaluate control procedures, measure rates of plant population change, document and map the spread of Eurasian watermilfoil and its impacts, and provide data to plan annual management. Survey methods used are described and examples of the results are presented to illustrate the application of field survey data to guide decision making and allocation of resources.

ISSN:1040-2381    

DOI:10.1080/07438149309354270

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Phosphorus loading from agricultural activities such as manure and fertilizer applications often contributes to eutrophication of surface waters. The primary goal of the LaPlatte River Watershed Project in northwestern Vermont was to reduce phosphorus loading from farmland through implementation of best management practices (BMPs). Eleven years of monitoring did not show a dramatic decrease in phosphorus concentration or load from the watershed. However, analysis controlling for hydrologic variability suggested significant decreases in phosphorus load from some subwatersheds following completion of the land treatment program. Post-BMP phosphorus load reductions of 26–44% (0.01–0.14 kg/ha/yr) were estimated using a paired regression technique that accounts for discharge differences between years. Phosphorus export was reduced under most circumstances, except under the highest runoff conditions, suggesting that the capacity of the land treatment system to control phosphorus may have been exceeded occasionally. Observed phosphorus reductions in treated watersheds appeared to be related to the degree of treatment after a minimum threshold level of land treatment had been achieved.

ISSN:1040-2381    

DOI:10.1080/07438149309354271

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor

摘要:

Paleolimnological methods can be used to identify baseline limnological conditions and to assess anthropogenic changes in lakes that lack historical limnological data. We studied a suite of Florida lakes and developed regression models that predict limnetic total P and Chiafrom diatom assemblages and nutrient accumulation rates in surface sediments. These models were applied to a210Pb-dated sediment core from Lake Parker, Polk County, Florida, and a pollen-dated profile from Lake Francis, Highlands County, Florida, to infer historical water quality. Our results show that Lake Parker displayed statistically significant increases in limnetic total P and Chiaconcentrations since the 1920s. Lake Francis has been eutrophic for more than 2 millennia, but shows a statistically significant decrease in limnetic total P during the present century. This study demonstrates that lakes may be naturally productive because of edaphic influences and may respond differently to human disturbance. We conclude that paleolimnological estimates of predisturbance nutrient/Chiaconcentrations can help define target conditions for water quality restoration programs.

ISSN:1040-2381    

DOI:10.1080/07438149309354272

出版商:Taylor & Francis Group    

年代:1993

数据来源: Taylor