W30r

FIGURE 12.11 A principal components analysis of 25 stream energy budgets from six biomes shows that arid streams, small mountain streams, and lowland streams separate along axes determined by energy inputs, benthic organic matter (BOM), and transport rates of organic matter. See text for further explanation. (Reproduced from Webster and Meyer 1997.) involved, organic matter budgets often are estimated for just 1 year, or pieced together with data from multiple years. In a comparison of 23...

Disturbance

Complex Diagram Magnetocaloric Effect

Hurricanes, fires, floods, and droughts are well-known examples of extreme disturbances that episodically cause high mortality to populations of many species in forest, grassland, coral reef, river, and other ecosystems. Because species vary in their resistance to disturbance, as well as rates of recolonization and recovery, disturbance can ameliorate strong biological interactions and help to maintain populations of species that might otherwise be eliminated by their consumers or competitors....

Nitrogen sources and quantities

Nitrogen is abundant in the environment as N2, but it is N bonded to oxygen, hydrogen, or C such as nitrate, ammonium, and organic N that comprises reactive N, and until recently this originated mainly by biological N fixation (Wet-zel 2001). As a consequence of the synthesis of nitrogenous fertilizers, burning of fossil fuels, and wide cultivation of crops such as soybeans that have N-fixing microbial symbionts, annual N fixation from anthropogenic sources now exceeds natural fixation...

Rivers are the Product of their Landscapes

Product Life Cycle Nike

In a prescient essay published in 1975, Noel Hynes wrote that ''in every respect the valley rules the stream.'' Geology determines the availability of ions and the supply of sediments, topography determines slope and degree of containment, climate and soils determine vegetation and hence the availability of organic matter and extent of shade, and so on. Decades of research support this view. The river continuum concept describes how basal resources and thus consumer assemblages and stream...

Info

River Bank Straightening

FIGURE 13.4 Decline in spawning populations of Chinook salmon (Oncorhynchus tshawytscha) since the construction of four dams on the lower Snake River, western United States (Reproduced from Kareiva et al. 2000.) tamed river due to six mainstem reservoirs on the middle river and channelization and levee construction along the lower river, the Missouri historically experienced March and June flood pulses that inundated the extensive bottomland forests, occasional prairies, oxbow lakes, and...

The Bicarbonate Buffer System

Buffer Capacity

Dissolved CO2 reacts with H2O to form carbonic acid H2CO3 , a weak inorganic acid that occurs at low concentrations relative to unhydrated CO2 at pH lt 8 Wetzel 2001 . H2CO3 further FIGURE 4.4 A classification of surface waters of the world based on ratios of sodium to calcium and chloride to bicarbonate, in relation to total dissolved salts. As one proceeds from left to right along the lower arm, inputs shift from a dominance of rock dissolution to a dominance of precipitation. The majority of...

Fluvial Processes along the River Continuum

Sediment Supply Stream Power Balance

We are now familiar with many of the principal features of streams, including the shape of their channels, the lateral connection to the flood-plain, the presence of riffles, pools, and meanders, and the sediments of the streambed and its banks. These features vary along the river's course from headwaters to lowlands, and with regional differences in climate and terrain. As stated earlier, streams seek a state of dynamic equilibrium between the imposed conditions of valley slope, discharge, and...

Consumers of CPOM

Shredders Ecology

Figure 8.3 depicts the shredder-CPOM linkage typical of a small stream in the temperate zone. The series of events culminating in the disappearance of leaf CPOM has already been discussed Section 7.1 , and the critical role that microorganisms play both directly and indirectly in influencing the nutritional quality of this resource is elaborated below. CPOM that becomes available in wetlands and larger rivers following macrophyte dieback enters the decomposer trophic web in a very similar...

Experimental studies of competition

Competitive interactions can be manipulated in the laboratory or in the field, conditional on the ingenuity of the investigator to construct an experiment that allows realistic interactions and reveals the mechanisms involved. Laboratory experiments usually offer the greatest experimental control and can be particularly useful in demonstrating the potential for competition and in identifying mechanisms. Field experiments at least in principle offer greater realism, although they too have...

Consumers of FPOM

Detrital Breakdown Streams

The collector-FPOM linkage Figure 8.5 depends on FPOM captured from suspension or from substrates. As discussed in Chapter 7, FPOM is a poorly characterized food source, and it originates in a number of ways. Categories considered to be richest in quality include sloughed periphyton and biofilm, and particles produced in the breakdown of CPOM. Morphological and behavioral specializations for suspension feeding including setae, mouthbrushes, and fans are diverse and well studied Wallace and...

Grazer effects on periphyton

Herbivores affect the periphyton by direct consumption, by physical disruption of the algal mats, and through indirect pathways, especially by nutrient regeneration. Grazing studies commonly report a reduction in periphyton biomass, compositional changes including a reduction in the overstory component, and marked differences in effects depending on the identity of the grazer Steinman 1996 . In addition to these structural changes, grazing can induce functional changes including more vigorous...

The habitat template and species traits

Habitat template theory places particular emphasis on the matching of habitat requirements of individual species to the abiotic and biotic conditions of a locale Southwood 1988, Town-send and Hildrew 1994 . Increasingly, such efforts examine the traits of species with the expectation that attributes such as size, body shape, life span, and mode of dispersal will help us understand why certain species succeed where others do not, and also may provide clues regarding the environmental factors...

Preface to the Second Edition

The diversity of running water environments is enormous. When one considers torrential mountain brooks, large rivers of lowlands, and great rivers whose basins occupy subcontinents, it is apparent how location-specific environmental factors contribute to the sense of uniqueness and diversity of running waters. At the same time, however, our improved understanding of ecological, biogeochemical, hydrological, and geomorphological processes provides insight into the structural and functional...