Showing papers on "Riparian zone published in 1975"

Bottom Fauna-Substrate Relationships in a Northern Colorado Trout Stream: 1945 and 1974

Abstract: A study of bottom fauna-substrate relationships conducted on North St. Vrain Creek, Colorado, USA in 1945 was repeated in 1974 to determine changes in the stream en- vironment and in the community structure and standing crop of macroinvertebrates. The stream remains a clear, unpolluted trout stream with soft water of neutral pH. Despite differences in flow, temperature, and riparian vegetation, macroinvertebrate composition was similar to that of 1945; most differences can be attributed to normal year-to-year fluctuations and slight shifts in emergence periods. Total density was less on all substrata in 1974, which is attributed to the higher discharge. Total biomass was comparable except for lower values on bedrock in 1974.

Herbivore Pressure on Two Types of Tropical Forests

Abstract: The herbivore pressure on the understory of two types of Costa Rican forest was measured and compared during the dry season. Leaves were collected from plants, classified as old and new and categorized according to the amount of herbivore damage present. There was no significant difference between the number of new leaves being produced in the understory of each forest. There was a significant difference in the number of individual plants producing new leaves in each forest-a large number of riparian plants produced a small number of new leaves, and a small number of the dry forest plants produced a large number of new leaves. Old leaves from the riparian forest had sustained significantly less damage than old dry forest leaves. Old leaves from both forests showed significantly more damage than young leaves. These results are discussed in terms of two strategies. Because of year-long predation by insects, it was reasoned that the riparian forest species should spend more energy producing insect-resistant leaves; dry forest species should spend less energy producing insect-resistant foliage because they lose their leaves annually. THE GUANACASTE LOWLANDS of Costa Rica are characterized by high average temperature, low rainfall and an extended dry season from November to April. The vegetation is described as tropical dry forest (Holdridge 1964). During the dry season almost all canopy and understory trees drop their leaves, but riparian forests remain much greener. The riparian plants are not forced into deciduousness by the drought, and the leaves are probably longer-lived than those of the dry forest. Riparian forests also have a higher insect density than do the dry forests during the dry season, because the streambeds provide a refuge for insects escaping from the drought (Janzen and Schoener 1968; Janzen 1973a,b). As a consequence herbivore pressure could be very intense in the riparian forest during the dry season. I reasoned that since dry forest plants have leaves with a shorter half-life, they might be less likely than riparian forest plants to evolve leaves rich with substances rendering them more highly resistant to herbivores. If this strategy is operating, then leaves from riparian forests should show significantly less damage per unit time than leaves from dry forests. Two hypotheses were advanced. First, old leaves from the dry forest should show significantly more damage than leaves from the riparian forest. Second, young leaves from both forests should show comparable degrees of damage, since there is some evidence that it takes time for toxic compounds to build up in the leaves (Feeny 1970). This paper reports on the testing of these two hypotheses.

Drainage basin characteristics from ERTS data

Abstract: The author has identified the following significant results. ERTS-derived measurements of forests, riparian vegetation, open water, and combined agricultural and urban land use were added to an available matrix of map-derived basin characteristics. The matrix of basin characteristics was correlated with 40 stream flow characteristics by multiple regression techniques. Fifteen out of the 40 equations were improved. If the technique can be transferred to other physiographic regions in the nation, the opportunity exists for a potential annual savings in operations of about $250,000.

The baltic sea - a semi-enclosed sea, as seen by the hydrologist

Abstract: The paper discusses water renewal of the Baltic Sea, a semi-enclosed basin, the general configuration of the water balance, the size and distribution of its individual elements and the interrelations between them. Connections between long-term variations in the water balance and certain ecological features are stressed. To make possible a deepened understanding of the water renewal, international cooperation has been organized between the seven riparian countries.

Southern Arizona riparian habitat: Spatial distribution and analysis

Abstract: The objectives of this study were centered around the demonstration of remote sensing as an inventory tool and researching the multiple uses of riparian vegetation. Specific study objectives were to: (1) map riparian vegetation along the Gila River, San Simon Creek, San Pedro River, Pantano Wash, (2) determine the feasibility of automated mapping using LANDSAT-1 computer compatible tapes, (3) locate and summarize existing mpas delineating riparian vegetation, (4) summarize data relevant to Southern Arizona's riparian products and uses, (5) document recent riparian vegetation changes along a selected portion of the San Pedro River, (6) summarize historical changes in composition and distribution of riparian vegetation, and (7) summarize sources of available photography pertinent to Southern Arizona.

Environmental Aspects—Sacramento Bank Protection

Abstract: Studies show that bank protection can include environmental measures and can preserve environmental values from erosion. Reclamation of the Sacramento Valley, California, included Federal construction of a leveed flood-control project. Erosion has threatened the integrity of the levee system and a program of revetment construction at critical sites was authorized in 1960. Early construction was on a least-cost basis and seriously reduced riparian vegetation which supplies important wildlife habitat in the semi-arid valley. Alternative revetment designs and construction procedures have been developed to minimize adverse environmental effects.

The Impacts of Lowland River Management

Abstract: Waterways, of whatever description, represent one of the most threatened habitat types in the British Isles today. Conservationists have good cause for deep anxiety concerning the future welfare of birds and many other forms of wildlife which have become highly adapted to a riparian life-style.

Vegetation and pollen rain in the cuatro cienegas basin, coahuila, mexico

Abstract: The Cuatro Cienegas Basin is a desert valley in central Coahuila, Mexico. The basin floor bears many aquatic habitats and supports a complex mosaic of edaphically-controlled vegetation communities. Spatial distribution and species composition of the communities are controlled by available soil moisture and soil salinity. Riparian sites support dense stands of sedges and cattails. Drier locations peripheral to riparian habitats support an extensive grassland community. Playas, stabilized dunes and other extremely dry areas bear a xerophytic community char- acterized by certain halophytic chenopods. Control by local vegetation over compo- sition of pollen rain in the basin floor is extreme, and local pollen rain is dominated by grass, Chenopodiaceae-Amaranthus and aquatic pollen types. Fluctuations of proportions of those pollen types characterize pollen rains on the edaphic communities. This paper presents a vegetational and palynological description of the floor of the Cuatro Cienegas Basin, a small desert valley in north- eastern Mexico. This survey was designed to provide modern control information on which to base interpretations of several late-Quater- nary fossil pollen chronologies that have been developed for the area. The fossil sequences are from sediment cores collected from springs located on the valley floor. Those records, together with descriptions of vegetation and pollen rain on mountains and bajadas surrounding the basin floor, are available elsewhere (Meyer 1973). Gilmore (1947) and Miiller (1947) presented preliminary botanical descriptions of the Cuatro Cienegas area, and Minckley (1969) pro- vided a geological description of the basin that includes a summary of the current status of biological research from the area. The valley is located at ca. 270 N, 1020 W, in the Chihuahuan Desert in central Coahuila, Mexico, roughly 240 km SSE from the Big Bend of the Rio Grande. The floor, or barrial (West 1964), of the basin averages 740 m above mean sea level and is surrounded by mountains rising to 1 Present address: National Commission on Water Quality, 1111 18th St., N.W.,