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  • 1
    Electronic Resource
    Electronic Resource
    Boston, MA, USA : Blackwell Science Inc
    Restoration ecology 7 (1999), S. 0 
    ISSN: 1526-100X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Flow regulation, which has largely eliminated flooding along the Rio Grande in central New Mexico, has substantially changed the riparian ecosystem. We investigated managed flooding as a means of restoring ecosystem function. After collecting baseline data during 1991 and 1992 in two riparian forest sites that had not flooded for about 50 years, we flooded an experimental site for 27–32 days during late spring of 1993, 1994, and 1995, leaving the reference site unflooded. During the final year of the study we compared these sites to two additional sites located within the riverside levee, one of which has been flooding naturally while the second remained largely unflooded. Three years of experimental flooding did not change the total biomass of either woody debris or forest-floor litter at the experimental flood site. Both woody debris and forest-floor litter, however, were significantly lower at the natural flood site than at the experimental flood site and two unflooded sites. Leaf and wood decomposition rates increased with flooding. The decay rate for cottonwood logs at the unflooded site (0.010 per year) predicted a half-life of 69.3 years, while the decay rate of 0.065 per year after 3 years of experimental flooding predicted a half-life of 10.6 years. This suggests that a decade of annual flooding may be used to restore the organic debris to pre-regulation levels. Flooding may also have caused an increase in litter production. These results suggest that experimental flooding has initiated a process of restoring ecosystem function within the riparian forest.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Freshwater biology 29 (1993), S. 0 
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 〈list xml:id="l1" style="custom"〉1 We examined the potential selective pressures exerted by different types of predators on morphological prey defences using the case-building larvae of the limnephilid caddisfly, Limnephilus frijole. The predators were a predaceous minnow, Gila pandora, and an aeschnid dragonfly naiad, Oplonaeschna armata.2 The influence of larval case design on vulnerability to predators was evaluated in a series of laboratory experiments. Larval L. frijole were collected from a stream without fish or dragonflies. In the laboratory, larvae still occupying their field-built cases were exposed to the two predators, with which L. frijole co-occurs in other streams. Following 24 h exposure of caddisfly larvae to a specific predator, the pre-trial case length, case strength, case width, and case composition of victims and survivors were compared.3 Principal components analysis (PCA) indicated substantial independent variation for all four case parameters in the study population. The cases of larvae surviving exposure to either dragonfly naiads or fish were significantly stronger and wider than cases of victims of predation. Cases of survivors were also longer and had a greater mineral fraction than those of victims, but differences were either marginally significant or not significant.4 These results demonstrate that specific aspects of case design affect the vulnerability of caddisfly larvae. In addition, predaceous fish and predaceous invertebrates, using different predation techniques, may exert similar selective pressures on these defenses. Case aspects influencing vulnerability in these experiments are broadly consistent with natural variation in case design associated with predator-rich and predator-free habitats for related caddisfly species.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 50 (2005), S. 0 
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. We examined the role of flooding on the leaf nutrient content of riparian trees by comparing the carbon : nitrogen : phosphorus (C : N : P) ratio of leaves and litter of Rio Grande cottonwood (Populus deltoides ssp. wislizenii) in flood and non-flood sites along the Middle Rio Grande, NM, U.S.A. The leaf C : N : P ratio was also examined for two non-native trees, saltcedar (Tamarix chinensis) and Russian olive (Elaeagnus angustifolia), and six species of dominant riparian arthropods.2. Living leaves and leaf litter of cottonwoods at flood sites had a significantly lower leaf N : P ratio and higher %P compared with leaves and litter at non-flood sites. A non-flood site downstream from wastewater effluent had a significantly lower litter C : N ratio than all other sites, suggesting N fertilisation through ground water. The non-native trees, saltcedar and Russian olive, had higher mean leaf N content, N : P ratio, and lower C : N ratio compared with cottonwoods across study sites.3. Riparian arthropods ranged from 5.2 to 7.1 for C : N ratio, 56–216 for C : P ratio, and 8.9–34 for N : P ratio. C content ranged from 25 to 52% of dry mass, N content from 4.7 to 10.8%, and P content from 0.59 to 1.2%. Differences in stoichiometry between high C : nutrient leaf litter and low C : nutrient invertebrates suggests possible food-quality constraints for detritivores.4. These results suggest that spatial and temporal variation in the C : N : P ratio of cottonwood leaves and leaf litter is influenced by surface and subsurface hydrologic connection within the floodplain. Reach-scale variation in the elemental composition of riparian organic matter inputs may have important implications for decomposition, nutrient cycling, and food webs in river floodplain systems.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Laboratory feeding experiments using Hesperoperla pacifica (Banks), Perlidae, and Megarcys signata (Hagen), Perlodidae, as predators and Baetis tricaudatus Dodds and Ephemerella altana Allen as prey indicate a strong effect of prey morphology and mobility and predator hunger on prey selection by stoneflies. Knowledge of both dietary composition and feeding behavior was necessary to fully understand prey selection by these stoneflies. Fasted stoneflies presented with live prey ate more E. altana while satiated stoneflies ate approximately equal numbers of the two mayfly species. This pattern of dietary composition was the result of a reduction of attack frequency on the slower swimming E. altana with predator satiation and a continued high attack rate on B. tricaudatus regardless of recent feeding history. In contrast, fasted H. pacifica fed fresh frozen mayflies ate more B. tricaudatus indicating the importance of differences in prey mobility in controlling dietary composition. The high degree of similarity in patterns of feeding and mechanisms underlying those patterns for H. pacifica and M. signata suggest that they may be using similar “rules” for choosing mayfly prey and we suggest that mayfly prey are ranked by stoneflies on the basis of handling times. A general mechanistic model for stoneflies feeding on mayflies is presented and discussed.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Landscape ecology 13 (1998), S. 203-214 
    ISSN: 1572-9761
    Keywords: lightning research ; precipitation ; vegetation ; monsoon ; GIS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We investigated the question “Is there a relationship between seasonality in precipitation and vegetative cover in Pole Canyon, NM?” GIS and statistical methods were used to determine the degree of association between either summer or winter precipitation and percent canopy cover for trees, graminoids and total vegetation. Monsoon (summer) precipitation was predicted for the years 1986–1994 from lightning strike and relative humidity data by multiple regression. Winter precipitation, the percent of annual precipitation that occurs during winter, and vegetative cover were derived from the Forest Service Terrestrial Ecosystem Survey. Vegetation and precipitation data were ranked and classified (e.g., high, medium, low) and cross-tabulations were generated to compare the spatial distribution of vegetation classes within each precipitation class. Results indicate that seasonality in precipitation affects the distribution and spatial pattern of vegetation at landscape scales. Winter precipitation is a key factor that influences the distribution and spatial pattern of tree cover. Monsoon precipitation may affect the spatial pattern of graminoid cover where Bouteloua gracilis dominates. Winter precipitation may affect the distribution and spatial pattern of graminoid cover where Festuca arizonica dominates. Some of the unexplained relationships may be due to competition between trees and graminoids for moisture and other limiting factors. The importance of temperature was implicit in the division between summer (monsoon) and winter seasons. Annual precipitation, elevation, topography and edaphic factors probably contributed to the observed relationships.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Hydrobiologia 65 (1979), S. 69-74 
    ISSN: 1573-5117
    Keywords: Streams ; Substrate size ; Substrate complexity ; Colonization ; Benthic insects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A field experiment was performed in a New Mexico (U.S.A.) stream to investigate the relation between size and diversity of substrate and numbers and diversity of colonizing insects. Baskets with either small gravel, large gravel, or a 1 : 1 mixture of the two sizes were placed in a riffle area and colonization was monitored for 19 days. Colonization was rapid, and both total number of individuals and number of species colonizing the substrates had stopped increasing by the end of the experiment. Fewer individuals colonized baskets downstream, suggesting that the drift is a major source of insect colonists. Small substrate supported more individuals and more species than the larger stones. Total number of individuals and the number of species on the mixed substrate were between numbers on small and large substrate. These results do not support previous generalizations on the relation between substrate size and complexity and the structure of invertebrate communities in streams. Results of the study are compared with the findings of recent experimental studies and it is suggested that earlier generalizations on the role of substrate size and complexity need to be reexamined.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Environmental biology of fishes 49 (1997), S. 417-434 
    ISSN: 1573-5133
    Keywords: assemblage structure ; floods ; disturbance ; refugia ; stream fish ; stream stability ; American southwest ; introduced species
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Spatial and temporal variation of fish communities in four secondary channels of the San Juan River between Shiprock, NM and Bluff, UT were investigated from July 1993 through November 1994. Fish abundance and habitat availability data were collected to determine if physical attributes of sites influenced spatial and temporal variation in their fish communities. Stability of habitat was shown to positively influence the stability of the fish community. Analysis of variance revealed greater spatial than temporal variation in the abundance of red shiner, Cyprinella lutrensis, fathead minnow, Pimephales promelas, and flannelmouth sucker Catostomus latipinnis, while speckled dace, Rhinichthys osculus showed greater temporal variation. Ordination, using detrended correspondence analysis, revealed variation in fish communities by site, date, and sample year. Spatial variation was greatest during low-flow periods when the greatest differences in habitat among the four sites occurred. Spring runoff had the greatest temporal effect on the fish communities in secondary channels and appeared to ‘reset’ the communities by displacing those species that were less resistant to increased current velocities. This annual event may help maintain native fish species adapted to these conditions in the San Juan River while moderating the abundance of nonnative fish species.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Water, air & soil pollution 9 (1978), S. 385-393 
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Water, air & soil pollution 14 (1980), S. 187-205 
    ISSN: 1573-2932
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Past studies of the Rio en Medio, New Mexico, U.S.A., have shown significant changes in water quality and in invertebrate communities below the Sante Fe Ski Area. The present study was undertaken to determine how far downstream the effects of the ski area extend.. The concentration of every major nutrient except SO4 was found to increase below the ski area and the only mechanism for recovery seemed to be dilution by downstream tributaries. Increased sediment loads below the ski area were also recorded. Peaks of sediment transport were associated with snow melt and summer rains. Much of the increased sediment below the ski area appeared to settle out in the upper reaches of the Rio en Medio. Composition and diversity of stream insects appeared to be little affected. However numbers and biomass of invertebrates were significantly reduced below the ski area. These reductions were attributed to the effects of increased sediment load. Some recovery of invertebrate production was recorded at distances of 700 to 2200 m below the ski area.
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