Vegetation responses to 35 and 55 years of native ungulate grazing in shrubsteppe communities

Ungulate populations are managed in shrubsteppe ecosystems around the world, but relatively few long-term datasets are available that test the impacts of these grazers on shrubsteppe structure and function. This study evaluated 8 exclosures in 4 shrubsteppe communities to determine the effects of deer and elk over 35 or 55 years on (1) plant biomass and species composition, (2) soil nitrogen (N) mineralization and net nitrification rates, Olsen extractable phosphorus (P), and C:N ratios, and (3) arthropod diversity and abundance. The site with deer, the highest ungulate densities, and coldest climate (Sinlahekin Wildlife Area, WA) had greater vegetative biomass and cover inside the exclosures than outside. The sites with elk, moderate ungulate densities, and intermediate climatic conditions (Oak Creek and Wenas Wildlife Areas, WA) had no effects of exclosures on vegetative biomass or cover. The site with elk, the lowest ungulate densities, and driest climatic conditions (L.T. Murray Wildlife Area, WA) had greater shrub cover outside of the exclosures. Ungulates significantly increased net N mineralization and nitrification rates, providing a potential explanation for compensatory growth by grazed plants. Our data suggest that arthropod herbivory does not substitute for ungulate herbivory. To the contrary, arthropod diversity reflected ungulate-induced changes in plant biomass. In addition to effects on standing biomass, ungulates were associated with increased exotic plant species richness at all 4 sites. Our results suggest that there may be a balance between indirect positive and direct negative effects of herbivory on plants that varies with ungulate densities and site characteristics, and that arthropod herbivory does not functionally replace ungulate herbivory.     

Size selection of food by cutthroat trout, Salmo clarki, in an Idaho stream

The mean size of food and amount of food consumed by cutthroat trout from Palisades Creek in southeastern Idaho increased with trout length. Number of organisms of terrestrial origin, number of aquatic larvae, number of ants, and number of berries from redstem dogwood were related to trout length. The size range and number of taxa consumed increased with trout size, indicating that as trout get larger, they broaden their feeding menu. The minimum size of food consumed was relatively constant for all trout, but larger trout appeared to feed more from the stream bottom. Trout may have a minimum length of food, below which items cannot be detected as food. Other possible factors affecting the feeding of cutthroat trout are mentioned.         

Burrow plugging by prairie dogs in response to Siberian polecats

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Observations on woundfin spawning and growth in an outdoor experimental stream

The response of woundfin to different substrates and current speeds was investigated in an outdoor experimental stream. Fish spawned in groups of 15 – 20 over 5 – 10 cm rock substrate in a .06 to .09 m/sec current at a depth of 10 cm. Eggs were adhesive on the undersides of the rocks. Fish spawned under these conditions grew to approximately 55 – 60 mm TL in 5 months.     

Nodulation and acetylene reduction by two legumes with Rhizobia indigenous to northern Great Basin soils

Medicago sativa L. and Hedysarum boreale Nutt. were grown in the greenhouse on soils representing 27 of the major soil associations of the northern Great Basin. Nodulation of Medicago sativa L. by indigenous rhizobia occurred with 25 of the soil associations and of Hedysarum boreale Nutt. with 21 of these soil associations. Nitrogen fixation, as indicated by acetylene reduction activity, was greater for Medicago sativa L. than for Hedysarum boreale Nutt. for most of the soil associations. Multiple regression functions incorporating 49 independent climatic, edaphic, and vegetation variables failed to predict acetylene reduction activity with satisfactory precision.     

Factors affecting selection of winter food and roosting resources by porcupines in Utah

Ecological and phytochemical factors potentially affecting winter dietary discrimination by porcupines ( Erethizon dorsatum ) in the mountain brush zone of Utah were studied. Porcupines utilized gambel oak ( Quercus gambelii ) as their primary winter food and roosting resource. Big-tooth maple ( Acer grandidentatum ) was the most common tree species in the study area but was rarely utilized by porcupines. Conifer species were used as a food and roosting resource significantly less often than they occurred in the study area, despite thermal advantages provided by their relatively dense canopies. Oak feed trees were successfully separated from conifer feed trees by discriminant analysis 100% of the time. Oak trees were correctly classified as feed and nonfeed trees 71% of the time. Gambel oak contained higher amounts of crude protein, fiber, and tannins, but was lower in either extract fractions and fatty acid content than conifers. A layer of adipose tissue used as an energy reserve by porcupines may have relaxed energy intake demands sufficiently to permit them to concentrate on a diet of oak tissue, which is high in protein, rather than a high-fat conifer diet. A diet relatively high in protein may have facilitated digestion of food material high in fiber. Temperature did not affect selection of tree species for roosting. Rock and snow caves were utilized infrequently and the study population ranged widely. Three of 15 study animals were eaten by predators.     

Molecular evidence on evolutionary switching from particle-feeding to sophisticated carnivory in the calanoid copepod family Heterorhabdidae: drastic and rapid changes in functions of homologues

The oceanic calanoid copepod family Heterorhabdidae is unique in that it comprises both particle-feeding and carnivorous genera with some intermediate taxa. Both morphological and molecular (nuclear 18S and 28S rRNA) phylogenetic analyses of the family suggest that an evolutionary switch in feeding strategy, from transitions of typical particle-feeding through some intermediate modes to sophisticated carnivory, might have occurred with the development of a specially designed ‘poison’ injection system. In view of the small amount of genetic differentiation among genera in this family, the switching of feeding modes and re-colonization from deep to shallow waters might have occurred over a short geological period since the Middle to Late Miocene.     

Tree growth and regeneration response to climate and stream fow in a species-rich southwestern riparian forest

We studied the influence of climate variables, stream flow, and topography on regeneration and growth of several riparian tree species ( Acer negundo, Alnus oblongifolia, Fraxinus velutina, Juglans major, Platanus wrightii, Populus fremontii, Salix spp.) at an unregulated perennial stream, West Clear Creek, in central Arizona. A pulse of seedling regeneration occurred for Alnus, Fraxinus, Platanus, Populus , and Salix in 1995 and 1996 following high winter and spring surface flows in 1993 and high spring surface flow in 1995. In contrast, little regeneration occurred for Acer and Juglans under these conditions. Most seedlings occurred at the active channel topographic location, and few seedlings occurred at abandoned channel, gravel-boulder bar, and bench locations. Relationships between environmental variables and annual radial stem growth varied among species and between constrained and unconstrained reaches. High spring or winter surface flows were negatively related to growth of Acer, Alnus, and Platanus , whereas high spring surface flow was positively related to growth of Fraxinus . Positive relationships between precipitation and growth occurred only for Fraxinus and Juglans , suggesting greater use of surface soil water by these species. Annual radial growth was high for Platanus and Alnus, medium for Acer and Fraxinus, and low for Juglans . Overall, the tree species in our study responded individually, rather than collectively, in regeneration and growth to changes in stream flow and climatic variables.     

Variation in germination response to temperature and water availability in blackbrush ( Coleogyne ramosissima ) and its ecological significance

Blackbursh ( Coleogyne ramosissima Torr.) is a dominant desert shrub in a distinct mid-elevations vegetation belt between creosote bush-bursage ( Larrea tridentata-Ambrosia dumosa ) shrubland below and big sagebrush-pinyon pine- Utah juniper ( Artemisia tridentata-Pinus monophylla-Juniperus osteosperma ) woodland above in the Mojave Desert. Seed germination patterns of blackbrush seeds collected from 2 elevations (1200 and 1550 m) in 5 mountain ranges within the blackbrush shrublands were investigated. Morphological features of blackbrush seeds, including weight, length, and width, were not significantly different ( P > 0.05) among elevations and mountain ranges in the Mojave Desert. Germination of blackbrush seeds was optimal when preceded by a prechill period of 4-6 wk. Seeds incubated at room temperature germinated poorly. Seeds collected at warm, low-elevation sites appeared to be less dormant (required less prechill time), germinated faster, and showed a higher overall germination response; watering at 2-wk intervals revealed the greatest germination. Some ecotypic variation among populations establishing at different elevations was evident with regard to dormancy duration and germination response at certain constant temperatures.     

Vegetation response to fire and postburn seeding treatments in juniper woodlands of the Grand Staircase-Escalante National Monument, Utah

We compared 3 naturally ignited burns with unburned sites in the Grand Staircase-Escalante National Monument. Each burn site was restored with native and nonnative seed mixes, restored with native seeds only, or regenerated naturally. In general, burned sites had significantly lower native species richness (1.8 vs. 2.9 species), native species cover (11% vs. 22.5%), and soil crust cover (4.1% vs. 15%) than unburned sites. Most burned plots, seeded or not, had significantly higher average nonnative species richness and cover and lower average native species richness and cover than unburned sites. Regression tree analyses suggest site variation was equally important to rehabilitation results as seeding treatments. Low native species richness and cover, high soil C, and low cover of biological soil crusts may facilitate increased nonnative species richness and cover. Our study also found that unburned sites in the region had equally high cover of nonnative species compared with the rest of the Monument. Cheatgrass ( Bromus tectorum ) dominated both burned and unburned sites. Despite the invasion of cheatgrass, unburned sites still maintain higher native species richness; however, the high cover of cheatgrass may increase fire frequency, further reduce native species richness and cover, and ultimately change vegetation composition in juniper woodlands.     

Use of space by the marsupials Gracilinanus microtarsus (Gardner and Creighton, 1989) and Marmosops incanus (Lund, 1840) in an Atlantic Forest of southeastern Brazil

The use of space by animals is determined by environmental conditions, biological and ecological adaptations and interactions and mostly by resource availability. We sampled two species of Neotropical mammals to investigate their use of different strata in Atlantic Forest habitat in Brazil, as well as the home range sizes and movements of both sexes of each species. We found no difference in home ranges and movements between the sexes and species, but we found differences in the use of strata, with Gracilinanus microtarsus mostly using the canopy and Marmosops incanus using the ground. Gracilinanus microtarsus males mostly use the understorey in the wet season and the canopy in the dry season. We believe that these patterns of strata use reflect intrinsic characteristics of the species; and the shifts in resources and interspecific competition, which are lower in the dry season, seem to be responsible for the shifts in space use observed for G. microtarsus males. We recommend studies with spool-and-line techniques or radio tracking to further test refined hypotheses regarding the use of space, including the role of territoriality in females.     

A contribution to the knowledge of fly fauna in the Kingdom of Saudi Arabia: new country records and an account of flies identified from Rawdhats,Riyadh Region,with biogeographical remarks (Insecta: Diptera)

A total of 80 fly species (Insecta: Diptera) belonging to 66 genera, and representing 26 families was identified from three natural areas or ‘Rawdhats’ in the Riyadh Region of the Kingdom of Saudi Arabia (KSA). The Rawdhats surveyed are Al-Harmaliyah (Al Quwayiyah Province), Al-Sabalah (Azulfi Province) and Farshet Sheaal (Al Aflaj Province). One family, one subfamily, 11 genera and 18 species were recorded for the first time from KSA, namely: the family Trixoscelididae; the subfamily Suilliinae (Heleomyzidae); the genera Oligodranes (Bombyliidae), Pseudomphrale (Scenopinidae), Actorthia (Therevidae), Crossopalpus (Hybotidae), Scatella (Ephydridae), Suillia (Heleomyzidae), Trixoscelis (Trixoscelididae), Renocera [Sciomyzidae], Melanophora and Stevenia [Rhinophoridae], Miltogramma [Sarcophagidae]; and the species Eremisca heleni (Efflatoun) and Ommatius tenellus van der Wulp [Asilidae], Oligodranes sp. [Bombyliidae], Pseudomphrale flavoscutellata Kröber [Scenopinidae], Actorthia lacteipennis (Becker), Actorthia sp. and Efflatouniella sinatica Mohammad and Badrawy [Therevidae], Crossopalpus hirsutipes Collin [Hybotidae], Eumerus mucidus Bezzi [Syrphidae], Ephydra riparia Fallén and Scatella sp. [Ephydridae], Suillia apicalis (Loew) [Heleomyzidae], Trixoscelis sp. (Trixoscelididae) and Renocera pallida (Fallén) [Sciomyzidae], Goniurellia longicauda Freidberg [Tephritidae], Melanophora sp. and Stevenia sp. [Rhinophoridae], and Miltogramma sp. [Sarcophagidae]. The zoogeographic affinities of the identified species showed a closer affiliation with the Palaearctic Region (26%) than to the Afrotropical Region (12.5%), while about 16% of the species were of both Afrotropical and Palaearctic affinities. Elements from other regions were apparently absent. The result support the idea that the central Arabian Desert which includes our study area is a transitional zone between the Palaearctic and Afrotropical regions.