The Central Arizona Project (CAP) canal system restricts movements of mammals across Avra Valley, Arizona. The Wildlife Mitigation Corridor (WMC) was established to provide access for animals over the Tucson Aqueduct of the CAP, and allow movement across Avra Valley. To determine if animals used the WMC more or less than other canal crossings (i.e., bridges), we recorded tracks of desert mule deer (Odocoileus hemionus crooki), collared peccary (Pecari tajacu), and coyote (Canis latrans) in and out of the WMC from August 1996 through July 1997. We also monitored two water catchments adjacent to crossings within the WMC with cameras to determine if catchments were used by wildlife. Deer and collared peccaries used crossings in the WMC more than those outside of the WMC. There was no significant difference between use of crossings by coyotes. Coyotes used all crossings throughout the year regardless of the availability of water sources.

There is increasing interest in the use of prescribed fire to reduce fuel loadings and other management objectives in ecosystems of the Madrean Province. Fuel loadings were measured on the same pine-oak ecosystem occurring on five different sites with a range of different fire frequencies. To determine the effects of fire frequencies on fuel loading. Study sites located in Mexico were characterized by a high fire frequency. Study sites in the United States were characterized by low and intermediate fire frequencies. Heavy fuel loadings on sites with high fire frequencies were below the recommended amounts for coarse woody debris. Sites with intermediate fire frequencies were within recommended amounts of coarse woody debris while sites with low fire frequencies were above recommended amounts for coarse woody debris. There was no difference in fine fuel loading among sites with 2, 5, 9, and 13 fires since 1900. Total fuel loading was inversely related to fire frequency. The effects of intermediate fire frequencies can be used to assess ecosystem function and meet multiple use management objectives.

To determine the factors affecting the distribution and abundance of submersed aquatic vegetation (SAV) within Topock Marsh, I measured 4 factors: (1) light availability (water depth and turbidity); (2) substrate type (grain size and organic content); (3) sediment nutrient availability; and (4) exposure to wave action. Multiple regression indicated that turbidity negatively affected the distribution and abundance of SAV in Topock Marsh during 1996 and 1997. Principal components analysis of sediment data in combination with a manipulative experiment indicated substrate type and sediment nutrients may influence SAV. Young shoots of Najas marina L. grew taller and had more branches when grown in sediments that had a smaller grain size and relatively higher amounts of NH4-N and soluble K. If the main objective of the refuge is to provide waterfowl foraging habitat, careful manipulation of water levels may be necessary to adequately promote the growth of SAV in Topock Marsh.

I used sapling population data collected since 1980 to investigate how canopy disturbance interacts with chronic understory disturbance to determine regeneration patterns. I reconstructed flooding history using a combination of river gauging, a local water-level recorder, and contour maps. 1979 was an extreme flood year for this site, as was 1989. Reduction in flooding frequency since dam construction in 1965 was significant for all elevations, while reduction in flooding duration was significant only for the upper half of the site. Using constrained ordination, I showed that sapling occurrence varies primarily along a flooding/soil moisture gradient, and secondarily along a canopy-openness gradient. This confirms that both flooding and light influence local variation in species composition. Small sapling density increased by more than five times during the decade, while large sapling density increased over 70%. I suggest that this increase is related to the decline in frequency and duration of flooding, and specifically, to the pattern of flooding from 1979-1989, characterized by severe flooding in 1979 and 1989. Sapling survivorship also responded to temporal variation in flooding over the decade. A damage survey revealed a size component to flooding damage, with small individuals making up a disproportionate share of those in the highest damage classes. In addition, there is a relationship between river flow and the elevation of saplings that died, suggesting that the effects of elevation are not simply related to flooding, but perhaps to soil moisture as well. Analyses of sapling growth suggest that there is a trade-off between tolerating flooding in wet years and being subject to moisture stress in dry years. I presented evidence that canopy gaps play an important role in determining sapling growth. Gaps appear to be crucial to the continued success of large saplings, and the fastest-growing individuals are found in them. This may also confer a measure of flood-tolerance related to sapling size.

This study shows that fire had a strong short-term effect on the small-sized individuals in the understory of two dry upland vegetation types, sandhill and upland pine. Large trees were less affected than saplings and small trees. The changes in these types were mainly structural rather than compositional. The influence of fire diminished toward the wet end of the vegetation gradient. Post-fire recruitment via resprouting and germination from seeds was rapid. The interaction of fire and vegetation type was apparent in the comparison of the two dry upland types with slope types. Simulation of fuel and fire provided additional, although not very strong, support for the existence of differences in fire behavior corresponding to an environmental gradient from dry upland forests to mesic and wet slope forests. Ordination using pre- and post-fire data suggests that fire had limited effects on current vegetation patterns and there was no indication that any present pre-fire type would be converted to another type. Furthermore, there were no clear convergent or divergent patterns in overall vegetation change; hence it was difficult to predict long-term changes. An eight-year record of vegetation change at a tornado damaged savanna site in Hickory Creek Unit demonstrates that the tornado had resulted in the succession of the vegetation toward a midslope forest, but two prescribed fires partially reversed such a trend. Phytolith analysis revealed that upland pine and some upperslope forests had abundant grass phytoliths. This indicates that these types had a grass component in the past under an open canopy which might have disappeared as a result of fire suppression, logging, and encroachment of shrubs and hardwoods.

A bottomland hardwood forest stand located in east Texas experienced a hurricane-related flood event in 1989. After this event, Carpinus caroliniana Walt. had a large pulse in mortality, decreasing dramatically in abundance (47%) over a 5-year period. The decline was greater at low elevations suggesting that at least part of the mortality was related to flooding. The flood was the longest summer flood on record. The duration of this growing season flood may have been partly a consequence of upstream dam management. Linear regression showed that in areas where Carpinus death was greater, several sapling species had increases in basal area growth. The invasive species Sapium sebiferum (L.) Roxb. had the greatest increase. This suggests that the Carpinus death and concomitant increase in light availability resulted in accelerated invasion of this forest by Sapium.

A mixed pine-oak forest in the Hickory Creek unit of the Big Thicket National Preserve was hit by a tornado in December of 1983. Subsequently the forest was subjected to three prescribed fires in an effort to restore this area to its former savanna state. The tornado has allowed for both pines and oaks to regenerate. Both groups have regained much of the basal area lost in the tornado. However, the biggest compositional change has occurred at the understory level. There has been a huge increase in the upland shrub Ilex vomitoria (yaupon). Vegetation composition and density seem to be involved in a positive feed-back loop with fire. Plots dense with shrubs experienced low flame heights, which has allowed for increased shrub growth. This process seems to be leading the tornado plots down a spiral towards unflammability. The current fire regime of periodic winter fires has only been able to slow this process in the most open plots. A more intense use of fire, such as repeated summer burns appears to be necessary to reclaim this area as a fire-dependent savanna.

Despite a 20 year reintroduction effort into northeastern North Carolina, little is known about the natural history and ecology of red wolves (Canis rufus). In 2005, I studied home ranges, habitat use and pup attendance of red wolves during the pup rearing season. Data indicated that red wolves have home range sizes intermediate between those of coyotes (Canis latrans) and gray wolves (Canis lupus). Similar to other canids in the eastern United States, red wolves preferred to use extensive agricultural fields during the summer months rather than adjacent wooded areas. Red wolves abandoned dens early to move pups into adjacent agricultural fields. Consistent with pup rearing studies done on gray wolves, red wolf pups were rarely left alone indicating that red wolves share duties of pup rearing and that males play a significant role in the rearing of red wolf pups.

The reproductive success of American kestrels (Falco sparverius) infected with Trichinella pseudospiralis was significantly reduced when compared with uninfected controls. Egg laying was delayed, and infected females produced fewer eggs than uninfected controls. Infected females were more aggressive and copulated less frequently. Egg breakage among infected birds was greater than among controls. Infected females tended to lay eggs outside the nest box. Infected females did not incubate as frequently as the controls, thus accounting for the higher prevalence of embryo mortality among these birds. The above effects translated into a mean production of 2.1 hatchlings per control pair and 0.6 per infected pair of kestrel. Both in breeding and non-breeding kestrel, T. pseudospiralis infections gave rise to a general decline in mobility. Behavioural effects are primarily attributable to the presence of muscle larvae. The parasite showed no predilection for specific muscle groups.

No description available.