I examined trends in relative abundance and species richness of breeding and wintering grassland birds before (1996) and after (1997, 1998) a spring prescribed burn in a mesquite-dominated desert grassland at Buenos Aires National Wildlife Refuge, Arizona. The burn was moderate in intensity, patchy in extent, and affected ground cover more strongly than shrub cover, smaller shrubs more strongly than larger shrubs, and killed 1% of velvet mesquite (Prosopis velutina). Species richness of breeding birds decreased in the first year post-burn. Of breeding species, black-throated sparrows (Amphispiza bilineata) and mourning doves (Zenaida macroura) increased; whereas Botteri's sparrows (Aimophila botterii), Cassin's sparrows (Aimophila cassinii), and pyrrhuloxias (Cardinalus sinuatus) decreased in relative abundance. Breeding species characterized as not shrub-dependent exhibited changes that were more pronounced than those for shrub-dependent species. Of wintering birds, ladder-backed woodpeckers (Picoides scalaris) and vesper sparrows (Pooecetes gramineus) increased, and cactus wrens (Campylorhynchus brunneicapillus) decreased in relative abundance.

I determined density and habitat use of desert mule deer (Odocoileus hemionus crooki) on the Buenos Aires National Wildlife Refuge, a semidesert grassland in southeastern Arizona, in 1996. I observed 219 groups of deer; densities varied from 0.9 ± 0.3 (SE) deer/km² in summer to 2.5 ± 1.3 in winter. Herd size varied from 1.5 ± 0.1 deer/group in summer to 9.7 ± 2.0 in winter. Density of females was greater than males (0.9 ± 0.3 and 0.03 ± 0.04, respectively). Mule deer used subshrub-grass more in summer (χ² = 54.8, 6 df, P < 0.0001) and Russian thistle (Sallsola kali) less and cactus more in autumn (χ² = 60.2, 6 df, P < 0.0001) than expected. Deer used mesquite (Prosopis velutina) less than expected, which may have been due to the difficulty of observing deer in dense cover. In general, the mule deer population was widespread, had a high proportion of females, and used vegetation associations as available.

Western spruce budworm (Choristoneura occidentalis) outbreaks periodically disturb Western US conifer forests by defoliating canopies, which could alter the quantity and chemistry of throughfall delivered to the forest floor. Our objectives were to: i) quantify throughfall water, carbon (C), nitrogen (N), and phosphorus (P) fluxes under budworm-impacted canopies, and ii) examine the influence of herbivore intensity on flux magnitudes. In June 2015, we installed throughfall collectors in two watersheds experiencing high and background levels of herbivory. In each watershed, four plots, each with three throughfall collectors, were established (n=24) collectors), and two bulk rainfall collectors were installed in areas without canopy cover. Throughfall and rainfall were collected from late June to early November 2015. Samples were analyzed for dissolved organic carbon (DOC), ammonium (NH4-N), and soluble reactive phosphorus (SRP). Over the sampling period, throughfall fluxes ranged 8.57 to 47.59 kg/ha for DOC, 0.004-0.011 kg/ha for NH4-N, and 007 - 0.29 kg/ha for SRP. Percent throughfall was slightly, but not significantly, higher in the high (48%) compared to the background watershed (42%). There were no differences in solute concentrations among the watersheds. Net throughfall fluxes, the sum of canopy uptake and leaching and dry/fog deposition, differed significantly for NH4-N by herbivory level and through time for NH4-N and DOC but not SRP. Over time, net NH4-N throughfall fluxes showed a clear transition from net uptake of NH4-N to net leaching of NH4-N in the high herbivory watershed. There was also a clearn NH4-N pulse in the high herbivory watershed after the first, but not subsequent, rainfall events. In this N-limited forest, altered throughfall N may affect soil nutrient cycling and downstream water quality.

Trees of Slash pine showed reduced growth, by an order of magnitude, following exposure to two hurricanes (Elena and Kate) in 1985. The reduced growth is caused by salt spray chlorosis and/or defoliation from high winds. Ring width, radial tracheid diameter, radial cell number, tracheid length and microfibril angle were measured for samples from before and after major storms. Data for ring width, earlywood radial cell diameter and cell number were not normally distributed, while data for latewood radial cell diameter, tracheid length and microfibril angle showed normal distributions. There were significant statistical differences for all main effects for ring width, earlywood radial cell diameter, cell number and tracheid length. The data for latewood radial cell diameter show significant differences for effects of time and height, but not for compass direction. There are significant differences in earlywood cellulose microfibril angle for height effects, and no difference for time and direction effects. Data for latewood cellulose microfibril angle show significant differences for the effects of time and height. / Source: Dissertation Abstracts International, Volume: 55-01, Section: B, page: 0016. / Major Professor: Loran C. Anderson. / Thesis (Ph.D.)--The Florida State University, 1993.

I examine three aspects forest vegetation of northern Florida: the Land Office Survey records of the abundance and distribution of woody species across northern Florida in the early nineteenth century; the abundance and distribution of woody species across a sharp elevation gradient in the hardwood slope forests along the Apalachicola River; and the population decline of Torreya taxifolia. / Land Office Survey data was tabulated for all available bearing trees north of Gainesville. This study includes 131,227 trees sampled at 49,896 section corners and mid-point lines. This data tabulation shows that northern Florida was dominated by pines prior to U.S. settlement. Over 77 percent of bearing trees were pines. Pineland oaks are the next most abundant species after pine. Wetlands trees, such as bay, gum, and cypress were dominant species in the absence of pine. The mixed hardwood species are a diverse group, including beech, magnolia, and dogwood, with no clear dominant among them. / The second portion of this research examines the spatial relationships among the species of the hardwood slope forests along the Apalachicola River. Species distributions were sampled using 80 belt transects in four ravine systems. Species turnover across elevation is high, but measures of species diversity and forest structure do not change with elevation. Distribution patterns of the major species indicate that assemblages in the adjacent elevation samples in the middle and upper slope positions are more similar to one another than are assemblages from the lower elevations. The assemblages do not, however, appear to form sub-communities with respect to elevation. / Finally, I examine hypotheses for the decline of Torreya taxifolia, a narrowly endemic conifer native to ravines along the Apalachicola River. Included in this analysis of the torreya decline is a demographic summary of 108 torreya on preserve land. Most individual torreya are multiple stemmed and less than 14 years old. Further, these individuals are most frequently grown at low elevations and under moderate to dense canopy shade. Among the many hypotheses proposed to explain the decline, I present evidence that fire suppression may have allowed fungal populations to soar, contributing to the onset of disease. / Source: Dissertation Abstracts International, Volume: 51-12, Section: B, page: 5692. / Major Professor: Joseph Travis. / Thesis (Ph.D.)--The Florida State University, 1990.

Forest fragmentation causes diverse changes to natural communities. Changes in spider communities' species diversity provide tools to understand the effects of area and isolation in a fragmented landscape. Bottomland Hardwood forest provides an excellent opportunity to study fragmentation because it has undergone profound loss and subdivision The present study was carried out in 11 fragments of three size classes, the small ranging from 2.7 to 91 ha, medium from 1,042 to 5,294 ha, and large from 32,348 to more than 460,000 ha. The forest remnants were located inside and around New Orleans, Louisiana. A rapid assessment methodology was used to measure the biological diversity of spiders in the fragments. A total of 3,538 adult female spiders in 127 morphospecies were collected in 274 sampling units. The expected number of species for Bottomland Harwood forest was calculated between 161 and 210 species using EstimateS software. Evaluation of the effects of Bottomland Forest fragmentation on the spider community demonstrated significant negative consequences of area reduction on spider species diversity. Not only did species richness decrease, but also species composition changed with decreased fragment size. Species composition was influenced by both population extirpations in small fragments and by the presence of spider species adapted to open areas moving inside a small forest remnant. Spider species composition inside small sized fragments differed from the species observed both in medium and large sized fragments Functional (guild) community relationships were also distorted by fragmentation. The dominance of some species of spiders was more pronounced in small and medium sized fragments. For example, large-bodied, orb-weaving spiders tended to decrease from, and small theridiids increased proportionately in the small fragments. Size of prey was also affected significantly for hymenopterans, dipterans, and homopterans, suggesting more complex effects of forest fragmentation. Another observation from the present study was the strong effect of the surrounding matrix on the diversity of species, exemplified by the unusually high diversity of a fragment surrounded by agricultural activities in comparison to others engulfed by urban development This study supported the advantages of using rapid assessment techniques in the evaluation of biological diversity and for the first time this technique was used in fragmented habitats. The use of non-parametric analysis to predict species richness provided consistent results for medium and large sized fragments and more variable results in the small ones as a consequence of the elevated proportion of singletons observed there / acase@tulane.edu

Ovenbirds (Seiurus aurocapillus) and Swainson's Warblers (Limnothlypis swainsonii) wintering in Jamaica exhibited divergent foraging behaviors, with Ovenbirds picking prey from the leaf litter surface and Swainson's Warblers flicking leaves aside to search for prey concealed beneath the leaf litter. The two species consumed significantly different prey: Ovenbirds feeding primarily on ants, and Swainson's Warblers most frequently consuming beetles and spiders, but also consuming roaches and small geckos. The differences in foraging strategies help explain the species' different habitat use patterns. Because of the ubiquity of ants, Ovenbirds are habitat generalists whereas Swainson's Warblers are dependent on habitats that have a well-developed canopy, leaf litter layer, and an abundant leaf litter fauna Ovenbird body condition declined seasonally, concurrent with seasonal declines in prey biomass. Rectrix regrowth rates and overwinter change in body mass were significantly correlated with ant biomass on Ovenbird territories. In habitats and years in which prey biomass decreased to <2.5 mg/0.25 m 2, Ovenbirds were not able to maintain body mass. The results confirm the hypothesis that dry season desiccation significantly decreases arthropod populations and the severity of the dry season strongly affects habitat quality for Ovenbirds Swainson's Warblers appear to be more tolerant of dry season leaf litter desiccation than Ovenbirds, as habitats with a deep leaf litter layer provided refugia for invertebrates. Correspondingly, Swainson's Warbler showed no seasonal decline in dry forests where they were relatively common. These results underscore the need for conservation of dry forests for the geographically restricted Swainson's Warblers Ovenbirds defended spatiotemporal territories, such that home ranges of neighboring birds overlapped, but individuals were not in the same place at the same time. Home range size was not significantly correlated with prey biomass. However, I experimentally decreased ant biomass on portions of the home ranges of four individuals. These birds showed a significant increase in home range size and movement rates. Control birds showed no change in either variable. These results strongly suggest that Ovenbirds constantly monitor food resources and adjust home range size accordingly and that food abundance limits winter habitat carrying capacity / acase@tulane.edu

Understanding how commercial forests can be managed to benefit wildlife has important conservation implications, as silvicultural landscapes occur globally and have high economic value. In this study, I compared two habitat types in southeastern Louisiana, even-aged loblolly pine ( Pinus taeda) and bottomland hardwood forests, both used for breeding by Swainson's Warbler (Limnothlypis swainsonii; SWWA). I investigated habitat quality and habitat selection patterns of SWWA to (1) assess the conservation value of pine plantations for understory-nesting birds, (2) identify ecological factors important in habitat selection at multiple scales, and (3) contribute needed information on the natural history and status of a species of conservation concern The density of breeding pairs, timing of nesting, clutch size, hatching rates, and reproductive success of SWWA did not differ significantly between habitats. These results, coupled with similar patterns of habitat use at the nest site, suggest that the habitats are ecologically analogous for breeding. Similarities in morphology and behavior also suggest that ecotypic variation does not account for differences in ecological success or patterns of habitat selection in the two forest types Predictions about habitat selection mechanisms were tested based on the foraging behaviors and nesting requirements of SWWA at specific scales. I found support for four hypotheses (Foraging Substrate, Potential Nest Site, Nest Decoy, and Nest Concealment), demonstrating that SWWA use different cues at the habitat, territory, nest patch, and nest site scales, but consistently across habitat types. Vegetation characteristics contributing to the nesting and foraging needs of this species served as mechanisms for habitat selection These results support the conclusion that SWWA has expanded its breeding range into an anthropogenic habitat that meets its basic nesting requirements, despite structural and floristic differences between the two forest types. The implication of these findings is that the conservation value of the enormous area of commercial pine plantations in the southeastern United States can be significantly augmented by appropriate management choices / acase@tulane.edu

The woody vegetation in 317 plots totaling 3.17 hectares was sampled in the forest of the Calakmul Biosphere Reserve, Campeche, Mexico. All stems greater than 2.5 cm diameter at breast height were measured; diameter and vernacular name (Maya or Spanish), along with scientific name, if known in the field, estimated height, slope, presence of ruins, and soil type were recorded. A total of 16,113 stems were measured, representing 138 taxa in 44 families; 105 taxa were identified to species level, 24 to genus, and 5 to family. Vines were only counted as a life form, due to the difficulty of securing specimens for determination. Three uncommon taxa were not identified, described only by Maya common name. Using Maya soil classification terminology, data were used to describe major plant communities on the most important soil types, and to develop an Indicator Species Analysis. Six possible Indicator Species were analyzed by an autobinomial regression, using a Gibbs sampler based on the Markov Chain Monte Carlo method, to test the statistical significance of the Indicator Values. The coefficients for three species were positive and statistically significant; the coefficients for two species were negative and statistically significant; and the coefficient for one species was not statistically significant Brosimum alicastrum (Moraceae) (n.v. ramon) was the dominant tree (measured in square decimeters per hectare) overall (all plots on all soils considered together), and was also the dominant tree on yaxhom (upland) soil, near ruins, on ruins, and on kakab, an anthropogenic soil created by many centuries of human activity on the site. Indicator species analysis showed B. alicastrum to be a strong indicator for the presence of ruins and anthropogenic soil, taking into account neighbor effects. Talisia olivaeformis and Manilkara zapota also show a significant positive association with ruins and the areas around ruins. T. olivaeformis is an important fruit tree in the Yucatan Peninsula today, and was undoubtedly so in antiquity. M. zapota yields fruit, latex, and a very hard, durable wood. The autobinomial regression technique confirmed the statistical significance of the indicator values. Haematozylum campechianum (Leguminosae) was the dominant tree on akalche soil, which is found in lowland seasonal swamps (bajos) The findings, including plant community demographics, statistical and graphic techniques, and historical and archaeological evidence, provide confirmation for the thesis that Brosimum alicastrum is a strong and reliable indicator of sites of former human habitation. These findings also support the hypothesis that B. alicastrum was managed and selected by the Lowland Maya as a staple food. The importance of B. alicastrum as a reliable food source in ancient times, especially before the introduction of Zea mays into the Maya lowlands, probably led to the intensive cultivation, management, and artificial selection of the species. The ramon on the site in modern times likely represents a population which has co-evolved in response to large-scale changes in the landscape and ecology of the forest of southern Campeche and nearby areas. Therefore, the abundance of B. alicastrum on ruin sites can be most parsimoniously explained as a kabab effect, rather than a ruin effect / acase@tulane.edu

Habitat fragmentation impacts on bird communities are relatively well studied in the temperate zone, where brood parasites and non-forest predators are the main causes of declining avian biodiversity. However, life history traits of tropical species suggest different and more diverse effects of habitat fragmentation on tropical bird communities. This dissertation used historical data and quantitative comparisons of fragmented and control sites to infer causes and patterns of tropical avian community response to fragmentation in Central America. Particular ecological guilds, namely forest understory insectivores, mixed-species flock participants, and birds that nest on or near the ground declined or disappeared from La Selva Biological Station, Costa Rica since the 1950s as the site became increasingly isolated from other forest. Spot-maps of twenty-two insectivorous bird species at La Selva in the 1970s indicate that insectivore populations were probably never large enough to be viable, emphasizing the need for larger reserves given the low density of many tropical forest species. Comparisons of four forest sites (24.6-1200 ha) to an non-fragmented control site in southeastern Nicaragua show significant reduction in biodiversity, corresponding decline in total bird abundance, and changes in community composition, even in the larger sites. Lack of change in the Nicaraguan control site suggests landscape changes rather than climate change is the most parsimonious explanation for community changes in the fragments. Finally, comparison of community changes in two large isolated forest reserves, La Selva and Barro Colorado Island, Panama, demonstrate similar patterns of losses of insectivores and low nesting species. However, landscape level and climatic differences between the two sites also affect the ability of some species to persist in remaining forest. Overall, this dissertation suggests that deterministic factors, especially ecological characteristics, put particular species at risk to landscape changes. No single mechanism appears to explain all the patterns, but small population size, poor dispersal ability, and increase in nest depredation are implicated by this study. Further investigation is needed to assess the relative importance of these and other mechanisms. Moreover, trophic cascades involving other taxa are predicted as a result of the lack of ecological replacement of disappearing specialized forest insectivores / acase@tulane.edu