Carl A. Reese

Pollen Dispersal and Deposition on the Quelccaya Ice Cap, Peru

The relatively young science of tropical ice-core palynology has proven effective in the study of paleoenvironments by its ability to produce long-term and highresolution paleoclimatic data. However, no studies thus far have investigated the basic dispersal and depositional processes of pollen on these tropical ice caps. In this study, 15 surface snow samples were taken along an east-west transect on the Quelccaya Ice Cap in southern Peru. Results show that pollen assemblages remain fairly uniform across the ice surface, suggesting a uniform mixing of the air mass and its pollen contents over the ice cap. The pollen concentrations, ranging between 17,250 and 55,400 grains/liter, are the highest ever found on a tropical or nontropical ice cap. Concentrations were highest toward the western edge of the ice cap, suggesting that the prevailing winds may have a greater influence on pollen dispersal than other diurnal winds. These results are the first step in understanding the fundamental questions of modern pollen-rain and depositional processes on a tropical ice cap, which are essential for reliable and accurate interpretation of ice-core pollen data.

Pollen Dispersal and Deposition on the Ice Cap of Volćan Parinacota, Southwestern Bolivia

Abstract Pollen, a regular component of tropical ice cores, has been shown to have great potential as a sensitive paleoenvironmental proxy in ice-core research. However, questions remain as to the modern dispersal and depositional patterns of pollen on high-alpine tropical ice caps. This information is vital to the accurate interpretation of the environmental reconstructions being derived from fossil pollen. In this study, 11 surface snow samples were collected around the caldera rim at the summit of Mt. Parinacota along the Bolivian-Chilean border. Results show that pollen concentration and assemblage are uniform in samples taken from the southwestern quadrant and the entire eastern half of the mountain. However, the pollen signatures are significantly different in the northwestern quadrant, probably due to long-distance transport of xerophytic Compositae shrub pollen from the prevailing winds. The sections of the mountain not directly impacted by the prevailing northwesterlies reflect a more locally influenced pollen assemblage dominated by grasses. These results are consistent with previous findings from the Quelccaya Ice Cap and confirm the importance of the prevailing winds in the dispersal and deposition of pollen on these high-alpine tropical ice caps.

Interannual Variability In Pollen Dispersal and Deposition On the Tropical Quelccaya Ice Cap

Abstract Pollen collected from snow samples on the Quelccaya Ice Cap in 2000 and 2001 reveals significant interannual variability in pollen assemblage, concentration, and provenance. Samples from 2000, a La Niña year, contain high pollen concentrations and resemble samples from the Andean forests (Yungas) to the east. Samples from 2001, an El Niño year, contain fewer pollen and resemble those from the Altiplano. We suggest that varying wind patterns under different El Niño/Southern Oscillation (ENSO) conditions may affect the processes of pollen transport over the Altiplano and on the ice cap, although confounding variables such as flowering phenology and sublimation should also be considered *The authors would like to thank Lonnie G. Thompson, Keith R. Mountain, and Jason K. Blackburn for their help in the field, as well as Jocelyne C. Bourgeois and Robert V. Rohli for useful discussion. A special thanks to Mary Lee Eggart for cartographic assistance. This research was jointly supported by the Geography and Regional Science Program, the Paleoclimatic Program, and the Americas Program of the National Science Foundation (NSF grants BCS-9906002, BCS-0117338, and BCS-0217321). Additional support for this project came from doctoral dissertation grants from the Geological Society of America, the Association of American Geographers, the Sigma-Xi National Research Society, and the Department of Geography and Anthropology at Louisiana State University.

Geologic Evidence of Hurricane Katrina Recovered from the Pearl River Marsh, MS/LA

Abstract Hurricane Katrina made its final landfall on August 29, 2005, as a category three storm, at the mouth of the Pearl River on the Mississippi/Louisiana border. Between October and December of 2005, 16 cores were recovered along two transects in the Pearl River Marsh: one running east to west across the mouth of the delta, and the other running south to north through the center of the basin. Loss-on-ignition and grain-size analysis clearly identified the sediments deposited by the storm and the resulting 5.9 m storm surge. The inorganic storm layer consisted of fine grain sands and silts, which were easily distinguished from the organic peat that develops naturally in the marsh. Although the Pearl River Marsh received uniform storm surge, the storm layer was unevenly distributed and was thicker and more pronounced toward the center of the marsh. The funneling of the storm surge by the floodplain terraces and/or the winnowing effect of wave action could account for this variability. Only 5 of the 16 cores showed evidence of Hurricane Camille, which made landfall near the Pearl River Marsh, as a category five storm, in 1969. Erosion and bioturbation of the marsh sediments could have worked to blur or even erase this layer in some locations, which would explain the inconsistent record. If this level of variability and degradation is common for marsh environments, it presents a challenge to paleotempestological investigations from these areas and emphasizes the importance of environmental reconstructions based on multiple transects of cores.

Geologic Evidence of Hurricane Rita Recovered from Texas Point, TX

Hurricane Rita made landfall at the Texas/Louisiana border on 24 September 2005 as a category 3 hurricane. In November 2006, four cores were recovered along a north-south transect from the marsh at Texas Point, TX. Loss-on-ignition and grain size analysis identified the inorganic storm layer (consisting of fine-grained sands and silts) deposited as a result of this event. Results show that the sediment pushed inland by the 3 m storm surge was unevenly distributed along the transect. Areas of open water (i.e. small lakes) along the transect provide a different depositional environment than the vegetated marsh surface and affect the characteristics of the storm layer, and thus potentially the interpretation of the hurricane history. This variability suggests that great caution is required when reconstructing past hurricane activity in marsh environments, especially when storm layer thickness is being used for the estimation of past hurricane strength.

An Old Dog With New Tricks: An Automated, Dry-Deposition Tauber Trap

Establishing a modern pollen analogue for remote, high‐deposition environments (e.g. ice caps) presents a unique problem that is difficult to address with current technology. Collecting modern pollen with traditional Tauber traps in these locations (at sub‐annual resolution) is nearly impossible due to the time and costs involved in frequent, long‐distance or remote travel. Presented in this paper is an automated, dry‐deposition Tauber trap with the ability to open and close on a timer, which allows for pollen collection at programmable intervals. This new trap (along with three traditional Tauber traps) was field tested in the summer of 2005 at the University of Colorados Niwot Ridge Long‐Term Ecological Research Station (LTER) located in the Front Range of the Colorado Rockies. During the research, one of the traditional traps became damaged and was subsequently discarded from the study. Significant variability in pollen concentrations and percentages was found in the remaining traps. Statistical tests revealed that the pollen assemblage collected in the automated trap was statistically no different to the pollen collected in the traditional Tauber traps. Field testing in a cold, high‐wind environment also revealed the weaknesses of acrylic as a trap material, and identified several improvements that could be made to the overall design. Further testing aside, this modified, automated Tauber trap now permits modern pollen rain studies at higher resolutions in more remote locations.

Late-Holocene Vegetation Changes at Bluff Swamp, Louisiana

Stratigraphic pollen studies on two short cores taken from Bluff Swamp, a cypress backwater swamp in southeastern Louisiana, have provided a proxy record of late-Holocene vegetational changes in the area. Results show that during AD 1100-1700, the area was dominated by a dense Taxodium (cypress) swamp. Throughout this time, cypress populations declined steadily, perhaps due to a gradual rise in the water level of the swamp. Around AD 1700 there was a dramatic change in the environment, marked by a sudden decrease in Taxodium and a subsequent rise in heliophytic, early-successional taxa, due to European settlement. In 1950, the U.S. Corps of Engineers constructed a levee that bisects the swamp. This, and other recent anthropogenic disturbance, has resulted in massive cypress die-off due to the widespread ponding of this fragile environment.

Impact of Prescribed Burns on Marsh Surface Elevation: Big Branch Marsh, Louisiana

This study examines the impact of prescribed burning on marsh elevation by comparing relative surface elevation change between burned and unburned control marsh plots using a Surface Elevation Table (SET) at Big Branch Marsh National Wildlife Refuge in St. Tammany Parish, LA. This project was developed in conjunction with the U.S. Fish and Wildlife Service and serves as the foundation for a long-term program for evaluating the effects of burning on marsh surface elevation. Three years after the initial burn, results indicate there was no significant difference in surface elevation change between the island receiving the burn treatment and the unburned control island. However, immediately following the burn, elevation differences between the two islands were significant, with the burn plot registering a significant decrease in elevation. The results over the course of the study might have been different had the study area not been impacted by hurricanes Faye, Gustav and Ike less than 5 months after the burn, which deposited a large amount of sediment and erased this initial deficit. These results indicate that while prescribed burning should increase vegetation density, thus increasing organic matter accumulation and potential vertical accretion, the possibility exists that the burn event will create an elevation deficit too large for those gains to overcome. This study also demonstrates the importance of storm-derived sedimentation events in the Gulf Coast marshes.