Marine Corps Air Ground Combat Research Articles

Hunter-Gatherer Settlement Patterns in the South-Central Mojave Desert: Perspectives from Emerson Lake, San Bernardino County, California

ABSTRACT This article briefly explores the archaeological signatures of Early through Late Holocene resource use and hunter-gatherer settlement patterns near Emerson Lake aboard the Marine Corps Air Ground Combat Center. Investigations of 156 localities along a linear belt of probable plant biomass modeled through Normalized Difference Vegetation Index assessments registered larger, richer, and more diverse assemblages containing significantly higher frequencies of resource-processing artifacts, such as flake tools and ground stone, nearer this belt than predicted by random distribution, suggesting that hunter-gatherer encampments, reflecting the utilization of recurring abundant seasonal biotic patches, targeted this belt. However, other than upticks in processing artifact numbers and proximity to the belt during the 1,000 years prior to European contact, archaeological assemblage profiles remain comparatively constant, implying little deviation in the way local hunter-gatherers utilized and settled around this landscape throughout the Holocene.

Installation Tobacco Control Programs in the U.S. Military.

Tobacco use prevalence is unacceptably high in the U.S. military, and the Department of Defense and service branches have implemented tobacco control policies and cessation programs. To explore aspects of programs regarded as exemplary by their services, we visited four installations, nominated by their service's health promotion leaders, and conducted interviews, observations, and focus groups. Installations included Naval Hospital Guam, Tripler Army Medical Center, MacDill Air Force Base, and the Naval Hospital at Marine Corps Air Ground Combat Center Twentynine Palms. The tobacco control managers (TCMs) at the programs studied were all civilian employees, highly motivated and enthusiastic, and had remained in their positions for approximately a decade. Other commonalities included support from command, a "culture" of health, and location in warm climates. Programs varied in their involvement in establishing designated tobacco use areas, and length and requirement of attending cessation classes; however, no evaluation of cessation programs is currently underway. TCMs should be more engaged in policy discussions for the larger installations they serve. A strong policy framework and command support for TCMs will be necessary to achieve the goal of a tobacco-free military.

Identifying Climate Refugia: A Framework to Inform Conservation Strategies for Agassiz's Desert Tortoise in a Warmer Future

Abstract Agassiz's desert tortoise, Gopherus agassizii, faces threats from climate change. With limited mobility to move long distances to more-suitable habitat as climate change advances, whether protecting tortoises in situ or translocating them out of harm's way, a critical conservation task is identifying refugia, lands that will remain suitable under the current climate and the projected, end of the 21st Century warming and drying. While researchers have modeled tortoise habitat suitability, they have done so at coarse scales and did not identify climate refugia that may become apparent only with a fine-scale approach. It is at that scale that managers can implement measures that will foster habitat protection for tortoises throughout their current range. In this case study, we employed fine-scale habitat suitability modeling to identify current habitat and climate refugia within and surrounding the Marine Corps Air Ground Combat Center (MCAGCC) at Twentynine Palms, California. We modeled nearly 284,...

Late Pleistocene to Middle Holocene Archaeology in the Mojave Desert: Recent Discoveries in Twentynine Palms, California

This article introduces late Pleistocene through middle Holocene archaeology at the Marine Corps Air Ground Combat Center, Twentynine Palms, California, illuminated by recent discoveries built on data gathered during 30+ years of cultural resource management efforts. We report on a Clovis biface and dating of terminal Pleistocene geological deposits.

Polyandry and multiple paternities in the threatened Agassiz’s desert tortoise, Gopherus agassizii

We used data from 17 to 20 microsatellite markers to investigate the incidence of multiple paternities in wild Agassiz’s desert tortoises, Gopherus agassizii. Neonates were sampled from clutches of eggs laid by wild mothers in nesting enclosures at Edwards Air Force Base and at the Marine Corps Air Ground Combat Center, California. We genotyped 28 clutches from 26 females sampling an average of six neonates per clutch. The number of paternal alleles was used to determine the minimum number of sires for each clutch. Based on conservative criteria requiring evidence from at least two loci to determine multiple paternity, a minimum of 64% of females were polyandrous, while a minimum of 57% of clutches were sired by multiple males. This formed one of the highest incidences of multiple paternities recorded to date in any species of tortoise. The high number of microsatellite loci involved in the analyses allowed detection of multiple paternities in clutches where this may have been missed if fewer loci were used. Our results highlighted the potential pitfalls of quantitatively comparing paternity studies based on differing sampling strategies. Finally, we summarized the conservation implications of the high rate of multiple paternities in this threatened species.

A Procedure to Extrapolate Vegetation Cover Estimates Over Large Arid and Semi‐arid Regions Using Multiple Spatial Resolution Imagery

Typically, land degradation on arid and semi‐arid military training and testing lands in the desert Southwestern United States is associated with a decrease in total vegetative cover. Long‐term field surveys have been established by the military to measure and monitor total vegetative cover over time. However, field methods are not cost effective due to the large area of training lands, nearly 3 million acres in the California deserts alone, that must be sampled. Measurements recorded at individual transects must still be spatially extrapolated to produce a complete census of the installation. Remote sensing has been used to spatially extrapolate such field measurements over larger areas, but in the past, imagery has lacked sufficient spatial resolution to accurately estimate total vegetative cover. In this study, nested, high resolution imagery was collected at different spatial resolutions for study sites at the Marine Corps Air Ground Combat Center in the south‐central Mojave Desert of southern California. Vegetation cover estimates derived from these multiple resolution images were examined as a possible surrogate for sampling total vegetative cover in the field. Results indicate that a high correlation exits between field measurements of cover and estimates of cover derived from imagery. However, similar to field measurements, if the intent is to estimate total vegetative cover across large geographic areas, high resolution imagery is also costly in terms of collection, processing, and interpretation because a single image generally covers a small geographic area. Therefore, a protocol to scale detailed observations of total cover from high resolution imagery to lower resolution imagery that covers a larger geographic area was developed and tested. The results of this study indicate that a relatively high correlation exists between vegetation cover estimates derived from high resolution imagery and image brightness derived from a nested, lower resolution image. This protocol now allows military land managers to sample site‐specific areas with high resolution imagery and extrapolate absolute estimates of vegetation cover across training and testing lands with more cost effective, lower resolution imagery that provides complete coverage of an installation.

Survival during Early Life Stages of the Desert Tortoise (Gopherus agassizii) in the South-Central Mojave Desert

Early age classes of the Desert Tortoise (Gopherus agassizii) are particularly vulnerable to predation by several mammal and bird species. We studied tortoise survival at the Sand Hill Training Area of the Marine Corps Air Ground Combat Center, Twentynine Palms, California, from 1998 to 1999. We radiographed and thread-spooled 25 females to determine reproductive and nesting ecology. Predators consumed 11 of 42 monitored nests during the first 70 days of incubation. Ninety-one of 132 eggs in nests fenced after 70 days developed into healthy neonates. We recorded 0.84 and 0.91 neonate survival probability during dispersal in 1998 and 1999, respectively. Applying neonatal survival to egg success, we predict that 40% of individuals survived from oviposition to hibernation. Our findings support other chelonian life-history models indicating relatively high mortality early in life. Our data also suggest that neonatal Desert Tortoises are less susceptible to predation than was previously thought, perhaps because of their cryptic coloration and secretive habits. The Common Raven (Corvus corax) was not found to be a source of neonate mortality during this study.

Wind erosion from military training lands in the Mojave Desert, California, U.S.A.

Military training activities reduce vegetation cover, disturb crusts, and degrade soil aggregates, making the land more vulnerable to wind erosion. The objective of this study was to quantify wind erosion rates for typical conditions at the Marine Corps Air Ground Combat Center, Twentynine Palms, CA, U.S.A. Five Big Spring Number Eight (BSNE) sampler stations were installed at each of five sites. Each BSNE station consisted of five BSNE samplers with the lowest sampler at 0·05 m and the highest sampler at 1·0 m above the soil surface. Once a month, sediment was collected from the samplers for analysis. Occurrence of saltating soil aggregates was recorded every hour using Sensits, one at each site. The site with the most erosion had a sediment discharge of 311 kg m −1 over a period of 17 months. Other sites eroded much less because of significant rock cover or the presence of a crust. Hourly sediment discharge was estimated combining hourly Sensit count and monthly sediment discharge measured using BSNE samplers. More simultaneously measured data are needed to better characterize the relationship between these two and reconstruct a detailed time-series of wind erosion. This measured time-series can then be used for comparison with simulation results from process-based wind erosion models such as the Wind Erosion Prediction System (WEPS), once it has been adapted to the unique aspects of military lands.