Mima Mounds Research Articles

Giant root-rat engineering and livestock grazing activities regulate plant functional trait diversity of an Afroalpine vegetation community in the Bale Mountains, Ethiopia

Disturbances from rodent engineering and human activities profoundly impact ecosystem structure and functioning. Whilst we know that disturbances modulate plant communities, comprehending the mechanisms through which rodent and human disturbances influence the functional trait diversity and trait composition of plant communities is important to allow projecting future changes and to enable informed decisions in response to changing intensity of the disturbances. Here, we evaluated the changes in functional trait diversity and composition of Afroalpine plant communities in the Bale Mountains of Ethiopia along gradients of engineering disturbances of a subterranean endemic rodent, the giant root-rat (Tachyoryctes macrocephalus Rüppell 1842) and human activities (settlement establishment and livestock grazing). We conducted RLQ (co-inertia analysis) and fourth-corner analyses to test for trait-disturbance (rodent engineering/human activities) covariation. Overall, our results show an increase in plant functional trait diversity with increasing root-rat engineering and increasing human activities. We found disturbance specific association with traits. Specifically, we found strong positive association of larger seed mass with increasing root-rat fresh burrow density, rhizomatous vegetative propagation negatively associated with increasing root-rat old burrow, and stolonifereous vegetative propagation positively associated with presence of root-rat mima mound. Moreover, both leaf size and leaf nitrogen content were positively associated with livestock dung abundance but negatively with distance from settlement. Overall, our results suggest that disturbances by rodents filter plant traits related to survival and reproduction strategies, whereas human activities such as livestock grazing act as filters for traits related to leaf economics spectrum along acquisitive resource-use strategy.

La presencia de monticulos tipo Mima en la Argentina en relación con roedores del género Ctenomys

The discovery of Mima mounds pocking the Pampean region in the south-east of San Luis, south of Córdoba and north of La Pampa, as well as in some Monte regions in Mendoza, confirms the hypothesis that fossorial rodents are the origin of this type of phenomenon and that such mounds are present in different regions of the world coinciding with the presence of families of fossorial rodents showing similar morphology and behavior.
 This similarity with geomyds of the United States and other families from West and South Africa, becomes evident in Argentine Ctenomydae, which activity is responsible for the formation of this type of relief, Which has nowadays disappeared in most of the central part of the country due to agricultural practices.
 The discovery of Mima mounds in Argentina unquestionably confirms the discussed origin of this type of topographic accident, which has been subject to the most varied interpretations.

Seeing What You Know: How Researchers’ Backgrounds Have Shaped the Mima Mound Controversy

Seeing What You Know: How Researchers’ Backgrounds Have Shaped the Mima Mound Controversy

Leopard predation on gelada monkeys at Guassa, Ethiopia.

Predation is widely believed to exert strong selective pressure on primate behavior and ecology but is difficult to study and rarely observed. In this study, we describe seven encounters between lone wild leopards (Panthera pardus) and herds of geladas (Theropithecus gelada) over a 6-year period in an intact Afroalpine grassland ecosystem at the Guassa Community Conservation Area, Ethiopia. Three encounters consisted of attempted predation on geladas by leopards, one of which was successful. All three attacks occurred in low-visibility microhabitats (dominated by tussock graminoids, mima mounds, or tall shrubs) that provided leopards with hidden viewsheds from which to ambush geladas. An additional four encounters did not result in an attempted attack but still document the consistently fearful responses of geladas to leopards. In encounters with leopards, geladas typically gave alarm calls (n = 7 of 7 encounters), reduced interindividual distances (n = 5), and collectively fled towards or remained at their sleeping cliffs (n = 7), the only significant refugia in the open-country habitat at Guassa. Geladas did not engage in mobbing behavior towards leopards. Encounters with leopards tended to occur on days when gelada herd sizes were small, raising the possibility that leopards, as ambush hunters, might stalk geladas on days when fewer eyes and ears make them less likely to be detected. We compare the behavioral responses of geladas to leopards at Guassa with those previously reported at Arsi and the Simien Mountains and discuss how gelada vulnerability and responses to leopards compare with those of other primate species living in habitats containing more refugia. Lastly, we briefly consider how living in multilevel societies may represent an adaptive response by geladas and other open-country primates to predation pressure from leopards and other large carnivores.

A theoretical foundation for multi-scale regular vegetation patterns.

Self-organized regular vegetation patterns are widespread and thought to mediate ecosystem functions such as productivity and robustness, but the mechanisms underlying their origin and maintenance remain disputed. Particularly controversial are landscapes of overdispersed (evenly spaced) elements, such as North American Mima mounds, Brazilian murundus, South African heuweltjies, and, famously, Namibian fairy circles. Two competing hypotheses are currently debated. On the one hand, models of scale-dependent feedbacks, whereby plants facilitate neighbours while competing with distant individuals, can reproduce various regular patterns identified in satellite imagery. Owing to deep theoretical roots and apparent generality, scale-dependent feedbacks are widely viewed as a unifying and near-universal principle of regular-pattern formation despite scant empirical evidence. On the other hand, many overdispersed vegetation patterns worldwide have been attributed to subterranean ecosystem engineers such as termites, ants, and rodents. Although potentially consistent with territorial competition, this interpretation has been challenged theoretically and empirically and (unlike scale-dependent feedbacks) lacks a unifying dynamical theory, fuelling scepticism about its plausibility and generality. Here we provide a general theoretical foundation for self-organization of social-insect colonies, validated using data from four continents, which demonstrates that intraspecific competition between territorial animals can generate the large-scale hexagonal regularity of these patterns. However, this mechanism is not mutually exclusive with scale-dependent feedbacks. Using Namib Desert fairy circles as a case study, we present field data showing that these landscapes exhibit multi-scale patterning-previously undocumented in this system-that cannot be explained by either mechanism in isolation. These multi-scale patterns and other emergent properties, such as enhanced resistance to and recovery from drought, instead arise from dynamic interactions in our theoretical framework, which couples both mechanisms. The potentially global extent of animal-induced regularity in vegetation-which can modulate other patterning processes in functionally important ways-emphasizes the need to integrate multiple mechanisms of ecological self-organization.

Critiques of the seismic hypothesis and the vegetation stabilization hypothesis for the formation of Mima mounds along the western coast of the U.S.

A recent paper published in Geomorphology by Gabet et al. (2014) presents the results of a numerical model supporting the hypothesis that burrowing mammals build Mima mounds - small, densely packed hillocks found primarily in the western United States. The model is based on field observations and produces realistic-looking mounds with spatial distributions similar to real moundfields. Alternative explanations have been proposed for these Mima mounds, including formation by seismic shaking and vegetation-controlled erosion and deposition. In this short communication, we present observations from moundfields in the coastal states of the western U.S. that are incompatible with these alternative theories.

Cumulative effects of an herbivorous ecosystem engineer in a heterogeneous landscape

AbstractForaging by herbivores alters individual plants and vegetation communities directly, and engineering behaviors such as bioturbation (digging and turning soil) and biodeposition (deposition of feces and urine) can affect soils and physical properties that indirectly influence vegetation and other organisms. Patchy environments often concentrate the activities of animals, potentially increasing the magnitude of their impacts on the vegetative community over time. To evaluate the potential for herbivorous engineers to enhance existing heterogeneity, we quantified the direct and indirect effects of a burrowing herbivore, the pygmy rabbit (Brachylagus idahoensis), on soil and vegetation in the sagebrush steppe ecosystem of the western United States, and we evaluated whether the effects were related to duration of occupancy by rabbits. Mounded microtopography (i.e., mima mounds) creates distinct resource islands with relatively tall and dense sagebrush shrubs where pygmy rabbits concentrate burrowing and foraging activities. We quantified soil and vegetation characteristics on mima mounds occupied by rabbits for 1–12 yr and on unoccupied mounds. We expected that browsing would negatively influence slow growing sagebrush shrubs, but that digging and biodeposition would enhance soil nutrients and water infiltration. In addition, we hypothesized that the net effect on sagebrush reproduction would be positive because indirect effects on soil would enhance seed production by mature sagebrush and seedling growth, and because bioturbation would increase seed retention and germination. Pygmy rabbit occupancy had significant cumulative effects on both soil and vegetation properties on occupied mima mounds. Over time, browsing reduced sagebrush canopy cover and percent of individual shrubs that were alive. Soil properties were less influenced by the duration of occupancy of mima mounds than by the localized spatial influence of burrowing; elevated nitrogen levels were associated with burrow entrances. Two measures of sagebrush reproduction (seedling recruitment and inflorescence biomass) increased with duration of burrow occupancy, suggesting that over longer time frames pygmy rabbits enhanced reproduction and recruitment of sagebrush shrubs. Our data demonstrate multiple pathways by which an herbivorous engineer can influence habitat heterogeneity, and they suggest that although pygmy rabbits are inconspicuous on the landscape, the species might play an important role in maintaining and augmenting heterogeneity in the sagebrush steppe.

Mysterious Mima mounds may be due to gopher activity

Mysterious Mima mounds may be due to gopher activity

Biotic origin for Mima mounds supported by numerical modeling

Mima mounds are ~1-m-high hillocks found on every continent except Antarctica. Despite often numbering in the millions within a single field, their origin has been a mystery, with proposed explanations ranging from glacial processes to seismic shaking. One hypothesis proposes that mounds in North America are built by burrowing mammals to provide refuge from seasonally saturated soils. We test this hypothesis with a numerical model, parameterized with measurements of soil transport by gophers from a California mound field, that couples animal behavior with geomorphic processes. The model successfully simulates the development of the mounds as well as key details such as the creation of vernal pools, small intermound basins that provide habitat for endemic species. Furthermore, we demonstrate that the spatial structure of the modeled mound fields is similar to actual mound fields and provides an example of self-organized topographic features. We conclude that, scaled by body mass, Mima mounds are the largest structures built by nonhuman mammals and may provide a rare example of an evolutionary coupling between landforms and the organisms that create them.

Geology and Topography Effects on Exotic Plant Distribution in a Semiarid Mima Mound Prairie in Eastern Washington

Native prairie plant communities are among the most endangered habitats due to extensive agricultural use and exotic species invasion. Understanding how species composition, particularly of exotic species, varies with environment is essential for management and preservation of these communities. In semi-arid prairies, plant establishment is often heterogeneous across the landscape and depends on the patchy availability of resources across environmental gradients. We studied how soil geologic substrate, topography, and grazing history relate to patterns of native and exotic plant distribution in a semiarid Mima mound prairie in eastern Washington. We analyzed the relationship between native and exotic species richness and abundance on 61 Mima mounds in a prairie underlain by two types of soil geologic substrate (glacial alluvium and basalt) where half of each had been grazed recently. We found that exotic species richness and cover were lowest and native species cover was highest on mounds underlain by basalt bedrock that had experienced recent grazing; on sites underlain by glacial alluvium there was little difference between more and less recently grazed mounds. Moreover, we found that exotic abundance was greatest at the top of Mima mounds compared to the sides; the opposite was true for native species. Our findings indicate that geologic substrate and grazing history may interact to determine plant distribution in semi-arid prairie communities. This study demonstrates that land managers aiming to restore native plant communities need to consider the synergistic effects of multiple environmental factors in order to focus restoration funding and effort.

A New Species ofHymenoxys(Asteraceae, Helenieae, Tetraneuridinae) from Texas

Hymenoxys perpygmaea W. C. Holmes, Singhurst & Mink (Asteraceae, Helenieae, Tetraneuridinae) is described as a new annual species. The species, which is ephemeral, is endemic to an alfisol prairie that contains mima mounds in Lamar County from northeastern Texas, U.S.A. It is similar to H. texana (J. M. Coult. & Rose) Cockerell, but is easily distinguished from that species by its diminutive rosette and fewer florets per capitulum.

Rare inland reindeer lichens at Mima Mounds in southwest Washington State.

Isolated populations of four reindeer lichen species and varieties co-occur in a unique relict prairie habitat at Mima Mounds Natural Area Preserve, southwest Washington State, USA. The prairie is the type locality for mima mounds, unusual geologic features providing topographical variation that influences vegetation patterns. Reindeer lichens ( Cladonia subgenus Cladina ) are usually more typical of northern boreal regions and are very rare in inland valley habitats of the western states outside of Alaska. Our study established distributional, ecological, chemotypic, and phylogenetic information for the target species. The species that at first appeared to be C. arbuscula was revealed by DNA sequences to be C. ciliata var. tenuis . We found that topography was not as important as recent fire history in explaining reindeer lichen distribution; in the future, prescribed fire is likely to benefit reindeer lichens so long as it preserves pockets of refugia as propagule sources. We also detected moderate air pollution stress, which is projected to have impacts on lichen abundances and community compositions in the near future. Chemotype analysis revealed 6 reindeer lichen chemotypes, of which 2 are rare (C. ciliata var. tenuis and C. portentosa subsp. pacifica f. decolorans ). Phylogenetic analyses supported previous species concepts, showing C. portentosa is distinct from the closely-related group that includes C. rangiferina and two varieties of C. ciliata . We synthesized our findings to provide a key for distinguishing the reindeer lichens of Mima Prairie. We suggested that rare inland reindeer lichens may benefit from small prescribed burns and sowing of propagules in disturbed areas, as well as continued monitoring and designation as state sensitive species.

Use of Soil Properties to Determine the Historical Extent of Two Western Washington Prairies

Abstract The Pacific Northwest, a region known for mesic coniferous forests, is also home to scattered prairies, which have been maintained by a combination of xeric site conditions and anthropogenic fires. These prairies, which existed for thousands of years, have been reduced to 2–4% of their historical extent over the past two centuries due to urban development, agriculture, and forest encroachment. We used soil properties, including organic matter concentration, black carbon concentration, proportion of large black carbon particles and moist color, to determine the historical location of prairie-forest ecotones at Mima Mounds and American Camp prairies. Based on these parameters, we conclude that Mima prairie historically extended 50 m north and 300 m east of the current ecotone. In contrast, at American Camp all sampled areas that are currently forested appear to have been grassland at some time in the past. Soils can provide an effective means of determining historical prairie boundaries.

Evidence for a geochemical origin of the mysterious circles in the Pro-Namib desert

The origin of the so-called “fairy circles” has not yet been established. Carbon monoxide (as an indicator of a natural gas microseep) was monitored inside and outside of the selected fairy circles in the Namib, Namibia, Southern Africa. Hydrocarbons were extracted from the soil by a novel method for trapping analytes onto silicone rubber designed for thermal desorption into a gas chromatograph–mass spectrometer (GC–MS). Unresolved complex mixtures with resolvable alkanes were detected in soil collected from two newly formed circles. Alkenes, the microbial degradation product of alkanes (microbial food source), were more abundant in the circles compared to the levels of alkenes detected in the matrix between circles. Results show a microseepage of gases and hydrocarbons which is expressed at the surface as a geobotanical anomaly of barren circles and circles of altered vegetation. In addition, this finding may suggest a new approach to the origin of the mima mounds ( heuweltjies) of the Western Cape in South Africa.

Notes on Native Vascular Plants from Mima Mound-Vernal Pool Terrain and the Importance of Preserving Coastal Terraces in Orange County, California

We report the following noteworthy collections of native vascular plants from mima mound fields in coastal Orange County, California: Deschampsia danthonioides, Lepidium strictum, and Sagina saginoides (new county records), Lepidium oblongum var. oblongum (previously excluded from the flora), Deinandra paniculata, Holocarpha virgata subsp. elongata, and Navarretia prostrata (new localities in the county), and Hordeum brachyantherum subsp. californicum (uncommon species of local interest). A herbarium study, preparation of voucher specimens, and a generalized distribution, facultative wetland status, and taxonomic notes, where appropriate, are cited for each taxon. An overview of the mima mound micro-relief associated with coastal terraces in southern California is also provided.

Paleoseismic features as indicators of earthquake hazards in North Coastal, San Diego County, California, USA

New road cut and mass-grading excavations in the north coastal area of San Diego County, California expose heretofore generally unrecognized, probable late Holocene tsunami deposits and paleoseismically deformed sediments. Remnant tsunami deposits occur up to 100 + m in elevation around the margins of modern coastal lagoons and estuaries and, combined with local mima mounds of possible sand blow origin, provide indirect but compelling evidence for the late Quaternary activity of onshore and offshore faults in the immediate study area. Probable paleoliquefaction features are regionally widespread and range from fissures filled with sediments derived from overlying marine terrace sand and soil, to the more traditional sand-filled injection dikes and sills, lateral spreads, and filled craterlets. The source of most liquefied sediment is underlying Tertiary “bedrock sand” and local, Quaternary marine-terrace deposits. A paleoseismic liquefaction origin rather than soft-sediment loading is deduced for these features based on morphology, internal stratigraphy, field setting, and near proximity to known seismogenic sources. Some paleoseismic events impacted late Holocene Indian middens and burial sites. The last seismic event probably occurred within the past 1 to 3 ka, and possibly even records the historic earthquakes of either November 22, 1800 or May 27, 1862. The liquefaction features also affect marine terrace sediments tens of meters above modern regional water levels, inferentially “recording” paleoseismic events in this Mediterranean-type climatic region during winter rains when high-level, perched water saturates the several meter thick source sediments. Based on their regional extent, the paleoseismic features were likely caused by M ∼ 7+ tectonic events inferentially generated by the nearby offshore Newport–Inglewood/Rose Canyon fault system, or possibly by smaller, recently exposed, related and localized faults. Accordingly, the seismic hazard of the north coastal area of San Diego County may be substantially higher than previously assumed, and hence of concern owing to the rapid ongoing and projected population increase.

Total Eclipse: The Destruction of the African American Community of Harrison, Arkansas, in 1905 and 1909

FOR MOST OF THE TWENTIETH CENTURY, Harrison, Arkansas, was all white. This homogeneity was not always the case, however, nor was it achieved without bloodshed. census taken in Harrison in April of 1900 lists 1,501 residents. Of that number, 115 were African American or of mixed race. A decade later, census takers in Harrison recorded an African American population of one. Two separate episodes of mob activity, in 1905 and 1909, destroyed Harrison's black community. A dearth of local coverage from the period, combined with uncertain memories that have been conflated into a single and inaccurate, they hung a nigger from the bridge, have obscured what actually occurred. Files of the Harrison newspaper have gaps that coincide with the events of 1905 and 1909. However, reports in other papers around the state, federal court records, and one eyewitness account make an examination of these events possible. evidence demonstrates that the ethnic purity of Harrison was the result of intentional violence directed at what had been an established African American community of long standing.' In 1900 Harrison was a diverse, if rather isolated, Ozarks town. Its square consisted of mixed dwellings and businesses of all classes and kinds. Fine Victorian homes overshadowed shacks and vacant lots. A dusty brickyard, the dominant industry of the day, stood where the city park was eventually built. Clemisher Hotel, a frame furniture store, the Boone County Bank, Tyson's General Store, Gamble's Book Store, and Hudson's Grocery drew in many a Saturday crowd from fields and woods.2 At the center stood the courthouse. The fence around it was of boards, former Harrison newspaperman Jessie Russell recalled, furnishing an ample supply of horse-racks. Streets were rendered very unsightly at times on account of the numerous hog wallows. pride of the elite was often cramped by the lack of a stock law.3 Prior to locomotive access, traveling in and out of Harrison proved challenging. Muscled teamsters, continually forced to deal with mud and flooding along their Ozark routes, carefully negotiated the daily stages drawn by three relays of horses. A railway was the only real means of keeping pace with progress, but the expense of engineering and constructing mountainous grades proved to be an obstacle for many years.4 This turn-of-the-century town was home to an apparently stable and rooted black community of fifty-three children and sixty-two adults-thirty-one men and thirty-one women-who were hardworking, religious, and family-centered. Some men worked as day laborers, porters, and in saloons. A few were barbers, shoemakers, blacksmiths, and teamsters; one man was both schoolteacher and preacher. Many of the women worked as cooks, housekeepers, laundresses, and servants.5 In some cases these families can be traced back to the census of 1870 and are referred to in a local history as ex-slaves or descendants of slaves who had come into the county with their white owners.6 Eleven of these families owned their own homes, indicating that blacks felt secure enough to settle in, sign mortgages, and pay off their notes.' According to Boone County historian Ralph Rea, They had their church, their social life, and in the main there was little friction between them and the whites.8 Harrison's black neighborhood was composed of small homes along Rush Avenue and Sycamore Street, running east to Chestnut, then northward up along the Dry Jordan Creek and southeast of Rose Hill Cemetery. A cul-de-sac of black-owned homes was also built at the present location of Woodland Heights School. Typical turn-of-the-century African American settlements were in less than desirable areas of town: Harrison's blacks settled in tracts of bottomland subject to intermittent flooding. Although a few black-owned homes could be found within Harrison's white-;)wned neighborhoods, overall little residential integration existed, as was also typical of early black neighborhood development in the South. …

Implications of Subfossil Coleoptera for the Evolution of the Mima Mounds of Southwestern Puget Lowland, Washington

The origin of Washington State's Mima Mounds has been debated for over a century, with numerous mechanisms being postulated. Subfossil Coleopteran (beetle) remains recovered from the base of a mound at Mima Prairie consist of species that would be expected in rodent burrows and nests; all but one species are obligate burrow inhabitants. These results suggest the past presence of fossorial rodents (probably pocket gophers,Thomomys mazama) in the mounds, although none live there at present. Whether or not the gophers created the mounds, they may well have been instrumental in maintaining mound geometry until very recently.

Mountains and plains: the ecology of Wyoming landscapes

Part 1 Wyoming and the Rocky Mountain West: Landscape History Modern Environments. Part 2 Along Creeks and Rivers: Riparian Landscapes. Part 3 Plains and Intermountain Basins: Grasslands Sagebrush Steppe Desert Shrublands and Playas Sand Dunes, Badlands, Mud Volcanoes, and Mima Mounds. Part 4 Foothills and Mountains: Escarpments and the Foothill Transition Mountain Forests The Forest Ecosystem Mountain Meadows and Snowglades Upper Treeline and Alpine Tundra. Part 5 Landscapes of Special Interest: The Yellowstone Plateau Jackson Hole and the Tetons The Black Hills, Bear Lodge Mountains, and Devil's Tower. Part 6 Sustainable Land Management: Using Wyoming Landscapes. Appendices: Latin Names for Plants Referred to in the Text by Common Name Latin Names for Birds, Mammals, Reptiles, Amphibian, and Invertebrates Referred to in the text by Common Name.

Feeding Ecology of Valley Pocket Gophers (Thomomys bottae sanctidiegi) on a California Coastal Grassland

-San Diego valley pocket gophers (Thomomys bottae sanctidiegi) live on Mediterranean-climate coastal mesas where the growing season occurs during winter. I report seasonal food habits of these pocket gophers in a Mima mound and vernal pool habitat. Diets of 48 individuals collected over 1 yr were assessed by microhistological analysis of stomach contents. Shoots composed more than 70% dry mass of diets throughout the year, peaking at 99% during early spring. Pocket gophers consumed more than 60% dry mass forb shoots from late autumn until early spring, but shifted to 70% grass shoots during summer and early autumn. Belowground tissues and plants restricted to vernal pools were scarce in most diets. Pocket gophers in the genus Thomomys throughout the western United States exhibit striking dietary parallels when seasons are designated according to plant growth stage rather than time of year. Forb shoots appear to be the preferred food, particularly during reproduction; grass shoots, corms and roots increase in importance during plant dormancy.