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openCC (other)Oct 2018View details →

Greenfall litter decomposition of three common species in the northern Chihuahuan Desert, 2010-2012

Soil organic carbon (SOC) is derived primarily from the decomposition of plant biomass. Animals that create greenfall, or green leaf litter, influence SOC dynamics by altering the phenological condition and, therefore, nutrient quality of plant litter. Animals that transport greenfall to a microsite with different microhabitat conditions from those where senesced litter would typically be found also influence SOC dynamics by altering the prevalence of various decomposition drivers. Microsite differences are particularly pronounced in arid and semi-arid ecosystems with heterogeneous vegetation cover. We investigated differences in decomposition between greenfall and senesced litter of three common Chihuahuan Desert plants from which animals frequently generate greenfall (Larrea tridentata, Sporobolus flexuosus, Yucca elata), using a litterbag study to quantify differences in mass, carbon (C), and nitrogen (N) losses between green and senesced leaves placed in shrub intercanopy and subcanopy microsites in a desert shrubland. We hypothesized that decomposition would be more rapid in 1) greenfall than naturally senesced litter, because of the higher nutrient concentration in green than senesced leaves, and 2) in intercanopy than shrub subcanopy microsites, because of increased exposure to decomposition drivers like soil-litter mixing and photodegradation in the less vegetated open area between shrub canopies. Using a litterbag study, we quantified differences in litter mass, C, and N losses between green and senesced leaves placed in shrub subcanopy and intercanopy (open) microsites. Measured variables include litter mass and litter ash, carbon, and nitrogen content. We found that there were significant differences in the nutrient concentration of green and senesced leaves of the same species, and that both litter condition and microsite affected decomposition rate. For two of the three litter species, greenfall decomposed more rapidly than senesced litter, and for all

openOpenMar 2016View details →

Long-term Dynamics in Soil Field Available Nitrogen and Potentially Mineralizable Nitrogen in a Chihuahuan Desert Grassland at the Sevilleta National Wildlife Refuge, New Mexico (1989-2014)

Associated with a project that was based upon the assumption that nitrogen may limit net primary plant production in desert grasslands, this project began measuring available inorganic soil N and potentially mineralizable N of soils at two desert grassland locations. Both available N and potentially mineralizable N were greatest following a drought period in 1989, declined during wetter periods that followed and remained relatively stable until another extended drought period. After drought in 1995-6, both forms of soil N increased, indicating the potential for greater NPP following drought and lower potential NPP during periods of normal precipitation.

openOpenFeb 2016View details →

Ecological Effects of Prescribed Fire on Soils in a Chihuahuan Desert Grassland at the Sevilleta National Wildlife Refuge, New Mexico (2003)

Fire resulting from natural ignition has become a more common event on the Sevilleta National Wildlife Refuge (NWR) since the exclusion of domesticated livestock. Efforts to return fire to the native landscape has resulted in the use of prescribed fire during periods that meet burn prescriptions. A prescribed fire was performed on the Sevilleta NWR in June 2003. Among the measured site and burn characteristics that were measure, this project sampled soils before and after the fire from 5 previously-sampled locations that were burned in June 2003 and from 5 newly established locations that served as controls. The controls were within an area that was sampled between 1989 and 1996 for similar properties measured in this study and had previously been tested to be similar to the locations burned in 2003. The soil properties that are repeatedly measured at the burn and control locations include: field water content; water-holding capacity; organic matter; field extractable nitrate and ammonium; and potentially mineralizable nitrogen.

openOpenJan 2020View details →

Soil Nutrient Distributions in Chihuahuan Desert Grasslands and Shrublands at the Sevilleta National Wildlife Refuge, New Mexico (1989)

Vegetation throughout the southwestern United States has changed from perennial grassland to woody shrubland over the past century. Previous studies on the development of 'islands of fertility' focused primarily on only the most limiting, plant-essential element, soil nitrogen (N). The research presented here addressed the question of whether other plant-essential elements, namely phosphorus (P) and potassium (K), showed similar concentration gradients under the desert shrub Larrea tridentata (creosotebush). It also examined whether the spatial distribution of N, P, and K differed from that of essential, but non-limiting nutrients, namely calcium (Ca), magnesium (Mg), and sulfur (S), and non-essential elements, namely sodium (Na), chloride (Cl), and fluoride (F). Within adjacent grassland and shrubland plots, surface soils were collected under and between vegetation and analyzed for a suite of soil nutrients. Soil nutrient distribution followed a uniform pattern that mirrored the spatial homogeneity of bunchgrasses in the grassland, but followed a patchy distribution that mirrored the spatial heterogeneity of individual shrubs in the shrubland. The main differences were that in the grassland, all elements were uniformly distributed, but in the shrubland the plant-essential elements, nitrogen, phosphorus, and potassium, were concentrated under the shrub canopy, and the non-limiting and non-essential elements were either concentrated in the intershrub spaces or were equally concentrated under shrubs and in the interspaces. Our results show how vegetation shifts from grassland to shrubland contribute to long-term, widespread change in the structure and function of desert ecosystems.

openOpenMar 2016View details →

Livestock Exclosure Nutrient Study from a Chihuahuan Desert Grassland at the Sevilleta National Wildlife Refuge, New Mexico (2003)

Data on soil characteristics and dominant grass and soil chemical composition gathered on active rangeland, livestock exclosures on active rangeland, and the Sevilleta NWR.

openOpenFeb 2011View details →

2003 Prescribed Burn Effect on Chihuahuan Desert Grasses and Shrubs at the Sevilleta National Wildlife Refuge, New Mexico: Shrub Recovery Study (2003-2009)

Disturbance from fire can affect the abundance and distribution of shrubs and grasses in arid ecosystems. In particular, fire may increase grass and forb production while hindering shrub encroachment. Therefore, prescribed fires are a common management tool for maintaining grassland habitats in the southwest. However, Bouteloua eriopoda (black grama), a dominant species in Chihuahuan Desert grassland, is highly susceptible to fire resulting in death followed by slow recovery rates. A prescribed fire on the Sevilleta National Wildlife refuge in central New Mexico in 2003 provided the opportunity to study the effects of infrequent fires on shrub invasion in this region. This study was conducted along a transition zone where creosote bushes (Larrea tridentata) are encroaching on a black grama grassland.

openOpenSep 2010View details →

Soil Surface Dynamics in the Chihuahuan Desert at the Sevilleta National Wildlife Refuge, New Mexico (1994-2013)

Observations of the soil surface on the Sevilleta National Wildlife Refuge indicate that the surface is very dynamic. During collections of decomposition bags it has been noted that the bags are frequently resting on pedestals of soil, often 2-3cm above the surrounding surface. This study will attempt to measure the dynamics of the soil surface using a specially designed soil bridge. The soil bridge will allow for repeated measurements of the relative height of the soil surface at several sites on the Sevilleta. These measurements will be used to assess the impact of the changing soil surface on nutrient cycling.

openOpenMar 2016View details →

Small Mammal Exclosure Study (SMES) Rabbit Feces Data from Chihuahuan Desert Grassland and Shrubland at the Sevilleta National Wildlife Refuge, New Mexico (1995-2005)

The purpose of this study is to determine whether or not the activities of small mammals regulate plant community structure, plant species diversity, and spatial vegetation patterns in Chihuahuan Desert shrublands and grasslands. What role if any do indigenous small mammal consumers have in maintaining desertified landscapes in the Chihuahuan Desert? Additionally, how do the effects of small mammals interact with changing climate to affect vegetation patterns over time? This is data for numbers rabbit fecal pellets counted on each of the Small Mammal Exclosure Study (SMES) plots. Rabbit fecal pellets were counted from each of the 36 one-meter2 quadrats twice each year when vegetation was measured.

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Assembly and origin of the flora of the Chihuahuan Desert: the case of sclerophyllous Rosaceae

Aim To test hypotheses on the origin and assembly of the flora of the Chihuahuan Desert using as a system the hard-leaved shrubby lineages of the Rosaceae distributed in North American Deserts. Location North American Deserts, Chihuahuan Desert, Mexican Plateau, Tehuacán Valley. Methods Phylogenetic analyses were conducted based on nine chloroplast and nuclear molecular markers of eleven newly sequenced species of Rosaceae distributed in the Chihuahuan Desert along with previous sequences of 41 species in 25 genera representative of the major clades in the family. Based on phylogeny, divergence times, migration, vicariance events and ancestral biogeographic areas were determined. Ecological niche-based modeling will predict changes in distribution during Pleistocene climate oscillations. Traitgrams were constructted to visualize departure among lineages in the most significant climate variables. <div>Results The lineages studied diverged during the Eocene-Oligocene (53 – 33Mya). The ancestral area for most of the taxa was in the Mojave and Chihuahuan Deserts. Most dispersal events occurred from the Mojave Desert to the central area of the Chihuahuan Desert on the Mexican Plateau. Ecological niche-based modeling suggests a contraction of suitable habitat during the Last Interglacial period (~120,000 - 140,000 years), followed by expansion during the Last Glacial Maximum (~ 22,000 years) and the Middle Holocene (~ 6000 years). </div> Main conclusions Our results confirm the Axelrod's hypothesis of an origin of the flora of the Chihuahuan Desert in SW North America migrating to occupy North American arid lands. Vicariance and the expansion of arid lands allowed divergence, migration and permanence of the lineages studied on the Mexican Plateau. Divergence occurred prior to the onset of aridification. The Mexican Plateau acted as a refuge for hard-leaved lineages during the Miocene. Shifts in ecological niches of related species allowed them to colonize new areas with different temperatures and precipitation. Current distribution of lineages is the most limited.

opencc-zeroOct 2020View details →

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Data from: Exploring Chihuahuan Desert diversification in the gray-banded kingsnake, Lampropeltis alterna (Serpentes: Colubridae)

Within many biomes, the cause of phylogeographic structure remains unknown even across regions throughout North America, including within the biodiverse Chihuahuan Desert. For example, little is know about population structure or the diming of diversification of Chihuahuan endemics. In part, this is due largely to the lack of population genomic studies within this region. We generated ultra-conserved element data for the gray-banded kingsnake (Lampropeltis alterna) to investigate lineage divergence and historical demography across the Chihuahuan Desert. We found three unique lineages corresponding to the Trans-Pecos and Mapimian biogeographic regions of the Chihuahuan Desert, and a distinct population in the Sierra Madre Occidental. Using several different mutation rates to calibrate the timing of divergence among these lineages, we demonstrate that lineage divergence likely occurred during the Pleistocene. This also suggests that careful consideration needs to be used when applying mutaiton rates to ultra-conserved elements. We suggest that biogeographic provinces within the Chihuahuan Desert may have served as allopatric refugia during climatic fluctuations of the Quaternary. This work serves as an important template for further testing biogeographic hypotheses within the region.

opencc-zeroDec 2017View details →

FIGURE 2 in Two new species of Eucyclops Claus (Copepoda: Cyclopoida) from the Chihuahuan Desert with a redescription of E. pseudoensifer Dussart

FIGURE 2. Eucyclops cuatrocienegas sp. nov., adult female holotype from Cuatro Ciénegas, Coahuila, northern Mexico. A) fifth pedigerous and genital double somites, ventral view; B) mandible with palp; C) detail of gnathal blade; D) antenna; E) maxillule; F) maxilla; G) maxilliped. Scale bars A–G=50 μm.

FIGURE 1 in Two new species of Eucyclops Claus (Copepoda: Cyclopoida) from the Chihuahuan Desert with a redescription of E. pseudoensifer Dussart

FIGURE 1. Eucyclops cuatrocienegas sp. nov., adult female holotype from Cuatro Ciénegas, Coahuila, northern Mexico. A) habitus, dorsal view; B) antennule; C) caudal rami, dorsal view; D) same, ventral view. Scale bars A=100 μm, B–D=50 μm.

FIGURE 5. Eucyclops pseudoensifer Dussart, 1984 in Two new species of Eucyclops Claus (Copepoda: Cyclopoida) from the Chihuahuan Desert with a redescription of E. pseudoensifer Dussart

FIGURE 5. Eucyclops pseudoensifer Dussart, 1984, adult female paratype (MNHN-2547) from Laguna Mucubajì, Venezuela. A) antennule; B) leg 5; C) caudal rami, ventral view; D) same, dorsal view; holotype female, E) right caudal rami, ventral view. E from D. Defaye's drawing of the holotype specimen (in litt.). Scale bars A=50 μm, B= 25 μm, C– E=50 μm.

FIGURE 8. Eucyclops pseudoensifer Dussart, 1984 in Two new species of Eucyclops Claus (Copepoda: Cyclopoida) from the Chihuahuan Desert with a redescription of E. pseudoensifer Dussart

FIGURE 8. Eucyclops pseudoensifer Dussart, 1984, adult male paratype (MNHN-2548) from Laguna Mucubajì, Venezuela. A) leg 3; B) leg 4; C) caudal rami, dorsal view; D) geniculate antennule. Scale bars A–D=50 μm.

FIGURE 7. Eucyclops pseudoensifer Dussart, 1984, A in Two new species of Eucyclops Claus (Copepoda: Cyclopoida) from the Chihuahuan Desert with a redescription of E. pseudoensifer Dussart

FIGURE 7. Eucyclops pseudoensifer Dussart, 1984, A adult female paratype (MNHN-2547) from Laguna Mucubajì, Venezuela. B-D from D. Defaye's drawings of the holotype specimen (MNHN-Cp663) (in litt.).A) leg 4; B) leg 1, coupler and inner margin of coxa and basipod; C) leg 4, ornamentation of coupler; D) leg 3, same. Scale bars A=50 μm, B–D= 25 μm.

FIGURE 10 in Two new species of Eucyclops Claus (Copepoda: Cyclopoida) from the Chihuahuan Desert with a redescription of E. pseudoensifer Dussart

FIGURE 10. Eucyclops chihuahuensis sp. nov., adult female holotype from Presa Chihuahua, northern Mexico. A) leg 1; B) leg 2; C) leg 2; D) leg 4; E) coxal plate of leg 1; F) coxal plate of leg 1; G) coxal plate of leg 3; H) coxal plate of leg 4. Scale bars A–G=50 μm. All appendages shown in frontal view.

FIGURE 9 in Two new species of Eucyclops Claus (Copepoda: Cyclopoida) from the Chihuahuan Desert with a redescription of E. pseudoensifer Dussart

FIGURE 9. Eucyclops chihuahuensis sp. nov., adult female holotype from Presa Chihuahua, northern Mexico. A) habitus, dorsal view; B) antennule; C) antenna; D) caudal rami and anal somite, ventral view; E) genital double and fifth pedigerous somites, ventral view. Scale bars A=100 μm, B–D=50 μm.

FIGURE 4 in Two new species of Eucyclops Claus (Copepoda: Cyclopoida) from the Chihuahuan Desert with a redescription of E. pseudoensifer Dussart

FIGURE 4. Eucyclops cuatrocienegas sp. nov., adult male allotype from Cuatro Ciénegas, Coahuila, northern Mexico. A) habitus, dorsal view; B) fifth pedigerous and genital somites, ventral; C) right caudal ramus, dorsal view; D) inner terminal caudal seta showing ornamentation pattern. E) antennule. Scale bars A=100 μm, B–E=60 μm.