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The large land area occupied by arid lands, roughly 36% to 40% globally, underscores the importance for understanding how these ecosystems function in the global carbon cycle. Few studies have directly examined soil organic carbon (SOC) dynamics and the effect of vegetation on SOC and microbial community structure in arid ecosystems. The objective of this study was to determine the effect of vegetation type on SOC dynamics in an arid, hyperthermic Sonoran Desert ecosystem. We specifically examined the influence of Prosopis velutina (mesquite), Larrea tridentata (creosote), and a combination of Bouteloua barbata, Bouteloua aristidoides, Aristida adscensionis, and Cynodon dactylon (mixed grass) vegetation types on...
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This data set represent the digital range map of Creosote Bush (Larrea tridentata) in western North America. Data from multiple sources, including existing digitized maps, tabular data, personal communication, and figures from other publications, were synthesized to create a single digital distribution. The distribution was peer reviewed and iteratively revised based on personal observations of regional authorities.
* 1 A classic biogeographic pattern is the alignment of diploid, tetraploid and hexaploid races of creosote bush (Larrea tridentata) across the Chihuahuan, Sonoran and Mohave Deserts of western North America. We used statistically robust differences in guard cell size of modern plants and fossil leaves from packrat middens to map current and past distributions of these ploidy races since the Last Glacial Maximum (LGM). * 2 Glacial/early Holocene (26?10 14C kyr bp or thousands of radiocarbon years before present) populations included diploids along the lower Rio Grande of west Texas, 650 km removed from sympatric diploids and tetraploids in the lower Colorado River Basin of south-eastern California/south-western...
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Larrea tridentata is a xerophytic evergreen shrub, dominant in the arid regions of the southwestern United States. We examined relationships between gasexchange characteristics, plant and soil water relations, and growth responses of large versus small shrubs of L. tridentata over the course of a summer growing season in the Chihuahuan Desert of southern New Mexico, USA. The soil wetting front did not reach 0.6 m, and soils at depths of 0.6 and 0.9 m remained dry throughout the summer, suggesting that L. tridentata extracts water largely from soil near the surface. Surface soil layers (max) occurred in early summer (21.3 � mol m-2 s-1), when pre-dawn xylem water potential (XWP) reached ca. -1 MPa. Although both...
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1. Windblown dust, an environmental problem in many disturbed arid lands, has the potential to affect the physiological performance of desert shrubs. Physiological parameters of gas exchange for three species (Larrea tridentata, Hymenoclea salsola and Atriplex canescens) were measured at a Mojave Desert site, at which both undisturbed and heavily dusted individual shrubs occurred. 2. Maximum rates of net photosynthesis (A) of dusted organs were reduced to 21% of those of control plants in resinous leaflets of Larrea, to 44% in resinous leaves and photosynthetic stems of Hymenoclea, and to 58% in non-resinous C4 leaves of Atriplex, which have vesiculated trichomes. Dusted plants of all three species showed reduced...
Geostatistical analyses show that the distribution of soil N, P and K is strongly associated with the presence of shrubs in desert habitats. Shrubs concentrate the biogeochemical cycle of these elements in ?islands of fertility? that are localized beneath their canopies, while adjacent barren, intershrub spaces are comparatively devoid of biotic activity. Both physical and biological processes are involved in the formation of shrub islands. Losses of semiarid grassland in favor of invading shrubs initiate these changes in the distribution of soil nutrients, which may promote the further invasion and persistence of shrubs and cause potential feedbacks between desertification and the Earth's climate system. Published...
Plant community structure in the southwestern United States co-varies with soil surface characteristics due to their role in controlling water availability. At the University of Arizona Desert Laboratory on Tumamoc Hill, we evaluated winter and summer season dynamics of photosynthesis in a dominant shrub species, Larrea tridentata (creosotebush), across soils with contrasting development of surface and sub-surface horizons. We measured pre-dawn water potential (?pd), stomatal conductance (gs), leaf nitrogen content (%N), and determined stable carbon isotope discrimination (?). There were no differences in these parameters throughout the winter, although ? was higher and %N was lower on the clay than sandy soil early...
The Chihuahuan desert of New Mexico, USA, has changed in historical times from semiarid grassland to desert shrublands dominated by Larrea tridentata and Prosopis glandulosa. Similar displacement of perennial grasslands by shrubs typifies desertification in many regions. Such structural vegetation change could alter average values of net primary productivity, as well as spatial and temporal patterns of production. We investigated patterns of aboveground plant biomass and net primary production in five ecosystem types of the Jornada Basin Long-Term Ecological Research (LTER) site. Comparisons of shrub-dominated desertified systems and remnant grass-dominated systems allowed us to test the prediction that shrublands...
Recent drought across the desert Southwest US may strongly affect the physiological functioning of evergreen desert species that maintain leaves through these dry periods. In July 2002 we compared the ecophysiological performance of the open-canopied, small-leaved creosotebush (Larrea tridentata) to the dense-canopied, more broad-leaved jojoba (Simmondsia chinensis) growing on a ridge-top, east- and west-facing slopes to assess how differences in leaf habit and exposure affect these species' ability to withstand severe drought. Standardized precipitation index (SPI) from 100 years precipitation data showed July 2002 rainfall was normal, but the 12-month period ending July 2002 was of extreme aridity (SPI = ?2.71)....
A field experiment using 2 patterns of irrigation and 1 level of nitrogen fertilizer (10 g-N m-2) was conducted in order to discern water and nitrogen interactions that may control production of creosotebush, (Larrea tridentata (D.C.) Cov. The 2 patterns of irrigation simulated precipitation from small, frequent events (6 mm water added weekly) or large, infrequent events (25 mm water added monthly). Understanding the factors controlling the production of this rangeland shrub may aid in the development of strategies for its management. Vegetative growth occurred mostly during March-May (spring) and August-October (summer-fall). Fruit production occurred mainly in the spring and root growth occurred mainly in the...
Horizontal and vertical zones of influence for root systems of four Mojave Desert shrubs were characterized using 32P as a nutrient tracer. Larrea tridentata's horizontal zone of influence was sparse near the plant's stem base, with a maximum probability of accessing 32P (Pmax) of 41%. However, its horizontal zone of influence extended beyond 5 m, and the distance from the stem base at which the probability of accessing 32P was half Pmax (L503 m) was significantly greater than the other three shrubs. Ambrosia dumosa's zone of influence was dense near the plant's stem base (Pmax78%), but was rare at distances >2 m (L501 m). Zones of influence for Lycium andersonii and Lycium pallidum were intermediate between those...
Irrigation and rain-out shelters were used to simulate precipitation patterns of wet and dry years in the northern Chihuahuan Desert. Irrigation provided approximately double the long-term average monthly precipitation. Rain was excluded during the wet season, July-October, to simulate a dry year. N net mineralization in laboratory incubations was undectable at calculated water potentials less than -1 MPa. Witb increasing moisture, mineralization gradually rose to the highest observed rates near field capacity. There was no mineralization maximum at moisture contents below field capacity. Irrigation significantly increased the water potential and rainfall exclusion reduced water potentials to less than-8 MPa. The...
Changes in the timing, frequency, and magnitude of precipitation events are projected for semiarid ecosystems worldwide. The ecological consequences associated with these precipitation changes will be better understood if the hydrological triggers of vegetation response can be better identified. Previous research has suggested that soil moisture, likely from large monsoon rainstorms, plays a critical role in triggering the phenological response of semiarid shrublands. Here we propose that the recent emergence of time-lapse repeat digital photography (pheno-cams) can play a role in further explaining the hydrological triggers of phenological response in semiarid shrublands. This study is focused on a creosotebush-dominated...
    map background search result map search result map Surface Dust Impacts on Gas Exchange in Mojave Desert Shrubs Effects of plant size and water relations on gas exchange and growth of the desert shrub Larrea tridentata Range Map of Creosote Bush (Larrea tridentata) Effects of plant size and water relations on gas exchange and growth of the desert shrub Larrea tridentata Surface Dust Impacts on Gas Exchange in Mojave Desert Shrubs Range Map of Creosote Bush (Larrea tridentata)