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Taly Dawn Drezner - One of the best experts on this subject based on the ideXlab platform.
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test of the accuracy of an age height model for Saguaro carnegiea gigantea
Southwestern Naturalist, 2014Co-Authors: Taly Dawn Drezner, Raymond M TurnerAbstract:A test of a general growth-model to estimate the age of Carnegiea gigantea, a keystone species of the Sonoran Desert, was conducted. Results suggest that standard errors are low (<2 years) and the model is robust for estimating age of establishment of the long-lived Saguaro cactus.
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variation in age and height of onset of reproduction in the Saguaro cactus carnegiea gigantea in the sonoran desert
Plant Ecology, 2007Co-Authors: Taly Dawn DreznerAbstract:The objective of this study is to determine the height and age at which reproduction begins (i.e., production of flowers and fruits; the transition to adulthood) in the giant Saguaro cactus (Carnegiea gigantea) in four geographically and environmentally distinct populations, and to relate observed variability to environmental differences. The onset of reproduction has been estimated at a height of 2.2 m in near optimal conditions. This value has been widely accepted and applied to populations in less optimal conditions, although variations under less ideal conditions have not been investigated. In addition, previous research has demonstrated that Carnegiea growth rates are highly variable over their range. Thus, even if 2.2 m is a consistent transition height to adulthood over their range, the age of individuals in different populations would be different. I investigate the age and height at which this transition occurs. The author sampled the heights of the shortest reproductive individuals and the tallest non-reproductive individuals to estimate the mean height of the onset of flowering in each of four locales in the northern Sonoran Desert. Using a previously published age-height-growth model, the mean age of the start of reproduction was also computed for the four sites. ANOVA and t-tests were used to compare the average transition to adulthood across sites by both age and height. Statistical results are robust and significant variations in the onset of reproduction are observed by both age and height across the four sites. Saguaro National Park and Organ Pipe Cactus National Monument individuals are transitioning to adulthood, on average, at younger ages and shorter heights than the other two locales. At the arid and marginal Kofa site, individuals that established during the regeneration peak of the late 1800s-early 1900s are only now becoming reproductive (individuals that established around 1899), while at Saguaro National Park, on average, individuals that established in the 1950s are already transitioning to adulthood. These results have implications for regeneration, particularly in marginal locales where regeneration is already limited.
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plant facilitation in extreme environments the non random distribution of Saguaro cacti carnegiea gigantea under their nurse associates and the relationship to nurse architecture
Journal of Arid Environments, 2006Co-Authors: Taly Dawn DreznerAbstract:Abstract This study samples 247 Saguaros ( Carnegiea gigantea ) and their nurses in 30 populations in the northern Sonoran Desert to determine whether Saguaros are randomly distributed beneath their nurses’ canopies. Saguaro–nurse association patterns are compared across three nurse groups distinguished by canopy architecture characteristics (leguminous trees, small dense Ambrosia spp. shrubs, and the larger, open-canopied shrub Larrea tridentata ). For all three nurse types, Saguaros are significantly clustered near the center of their nurse's base. Clustering varies with nurse architecture, as Saguaros are most tightly clumped under the most open-canopied species ( L. tridentata ), as more than 80% of Saguaros were under the innermost 10% of L. tridentata 's subcanopy area. Saguaros showed the least basal clustering about tree nurses, though not significantly less than Ambrosia spp. nurses. More Saguaros establish under Ambrosia relative to its cover in sampled populations, while Saguaros were underrepresented under L. tridentata . All analyses suggest that L. tridentata is an inferior nurse for Saguaros. Different canopy architecture influences the extent of ground available to a nursed species to benefit from, for establishment and survival. While herbivory, rodents or other factors may play a role in these patterns, ultimately microclimate differences are the most likely factor shaping cacti–nurse associations in the harsh desert environment.
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regeneration of carnegiea gigantea cactaceae since 1850 in three populations in the northern sonoran desert
Acta Oecologica-international Journal of Ecology, 2006Co-Authors: Taly Dawn DreznerAbstract:Saguaro cacti (Carnegiea gigantea) are long-lived and exhibit great variability in growth that makes age estimation problematic. A few single-site studies have focused on those locales where long-term data (e.g. 85 years) are available. Using a newly developed technique, 733 Saguaros were sampled in three locales (Silverbell, Harcuvar, Kofa) across Arizona and their age structure reconstructed for the last 150 years based on a mathematical model of the heights of individuals. This is the first study to compare regeneration at multiple locations across the species' range. Regression analysis for each site (years and frequency of individuals established during that year) was run and residuals extracted to determine peaks and troughs in regeneration over time. Correlation was run on the residuals between sites, and chi-square analysis was employed to compare frequency of good and bad regeneration years between Kofa and Silverbell. Peaks and troughs represent regeneration as well as survivorship and mortality. Several large cohorts established at Kofa and Harcuvar since 1850, while at Silverbell well over 80% of sampled Saguaros established after the late 1930s. This more recent recruitment at Silverbell may be related to the major freezing event of 1937 whose impact was likely greater at the cooler Silverbell site. Despite the widely different population structures at Silverbell and Kofa, recruitment trends in both populations were statistically linked as both locales often benefited from the same favorable periods for regeneration (P < 0.001). The Harcuvar population shares some common peaks and troughs in regeneration over time with Kofa and Silverbell, but its relationship to them is not statistically significant. Some trends overlap in some locales, such as the favorable regeneration period in the late 1800s and early 1900s, particularly at Silverbell and Kofa as well as at other known sites. However, each population has its own signature. Silverbell is a youthful population likely shaped by severe freezing events, while Kofa has many individuals representing regeneration at several different periods. Regeneration, mortality and subsequent population structure is shaped by both regional-scale influences as well as more localized conditions over the long and short terms.
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Saguaro carnegiea gigantea densities and reproduction over the northern sonoran desert
Physical Geography, 2006Co-Authors: Taly Dawn DreznerAbstract:Casual observations suggest that Saguaro populations are densest in southeastern Arizona, although data have not been collected and no study has been done to address this topic. In addition, the topic of reproductive density has similarly never been addressed. Saguaro reproductive output is directly related to the number of adult individuals and the number of branches in the area. Thirty Saguaro populations over their U.S. range were sampled to consider two variables: population density and reproductive stem density. Stepwise regression using climate and vegetation (e.g., availability of nurse plants) to predict density yielded tree + Ambrosia cover and maximum July precipitation. Nurse cover, however, is also influenced by summer rain. The partial correlation results suggest that high Saguaro densities are linked with high quality nurse cover (i.e., not Larrea tridentata) in addition to summer rainfall. Total cover and mean annual precipitation are the best predictors of reproductive stem density. Mean a...
Rice Jeff - One of the best experts on this subject based on the ideXlab platform.
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Collared Peccary bark (100424)
Western Soundscape Archive University of Utah, 2010Co-Authors: Rice JeffAbstract:AnimaliaCraniataMammaliaArtiodactylaTayassuidaePecariCompressed from .wav format into .mp4 delivery formatAudio tracks of animal soundsRecorded in a residential area on the outskirts of Tucson near Saguaro National Park east; Local time: approximately 8 P
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Coyotes near Tucson (100314) b
Western Soundscape Archive University of Utah, 2010Co-Authors: Rice JeffAbstract:AnimaliaCraniataMammaliaCarnivoraCanidaeCanisCompressed from .wav format into .mp4 delivery formatCoyote vocalizationsCoyotes on the outskirts of Tucson near Saguaro National Park east; recorded at approximately 1 A
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Collared peccary herd (100424)
Western Soundscape Archive University of Utah, 2010Co-Authors: Rice JeffAbstract:AnimaliaCraniataMammaliaArtiodactylaTayassuidaePecariCompressed from .wav format into .mp4 delivery formatAudio tracks of animal soundsRecorded in a residential area on the outskirts of Tucson near Saguaro National Park east; Local time: approximately 8 P
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Yavapai Leopard Frog (100314) 2
Western Soundscape Archive University of Utah, 2010Co-Authors: Rice JeffAbstract:AnimaliaCraniataAmphibiaAnuraRanidaeRanaBreeding Season: September-AprilCompressed from .wav format into .mp4 delivery formatAudio tracks of animal soundsRecorded between midnight and 4 AM at a small man-made pond in a residential area on the outskirts of Tucson near Saguaro National Park eas
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Yavapai Leopard Frog (100314) 5
Western Soundscape Archive University of Utah, 2010Co-Authors: Rice JeffAbstract:AnimaliaCraniataAmphibiaAnuraRanidaeRanaBreeding Season: September-AprilCompressed from .wav format into .mp4 delivery formatAudio tracks of animal soundsRecorded between midnight and 4 AM at a small man-made pond in a residential area on the outskirts of Tucson near Saguaro National Park eas
Lance S Evans - One of the best experts on this subject based on the ideXlab platform.
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algorithms predict morbidity and mortality of Saguaro cacti carnegiea gigantea from sunlight exposures
Flora, 2021Co-Authors: Lance S EvansAbstract:Abstract Bark coverages on stem surfaces lead to premature death of Saguaro cacti (Carnegiea gigantea). Bark coverages have occurred on surfaces of more than 50 species of tall, long-lived cacti throughout the Americas. This study analyzed data of bark coverages on 12 surfaces of C. gigantea. Among 1,149 Saguaro cacti, from four sampling periods over 23 years, data of four independent algorithm programs were used to predict bark coverages and cactus death. On Saguaros, bark coverage originates on south-facing surfaces and progresses to north-facing surfaces, prior to cactus death. For this population, bark coverages increased over time and 45% of all cacti were dead by the end of the 23-year study period. Validate Model and WEKA 3.8 predicted bark coverages with over 96% accuracy. Random Forest predicted cactus death with 99.6% accuracy and kNN predicted cactus death with 100% accuracy. Since trough surfaces occur after crest surfaces, trough surfaces were better predictors of bark coverages and cactus death. Cactus death was best predicted (above 99%) with north-right troughs with west-facing surfaces. Taken together, the four machine programs gave complimentary results and predicted (above 99%) both increased bark coverages from south-facing surfaces to north-facing surfaces over time and death of individual cacti over an eight-year period when north-facing right troughs had more than 80% bark coverages.
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machine learning algorithms predict bark coverages on Saguaro cacti carnegiea gigantea
Flora, 2020Co-Authors: Lance S Evans, Alexander Shackley, Olivia PrintyAbstract:Abstract Bark coverages lead to the premature death of Saguaro cacti (Carnegiea gigantea). Bark coverages on surfaces of more than 20 species of tall, long-lived cacti occur throughout the Americas. This study analyzed data of bark coverages on twelve surfaces on 1149 Saguaro cacti from four sampling periods over a period of 23 years. Bark coverage starts on equator-facing surfaces and progresses to polar-facing surfaces. For this population, 45 % of all cacti were dead by the end of the 23-year period of study. In order to understand how bark coverages are related to cactus death, four machine learning programs were used to analyze the data obtained. Decision trees predicted rates of bark coverages and death with time as a variable with probabilities of 90 % and 99 %, respectively. Trough surfaces were better predictors of bark coverage and cactus death than crest surfaces. Left troughs of both polar- and west-facing surfaces were the best predictors of bark coverage and cactus death with probabilities above 99 %. The four machine learning programs gave complimentary results to present a unified view to predict future bark coverages over time and predict eventual cactus death with more than 99 % accuracy.
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predicting morbidity and mortality for a Saguaro cactus carnegiea gigantea population1
Journal of The Torrey Botanical Society, 2013Co-Authors: Lance S Evans, Peter Boothe, Andrew BaezAbstract:Scale and bark injuries (a condition called epidermal browning) have been shown to occur on stem surfaces of 21 species of tall, long-lived cactus species throughout the Americas. The amounts of surface injuries are highly correlated with amounts of sunlight exposures. Epidermal browning causes cactus morbidity and mortality of Saguaro cacti. For this study, rates of morbidity and mortality of Saguaro cacti (Carnegiea gigantea (Engelm.) Britt and Rose) were determined for 1061 plants from 50 desert field plots. From 2002 to 2010, 16.5% of all Saguaros died (increased mortality). During the same period, the percentage of cacti with few epidermal injuries decreased from 25 to 9%, with a 16% increase in initial morbidity. Over this same period, about 10% of the population had a rapid increase of epidermal browning (rapid morbidity). Thus, marked increases in morbidity and mortality occurred over the eight-year period. WEKA, a standard machine-learning program, was used to determine the characteristics of Saguaros that predispose them to (1) die, (2) initiate morbidity (start of epidermal browning symptoms) and (3) initiate rapid morbidity (a rapid increase in epidermal browning). Decision trees were created using the C4.5 algorithm, a top-down method that repeatedly chooses the question that produces a maximal information gain. Amounts of epidermal browning on north-facing troughs alone predicted cactus mortality with 89.1% accuracy. Initial morbidity was predicted with 80.2% accuracy with data of south-facing troughs and crests only. Rapid morbidity (less than 20% epidermal browning in 2002 and more than 50% by 2010) was predicted with a very large tree with 79.6% accuracy. For example, rapid morbidity is predicted by more than 3.1% epidermal browning on left troughs on south-facing surfaces in 2002 with 80% accuracy. Moreover, rapid morbidity was also predicted if east-facing crests had more than 3.9% epidermal browning in 2002. Overall, decision tree analysis was very effective at predicting changes in mortality and morbidity for the population of 1061 Saguaros from 2002 to 2010. Data from trough surfaces were more effective than data from crests for predicting mortality and morbidity.
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changes in scale and bark stem surface injuries and mortality rates of a Saguaro cacti carnegiea gigantea cactaceae population in tucson mountain park
Botany, 2005Co-Authors: Lance S Evans, April Jan B Young, Sr Joan HarnettAbstract:Rates that stem surfaces of Saguaro cacti (Carnegiea gigantea (Engelm.) Britt & Rose) accumulate scale and bark injuries and the mortality rates of cacti were determined on a population of 1149 Saguaro cacti in 50 field plots over the 9-year period of study (from 19931994 until 2002). Twenty-three percent of the Saguaro population had few surface injuries throughout the 9-year period while 27% showed a marked increase in stem area with scale and bark injuries. Thirty percent of all cacti had more than 80% stem areas with combined scale and bark injuries on south-facing stem surfaces throughout the study period. Finally, 20.3% of the Saguaro population died over the 9-year period, a rate of 2.3% per year. Thirty-three percent of all cacti that died by 2002 exhibited few surface injuries in 19931994 while 54% of the cacti that died over the period had more than 98% stem areas with combined scale and bark on south-facing stem surfaces in 19931994. In this manner, stem scale and bark injuries on south-faci...
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changes in surface injuries and mortality rates of Saguaro carnegiea gigantea cacti over a twelve year period
Journal of The Torrey Botanical Society, 2003Co-Authors: Lance S Evans, Michelle Zugermayr, April Jan B YoungAbstract:injuries and the mortality rate of a population of 253 Saguaro cacti were determined over a twelve-year period of study. Seventeen percent of the Saguaro population had few surface injuries throughout the period. Thirty percent of the population showed a marked increase (more than half of the cacti in this group showed a mean increase in barking of 80%) in scaling and barking injuries over the 12-year period. Twenty-six percent of all cacti had more than 90% scaling and barking on stem surfaces throughout the period. Rates of scaling and barking injuries (morbidity) are high considering the long life span of Saguaros. Finally, 27.3% of the Saguaro population died over the twelve-year period. Twenty-five percent of the cacti that died over the period exhibited few surface injuries in 1990 while 65% of the cacti that died over the period had 98% scaling and barking on stem crests in 1990. A mortality rate of 27% over 12 years (2.3% annually) is very high considering these cacti may live for long time periods.
David G Williams - One of the best experts on this subject based on the ideXlab platform.
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seasonal photosynthetic gas exchange and water use efficiency in a constitutive cam plant the giant Saguaro cactus carnegiea gigantea
Oecologia, 2011Co-Authors: Dustin R Bronson, Nathan B English, David L Dettman, David G WilliamsAbstract:Crassulacean acid metabolism (CAM) and the capacity to store large quantities of water are thought to confer high water use efficiency (WUE) and survival of succulent plants in warm desert environments. Yet the highly variable precipitation, temperature and humidity conditions in these environments likely have unique impacts on underlying processes regulating photosynthetic gas exchange and WUE, limiting our ability to predict growth and survival responses of desert CAM plants to climate change. We monitored net CO2 assimilation (Anet), stomatal conductance (gs), and transpiration (E) rates periodically over 2 years in a natural population of the giant columnar cactus Carnegiea gigantea (Saguaro) near Tucson, Arizona USA to investigate environmental and physiological controls over carbon gain and water loss in this ecologically important plant. We hypothesized that seasonal changes in daily integrated water use efficiency (WUEday) in this constitutive CAM species would be driven largely by stomatal regulation of nighttime transpiration and CO2 uptake responding to shifts in nighttime air temperature and humidity. The lowest WUEday occurred during time periods with extreme high and low air vapor pressure deficit (Da). The diurnal with the highest Da had low WUEday due to minimal net carbon gain across the 24 h period. Low WUEday was also observed under conditions of low Da; however, it was due to significant transpiration losses. Gas exchange measurements on potted Saguaro plants exposed to experimental changes in Da confirmed the relationship between Da and gs. Our results suggest that climatic changes involving shifts in air temperature and humidity will have large impacts on the water and carbon economy of the giant Saguaro and potentially other succulent CAM plants of warm desert environments.
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daily to decadal patterns of precipitation humidity and photosynthetic physiology recorded in the spines of the columnar cactus carnegiea gigantea
Journal of Geophysical Research, 2010Co-Authors: Nathan B English, David L Dettman, Darren R Sandquist, David G WilliamsAbstract:[1] Isotopic analyses of cactus spines grown serially from the apex of long-lived columnar cactuses may be useful for climatological and ecological studies if time series can be reliably determined from spines. To characterize the timescales over which spines may record this information, we measured spine growth in Saguaro cactus over days, months, and years with time-lapse photography, periodic marking, and postbomb radiocarbon dating and then analyzed isotopic variability over these same timescales and compared these measurements to local climate. We used daily increments of growth, visible as transverse bands of light and dark tissue in spines, as chronometers to develop diurnally resolved δ13C and δ18O records from three spines grown in series over a 70 day period. We also constructed a 22 year record of δ13C variations from spine tips arranged in chronological sequence along the side of a 4 m tall, single-stemmed Saguaro. We evaluated two mechanisms potentially responsible for daily, weekly, and annual variability in δ13C values of spines; both related to vapor pressure deficit (VPD). Our data suggest that stomatal conductance is unlikely to be the determinant of δ13C variation in spines. We suggest that either VPD-induced changes in the balance of nighttime- and daytime-assimilated CO2 or mesophyll-limited diffusion of CO2 at night are the most likely determinant of δ13C variation in spines. Intra-annual and interannual variability of δ18O in spine tissue appears to be controlled by the mass balance of 18O-depleted water taken up after rain events and evaporative enrichment of 18O in tissue water between rains. We were able to estimate the annual growth and areole generation rate of a Saguaro cactus from its 22 yearlong isotopic record because VPD, rainfall, and evaporation exhibit strong annual cycles in the Sonoran Desert and these variations are recorded in the oxygen and carbon isotope ratios of spines.
Vahab Hassani - One of the best experts on this subject based on the ideXlab platform.
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Hassani V.: Performance Analysis of Thermocline Energy Storage proposed for the 1MW Saguaro Solar Trough Plant
2015Co-Authors: Gregory J Kolb, Vahab HassaniAbstract:The 1 MW Saguaro solar parabolic trough power plant began operation in December 2005. The plant will initially operate without an energy storage system. However, recent studies predict a thermocline-type storage should be the most cost-effective storage concept for solar parabolic troughs power plants. If such a system can be successfully demonstrated at Saguaro, future trough plants will likely adopt this storage technology. A thermocline storage system for Saguaro has been proposed by Department of Energy (DOE) laboratories and the solar industry. In this paper, the time-dependent performance of the proposed storage system was evaluated with a new model of the plant based on the TRNSYS simulation system. Results indicate that the proposed system should work well at Saguaro. The paper describes the TRNSYS model and the engineering insights gleaned from annual performance simulations of the plant
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performance analysis of thermocline energy storage proposed for the 1 mw Saguaro solar trough plant
Solar Energy, 2006Co-Authors: Gregory J Kolb, Vahab HassaniAbstract:The 1 MW Saguaro solar parabolic trough power plant began operation in December 2005. The plant will initially operate without an energy storage system. However, recent studies predict a thermocline-type storage should be the most cost-effective storage concept for solar parabolic troughs power plants. If such a system can be successfully demonstrated at Saguaro, future trough plants will likely adopt this storage technology. A thermocline storage system for Saguaro has been proposed by Department of Energy (DOE) laboratories and the solar industry. In this paper, the time-dependent performance of the proposed storage system was evaluated with a new model of the plant based on the TRNSYS simulation system. Results indicate that the proposed system should work well at Saguaro. The paper describes the TRNSYS model and the engineering insights gleaned from annual performance simulations of the plant.
