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Taly Dawn Drezner - One of the best experts on this subject based on the ideXlab platform.
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variations in saguaro cactus Carnegiea gigantea spine length in wet and dry portions of their range
Madroño, 2017Co-Authors: Taly Dawn DreznerAbstract:I sampled spine length in the keystone Carnegiea gigantea (Engelm.) Britton & Rose in two northern Sonoran Desert populations where this species is ultimately limited by cold temperatures. I compared spine length (1) between two sites, (2) on north versus south facing sides of plants, (3) by level of shading, (4) by proximity to other potential conspecific competitors, and (5) by presence near sources of surface runoff from which all their water is obtained. Spine length increases, providing thermal protection and reducing photosynthesis, where temperature is more extreme (winter and summer) and where conditions are more xeric. The difference in spine length by direction on plant was much smaller at the more extreme site. Clumped plants that necessarily had increased competition for water but also greater shading were split; at the more extreme site, greater spine shading occurred where water competition was fiercest, while at the less extreme site, greater shading occurred in association with sunlight rather than water.
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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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regional branching relationships in Carnegiea gigantea a keystone cactus
Western North American Naturalist, 2014Co-Authors: Taly Dawn DreznerAbstract:Abstract. The large columnar cactus Carnegiea gigantea branches to increase reproductive output. The branches of this keystone species also provide shelter to a large portion of the Sonoran Desert's fauna. In this study, branch length was used to reconstruct branch establishment at 2 populations to determine branching patterns over time and the relationship across populations. Branches showed high establishment but relatively low survival. Either more branches establish than eventually survive or growth is slow when branches are smaller, thereby biasing the distribution of lengths due to the differences in growth rate. Also, the distribution of branch lengths (i.e., branch generation over time) reflects a cohort pattern, indicating that there are favorable and poor years for branch production. Further, a significant relationship in peaks and troughs is detected between the 2 very different populations, suggesting a regional influence over branching that extends beyond a population or local area.
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The keystone saguaro (Carnegiea gigantea, Cactaceae): a review of its ecology, associations, reproduction, limits, and demographics
Plant Ecology, 2014Co-Authors: Taly Dawn DreznerAbstract:This paper reviews the basics of a Sonoran Desert keystone cactus species, including the ecology of its establishment and high mortality, its association with nurse plants to provide ameliorated conditions for survival, and variability in longevity and reproduction over its range such as delayed reproduction in hotter and more arid populations where this delay is met with longer lifespans. The production of flowers, branches, and spines from areoles is reviewed, as well as current methods for estimating individual age despite great variability in growth rates, most notably linked to summer rainfall. Possible implications of anthropogenic influences that impact populations as well as global climate change are discussed as are implications for potential range shifts in the future. This paper also provides a table listing of over 100 birds, mammals, insects, reptiles, and other animal species that use Carnegiea and highlighting its keystone status.
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relationships between epidermal browning girdling damage and bird cavities in a military restricted database of 12 000 plants of the keystone Carnegiea gigantea in the northern sonoran desert
Madroño; a West American journal of botany, 2014Co-Authors: Shelley Danzer, Taly Dawn DreznerAbstract:Abstract An exceptional dataset for over 12,000 Carnegiea gigantea collected by the Arizona Department of Game and Fish over two field seasons on a restricted military reservation was released to the authors for analysis, including a variety of variables for which little empirical evidence exists. Data on epidermal browning, physical damage due to fire, lightning, gunshot or topping, rodent girdling, bird cavities and other variables were assessed using primarily chi-square analysis. The main findings of this study include: (1) Plants with high amounts of epidermal browning were rather evenly distributed across height classes, although the very smallest plants (0–0.9 m) had substantially less epidermal browning. (2) Although past work has shown that epidermal browning is surely a function of solar radiation receipt, other variables (bird cavities, girdling, damage, branching) are statistically linked with browning, raising the possibility that other biotic and abiotic factors may hasten browning. (3) Bird...
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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a 26 year stable isotope record of humidity and el nino enhanced precipitation in the spines of saguaro cactus Carnegiea gigantea
Palaeogeography Palaeoclimatology Palaeoecology, 2010Co-Authors: Nathan B English, David L Dettman, David G WilliamsAbstract:article i nfo Seasonal and annual variations of rainfall and humidity are recorded in the carbon and oxygen stable isotope ratios of sequentially grown spines found on the columnar cactus, Carnegiea gigantea. A 26-year long composite δ 18 O and δ 13 C isotope record from the spines of five saguaro cacti was created using bomb radiocarbon and semi-annual variations in δ 13 C. Once dating errors in the composite record are corrected, 18 O is negatively correlated (Pb0.001) with total annual precipitation (TAP) from November through October and positively correlated (Pb0.01) with mean annual nighttime vapor pressure deficit (VPD). Year-to-year decreases (N2‰) in the maximum annual spine δ 18 O are positively correlated (Pb0.01) with the Southern Oscillation Index (SOI). We attribute these decreases to enhanced winter rainfall associated with the El Nino phase of the El Nino-Southern Oscillation. Minimum annual δ 13 C is negatively correlated with TAP (Pb0.05) and mean nighttime VPD (Pb0.05). These results bolster proposed mechanistic models of isotopic variation in the spines of columnar cactus and demonstrate how isotopic spine series may be used as climate proxies in regions of the Americas where trees suitable for traditional or isotopic dendrochonology are absent. Published by Elsevier B.V.
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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.
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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rates of bark formation on surfaces of saguaro cacti Carnegiea gigantea 1 2
Journal of The Torrey Botanical Society, 2017Co-Authors: Mark Debonis, Lauren Barton, Lance S EvansAbstract:Abstract Twenty-one species of tall, long-lived columnar cactus species show extensive bark coverage (epidermal browning) in the Americas. Each species shows more bark coverage on equatorial-facing surfaces than on polar-facing surfaces. In addition, controlled experiments with supplemental UV-B irradiation show the initial stages of bark coverage. These two facts suggest that UV-B irradiation is the cause of sunlight-induced bark coverage. This sunlight-induced bark leads to premature morbidity and mortality. Saguaro cactus (Carnegiea gigantea (Engelm.) Britton & Rose) of southern Arizona is the most researched cactus species with regard to this bark coverage. The current effort focused on bark coverage rates on 12 cactus surfaces at 1.7 m height above ground by comparing logistic curves of relative bark coverage among stem surfaces. Logistic curves have been used to document progress of many diseases in humans. In this study, logistic curves were best fit to data with least squares analysis in all cases...
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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...
Nathan B English - 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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a 26 year stable isotope record of humidity and el nino enhanced precipitation in the spines of saguaro cactus Carnegiea gigantea
Palaeogeography Palaeoclimatology Palaeoecology, 2010Co-Authors: Nathan B English, David L Dettman, David G WilliamsAbstract:article i nfo Seasonal and annual variations of rainfall and humidity are recorded in the carbon and oxygen stable isotope ratios of sequentially grown spines found on the columnar cactus, Carnegiea gigantea. A 26-year long composite δ 18 O and δ 13 C isotope record from the spines of five saguaro cacti was created using bomb radiocarbon and semi-annual variations in δ 13 C. Once dating errors in the composite record are corrected, 18 O is negatively correlated (Pb0.001) with total annual precipitation (TAP) from November through October and positively correlated (Pb0.01) with mean annual nighttime vapor pressure deficit (VPD). Year-to-year decreases (N2‰) in the maximum annual spine δ 18 O are positively correlated (Pb0.01) with the Southern Oscillation Index (SOI). We attribute these decreases to enhanced winter rainfall associated with the El Nino phase of the El Nino-Southern Oscillation. Minimum annual δ 13 C is negatively correlated with TAP (Pb0.05) and mean nighttime VPD (Pb0.05). These results bolster proposed mechanistic models of isotopic variation in the spines of columnar cactus and demonstrate how isotopic spine series may be used as climate proxies in regions of the Americas where trees suitable for traditional or isotopic dendrochonology are absent. Published by Elsevier B.V.
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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.
Susana Rodriguezburitica - One of the best experts on this subject based on the ideXlab platform.
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local temporal trajectories explain population level responses to climate change in saguaro Carnegiea gigantea
Ecosphere, 2019Co-Authors: Daniel E Winkler, Susana Rodriguezburitica, Robert H Webb, Lawrence D VenableAbstract:NSFNational Science Foundation (NSF) [DEB 0817121]; U.S. Geological SurveyUnited States Geological Survey
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population dynamics of sonoran desert saguaro cactus Carnegiea gigantea at the desert laboratory tucson arizona
Ecology, 2013Co-Authors: Susana Rodriguezburitica, Raymond M Turner, Elizabeth A Pierson, Helen Raichle, Trevor Birt, Robert H Webb, Lawrence D VenableAbstract:The saguaro cactus (Carnegiea gigantea) is one of the most iconic perennials in the Sonoran Desert. The ecological importance of this species has motivated studies that explored its physiological adaptations to deserts, factors controlling its recruitment and distribution, and changes in its population density and extent over time. The population of saguaros on Tumamoc Hill (Tucson, Arizona) is one of the best studied. Saguaros on and nearby Tumamoc Hill were mapped in 1908, and in 1964 R. M. Turner and J. R. Hastings established four 250-m wide plots within the original census area. Plots were established on the north-, south-, east-, and west-facing slopes of Tumamoc Hill, and each plot extends from the top to the base of the hill. Plots were resurveyed in 1970, 1987, 1993, and between 2010 and 2012. In this Data Paper, we present all information associated with this monitoring program, which includes digital versions of Spalding's original 1908 saguaro map as well as information regarding individual saguaros located in each of the four plots. Collected data include plant height, number of branches, and plant condition, as well as plant location. Starting in 1993, we also noted the identity and condition of plant species growing in close proximity to each saguaro. The archived data set described here contains information pertaining to >5800 saguaros. Past analyses of these data include reconstructions of regeneration patterns from observed age structures and the determination of the average height-specific growth rates for plants on each slope. The findings from these studies have broadened our understanding of the relationship between saguaro regeneration patterns and climate. These data have also provided pivotal information regarding regional trends of saguaro populations throughout the Sonoran Desert. As a group, the Tumamoc Hill censuses constitute one of the longest spatially explicit monitoring efforts for a single species in the world. They provide an observational baseline for future comparisons relating individual growth and population demographics to rising CO2 levels, climate change, vegetation change, or changes in other biotic or abiotic factors.