Epidermal browning of saguaro cacti (Carnegiea gigantea): is it new or related to direction?

Laboratory of Plant Morphogenesis, Manhattan College, The Bronx, NY 10471, U.S.A.
Environmental and Experimental Botany 01/1992; DOI: 10.1016/0098-8472(92)90048-7

ABSTRACT Browning of epidermal surfaces of saguaro cacti (Carnegiea gigantea) is associated with premature death of the species in the northern Sonoran Desert. Analyses of authentic historical photographs of mature saguaros from 1903 to 1987 demonstrated a significant (1) loss of spines, (2) decrease in apparently healthy crests, and (3) increased trough barking over the period. All three of these changes occurred to saguaros of over 115 years of age at a projected rate of 4–5% per decade. Analyses of epidermal characteristics of saguaros at the Saguaro National Monument were performed to determine if epidermal browning was related to compass direction. Results show that both scaling and barking of crests and troughs and loss of spines, all symptoms of epidermal browning, were 10 times higher on southern exposures (between 140 and 220°) compared with northern exposures (between 320 and 40°). The two troughs of a crest were evaluated separately. The results demonstrated that injury to one trough of a crest could be as much as four times greater than that of the second trough.

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    ABSTRACT: Question: We know of no study that has linked volcanic eruptions occurring anywhere worldwide and the local population cycles of any species. The keystone saguaro cactus (Carnegiea gigantea) establishes in cohorts. We test whether there is a statistical relationship between Carnegiea gigantea establishment and volcanic eruptions.Location: Northern Sonoran Desert, Arizona, USA.Methods: We use both a region-wide dataset made up of 30 populations, and a dataset from a marginal site. We incorporate data for over 750 individuals over an area of more than 50 000 km2. We created a 111-year time series of population peaks and troughs and correlated this over the 111-year record with the annual Weighted Historical Dust Veil Index (WHDVI). A t-test compared establishment patterns with the WHDVI.Results: We found a significant relationship between volcanism and C. gigantea regeneration at both the marginal site, and in the region-wide dataset.Conclusions: We suggest that while different populations are influenced by temporary global temperature ameliorations to different extents, our results show that populations do derive significant benefits from volcanic eruptions that promote their regeneration over large portions of their range, as is also exhibited locally at our marginal site, where populations are most susceptible to the inhospitable conditions that are witnessed at the edge of their range. This paper draws a link between the population fluctuations and regeneration of a species locally with geologic events from distant parts of the earth.
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    ABSTRACT: 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 1993–1994 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 1993–1994 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 1993–1994. In this manner, stem scale and bark injuries on south-facing surfaces were usually associated with the death of saguaros. The annual mortality rate of 2.3% appears high considering that this species may live for more than 200 years.Key words: saguaros, Carnegiea gigantea, Cactaceae, stem areas with scale and bark injuries, mortality rates.
    Canadian Journal of Botany 02/2011; 83(3):311-319. · 1.40 Impact Factor
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    ABSTRACT: Evans, L. S. (Laboratory of Plant Morphogenesis, Biological Sciences Research Laboratories, Manhattan College, the Bronx, NY 10471). Stem surface injuries of Neobuxbaumia tetetzo and Neobuxbaumia mezcalaensis of the Tehuacan Valley of central Mexico. J. Torrey Bot. Soc. 132: 33–37. 2005.—Identical scale and bark stem surface injuries are present on surfaces of fourteen species of long-lived columnar cacti in both North and South America. The purpose of this research was to determine the amounts of injuries on south-, east-, north-, and west-facing stem trough surfaces for two species of columnar cacti, Neobuxbaumia tetetzo and N. mezcalaensis, from the Tehuacan Valley (18° N latitude) of central Mexico. Stem surface injury levels on south (equatorial)-facing surfaces were twice that of north (polar)-facing stem surfaces for both cactus species. Calculations indicate that twice as much total annual direct sunlight occurs to south-facing cactus surfaces than on north-facing surfaces at 18° N latitude. In general, surface injury levels for east-facing and west-facing plant surfaces were usually intermediate between the high levels of injury for south-facing surfaces and the low levels of injury for north-facing surfaces. It should be noted that published results from columnar cacti growing at 32 °N latitude have about four times more stem surface injuries and four times more direct sunlight exposure on equatorial-facing surfaces than on polar surfaces. So, for columnar cacti at 18° and 32° latitude, the ratios of injuires were coincident with ratios of sunlight on equatorial and polar surfaces. Overall, the results of these studies are consistent with the hypothesis that sunlight, possibly UV-B, cause injuries to stems of long-lived, columnar cacti.
    Journal of the Torrey Botanical Society 01/2009; · 0.75 Impact Factor