Showing papers by "Thomas T. Veblen published in 1977"

Plant Succession in a Timberline Depressed by Vulcanism in South-Central Chile

Abstract: The vegetation of the Antillanca Valley in the Andes of southcentral Chile consists of high altitude fellfields, species-rich scrub grasslands, Nothofagus krummholz, deciduous N. pumilio forests, and mixed evergreen deciduous NVothofagus forests. Catastrophic vulcanism has depressed the timberlines an average of 100 to 300 m and greatly affected these vegetation types. Locally, timberline is determined under the influence of such disruptive factors as withthrow, unstable slopes, and avalanches. Succession is interpreted on the bases of species distributions in zones of environmental stress, population structures, and the observed responses of the dominant Nothofagus spp. to avalanche damage and burial by scoria deposition. This study thus documents the dynamic and transitory nature of the frequently-described vegetation zones of southcentral Chile.

Distribution and dominance of species in the understorey of a mixed evergreen-deciduous Nothofagus forest in south-central Chile.

Abstract: SUMMARY An area of mixed deciduous and evergreen Nothofagus forest at 1000-1050 m altitude near the timberline in south-central Chile was studied to determine the influence of the tree dominants on the distribution and dominance of plants in the understorey. The understorey dominant Chusquea cf. tenuiflora Phil., a bamboo, was found to be more frequent and taller under the evergreen Nothofagus betuloides. Nearly all other understorey species were more abundant and larger under the deciduous N. pumilio. The snow cover is less persistent under N. betuloides, resulting in a longer vegetative period under the evergreen trees. Chusquea cf. tenuiflora is well adapted to take advantage of earlier snow-melt by its capacity to spring into an erect position when released from the pressure of snow, and its vigorous growth suppresses the other understorey components. In the successional trend from mixed Nothofagus forest towards evergreen forest, C. cf. tenuiflora would be expected to increase in size and abundance, and to play an increasingly controlling role in the process of forest regeneration.

Native population decline in Totonicapán, Guatemala.

Abstract: The Spanish conquest of the New World resulted in a rapid and drastic reduction of the native population. This demographic collapse was caused by the battles of conquest, the severe disruption of native economies, and the devastating impact of Old World diseases on an immunologically virgin population. In the case of Totonicapan in the western highlands of Guatemala, population decline was initiated by lethal epidemics introduced via Mexico which immediately preceded the arrival of the Spaniards. Spanish and native eyewitness testimony indicate that the western highlands of Guatemala were densely settled at the time of contact. Native and Spanish colonial documents clearly show that Old World epidemic diseases were the major killers. These eyewitness accounts and documentary materials permit a tentative estimate of the contact-time population of Totonicapan as being of the same magnitude as the mid-twentieth century population. Thus, approximately four centuries were required for the native demog...