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Subcanopy Trees (subcanopy + tree)

Distribution by Scientific Domains

Life Sciences	75%

Selected Abstracts

Tree mortality due to an El Niño flood along the lower Tana River, Kenya

AFRICAN JOURNAL OF ECOLOGY, Issue 1 2009
Julie Wieczkowski
Abstract This study investigated forest tree mortality as a result of the extremely strong 1997,1998 El Niño flood in Tana River, Kenya, directly tested how mortality varied in relation to tree species and diameter at breast height (DBH), and indirectly tested how mortality varied in relation to floodwater depth. The study forest was under 2 m of water for approximately 71 days, from December 1997 until February 1998. Twenty-five liana, subcanopy tree, and canopy tree species were selected based on their importance in the diet of the Tana River mangabey (Cercocebus galeritus Peters), a critically endangered primate endemic to the Tana River. Reproductive-sized individuals of these species were enumerated in 16.25 ha. I also enumerated trees killed by the El Niño flood, recorded their location in the forest, and measured their DBH. Ninety-two trees in fifteen species were killed by the flood. There were significant differences in mortality by species and by 0.25 ha quadrat. There were negative correlations between number of dead and DBH, number of dead and distance from the river, and per cent of quadrat killed and distance from the river. There appear to have been few long-term consequences of the El Niño flood in the forest or for the mangabeys. Résumé Cette étude s'est intéressée à la mortalité des arbres en forêt due à la très grave inondation causée en 1997,1998 par El Niño dans la rivière Tana, au Kenya. J'ai testé directement de quelle manière la mortalité variait selon l'espèce des arbres et leur diamètre à hauteur de poitrine (DBH), et indirectement comment elle variait avec la profondeur de l'eau. La forêt étudiée est restée sous deux mètres d'eau pendant environ 71 jours, de décembre 1997 à février 1998. Vingt-cinq espèces de lianes, d'arbres de sous-canopée et de la canopée ont été sélectionnées en fonction de leur importance dans le régime alimentaire du mangabey de la rivière Tana (Cercocebus galeritus Peters), une espèce de primate en danger critique d'extinction qui est endémique de cet endroit. Les individus de ces espèces ayant la taille requise pour se reproduire furent dénombrés sur 16,25 ha. J'ai aussi dénombré les arbres tués par l'inondation d'El Niño, noté leur emplacement dans la forêt et mesuré leur DBH. Quatre-vingt-douze arbres appartenant à 15 espèces ont été tués par cette inondation. Il y avait des différences significatives de mortalité selon les espèces et par quadrat de 0,25 ha. Il y avait des corrélations négatives entre le nombre d'arbres morts et leur DBH, entre le nombre d'arbres morts et la distance par rapport au lit du fleuve, et entre le nombre d'arbres morts par quadrat et cette distance. Il semble qu'il y ait peu de conséquences à long terme de cette inondation dans la forêt ou pour les mangabeys. [source]

Nest-site selection by Common Black-Hawks in southwestern New Mexico

JOURNAL OF FIELD ORNITHOLOGY, Issue 1 2008
Giancarlo Sadoti
ABSTRACT Despite the interest of resource managers and conservationists in the status of Common Black-Hawk (Buteogallus anthracinus) populations in the southwestern United States, little is known about their nesting success and habitat requirements. Because such information is essential for effective population and habitat management, I examined the nesting success and nest-site selection of Common Black-Hawks in southwestern New Mexico during 2000 and 2001. Of the 37 nesting attempts in 21 territories, ,1 young fledged from 25 nests (68%). Comparison of nest-sites and nonused sites suggested that breeding Common Black-Hawks selected nest-sites in areas with a sparser and shorter subcanopy tree layer and in trees with a smaller trunk diameter and a greater minimum crown diameter. These differences appear to be related to variation in forest ages within territories, with nonused sites having fewer, but older, canopy trees than nest-sites. Sites with younger, smaller subcanopy trees may provide forest structure for more effective foraging, whereas the characteristics of younger nest tree canopies may reduce the risk of nest predation or offer more protection from inclement weather. Due to the limited range of this species in the southwestern United States, efforts to encourage the establishment and maturation of riparian forests in Common Black-Hawk breeding areas could be important in sustaining available nesting habitat and, in turn, maintaining or expanding current population levels. SINOPSIS Aunque existe interés de parte de profesionales en manejo de recursos y conservacionistas en el estatus de las poblaciones de Buteogallus anthracinus en el sudoeste de los Estados Unidos, poco se conoce sobre su éxito de anidamiento y requerimientos de hábitat. Por la razón que esta información es esencial para el éxito del manejo poblacional y del hábitat para esta especie, examiné el éxito de anidamiento y la selección del lugar de anidamiento de Buteogallus anthracinus en el sudeste del estado de Nueva México durante el 2000 y el 2001. De los 37 intentos de anidamiento en 21 territorios, ,1 de los polluelos volaron de 25 nidos (68%). Una comparación entre lugares donde se ubicaban los nidos y sitios no utilizados para anidar indica que individuos seleccionaron lugares para anidar en áreas con una menor cobertura y una menor altura del sub-dosel. Adicionalmente, los nidos fueron ubicados en árboles con un menor diámetro del tronco y con un mayor diámetro mínimo de la corona. Estas diferencias parecen ser relacionadas a la variación en la edad del bosque dentro de los territorios, con sitios no utilizados caracterizados por un número menor de árboles del dosel pero las cuales tienen una edad mayor que los árboles del dosel en los sitios donde se ubicaron los nidos. Sitios con árboles en el sub-dosel de menor edad y de menor tamaño podrían proveer la estructura del bosque necesaria para un forrajeo mas efectivo, mientras que las características de las coronas de los árboles de menor edad en la cual se encuentra el nido podrían reducir el riesgo de la depredación del nido o proveer mas protección de mal tiempo. Dado el rango limitado de esta especie en el sudeste de los Estados Unidos, los esfuerzos para animar el establecimiento y la maduración de los bosques riparios en las áreas de anidamiento de esta especie podrían ser importantes para mantener el hábitat disponible para anidar y a la vez mantener o expandir los tamaños actuales de las poblaciones. [source]

Disturbance history of a European old-growth mixed-species forest,A spatial dendro-ecological analysis

JOURNAL OF VEGETATION SCIENCE, Issue 5 2005
Bernhard E. Splechtna
Abstract Question: We were interested if and how variation in frequency and/or size of disturbances affect the dynamics of a montane old-growth forest in Central Europe. Location: The forest, co-dominated by Fagus sylvatica, Picea abies and Abies alba, is located in Lower Austria and represents one of the few sizable virgin forests in Central Europe. Methods: We extracted cores from 100 trees using systematic grid sampling (grid cell size 10 m × 10 m) on each of four 1-ha plots distributed across the old-growth remnant of 300 ha. We inferred disturbance events from rapid early growth and release events. For defining release criteria, we applied the boundary line method. We investigated the spatial structure of current age and gap distributions and past disturbance events in grid cells, using a pair density statistic. Results: The disturbance histories indicate decades with peaks and also extended periods without disturbance. Some peaks occurred synchronously at three of the four plots (1910s, 1930s, 1960s and 1980s). Peaks and gaps in the disturbance chronologies widely agreed with peaks and gaps in the age distributions. Most disturbance events during single decades showed a random spatial distribution. Conclusions: There is considerable variation in disturbance frequency and/or severity over time. Most disturbance events will rather thin the stand than clear larger areas at once. Following scattered disturbance two pathways occur: (1) gap expansion leading to creation of larger gaps, and (2) gap closure by lateral encroachment or by subcanopy trees growing into the canopy. [source]

The Effect of Hurricane Iris on the Food Supply of Black Howlers (Alouatta pigra) in Southern Belize1

BIOTROPICA, Issue 1 2005
Mary S. M. Pavelka
ABSTRACT Hurricanes frequently affect the forests of South and Central America; however, few studies have quantified their effects to forest structure, especially when concentrating on the food supply of an animal population. Hurricane Iris made landfall in Southern Belize on 8 October 2001, severely damaging a 52 hectare site where the behavioral ecology of a population of Central American Black Howlers (Alouatta pigra) had been under study for 2.5 yr. The hurricane resulted in a mortality rate of 35 percent for major food trees, which was primarily attributed to uprooting, snapping, and major delimbing. This damage accounted for 97 percent of the food tree loss between the two sample periods. Tree species differences were found in both the percentage loss and category of damage to food trees. Trees of different heights also experienced different percentage loss and levels of damage; subcanopy and emergent trees experienced higher loss than canopy trees, and subcanopy trees were frequently uprooted. This was partially attributed to a lack of buttressing on these subcanopy trees. Buttressing was found to decrease the frequency of uprooting. Tree size was the only factor that did not influence either damage or death. Trees from which fruit were eaten by black howlers died more than twice as often as did trees eaten for leaves. [source]