The long‐term impact of elephant browsing on baobab trees at Msembe, Ruaha National Park, Tanzania

Abstract

SummaryThe baobab tree population of the Msembe study area was surveyed for the third time in 1989. Although tree density had dropped between the 1976 and 1982 surveys, there was no significant change between 1982 and 1989, probably because most bull éléphants had been killed by poachers. The change in the baobab size distribution between 1976 and 1989 is similar to that predicted by a model simulating the effects of elephant browsing on baobabs. It suggests that elephant browsing has a different effect on baobab numbers compared with browsing on other tree populations in the same study area.RésuméLa population de baobabs de la zone d'étude de Msembe fut étudiée pour la troisième fois en 1989. Bien que la densité de arbres ait chuté entre les études de 1976 et de 1982, on n'a pas constaté de changement significatif entre 1982 et 1989, probablement parce que la plupart des éléphants mâles avaient été tuéus par des braconniers.Le changement dans la distribution des tailles des baobabs entre 1976 et 1989 est similaire à celui prédit par un modèle simulant les effets des éléphants se nourrissant sur les baobabs. Ceci suggère que le nourrissage des éléphants a un effet différent sur le nombre de baobabs que sur d'autres populations d'arbres dans la même zone d'étude.

Status of African baobab (<i>Adansonia digitata</i>) across Gonarezhou National Park, Zimbabwe

“…Several factors including those not investigated, could explain this spatial distribution. Wilson (1988) and Barnes et al (1994) suggested that baobab densities are very variable across landscapes as they are affected by a number of establishment factors, such as insect outbreaks, past human activities, droughts or edaphic variables (Edkins et al 2007), all interacting in a complex and unpredictable ways (Scholes and Walker 1993). In Gonarezhou, Tafangenyasha (1992) suggested that herbivores (e.g., elephant and tree squirrels), drought, and increased density of associated species could bring about deaths of baobabs.…”

Resprouting of woody saplings following stem snap by wild pigs in a Malaysian rain forest

“…PFR may be an extreme case of increased animalrelated damage resulting from increases in animal densities within reserves, but shifts in community composition following animal-induced damage to vegetation have been proposed in several studies, e.g. elephant browsing in African savannahs (Barnes et al 1994) and white-tailed deer browsing in eastern North America (Long & Carson 1998). We concur with Guariguata (1998) that 'interspecific patterns of post-damage response' may generally be a critical lifehistory parameter that affects the structure, species composition and diversity of tropical forests.…”

Development and Parameterization of a Rain- and Fire-driven Model for Exploring Elephant Effects in African Savannas

“…Rather, we assess the impact of elephants visiting this square kilometer, i.e., elephants can be dealt with as a timevarying input into the model, and different scenarios may be analyzed. We consider this approach more realistic than limiting our analysis, as in some earlier studies [4,5,82,99], to various constant elephant "stocking densities." In addition, this approach naturally extends to a geographic information systems setting in which our model is used to evaluate the effects of elephants in each of many grid cells on top of which elephant movements are imposed (cf.…”

“…for transitions within metaclasses), we set l i =1 (i=2, 3,4,6,8). Any given level of growth, g i , may also entail shading out other plants in the same or lower height class and so we introduce h i as a "crowding coefficient", representing the proportion of plants overshadowed by the individuals growing from class i to i+1 (see Fig.…”