Patterns of seed dispersal and establishment of the invaderProsopis juliflorain the upper floodplain of Tana River, Kenya

Abstract

Invasive species in Africa have important impacts on food security and biodiversity conservation. African floodplains in arid areas are critical wildlife habitats in addition to crop production and dry season livestock grazing. The study aimed to understand the patterns of spread of the invader Prosopis juliflora in a typical African floodplain characterised by both multiple dispersers and habitats. Data was collected on faecal seed density, establishment and vegetation composition, and subjected to non-parametric tests and regression analysis. The results showed that both livestock and wildlife species played a critical role in dispersal of Prosopis juliflora, especially yellow baboons (Papio cynocephalus), bush pigs (Potamochoerus larvatus), donkeys and goats. Habitat preference of wildlife dispersers and livestock herding patterns influenced the spatial pattern of invader seed influx. Establishment of Prosopis juliflora was enhanced by ecological disturbance such as in rested crop fields and habitats outside conservation areas as compared to those inside. Establishment was also higher inside the floodplain than outside probably due to higher seasonal soil resources. Lastly, indigenous woody species diversity declined significantly as the density of Prosopis juliflora increased. We conclude that patterns of spread of Prosopis juliflora were related to ecological disturbances, type of disperser and flooplain effect.

Chemical composition and <i>in vitro</i> degradation of red and white mesquite (<i>Prosopis laevigata</i>) pods

“…Approximately, 40 species (trees and shrubs) are native to North and South America (Pasiecznik et al, 2001). However, they have been introduced and have adapted to dry lands of Asia, Africa and Australia because of their commercial value, contribution to land rehabilitation, and provision of fodder and firewood (Mwangi & Swallow, 2008;Mworia et al, 2011). Mesquite pods (referred to henceforth as fruits) vary in colour from white to red and dark brown.…”

Allometric equations for estimating biomass in naturally established Prosopis stands in Kenya

“…Provision of wood fuel was one of the main objectives of Prosopis species introduction in the country (Mwangi and Swallow, 2008). This objective is not yet fully realized, despite the successful establishment of the species in the initial trials (Maghembe et al, 1983;Olukoye et al, 2003) and their subsequent spread into other unintended areas, as a result of natural seed dispersal by livestock, wild animals and water (Mwangi and Swallow, 2008;Mworia et al, 2011). Recently, the government gave a policy direction for utilization of Prosopis species to control their further spread in areas where they are invasive (GOK, 2007).…”

Invasive Plant Species and Biomass Production in Savannas

“…Propagule pressure across habitats in an ecosystem can be enhanced if the invasive species has multiple dispersal agents. For example Mworia et al (2011) observed that the invader Prosopis juliflora was dispersed by several wildlife and livestock species within the savanna of the upper Tana River floodplain resulting in a significant association between habitat type and disperser type indicating the importance of habitat preference and livestock herding patterns. Characteristics of non-native species can be an indicator of its potential invasiveness in the new community.…”

“…It is important to note that disturbances create opportunities for both natives and non-natives and for the prevalence of non-natives to increase there must a source of non-native propagule (Lockwod et al, 2007). Lets again take the example of the Prosopis juliflora in savanna floodplain of upper Tana River in Kenya where Mworia et al (2011) found that ecological disturbance manifested by rested crop fields not only enhanced the establishment of the invader but also had a positive effect on indigenous woody species. Rested crop fields have vegetation and soil disturbance and represent early stages of plant succession.…”