Prosopis pallida

Prosopis is invading the riverine forest, with negative impacts on the regeneration of native A. tortilis, and the productivity and diversity of the herbaceous layer. The negative impact is not due to dense shading or changed soil conditions, but seems rather to be the result of negative allelopathic effects.

Prosopis pallida (kiawe), a common deciduous tree found in arid, low elevation, disturbed sites on Molokai (USFWS 1992), has invaded areas adjacent to the hardened sand dunes of Moomomi Preserve where Tetramolopium rockii grows (USFWS 1992). Kiawe shades the ground cover and its vast root system dries the substrate by utilizing all available water (USFWS 1992). It thus competes with Tetramolopium rockii (USFWS 1992) for light, space, and moisture. (...) The major threats to Tetramolopium rockii are ungulate (axis deer and cattle) activity, competition with the alien plant Prosopis pallida (kiawe), human recreational impacts, and fire. Prosopis is invading the riverine forest, with negative impacts on the regeneration of native A. tortilis, and the productivity and diversity of the herbaceous layer. The negative impact is not due to dense shading or changed soil conditions, but seems rather to be the result of negative allelopathic effects.

Our findings showing the negative impacts of Prosopis invasions on native plants (Fig. 4, Fig. 5) are supported by other studies internationally. Prosopis invasions also negatively affected native species richness in Hawaii, India, Kenya and the United Arab Emirates (El-Keblawy and Al-Rawai, 2007, Kaur et al., 2012, Muturi et al., 2013). In the United Arab Emirates, native species richness and densities under Prosopis tree canopies were lower than at canopy margins and away from Prosopis canopies (El-Keblawy and Al-Rawai, 2007). This suggests that Prosopis was able to outcompete native plants for limited resources, such as light and water (Garcia-Serrano et al., 2007, El-Keblawy and Al-Rawai, 2007).