Allelopathic effects of the invasive Prosopis juliflora (Sw.) DC. on selected native plant species in Middle Awash, Southern Afar Rift of Ethiopia

Samuel Getachew,Tadesse Woldemariam,Sebsebe Demissew

doi:10.3391/mbi.2012.3.2.05

Abstract

The allelopathic effects of the invasive Prosopis juliflora (Sw.) DC. was studied on seed germination and seedling growth of Acacia nilotica (L.) Willd. ex Del., Acacia tortilis (Forssk.) Hayne, Cenchrus ciliaris L. and Enteropogon rupestris (J.A. Schmidt) A. Chev. Vegetation sampling in different habitat types in the area was made to identify the target plant species. Comparison of canopy characteristics among P. juliflora, A. nilotica and A. tortilis was also made to observe differences if any in canopy closure. P. juliflora was recorded in all habitat types in highest density and observed affecting the plant diversity there in. Its growth characteristics and dense thicket formation restrict light to the ground flora and hence diminishes plant diversity. Leaf, bark and root aqueous extract of P. juliflora at 0, 0.5, 0.8, 1, 2 and 6% were prepared and their effect studied on germination percentage and seedling growth of the study plant species. Germination of A. nilotica and A. tortilis was not affected by all aqueous extracts of different organ parts of P. juliflora while leaf and root extracts at higher concentrations inhibited germination of C. ciliaris and E. rupestris. Shoot and root growth of the study species were inhibited by leaf and root at higher concentrations. Seed germination of all species except A. nilotica was inhibited by soil amended with decaying plant parts and under canopy soil. The effect is species specific and annuals (grasses and herbs) were affected more than perennials. Leaf seems to contain greater number/ amount of inhibitors than does root and bark. Bark seems to contain the least. Heavy accumulation of toxic substances at under canopy soil of P. juliflora may be one of the reasons for its invasiveness and low plant diversity.

Highlights

Biological invasions by non-native species are one of the worst ecological components of global environmental change
The lowest value of the range for mean peroxidase concentrations was found for Group T in Pond 7 (6.71 μg/gm FW), for Group A in Pond 2 (6.72 μg/gm F.W.) and for Group B in Pond 3 (1.31 μg/gm F.W.)
This study shows evidence in favour of two specific traits of Alternanthera philoxeroides that are reported to facilitate plant adaptations in different environments, namely, its ability to grow even under high strand density and its ability to withstand a broad range of environmental conditions

Summary

Introduction

Biological invasions by non-native species are one of the worst ecological components of global environmental change. Alternanthera philoxeroides (Martius) Griseb (Amaranthaceae), alligator weed, an invasive perennial wetland herb originating from South America (Maddox 1968), has many attributes of a successful invasive weed such as rapid growth and vegetative propagation (Tao et al 2009; Wang et al 2009) as well as a broad ecological amplitude (Geng et al 2007) This amphibious clonal plant has invaded many ecosystems worldwide (Julien et al 1995), including riparian zones (Pan et al 2006) and agricultural lands (Spencer and Coulson 1976), and is regarded as one of the worst weeds of the world (http://www.waikatoregion.nz). Invasive plants posses certain characteristics which make them more competent to adapt and propagate in newer environments/ habitats and understanding these mechanisms is crucial for managing invasive plant species (Mack et al 2000)

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