Possible control of Senna spectabilis (Caesalpiniaceae), an invasive tree in Mahale Mountains National Park, Tanzania

  • Published source details Wakibara J.V. & Mnaya B.J. (2002) Possible control of Senna spectabilis (Caesalpiniaceae), an invasive tree in Mahale Mountains National Park, Tanzania. Oryx, 36, 357-363.


Senna spectabilis, a tree native to South and Central America, was introduced to Mahale Mountains National Park in western Tanzania during the 1960s. In 2002, the species was found to have invaded approximately 225 ha of a 3, 000 ha forest area within the park. Girdling and felling was tested as a possible means to control this exotic species.

Three 0.25 ha forest plots, intensively invaded by S.spectabilis, were selected in March 1996.  All native and non-native trees, saplings, and seedlings, within each plot were counted. S. spectabilis trees were girdled (i.e. bark stripped from the tree base about 60cm above ground level) in the first plot and felled in the second plot; no action was carried out in the third plot, which was a control. Over the following 90 days, S.spectabilis ‘poles’ (i.e. young trees 2-10 cm diameter) and saplings were cut and germinating seedlings were uprooted 2-3 times a week in the first and second plots.   

Before the experimental control, tree composition and age structure in the three plots (S.spectabilis and native tree species) was similar.  Four years later, the numbers of S.spectabilis was significantly lower in girdled plot (seedling and saplings -87.6%; poles and trees -83.5%) and felled plot (seedling and saplings -95.7 %; poles and trees -97.5%) compared to the control plot, where the numbers of S.spectabilis had increased (seedling and saplings +4.3%; poles and trees +35.9%).

Girdling and felling also encouraged regeneration of native tree species, with the greatest increase in the girdled plot (seedling and saplings +672.5 %; poles and trees +1047.1%). 
Native trees species, unrecorded at the start of the experiment, were found at the girdled, felled and control plots (11, 6 and 3 species) respectively.
The removal of S.spectabilis encouragee natural regeneration of native tree species in degraded forest.
Note: If using or referring to this published study, please read and quote the original paper, the abstract of which can be viewed at:


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