The recovery of an afromontane forest after slash and burn : a case study from the Nkandla forest.
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Date
2000
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Abstract
Clear cutting and subsequent agricultural processes lead not only to species loss, but also have
negative consequences for soil and water conservation. This study investigated the response
to, and effect of, deforestation due to shifting cultivation on the Nkandla forest complex
(NFC), a subtropical Afromontane forest. As a consequence of shifting agriculture,
abandoned areas are nutrient poor, have depleted seed banks and may lack the ability to
regenerate into species rich mature forest. The ability of forests to regenerate after disturbance
effects is extremely important for the maintenance of ecological diversity and the stability of
forest ecosystems.
The present study focused on the recovery of the NFC, after shifting agriculture was
practised along the forest margins. The NFC was sampled to determine: (1) how vegetation
structure, composition and plant species diversity differ between regrowth forest and
undisturbed forest ; (2) how continued disturbance and subsequent land use affects the rate of
recovery and regeneration of secondary forest ; and (3) what species establishment pattern, if
any, does the path of recovery follow during succession? Four different types of forest were
sampled, disturbed margin (DM) forest, disturbed interior (DI) forest , undisturbed margin
(UM) forest and undisturbed interior (UI) forest.
The study showed that recovery does occur and that in the NFC recovery patterns (in
terms of species diversity trends, biomass and basal areas) are similar to those found in other
tropical and sub-tropical regions. Floristic recovery proceeded in a way that required the
prerequisite establishment of forest margin tree species that would ultimately lead to a climax
condition described by undisturbed interior forest. Unimodal trends were found for stem
density and species richness across all four forest types, with basal area increasing steadily
from disturbed to undisturbed interior forest. These forest types and their floral composition
and structure described a gradient of decreasing disturbance, with disturbed margin forest
being the most disturbed type.
Continued harvesting of selected species is detrimental to the survival of these species.
Analyses showed that Rapanea melanophloeos, Cassipourea gummiflua, Curtisia dentata,
Ochna natalitia, Olea capensis subsp. macrocarpa and Strychnos henningsii have been overused.
Continued harvesting could result in critically low densities of these species and even
their local extinction.
Description
Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 2000.
Keywords
Forest ecology--KwaZulu-Natal., Forest regeneration--KwaZulu-Natal., Forests and forestry--KwaZulu-Natal--Nkandla., Shifting cultivation., Theses--Environmental science.