Succession and management - Ecological Applications: Toward a Sustainable World - page 229

villagers in Sumatra. They plant benzoin gardens ( S. paralleloneurum ) after clearing
small patches (0.5-3.0 ha) of the understory of montane broadleaf forest. Two years
later farmers remove branches from the larger trees to allow light to reach the sap-
lings, leaving the wood to decay on the forest fl oor. Annual tapping of benzoin
begins after 8 years. Yields usually decline after 30 years of tapping but resin may
be harvested for as long as 60 years before the garden is left to return to the
forest.
Garcia-Fernandez et al. (2003) identifi ed three categories of garden: G1 was the
most plantation-like, with intensive thinning and high densities of S. paralleloneu-
rum trees, and G3 was the most forest like. Tot a l t ree spec ies richness was high in
plots of 'primary' (pristine) and 'secondary' forest (30-40 years after gardening had
ceased) but also in most of the gardens themselves, except for the most intensely
managed cases where richness was lower (but still with a remarkably high average
of 26 tree species) (Figure 8.12a). As predicted by succession theory (Box 8.1),
climax species typical of mature forest were most common in primary forest and
there was a more even mix of pioneer and mid-successional tree species in second-
ary forest and in the least intensively managed gardens (G3) (Figure 8.12b). Gardens
with an intermediate or high intensity of management were dominated by mid-suc-
cessional trees (mainly because benzoin trees are in this category).
Indigenous people are usually aware of a wide range of uses for forest plants.
Figure 8.12c shows the representation in the garden and forest plots of trees in each
of four classes: no known use (12%), subsistence use (food, fi ber or medicine) (42%),
local market use (23%) and international market use (23%). The international cate-
gory dominates in intensively managed gardens (i.e. benzoin and its products) while
trees in the subsistence and local market categories were well represented in less
intensively managed gardens and in primary and secondary forest.
Although benzoin gardening requires competing vegetation to be trimmed back,
tree species richness remains high. This traditional form of forest gardening main-
tains a diverse community that recovers rapidly when tapping ceases. It represents
a sustainable balance between development and conservation.

8.3.2 Aboriginal
burning enhances
harvests

Fire is used as a management tool in a number of situations, including the mainte-
nance by gamekeepers of prime game bird habitat in Scottish moorland. Fire is an
important management tool also for the Australian aborigine clan who own the
Dukaladjarranj area of Arnhem Land (Figure 8.13a). Burning, to provide green
forage for game animals, is planned by custodians (aboriginal people with special
responsibilities for the land) and focuses on dry grasses on higher ground, before
moving progressively to moister sites as the dry season runs its course. Each fi re is
small in extent and of low intensity, producing a patchy mosaic of burned and
unburned areas and thus a variety of habitats at different successional stages.
Towa rd t he end of the dry season, when the weather is very hot and dry, burning
ceases except where it can be carefully controlled (such as the reburning of previ-
ously burnt areas).
In a study carried out by indigenous people and professional ecologists, Yibarbuk
et al. (2001) lit experimental fi res to assess their impact on the vegetation and
animals. They discovered that burned sites attracted large kangaroos (Figure 8.13b)
and other game animals, and yams and other important plant foods remained
abundant. These results would have hardly been a surprise to the indigenous