Biology Reference
In-Depth Information
sources for some species are sparse and technology for native seed production is
poorly developed. Thus, although initial trials suggest that postfire seeding can lead
to the successful establishment of native species, in reality restoration will be lim-
ited by availability of appropriate seed and will therefore likely be of limited spe-
cies composition. Since 2006, R. Loh and staff have been establishing native plant
seed
orchards
in various portions of the park to serve as a source of material for
future restoration efforts. Their efforts will provide critical information on native
plant propagation and possibilities for large-scale seed production.
Are the communities that are being created actually resilient to fire? This was a
critical element of the initial argument for this approach to restoration/revegetation.
Testing this, however, will require reburning of the
revegetated
sites. This has only
been done for two small sites and it was observed that
S. chrysophylla
individuals
regrew from root sprouts and
D. viscosa
individuals regenerated from the seedbank.
We do not yet know how the other species would respond or over what range of fuel
conditions populations of desired native species will show resilience.
On the leeward side of Hawaii, S. Cordell and others (Institute of Pacific Island
Forestry, Hilo Hawaii, personal communications) are experimenting with
green
stripping
as part of large-scale ecosystem rehabilitation in fire-prone shrublands
and woodlands. Their goal is to prevent the spread of
P. setaceum
fueled wildfires
into remnant patches of native dry forest that harbor rare species. Their approach
focuses on finding species with fuel characteristics that will suppress grass growth
and reduce fire spread rates. Although such an approach seems unfeasible in the
vast stretches of grass-invaded submontane forests and shrublands in Hawaii
Volcanoes National Park, it is being considered in areas where fire could spread
from grass-invaded portions of the Park into a nearby residential subdivision. In
addition, active fire suppression will help to slow the further loss of the prefire for-
ests and shrublands. Special ecological areas with rare or unique species have been
identified by Park personnel. Protecting these areas from fire is a high priority. This
may be done through fire suppression, manual fuel reduction, or potentially green
stripping if it can be effectively done.
Could the reestablishment of native species such as we have tried eventually lead
to the establishment of some biotic resistance to exotic grass invasion? This is pos-
sible for
M. minutiflora
because its growth is sensitive to shading (D'Antonio et al.
2001a). However,
S. condensatum
and
A. virginicus
both tolerate a high level of
shade so it would take a very dense shrub or tree canopy to reduce their invasion
rate. Nonetheless, high densities of native shrubs could decrease the fine fuel bio-
mass that accumulates with exotic grass invasion, potentially reducing fire inten-
sity. Despite this, the long-term persistence of native species in these areas will rely
more on creating a community of species resilient to fire than any ecological resist-
ance that these communities might provide.
Are we restoring important ecosystem functions to these sites? Reestablishment
of a heterogeneous plant canopy is a potential benefit of managing these grass inva-
sions by rehabilitating these ecosystems with native woody species. As mentioned
previously, Freifelder et al. (1998) showed that the homogenous exotic grass can-
opy promoted high wind speeds and therefore faster fire spread rates. The breakup
