Environmental Engineering Reference
In-Depth Information
suggest that the floristic composition of the southwestern E. marginata can
reflect the initial vegetation complex for many years after restoration (Koch &
Ward
1994
; Grant & Loneragan
2001
; Norman et al.
2006
). That said, both cases
(the northern and southwestern forests) have a predicable dominance of
acacias, that are short-lived and produce copious seed, for the first decade or
so of restoration. After this, the overstorey eucalypts begin to dominate the
forest and the acacias decline in their relative to the basal area (
Figs. 15.7b
and
15.7c
). The overstory vegetation is typically dominated by just a few standard
species (
Figs. 15.7c
and
15.7d
) (Spain et al.
2006
; Koch & Samsa
2007
) and it is in
the understory where the majority of floristic diversity occurs and needs to be
re-established (Koch
2007a
).
Accumulation and quality of litters
Litter accumulation is considered the major accession route for both organic
matter and most plant nutrient elements to the soil (Spain
1973
) and is also an
important habitat for invertebrate colonisation of restored lands with direct
implications for soil development and nutrient cycling (Abbott
1989
; Ward
et al.
1991
). It is therefore measured as a key indicator of ecosystem develop-
ment (Majer et al.
2006
; Grant et al.
2007
) and is now also of interest as a
precursor to soil carbon as a component of carbon accounting (Tibbett
2008
).
Litters tend to develop as a function of above-ground primary productivity,
so litters tend to accumulate slowly in the first few (up to 8) years and it takes
about a decade of ecosystem development to reach almost concurrent canopy
and litter closure (
Fig. 15.8
). However, within a decade after this, litters accu-
mulate masses greater than that found in natural undisturbed reference sites.
Nonetheless, litters are evidently decomposing in these restored systems
(Grant et al.
2007
) as is apparent from the lower mass of litters after the wet season
(
Fig. 15.8
).
Figure 15.8.
Litter properties in the rehabilitated and unmined native forest soils:
(left panel). Percentage surface coverage of litter, late dry season 2002 (right panel).
Seasonal changes in dry mass (after Spain et al.
2006
).
