Environmental Engineering Reference
In-Depth Information
At Wodonga, species growth to 4 years was
E. saligna
(134 m
3
/ha stem volume, 84 Mg/ha aboveg-
round biomass),
EG
(126, 80),
Populus deltoides
×
nigra
(85, 47),
Pinus radiata
(61, 42),
Casuarina
cunninghamiana
(43, 49), and
E. camaldulensis
(40, 52) (Stewart et al. 1988). At Kyabram, species
ranking at 4 years was
EG
,
E. saligna
,
E. globulus
, and
E. camaldulensis
(Baker 1998).
At Werribee with
E. globulus
,
EG
,
E. saligna
, and
E. camaldulensis
and densities of 1333, 2500,
and 4444 trees per ha, stem volume growth to 4 years across planting densities varied:
E. globulus
(57-108 m
3
/ha),
EG
(46-89), and
E. saligna
(37-77) (Delbridge et al. 1998). Tripling planting den-
sity approximately doubled potential yield.
At Bolivar (Boardman et al. 1996, Shaw et al. 1996), initial tree growth rates were relatively high,
with species ranking to 4 years of
E. globulus
(139 -182 m
3
/ha overbark stem volume),
C. glauca
(85 -111),
E. occidentalis
(90 -92),
EG
(75-91), and
E. camaldulensis
(59 -71).
A Wagga Wagga project developed national guidelines for sustainable management of water,
nutrients, and salt in effluent-irrigated plantations. The project studied biophysical processes under
three effluent irrigation rates: medium (M, rate of water use less rainfall), high (H, about 1.5 times
M), and low (L, about 0.5 times M). The main species studied were
EG
and
P. radiata
. Tree spacing
was 3 × 2 m. Among several conclusions, the project identified best eucalypt species and radiata
pine clones for effluent-irrigated plantations for sustainable biomass production, salt sensitivity in
tree species, and water use efficiency (Myers et al. 1996). After 6 years, halving irrigation (M vs. L)
led to only a 10% decrease in volume production—20 to 18 m
3
/ha per year.
At Shepparton (Baker et al. 1994), both
E. globulus
and
EG
grew well through 5 years, with
E.
globulus
larger than
EG
(172 vs. 128 m
3
/ha) (Duncan et al. 1999). Stem volume MAIs were 30 and 38
m
3
/ha for
E. globulus
and 23 and 31 m
3
/ha for
EG
for 1333 and 2667 trees/ha, respectively. Coppice
growth at 2 years varied between 31 and 42 Mg/ha and was greater than that of the planted seedlings.
Biomass production for a 12-year cycle of 3-, 6-, and 12-year rotations was projected to be 330, 390,
and 350 Mg/ha, respectively, for
E. globulus
growing at an estimated peak of 45 m
3
/ha per year.
In 1998, Australia had approximately 1.25 million ha of plantations, 23% hardwoods (
E. globulus
,
E. nitens
,
E. regnans
, and
EG
) and 77% softwoods (
Pinus radiata
,
P. elliottii
,
P. caribaea
,
P. pinaster
,
and
Araucaria cunninghammii
) (Baker et al. 1999). Although softwood plantations managed in 20-40
year rotations for veneer logs, sawlogs, posts, poles, and pulpwood have bioenergy potential from silvi-
cultural and product residues, the rapidly developing 10-15 year rotation hardwood pulpwood industry
also has potential. Australia has a plantation goal of approximately 3 million ha by 2020.
New hardwood plantations in Australia totaled 49,000 ha per year in 1998 and were expected to
increase (Baker et al. 1999). These plantations have been mostly for pulpwood on agricultural land
in southwestern Western Australia, southeastern South Australia, Victoria, Tasmania, and north-
coastal New South Wales. Assuming a growth rate of 20 m
3
/ha per year and ultimately 500,000 ha,
potentially 500,000 Mg per year of wood residue will be available for bioenergy production.
In southern Australia, SRWCs with 3-5 year rotations may be used for bioenergy after alle-
viating salinization of land and water in dryland (300-600mm annual rainfall) farming systems
(Sochacki et al. 2007). Planting density and slope position had strong influences on biomass yield.
Mean 3-year yields of
E. globulus
,
E. occidentalis
, and
P. radiata
planted at 500, 1000, 2000, and
4000 trees/ha at upper-, mid-, and lower-slope positions ranged from 12 to 14 tons/ha. Biomass yield
consistently increased with planting density, generally greatest at 4000 trees/ha. The best
E. globu-
lus
and
E. occidentalis
yields, 16.6 and 22.2 tons/ha, respectively, were at lower slope positions
at 4000 trees/ha, whereas the best yield of
P. radiata
was 15.4 tons/ha in an upper slope position.
E. globulus
did not perform well on the upper-slope site.
E. occidentalis
has some salt tolerance.
P. radiata
yields were relatively low in the lower landscape being relatively small. Using high
planting densities and different species for different hydrological settings can optimize biomass
productivity. Higher yields are expected under more normal rainfall conditions.
Root:shoot (R:S) ratios that did not vary significantly between planting density and slope posi-
tion but varied between species (
E. occidentalis
— 0.51,
E. globulus
— 0.31,
P. radiata
—0.33) have
implications for harvesting systems, in terms of biomass yield and stump removal (Sochacki et al.
