Transcript CPW_PRES - Cumberland Plain Seeds

GRASSY RECONSTRUCTION:
A Plant Competition Trial and
insights into the relative competitiveness of
two Cumberland Plain grass species
Some Challenges in Reconstructing
Grassy Habitats
• Seed supply
• Seed establishment
knowledge
• Weed control
• Ecological approaches
to weed control
• Managing for diversity
and weed resistance
A Plant Competition Trial:
-Trial Overview-
Monocultures & Mixtures
Species Selection & Location
rationale for sites & species
Bulking-up Seed for Trial
Trial planting in 1996
Trail Measurements
An Early Hypothesis
Mixtures would be more
productive (and therefore weed
resistant) than monocultures;
due to resource partitioning,
mutualism, and diversity of
growth habits and requirements
Some Microlaena & Chloris Results
% of total plot
productivity
Microlaena in Chloris mixtures as a
% of total plot productivity over time
40
32.17
30
17.44
20
10
8.77
0
Sampling year: 1998, 1999 & 2004
% of total
plot
productivity
Chloris in Microlaena mixtures as a
% of total plot productivity over
time
100
91.2
50
50
3.5
0
Sampling year: 1998, 1999 & 2004
Comparison of 1998 herbage mass
for Microlaena and Chloris
Herbage mass
160
141.36
140
134.06
120
100
80.06
80
60
40
20
0
Mic. mono, Chloris mono, & CM mixture
Comparison of 1999 herbage mass
for Microlaena and Chloris
45.61
Herbage mass
46
44
42
40.81
41.76
40
38
Mic. mono, Chloris mono, & CM mixture
Comparison of 2004 % cover for
Microlaena and Chloris
% cover
60
50.62
50
36.92
40
30
27.4
20
10
0
Mic. mono, Chloris mono, CM mixture
Observations: Mic. & Chloris
• Mic. inferior competitor early and therefore more
productive in monoculture than in mixture
• Chloris stronger competitor early and performing well
in mixture and monoculture
• Chloris very productive early (good early cover)
• By 2004 Mic. is the stronger competitor and is
displacing Chloris
• Mic. monocultures are the superior treatments with
highest cover scores in 2004
• Chloris loosing productivity over time
• Mic. gaining productivity over time
Hypothesis Outcome
• In many circumstances (time of
sampling, species make-up in
treatment, etc) monocultures
were more productive (not
expected)
• A new observation: slower
growing species better
competitors in the longer term
Consistent with Ecological
Theory of Tillman:
At moderate to low mortality
rates, transient dominance is
predicted whereby species
may actually be replaced by
slower growing species with
lower resource requirements
Strategies & Implications of Results
• Seeding of monoculture mosaics may be more suitable
than blended mixes in some circumstances (for some
species)
• Some species will perform better in blends
• Inclusion of slower growing & longer lived species is
important
• Quick growing species such as Chloris may be a useful
cover & nurse crop for slower growing species
• Slower growing species may be best sown into alternative
seed beds (not cultivated) such as into a native cover crop
or into sprayed down exotic cover
Herbicide & Sowing Rate Trials
Application of trial results to
seed production & rehab. areas
Reconstruction can be successful;
success requires…
• Reliable seed supply from
local or regional sources
• Ongoing improvements in
establishment knowledge,
including weed control
• Careful consideration of
genetic & provenance
policies in the context of
fostering seed supply
sufficient to meet the need