grassy reconstruction: a plant competition trial and insights into the relative competitiveness of...

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 & Locationrationale 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

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