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Recalcitrant Planting

Natural seed from the returned topsoil, and seed that is collected and hand or machine spread at the time of ripping, returns the majority of jarrah forest plant species back into the rehabilitated minepits.  However some species produce very little seed and are therefore difficult to restore from the natural top soil seed bank or from collected seeds.  We call these “recalcitrant” species.  They are often species that recover from natural disturbances by re-sprouting from tubers, rhizomes and other underground parts.  Re-sprouting species give the jarrah forest a high resilience to natural disturbances, particularly fire and grazing, and hence are a crucial component of the ecosystem.  Our botanical diversity target of 100% species richness includes a requirement for 20% of the species to be “recalcitrant” species.

Little was known about how to propagate or grow most of these species – they are not used in the horticultural industry.  We grow them from either cuttings, small amounts of collected seed or from tissue culture.  Tissue culture is the most difficult and expensive propagation method and is only used when there are biological barriers to other methods.  In 2007, Marrinup Nursery produced 219,800 plants of 25 different recalcitrant species.  In the last decade Marrinup Nursery has produced over 1.5 million plants for rehabilitated areas in the jarrah forest.  Each year, in winter the ~ 600ha of rehabilitation across both Huntly and Willowdale, is planted with these recalcitrant species by hand.  Survival rates are between 60% and 80% after 18 months.

Many of these species, particularly the grass-like rushes and sedges and the grass-trees of the Xanthorrhoeaceae family, are the favourite food source for kangaroos in the post-mining rehabilitated areas and can be killed by intensive grazing.  This has two implications; firstly, that these species have an important function in the restored ecosystem as kangaroo food and secondly, the plants need protection when they are small, otherwise they can be killed by overgrazing.  Small mesh bags are used to protect the grass-like species from overgrazing. 
 


Nursery Assistants

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Nursery Assistants work in the laboratory to carefully divide recalcitrant plant species.

Recalcitrant species.

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Recalcitrant species are grown at the Marrinup Nursery and planted into rehabilitated mine pits during winter each year.

(Loxocarya cinerea)

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A thriving 2 year old recalcitrant plant (Loxocarya cinerea) in rehabilitation.