Extension Hill Iron Mine

December 12

The purpose of my trip to the Mt. Gibson area is to lend a hand with some conservation work. Extension hill is a large ironstone mountain that is going to be mined for hematite and magnetite. The mining will effectively eliminate Extension Hill and replace it with a large, deep open pit. A waste rock dump will be created on part of the flat land at the base of the hill. This will cover 2 square miles of land under 130 feet of rock. The mining agreement between the government and the mining company stipulates there must be environmental mitigation. This includes the specific requirements that they create a new hill, adjacent to the one they are removing, that will be restored with the native floral communities that are currently found on Extension Hill. They must also restore populations of two rare plants that are only found on a few ironstone mountains that include Extension Hill. One of these species (a Darwinia) is
only found in one other place, the hill adjacent to Extension Hill, and there is some evidence its seeds are dispersed by ants. The plant can establish itself and grow right on exposed layers of iron stone, as you can see in the picture.

The botanist from Kings Park, Ben Miller, wanted me to help him see if ants are in fact moving the seeds of this plant. Anything else we could discover would also be helpful. Considering I could only spend a few days working on this problem, it would be good to discover anything useful.

Fortunately the Darwinia can be propagated from cuttings. The park has some of these cuttings growing in their greenhouses in Perth and they are trying to figure out how to grow plants from seeds. Many, many plants in Western Australia are adapted to the fires that have naturally occurred here in the past. This means many plants have evolved adaptations where seeds can only begin their transformation from a viable seed into a new plant when they are stimulated by a fire. This may mean they need to be heated while they are in the soil bank. It can also be that the seeds are held on structures on a plant that only allow the seeds to be released when the plant experiences the high temperatures associated with a fire. The seeds of the Darwinia do fall from the plant after the seed is set but there are some conditions associated with fire that are necessary to initiate the seeds to grow. What those conditions are remains to be worked out.

The part the ants play in this story are their ability to move the seeds and to potentially place them in a location that is favorable for their germination. Amazingly enough we were able to find an ant that was moving the seeds. The species is very similar to the ant that Maria and I were studying on the sand plains of North Eneabba. Our few days of work revealed only the barest beginnings regarding the details of the interactions between the plants, the seeds, and the ants but it was a good start. I thought it was quite likely we would not be able to find out anything during my visit to Extension Hill. Chance does favor the prepared but having some luck (the weather cooperated, we found seeds around the nest entrances of the ants, etc.) never hurts either.