​Greetings fellow Foxies,
These hollow ironstone pipes are exposed in a gravel pit on private property south-east of Quairading. The pipes start about 2 metres below the surface and continue into the gravelly clay base of the pit. Equally amazing is that this is an ancient sand deposit on a ridge overlying granite/dolerite bedrock.
This raises some questions
·         How did a sand dune form on a ridge in the wheatbelt?
·         How did the sand turn into gravel and what causes the ironstone pipes?

​A clue to the sand deposit lies in the large salt lake chain (The “Salt River”) to the west of the gravel pit. Millions of years ago this was a mighty river that flowed to the Helena River in Perth. Gradually the river was blocked as the Darling Range was uplifted, causing the river to back up (forming a lake?) until it was diverted north in its present course as the south branch of the Avon River. The climate was also gradually changing and becoming more variable with alternating wet and dry cycles, particularly in the last hundred thousand years. During extended droughts strong winds blew sand from the dry river/lake beds to form aeolian sand deposits (that often have Banksia prionotes and Xylomelum angustifolium vegetation today ).
We know that these are aeolian deposits because of the uniform sand grain size.

​A clue to the gravel formation is the vegetation at the top of the pit face, which comprises Allocasuarina campestris (a tamma) and a grevillea species that are remnants of recent native vegetation.
This blog  describes how these plants and associated bacteria create lateritic soils.
This spot is more complicated than most in being an old sand deposit over reddish clay formed from dolerite. My guess is that deep plant roots transported iron and aluminium up from depth up to the subsoil where it was converted into gravels, and deposited around the root channels to form the ironstone pipes. The loose sandy gravel flowed away from the pipes when the pit was excavated.
 Despite being tough rocks, on close examination the pipes are just fine sand that has been cemented together by aluminium (white) and iron (yellow/orange/red) oxides and silica (not obvious).

A hemiparasitic plant steals water and minerals from their hosts but still use green chlorophyll in their leaves to produce energy.
Holoparasites derive all their energy from their hosts without killing them. Plant examples include dodder laurel and orabanche, and there are many animal parasites such as ticks and fleas.
The animal world also has parasitoids, such as wasps whose larvae kill their hosts.​
Mistletoes are hemiparasites, which grow on eucalypt and acacia branches, but most hemiparasites feed from their host's roots.
The beautiful Christmas tree Nuytsia floribunda is the largest root hemiparasitise, and has special organs on their roots called haustoria to tap into the sap of host plants. In the 1960’s they caused short circuits in underground power cables until resistant cables were developed.
Sandalwood and quandongs are Santalum genus hemiparasites, which prefer acacias.

Western quandong Santalum acuminatum is a small tree that produces edible nuts covered by a red vitamin C-rich rind that makes wonderful jam. In Foxes Lair it occurs as clumps of small shrubs that have never fruited in the last twenty years. I think that the clumps are clones of a single plant, which have spread from underground root shoots.

​Australian Sandalwood Santalum spicatum has been planted at the Range Road car park with their jam acacia hosts. They have tasty nuts like macadamias.

Weeping, narrow-leaved bitter quandong, Santalum murryanum occurs on lateritic soils. It  has inedible fruit.
Olax and quandongs have bell-shaped root haustoria that attach to the host root and drill into it to connect to the water bearing vessels. ​

​Olax benthamiana is another hemiparasite flowering now on gravelly soils, which became more common after the 2009 fire. It is adapted to germinate with its acacia and melaleuca shrub hosts. Its flowers have a strong sweet smell which attracts insect pollinators

Most hemiparasites produce nuts or fruit (drupes) that are spread by passing through animals (e.g) emus woylies and birds, some of which are now extinct in most reserves. This has reduced the ability of quandong and sandalwood to spread. There has been a huge regeneration of bitter quandong seedlings after a 2009 fire. As there are far more plants that can be supported by their hosts; the stand has to thin out.

Native currants (Leptomeria species) tend to occur in relatively bare areas under eucalypts, which they must be parasitising.
They are very obvious in late spring and summer, with their almost glowing light green soft looking foliage. See them under the salmon gums near the Brockway tree at Yilliminning Rock. The tiny bush tucker 'currants' are very high in vitamin C.