Eucalyptus falcata I often see fallen trees as I travel around the wheatbelt. I think that trees are falling much faster than others are growing to develop critical nesting and refuges for our native birds and animals. Wind blowing from cleared land is stronger than uncleared forests, and trees endure more stress events now due to increased heat and reduced rainfall.
I recently discovered a large Silver Mallet Eucalyptus falcata, which had blown over to reveal its amazing root system. In this district Silver Mallets occur on our oldest land surfaces-shallow ironstone remnants of ancient upland mesas. I usually find them in reserves on the highest points of lateritic upland boundaries surrounding river catchments.
I recently discovered a large Silver Mallet Eucalyptus falcata, which had blown over to reveal its amazing root system. In this district Silver Mallets occur on our oldest land surfaces-shallow ironstone remnants of ancient upland mesas. I usually find them in reserves on the highest points of lateritic upland boundaries surrounding river catchments.
Eucalptus falcata grove on remnant ironstone plateau and surrounded by kwongan shrubs and wandoo-Jam woodland
The fallen 20 metre high beauty had been supported by a six metre diameter plate of dense roots and very long feeder roots that snaked out from the central plate. All of this was in about 40 centimetres of gravelly loamy sand soil over a dense ironstone pavement
Six metre root disk supported this twenty metre high Silver Mallet
The root disk comprised a dense mat of roots. Long straggly roots extended out from the disk
A closer look at the underside of the root disk revealed that it was mainly a dense mat of shallow feeder root. Round spots in the mat were thin sinker roots, which had managed to penetrate cracks in the ironstone layer
No central tap root
Almost impentrable ironstone layer below the root disk
Dimorphic root system Most trees and shrubs have a dimorphic root system, which has a taproot, which grows straight down to the water table, from which it obtains water for the plant; and a system of lateral roots, which obtain nutrients from superficial soil layers near the surface.The image of a dried root of a young tree that was probably killed by fire displays these features.
Proteaceae plants such as banksias and hakeas have dimorphic root systems, but they rarely occur in adult eucalypts.
Proteaceae plants such as banksias and hakeas have dimorphic root systems, but they rarely occur in adult eucalypts.
After studying root systems of fallen eucalypts I discovered that most have minor tap roots, usually several small sinker roots below a ring of feeder roots. This makes sense because our ancient soils often have shallow topsoils over hostile subsoils.
There are a couple of great examples on the Breakaway Walk in Foxes Lair, which have fallen over but remained alive with side branches taking over the function of the main stem.
There are a couple of great examples on the Breakaway Walk in Foxes Lair, which have fallen over but remained alive with side branches taking over the function of the main stem.
Fallen Brown Mallet on shallow ironstone
Fallen 10 metre Wandoo on gravel soil The mallee region of wheatbelt WA is characterised by a subdued landscape of mallee woodland on hard setting duplex soils. Recent research has shown that many eucalypts have root systems that create a layer of dense clay subsoil to exclude other plants. Young mallees initially have a tap root like other eucalypts that develops into a woody lignotuber ('mallee root'). Lateral roots generate a hard clay barrier layer and sinker roots extending down through it water holding clay below. Over hundreds of years the taproot/lignotuber rots to allow water to rapidly flow into the soil and a lateral sinker root network, which pumps soil water up and down the soil profile. After rain these roots move water below the clay barrier to deny competing plants and store it. In summer the network pumps water back up for the mallee's use. Amazing!
For an interesting description of tree root systems, read this web page.
Shallow root systems are certainly not limited to Australia. As with Australian trees, tap roots are inhibited by hostile subsoils, some for other reasons such as pines on permafrost.
Shallow root systems are certainly not limited to Australia. As with Australian trees, tap roots are inhibited by hostile subsoils, some for other reasons such as pines on permafrost.