Why scattered paddock trees are important
Scattered paddock trees are an important part of the landscape and play a number of roles on a healthy and productive farm.
About one third of agricultural land in the Australian temperate zone contains scattered paddock trees.
Most of these trees are very old and there are often insufficient young trees growing to take their place, including some over cleared species such as White Box and Yellow Box.
Even dead and unhealthy scattered paddock trees are important as they provide homes and shelter for wildlife. The big concern is that in 40 years all of these paddock trees could be gone.
Benefits for your farm
Scattered paddock trees provide a range of benefits for productivity including:
- Pest control - Bats and birds that roost in trees can significantly reduce the number of insect pests
- Shade and shelter for livestock - Protection from sun and wind reduces heat and cold stress. This allows stock to thermoregulate more efficiently and optimise food metabolism.
- Shelter for crops and pasture - Trees give protection from the wind and extreme temperatures improving localised growth.
- Salinity management - Trees can improve waterlogging and dryland salinity problems.
- Improved soil structure - Wind and water erosion is reduced with remnant vegetation.
- Better quality soil - Soil fertility improves as leaf litter and animal droppings break down, returning nutrients to deep soil beyond the reach of the pasture root zone.
- Natural regeneration - Mature trees provide the seeds to grow young trees and create the right conditions to grow native grasses and shrubs.
- Pollinators - Increase in the abundance and diversity of insect pollinators. Also valuable for bee products including honey and beeswax.
- Carbon storage – large, older paddock trees store more carbon than smaller trees. This can help improve long-term carbon storage and benefit on-farm carbon accounting.
Benefits for wildlife
Scattered paddock trees also provide an important function for our wildlife including:
- Biodiversity links - Prevent fragmentation of landscapes by providing a connection between larger patches of native vegetation.
- Habitat hollows – Tree hollows can take a century to form, and provide habitat for many birds, small mammals, micro bats, reptiles, frogs, insects and spiders.
- Micro-habitats – Natural crevices and loose bark on old paddock trees, and fallen limbs, provide habitat for small mammals and reptiles.
- Food source – Old trees provide a variety of food sources for native fauna including nectar, seed, pollen, and insects.
- Source of seed - Paddock trees can aid natural regeneration and provide a source of local seeds for collection, storage and propagation.
Shade and shelter
Read transcriptScattered paddock trees for hollows
Scattered paddock trees are important because they often contain hollows or are of hollow forming age. Since it takes at least 60 to 80 years for hollows to develop, we need to conserve mature trees to ensure the survival of animals and plants that depend on them, until replacements have grown. Some trees, such as red gums need over 100 years to develop hollows.
Planted trees do not replace the established trees until they have formed the full range of tree hollows, cracks and loose bark needed for wildlife. If we keep our scattered paddock trees in good condition then we can pass on a valuable natural resource to the next generation of land holders.
In many instances, scattered paddock trees are the only remaining trees of highly cleared vegetation communities, for example grassy box woodlands.
Eucalypts are the most important trees in the catchment when it comes to providing homes and food for a range of animals.
But not all eucalypts are equal as the size, age and type of tree can make a big difference to the shelter that is available for animals. For example:
- Most eucalypt trees that have a diameter of more than 60cm have medium and large tree hollows
- The best hollows are found in the various species of box tree and River Red Gums
- Eucalypts are the home of choice for many unique species including a variety of insects, spiders and other invertebrates
- In box and ironbark forests 61% of mammal species and 20% of bird species depend on hollows
- Some threatened bird species rely on particular eucalypt species for nesting and food.
Non-eucalypts are also important because they contain small tree hollows and bark that create shelter for smaller animals.
Cracks and crevices for wildlife
There are a number of trees that do not form many hollows such as the Cypress Pine, Myall, Leopardwood, Bulloke and Red Stringybark. These tree species do provide cracks and crevices that are habitat for small mammals and reptiles.
Cracks and crevices provide food and shelter from predators. They also provide protection from extreme temperatures for many animals.
For example, Casuarinas such as Belah and Bullokes are important because they provide food and shelter for Glossy Black Cockatoos, which are listed as threatened species. Cracks and crevices also provide habitat and food for the following:
- 400 Australian vertebrate species (100 threatened or near-threatened species)
- 66% of bats
- 31% of tree dwelling mammals
- 15% of land birds
- 13% of all frogs
- 10% of all reptiles.
Food and nesting sites for wildlife
Honeyeaters, sugar gliders and many other animals depend on nectar and pollen. Some birds follow the flowering trees as they blossom. Not all eucalypt trees flower at the same time, so the birds need to have a variety of tree types across the landscape to get nectar throughout the year. For example, Blue-leaved Ironbarks flower in winter and Narrow-leafed Ironbarks in spring. Together they provide a reliable food supply.
Leaf eating animals like koalas, possums and gliders need a range of trees to choose from because not every tree has good food. For example, some gum leaves cannot be eaten because they are too toxic and not as nutritious as the leaves found on other trees.
Large habitat trees are a haven for invertebrates such as insects and spiders. Many birds and reptiles collect food from under the bark, on leaves, around flowers and amongst the debris that falls under the trees.
Even small trees can be the home for nests of large birds such as wedge-tailed eagles.
Loss of scattered paddock trees
Even in big patches of native vegetation the number of large trees (or habitat trees) has been reduced to one tenth of the original density. With lack of regeneration of these trees over the past 200 years, there are few medium to large trees to take their place.
In addition to loss, many paddock tree areas are affected by dieback. This is the long drawn out decline in a tree's health. It starts with the ongoing dying back of the tips of twigs, branches or tops of trees and with constant and repeated stress the tree eventually dies.
Learn about some of the threats to scattered paddock trees.
Many large trees are approaching the end of their lifespan and there are no replacement trees. This is happening more quickly as a result of routine agricultural practices.
Stressed trees are in more danger of being attacked by Christmas beetles, leaf miners, sawfly larvae, lerps and scale insects.
Stressed trees are at more risk of heavy infestation by mistletoe.
Hollows make established trees more susceptible to being burnt out as flames can funnel up the internal hollows and still be burning sometimes weeks later.
This frequently leads to the death of paddock trees.
Paddock trees are still being removed for fence replacement and access for wider machinery.
Surface roots are damaged if cultivation takes place too close to the tree. This can make it difficult for the tree to get enough water and nutrients and increases the chance of fungus and insect attack.
Fertilisers change soil nutrient levels. Increased nutrient loads from fertilisers and stock camps making the trees more susceptible to insect attack and drought stress
Knockdown herbicides and non-lethal levels of herbicide from drift can slowly kill mature trees. Spray drift can also weaken paddock trees, inviting insect attack and rot.
Dominance of exotic pasture grasses (like phalaris) affects the tree's chances of survival. Some exotic grasses can take the tree's moisture and inhibit the seedling regrowth.
The loss of ground cover from stock causes soil compaction and degradation, erosion and a change in soil fertility from the buildup of manure. Stock can also ringbark rough-barked trees such as stringybark, peppermint and box trees as well as kill seedlings.
Assess the condition of your paddock trees
Use the following checklist to gauge the health of bushland and paddock trees on your property.
- Paddock shade trees and stock camps are fenced (or not used for long periods by stock).
- There is no evidence of ringbarking by stock or rubbing on trunks.
- There are young trees coming along to replace aging trees.
- There are fewer than 20% of paddock trees at Stage 4 of dieback.
- There are fewer than 20% of paddock trees at Stage 3 of dieback.
- There are less than 20% of trees at Stage 2 of dieback.
- There are fewer than 20% of paddock trees at Stage 1 of dieback.
- Eucalypt trees have seeds on them.
- There is more than 2sq m of shade in summer per animal in each paddock.
- There is more than 4sq m of shade in summer per animal in each paddock.
Stages of paddock tree die-back
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Protecting scattered paddock trees
Your farm plan should include management of scattered paddock trees.
Some ways to protect scattered paddock trees and limit dieback are:
- Fencing to protect selected trees from stock and routine agricultural practices in the paddock.
- Plant shade trees away from isolated paddock trees for stock.
- Wrap wire netting around trees that are being ringbarked by stock.
- Do not apply fertilizer in the root zone of the tree.
- Reduce herbicide spray drift as much as possible.
- Don't burn logs, stumps, or fallen branches. If they are in an inconvenient place, move logs to a more appropriate remnant vegetation area or creek as wildlife habitat.
Ways to help natural regeneration to take place:
- use temporary fencing and enclose an area twice the size of the tree canopy to encourage regeneration
- manage grazing to help young plants survive
- control herbivores such as rabbits, hares, goats and kangaroos.
Mistletoe
Mistletoes are natural parasites of trees and shrubs. There are many varieties of native mistletoe and each one generally has a type of host tree or shrub that they prefer. Many host plants can carry a few mistletoes and survive but if the host plant has a severe infestation then the mistletoe can kill the tree or stunt its growth. When the ecosystem is out of balance, mistletoes are more likely to infest trees and speed up their death.
Mistletoes are important food sources for many native animals that play a role in controlling the plant. In areas where the animals no longer naturally control the mistletoe, the excess is best managed by pruning and pollarding. Long term control requires landscape restoration and revegetation.
Paddock tree protection success stories
Catherine Bennett has been working to improve landscape connectivity and biodiversity across her sheep and cattle property 7 km north of Cowra.
Over the past 12 years Catherine has installed 23 biodiversity clusters around the base of existing paddock trees. She has used a unique method of fencing in which fence posts are installed on an angle and strained using wire forming a 25m diameter circle around mature hollow bearing trees. The fence is installed without the need for any strainer posts and is done in a way in which the shade is still available for her stock.
Within the circle she plants a mix of native shrubs and trees which will form an island of biodiversity within the landscape. The planted vegetation helps with soil microbial activity and develops a mycelial mat underneath the soil. She has noticed that the health of the old growth trees improves once they have the circle around them.
Tree circles for property health: An innovative tool to improve habitat and drought resilience
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