Monday, 29 October 2007

The Mathematics of Bushland Management

Just me in the bushland today - but surrounded by painted ladies it seems - dug them out and (carefully) removed from the bushland to avoid spreading their little bulbils that break off from the main bulb.

As I had plenty of time to contemplate things, I pondered on the mathematics of bushland management, specifically, what is going to happen as the number of Geraldton Carnation Weeds declines? Big patches of weeds are easy to find. Individual GCW plants are quite a challenge to find - they are typically only a few centimetres tall, often surrounded by grass, and not really visible until they are advanced enough to flower or produce seeds.

At present we approach the challenge of weed control by working around the edges of infestations, trying to find the boundary, and working towards the centre. So, we are always searching for that individual plant on the outer edge of the infestation. And, I am sure we miss many of these outliers, so the edges of infestations become more and more diffuse and difficult to define.

This strategy is only as good as our ability to find those outliers. If we miss the outliers, and they then go to seed, then we will have an even bigger problem next year - and GCW has seeds that may last up to 7 years in the soil.

Our response to this problem is to visit the same area several times during the season. This increases the likelihood of picking up the outliers, especially as the plants become more visible as they mature. The problem of course is that this puts heavy demands on our time - reducing our capacity to focus on other weeds.

Any suggestions on how to deal with this? Suggestions welcome.

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Saturday, 27 October 2007

Proposed Bush to Beach Walk for Walk Week (11th November)

Walk notes prepared by Daniel Boase-Jelinek, Friends of Shenton Bushland Inc

Shenton Bushland is a time-capsule that tells us a little of what this area used to look like before European settlement 200 years ago, and also how the natural ecosystem of this bushland has evolved and adapted to the changes that have occurred as a result of that settlement.

Looking east from the Shenton Park train station notice that we are high up on a remnant sand-dune.

A geological cross section from the City to the ocean reveals that there are a series of these dunes. Each dune sits on top of an elevated ridge of limestone. In the valleys between the dunes are wetlands such as Lake Jualbup, Lake Claremont and Perry Lakes.

The original vegetation on the dunes is Jarrah Banksia woodlands. Where the limestone comes close to the surface, you will see Tuart and thickets of Dryandra sessilis. Most of the original vegetation around the wetlands has been removed to make way for houses and parks. If you visit Lake Claremont and Perry Lakes you might see some of the original reeds and swamp paperbarks.

This diversity of land forms, and associated vegetation has made it possible for a great variety of insects, birds, reptiles and mammals to inhabit and survive in the area despite the long hot dry summers. Central to this survival is the groundwater that is collected during the winter rains, and then seeps out from the limestone ridges and flows down into the wetlands, ultimately ending up in the river and the ocean. The ground water level rises during winter and causes the wetlands to flood, and declines each summer allowing the wetlands to dry out. The frogs, tortoises and birdlife that inhabit the wetlands in winter have adapted to this cycle. For example, each spring, the frogs leave the wetland and head off up into the bushland, and forage there through summer, before returning to the wetland in autumn to breed. Birds, butterflies, bees and other insects also move to-and-fro with the seasons.

Vegetation linkages provide the routes for these frogs, birds, and insects to move between bushland and wetland as part of their seasonal movement.
Today's walk will commence at Shenton Park train station, and loop through the bushland (following the path marked in blue on this map), returning back to the starting point.

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Entering Shenton Bushland through the car park we notice the big Jarrah and Tuart trees with nesting hollows. It takes many years for trees to develop hollows big enough for birds to use for nesting. During Perth's early settlement there was a lot of logging activities in these bushland areas, and many of the old trees have disappeared.

Walking along the path, looking west into the bushland, we notice that there are few big trees, and most of the vegetation consists of shrubs and ground covers. This reflects the logging, followed by frequent fires that killed off regrowth. It is now ten years since the last fire, and new saplings are beginning to appear. This bushland needs at least another 10 or 20 years without fire to have any chance of getting the big trees back.

The degraded area used to be a rubbish tip for many years. Being on the road to the Brockway Rubbish tip it was cheaper to dump rubbish here than at the tip. Nature has a way of reclaiming these areas, and amid the weeds (which have been sprayed to reduce the fire hazard) there are native plants gradually reclaiming this area.

Native plants compete fiercely with weeds, however, once a patch of bushland has lost much of its over-storey, shrubs, and ground cover, it becomes very vulnerable to weed invasion. Most weeds love fire and bare ground, and will quickly take over an area. Weeds don't contribute food or habitat to birds and insects in the bushland. They don't 'pay taxes', and therefore have a natural advantage over native plants that are continually being attacked and eaten.

Local Councils and Bushland Friends groups try to counter the weed invasion by building the resilience of the existing bushland. They encourage the natural vegetation by reducing fire hazards, spraying weeds, and hand removing where spraying is not practical.

Shenton Bushland has had many uses over the years. Being close to the Karrakatta Barracks and the railway line, it was handy during the Second World War to use as a transfer station for Prisoners of War who were mainly based at Marinup (near Dwellingup), but had to come to Perth for medical and other reasons during their internment. The camp here was a group of tents, as well as a parade ground. Most of this was bulldozed after the camp was closed.

Near the southern boundary of the bushland is the current Karrakatta Barracks.

This area was used as a firing range during the war. It is now used for training Reserves. In the background you might see tents and ablution blocks for the Transport Division that used the Bushland when they needed more room.

Near the top of the ridge, we enter a thicket of Dryandra sessilis, which is a sign that limestone is close to the surface. This thicket is important for small birds that can safely forage for food, safe from larger birds that might hunt them.

This diversity of vegetation is a key for survival of the bushland into the future. Diverse bushland habitats allows a variety of insects, birds, and reptiles to live there, and they all contribute to the ecological processes that keep the bushland alive.

Diversity of bushland habitats is also important for this bushland to survive climate change. There have been many changes in climate during the evolution of this bushland. It has survived those changes in the past because those species that were favoured by the new climate did well, while other species that were not suited to the new climate diminished. Larger bushland areas have more diversity, and thus are more likely to survive climate change. Before European settlement, this was one single bushland stretching hundreds of kilometres along the coast and into the goldfields. Now we have just tiny fragments of bushland left. No-one knows whether these small fragments have enough diversity and resilience to respond to the challenge of climate change.

One of the life forms in the bushland we will not see today are fungi. Fungi are neither plant, nor animal. They live in the soil, invisible to us for most of the year until winter. When the rain comes they put up their fruiting bodies that we recognize as mushrooms and puff balls. They also produce fruiting bodies (such as truffles) underground, that used to be eaten by marsupials. Marsupials were probably an important way for fungi to spread through the bushland. Cats, dogs, and foxes have killed off all the marsupials in this bushland. But the fungi remain, and are vital to the life of the bushland. Without them, there would be no Jarrah or Tuart trees, or many of the shrubs that grow in the bushland because the fungi attach to the roots of these plants and help them gather nutrients from the soil.

Other invisible life forms vital to the bushland are cyano-bacteria. These bacteria cannot survive alone, and need to live in association with a host that can protect them from the hostile world. For example, Zamias form an association with cyano-bacteria by developing special roots that are inhabited by the bacteria. The bacteria use photosynthesis to provide nitrogen to the Zamia in exchange for shelter from a hostile world. Cyano-bacteria are vital to life on earth – over millions of years they were the source of much of the oxygen in our atmosphere. Unfortunately, oxygen is toxic to cyano-bacteria, so they are the victims of their own success. Is this a lesson for human beings?

A question for you to consider: How is your lifestyle impacting on the survival of the plants, insects, fungi, birds, and reptiles of Shenton Bushland?

  • do plants from your garden threaten to invade the bushland?

  • could you plant species in your garden that can enhance the movement of insects, birds, and reptiles during their seasonal migrations?

  • do you use chemicals in your garden that might harm these insects, birds, and reptiles?

  • have you told your local council that you value the work council does in looking after these bushland areas, and that you are happy for your rates to be used for this purpose?

These might seem small things, but they have a big impact on the survival of this bushland!

Sunday, 21 October 2007

Surprises - nice and not so nice!

Gladiolus angustus - (Long tubed painted lady) - a nasty surprise lurking where we didn't expect it.

These plants have lots of bulbils that need to be carefully dug out - otherwise they just get worse each time they are disturbed.

We weren't prepared - will need to come back with trowels and bags.

Moving on we worked on Geraldton Carnation Weeds - still lots of them. This has been a really good year for them, and we need to do a lot more work to make sure we don't have a massive infestation next year.

Also found a few Watsonias - which we dug out - no problems there, just need to keep at them.

Further along we came across 6 Victorian Ti-Tree seedlings that had blown in across the fence from Defence Department land.
A pleasant surprise awaited us further East along the Defence Department land fence - a patch of Dampiera linearis out in bloom! These plants are barely visible for most of the year, and then they come out with this stunning blue and yellow flower!

We feasted our eyes on them, and then moved off to another patch of Geraldton Carnation weeds.

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Monday, 15 October 2007

Snakes alive!

The three of us were transfixed - Brian, myself, and a shiny, black, sleek looking Dugite, which appeared to have just emerged from hibernation, and was no doubt hungry and full of venom!

The Dugite slithered away in a flash amid our nervous laughter, and we resumed our activities pulling geraldton carnation weeds (hopefully the last lot!).

Then we moved to the Watsonia patch where a few were still coming up. Came across what looked like a Banksia grandis seedling - though it could be a B. prionotes - will have to watch it to see (there are no B Grandis adults remaining in the bushland).

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Monday, 8 October 2007

Briefing Vicki - our new bushcare officer

Vicki joined Kim and myself to tour the bushland on Sunday afternoon and discuss management issues.

Points of discussion (see map below):

1. Geraldton Carnation Weed - still lots of plants visible, beginning to go to seed - Friends of Shenton Bushland (FoSB) to continue work in this area (Nedlands to help with Greencorps if possible).

2. Watsonia - a few plants still coming up - FoSB will need to work here also

3. Black flag trial - City of Nedlands need to liaise with Kate to make sure we do not affect Kate's work here.

4. Fire break along Health Department Land - FoSB need to contact Health Department to organise

5. Lachenalia Trial - FoSB and Nedlands need to liaise with Kate about the status of this trial

6. Plantings - Lots of Lupins infesting planting area - good for garden mulch - Dani to come and collect them soon.

7. Barrens - Nedlands needs to spray - FoSB to link up with UWA researcher to make sure project is not affected by spraying

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Monday, 1 October 2007

2007 - Annual Bush to Beach walk

The sun was just breaking through heavy grey clouds as we gathered to set off on our 7th Annual Bush to Beach walk. Our route this year was from Swanbourne Beach to Point Resolution.

Robert Powell provided interpretation along the route of the walk.

Here, right on the coastal dunes at Swanbourne, Robert pointed out the coastal wattles being pruned by salt laden winds coming in off the Ocean.

From Swanbourne we set off up Melon Hill in Allen Park, admiring the enormous restoration effort being put into this coastal reserve. Robert pointed out the magnificent Tuarts on top of the ridge.

Behind the coastal ridge, away from the worst of the salty winds, the vegetation became taller. Here, at Allen Park we looked at the Tuarts, Marri, and Rottnest Island Pines.

The Friends of Allen Park had put in some everlastings beside the cottage where they are based.

We learnt about the importance of native Pellitory plants in the life cycle of the Yellow Admiral Butterflies that travel great distances to visit the bushland each year.
(Photo courtesy of Marg Owen)

We then moved on through the housing development at the former Swanbourne High School site, lamenting the short-sightedness of politicians who sell off such assets and leave future generations with nowhere to send their children to school!

Down the hill from Swanbourne we walked along the edge of Lake Claremont, admiring ducks and other water birds with their chicks.

From there, we crossed through Claremont, and were welcomed to the grounds of the Methodist Ladies College (MLC) by a teacher, Ray Forma, who has given up his Sunday to show us around regeneration work the MLC students were doing along the river.

Ray pointed out the historic buildings on the grounds of MLC.

The view from the top was quite breathtaking.

We then went down the stairs to look at the regeneration work.

This foreshore area was used as a vegetable garden during the Great Depression to help feed students at the college.

After leaving MLC we walked along the river beach to Mrs Herbert's Park for a much anticipated picnic, with refreshments provided by Western Endeavour Rotary Club.

The sun came out as we feasted on home-made muffins. Kerri bought 6 to take home to feed dinner guests that evening!

Rupert noticed the tide was coming in, so it was time to negotiate the shallow rock ledges along the Dalkeith foreshore.

After rounding the headland at Bishop St Reserve we came across the beautiful white beach leading to Point Resolution.

Unfortunately, Government Bureaucracy has failed to protect the public interest here, and wealthy individuals are building their ugly mansions right down to the high tide mark.