Brisbane Rainforest Action & Information Network

The Thinking Bush Regenerator

A new way of approaching bush regeneration

(From an article by Judie Rawling in the Urban Bushland Management newsletter March '96. This article refers to bush regeneration undertaken in NSW).

The problem: a typical urban reserve, degraded in parts, criss-crossed with tracks, dumping on the edges, often a creek line cutting through the bush. The native plant community has become infested with a variety of herbaceous and woody weeds with a consequent loss of species diversity, loss of habitat value presenting to the neighbours as generally not a very nice place to be.

The traditional solution: call in the bush regenerators! Bush regeneration is typically a slow meticulous process whereby unwanted exotics and alien native species are removed in extended stages to encourage the growth of native plants. Often bush regeneration projects include a general "clean-up" along the edges, perhaps a bit of creek bank stabilisation and some replanting in badly degraded areas.

Primary weed control the first time through is followed by secondary weeding which may take place once or many times, depending on the degree of weed growth. This phase may, and often does, extend over many years. The bush regenerators return time and time again to remove weeds from the work site - trying to keep the area squeaky clean and free from weeds.

Follow-up weeding is vital to the success of any bush regeneration programme - no-one could possibly argue with that, and this is the one phase of the programme which is often ignored by unskilled or inexperienced bush workers. It is also the phase which costs the client a great deal of money - but forms the mainstay of the bush regenerators wage packet.

The Quandary - traditional practices or new approach? I am asking you all to think about whether we really need to be quite so meticulous in our follow-up weeding. By rushing in to pull out the first flush of weeds that follow a primary clearing, and by continually picking over the site, are we actually doing harm?

No don't panic and rush off to the telephone to spread the word that Judie says we canít do follow-up any more. I didn't say we are doing harm or that we should knock off the follow-up, I just asked you to think objectively about a few of the issues. Let me explain.

A hypothetical site: Typically we have an area of Lantana and Privet - underneath, say, is Asparagus and a bit of Wandering Jew. We remove the woody weeds, deal with the weedy ground covers. The site looks pretty bare - much like a bomb has gone off - oh dear, have we over cleared?

If it's summer, after a few weeks the site is covered with the pioneer weeds - Fleabane, Paddy's Lucerne, Tobacco and so on, maybe a bit of Lantana regrowth. The natural instinct is to get in there and wipe the weeds out - dig, yank and spray.

Where does this get us? A nice bare soil site once again - boy, does it look neat. Maybe we have been lucky and there are some native pioneer species poking their cotyledons out - a bit of Trema maybe or Omalanthus or Sigesbeckia, a few wisps of Entolasia. This isn't the usual situation - there isn't usually much in the way of native regrowth in the first few months. Natives, even the pioneers, tend to be slower to germinate than the exotics (it's one of life's mysteries!)

Making beds: A month or so later, here we all are again. All that nice bare soil is covered with tall messy looking herbaceous weeds - they really stick out as weeds don't they? But, if we have done our job well in the first place, there should be very few woody weeds this time, especially if we have used our common sense and removed the Privet and Lantana before the year's crop of berries is ripe. This is called making your knowledge of the weeds life cycle work for you, and making your life easier.

What do we do, go in and dig, rip and spray all over again, and again, and again? Good for the purse but not so good for the bush. This is why.

Succession - re-establishing a healthy ecosystem: On a newly bared site a whole host of physical and chemical factors come into play which determine which species germinate and which will survive. Some of the pioneer species taking advantage of the new housing estate will be exotics, some natives - generally they have a weedy habit i.e. they arrive uninvited in large numbers and overstay their welcome.

However, many of the long-lived native species are slow to germinate. They pop up happily only in the protective umbrella provided by other quick growing and often taller plants (the herbaceous weeds that look messy) - and remember, they aren't fussy about what is going to provide that protection, exotics or natives.

If we go in right away and start ripping out this protective umbrella, we remove that shading factor which blocks the high radiation and reduces the temperature of the soil surface. We remove the soil moisture, in fact, we remove the protective micro-habitat. Any small seedlings struggling to establish come in for a real shock - high radiation, drying winds and possible invasion by other, more competitive weeds, which jump into the open niche, thoughtfully provided by the bush regenerators.

Also, remember that if we pull out a large Fleabane or a Bidens, other plants may come up in the clod of earth - barely germinated native seedlings possibly - and the soil is turned over once again. Some of these seedlings are too small to be seen clearly - barely germinated - but they are usually there or they were!

If we go in and spot-spray, what else do we inadvertently hit? And how about the trampling of a bunch of bush regenerators traipsing through the site? Is it worth the risk?

No, I'm not talking about leaving gross competitors like Tobacco, Lantana, Privet or Tradescantia to argue with the native seedlings: but I am talking about the perceived necessity to remove any and all non-native growth on a regular basis. In fact, returning week after week, month after month to the same site to disrupt the newly establishing plant community is only counter productive.

What does observation made over the last eight years (in severely degraded sites where primary weed clearance had removed virtually all the understorey vegetation)? That leaving the site to rest, to recover its equilibrium and to re-order the soil nutrient and moisture balance, may be the best thing for the bush in the long run.

Where cover crops have been used to provide this bit of cover for new plants, the situation is much the same. Several years ago two badly degraded sites were treated in this way, using a cover crop to provide a protective blanket around new plantings. The natives were powering along in their sheltered locations. The contractors who followed us in to these sites removed all the cover crop and made the site look neat once again. The result - massive invasion of Ehrharta (Veldgrass) and other smothering weeds - the loss of many of the new native plants - but on-going work for the bush regenerating team. Who benefited, the regenerators or the bush?

Sure, the herbaceous weeds may provide a bit of competition for the natives, but the benefits they offer far outweigh the negative aspects. The natives germinate in amongst the weeds and the weeds are rampant ground covers (e.g. Tradescantia, vines or Kikuyu) they generally do very well under it all. In fact, after twelve months or less, the natives will over-top the weeds and you can safely go in and weed around them.

Remember too, that the natives will germinate and establish progressively, so that Cassinia, Cheese Tree, Acacia etc. will join the pioneer natives mentioned above, as time goes on. If you have been lucky, you may even get Eucalypts and Angophoras - but this won't happen unless the fresh seed arrived on the bare soil site immediately after it was cleared (as your clearing stimulated the conditions provided by a fire).

So, I pose the question - does bush regeneration need to be such a long-drawn process? Do our traditional techniques (and most important, the established practice of carrying out continual maintenance weeding on a recovering site) stretch out the process unnecessarily?

Should we perhaps do our work in blocks: first doing primary removal over a set areas, then allowing the site to rest for 3 or 6 months before doing any further work? Be sure to look in on it from time to time, by all means pop in and eradicate a few real "nasties", but generally leave the site to recover by itself.
Work, rest and re-evaluate.

Judie Rawling