2018

SELECTION OF ARTICLES APPEARING IN THE GUNDAROO GAZETTE IN 2018

Contents

May 2018  Keep your cool – on the role of land management in influencing
local climate

March 2018  This is living – on the surprising success of a restoration

August 2018  Bud-banks – the secret of success in a land where the living is not easy


Keep your cool
May 2018

Whether it is “just” another 20 year drought or part of the current warming trend, this autumn has been a sober warning of what is to come: unseasonal heatwaves, downpours of rain and severe drought. I recall reading predictions that these events would intensify as far back as the 1980s. Thirty years later, the populace is still struggling to come to terms with the reality of climate change. Acting on it at a global-scale seems a step too far for our species at the moment.  But beyond ceasing fossil fuel burning to stem CO2 emissions there are additional things we can do to directly influence the local climate. And these are things very much in your control.

A Czech scientist Jan Porkorný has devoted his career to pointing out just how important local landscape management is to keeping the planet cool. I knew Jan when he worked for a few years at CSIRO in the early 80s.  Later I visited the Institute of Landscape Ecology in Třeboň, stayed in his family’s 700 year old house in Bohemia and saw the amazing cultural landscape of meadows and ponds where the local delicacy, European carp, is raised. It was in this landscape that Jan came to understand the vital role of vegetation and water in keeping the land surface and surrounding air cool. In a recent review Jan summarized what is known about this topic[1]. The mechanisms are complicated, and I am happy to send copies of the paper to anyone interested.

However, the message is simple. Retaining vegetation and rainwater in the landscape, both directly and indirectly, keeps the landscape cool and promotes local rainfall.

Seeing hills bared of all perennial vegetation in our district is very, very scary.  Apart from the well-understood risk of losing soil into the Yass River, bare ground absorbs more radiant heat from the sun. With no plants converting this sunlight into biomass, bare ground instead heats up, creating fluctuating temperature conditions and reducing relative humidity. The greener and wetter the vegetation, the greater the cooling effect. Water evaporates from the plants’ leaves which contributes to cooling and greater moisture. Water begets water it seems. In Western Australia, researchers concluded that the sharp decline in rainfall that has been experienced in the south-west inland was due to vegetation clearance rather then global-scale changes to atmospheric conditions[2].

Returning native perennial grasses, trees and shrubs to our land is a positive move that is within the capacity of most landholders. It has the added benefit of helping our wildlife. Not having houses, air conditioning or a means of diverting more resources for their survival (e.g. no irrigated crops), much of our fauna is going to suffer from the heat and dryness even more than ourselves. More habitat will mean greater survival opportunities. Moreover, we have the know-how and institutions to make serious revegetation little more demanding than a ramping-up of business as usual.

I am not sure what it reveals about our ability to forget the past, but what I am saying here was not news in the 19th century. A Polish immigrant to South Australia, Johann Tepper, wrote an article published in the Agricultural Gazette of New South Wales in 1896 about the role of trees in ameliorating the local climate and promoting rainfall.

His words were are follows:

Even in countries with such deep rich soils, moist and temperate climate, and extremely favourable constitution for continued cropping as central and eastern Europe, it is considered by those who have studied the whole question that one-third of the area should be kept under forest or heath vegetation; for the drier parts of Australia one-half would not be too much.

I am not sure that our landscape can be left exposed and vulnerable, and stay as productive as it currently is, if we ignore the warnings for another 100 years.
Time to act.

[1] Huryna, H. & Porkorný, J. (2016) The role of water and vegetation in the distribution of solar energy and local climate: a review. Folia Geobotanica, 51, 191-208.

[2] Andrich, M.A. & Imberger, J. (2013). The effect of land clearing on rainfall and fresh water resources in Western Australia: a multi-functional sustainability analysis. International Journal of Sustainable Development and World Ecology, 20, 549-63.


This is living
March 2018

After a rather pleasant wet spell in December the moisture in our landscape started to shrink down to the low lying areas, and it would appear that many of the birds did as well.  In late January there appeared birds in such profusion and variety around Lake Kevin that it was dizzying.  The combination of water, greener grass and the flowering of the nearby Yellow Box combined to be irresistibly attractive to birds.  On the water a Wood Duck pair and their brood of eight drifted about, being dodged by water-skimming Tree Martins.  Sacred Kingfishers zoomed here and there, while Dusky Wood-swallows swooped on airborne insects for their hungry offspring.  A large dead tree provided convenient parking for these birds, together with assorted Galahs, Noisy Friarbirds, and Varied Sittellas.  The surrounding bushes were aquiver with numerous bush birds: Spotted Pardalote, Willie Wagtail, Speckled Warbler, Red-Browed Firetail, Yellow-rumped Thornbill, Eastern Spinebill, Superb Fairy-wren (aka Blue Wren), Brown Thornbill, White-throated Tree Creeper and Buff-rumped Thornbill.

The spectacle of these cheery creatures was even sweeter with the thought that they were enjoying themselves in the location that was the most degraded part of the property a decade ago.  I was even more impressed that some of the birds were species that were rarely seen anywhere on Gang Gang in the past, but now have moved in permanently (Blue Wren, Willie Wagtail).  Others which has had been seen overhead previously were now finally gracing us with their perching presence (Dusky Woodswallow, Tree Martin).  The finches were especially exciting to have as this was the first time they had stayed for more than a fleeting visit.  And the Speckled Warblers are always special, being a particularly handsome species struggling to survive.  Foxes eat most of their offspring, owing to the bird’s unfortunate habit of nesting on the ground.

Twelve years ago, this area featured an ugly concrete flume, undermined by gullying. It sat in a hectare of scalded, eroded soil and gullies, parts of it salt affected. Past owners had works done ten years previously (contour banks, the flume, fencing) but it had all fallen apart, whether by poor management or bad luck. On advice, we decided to inter the failed infrastructure under a dam wall. This is when Kevin came on the scene. As you might expect, I am not a fan of the damage that bulldozers can do to vegetation, but Kevin did some spectacularly good earthworks and constructed a beautiful dam (which we named after him). It was now up to Jon and me to revegetate the wall and surrounding salty, eroded area.

Ten years from the time of this photo, the gully had been replaced by high quality bird habitat.

We did a little bit of planting, some scattering of seed collected from elsewhere on Gang Gang, and added grass clippings and prunings to the most scorched spots. Other plants just found their way. This was one of the few sites where I have not been fussed about weed removal. Almost anything that could grow was welcome here.

After ten years, there are small eucalypts, lots of wattles, some dense bottlebrushes and Sweet Bursaria. The ground is a mosaic of bare ground and grass – the ground feeders seem to prefer a measure of bare soil as it enables them to move freely and keep an eye out for danger. Flowering occurs throughout the year now, which contributes to insect numbers (as does the dam) and wattle seed is relished by the parrots. Gang Gangs now linger longer on Gang Gang thanks to this new food source. As far as the birds (and ourselves) are concerned, this is living.

Lake Kevin ten years after the first photo, taken from approximately the same point.

 


Bud-banks: the secret of success in a land where the living is not easy
August 2018

When the frosts of winter combine with the added insult of drought, living in the bush on the southern tablelands can be a dispiriting time. This is especially the case when one considers the ground layer vegetation. The summer-growing grasses shrivel to grey, the ground cover is nibbled to an ever more ground-hugging profile, and there are no flowers to speak of.

This dreary, relatively lifeless prospect can persist for years, but as soon as the soil profile is wetted up again the wildflowers spring forth, their splashes of bright colour reminding us once again why we love living in this muted, but beautiful landscape

It’s seeds” – you might think. Everybody knows that seeds can lie dormant in the soil for years, waiting for the right conditions to bring plant life back to the surface. But native plants have been around a long time and seem to have concluded that relying on seeds is not the most successful strategy for undisturbed, nutrient-poor soils in a land where drought prevails much of the time. Instead they bank on a supply of dormant buds and a store of food.

The natives have voted with their roots, so to speak. While they may produce some seed, they mainly invest in deep roots and food storage. Substantial amounts of food may be stowed away in corms, tubers or rhizomes.

Of the 180-odd species of native herbaceous plants that live at Gang Gang, only 27 (15%) are annuals that rely entirely on seeds to grow from year to year. The great majority are perennials that are capable of surviving the hard times by going dormant. This involves withdrawing nutrients and sugars from the leaves to the storage organs. The leaves shrivel up and the plant shuts down until conditions suitable for growth return, and dormant buds reactivate.

While brooding under the ground, the plants have various means of protecting themselves from drying out and they use a small amount of energy to stay alive. The amount of energy used, and the amount stored, determines how long they can stay dormant. In the case of orchids, this can be for years.

Above: Over 70% of the exotic plants on Gang Gang are annuals. The entire plant dies after the seeds mature and seeds are the only means of regeneration. Note the lack of investment in root mass vs the shoots.

Above:  These native Yam Daisies have diverted all the energy collected during the winter to the fleshy underground ‘yams’. Note the shrivelled leaves. The well-provisioned summer-dormant buds will reshoot if there is moisture around next autumn.

The main difference between the two life histories is that germinated seedlings are reliant on sustained moist conditions to establish and have only one shot at adulthood. A Yam Daisy can put out some tentative leaves, replenish the stores as much as possible, but close down shop again if things go bad. Obviously both strategies have their advantages, but the proportion of perennials among Australian native herbs attests to an evolutionary history of low nutrients and stressful growing conditions. The exotic annuals are the new kids on the block, adapted to more nutrients and more disturbance. No one knows which strategy will result in greater success when faced with the combined effects of global warming and land use change. Only time will tell.