Botanic Gardens Trust, Sydney, Australia

A year in the woodland - a seasonal diary

Seasonal conditions in the Conservation Research Woodland at the Australian Botanic Garden, Mount Annan range from very hot and dry in summer, to cool or cold in winter. Showers of rain may occur at any time of year.

To give an idea of seasonal conditions and their effect on the woodland plants, here is a month by month diary kept by scientist Jocelyn Howell, as she took part in fieldwork over the period 2001-2004. Observations were made on days when woodland vegetation plots were being recorded, generally in the middle of the month. Illustrations have been kindly provided by Nancy Rollason.

We begin in March when plant growth is at its best.

March - a major flowering time

It is lush and green after rain nearly every day for two weeks. Pale green developing fruits, weighing down branch ends,  have replaced most of the white Blackthorn flowers that filled the woodland understorey in summer. Their small round flattened  'purse' fruits give the genus name Bursaria, while spinosa warns of spines amongst the leaves. The fragrant white flowers are celebrated only in the more friendly common name  - Sweet Bursaria. (We’re not sure how the 'black' of Blackthorn fits in!).

On the ground, some grasses - not all - are having a flush of flowering in response to the rain. Windmill-like seed heads of Chloris truncata are particularly obvious. Yellow is the most popular colour among other flowers - those of the native herb Hypericum gramineum are orange-yellow (the similar looking but exotic weed St Johns Wort *Hypericum perforatum has finished flowering) while small trees of Acacia implexa have pale cream flowerheads. Scattered amongst the grasses are tiny lemon yellow flowers of different shapes - rounded Oxalis perennans, stars of lilies Tricoryne elatior and Hypoxis hygrometrica; the tiny balls of Calotis lappulacea, the Yellow Burr-daisy, appear in just one spot.

We count at least 50 species of plants flowering, and many are also forming seeds, but the 'lower' plants that can’t 'flower and seed' are also active! The two rockferns respond rapidly to rain with vigorous growth of tiny green fronds - taller and smooth in Cheilanthes sieberi, spreading and scaly in Cheilanthes distans. Pale green lichens grow vigorously on black ironbark trunks, and fungi emerge from soil, wood and litter as toadstools - white, cream, pink, red and pale brown - in a variety of shapes.

As we work, Corellas call in the treetops and occasionally drop bunches of Grey Box, Eucalyptus moluccana, flowers. The Forest Red Gums, Eucalyptus tereticornis, are shedding strips of bark rather than flowers, leaving trunks with beautiful patterns of grey, cream and pale brown. Families of Red-rumped Parrots, reared in hollows in the larger trees, chatter amongst themselves.

Insects are busy and visible after the rain - several species of ant are refurbishing their nest entrances and food supplies. Portuguese Millipedes poke amongst the litter, processionary caterpillars group at the base of Acacia implexa trees ready to sneak up and chew the leaves under cover of darkness, Meadow Argus butterflies flit about, and we notice occasional spittlebugs on Vernonia cinerea daisy plants and the creeping herb Brunoniella australis. But it is the flies that have the numbers - dragonflies, March flies, and biting flies with large green eyes! (2001)

April - seeds are abundant

Cloudiness and changeability marks our April woodland monitoring day, but we finish just before the first drops of rain. The biting 'March flies' know it is April and have moved on, so there were fewer distractions. Flowers are also fewer, after warm dry weather in the previous weeks. Cheilanthes fern fronds that looked so vigorous and green in March are starting to curl on the way to drying out. Some plants of weedy *Verbena bonariensis, Purpletop, have died completely. Thick clumps of Poa labillardierei, known appropriately as 'Tussock', have more dead leaves amongst the green.  Other grasses still have their long curving inflorescences rippling in the wind, particularly Themeda australis, Kangaroo Grass, native Sporobolus creber, Slender Rat’s Tail Grass, and unfortunately, weedy *Paspalum dilatatum.

Seeds, however, are abundant. We collect seed for study from several of the native grasses - three-pronged seeds of Aristida vagans, and long awned seed from Red-leg Grass, Bothriochloa macra. So far we’ve recorded 24 native grass species in our Cumberland Plain Woodland remnant.

We also collect seed from other ground plants  including several small daisies. Many of the 13 native daisy species are localised to only a few spots in the woodland, rather than distributed throughout, so we need to find out how the plants spread. It seems the daisies use a variety of tactics to disperse their seeds. Some have the well-known pappus or tuft of hairs that catches the wind. Other species are ground-hugging rosettes, hardly tall enough to make use of wind. Some of these have sticky seeds that may adhere to visiting insects or small animals passing by.  One species has an oil-rich food body that attracts certain ants - they carry these seeds away to their nests, eat off the food bodies, and discard the seeds in or on the soil, ready to germinate at the next suitable time. Calotis lappulacea has a 'burr' that breaks up into individual seeds after it’s been carried away caught in animal fur.

Purse-like fruits on Blackthorn shrubs Bursaria spinosa are mostly still closed and green - we’ll be interested to see whether they’ve dropped all their seeds by our next visit! (2001)

May/June - woodland shines in autumn-winter sun

Mount Annan didn’t received deluges of rain in early May like other parts of Sydney, but despite this, and long stretches of fine sunny weather, in mid-June the woodland still looks green. Dark brown patches punctuate the green of the shrub layer - these are bunches of open purse-like fruit capsules on branch tips of Bursaria spinosa. When shaken, tiny disc seeds fell with a rattle to the ground.

A film of pale brown hovers above the ground layer plants. It is the spent grass inflorescences - dying back after finishing their seed production efforts. Even lower on the ground, delicate fronds of the fern Cheilanthes sieberi are curling as they dry out, and brown at the tips.

Seed packages of the native windmill grasses, Chloris truncata and Chloris ventricosa, come in two colours, either black or pale brown. Three-awned diaspores (= the units that get dispersed) of wiregrass species, Aristida ramosa and Aristida vagans, are the most tenacious and annoying when using that well-known seed dispersal agent, socks – their pointed callus seems to be the sharpest of all the woodland grasses once it has worked its way through the sock to your skin!

While the majority of grasses seem to be closing down in May and June for winter, new green leaves of Poa labillardierei are emerging from amongst the pale brown packed-down thatch of earlier tussock growth. Also sporting new growth are Geranium homeanum and the fragrant native mint Mentha satureioides amongst the herbs.

In early Autumn there were yellow flowers belonging to lots of different native species. By May and June all the yellow flowers, unfortunately, belong to weedy *Senecio madagascariensis. In May a black and white hoverfly created a mini-breeze while investigating my blue pen tip - searching in vain for a blue or pink flower?

In May we couldn’t ignore the Nephila spiders – Golden Orb Weavers. Their three-dimensional webs - triumphs of engineering spun from shining golden spidersilk - straddled tracks and gaps everywhere we thought of walking. By June there are hardly any to be seen, as insect activities have also scaled down. There is only an occasional Admiral or Wanderer butterfly, and the processionary caterpillars we’d seen in March have defoliated one small Acacia implexa tree almost completely, but left without touching a similar one close beside it. 

Birds are also less obvious in June. In May we’d heard the wingflaps of Crested Pigeons, which sound as if they need a grease and oil change, and seen Galahs grubbing in the ground for grass roots. As we search for and record plants in June, we are not so conscious of  the rich avian symphony  we’d been treated to in May - from melodious Magpies and Butcher Birds, strident Noisy Miners and White Cockatoos, sedate Corellas, mournful Ravens and sweet-sounding Red-Rumped Parrots. (2001)

July - the woodland in winter

Mid-July - the middle of the coldest season - will the Cumberland Plain Woodland at Mount Annan present a bleak scene with plants battened down against the cold?

Quite the contrary, our July day in the woodland is sunny - the sky a deep winter blue of an intensity that inspires paint manufacturers, the plants alive and green after good rain the previous week. It seems to have been a relatively warm winter so far, and some plants had buds.

One of our aims in studying the woodland is to throw some light on what triggers responses of different woodland plants - to learn their biological needs so as to help ensure each species is conserved. There are buds, for example, on Eucalyptus crebra trees, the Narrow-leaved Ironbarks, and the woodland’s one shrub of Myoporum montanum even has a few flowers. Are these responses triggered by longer days after the winter solstice towards the end of June, and consistent every year, or by the warm winter temperatures and only happening this year? What will happen to the flowers if there’s a sudden cold snap with frost? The ironbark flowers will probably survive, but frost could play havoc with the soft-petalled Myoporum flowers.

Occasional grass plants have developed inflorescences - soft upright plumes on Dichelachne micrantha, and pendulous seed heads on the more common Kangaroo Grass, Themeda australis. Our tiny rock ferns, Cheilanthes distans and Cheilanthes sieberi, seem to respond to moisture despite day length and temperature, and fronds are soft and green after the previous week’s rain.

Are the weeds successful because they tolerate harsher conditions and flower for longer periods? The latter may certainly contribute to the success of Fireweed, *Senecio madagascariensis - its yellow daisy flowers are still scattered through the woodland understorey. Perhaps "Winterweed" would be an appropriate name! One or two plants of the bad weed *Nassella neesiana, Chilean Needle Grass, are starting to develop inflorescences. Tiny seedlings of other weeds appear in our plots - *Anagallis arvensis, the Scarlet Pimpernel, and *Hypochaeris radicata, Catsear, are two we find.

Birds are certainly responding to the winter sunshine, or perhaps they sense that warmer weather is on its way. A Corella is checking out the hollow branch end on the tall Eucalyptus tereticornis, Forest Red Gum, near the start of the education trail - one less nest space for the Red-rumped Parrots? Butcher Birds, Magpies, Ravens and White Cockatoos are singing and squawking (respectively), and there seems to be a constant background chatter of small birds, including the "cheeps" of the Grey Fantail and the more melodious three-note call of the Spotted Pardalote. Ravens interrupt their calling for a drink of muddy water at the small dam, where Eastern Froglets, Crinia signifera, are vocal.

It’s a perfect winter’s day to enjoy the woodland - but by 4.30 pm the sun has lost its warmth and a veil of thin white cloud spreads silently across the blue from the west - time to draw the curtain against the night cold already on its way! (2001)

August - wind in the woodland

August turns on some of its infamous wind. Leaves and twigs are blown around, though it is surprising how resistant even quite small branches are to being broken off. By late afternoon it is quite chilly in the shade. However, if you are wondering what winter’s woodland weather will be - it’s not always windy! Our second August monitoring day could hardly have been more pleasant - sunny and calm.
 
The weather also brings considerable variety to the lifestyles of our little Rock Ferns! Cheilanthes fronds that were soft and green in July after rain, this month have turned brown and are curling up - probably a response to dry rather than cold weather, but perhaps to both. Fragrant native mint Mentha satureioides, that also looked green and flourishing a couple of months ago, is now looking sere and yellow.

The native daisy species we are monitoring showed variety too. Vernonia cinerea has died back almost completely, with dead stems and hardly any mature leaves remaining. New leafy shoots are just starting to develop close to the ground. In contrast, small rounded plants of Calotis lappulacea, the Yellow Burr-daisy, has lots of green leaves and still some old seed heads. Among the ground-hugging rosette daisies, Lagenophora gracilis, Solenogyne bellioides and Solenogyne dominii are all developing tiny new leaves, but only Cymbonotus lawsonianus is developing flower buds as well, with the occasional one already opened into a yellow flower. Some older leaves of these rosette daisies have been chewed off quite recently, so winter hasn’t deterred all the grazers.

Weedy *Senecio madagascariensis still shows a scattering of yellow flowers amongst the grassy understorey, but there are also occasional tiny pink flowers of native Geranium homeanum. Colourless flowers low to the ground are harder to see, but quite abundant, their stigmas at the ready to receive pollen - they belonged to the small sedge Carex breviculmis, barely 15-20cm tall, hardly a florist’s favourite, but perhaps providing small but vital winter pollen resources to other organisms in  the woodland.

We see occasional arthropods - a Wanderer butterfly here, a native bee there, occasional spiders - but no flies. Ants are still active, but possibly at reduced speed. A magpie dances near the ant trails sampling them like appetizers! - repeatedly darting towards them, collecting an ant with a 'clack!' of the beak, then stepping back quickly to avoid the attentions of ant relatives.

At the start of the education trail, two Long-billed Corellas are stepping in and out of a hollow branch of the big Eucalyptus tereticornis - their new home? A constant background noise of different calls suggests they are not the only birds busy in the woodland. (2001)

September - no massed flowering

Spring in the woodland isn’t accompanied by mass flowering as in sandstone areas, but several species are responding to the warm spring weather. Indigofera australis shrubs are covered in pink flower sprays, there are occasional yellow Oxalis and pink Geranium flowers (both natives), the first Ajuga flowers and Brunoniella buds. Lomandra multiflora spikes are covered in buds, and amongst our rosette daisies, Cymbonontus lawsonianus is flowering in open areas, while Solenogyne bellioides plants in similar situations are forming buds. Dodonaea viscosa shrubs have already flowered in their inconspicuous way, and seeds are forming inside the striking winged fruits.  

On the creek banks, it is a thrill to find flowers of the rare greenhood orchid, Pterostylis curta. Further up the creek line, a trailing vine of Parsonsia straminea is covered with developing green pods, shaped like vanilla beans. Inside, the still-green seeds are developing their beautiful silky plumes, ready for catching the wind when released.

The woodland burns

September, however is an exciting month in the Cumberland Plain Woodland at Mount Annan in 2001- not only because of spring, but also for the prospect of an ecological fire. Such fires are part of woodland management. The native plant species are adapted to survive fire (provided these are not too frequent),  and many benefit from post-fire conditions ideal for germination - cleared soil fertilised with ash, almost as good as a garden bed!

The appointed day dawns fine and sunny, the team of Mount Annan firefighters don their bright yellow overalls, and in two teams take to the trucks with hoses and all the other equipment. The woodland was doused by substantial rain at the end of August, causing the date to be postponed until Thursday 6 September. Will things go right this time?

After a little time to let the night’s dew evaporate, all seems ready, and the first flames are applied at about 10.30 am. But where is the wind to help the fire along? Not a hint of a breeze - in fact, a near-perfect early spring day, if only one wasn’t trying to have a nice hot bushfire! Everyone is a bit disappointed it doesn’t burn faster and fiercer. The team has to apply drip-torches very persistently to some areas to get them to burn at all!

We watch the way the fire behaves. The flames do gather height and intensity in a few places, but mostly there just isn’t thick enough fuel or strong enough air movement for the fire to really take off. The result is a classical patchy cool burn. After all the organisational effort needed for a planned burn, it’s disappointing that the fire doesn’t quite live up to hopes. But, because of the big unknown - weather - unpredictable outcomes just seem to be an inescapable part of the fire scene! It’s certainly possible to learn from any experimental fire, and in that sense every one can be a success.

The following week we are out in the woodland again doing our monthly monitoring of permanent plots. There aren’t many effects of the fire visible yet - its main impact is the pervasive potent perfume of wet ash! But there are dark grey clouds, occasional lightning and thunder, and heavy, then, nuisance rain. Since then, we’ve heard that grasses and other plants are resprouting in the burnt areas. (2001)

October - woodland recovery

Our mid-October monitoring day is warm and calm, though clouds come over later. Warm enough for reptiles to appear - we see a Bearded Dragon and a Blue-tongued Lizard ambling through unburnt undergrowth. The dragon’s colouring, with yellowish 'beard' against grey body, provides particularly effective camouflage by matching the dried-out understorey colours. We haven’t seen these lizards before here - We hope they are residents rather than unwilling immigrants from elsewhere.

After the September fire, we are keen to see how the woodland plants have responded. We joined three Crested Pigeons in the area blackened by the fire; they are foraging on the  ground, whereas we are checking for a wider variety of plant responses. Grasses do not seem to be flourishing, and in fact local reports suggest that those that resprouted early after the fire may have been grazed back by rabbits. However, we count at least 15 herb species resprouting. Plantago gaudichaudii resprouts are developing buds already, six weeks after the fire, while the trailing pea Desmodium brachypodum is suffering from herbivory. Resprouting plants amass biomass and flower faster than seedlings, giving them an advantage, although grazers are attracted to burnt areas with lots of new growth. 

Interestingly, seedlings of some of these resprouting native species are also appearing in the burnt areas, particularly Dichondra repens, which is common throughout the woodland as a ground-hugging creeper. Its seeds don’t normally germinate easily, and it will be interesting to see whether it is heat or smoke that causes this germination response to fire. Even though Dichondra repens can survive and proliferate vegetatively, germination is needed to start a new generation.

Unfortunately some weeds are taking advantage of the cleared, ash-fertilised burnt areas too - there are lots of tiny seedlings of *Sida rhombifolia, Paddy’s Lucerne, and some of *Cirsium vulgare, Spear Thistle, and *Modiola caroliniana, the Red-flowered Mallow. However, fire may be useful in fighting the most troublesome weed, African Olive. We’ve tagged some young plants that seem to have been killed by the fire, and will keep a watch on them to see whether or not they recover.

The unburnt woodland has a pale brownish hue, largely from dead leaves and old inflorescences of some of the grasses. These not only look dead, but crunch underfoot. Lots of plants die back at this dry time of year, and resprout when conditions are better for growth. There are quite a few varieties on the theme of rootstocks for this purpose – thickened taproots, rhizomes (underground stems), fleshy tubers, corms and bulbs. It is thought that resprouting rootstocks may have developed initially as a response to drought, but now enable such plants to survive fire. Rainfall is lower in western Sydney than on the coast, and underground storage organs are a common characteristic of plants growing in the shale-based soils of the Cumberland Plain; this is reflected in the collective name for Aboriginal people of this area, Dharuk, meaning yam or tuber. 

Occasional new inflorescences have appeared on the grasses, Themeda australis, Bothriochloa macra, Austrodanthonia racemosa, Dichelachne micrantha, and Microlaena stipoides. And some of the herbs are flowering, though not in massed proportions – blue Ajuga australis and mauve Brunoniella australis. On Indigofera australis shrubs, seed pods are developing where sprays of pink flowers were in early September. The tiny sedge Carex breviculmis, noted flowering previously, doesn’t seem to have been so successful in forming seeds.

A long flowering season may be a characteristic that makes some weeds successful, and *Anagallis arvensis, *Hypericum perforatum, *Linum trigynum, *Medicago lupulina and *Verbena bonariensis are certainly quick off the mark with flowers this spring. *Senecio madagascariensis flowers are present too – but then, there have been yellow flowers of this weed in the woodland all through winter (2001).

November - the beginning of the dry

The woodland looks rather dry and tired, but then, it’s at the mercy of the rain - or lack of. Because there’s been so little rain since May, the show of lilies, daisies and other herbs emerging from dormant or semi-dormant rootstocks is very muted; there are some of these, mostly in sheltered, favourable spots, but by no means a mass flowering. We’re hoping our continuing monthly observations and recording will tell us what proportion of plants flower consistently at the same time each year, and what proportion respond opportunistically to prevailing conditions – I suspect the latter will predominate. This has important implications for managing and conserving rare species.

The Cumberland Plain land snail, Meridolum corneovirens, is listed as an endangered species under the Threatened Species Conservation Act. In dry times like this November, these snails find their way down deep in the soil, seeking moisture. The day University of Western Sydney snail expert Stephanie Clarke visited we found none on the surface, and only one very small live snail sheltering under a log. One aspect of the snail’s biology is particularly relevant to regeneration work in the woodland - Stephanie told us she has never found any Meridolum corneovirens where there is dense litter from weedy Olive trees. There was excitement when we found two different types of native earthworm, one quite large - not quite rivalling the giant Gippsland worms, but over 20 centimetres long. Native carnivorous snails, Austrorhytida cappillacea, are also present in the woodland.

Meanwhile, as there has been so little rain, resprouting after the September woodland fire has been muted. Burnt Bursaria shrubs have lots of green basal shoots, but grass resprouts seem to have definitely provided food for rabbits. By late November, burnt areas are enlivened by the resprouting herbs Brunoniella australis and Sida corrugata, flowering mauve and yellow respectively. (2001)

December - a quiet time

December may be dry and brown - a quiet time. Ants about.

January - plants are resting

Another warm summer day in the Woodland at Mount Annan - yes, another fine day with no rain! This must be January! The plants tell us it is - the ground cover looks like a pale brown sea as grasses hold aloft more dead leaves than green. Ground-hugging herbs have died back and are holding their remaining leaves vertically to minimise heat absorption, tiny fern fronds have shrivelled to brown. Looking at the parched soil surface, one can understand why. The ground is so dry, large cracks have appeared in some areas.

We walk through the area beside Mount Annan Drive burnt experimentally last September. At first glance, one might be tempted to believe in the media interpretation trumpeted after every bushfire - bushland 'destroyed' by fire! The blackened ground is still largely bare in between small patches of green leaves where eucalypts, grass tussocks and Bursaria shrubs are resprouting. The ground is so dry the cracks form a pattern of polygons.

But we know that the burnt woodland will be green again - the plants are just waiting for that elusive rain! When the soil is nice and wet, many of the woodland’s 100 or so species of small ground-hugging native plants and grasses will resprout from dormant rootstocks. But there will also be new seedlings popping up, just like they do in your garden when you water it.

And look upwards a little, you will see that the trees are thriving - bright green canopies match the intensity of the clear blue summer sky behind them. Although some herbs invest heavily in their root systems, tree roots go deeper. (2004)

February and March - good soaking rain

Good soaking late summer rain in February and March has transformed the Cumberland Plain Woodland at Mount Annan Botanic Garden from dried yellow to lush green. In mid-February, woodland plants had come alive and green again after the drying heat of January, and by the time of our mid-March monitoring visit, the woodland understorey has a feeling of vibrant growth.  So many plants putting out new shoots and buds, flowering, and beginning to set seed. Lots more seedlings have germinated in the area burnt by the experimental fire last September, emphasising the point that post-fire recovery of bushland is very dependant on the weather conditions after fire. Although previously there was sporadic germination of seeds from the soil seed bank in the fire-bared area, it has taken the good February rains to stimulate mass germination.

One particularly heavy fall on a February morning left water streaming across the road, and the dam the fullest we have ever seen it.

Of course, many of the seedlings are weeds - *Sida rhombifolia, Paddy’s Lucerne, is particularly common.

The rain also stimulates more lush green growth and flowering of plants that resprouted after the fire. Plants of Sida corrugata, a ground-hugging native relative of the troublesome Paddy’s Lucerne, are peppered with small round yellow flowers, patches of the common creeping herb Brunoniella australis are dotted with small round mauve flowers, while the larger spreading pea Desmodium brachypodum has developed long sprays of pink flowers.
 
Quickly putting up inflorescences are the resprouting grasses, including the common Aristida ramosa, a wire-grass, Chloris ventricosa, a windmill grass, and Themeda australis, Kangaroo Grass. Less common grasses also flowering include Sporobolus creber, a native relative of the weed Parramatta Grass, Aristida vagans, with its distinctive spiky-looking inflorescences, and delicate Austrodanthonia racemosa, one of the wallaby grasses with fluffy seeds.

Naturally the lush plant growth is attracting insects intent on eating leaves and pollinating flowers. These in turn are attracting Nephila spiders, who have once again begun festooning the Bursaria shrubs with their golden webs after being absent during the drier unproductive summer weather. Unfortunately our presence in March attracts the biting green-eyed 'March Flies', and their larger buzzing golden-brown-eyed cousins. ( 2002)

With a rush of growth and activity after replenishing rains, the seasonal cycle has begun again.

Ecology of Cumberland Plain Woodland

Tree illustration

Bearded dragon illustration

Butterfly illustration

Cicada illustration

Corrella illustration

Fox illustration

Spider illustration

Eucalypt illustration

Frog illustration

Hoverfly illustration

Magpie illustration

Seedling illustration

Mushroom illustration

Oxalis illustration

Plover illustration

Solenogyne illustration

Wallaroo illustration

Sida illustration

Snail shells illustration

Bursaria illustration


Asterisk * indicates exotic species naturalised at the Australian Botanic Garden.