Woodlands at the Australian Botanic Garden

Averaging rainfall figures for recording stations in the Australian Botanic Garden Mount Annan area gives a long-term average of about 730 mm per annum for the period 1850 to 1960, with a higher average of about 830 mm for 1950 to 2004. Rainfall from 2000-2006 was considerably lower with all years receiving less than 700 mm (based on records for Eaglevale). Average annual rainfall from 2007-2016 was 759 mm, with highest rainfall in 2007 (947 mm) and lowest in 2009 (514 mm). 

Long-term average annual rainfall records are 747 mm at Campbelltown (period 1845-1961); 764 mm at Camden (Bowling Club) (1883-1968); 683 mm at Menangle (Camden Park) (1878-1968); 828 mm for Camden Airport (1943-2004); 830 mm at Campbelltown Swimming Centre (1959-1984).

Mean monthly rainfall peaked in February (99 mm) and March (94 mm), and was lowest in September (43 mm) (based on Camden Airport records 1943-2004). This has shifted in the period 2006-2016 with high rainfall slightly earlier in the year, January and February, and peak rainfall in June (105 mm) (based on Campbelltown Mount Annan records).   

 Temperatures are important for seed germination. Air temperatures are hottest in January with a mean daily maximum  of 29.2°C and a highest recorded maximum of 45°C. Temperatures are coldest in July with a mean daily minimum of 2.9°C and a lowest recorded minimum temperature of -6°C (based on Camden Airport records). Temperatures records at Mount Annan from 2007-2016 are similar, although mean daily minimum temperatures in winter have been slightly higher (4°C). 

To give an idea of seasonal conditions in the woodland we’ve included a month by month account, 'A year in the woodland', based on Jocelyn Howell's diary records in 2001-2003.   

To observe changes over time we set up permanently marked plots that we could periodically record. Initially we set up eight permanent square plots, each 5 m x 5 m, marked with steel posts and coloured tape. The Woodland Conservation Area included an area with large trees which appeared likely to have a good number of native species amongst the weeds, as well as areas with smaller trees and more open areas that had evidently been cultivated or possibly ploughed and pasture improved. When we first visited it had been grazed by stock for many years and had been recently slashed.

Historical accounts give the impression that Themeda triandra, Kangaroo Grass, was a major groundcover component of the woodland at the time of European settlement, but that this was readily eaten out by stock. Patches of Themeda triandra were relatively common in our woodland and were relatively weed free. We regarded these as the type of groundcover we hoped would expand into the more weedy areas in the absence of grazing and mowing. We placed two sites in grassland mainly of Themeda triandra (sites 3 & 4), and two sites in Themeda triandra-Bursaria spinosa, Blackthorn, grassy-shrubby areas (sites 1 & 6). To sample the weedy areas we placed two sites in *Paspalum dilatatum-*Sida rhombifolia, Paddy's lucerne, dominated areas (sites 2 & 5). Because of our particular interest in the endangered species Pimelea spicata we located one site to include part of its population, (site 7), and another, (site 8), amongst Chloris ventricosa-*Sida rhombifolia-Bursaria spinosa, with a similar shrubby structure but with no Pimelea spicata.

Initial field recording was done in December 1988 as we thought that most plants would be flowering late spring-early summer and most readily identified. We recorded the species present within each of the 25, 1 m x1 m subplots. This gave us a frequency out of 25 for each plot, and a total frequency out of 200 subplots, a measure of abundance that we could remeasure, to observe increases or decreases. Our 8 plots set up in 1988 included occurrences of about 50 % of the plant species (69 out of the 134) recorded in the woodland at that time.

Some difficulties often encountered in monitoring Cumberland Plain Woodland

• Dry conditions seasonally and even daily.
• Tiny species make location and identification difficult, particularly if they are also short lived e.g. Phyllanthus virgatus.
• Similar closely-related species make identification difficult e.g. Austrodanthonia species.

Rabbit exclosure plots By 1991 rabbits were becoming common in the woodland and despite the assurances of the Gardens' management that a control program would eliminate them within 6 months, evidence of their activities became increasingly obvious. We had not considered the impact of rabbits during the initial setting up of the plots as there was no evidence of their presence, and the open conditions of the grazed landscape and presence of dogs presumably kept them in check. However the taller growing groundcover and the fencing of the Gardens obviously provided them with suitable conditions to flourish. In 1991 we set up three fenced exclosure plots, Plot 9 paired with Plot 6, Plot 10 paired with Plot 8, and Plot 11 in open grassy area at the top of the woodland, paired with a new unfenced plot 12. We particularly wanted to see whether natural recruitment of native seedlings was retarded by rabbit grazing. These plots were recorded at the same time as Plots 1-8.

Subsequent recording of all the plots was done on an ad hoc basis as time allowed. The plots were recorded in May 1991, November 1991, December 1992, December 1993 and December 1996.

After the 1996 recording we began to question our expectations of the change in the woodland. There was not the great expansion of native species we had expected. Instead change was very slow. What was beginning to happen however was that some of the perennial weed species were beginning to expand. This was obvious in observations in the woodland, and was confirmed in the plots. In particular the weedy shrub *Olea europea subsp. cuspidata, African Olive, was clearly becoming more common in the woodland, particularly under large Eucalyptus trees. The time spent on the sample plots seemed disproportionate to the questions being raised, which related to rare species, that were mostly not represented in the plots. Other work commitments reduced our available time for the project, allowing only occasional visits to the woodland and not allowing for the week needed every year to record all 12 plots plus the time to consider the data. No recording was made from 1997 to 2000 though we visited the woodland sporadically during this time.

Following changes in work programs at the end of 2000, we were able to allocate more time to the woodland allowing us to record our sites in January 2001, December 2001, December 2002, December 2003, December 2004 and December 2005.

Monthly recording In 2000, after reviewing the woodland plot data from the previous 10 years, during which relatively little seemed to have happened, we became concerned that our narrow window onto the woodland, our December recording, meant that we were missing important changes in the vegetation that occurred in other months. We had initially chosen December for annual recording to maximise our level of identification, based on our wider experience on sandstone areas where major flowering is in spring, and modified by knowledge that grasses are more readily identified by their fruiting in summer. We realized that many of the plant species were opportunists and that major ecological events such as seedling recruitment, flowering and fruiting, were being influenced by rainfall and temperature events which occurred irregularly over the year.

We therefore selected two of our plots, Plots 4 and 9, for regular monthly recording. Plot 4 was an unfenced grassy plot which was left undisturbed without any treatment. Plot 9 was a fenced Themeda-Bursaria plot set up in 1991. Neither plot has been burnt in the 20 years to 2006. These two plots contained a good variety of woodland species, 67 natives, (50% of our total of 134) and 34 exotics.

Our more frequent recording subsequently has shown that overall there is more growth and flowering after rains in late summer and autumn than there is in spring, although a handful of species grow more in spring.

Seasonality recording To explore the issue of seasonality further we have been recording the flowering and fruiting times or seasons of the woodland plants. This is known as phenology. Our initial view that flowering and fruiting timing were likely to be similar to the patterns observed on the familiar Hawkesbury sandstone areas was changing, and we wanted to observe changes in our woodland more closely.

Fire trials We carried out a trial ecological burn in part of the woodland in 1991. 

We carried out more experimental burns in parts of the woodland in September 2001 when we again burned the area previously burnt in 1991. The adjacent area to the west was burned in September 2002, the area to the north, including adjacent grassland, in September 2005.

Asterisk * indicates exotic species naturalised at the Australian Botanic Garden

We originally chose the Conservation Woodland for a study site because of its large trees. In some parts the trees are up to 25 m high with diameters of up to 1 m. These are some of the largest trees we have seen in Cumberland Plain Woodland in western Sydney and are likely to be at least 100-200 years old. In some parts of the woodland however the trees are much smaller, evidently where the original trees were cleared during the farming period and young trees have grown since then.

Eucalypt seedling recruitment is generally confined to areas around the canopy of mature seed trees, or within 20 to 30 m of tree canopies This pattern is commonly observed in woodland at Mount Annan. This is because eucalypt seed is small and has no special dispersal mechanism apart from being shed 10-20 m above the ground to be blown a few metres away and may be washed a further few metres across a bare soil surface in rainwater. A lot of seedlings came up following the cessation of grazing in the 1980s and are now trees up to 8 m high.

Interestingly there has been very little subsequent recruitment in the woodland since the 1980s. A few seedling have been recorded in the sample plots but none of these have survived. The only obvious recent successful recruitment has been near the road along a line dug for a water pipe where backfilled soil provided bare soil for the seedling recruitment, trees overhead provided seed, and there was enough rainfall.

Most of the sapling recruitment has been of Grey Box Eucalyptus moluccana and Forest Red Gum Eucalyptus tereticornis, with a small amount of Narrow-leaved Ironbark Eucalyptus crebra. However during the 1990s many adult ironbarks gradually died despite relatively favourable rainfall conditions. We consider that these deaths were a delayed long-term result of the 1980s drought, and the impacts of the increased nutrients and compaction of the soil by stock grazing.

Flowering and fruiting by the woodland eucalypts is very sporadic. At no time could we say that all mature trees of a particular species were in flower, though we would note occasional individual trees flowering. Nor could we note any clear seasonal trends in those individuals that did flower. Fruiting occurs a considerable time after flowering, but again we have not noted any distinctly recurring patterns.

Halo effects around trees

In some areas we noted that the understorey under large trees was different to that nearby. There were more Einadia plants, and weeds such as *Sida rhombifolia. We put this down to these being the site of old stock camps, resting places for animals during hot weather, where nutrients had been locally increased, conditions the Einadia plants would like. However these conditions seem more widespread than we had thought, and a listing of species within about 5 to 10 m of large trees includes the following - 4 species of Einadia, 2 Solanums, *Olea europea subsp. cuspidata and *Sida rhombifolia, grasses rare. These species all have fleshy fruits and are likely to be spread by birds, therefore being concentrated below canopies of large and particularly remnant trees. These effects are most conspicuous under old well-established trees, and may take at least 20 years to become noticeable. First established under isolated trees are the *Olea eurapaea subsp cuspidata, African olive, followed by Einadia species. It is likely that *Olea europaea subsp cuspidata will crowd out other species by its dense canopy and the growth of its own seedlings.

Prior to 1988 patches of Bursaria in the woodland were generally associated with tree bases or steeper slopes which were not slashed. Our 1988 woodland photos showed an open grassy ground cover with previously slashed Bursaria rootstocks beginning to regrow.

These Bursaria spinosa shrubs grew very vigorously to form dense thickets within about 5-7 years after slashing. After the initial regrowth, lateral spread was slow, apart from longer spreading lateral branches as the plants increased in size, with seedlings mainly recruiting under parent plants. As a result, in 2006, many of the areas between Bursaria spinosa clumps are still relatively open.

Bursaria spinosa can resprout from its base after cutting and fire. Where rootstocks have persisted in the soil after grazing or slashing vigorous recovery takes place resulting in plants up to 2-3 m high in say 5-7 years. Total rooted frequency in our 8 measured plots (200 1 m x 1 m subplots) increased from 25% in 1988 to a peak of 47% 12 years later, though it subsequently declined to 38% in the following 3 (dry) years. This measurement includes both mature 2-3 m high plants, as well as smaller plants and seedlings 5-30 cm high.

Our interpretation is that growth of Bursaria spinosa rapidly recovers where it has previously been suppressed, but that invasion into new areas is a slow process. We have previously thought that lateral spread was by rootsuckers, but extensive digging around established plants has not verified this as a possibility. Spread does appear to occur mainly adjacent to established plants, though occasional plants appear at distances of 10-20 m from the main edge by seedling recruitment. How successfully Bursaria recruits from seed, is not clear. Viable seed is produced each year, and there is no dormancy or soil-stored seedbank. We have only observed occasional seedlings, i.e. that can be identified from presence of cotyledons, but these have all subsequently disappeared. Nursery-grown plants and small plants dug up show a tapering carrot-like rootstock develops early in the establishment phase. There may also be some suppression of young plants by established adults.

While Bursaria spinosa generally resprouts vigorously after fire, regrowth of some plants burnt in the 2002 and 2005 burns has been very slow, presumably because of the low rainfall over this period.

Bursaria spinosa is very common in many Cumberland Plain Woodland remnants and there is the perception that it will crowd out other species. On the other hand its dense prickly canopy may protect associated species from stock grazing and damage from trampling, and with its relatively open canopy allows light for other species to grow. As a major component of Cumberland Plain Woodland and because of its importance in remnant sites, more research on the ecology of Bursaria spinosa is needed.  

In 1988 our initial expectation for the Woodland Conservation Area was that, with the cessation of grazing and its management for conservation, that the native plant species would increase in abundance. Certainly tree and shrub cover increased noticeably over a 10 year period, but this only involved a few tree species and the shrub species, Bursaria spinosa, Blackthorn, which was mainly from previously suppressed individuals - areas that were previously devoid of shrubs are still relatively shrub free nearly 20 years later.

Changes in the relative abundance of native groundcover species (and these make up over 80% of the plant species) have been much less obvious. Native species that were regarded as Frequent species in 1988 were still Frequent species in 2000 (an exception is the grass Bothriochloa macra which appears to change in response to changing structure), while a few less common species have increased in abundance e.g. the fern Cheilanthes sieberi.

Undisturbed woodland plots 1988-2004

Five of our 5 x 5 m monitoring plots (four plots from September 2002) were left essentially undisturbed over the 16 year period from December 1988 to November 2004. Undisturbed plots were those kept unslashed, unburnt, un-grazed by domestic stock, and unfenced - allowing access by rabbits from 1991, and kangaroos from 2000. These are essentially control plots and represent the basic management treatment for the conservation area.

The figure below shows the mean species richness measures for these plots. Native species richness was high initially with 32 species per plot, but fluctuated over the initial 14 year period, generally dropping no more than 25% of the initial measure, and returning to similar high levels after 15 and 16 years. The exception was a major slump to 16 species (a 50% drop on the initial figure) in November 2002 during an exceptionally very hot dry period. Native species richness the following year recovered to 32 species per plot.

Exotic species richness declined over the 16 year period from 16 species to 7 species, and dropped to 3 species in the very dry 2002.

Gaps in recording years however could mask fluctuations but there does appear to be a trend in decrease of exotic species over the period. Many of these species would remain in the soil seed bank or as rootstocks as is indicated by the immediate response in 2003 after the dry conditions of 2002.

The first five years - will the weeds go?

With the grazing or slashing regime lifted, we expected the native groundcover plants to increase in abundance and begin to dominate. While some native species were widespread and common in 1988, many native species had very localised populations often of only a few plants occupying an area of a few square metres. Species such as Pimelea spicata, Daviesia ulicifolia, Sorghum leiocladum, Vernonia cinerea, Calotis lappaceus, Ranunculus lappaceus and Ranunculus sessiliflorus were all very restricted and we expected to see an increase in their abundance and distribution. During the five years from 1988 however the main changes in species abundance were among the exotic species and many of these weedy species, after an initial increase, decreased or virtually disappeared. These included *Petrorhagia nanteillei, *Vulpia bromoides, *Silene gallica, *Lepidium species [they reappeared after drought], *Polycarpon tetraphyllum, *Soliva sessilis, *Stachys arvensis, *Linum trigynum, *Centaurium tenuiflorum and *Verbascum virgatum. These species were generally short-lived species, with many of the exotics being weedy annual species and are part of a group of species that we called Short-term (<5 years) responders. Data from our plots showed that species of this group decreased in frequency during the first 5 years (between 1988 and 1993), and continued to decrease further in the following 10 years. Many are common weeds in rural sites. Presumably these species benefited from the open conditions created by slashing and grazing, and particularly in the years immediately following but were unable to establish or persist as longer-lived herb species became more abundant, and the perennial grasses grew taller. Short-term (< 5 years) responders also include some short-lived ephemeral native species e.g. Daucus glochidiatus, Fimbristylis dichotoma and Ranunculus sessiliflorus, and short-lived perennials e.g. Geranium homeanum, Oxalis perennans , as would be expected, but also perennial species with rootstocks e.g. Sida corrugata. Most of these native species have long-lived soil seedbanks and reappear periodically during wet seasonal conditions, particularly where groundcover has been depleted by drought or disturbance.

The next ten years 1993-2002

During the first 5 years some species increased in frequency, but subsequently, between 1993 and 2002, decreased in frequency. These species appeared to respond best to conditions 5-10 years after grazing/slashing ceased. Medium term (5 -10 years) responders are herbs and monocots, including a particularly high component of exotic herbs. They also include annuals e.g. Wahlenbergia gracilis, *Sonchus oleraceus, *Conyza sumatrensis, and short-lived species e.g. Senecio quadridentatus, *Senecio madagascariensis, *Anagallis arvensis and perennial species with rootstocks e.g. Asperula conferta, Pimelea spicata. These species appear to be taller growing species that are susceptible to regular slashing or grazing but respond to open conditions. We have called these Medium-term (5-10 years) responders.

A third group of species either increased in frequency or at least remained relatively stable over the 14 year time span. These Long-term (> 10 years) responders are mostly native species, herbs and monocots but also includes the tree and shrub component of the woodland. Perennial species with rootstocks are a major component e.g. Dichondra repens, Brunoniella australis, Aristida ramosa, Cheilanthes sieberi, but there are also some relatively shortlived species that establish in the absence of disturbance, e.g. Solanum prinophyllum, Oplismenus imbecillis, Crassula sieberiana. 

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)

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

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

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

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

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

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)  

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

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)  

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

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)  

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 triandra, 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. With a rush of growth and activity after replenishing rains, the seasonal cycle has begun again. (2002) Asterisk * indicates exotic species naturalised at the Australian Botanic Garden.