It was during a recent weekend, when the wind changed direction to the north-east, and within a short time sycamore leaves — showing their orange tinge — were descending rapidly, that I felt that the autumn season was well and truly underway.

Many of the contributors to the Woodland Trust’s phenology survey —called Nature’s Calendar — have already been aware of this for a little while, according to the observations that they have been sending in for the trust’s recording scheme of autumnal events.

Carole Watts, of Southmoor, has been taking part in both the springtime and autumn surveys for the past two years.

She said: “We are concerned about the environment, but you have to have proof of change, so the more records of earlier leaf-fall or earlier budding that we can have to provide actual signs of that change, the better.

“I am recording as and when I can — some things are more difficult to find, but I usually see these changes while I am going around the village, while out on walks, and when I am in other local towns and villages.

“As I look out in my garden, most things are still green, but the Virginia creeper is turning a bright shade of red.

“I have noticed a horse chestnut tree near my house where the leaves are going brown early because of the disease that is affecting this species. It used to have very large conkers, but last year they were small, and this year there seem to be very few.

“I have found a huge crop of sloes, they seem to have ripened early. There are a lot of blackberries and the wild plum trees, the bullaces, have been full of fruit.

“The rose hips ripen later in the season but I have found a few.”

Mrs Watts and I both noticed a few weeks ago the ripe bunches of elderberries, but have since seen that the birds had already been making inroads into this food resource, as they build themselves up before the winter.

Jane Harrison and her 11-year-old son, Alfie, live in Oxford, and they took a cycle ride out to Otmoor to see how autumn has been progressing in the countryside.

“The hedges were changing colour,” said Alfie. “We saw berries on the hawthorn. There were flowers on the ivy — they are very important for both the flowers and the berries they will produce for wildlife.

“We saw horse chestnut trees that had brown leaves, and the conker crop is not very good. It’s odd really.”

Mrs Harrison has noticed the autumn bounty of blackberries in Boundary Brook Nature Park is being put to good use. As well as by the birds, they are being enjoyed by a family of foxes. “It is good to see them all feasted upon by wildlife,” she said.

The information gathered by its recorders enables the Woodland Trust to monitor changes over successive seasons, and it would welcome more contributors to the records for autumn.

Richard Smithers, the trust’s conservation advisor, said: “Advances in the date of spring phenology have been very marked, both in the UK and elsewhere. But changes in autumn phenology have been less clear.

“Autumn is a harder season to assess, because recording has always been less popular at this time than in spring — and consequently there are fewer historic dates available.”

The phenology team received 34,000 records of individual autumn events that were submitted to Nature’s Calendar in 2008. This has declined from 48,000 in 2007 and 60,000 in 2008.

“We particularly need people to continue recording autumn events and to encourage their friends and family to do likewise, so that we can gain as good a grasp of what is happening as we can in relation to spring events,” said Mr Smithers.

The temperatures of the second half of 2008 were very close to the average for the 30 years from 1961 to 1990, being only 0.19 degrees centigrade below it.

Summer and autumn fruiting records in August and September were, on average, four days later than the average. It is thought that later flowering of blossom in spring delays fruiting in autumn.

Consistent with this idea, January to June 2008 had been a period that was 0.82 degrees cooler than the same six months of 2007, the year which produced the warmest spring on record. Fruiting in 2008 was 19 days earlier than in the trust’s springtime benchmark year of 2001.

Classic autumn events are the departures of the summer migrants, the swifts, swallows and house martins, and the arrival dates for the winter migrants, the fieldfares and redwings, the first tint and full tint of leaves, leaf fall and then bare trees.

In comparison with 2007, records received showed that the departing birds were last seen two days earlier, and the arrivals three days later. The leaf-related events however differed by only one day for final leaf fall, with the first and full colouring tints being observed on exactly the same day.

The year of 2007 is now being taken as the autumn benchmark, as the temperature overall was only 0.04 degrees above the 30-year average.

In Oxfordshire, the departure of swifts took place at the very beginning of August, with the swifts who had spent the summer in Charney Bassett being last observed there on August 2. The house martins, which had summered in the Abingdon area, were last seen on August 11.

The only flowering record needed for the autumn is that of the ivy; ivy flowers were seen in Southmoor on August 12. They are always a welcome sign, for they are enjoyed by the bees and other insects now, and then at the end of winter provide a vital source of food for other wildlife at a time when supplies of berries produced earlier by other trees and shrubs have been exhausted. Blackberries were seen particularly early in the Didcot area, for the Woodland Trust received a record for July 27. In most of the recent years the average date of bramble fruit ripening has been in August.

The sloes on the blackthorn in Duns Tew were also ripe for picking at an early date. A record was received from there for August 16. Only 2007 had an average date for first fruiting as early as August.

Recorders are asked to select mature trees, of 30 years standing or more, for their observations as young trees may show unusual responses.

So that the ‘trendsetters’ rather than the ‘extraordinary’ are taken as examples, recorders are asked to wait until an event such as leaf tint is occurring in three trees of the same species in close proximity to one another.

Weather conditions such as drought can have specific effects. Drought can affect such species as beech and oak with results including early colour changes and shrivelling of leaves. Another weather effect may be that trees become bare of leaves before any significant colour change has been recorded.

Trees which form part of the survey are the ash, beech, field maple, horse chestnut, both the pedunculate and sessile oaks, the rowan, silver birch and sycamore. Sycamore leaves showing their first tint were recorded in Southmoor on August 8 — September is much more usual. The first conkers fell from a horse chestnut tree in Banbury on August 25, again a variation from the normal September average.

Shrubs surveyed are the elder, hawthorn, hazel, holly, blackthorn, bramble and dog rose.

Details of how to contribute to the survey are available at naturescalendar.org.uk, or from the Woodland Trust office, on 01476 581111.

Autumn reed cutting will soon start at Hogley Bog (formerly known as Bullingdon Bog) in the Lye Valley Site of Special Scientific Interest (SSSI) near Headington, close to the heart of Oxford.

It is the next stage in regular work to maintain this green space. Work carried out by greens staff at Southfield Golf Club earlier this year has resulted in the clearing of scrub and woodland on the site at this rare fen habitat.

The fen is next to Southfield Golf Course.

In June this year, a group of local volunteers and members of the Oxford Urban Wildlife Group cleared areas of the fen of the invasive plant Himalayan Balsam, helping to restore the natural environment.

Also known as Poor Man’s Orchid and Policeman’s Helmet, Himalayan Balsam is invasive and grows very fast to a height of over two metres, shading out important native species of plant. Its pretty pink to purple flowers produce explosive seed capsules which scatter the seeds more than seven metres away, allowing the plant to spread rapidly.

Lye Valley SSSI is one of the best recorded examples of a calcareous valley in southern England. There are only a very few other places in Britain where calcareous fen habitats can be found. These include a few locations in Oxfordshire, and in East Anglia and North Wales.

The fens in Lye Valley have been studied by botanists since the 17th century, many of whom would have been associated with Oxford University.

Among the special fen plants that are found in Lye Valley are the very pretty Grass-of-Parnassus and the insectivorous Common Butterwort, both of which are rare in southern England.

This wet fen habitat is also home to a number of uncommon or rare insects such as the Water Penny Beetle and the Banded General Soldierfly, which is striped yellow and black like a wasp, but is completely harmless. Hogley Bog was an extensive marshy area of the Lye Valley formed because of a line of natural springs. It was also known long ago as ‘Hockley in ye Hole’ and more recently as Bullingdon Bog.

Before the golf course was created, the area was grazed by livestock, and the reeds and rushes were harvested for thatching or basket making.

This ceased early in the 1900s and the site became hemmed in by housing in the 1930s and 40s, and some of the springs dried up.

After the grazing and cutting ceased, willow and alder scrub started to invade the fen. Before the Golf Club cleared the scrub, there was only a very small area of healthy open fen habitat remaining in the lower part of Lye Valley. This part of the SSSI has been in poor condition due to a lack of management.

Natural England has brought together the interested parties and drawn on local skills in understanding and caring for this special environment.

Alison Muldal, of Natural England, said: “Already plants which previously thrived on the site have returned in increased numbers, including Marsh Helleborine orchids and Grass-of-Parnassus. Hogley Bog is now one of only three sites in Oxfordshire which supports these unusual plants.”