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INDEX ***Timelines Project*** Seasonal Calendars *** Observations *** Freebies *** Why? *** Links
THE USEFULNESS OF PHENOLOGY STUDIES Kevin McDonald PHENOLOGY is the study of cyclical change in nature. Thus phenologists begin by recording as much data as possible about such phenomena as the flowering times of plants and the migratory times of animals. These events result from seasonal, climatic and other changes in the environment. The records kept by phenologists may then be used to predict when certain events will occur in nature. Such predictions can be as accurate as a given week (or even the very day) of the year. However, many changes are quite gradual, with some individuals in a population of plants or animals exhibiting change several days (or even weeks) earlier or later than other individuals. Many of the changes which occur in nature result from the fact that the earth is tilted on its axis (relative to the plane of its orbit around the sun) at an angle of 23.5º. This tilt causes the changing seasons of the year to occur, while the rotation of the earth on its axis results in the sequence of day and night once every 24 hours. The combination of the annual (seasonal) sequence and the circadian (day/night) sequence results in increasing or decreasing amounts of light and heat being available for any given point on the earth's surface. All life on earth has evolved over hundreds of millions of years under this regime of regularly changing amounts of light and heat. Thus organisms have acquired through evolution mechanisms to cope with these changes in order to survive extremes of heat and cold, and to exploit the availability of water, food, shelter and other requirements. Phenologists are able to construct calendars showing when certain changes will occur in nature. The most visually effective types of calendar are those based on a circular design, since such "wheel diagrams" emphasise that there is no fixed beginning or end of any "year", but rather an ongoing, never-ending series of spirals in time, with humans at liberty to choose any date on which to commence a 365_ (earth year) sequence, or "timeline". Humans have always had trouble in trying to divide up an earth year into useful units such as weeks and months, and we are stuck with the fact that the year is designated to commence on the 1st January, rather than some more astronomically logical date such as the summer solstice, or the spring equinox. Humans have also grossly oversimplified the sequence and length of seasonal change by designating four seasons of the year, each of three months duration: spring, summer, autumn and winter. In many long-populous areas of the northern hemisphere (such as England or the USA), this "4-seasons" mindset works quite well, and there is a fairly dramatic and short shift from one season into the next, but for many areas on planet earth (such as the tropics and polar regions) the "4-seasons" division is totally meaningless. In a temperate-region country such as Australia, the year is more logically divided up into a sequence of identifiable seasonal phases, some of which may be as short as two months, others as long as four or five months. The aboriginal people of Australia had names for these seasonal phases, with the names implying the availability of food sources or the appearance of certain weather phenomena. Phenology studies have evolved from a centuries-long tradition of natural history. Humans have long been fascinated by the ever-changing sights and sounds of nature, and enjoyable activities, such as bird-watching, collecting insects and identifying wildflowers have formed part of the ethos of people in many countries. People have been inspired to write poetry about nature, compose music inspired by nature, to sketch and make paintings of flowers and birds, and to photograph nature in all its moods. The scientific disciplines of botany and zoology have seen the accurate recording and analysis of an immense range of natural phenomena. A downside of scientific progress has been the increasing complexity and sophistication of biological research to the point where many amateurs feel alienated from the mountain of esoteric, statistically analysed knowledge compiled by "the experts". Yet there will always be a place for the ordinary person who is simply interested in nature as an enjoyable hobby and who wishes to continue the pleasure and excitement of being "out there" in the bush, the forest, the coastal headland, the lonely beach, and the dry desert. People have established natural history societies, and there has been a proliferation of books and magazines dealing with wildflowers, fungi, birds, mammals, insects and so on. Naturalists become highly skilled after years of observation and extensive reading. There are many expert bird observers and amateur botanists who can tell you exactly where and when you will find a particular bird or plant species. The skilled naturalist becomes the phenologist without necessarily acknowledging the existence of this word. (It is noted here that the term: "phenology" should not be confused with similar words having entirely different meanings, such as: phrenology, penology, phonology, philology, and phytology! Phenology is derived from a Greek word meaning "appearance". The reader can look up the meaning of the other words in a dictionary.) With continuing studies in phenology, highly useful knowledge
is obtained, such as being able to: It becomes very satisfying for keen naturalists to be able to walk through the bush confident that they will make or confirm certain discoveries. This ability comes through long experience, reading about the work of other naturalists, and, above all, keeping detailed records, with dates, times and places noted. The skilled naturalist will often be able to explain why certain events seem to be (or are) occurring a little earlier or later than usual. Some changes in nature occur almost suddenly, or depend on a certain "trigger" such as the arrival of rain after months of drought. That is, they are not so much dependent on changing light and heat regimes as on the vagaries of weather phenomena or the event of a bushfire, or some other cause. Phenological studies have received a boost in recent times through their potential value in providing evidence for significant climate change, notably with reference to global warming theory. Plants have been observed flowering weeks earlier than usual, and migratory patterns of birds and other animals have departed significantly from those recorded in previous decades. Thus phenology networks have arisen, aided greatly by internet technology where websites specializing in this area of knowledge have aided the rapid exchange of information from observers all over the world. Whether or not human activities resulting in greatly increased levels of greenhouse gases in the atmosphere are the cause of global warming is another matter. It could well be that the earth is passing into a warmer phase (due to some cause other than greenhouse gases) like many such phases in earth history. Indeed, some earth scientists have predicted that another Ice Age is due, if not overdue, and that within decades or centuries there might well be a cooling phase ahead! It would be somewhat disappointing, however, if evidence for global warming were to be the sole or main motivation for keeping records of natural events. Phenology studies offer much more than adding to this worrying aspect of our planet. At the level of nature study as a hobby interest, phenology studies add to the joy of daily discoveries in the natural world. That is, there is always something to look forward to when one is "out there" in nature. The discovery of some previously unknown phenomenon or occurrence adds to the excitement of enjoying one's home garden, or nearby bushland, or that holiday away from home in unfamiliar countryside. Sharing one's observations about change in nature simply adds to this enjoyment. This is why so many people become members of natural history societies, or native plant societies, or bird watching clubs. Some of the changes in nature are due to a complex of causes, such as the introduction of exotic plants and animals into a different country, or changes brought about to microclimates due to large-scale clearing of vegetation. In this context, the gradual disappearance of a particular species of bird or mammal might have nothing to do with global warming, but much to do with habitat destruction or the introduction of diseases, fungal, bacterial or viral. It is up to the field naturalist to identify any significant changes which are occurring, and then to put forward possible explanations as to why. Phenology studies, whether by professional scientist or amateur field naturalist, can contribute valuable information and hypotheses for the advancement of knowledge and the identification of potential problems, not to mention the offering of possible solutions to such problems. Thus phenology studies have an important part to play in helping
to identify and protect the biodiversity of the planet. There
is so much we don't know about our native flora and fauna, and
so little time to unlock some of nature's secrets as the scale
of land clearing and other developments push natural systems
to the brink of extinction. One Australian scientist has claimed
that many Australian bird species will become extinct within
the next 50 years. The causes of threats to our heritage of native
plants and animals must be identified and where possible, action
should be taken to at least minimise these threats and instigate
such measures as large scale plantings of shrubs and trees. And the seasons of the year. I want to know what's happening With the plants and wildlife here. As the seasons pass nearby; The questions asked are: WHAT and WHICH, And WHEN And WHERE and HOW, And WHY? To the flowers and birds of kind? The WHICH is just which creature Does my searching seek to find? The WHEN is so important: Time of day, or month, or year? The WHERE is where to find it In that great big world out there? The HOW is what mechanics Makes Nature tick on time? And finally, the WHY The hardest ask of all; What end result or function Does the happening serve to call? PHENOLOGY Flowering Times & Periods List of reasons why one individual plant might flower earlier
or later, or show a shorter or longer flowering period than another
individual of the same species 1. Latitude differences: Individual plants (of the same species) tend to flower about four days earlier or later for every degree of latitude difference. 2. Longitude difference: Plants tend to flower about one day earlier or later for every degree of longitude difference. 3. Altitude difference: Plants tend to flower about one day earlier of later for every 30 metres of altitude difference. 4. Genetic differences: 5. Soil differences: 6. Locational aspect: Plants growing in otherwise identical situations (i.e., of latitude, soil type, etc) may exhibit different flowering regimes due to their particular location in relation to aspect (e.g., north versus south-facing), slope, degree of shadiness or exposure to sun or wind. 7. Age: Individual plants (of the same species) may exhibit marked differences in flowering characteristics, including earlier or later flowering times, according to the age of those plants. Some young plants may not flower at all until they reach a certain age, while somewhat older individuals may show different flowering patterns compared to very old individuals of the same species. 8. Stress: Populations (or individuals) of a certain species may either not flower at all in a given season, or, in marked contrast, may flower profusely due to environmental stresses such as drought and disease, or marked variations away from normal seasonal trends. DISCUSSION The 23.5º tilt of the earth (in relation to the plane of its orbit around the sun) is the fundamental cause of the changing seasons, conventionally referred to as: Spring, Summer, Autumn and Winter. All life on earth has evolved within the strictures of this repeating annual sequence of lengthening and shortening hours of daylight, together with increasing and decreasing levels of heat energy from the sun. If the earth was not tilted, but remained rotating at 90º to the plane of its solar orbit, there would be no seasons as we know them. (Note that the elliptical, rather than circular orbit of the earth around the sun would cause the planet to become slightly hotter and colder during any one year, producing conditions for very weak "seasonal" changes, but these would be very small compared to the changes brought about by the fact of the 23.5º tilt.) Of course, if the earth remained rotating at 90º to the plane of its solar orbit, the lengths of daylight and nighttime for any position on the earth would always be the same throughout the entire year. If the tilt of the earth was greater or lesser than 23.5º, seasonal changes would be either more or less dramatic than they presently are. For example, if the earth were tilted at an angle of, say, 30º then summer would be unbearably hotter and winter unbearably colder for most organisms to survive than is presently the case. The cause of the earth's 23.5º tilt is not known with certainty, but is thought to have been caused by a major collision between the earth and some other enormously large object early in the earth's history, thousand of millions of years ago. Other planets in our solar system have tilts also, some less, others greater than that of our earth. As producer organisms (green plants) evolved on earth, they had to cope with a range of environmental conditions (at any given locality) including increasing/decreasing day-length (i.e., light availability) and increasing/decreasing temperatures (i.e., heat energy), throughout the year. They also had to cope with widely ranging extremes of water and nutrient availability, the effects of strong winds, the impact of plant-eating animals, and other physical, chemical and biological influences of any particular environment. Plants (and, of course, the animals which depended upon them for food) gradually evolved a very wide range of cellular, organ and ecosystem adaptations in order to survive. Some plants in cold climates evolved such mechanisms as the ability to shed leaves in snow-clad environments (deciduous plants). Plants in hot, dry climates evolved structures (sunken stomates, hairs, thick cuticle, etc) to minimise water loss. Many changes occurred at the level of cells and their constituent protoplasm, for example, eucalypts are extremely well adapted to the hot, dry Australian environment by having thick-walled, non-collapsing cells (sclerophyllous cells), containing protoplasm which can almost dry out before lasting harm occurs to the plant. Amongst the multitude of strategies which plants evolved was that of the timing of the periods of budding, flowering and fruiting. Some plants became "long-day" plants, i.e., those which only came into flower as the days began to lengthen, while other became "short-day" plants, flowering only when daylight was shortening. This triggering of flowering due to the length of time of exposure to light is referred to as photoperiodism. Some plants evolved vegetative structures which enabled the plant to both survive and spread without the need to always flower to produce seed. (They still flowered, of course.) Such vegetative structures include bulbs, corms, and rhizomes. Plants also evolved ways of dealing with extremes in availability of water. In hot, dry areas prone to long droughts, the seeds of many plants possess long viability (with hard seed coats, etc), and only germinate when the rains arrive. And then, many such plants come into flower rapidly, set their seeds and then die. At certain times, huge areas of inland Australia are covered with a blaze of colour as the desert plants bloom. The plants soon wither and die, however, and some years may pass before this sight occurs again. The 23.5º tilt of the earth means that there are large zones of the earth's surface which are subject to contrasting ranges of light availability and temperature extremes. In broad biogeographical terms, we distinguish between tropical (equatorial), temperate, sub-polar and polar regions. The plants (and animals) in these zones differ greatly from those in other zones in many ways. In equatorial areas, the forests are lush and green, and many plants flower throughout the year, with little seasonal variation. In warm temperate zones, flowering shows definite seasonal tendencies, whilst in cool temperate zones, seasonal contrasts can be quite dramatic, with very narrow "windows of opportunity" for plants to flower and set their seeds. Thus the latitude at which a given plant species is of crucial importance to the ability of a plant to flower or even survive. In order to cope with the rigours of the changing seasons, plants must be able to detect and respond to increasing/decreasing amounts of light and heat energy. Within the DNA of plant cells there are genetic "switches" which can be turned on or off by changing light regimes. Plant scientists are able to investigate these mechanisms and their effects by employing simple experiments to artificially manipulate the amount of light available to a plant. At an advanced level such experiments are undertaken in plant growth chambers, or phytotrons. In the horticultural industry, such manipulation can be performed on a large scale, where the blooming of flowers for the cut-flower market is undertaken in glass (or plastic) houses with shutters and night control of lighting thus regulating the timing and duration of light energy and causing the plants to flower either sooner or later than they would normally. In nature, a plant has to "get ready" for the sequence of bud formation, flowering and fruiting. It does this (in part) by detecting whether the daylight hours are lengthening or shortening. The genetic switches have evolved for various plants to ensure their survival in a given environmental situation. Thus many Australian wildflowers come into bud and then flower very early, usually in August-September, ensuring that the seeds have been set within the developed ovary well before the long hot days of summer arrive. Many Australian plants have hard, woody fruits which protect the seeds inside both from the heat and frequent bushfires which are such a part of the Australian environment. Thus flowering for many of our Australian plants is well and truly over before the official "summer". This strategy is not the same for all Australian plants. Some of our plants are winter-flowering (e,g,, many Banksias, and most of the terrestrial orchids). When a plant species is transported from one part of the world to another, it will only survive and reproduce if the conditions in its new environment are reasonably similar to those where it evolved. Thus many tropical plants and cool temperate species will either grow poorly or not survive at all in the Australian environment. In order to grow certain plants from cold countries (e.g., Tulips) in the Australian environment it is necessary to subject the bulbs to a period of artificial cold, i.e., vernalisation (e.g., in a refrigerator) if the plant is to grow well. Even then, daffodils might grow well enough in the climates of Canberra and Bowral, but would not survive at Alice Springs! The generalization made about the importance of latitude applies similarly to altitude. In general, temperature regimes become colder with increasing altitude, thus enabling some plants to survive (those which have evolved to cope with cold temperatures) but preventing others from having any hope of survival. Thus we see clear-cut examples of the zonation of plant species and plant communities with increasing altitude in mountainous areas. Another factor determining both the very survival and the flowering success of a given plant species is that of its specific location within a certain environment. It is well known that some plant species demand open, sunny positions, while others will only survive in shady positions. The aspect of the environment is very important, e.g., whether a given situation is north-facing or south-facing, whether the land is flat or sloping, and whether the area is subject to, or protected from strong winds or the influence of seaborne salt. Yet another factor for the very survival of a plant let alone its flowering success is the set of physical and chemical conditions of the soil in which it is growing. Soil pH (relative acidity or alkalinity) is crucial to the success of many plant species. Acid-loving plants (such as Azaleas) will not grow in alkaline soils. If the soil pH is unfavourable, the plant may survive but may not flower well or at all. Of great relevance to the flowering of a given plant species is the issue of the age of the plant. All organisms have a species-specific life cycle. Certain plants (annuals) live only for one year, or less, growing from seed to flowering to seed set and then dying within that short time. Other plants (biannuals) take two years for this cycle. All other plants are perennials, some living for fairly short lifespans (e.g., Australian wattles which live for periods roughly between five and twenty years at the most), others have very long lifespans (e.g., some of our Australian eucalypts which may live for two or three centuries). Within these lifespans, flowering will generally not occur in the first few years, and then will occur on a fairly or very regular, seasonal basis for many years. With increasing years, flowering may become more erratic until death occurs. Some plants, however, reveal highly irregular flowering patterns, flowering very well in one year, not at all in the next, or flowering poorly in between "good" years. The Australian plant, the Flame Tree (Brachychiton acerifolius) can flower spectacularly in one year, and then exhibit poor flowering until some years have passed. The "triggers" controlling these events are not fully understood. The above discussion shows how difficult it is to predict
just when a certain plant species will flower or even survive
where it has been introduced into a new location. It also shows
that the length of the flowering periods of some species may
differ from one area to another, or from year to year in the
same locality. The discussion has been very brief and has not
touched upon the many mechanisms involved including the production
and transport within the plant of hormones which either initiate
or inhibit flowering times and periods. However, one final fundamental
point should be made: the annual flowering of naturally occurring
native plants is, in general, a predictable phenomenon which
shows little variation in starting time and duration from year
to year unless some major factor is at work such as a prolonged
drought, abnormally wet conditions or a severely cold winter.
Mother Nature is generally "on time", with many phenological
events commencing in the same week of each year, for any given
locality. Of concern to biologists, however, is the phenomenon
of global warming (whatever its cause) which currently appears
to be triggering significantly earlier responses in plant flowering
(and animal migration) than those documented in previous studies. AIMS of the NATURE WATCH DIARY Project: Overall statement: The Nature Watch Diary project is designed to encourage people to record, on a regular and organised basis, their observations of the natural world around them in order to detect predictable, useful and interesting patterns and trends in nature. The nature watch diary project aims to provide: 1. A satisfying and productive hobby for people with an interest
in nature. NATURE WATCHING THROUGHOUT THE YEAR a great hobby
interest: Honorary coordinator for the Hunter region: TIMELINES
HUNTER incorporating the HUNTER PHENOLOGY NETWORK and the NATURE WATCH DIARY Honorary coordinator: Kevin McDonald Explanation: Phenology is the study of the times of recurring natural phenomena, especially in relation to climate and seasonality. The dates and times of natural events, such as the commencement of flowering of a certain plant in a given area, or the first appearance of a migratory bird species in a given locality are of central interest to phenologists. Such observations are documented on a regular basis (e.g., by means of a Nature Watch Diary). As records are built up over a number of years, it becomes possible to predict (often with considerable accuracy) when certain natural events will occur. Where such trends as earlier or later than expected are discerned, explanations are sought by phenologists to explain such discrepancies. For example, it is currently considered that the phenomenon referred to as "global warming" is causing some natural events to occur days, or even weeks earlier than in past decades. This website will feature records from participants in the NATURE WATCH project, which is being undertaken in the Hunter region, NSW by a small but growing network of volunteers who maintain their Nature Watch diaries as a keen hobby interest. It should be pointed out that "nature watching" (including recording of observations) for most participants is simply an enjoyable, private hobby interest in the general area of natural history. For more committed people, records may be shared with others and linked to various databases, including various phenology networks now becoming available on the Internet. Attention is drawn to the inspiration behind TIMELINES HUNTER, namely the establishment some years ago in Victoria, of the project known as Timelines Australia, by the well known naturalist, Alan Reid. This project has seen the establishment of nodes of seasonality studies in all states and territories of Australia. Alan Reid's book: Banksias and Bilbies (Gould League of Victoria) provides an easy introduction to the project. In addition, Alan produces a bimonthly newsletter: Timelines News, which provides a summary of activities and records from contributors around Australia. Alan has established a Timelines Field Centre on his property at 240 Burns Road, Glenburn VIC 3717, phone/fax: (03) 5797 8495; email: [email protected] Another important contribution has been made by Michael Smith, the designer of this website, who produced the book: Bush Mates: A Guide to the Wildlife of Nelson Bay. This book also adopts the diary format so useful for studies in seasonality in nature. INDEX ***Timelines Project*** Seasonal Calendars *** Observations *** Freebies *** Why? *** Links |