History Of N.Z. Vegetation Learned From Pollen

Press, Volume CVI, Issue 31154, 2 September 1966, Page 16

History Of N.Z. Vegetation Learned From Pollen

Pollen which fell to the ground many thousands of years ago Ise helping

scientists to piece together the history of New Zealand’s vegetation since the last ice age, and through this to achieve a better understanding of problems relating to the country’s present flora.

Dr. N. T. Moar, a palynologist of the Botany Division of the D.S.I.R. at Lincoln, has been studying pollen ex- j tracted from sites in Canterbury and Westland. Identification of the pollen types found at different levels is enabling him to build up pollen diagrams which show the changes in vegetation in these areas since the ice retreated about 15,000 years ago. Radiocarbon dating is providing information on the times at which these changes occurred. Pollen is by no means the transient thing it appears. It is, in fact, one of the most indestructible of all plant materials. Its durability comes from the toughness of the outer wail of the pollen grain. This is an extremely resistant structure, and is not damaged even by treatment with such powerful destructive agents as hydrofluoric acid. Though the protoplasm inside the pollen is easily destroyed, the outer wall of the grain can remain in the ground in recognisable form for millions of years. Pollen grains extracted from sediments of various kinds .including extremely old ones, are studied in most parts of the world, not only as a matter of academic interest, but also for many practical purposes. Most oil companies of any size now employ palynologists to study pollen samples taken from bores during oil exploration work. These pollen samples, by providing clues as to the circumstances in which sediments were formed, often serve as useful indicators of the likelihood of oil being discovered in particular drilling areas. Environment Of Moas Pollen extracted from the site of rich finds of moa bones in Pyramid Valley, North Canterbury, has thrown light on the environment in which moas lived in that area. Pollen found in the soil adhering to archaeological specimens from various parts of the world has been helpful in determining the age of the specimens. Studies of fresh pollen, too, have their practical applications The Botany Division has, in the past, carried out an investigation of seasonal changes in the pollen content of the air. This study provided useful information for medical workers concerned with allergies such as hay fever. The division has at various times undertaken studies of pollen in honeys. Identification of the pollen types indicates which kinds of flower the bees were visiting, and makes it possible to detect any misrepresentation as to the source of the honey. Recently, by helping with the analysis of pollen loads on the legs of native bees, the Botany Division assisted Crop Research Division workers to determine the feeding and nector-gathering habits of these bees, and thus to assess their importance as crop pollinators. Solving Crimes Palynology has even been used in establishing the facts of at least one murder—this being a Swedish case in which the pollen contained in dirt from the victim’s clothing was used to clear up the question whether the murder was actually committed in the place where the body was found. Dr. Moar’s studies so far have shown that in the moun-

tain valleys of Mid-Canterbury the sequence of changes in the post-glacial period was first to an open grassland phase; then to shrubland; then to a mixed growth of shrubs and forest trees, including totara, metai and miro: and finally to a forest of beech. Interpretation of these changes in terms of climate, soil conditions and other factors can provide a key to understanding of the processes by which the vegetation has reached its present state. Pollen diagrams may throw light on such matters as the rate of migration of tree species from one area to another.