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Tuatara aims to stimulate and widen interest in the natural sciences in New Zealand, by publishing articles which (a) review recent advances of broad interest; or (b), give clear, illustrated, and readily understood keys to the identification of New Zealand plants and animals; or (c), relate New Zealand biological problems to a broader Pacific or Souther Hemisphere context. Authors are asked to explain any special terminology required by their topic. Address for contribution: Editor of Tuatara, c/o Victoria University of Wellington, Box 196, Wellington, New Zealand. Enquiries about subscription should be sent to: Business Manager of Tuatara, c/o Victoria University of Wellington, Box 196, Wellington, New Zealand.
is the journal of the Biological Society, Victoria University of Wellington, New Zealand and is published three times a year. Editor:
The Problem of keeping information from books and papers available for easy reference is familiar to specialists in most fields, and most are familiar with one indexing system or another which helps with the problem. The better known systems, however, have various shortcomings. They may require for their maintenance more time and concentration than is justified, or they may fail to yield information for want of recollection of some key word, or they may not be versatile enough to accommodate changing needs. Computers suffer from the first disadvantage, the alphabetical card (library) catalogue suffers from the first or second or both, and the edge-punched card index from the first and third.
A system which has none of these disadvantages and which is cheap to operate is the ‘optical coincidence’ system. It provides a cumulative index to information on any subject whatsoever; it provides with little effort, an unlimited degree of cross-indexing and it can be operated by untrained personnel of average intelligence. It employs standard index cards (5 × 3 inch or 8 × 5 inch) which need not be specially printed, though printed cards are easier to interpret.
The equipment needed for the operation of the system is illustrated in figure 2. A wooden frame is constructed so that index cards of the chosen size fit accurately into it. A metal guide sheet the same size as the cards is cut from perforated copper or zinc, and painted or etched in such a way that the holes in it can be identified as a numerical series reading from left to right along the rows.
Fig. 1: A Printed Index Card
Items to be indexed (reprints, notes, specimens, etc.) are numbered consecutively in whatever order they come to hand. Suppose item number 1 is an article entitled ‘Blood Meal Identification in Aedes notoscriptus’ by M. Foot. The words ‘blood’, ‘Aedes notoscriptus’, ‘Foot, M.’, and other such relevant headings as ‘immunodiffusion’, ‘serology’, ‘Culicidae’, are each written on a plain index card (or a printed card, fig. 1), the cards are arranged face-up and stacked in the wooden frame. The metal guide-sheet is then placed on top of the cards, and a hole is drilled through the guide sheet perforation number 1, and on through every card in the stack. The cards are then
As further items are processed, the card index grows and comes to contain an increasing variety of words. It then becomes possible to index later items by re-using cards from the existing index, only writing new cards for words that the index does not yet contain. Many cards will soon have more than one perforation, and some cards which are applicable to many items will carry many perforations. Such cards as ‘New Zealand’, ‘technique’ and ‘survey’ might be of this kind.
At its simplest the retrieval of information involves selecting some card from the index, interpreting (with the aid of the metal guide sheet) the numbers represented by its perforations, and consulting the items to which these numbers refer. Thus in the example cited above the card ‘Aedes notoscriptus’ might have three holes, say in the locations 1, 749 and 1305, and the three articles carrying those serial numbers will all have information on that species.
If, however, the card referred to has many holes, the task of consulting all the items concerned becomes excessively laborious. Say, for example, the card ‘New Zealand’ was selected and that it contained 470 perforations. The forbidding task of consulting all these items can be reduced immediately if a second relevant card, say ‘immunodiffusion’ is taken, placed exactly on top of the first, and the two cards held up to the light. Light will then be seen through only those holes which are common to both cards (i.e. are optically coincident) and these holes will refer to all the articles concerned with immunodiffusion and with New Zealand. If the number of articles is still too great for convenience, a third card, say ‘Canis canis’, may be added to the other two, and the optically coincident holes in the three cards will then refer only to articles concerning immunodiffusion, dogs and New Zealand. The number of such articles would perhaps be more manageable. It is this capacity for successive refinement of the quest for sources of information which is the special virtue of the optical coincidence method.
The mechanics of the optical coincidence method may be handled in a variety of ways. For instance the metal guide sheet mentioned
Fig. 2: A metal guide sheet and two unprinted index cards ready to be placed in the wooden frame for drilling.
If holes are drilled out thoroughly, ordinary metalworking drills are quite satisfactory provided the stack of cards is compressed during drilling. A heavy paperweight is a help. The drill should not be less than 1/16 inch diameter if ordinary cardboard cards are used, nor should it be larger than 5/64 inch diameter if the cards are to accommodate 100 perforations to the square inch. With ordinary cardboard there can still be some tendency for adjacent perforations to coalesce, and there is a considerable advantage in using plastic-impregnated cards.
In filing the index cards alphabetically, the usual guide cards or tags are used to aid rapid location of the card required, and markers may be used to facilitate the return of cards to the index.
During indexing of the first fifty or so items a good deal of time is spent in writing cards for the alphabetical index, but as the index grows, more and more of the appropriate cards will be found already in the index so the effort involved in maintaining the system becomes less as the index progresses. Similarly the number of cards in the index is soon overtaken by the number of items filed. One such system, which contained 8,000 reprints, used only 1,500 index cards.
The number of cards that can be used in reference to a single item is actually unlimited. Even the length of the drill imposes no limitation as the cards can be drilled in several lots. (When drilling deep stacks, care must be taken to keep the drill upright.) It is therefore possible to index review articles and monographs under every species mentioned in the text, and for no more effort than writing the name of each species on a card. Cross reference on such a scale is a major advantage of optical coincidence over other systems.
Since every card in the index can be used as a template for drilling any number of duplicates of itself, the whole index can be reproduced quickly and accurately for the use of substations or agencies which have access to a central reprint collection, library or other information source. If it were desirable, every member of a research institution could be issued with a ready-made index to the contents of the library.
Though the capacity of each card is considerable (Miller's Bibliography of New Zealand Entomology’, which contains about 3,400 references, could be accommodated on 8 inch × 5 inch cards),
Optical coincidence is a cheap, effective and manageable system which provides a cumulative cross-referenced index to information on any subject. There can be few specialists who would not benefit from using it.
Botany Department
Electron Microscope Unit, Victoria University of Wellington.
Microns.In July, 1970, while examining water moulds trapped on boiled hemp seed from pond water collected at Otari Plant Museum, Wellington, the attention of one of us (J.E.S.) was arrested by the activities of a number of spiral micro-organisms so large that their movement could readily be followed at a magnification of 100X in the light microscope. These organisms moved swiftly, rotating as they went, until striking an object (e.g. a fungal hypha) on which they then reversed to continue as before. Periodically they came to rest and the number of spiral turns could be counted — some 2-3. Negative staining with nigrosin showed morphology clearly (Fig. 1) and staining with Leifson's stain (1951) readily demonstrated a single flagellum at each end (Fig. 2). When stained with methylene blue conspicuous metachromatic granules (volutin) were evident (Fig. 3). Movement was studied under phase contrast: the organisms darted back and forth, rotating as they went, but the body remained rigid. When at rest the flagellum moved slowly backwards and forwards without showing any wave motion. There was nothing to suggest that the flagellum was compound. Because of the large size (15.8 mic.
It obviously belonged to the family Spirillaceae of the order Pseudomonadales because the spiral axis was rigid and it possessed polar flagella. Dobell, in 1912, described a spiral organism from water from the river Granta near Cambridge, England, which he placed in the new genus Paraspirillum. It averaged 15 mic. × 1.5-2.0 mic., had a single flagellum at either end, numerous volutin granules, a definite nucleus and tapered towards the ends. It was only encountered once. Our organism resembled Dobell's organism in possessing a single flagellum at each end but it lacked a conspicuous nucleus (no bacterium possesses a true nucleus) and it did not taper towards the ends. It seemed more likely to belong to the genus Spirillum. Migula, in 1900, separated this genus from other spiral bacteria on the basis of motility by means of a tuft of polar flagella.
Spirillum volutans. Negative stain.
Spirillum. He placed those species with a single flagellum in the genus Vibrio. Williams and Rittenberg (1957) described six species of the genus Spirillum as having a single flagellum in flagellar stained preparations. In phase contrast observations of living material of the larger species only a single flagellum could be seen. Some time later Williams and Chapman (1961) made an electron microscope study of some twenty-six species and showed that in all, with one possible exception, the apparently single flagellum is in fact compound — a fascicle of many flagella. In a comparison of many flagellar staining methods they found that Leifson's method gave closest agreement with the findings obtained by electron microscopy.
Spirillum volutans. Leifson's stain showing flagella.
Spirillum volutans. Methylene blue stain showing volutin granules.
Water was collected from the pond at Otari Plant Museum in a glass vessel. This was distributed in pyrex petri dishes and baited with boiled hemp seed. Incubation was at room temperature (18-22° C.). The larger spirilla were present in quantity after a few days.
A drop of incubated pond water was placed on a clean microscope slide and a smear made and dried. A drop of 10% nigrosin was then placed at one end of the slide and drawn across the smear with the edge of another slide.
New microscope slides were dipped in 95% alcohol and flamed. They were then placed on a staining rack and a small drop of incubated water containing the organisms was placed on the slide with a pipette or loop. The water was allowed to evaporate. The slide was flooded with the stain (equal parts of soln. A, B and C below) and allowed to act, times varying from 2 to 6 minutes. It was gently rinsed off with tap water. The slide was then flooded with methylene blue for 5-10 minutes, washed in water, dried in air and examined. The cells stained blue, the flagella red. We found the best time for staining was 3 minutes.
Equal quantities of solutions A, B and C were mixed together before use.
Two hundred mesh grids were covered with a vacuum evaporated carbon film and allowed to dry. Specimens were pipetted off from the culture and a small drop placed on a standard microscope slide. The prepared grid was then gently lowered into the surface of the drop, withdrawn, and the adhering material allowed to dry.
Spirillum volutans. Electron micrograph showing a fascicle of flagella which appears to be spirally twisted.
Negative staining as described by Brenner and Horne (1959) was used. A 2% solution of phosphotungstic acid (PTA) in water was prepared and pH adjusted to a neutral value of between 6.8 and 7.4 by adding N-KOH. A small drop of the resulting potassium phos-photungstate (KPT) being then placed on a glass microscope slide and the grid lowered on to the surface of the drop and allowed to rest for one minute. After washing in distilled water and drying, the grid is ready for use in the microscope. Electron microscopic studies were carried out with the Zeiss EM 9A electron microscope and the included electron micrographs were made with this instrument.
Five different spiral micro-organisms were studied in the electron microscope and an attempt was made to relate findings to those of the light microscope. It has been possible to identify with certainty only two or the organisms. The large organism to which our attention was first drawn is identified as Spirillum volutans (Figs. 1-5); another, not seen in the light microscope, is identified as Leptospira biflexa (Figs. 6 and 7). These are described in detail below.
Spirillum volutans. Electron micrograph showing individual flagella.
Leptospira biflexa. Electron micrograph showing characteristic hook at one end and tight spiral coil.
Leptospira biflexa. Electron micrograph showing axial filament.
The other three organisms comprise: (1) A large organism (29.1 mic. × 0.8 mic.) which spiralled as it moved but appeared to flex and did not have demonstrable flagella in phase contrast. However, in Leifson stained preparations a number had a flagellum at one or both ends. The flexing motion combined with spiral shape is characteristic of the spirochaetes but the possession of flagella and movement by rapid spiralling is characteristic of the Spirillaceae. Further studies are necessary before any conclusions can be reached (Fig. 8). (2) A small organism (2.3 mic. × 0.5 mic.) with a single flagellum at each end demonstrable only in the electron microscope (Fig. 9). This would be excluded from Spirillum if Giesberger's ideas are followed and may belong to the genus Vibrio. Vibrios are generally ‘comma’-shaped but the progeny may remain attached, forming spirals. Also, according to Begey's Manual (Society of American Bacteriologists, 1957) the borderline between straight rods found in Pseudomonas and curved rods found in Vibrio is not sharp. Further studies are necessary to identify this organism with confidence. (3) The small curved rod (2.5 mic. × 0.3 mic.) shown in Fig. 10 appears to be attached to a bacterial cell. Recently Stolp and Starr (1963) have described a new genus Bdellovibrio for a predatory, ectoparasitic, and bacteriolytic micro-organism. Our photograph is strongly suggestive of such activity. No flagellum can be seen.
Spirillum volutans. In the electron micrographs the apparently single flagellum seen in light and phase contrast appears as a fascicle of some 20 individual strands. There is also the suggestion that this is spirally coiled (Fig. 4). No basal granules can be seen at the origin of the flagella. These findings agree with those of Williams and Chapman (1961).
Leptospira biflexa. Only two species of Leptospira are described in Bergery's Manual; L. icterohaemorrhagiae representative of the
L. biflexa representative of the saprophytic species. Our organism shows clearly the very fine coil and hook (at one end only) which are characteristics of the genus Leptospira (Fig. 6). It measures 8.2 mic. × 0.18 mic. The single axial filament can be seen wound round the main coils of the organism. The point of attachment can be seen in Fig. 7. Holt and Canale-Parola (1968) have shown some excellent electron micrographs of Spirochaeta stenostrepta, a related organism, in which the insertion of the axial filament is clearly seen — the insertion disc. They also demonstrated, for the first time, helical elements in the protoplasmic cylinder but we have not seen these in Leptospira.
The application of electron microscopy has shown the single flagellum of Spirillum volutans, seen in light and phase contrast studies, to be compound. The axial filament of Leptospira shows up clearly. Further work is necessary before the other three organisms can be identified with certainty.
Spirillum volutans, as here described, is an excellent organism for demonstrating the spiral form, motion, flagella and volutin to students of microbiology. We have based our identification on data given in Bergey's Manual. However, there is still a need for further investigations in connection with species of the genus Spirillum, particularly
Spirillum to lose their spiral curvature, appearing as straight rods, making it difficult to distinguish the genera Pseudomonas, Vibrio and Spirillum. We have not yet grown any of our organisms in pure culture. Dobell's Paraspirillum remains a puzzle — it is an anomalous organism since no bacterium is known to have a clearly defined nucleus.
We are grateful for Professor V. B. D. Skerman's comments on electron micrographs which we sent to him.
Apart from collating recent advances in dynamic global meteorology, oxygen isotopic ratios, solar cycles, bog recurrence surfaces, glaciology and dendrochronology, this review centres on New Zealand literature on climatic change. The review is limited to the last 1,000 years in order to provide some basis for establishing a time control of processes of structural and compositional change in the current vegetation soil systems.
The essentially dynamic and youthful nature of New Zealand vegetation and soils has, for many years, been apparent in descriptive studies (Cockayne 1928, Raeside 1948, Holloway 1954, Nicholls 1957). In the absence of any direct evidence of climatic change, many indirect and often ecologically tenuous inferences have been drawn from the vegetation and soils to explain maladjustment of populations, soils out-of-place with their present environment and discontinuous distribution of vegetation types.
Recently there has been a shift in emphasis from wholly climatic causes to the recognition of other factors, notably catastrophes of various kinds (Cumberland 1962, Fleming 1963, Molloy 1968, 1969). Climate, from this point of view, is considered an ‘intellectual concept’. It is the day-to-day realities of weather that are said to matter, rather than the climate of the free atmosphere evaluated in yearly means (Cumberland 1962).
It is unfortunate that recent reviews of climatic change in New Zealand have not involved the advances made in the understanding of dynamic meteorology, solar cycles and isotopic composition of snow and speleothems, e.g. stalactites, stalagmites.pers. comm.).
Antevs (1955) and Deevey and Flint (1957) considered that long-distance climatic correlations could be made only on the basis of inferred long-range temperature shifts. Recorded moisture changes were considered to reflect local geographic factors and to be therefore not useful for long-range correlation purposes. Most of the recent research on oscillations in solar activity and oxygen isotopic concentrations have had a temperature basis. As a result, the concept of
In sites of deposition, for example peats, varves, pollen profiles or in the ecological response to climatic change, for example forest composition, high water tables, lowered timber lines, there may be a considerable lag-period. This lag may vary from place to place and often be actually greater than the standard error of a date (Karlstrom 1966).
The climatic cycles postulated for the last 1,000 years were considered by Willett (1953) and Lamb (1959) to represent ‘alternate equatorward and poleward displacement of prevailing storm tracks’. In middle latitudes, such as New Zealand, this resulted in an alternation between warm-dry and cool-wet climates, whilst the alternation of warm-wet and cool-dry climates were characteristic of higher latitudes. Karlstrom (1966) and Yamamoto (1966) came to similar conclusions in a discussion of glacial-pluvial cycles and thermal advection.
Yamamoto (1966), Bray (1965, 1968), Johnsen et al (1970) confirmed a positive relationship between temperature and apparently regular solar-activity cycles, using botanical, geophysical, glaciological, geological and historical evidence. The ‘little climatic optimum’ of A.D. 1000-1300 and the ‘little ice age’ from A.D. 1600-1750 were both most apparent in the solar activity indices (Bray 1968) and ice-core data (Johnsen et al, 1970).
The detailed meteorological and historical data of Lamb (1965, 1966) were generally synchronous with the above research on extraterrestrial activity. Lamb et al (1966) described the period A.D. 1000-1300 as probably warmer and drier, in summer particularly, than any period since 1000 B.C. Lamb (1965) called this the ‘warm Mediaeval epoch’. He explained it meteorologically as a more frequent influence of the subtropical anticyclones extending over temperate Europe. ‘Then, as in the period 1900-1940 there was a greater frequency of westerly and anti-cyclonic westerly weather in Britain than in any other century.’ Lamb et al (1966) also considered that no cold period as measured by glacial advance, comparable with A.D. 1500-1700, had occurred since 8000 B.C. unless that of 500 B.C. They, Bray (1965) and Suess (1965) stated that most of the evidence had well established that the C14 variations in the atmosphere strengthened archaeological, botanical and glacial indications of a sharp climatic deterioration between A.D. 1300 and 1600.
Although annual rainfall was apparently lowest in the period between A.D. 1550 and 1700, the difference as regards soil moisture was probably offset by less evaporation and wetter summers (Lamb, 1965). This is evident from ‘recurrence surfaces’ — stratigraphic positions where peat accumulation recommenced in bogs throughout the Northern Hemisphere (Granlund 1932, Godwin 1954, Lundquist 1962, Nicholls 1969). All recurrence-surfaces restarted growth soon after A.D. 1200 after having ‘no-growth’ periods of 300-400 years duration.
From glaciological evidence, Porter and Denton (1967) termed the period from about A.D. 1300-1800, the ‘Neoglaciation’. They and Heusser (1966) extensively reviewed the evidence of glacial fluctuations throughout the world, particularly in the western United States of America, in the last 1,000 years. Data came from many historical records, C14 dates, dendrochronology and lichenometric dating of moraines. Porter and Denton (1970) reviewed the worldwide glacial recession beginning in the late Nineteenth Century and continuing to the 1940's. This closely coincided with a distinct global warming trend that led to an increase in world temperature by as much as 1.0°C. Yamamoto (1966) demonstrated a very close agreement of glacial fluctuations with the sunspot curve and the curve of rainfall in Korea from A.D. 1600 to the present.
The caution with which glaciological data must be treated has been noted by Aushmann (1966); ‘right at the margins of existing glaciers only quite drastic climatic variations are likely to have left a geological (moraine) imprint. The validity of global climatic correlation has been repeatedly questioned. But parallel glacial moraine sequences at far corners of the Pacific Basin afford growing confidence.’
Tree ring growth rates have been used by Antevs (1938) and Schulman (1953) in conjunction with lake-levels and run-off records in the intermontane basins of the western United States of America to demonstrate the time-distribution of wet and dry periods in the last 800 years. Schulman considered that the Thirteenth Century was very dry but became wet, with frequent storms in the Fourteenth Century.
Fluctuations of timberline have long been indicative of climatic change. In Canada, Brink (1959) demonstrated that current forest is invading alpine grassland at higher altitudes, where snow cover is diminishing. This could be related to the global retreat of glaciers and increasing temperatures since late last century.
The hypotheses of van Post (1946) and Harris (1949) that during the last 700 years, beech (Nothofagus) forest was replacing podocarp forest, in response to changes in climate was disputed by Walker
Holloway (1954), Wardle and Mark (1956) and others attributed the present forest/grassland boundary in parts of New Zealand, which is pedologically out-of-phase with what it was 800 years ago, to fire. These fires were made more effective as a result of climatic changes less than 2,000 years ago (Holloway). Their work, in part, supported the earlier conclusions of Raeside (1948) who interpreted anomalies in vegetation and soil in relation to the present climate. Raeside considered that between the Seventh and Thirteenth Centuries A.D., climates were warmer and wetter than at present. On pollen evidence, Moar (1970) confirmed widespread vegetation changes in Canterbury in the last 1,000 years, attributing them to fire-induced de-forestation, whilst noting that this did not invalidate the climatic change hypothesis.
Molloy (1969) considered that the climatic shift described by Raeside (1948) and Holloway (1954) from indirect evidence, was hard to trace. In agreement with Cumberland (1962), Molloy favoured catastrophic phenomena, particularly fire, as more likely to have caused the past vegetation changes in New Zealand. The effects of early fires has been extensively studied, for example Cox and Mead
Cumberland's (1962) and Molloy's (1969) criciticism of palaeoclimatic factors evaluated as yearly, decade, or fifty-year means (e.g. Lamb 1965) being used to infer ecological change are invalid. The utility of grouped means lies in their indication of climatic extremes; the 2°C. amplitude between A.D. 1000-1300 and A.D. 1600-1750 periods are the climatic levels critical to major species in vegetation. Regeneration gaps, changes in timberline and peat accumulation require climatic factors to be continually either above or below critical levels. The most useful way of expressing palaeo-climatic data is to group data with similar quantitative attributes.
Recent work by Hendy and Wilson (1968), Hendy (1969) on the isotopic chemistry of C14 dated speleothems has made a great contribution to New Zealand-based interpretations of global palaeoclimatic data. Hendy obtained the ratios of the oxygen isotopes O16 and O18, the fractionation of which was temperature dependent. He concluded that for the last 1,000 years:—
throughout New Zealand, variation in O18 in speleothems was constant in time and quantity. This implied New Zealand-wide synchroneity of considerable climatic change in the last 1,000 years.
Palaeo-temperature changes deduced from the isotopic ratios of the speleothems were constant in time and quantity with the mean temperature deduced for central England (Lamb 1965).
On historical and dendrochronological evidence, J. R. Bray (pers. comm.) has recently demonstrated the synchroneity of glacial activity in southern New Zealand and British Columbia in the last 1,000 years. Other glaciological evidence agrees broadly with the trends noted by overseas research. pers. comm) described glacial advances at Mount Cook, from moraine dates occurring about A.D. 1200 and in the Fifteenth, Seventeenth, Eighteenth and late Nineteenth Centuries. Burrows somewhat disputed the ‘little ice age’ on the basis that there was no overall glacial pattern in New Zealand. However, moraine evidence from the Cameron Glacier and lichenometric dating of the Mueller Glacier moraines (Burrows and Lawrence 1965), suggested a maximum terminal moraine at both glaciers forming about A.D. 1750. The same authors and McKellar (1955) also noted a well-developed morainal surface, consistently dated at about A.D. 1890. The observations of Gage (1966) on glacial activity in the South Island are particularly relevant to the problems of palaeo-climatic interpretation from indirect
Park (1970) evaluated a Maori oven found under silver beech forest at 2,600 ft. in the Tararua Range in terms of palaeo-climatic change. The oven, dated at A.D. 1227 ± 40, was evaluated in conjunction with soil stratigraphy, soil air/water balance, pollen analysis, and radial growth rate and age structure of Halls totara and silver beech populations. The oven suggested an appreciably warmer and effectively seasonally drier period than the present at the time of its construction.
The 1°C. change associated with the global temperature increase from 1890-1940 was quite pronounced throughout New Zealand (J. Finkelstein pers. comm.). Mean temperature rises of 1.21°C. and 1.10°C. occurred in Auckland and Dunedin respectively. From 1925-1950 the mean annual trend of temperature change for New Zealand (J. Finkelstein pers. comm.) were very similar to those of western United States of America (Heusser 1966). The long-term fluctuations of rainfall in the North Island from 1898 to the present day (de Lisle 1961) also show many similarities with the global tropical and subtropical synthesis of Kraus (1958).
In 1963 Elder published evidence of a general imbalance in mountain beech forests (Nothofagus solandri var. cliffortioides) in the Ruahine Range except at the lower altitudinal end of its range. The short life span of mountain beech restricted any environmental change to within the last 200 years. At the head of the Maropea River, Elder noted evidence of a former timberline some 200-300 ft. higher than at present. He considered that in the last 200 years there has been a retreat by mountain beech to lower altitudes and drier sites, suggesting that the climate has been getting progressively cooler and wetter. Throughout the northern and central Ruahines there is a downward and outward movement of beech forest into other types, including a retreat of red beech (Nothofagus fusca) and its replacement by mountain beech. Observations in red beech-silver beech forest east of Lake Taupo in the northern Kaimanawa Range by this author in 1969 suggested that the older senile red beech-silver beech canopy was being replaced through successive windfalls, by younger trees of solely silver beech. Throughout New Zealand silver beech appears to be a species of lower nutrient requirements and higher moisture tolerance than red beech. Such vegetation changes are supported by pollen evidence from Mokai Patea in the Western
McQueen (1950) postulated a lowering of timberline by about 600 ft. to account for a lack of beech regeneration on silver beech sites on Mts. Quoin and Reeves, Southern Tararua Range. Pole stands of beech of Mt. Reeves, in sites normally dominated by red beech, had a higher proportion of silver than red beech. Reid (1948) and McQueen (1950) described recent changes in compositional structure of red beech-silver beech forest; the former relating changes to regeneration after excessive windthrow. In both cases silver beech was regenerating at the expense of red beech. Holloway (1954) described compositional changes of similar nature in the South Island. McQueen (1950) discussed the observation of
In contrast to the above vegetation changes, Wardle (1962) demonstrated an advance of silver beech into subalpine scrub and tussock grassland in the Southern Tararua Range, and a contraction in the territory of Dacrydium biforme in the northern part of the range. Ecologically it is likely that both the phenomena described by Wardle are in response to a recent change towards a warmer and sunnier climate, attributable to the well documented global warming since late last century. Wardle's results lacked any dates of forest advancement or contraction. Druce and Atkinson (1959) dated a timberline line advance of silver beech forest on Mt. Alpha to c.A.D. 1906.
The increasingly demonstrated synchrony of climatically induced events throughout New Zealand (Wardle 1964, Hendy 1969), within the Pacific Basin (Karlstrom 1966) and globally (Bray 1968, Hendy 1969) suggest that considerable changes in climate have, in fact, occurred in the last 1,000 years.
The argument against any climatic changes in the last 1,000 years being ecologically significant would appear to be a function of the lack of direct evidence of their occurrences. The indirect effects, forest instability and out-of-phase vegetation and soil boundaries, are more often than not explicable by catastrophic phenomena (Molly 1969).
Lamb et al (1966) noted the prominence of the warm, dry summers of the period A.D. 1100-1300 and the cold period A.D. 1550-1700 in the climatic record of the last 1,000 years. Between these two intervals there was a maximum temperature decline of 2°C. Lamb (1965) described the significance of this change to anthropogenic
If forest vegetation is to be used to assess climatic change (Holloway 1954, Nicholls 1957) there is need for a far greater understanding of comparative vegetation and soil dynamics between forest, scrub and grassland systems. The concepts of vegetation/soil system development, steady-state, post steady-state, species age/tolerance (Becking 1969) and size class/age stratification (Goff 1968) have received little attention in New Zealand. Similarly, a quantitative knowledge of upland climates, apart from the work of Mark (e.g. 1965) and Coulter (1967) and suitable archaeological evidence of climatic change, particularly in upland areas, is lacking in New Zealand.
I would like to thank Dr. J. R. Bray for helpful discussion and Dr.
Diurnal refers to the light period. Daily refers to the 24-hour period.In his Paper concerning the activity responses of a diurnal and nocturnal lizard to light and temperature fluctuations, Evans (1966) points out that diurnal
Park (1940, 1941) subdivides rhythmic phenomena into two main categories:
‘exogenous’ rhythms — direct responses to environmental changes. They do not persist when conditions are kept constant;
‘endogenous’ rhythms — innate rhythms which continue, for a time at least, under constant conditions.
In the light of the great store of recent descriptive work, most workers are in agreement that daily rhythms are endogenous (Pittendrigh, 1960) and that although they are not necessarily a direct response to environmental changes, are frequently correlated with them (Cloudsley-Thompson, 1961; Hamner and Enright, 1967). Cloudsley-Thompson (1961) considers that under natural conditions, several external factors are probably active at the same time, generally with one in particular being the ruling factor of an animal's periodicity.
Brown and his co-workers (1954-6) believe that some extraneous force such as cosmic ray showers, barometric pressure, conductivity or ionisation of the atmosphere or changes in the earth's geomagnetic field may be involved as synchronisers of natural rhythmicity with the environmental day-night cycle. Work by Pittendrigh (1961), however, has led him to believe that light and temperature are the only two variables known to be coupled to the living oscillation. Although there are some indications (Aschoff, 1958) in favour of Bruce's (1960) theory that some other type of periodically repeated stimulus may cause a persistent rhythm to become synchronised with the entraining cycle, Aschoff (1963) considers that there has been no adequate demonstration of an effective zeitgeber (phase-setting factor) other than light and temperature. Of these two, he further considers, as does Cloudsley-Thompson (1961), that light is the most common and most important factor.
Evidence for the endogenicity of rhythms comes from studies which show that daily rhythms persist with periods other than those of environmental factors when organisms are placed into constant conditions (Roberts, 1960; Sollberger, 1965; Hamner and Enright, 1967; Menaker, 1969; and others). Experimental results have indicated that although perfect constant conditions are probably impossible to establish in the earth environment owing to the difficulty in excluding such variables as barometric pressure, magnetic field and ionisation of the air (Menaker, 1969), constant levels of light intensity and temperature are sufficient to demonstrate the endogenous nature of biological rhythms (Pittendrigh and Bruce, 1957; Bünning, 1958; Pittendrigh, 1960; Menaker, 1969). A major property of biological rhythms under these conditions is the deviation of period length from the exact 24-hour cycle of the natural day (Lohman, 1967), hence the term ‘circadian’, derived from the Latin (circa = about, and dies = a day) (Halberg, 1959).
Further evidence for endogenicity comes from the results of several workers (Harker, 1953; Aschoff and Meyer-Lohmann, 1954; Pittendrigh, 1954; Folk, 1955; Hoffmann, 1955) who have initiated circadian rhythmicity in laboratory-reared organisms which had never experienced environmental rhythms of 24-hour periodicity.
Marler and Hamilton (1966) and Menaker (1969) point out that individuals within a given species will exhibit small differences in the length of the natural period. Hoffmann (1957), for example, showed that lizards hatching in constant darkness and temperature had individual differences in the period of their activity rhythm. This is strong evidence against external control of the period of the rhythm since all individuals were subject to the same conditions.
The efficacy of light as an entraining agent can be demonstrated in an environment with no temperature periodicity. Under an artificial light: dark (12: 12) regime at constant temperature, Roberts (1962) found that the rhythm of the cockroach always attains a steady state whose period is 24 hours and whose phase is such that activity begins at, or shortly after, the light-to-dark transition. The primary onset of activity is closely correlated with the ‘dusk’ transition.
Concerning the natural period of the circadian oscillation, Jegla and Poulson (1968) consider that where this differs from 24 hours, factors such as dawn or dusk provide the proper phase relationship between the circadian periodicity of the species and its environment; that is, the rhythm is entrained each day as the photoperiod changes. Cloudsley-Thompson (1961) points out that synchronisation with environmental periodic changes cannot be achieved both at dawn and at dusk, as the time of each of these is altering. He considers that the synchroniser tends to be the dusk, in the case of nocturnal forms, dawn in that of diurnal forms. Bennett (1954) noted that during
Hyphantria cunea to be promoted by the change from light to dark, point to the effectiveness of dusk as a phase-setting factor. Kavanau (1962), on the other hand, found that for deer mice, which are nocturnal, dusk is sometimes ignored, the dawn changes usually being the more compelling!
Much experimental work has been done under constant light conditions. Such conditions may positively or negatively affect the amplitude of the rhythms, and may also affect the period length (Harker, 1958). Roberts (1960), for example, although finding no obvious correlation between period length and intensity of illumination, in two species of cockroaches, did note that the period was markedly lengthened in constant light as compared with constant darkness. Whereas the activity period of the white-footed mouse is also lengthened (Johnson, 1939), that of the lizard Cnemidophorus sexlineatus is shortened in constant light (Barden, 1942).
In 1960, Aschoff formulated the ‘Circadian Rule’ that in light-active animals: (1) spontaneous frequency; (2) the ratio of activity time to rest time, and; (3) total activity, all increase with increasing intensity of continuous illumination. Harker (1964) pointed out that the intensity of the light in a constant environment has a considerable effect on the length of the free-running period. Correspondingly Aschoff's hypothesis, which has been extended to include intensity effects and is now being widely called ‘Aschoff's Rule’, states, in its modified form, that an increase in the intensity of constant light causes a lengthening of the period for a nocturnal organism and a shortening of the period for a diurnal organism (Hoffmann, 1965). The rule clearly holds in those cases cited by Aschoff (1960). These include the activity rhythms of chaffinches and the lizard Lacerta sicula (Hoffmann, 1960). Similarly flying squirrels and house mice, which like deer mice are nocturnal, show an increased period length in brighter light (Aschoff, 1960; Hoffmann, 1960, 1965), as does also the mosquito, Aedes aegypti, which also shows corresponding increases in its level of activity (Taylor and Jones, 1959).
Although the validity of ‘Aschoff's Rule’ has been demonstrated in a wide variety of species (Hoffmann, 1965), rhythms of other species, which have been studied over long periods of time, show that there are exceptions (Harker, 1964). Some of the more recent studies demonstrating the latter include those of Imlay (1968) and Youthed and Moran (1969), who worked with the clam (Elliptio complanatus) and larvae of the ant-lion respectively. Marler and Hamilton (1966) state that diurnal animals such as most birds react to increased light intensities in the same way as lizards, which,
Hoplodactylus pacificus), in which both species have been shown to disobey ‘Aschoff's Rule’.
During his work on Peromyscus, Johnson (1939) noted that light may have an inhibiting effect on the activity of a nocturnal animal. Munn (1950) recorded the same phenomenon in rats. Sufficient evidence from other work led Harker (1958) to write that light partially or completely inhibits movement and other activities in some animals. She noted also that although arthropods appear to be the only group from which the following effect is recorded, continuous darkness may also be inhibitory.
An important comment from Marler and Hamilton (1966) concerns the variable effect that lighting conditions may have on individual animals. Hoffmann (1957), for example, found a strong individual variation in period length in adult lizards (Lacerta sicula, L. agilis, L. viridis) measured under constant conditions.
Regarding the importance of temperature as a factor in daily activity Bünning (1931), Wahl (1932) and Kalmus (1934) found the period length to be remarkably independent of temperature under steady conditions. Later work has confirmed these early findings in a numbr of widely varying species, for example: tortoises (Cloudsley-Thompson, 1970); Perognathus intermedius (Stewart and Reeder, 1968); Bufo fowleri and B. americanus (Higginbotham, 1939); Uca (Brown and Webb, 1948); and Carcinus (Naylor, 1960).
On the other hand, studies of lizards (Hoffman, 1957) and many other species (Sweeney and Hastings, 1960) have consistently revealed small but distinct shifts in period length within certain ranges of temperature change. Bustard (1968) has found temperature above 25-26° C. delays initiation of evening activity of the nocturnal gecko, Diplodactylus vittatus, whereas a fall in evening temperature to below 13-17° C. greatly curtails evening activity.
Marler and Hamilton (1966) consider the relative temperature independence of circadian rhythms to be significant under natural conditions. They point out that if circadian rhythms serve primarily to concentrate appropriate behaviour at certain times of day, change with temperature would hinder accurate timing. On the other hand, as the rate of metabolic processes is so closely linked with temperature, it is surprising that rhythms are not also affected by temperature (Harker, 1958; Marler and Hamilton, 1966).
Although constant temperatures cause little change in period length, it has been found that a regular cycle of temperature change
Bentley, Gunn and Ewer (1941) showed that the activity rhythm of the spider beetle Ptinus tectus, though gradually lost in continuous illumination, could be reinstated by periodic exposure to high (23° C.) and low (17° C.) temperatures. Other species which become synchronised with temperature fluctuations include the lizards, Sceloporus magister (Taylor and Tschirgi, 1960) and Uta stansburiana (Evans, 1966). Hirai (1969) has found that a drop in temperature induces earlier eclosion in Hyphantria.
While temperature entrainment has, therefore, been well substantiated for such poikilotherms as insects and lizards, it has not been demonstrated conclusively for mammals (Stewart and Reeder, 1968). DeCoursey (1960) with flying squirrels, and Bruce (1960) with hamsters, were unable to find any evidence for temperature entrainment. One should note, however, that Browman (1943) and Calhoun (1944) have shown a temperature cycle to determine phase-setting in the rat.
Cloudsley-Thompson (1961) pointed out that in all organisms investigated up till then, there appeared to be a critical temperature at which rhythms cease. Furthermore, he contended that although the period of a rhythm may be relatively unaffected by temperature, its amplitude will show a normal physiological temperature dependence. Mark and Kayser (1949) found this to be the case in Lacerta agilis and L. muralis, as did the author with Hoplodactylus pacificus. Earlier, Higginbotham (1939), working with toads, had discovered that with an increase of 10° C., a doubling or tripling of the amount of activity occurred.
Harker (1958) showed that sudden large changes or very low temperatures can alter the period of a daily rhythm which is not temperature sensitive within a normal temperature range. Phase shifts are reported to occur in Uca (Stephens, 1957), and Periplaneta (Bünning, 1958), when the temperature is lowered to the 0-10° C. range for an interval of 12 hours or less.
Temperature and light may also have interacting effects (Marler and Hamilton, 1966). For example, Enright (1966) found that the extent to which the free-running activity of the house finch is retarded by low temperatures, depends on the intensity of the constant light.