551.506.8 DISCUSSION ON THE REPORT ON THE

PHENOLOGICAL OBSERVATIONS I N THE BRITISH ISLES FROM DECEMBER, 1943, TO NOVEMBER, 1944

March 14, 1945 In presenting the Phenological Report for 1944, Major H. C.

GUNTON illustrated by slides the features of the season under review and explained his reasons for attaching importance to the observation of the earliest plant in a station area, as well as of the plant selected for observation every year, which observers have been requested to record.

DISCUSSION Dr. C. B. WILLIAMS ’: I congratulate Major Gunton on the early appearance

of the Phenological Report. The variability of flowering date which phenologists are attempting to study has four levels at which it can be analysed. Variation within a plant ; between two plants growing side by side ; between two plants growing in the same district ; and between districts. In the past, most emphasis has been laid on the latter. I am glad to see that Major Gunton is bringing in evidence at some of the other levels, and agree with observations of the earliest as well as the selected plant.

I should like to suggest that in some convenient.locality, about 100 horse- chestnut trees should be mapped and examined e v q day during the spring, and further that separate observations should be made on different parts of the same tree (e.g., N.S.E.W. and top of tree). In this way, with a short intensive period of work, much valuable information would be obtained.

Another problem of great importance to phenology and requiring further study is a statistical one. In most problems of observation, the observations are scattered on either side of the truth and the true reading is probably not far from the average. But in phenology (apart from misidentification) all errors are in one direction, that of lateness. It is impossible to observe an event before i t happens, but i t is very likely not to be observed until some time after. This case of one-sided error requires further statistical study.

Mr. A. J. WILMOTT: I should like to congratulate Major Gunton on the early appearance of his Report. I think it advisable to cut out the late observations and let them go into the next year’s Report. I have tried to discover why Major Gunton thinks that the earliest date of seeing a flower would give better results, and it appears to be because he thinks that site characters are more variable than individual differences in time of flowering within the species. 1 think that, if you observe a standard individual, you can be sure of not missing the earliest date of its flowering, and that by departing from this practice avoidable difficulties would be created. If any observer seems to have selected a discrepantly early or late standard, i t would be better to ask that observer to select a standard the required amount earlier or later to bring the station into harmony with the others. The differences in flowering time within a species may be very wide. If you take the earliest observation, you are definitely observing an abnormality, for both first and last dates of flowering are the ,furthest from the “ n o r m ” and are therefore abnormal. So you can have both abnormal individuals and abnormal sites. One should aim to avoid

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REPORT ON THE PHENOLOGICAL OBSERVATIONS 27

both by having standard specimens for observation and by selecting normal sites a s little as possible subject to unusual variable shelter.

Mr. E. L. HAWKE : It seems a great pity that not more than about one per cent of the members of this Society attend the meetings specially arranged for the presentation and discussion of the Phenological Report. I feel sure that many more would come along if only they realised what a master of his subject Major Gunton is. In the discussions of previous issues of the Report during the last half-century or so, i t has been pointed out on several occasions by far-seeing speakers that while the observations collected by the Society might appear to be of no very great immediate value, they would undoubtedly prove their worth and utility in the course of time. For example, Mr. Bonacina stated, in his contribution to the discussion eleven years ago, that the Phenological Report " was becoming a repository of information for the inevitable day when important questions would arise concerning the reaction of living creatures to weather and climate." He added that the subject was one of great difficulty and required sound and well-balanced judgment.

I would submit that the '' inevitable day," then envisaged by Mr. Bonacina, has now arrived. The fact that British government departments, or institutions under their auspices, are seeking the co-operation of our phenological organisation seems to be sufficient evidence of this. Furthermore, I believe I am right in stating that Major Gunton has latterly been consulted from overseas in regard to intended phenological investigations. Two things are certain : first, that our Phenological Director has brought to bear on this very difficult and complicated subject " sound and well-balanced judgment " in the highest degree; second, that we are indeed fortunate to have him in charge of this important branch of the Society's activities. I personally have the greatest admiration for all the work he does on our behalf, and for the excellent Reports which he brings to birth so punctually year by year. I should like to compliment Major Gunton most wholeheartedly on the latest addition to the family ; it is. in my opinion, a child a t least equalling in merit any of its predecessors, and that is no small praise.

Can he tell us if it is known whether insects are induced to emerge from hibernation on a winter day by warmth, or by light, or by a combination of the two ? On page 5 of the Report before us, reference is made to Miss Marsham's statement that the male Brimstone butterfly has been observed in flight during January on only three occasions in her family's remarkable series of Norfolk records extending back to 1736 : those occasions were the 14th of the month in 1790, the 11th in 1846, and the 30th last year. I have had the curiosity to look up weather statistics of those two earlier Januarys. Like January, 1944, they were both, on the whole, much warmer than usual in south-eastern England ; but January 11, 1846, itself was about average as regards day temperature. The maximum reading a t Greenwich Observatory was 42' F., after a minimum of 36O F., and I suppose it would not have been very different in Norfolk. There had, however, previously been a long spell of abnormally genial weather for the season, just as there was before the premature appearance of the male Brimstone on January 30 last year. May i t perhaps be that the sleep of a hibernating butterfly becomes progressively lighter during such a spell of winter warmth until a t length the creature is continuously so near to the limit of consciousness that any burst of sunshine may suddenly wake i t and tempt i t to take wing even on a chilly day like January 11, 1846, with a maximum air temperature not much above 40' F. ?

May I ask Major Gunton one or two questions ?

28 REPORT ON THE PHENOLOGICAL OBSERVATIONS

Also, can Major Gunton say whether the great shortage of honey last year was associated with any particular meteorological circumstance or combination of circumstances ? (Added later.) I do not know whether the dearth of honey was general throughout the country, but i t was certainly acute in many central, eastern, and southern districts of England, where some bee-keepers reported tha t the season was among the worst in their experience.

Mr. L. C. W. BONACINA : After what Mr. Hawke has said, I can only say that I feel deeply sensible that the inevitable date has arrived, when vital issues are arising out of this phenological work. Major Gunton said in his Report that he was endeavouring to show the lines upon which he was working. I am quite certain he is working on the correct lines. We shall do well to remember that phenological observations are not simple, but are extremely compl‘ex and require a well-balanced judgment. Variability in individual plants of a species is very great and is not merely related to site and exposure, but is partly inherent, that is biological. Diagram 1 is a mine of information, but would be more valuable if it could be made a little clearer, with mare explanatory index. I t is difficult to decipher and clarification would increase the value.

Could Major Gunton ask Mr. Colquhoun to pay attention to the ripening of acorns from south to north of Britain ? My personal interest in this subject was aroused through repeated failure on September visits to Northumberland in the 1920’s and 1930’s to meet with ripe or ripenable acorns. I t is, however, a fact which I have substantiated by correspondence with well-known authorities that whereas in southern England acorns are ripened lavishly practically every year, this is only the case in northern England and southern Scotland in favourable seasons and in northern Scotland in very exceptional years in favourable situations. But, as I learn from Prof. Tansley, even if a crop of acorns matured but once in 50 years, i t would suffice to perpetuate the species. He points out that oak is undoubtedly native in the Great Glen, and along the shores of the Moray Firth and in the vicinity of Loch Broom in western Ross-shire, and that oak scrub exists as far north as lower Helmsdale in southern, Sutherlandshire.

Major H. C . GUNTON, in reply : Dr. Williams’s support for the additional observations which i t is hoped to obtain is noted with His suggestions for the intensive study of a group of trees will be borne in mind, but I know he realises that .we cannot ask our observers generally to undertake additional wcrk of this extent.

In reply to Mr. Wilmott ; my reasons for not wishing to confine observations to selected plants are given in the following extract from a memoFandum on this subject.

satisfaction.

Phenological Observations The following is an extract from the Summary of Conclusions in the

Phenological Report, 1943 :- The 1942 Report mentioned that, in the course of investigations into

average dates, it had become evident that, owing to the effects of site characteristics, there are considerable numbers of stations with which equafly and markedly early dates are associated, although such stations may be distributed over a large area, including several districts. It was also clear from the zone diagrams that there is less difference in date between groups of the same species, as a whole, in different zones than there is between the dates from stations in individual groups; the former difference may amount to a few days, but the latter to several weeks.

REPORT ON THE PHESOLOGICAL OBSERVATIONS 23

The differences in date within a single plant group, while attributable mainly t o site characteristics and to the incidence of weather as explained above in the discussion of Fig. A, para. (d ) , are doubtless due to some extent t o the rule whereby the response is observed year by year, of the same plant, with i ts own individual characteristics, as distinct from the first response of any plant in the area of observation.

I t will be instructive to note, over a period of years, the effect 01 observing the dates of both these responses and arrangements have been made for this t o be done, with the concurrence of botanical members of the Executive Committee.

(End of extract f r o m Pilenological Repor t , 1943) There have appeared to be great advantages in observing. year by

year. selected standard plants, and much has been learned from the dual methods of analysing and demonstrating the characteristics of a season, and the relations between stations, by plotting. in juxtaposition to the meteorological data , (a) the two earliest station records in a District, for each item, in comparison with the corresponding average earliest records, and ( b ) all the station records in the District for the same item.

I t has become apparent, however, that there are disadvantages in confining observations to standard plants, which militate against a correct appraisement of the characteristics of a station in relation to others and may even tend to give a false impression of the seasonal state.

(i) Even if the standard plants were all selected by experts, i t would be unlikely tha t they would correspond closely as regards their individual characteristics, their age and their environment, including shelter and the relationship between roots and sub-soil.

(ii) After the lapse of a considerable number of years, the response would differ and, in recent years, there must have been many instances of destruction of the standard. In the phenological gardens of the 3Linistry of Agriculture, there have been frequent nil returns due to the death of plants.

(iii) A difference in the characteristics or environment of two standard plants may, under the influence of \\.eather, result in a considerable and quite disproportionate difference in the dates of response.

(iv) From a slightly different angle ; while, using standard plants, the two earliest statiun records may, and probably do, serve as an approximation to the earliest dates in a District, the gap which so often occurs between these respoiises ;m(l those of the remainder of the stations, and the dispersion of the latter, may be misleading. The conviction has grown that to maintain the restriction imposed by the observation of a single plant, will hamper an extension of our investigations into the phenological characteristics of a station area and into the phenological-ecological relationships between plants and animals.

I n order that the reality of the points referred to above may be appreciated, extracts have been made from the Phenological Reports.

(i) There are a few places where there are two stations, e.g., at Exmouth-A (ii), 13a and 13b ; at Thetford-E, 18c and 18i ; at Kendal- F (ii), 27a and 27c. There are certain responses at these stations in respect of different plants, which are significant. The responses at the stations of each pair are liable t o differ both as regards date and order, although they refer, presumably, t o standard representative specimens in each case and do, in certain years, agree.

30 REPORT ON THE PHENOLOGICAL OBSERVATIONS

I t will be clear, by reference to the Tables in the Reports, that if, say, there had been no station 13b a t Exmouth in 1942, the date of response of Plant I X would have been taken as 164, whereas a, response of 19 days earlier could have been observed from another ” representative ” specimen, thereby affecting materially the phenological position of the station as regards that species.

It will also be evident that in any investigations, such as the damage done to oaks by the Green Oak Tortrix moth, the response of the standard tree might be much less important than the response of earlier trees in the immediate neighbourhood ; this difference might have amounted ta 13 days in 1944, at Thetford.

(ii) The comparatively few “ earliest dates ’’ which have so far been returned by observers, as requested in ‘‘ Notes to Observers ” in the 1943 Report, are shown in brackets in Tables 111, IV and V of the 1944 Report, and indicate various degrees of difference. Three of these stations are the subjects of the following notes.

Lowestoft-E, 26h (Table 111). It will be seen that some of the dates are for ‘‘ standard ” plants only, some for “ e;.sliest ” plants only (presumably because the I ‘ standard ” and “ earliest ” were the same), and some for both classes of date, between which there was little difference.

In this case all the dates are “ earliest.”

This is a late station (750 feet above sea level). Six “ earliest ” dates are given for five of which there are corresponding “ standard ” dates, and i t will be seen that the difference is very large in the cases of Plants I1 and 111, due, no doubt, to the cold spell in February-March.

With regard to cases in which i t appears that “s tandard” and “ earliest ” dates are very similar or identical. i t will be realised that this is bound to occur where there are only a small number, or single specimens, of a plant available.

It remains to suggest the most suitable procedure in order to obtain fuller and more reliable information.

( a ) Anything in the form of a general or average response is open to the objection that the estimated or calculated date may be in the centre of a cold spell and represent a phenological absurdity.

(b) The selection of several specimens, while quite suitable in the case of an investigation such as that a t Parkend. Glos., which includes the study of earliest, latest and intermediate specimens (vide Phenological Report, 1944). is not everywhere applicable, and previous efforts to obtain information relating to three specimens were unsuccessful. Incidentally the additional space which would be required for tabulation would present considerable difficulty.

(c) It is suggested that, for the present, the best policy will be to continue and intensify efforts to obtain the dual information specified in the opening paragraph of this memorandum, i.e., to continue the observation of “ representative ” (standard) specimens where they really exist, and learn as much as possible from them regarding the effects of their site characteristics, and to observe, in addition, the responses of “ earliest ” specimens, naturally selected, i.e., avoiding specimens such as occur in gardens or in contact with buildings, but accepting any responses in a natural site, with corresponding notes regarding shelter.

Llanfairfechan-F (i), 9f (Table 111).

Murton Appleby-F (ii). 30a (Table 111).

REPORT ON THE PHENOLOGICAL OBSERVATIONS 31

It‘is anticipated that the result of this policy would be the clarification of the true relationship between the responses of stations which would be indicated by group graphs considerably shorter, i.e.. with less deviation than those referring to “ standards,” and later, when averages have been established, the “earliest” dates could aIso be used to show a closer approximation to the earliest responses corresponding to different seasons than is possible at present.

In order that this investigation may be pursued with a reasonable prospect of success and with uniformity of method, it seems necessary that there should be personal contact with observers, and possibly the selection of a number in each District of those who are so situated that they could, and would, undertake the dual obsetvations, with the accompanying information desired, with a reasonable prospect of continuity and regularity. The uses to which the Phenologicat Report may be put can be classified

as follows :- (a) To study the responses of certain plants to the weather; for this

purpose a selected representative plant is the ideal to be aimed at. ( b ) To assess the relative position of different stations in different seasons.

In this connexion the earliest responses, as well as those of the selected plants, are desirable.

(c) For special researches of an ecological nature, such as those involving the appearance and activities of insects. In such cases the “ earliest ” date of plant response may be essential.

I am afraid that, even if Mr. Wilmott’s suggestion to adjust the selected plants were found to be practicable, i t would not entirely meet the requirements ( b ) and (c), while i t would adversely affect (a) inasmuch as existing averages would be disturbed.

I can see no scientific justification for ignoring the earliest specimens of flowers or foliage which may be associated with the earliest visits of beneficent or harmful insects. These are natural indices of the season up to that date; the response dates of specimens which respond later, owing to individual characteristics or site characteristics, or both, are frequently and largely influenced by a subsequent change of weather (eg., Murton Appleby responses quoted in the above memorandum).

In these circumstances, ‘the assessment of what may be termed a “normal” response would be difficult, and might be impossible, while the calculation of an average may, as pointed out in the’above memorandum, lead to a misleading result. I should add that while specific differences may contribute to differences in date, they cannot account for the differences in order which are of such frequent occurrence.

These and other facts summarised in the 1943 Report led to the decision to ask for the earliest response as well as the response of the selected plant, and I feel confident that this policy, combined with the establishment of closer touch with the observers, will lead to a valuable increase in our knowledge.

I am much indebted to Mr. Hawke for hisunfailing support and appreciation. I wish I could give a complete answer to his question about the emergence of insects from hibernation, but, in a case such as that to which he refers, a knowledge of all the local circumstances would be necessary. I think his conclusion is probably correct. but, as regards appearance on a chilly day, i t is possible that the insect had already been roused to activity on a preceding and warmer day. In connexion with this phenomenon, it may be of interest to recalI that hibermtion, which must be associated with winter in a liberal sense, or aestivation, associated with summer, is a state of torpor which enables

32 REPORT ON THE PHENOLOGICAL OBSERVATIONS

an animal to survive a season of unsuitability as regards weather or availability of food. There is an instance, in Greece, of a butterfly, the Large Tortoiseshell (which i; this country behaves like the Peacock or Brimstone)-emerging from the chrysalid in May and conserving its vitality throughout the heat of the summer and the cold of the following winter by a retirement which amounts to a period of aestivation followed without a break by a period of hibernation ; it is conjectured that the insect emerges from hibernation m February and that the life cycle is completed rapidly.

It appears that the shortage of honey in 1944, especially in the South- Eastern districts, was due mainly to the droughty conditions, which affect the quality of the honey and the ability of the bees to collect i t from the flowers.

Mr. Bonacina is, I think, always giving useful advice when he draws attention to the complexity of our subject. With regard to his remarks about Diagram 1 a full description of the principles was given when this new type was introduced in 1937. In the recent war years, one diagram has been made to serve for three Districts, partly because i t was convenient to demonstrate the comparative responses in this manner, and partly in the interests of economy, but i t is certainly not so easy to decipher as the one-district diagram ; after the present season i t may be possible to return to the latter. I have communicated Mr. Bonacina’s remarks with reference to the geographical distribution of acorns to Mr. Colquhoun, who has replied as follows :-

“ I think Mr. Bonacina has raised an interesting point, but, in my opinion, i t will be some years before we can get much data on which to study this. When we have regular records of the abundance, i t will be well worth examining these relatively to the geographical position. Now that the point has been raised, however, I shall certainly look out myself for any points of interest, and possibly other observers will be encouraged t o do so also.

I think the important matter at the moment is to enlist the help of ‘as many observers as possible, since we have now done enough preliminary work to show that these records are going to be of value; and, with the beginning of demobilization, I feel sure that the number of observers will increasd, and that the continuity of the data will be ensured.”