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FIGURE I 1.9 Phenological data as a climatic index. Solid line shows the average number of days per year in which the flowering dates of 51 species were earlier (below zero, left ordinate) or later (above zero, left ordinate) than the average.The dashed line shows the average departure of mean daily temperature from March I to May 16 for each year (right ordinate scale). Observations from Bluffton, Indiana (Lindsey and Newman, 1956).

cool, though this impression could be due entirely to the inadequate statistics (only 30 reliable dates in 400 yr!). Were'it not for similar phenological observations from China, tending to support this idea, particularly of a cooler twelfth century in the Far East, one could place little faith in the Kyoto data alone (Chu, 1973).

The most important phenological records from Europe concern the date of the grape harvest. Grape harvests are, of course, not only determined by climatic factors but also by economic considerations. For example, an increasing demand for brandy may cause the vineyard owner to delay the harvest in order to obtain a liquor richer in sugar and more desirable from the point of view of spirits production. However, such factors are unlikely to be of general significance, and,

TABLE 11.5 Average Cherry Blossom Blooming Dates at Kyoto, Japan, by Century. Mean date, April 14.6; n = 171

Century

9th

10th

11th

12 th

13 th

14th

15th

16 th

17th 18 th

19th

20th"

Day in April

11

12

18

17

15

17

13

17

12

12

14

No. observations

7

14

5

4

8

13

30

39

10

5

36

From Arakawa (1956b).

" Chu (1973) notes 20th century data (1917-1953) for blossoms "in full bloom."

From Arakawa (1956b).

" Chu (1973) notes 20th century data (1917-1953) for blossoms "in full bloom."

providing variation in the dates of grape harvests shows regional similarities, it is reasonable to infer that climate is a controlling factor. Thus, Le Roy Ladurie and Baulant (1981) have produced a regionally homogeneous index of grape harvest dates for central and northern France, based on over 100 local harvest-date series, extending back to 1484. For the period of overlap with instrumental records from Paris (1797-1879), the index had a correlation coefficient with mean April to September temperatures of +0.86, indicating that it provides a good proxy of the overall warmth of the growth season (Fig. 11.10; Gamier, 1955; Le Roy Ladurie, 1971). Indeed, Bray (1982) has shown that the reconstructed summer paleotemperatures also show a strong correlation with the record of alpine glacier advances in western Europe. Periods characterized by temperatures consistently below the median value are generally followed by glacier advances.

The deterioration of climate during the Little Ice Age also had important geographical consequences for plants and animals, particularly in marginal environments. In the Lammermuir hills of southeastern Scotland, for example, oats were cultivated up to elevations of over 450 m during the warm interval from A.D. 1150 to A.D. 1250. However, by A.D. 1300, the uppermost limit had fallen to 400 m and by A.D. 1600 to only -265 m, more than doubling the area of uncul-tivable land (Parry, 1975, 1981). These changes probably resulted from reduced summer warmth, wetter conditions, and earlier snowfalls in winter months, factors which all combined to increase the probability of crop failure from only 1 yr in 20 in the Middle Ages to 1 yr in 2 or 3 during the Little Ice Age. The abandonment of upland field cultivation was also accompanied by the abandonment of upland settlements and resulted in a considerable redistribution of population in the area.

Former plant and animal distributions can provide useful indices of climatic fluctuation, though it is not always possible to quantify the significance of the change in species range. Harper (1961), for example, has documented significant changes in the distribution of flora and fauna in subarctic Canada during the twentieth century as a result of the widespread increase in temperature during this period. Similar observations have been made in Finland by Kalela (1952) and the change is not confined to terrestrial species; northward migration of fish in the North Atlantic as a result of increasing water temperatures in the North Atlantic has also been noted (Halme, 1952). Trading post records of animal catches around the coasts of Greenland point to the close dependence of animal populations on climatic fluctuations and associated changes in the distribution of sea ice (Vibe, 1967). These records rarely extend back beyond the mid-nineteenth century, however, and merely point to the biological significance of climatic fluctuations, which instrumental records have documented in considerable detail. Nevertheless, there is great potential in using historical records of former plant and animal distributions, the timing of migrations, etc., to document climatic variations during periods for which no instrumental records exist. The possible value of such work is well illustrated by the wide-ranging surveys of former plant and animal populations in China reported by Chu (1973).

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