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Home > Change in timing of tree phenophase across Europe in 2010

Change in timing of tree phenophase across Europe in 2010

This is a summary of the main results from the tree phenophase records for 2010 from the Beagle project. The changes in timing of phenophase were explored with respect to change from north to south and east to west. Only the north to south change was statistically significant and is expressed as the average number of days earlier or later that a given phenophase occurred for a one degree change in latitude (Table 1). The most southerly record was 44.1 degrees latitude in Romania (Cluj) compared with the most northerly record of 67.6 degrees in Russia (Murmanskaya oblast).

Bud burst is significantly later further north for five of the six species (Table 1). For example, on average a birch tree has bud burst 2.2 days later for every one degree north travelled. Therefore, the average time difference of birch bud-burst between south-central Romania (45 degrees latitude) and southern Norway (60 degrees latitude) is 15 x 2.2 = 33 days. Similarly first leaves are produced later the further north the tree is located, with a change of between 1.6 to 2.7 days per degree latitude for five of the six species. Changes in the later phenophase events are generally non-significant or even negative. The interpretation of non-significant events is that either there is no change in the phenophase date across Europe and/or that there are too few data. The latter may apply to beech, but generally the other analyses are based on large samples (often greater than 50). The negative values indicate that the phenophases are earlier as one travels further north.

A consequence of either no change or earlier ripening berries is that the time for reproduction is reduced as we travel further north. The same is true for the time from first leaf to leaf fall, i.e., the time for photosynthesis. For example, it can be calculated on average that the time from first leaf to leaf fall is 138 days for birch at 65 degrees latitude and 196 days at 45 degrees latitude. Similarly, rowan has 134 days at 65 degrees latitude compared with 185 days at 45 degrees latitude.

Table 1. Change in number of days per degree latitude. NS means the change is not statistically significant. Values in brackets are only marginally significant and should be treated with caution

Tree species

bud burst

first leaves

first flowers

berries ripe

leaves start to fall

birch

2.2

1.9

2.9

NS

NS

beech

NS

NS

NS

NS

NS

horse-chestnut

1.8

1.6

1.7

(-4.4)

NS

lime

2.9

2.7

NS

NS

NS

oak

2.0

2.7

(2.3)

(-4.5)

NS

rowan

2.7

1.8

NS

NS

NS

More details on the statistical analysis of the data can be obtained from the author.

Michael Gillman. 22 February 2011.

Published 15.03.2011.