I have the impression that many more acorns have fallen from the oaks along the street this year. I also suspect that there are fewer leaves than other years, but no certainty about this. What difference from previous years caused this clear difference in acorns?
Answer
Dear Luke,
Many tree species have something like mast years, which are years in which they bear remarkably more fruit than usual. Beech and oak are known species that show this. At first it is thought to be an evolutionary adaptation of the trees, which rely on wind pollination and seed consumption by mammals. How so? Ex.
- Mass simultaneous flowering increases the chance of successful pollination.
- A number of ‘lean’ years keep animal populations in check so that not all the fruit is eaten during the mast year.
There is also an environmental factor in determining mast years. Favorable external conditions then ensure that the tree can invest extra energy in fruit set. Read: more jerks. Conversely, it is also stated that mast occurs in response to stress, e.g. persistent drought or heat, which makes the trees want to ensure their offspring. You will find that there is a certain frequency in the mast years (e.g. every 4 to 5 years), but in recent decades it has been noticed that mast years are becoming more and more frequent. Mast often occurs synchronously over large areas, ie many trees do this at the same time. However, there are also differences within areas, which can conceivably be due to differences in the soil (eg nutrients, water management, etc.).
You notice that there is no single explanation for this phenomenon, and a lot of research is still being done. Trees are not simple machines.
PS. The word “mast” is said to come from the German of fattening. Seed eaters (e.g. wild boars) that are lucky enough to experience a mast year get food very easily. You will therefore less easily spot those animals in a forest that has a mast season.
Answered by
Dr. Pieter Gurdbeke
Earth & Nature
http://www.ugent.be
.