I love, love, love the Old Farmer's Almanac, which I have been reading since I was a kid. Here is the right hand-most column of the October calendar pages:
"Nobody knows for sure what accounts for the cycles in the lives of oak trees in which they make a huge crop of acorns every four or five years after several years of far lower production. Some baotanists say the superabundant years are due to ideal weather conditions when the trees are in flower. Some think the wide swings in production are adapted to foil insect parasites.
In a big year (a "mast year", so called), the woods seem to be flooded with acorns. They're treacherous underfoot; going down a woods road in an acorn super-year is like walking on marbles. An acre of oak woods in a normal year may produce a quarter-million acorns. In a mast year that crop might be doubled or trebled.
Whatever causes it, the extraordinary production of acorns is good news in the forest. Acorns are the bread of the woods. Deer, bear, squirrels, wild turkeys, partridge thrive in mast years. If you take to the woods in the spring following a bountiful acorn year, you'll be hard pressed to find a handful. That tidal wave of acorns has been consumed on the spot, or it has been cached by squirrels in safe places--some of them so safe that the provident squirrels themselves have overlooked them. Those acorns are the ones that will grow the oaks that will make the acorns that in turn the ankles of grandchildren."
Last year (and this is in the blog), Luis and I went up to Bear Mountain and it was clearly a mast year there. We were walking along the paved path but eventually I wanted to walk in the woods, not near them. We were coming down an incline and suddenly WHAM! I'm on the ground looking up and my heart is pounding madly! They were just like marbles. Just like that, and down I went. I wasn't injured but I certainly was worn out that night and sore the next day.
I keep waiting for our oaks to have a mast year in our back yard. I would love to see that!