I've been evaluating the weather prediction skills of oak trees for the past few years. There are folk stories, myths apparently, that the volume of acorns produced anticipates germination and growing conditions in future. A sparse crop, or mast, indicates a dry winter ahead, and abundance indicates great expectations for good growing conditions.

The crop around here is middling this year but the nuts are larger than usual, thus emphasizing the truth that the world is not just uncertain, it is ambiguous. What the heck kind of weather forecast is that!?

Perhaps it's not.

Many scientists now believe the mast cycle is an evolutionary adaptation; that over the eons oaks and other nut-bearing trees have developed an on-and-off mast cycle to ensure their reproductive survival. The theory makes sense. If oaks produced a consistently healthy crop of acorns every year, populations of nutloving animals would rise to the point where all the acorns would be eaten no matter how numerous. None would remain to grow into mighty oaks.

The mast cycle solves the problem. During moderate to poor years, wildlife get by as best they can, seldom increasing and often decreasing in numbers. Then comes a good year, when the trees pour it on and produce far more nuts than the animals can consume, no matter how fast they reproduce. Nuts are left to germinate and renew the forest. Over the leaner years following, wildlife again dwindles to numbers too few to eat all of the next bumper crop.

Well, OK, that seems plausible, but how do they coordinate with one another? It doesn't work unless most or all of the nut trees cooperate and synchronize their feasts and famines.

Oaks of one species in a localized area are often synchronized, producing many or few acorns in lockstep. Scientists haven't worked out exactly how this happens, but in many cases, weather plays a role. For example, a late frost might kill the flowers on all the oaks of a particular species in a particular area. (Chestnuts produced seeds more regularly, partly because they flowered in June, after the threat of frost had passed.)

In forests with more than one oak species, the number of acorns varies from year to year; some species take one year to go from flower to acorn while others take two, and each species produces a different amount of acorns. The effect of weather on acorn production also varies with each species. But every so often, most or all of the oak species in an area produce either a bumper crop or a paltry crop at the same time.

hmmmm, more uncertainty and ambiguity. This isn't just idle neeping about arcana since nuts are hugely important to wildlife. Many species - from rodents to bears - depend on them for a large part of their diets, and other species are indirectly affected by the prosperity or penury of those directly affected. Ground nesting birds, for example, do better when there are fewer rodents about.

People complicate the picture. They too eat some nuts but it was more important for their livestock.

O.E. æcern "nut," common Gmc. (cf. O.N. akarn, Du. aker, Low Ger. ecker "acorn," Goth. akran "fruit"), originally the mast of any forest tree, and ultimately related to related (via notion of "fruit of the open or unenclosed land") to O.E. æcer "open land," Goth. akrs "field," O.Fr. aigrun "fruits and vegetables" (from a Gmc. source). The sense gradually restricted in Low Ger., Scand. and Eng. to the most important of the forest produce for feeding swine, the mast of the oak tree. Spelling changed by folk etymology from oak (O.E. ac) + corn.

And . . .

mast
"fallen nuts; food for swine," O.E. mæst, from P.Gmc. *mastaz (cf. Du., Ger. mast "mast," O.E. verb mæsten "to fatten, feed"), perhaps from PIE *mazdo-/*maddo- "to be fat, to flow" (cf. Skt. meda "fat," Goth. mats "food," see meat).

Masticate on that a bit. At some level, at least in N. Europe, nuts aren't just food, they mean food. That's a pretty important dependency. But it may be reciprocal.

Healy, and many other foresters and wildlife biologists are recommending that oak forests be managed to encourage new oak growth, which might involve prescribed burns and selected cutting. "The idea of putting a fence around this and letting nature take its course isn't going to work for oaks," McShea says. "It's going to take active management."

Before Native Americans began burning forests, natural fires and periods of warmer, drier weather allowed oaks to survive. But paleoecological evidence suggests that oak forest really began to prosper and spread between 5,000 and 7,000 years ago, when Native Americans began burning regularly. . .

"This world here in the East is manmade," McShea says. "We made the forests where the forests are. We made the fields where the fields are. . .

"If the oak forest goes to maple and birch and yellow poplar, why does it matter? It matters because the wildlife that we enjoy in eastern forests, that whole vast community, is dependent on hard tree seeds, and that's been true for 10,000 years."

The oaks need us, apparently, as much as we and many other species need them. We grew up together.