Why mast years? This year a heavy crop of acorns is falling on the ground. Just look under any oak tree, or walk across the campus at Greenfield Community College. These acorns are the most visible crop of tree seeds which are also called ‘mast.’
Acorns and other ‘hard mast’ like hickory nuts and beech nuts are just a few of the crops that feed local wildlife. There is also ‘soft mast’ including blackberries, blueberries and apples. In addition to squirrels, pigeons, blue jays, owls and woodpeckers depend on mast to fatten up or prepare for migration. Rats and deer also come around for their share of acorns. Acorns are a big part of the deers’ winter diet. The larvae of some moths live and feed on young acorns as they develop.
Acorns are important to all these groups because they contain generous amounts of important nutrients, proteins, carbohydrates and fats, as well as calcium, phosphorus and potassium. Calcium and phosphorus are just as important to the bones of wildlife creatures as they are to us humans. Potassium and other vitamins are also important to wildlife.
In ancient times humans ate acorns, too, but not until after boiling them. Acorns are full of tannins which do no human digestive system any good until they are cooked. Acorn flour can be made and then needs to be stored carefully to prevent mold. Some Indigenous peoples still include acorns in their diet. Others will turn to acorns in times of famine. Today some people are reconsidering the value of acorns in an environment that is changing.
All that food value makes it clear what acorns and other mast do for animals. What does it mean for the trees if wild creatures are going to eat all their seeds?
Actually, acorns and other nuts are not all eaten by wildlife in a mast year. Too many nuts are dropped. Some nuts will be eaten near the tree. Some will be carried away and cached for winter meals by the birds and animals. Some of those nuts will be lost or forgotten by the animals and the nuts will germinate and grow far from the parent tree. Trees need wildlife to disperse their seeds and take root.
Neither do mast years occur regularly. Depending on the tree species it may take up to five years before another mast year occurs. Science does not definitively know how or why it is so, but there are theories. Everyone agrees that it takes a lot of energy for a tree to produce a heavy crop. It is also true that some trees like red oaks take two years for their acorns to ripen. It is not hard to believe that a tree will need time to recover before it can create another mast year.
One thing scientists do agree on is that a mast year is not a predictor of a coming bad winter. Neither is it caused by other weather fluctuations.
Then the question is how do the trees all know how to produce great volumes of seed at the same time? It wouldn’t help if one tree was spreading lots of seeds, if all the other trees were still making very few seeds.
Is it that the weather is similar over large areas? Is it that the wind pollinates trees at the same time some years?
There is not a solid answer to those questions, but one thought is becoming more popular. Peter Wollheben, a German forester, cared for his forests for many years beginning in 1987. Over time he became convinced that techniques and technologies he was expected to use damaged the trees. He objected to plantation monocultures and the use of heavy machinery in the forests. He was more and more interested in the ecology involved with forest management.
Wohlleben also came to believe that the web of fungi that grows around tree roots, covering vast expanses, made it possible for trees to collect nutrients and water, and then share those resources with other trees. One experiment found that in a large grove of beeches, where not all the trees had the same soil, scientists discovered that they all had the same rate of photosynthesis. The leaves of every tree got the same amount of sugar in spite of the differences in soil.
The fungi also send chemical and electrical signals, although not in the same way that they work for plants. Dr. Suzanne Simard in Nature magazine coined the term Wood Wide Web; some scientists call these mycorrhizal networks.
It is Wohlleben’s wish that if we all come to think that trees have ‘emotional lives and needs’ as he does, that we will become aware of ways that forests can give us respite at the same time the trees are benefitting the environment.
Wollheben’s book, The Hidden Life of Trees: What They Feel, What They Communicate explains his thoughts. I believe this is the first book on the subject, but other scientists are supporting the idea that trees are communal and live cooperatively with interdependent relationships and are able to communicate with each other.
When I walk under oak trees, or any other trees that have covered the ground with nuts. I confess that I feel a mystery I cannot understand. I can only wonder and marvel at the mystery.
Between the Rows November 30, 2019