Having rain almost everyday -
Can trees get too much rain?
Rotten tree root. Here in the Northeast of the US, we are having rain almost everyday and not a lot of sunshine. (We are extraordinarily lucky, as this is only the remnants of horrible flooding in the interior of the country, as storms dumped their moisture loads well before arriving in our region. There has been record flooding in the heartland of the US and nothing we are receiving here compares to what they are facing from the weather.) This portends consequences for us as heavier than normal rains saturate our landscape. So what should we be concerned about?
Well, for one thing, what about the trees? If you have tall trees near your house, you may have to worry about one or some of them coming down in high winds. (see post of October 2018 for more info). Trees need a lot of water and drink the rain up with their roots. But they need oxygen as well, and if a tree’s roots are chronically saturated with water, the lack of oxygen will weaken the root system. The anaerobic (lack of oxygen) nature of saturated soil can also promote the growth of root eating fungi like armillaria and phytophothera. If fungi weaken the roots, the tree is more likely to topple. It is probably a good idea to examine your trees now to assess whether they might pose a threat or not. To identify various tree diseases, you can go to https://extension.psu.edu/tree-diseases-that-create-hazards. If you aren’t sure but see obvious signs of disease, asking an arborist for an evaluation is a good idea.
Well, for one thing, what about the trees? If you have tall trees near your house, you may have to worry about one or some of them coming down in high winds. (see post of October 2018 for more info). Trees need a lot of water and drink the rain up with their roots. But they need oxygen as well, and if a tree’s roots are chronically saturated with water, the lack of oxygen will weaken the root system. The anaerobic (lack of oxygen) nature of saturated soil can also promote the growth of root eating fungi like armillaria and phytophothera. If fungi weaken the roots, the tree is more likely to topple. It is probably a good idea to examine your trees now to assess whether they might pose a threat or not. To identify various tree diseases, you can go to https://extension.psu.edu/tree-diseases-that-create-hazards. If you aren’t sure but see obvious signs of disease, asking an arborist for an evaluation is a good idea.
The wind can easily blow through the canopy. The water also acts as a lubricant, weakening the root bonds in the soil and makes ‘windthrow’ more likely. If the tree is densely leafed, storm winds can’t readily flow through the canopy and it becomes a sail. Think of using a hammer to pull out a nail. The more pressure you exert on the top of the handle, the more leverage there is to pull out the nail. Well it is the same with a full canopy! Add the lubricant of water saturated soil, and falling over becomes more likely. This is another reason to keep a tree properly pruned, to reduce the sail effect.
And of course, water is heavy. One gallon equals eight pounds. Trees absorb more water than they really need for nourishment. They give it back to us through transpiration. A regular tree breaths out 250 and more gallons of water daily through its leaves. That’s at least 2,000 pounds, one ton! So if just the weight of a tree’s breath is startling, think of how much force in weight, is in that tree next to the house? It pays to monitor the tree’s health. To help trees along, you should prune them regularly so they are structurally sound and can weather the storms. Also important are the forks in the tree (see post of April 2018).
Our house is surrounded by a lot of trees, and in the evening you can feel the moisture building. An acre of forest can have over 1,000 acres of leaf surface area. All this moisture being exhaled by trees every day, is critical to our environment. Isotope studies have shown that water evaporated from the oceans by the sun, rarely falls on land as rain past 150 miles from the coast line. So the rains that nourish us beyond that, mostly come from the moist exhalation of trees. Indeed, about 95 percent of the rain inland comes from the exhalations of trees.
Our house is surrounded by a lot of trees, and in the evening you can feel the moisture building. An acre of forest can have over 1,000 acres of leaf surface area. All this moisture being exhaled by trees every day, is critical to our environment. Isotope studies have shown that water evaporated from the oceans by the sun, rarely falls on land as rain past 150 miles from the coast line. So the rains that nourish us beyond that, mostly come from the moist exhalation of trees. Indeed, about 95 percent of the rain inland comes from the exhalations of trees.
Trees living in wet soil- like willows, spruce and white pine, are prime candidates to fall in storms. As you by now may guess, because the soil is saturated, the roots of trees in habitually wet ground, tend to be shallower to capture enough oxygen to run their metabolism.
So, having a lot of rain can be good or bad.
So, having a lot of rain can be good or bad.
Australian desert The tree’s ability to humidify areas inland, away from oceans, guarantees the rain cycle. Without trees, there is no rain cycle and the landscape turns into desert. The Southwest of the U.S. used to be much greener 300 years ago, before settlers started cutting down forests for lumber and agriculture. Nowadays, the Sonoran and Chihuahuan deserts are slowly expanding north.
Australia’s European settlers, clear cut so many trees, that the continent’s increasing desertification may be irreversible. No matter where you go on the planet, from the Amazon rain forest to Africa, clear cutting forests for agriculture, etc, leads to desertification of the land down stream from the prevailing winds. Without the moisture exhaled by the trees, the land changes.
Australia’s European settlers, clear cut so many trees, that the continent’s increasing desertification may be irreversible. No matter where you go on the planet, from the Amazon rain forest to Africa, clear cutting forests for agriculture, etc, leads to desertification of the land down stream from the prevailing winds. Without the moisture exhaled by the trees, the land changes.
Image of Maui by Landsat satellite. The small island to the southwest is the unpopulated island of Kahoolawe. Even an island- surrounded by water may not be immune. Kahoolawe, the smallest of the eight main Hawaiian islands, is about the size of Manhattan, and sits about seven miles southwest in the rain shadow of the larger island of Maui. Historically it was heavily forested, but after many of the high forests of Maui’s volcanic slopes were cut down, it rapidly turned into a desert island, deprived of the moisture that was exhaled and turned into rain by the slopes of the volcano’s trees.
Kahoolawe is low and relatively flat. So there is not enough lift created for the prevailing northeasterly trade winds to create rain from the surrounding ocean. (This is known as orographic precipitation, and occurs when a moving air mass is forced upwards by rising terrain- Maui’s volcanic slopes. It cools down with rising altitudes, humidity increases and rain can be generated downstream of the winds.) Without Maui’s forests, Kahoolawe- seven miles away over the ocean, was starved of moisture and is now mostly desert, despite being surrounded on all sides by water!
There is a lesson in this.
Kahoolawe is low and relatively flat. So there is not enough lift created for the prevailing northeasterly trade winds to create rain from the surrounding ocean. (This is known as orographic precipitation, and occurs when a moving air mass is forced upwards by rising terrain- Maui’s volcanic slopes. It cools down with rising altitudes, humidity increases and rain can be generated downstream of the winds.) Without Maui’s forests, Kahoolawe- seven miles away over the ocean, was starved of moisture and is now mostly desert, despite being surrounded on all sides by water!
There is a lesson in this.
Kahoolawe island, Hawaii, is now a desert.
So keep the trees,
just make sure they stay healthy.
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