Tag: trees

Trees and drought.

The scientific findings of how the height of trees affects their ability to cope with drought.

I subscribe to the online Physics World website and a recent article tickled my fancy. Because it was supported by what we see here at home.

That is that shorter and taller trees do not handle drought conditions as well as medium-height trees.

First the article and then some supporting evidence from home.

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ECOSYSTEMS
RESEARCH UPDATE

Medium-height trees survive drought best

04 Sep 2018

Courtesy iStock_MilosJokic.jpg

Forests with canopy heights of around 18 metres are more resistant to the effects of severe drought than those with shorter and taller trees, according to researchers in China and the US.

In the past, studies have disagreed on whether forests with lower or higher canopies will be more likely to make it through prolonged spells of hot, dry weather. The discrepancy has made it difficult for forest managers, who need to know which tree heights to encourage to ensure the highest growth and survival rates during extreme drought.

Study leader Peipei Xu at Beijing Normal University in China and her colleagues believe the issue is increasingly pressing. “Climate data indicate that warm areas of land are increasing, and the warmed areas are also drying,” says Chuixiang Yi at the City University of New York, US. “Hot-dry-induced forest mortality poses a significant global concern for the future as carbon dioxide continues to rise and the climate continues to warm.”

Xu, Yi and the rest of the team aimed to quantify the relationships between canopy height, growth and survival rates during drought accurately for the first time. They analysed data gathered during a severe drought in the southwestern US in 2002 that showed the effect on the ring widths of tree trunks, a useful indicator of their yearly growth. In addition, satellite data revealed how the density of vegetation changed over the course of the drought; the team used this to calculate both leaf growth and tree mortality rates.

The results revealed that trunk and leaf growth under drought conditions increased with canopy height for trees shorter than 18 metres but decreased with height for trees taller than 18 metres. “Our results indicate that both high and small trees have relatively low drought resistance,” says Yi.

After establishing these relationships, the researchers could determine the biological mechanisms governing tree growth and survival during drought.

“All organic matter in a tree is formed on the leaves at the top of the tree by photosynthesis,” Yi explains. “Tall trees have a longer water transport path from roots to leaves and [it’s] more difficult to overcome tissue resistance and … gravity, particularly under dry conditions. The roots of small trees are short, and their abilities to access water and nutrient supplies unavailable to the surface soil layer are extremely limited.”

The researchers believe that using their results to inform the active management of canopy structure could safeguard vulnerable forests. As climate models predict hotter, drier droughts becoming more commonplace, this could be essential to combat forest dieback – a phenomenon that will also drive climate change.

“Our findings provide insights into how to manage forests or plant what trees to increase forest drought resistance in facing hot-dry climate conditions to mitigate climate change,” says Yi.

The team reported the findings in Environmental Research Letters (ERL).

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So turning to home.

Here are a couple of photographs of tall trees to the Northern side of the house that are clearly showing some stress.

A tall fir tree that is due for removal because it is clearly dead.

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Another tall tree, this time a pine, showing signs of stress.

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Now in stark contrast look at the trees in the photo below. (Oh, that’s the smoky summit of Mount Sexton, elevation 3,829 ft., in the distance.)

Medium-height trees that border the Northern side of our driveway from the road to the house.

As our taller trees are felled each year we are planting new young trees, two for every tree felled, in one of our grass fields.

Because it is not just Jeannie and me, and all the wild birds, who love our trees!

Do you know, I feel the need to pee!

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This seems to have a good smell about it!

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Ah! That’s so much better!

Will close with another photo with a tree in it taken a few nights ago.

We must never, ever lose our trees!

Picture Parade Two Hundred and Forty-Three

The second set of tree photographs from here at home.

They seem to fit the theme of Life and Death! (The first set were published last Sunday !)

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Hope you all enjoyed them! All of the photographs were taken with a Nikon D750 camera through a Nikkor 24-120mm lens.

Picture Parade Two Hundred and Forty-Two

Just trees!

A few days ago I took it upon myself to spend an hour wandering our acres of wild forested land.

Here are some of the photos I took. Hope you enjoy them.

If I had a theme in mind when I was out taking the photographs it was Life and Death!

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I will continue with these next Sunday. All of the photographs were taken with a Nikon D750 camera through a Nikkor 24-120mm lens.

 

Giving in to Nature.

The power of Nature might surprise you!

The last two posts have offered two aspects of our bountiful Nature. First we had Earth Day and the celebration of our trees. Then yesterday we had the celebration of the birth of five Canada Geese goslings.

So it seemed appropriate to continue the theme for another day.

Earlier this month there was an article over on MNN that I saved for later use simply because the message it offered was counter-intuitive. Here’s how that article opened:

Deforestation vs. nature: The winner might surprise you

Large-scale tree-planting projects, abandoned farmland help balance out rain forest destruction.

By: Michael Graham Richard
Wed, Apr 08, 2015 at 10:11 AM

Forest canopy heights are highest near the equator and generally decrease the closer forests are to the poles. (Photo: NASA)
Forest canopy heights are highest near the equator and generally decrease the closer forests are to the poles. (Photo: NASA)

For decades, we’ve been hearing about how the world’s forests are under attack, how the equivalent of “36 football fields of the world’s forests are being cut every minute.” With all this pressure on nature, could the Earth possibly be getting greener? Not a chance, right? Surprisingly, that’s what a team of scientists discovered when they looked at two decades’ worth of data from satellites that use a technique called “passive microwave remote sensing,” which allows researchers to measure how much biomass, or living matter, is present on the surface of the planet.

The researchers found that despite ongoing deforestation in the rain forests of South America and Southeast Asia — a huge problem, regardless of what happens elsewhere — other regions outside the tropics, such as Africa and Australia, have been improving enough to offset the losses. Some of the more unexpected sources of this extra biomass are farmland abandoned after the fall of communism where forests have spontaneously regrown in the former Soviet republics, as well as in areas of China where large-scale tree planting projects took place.

What really caught my eye was another photo from NASA that showed the biomass stored in trees in the USA.

The concentration of biomass stored in trees in the U.S. The darkest greens reveal the areas with the densest, tallest, and most robust forest growth. (Photo: NASA)
The concentration of biomass stored in trees in the U.S. The darkest greens reveal the areas with the densest, tallest, and most robust forest growth. (Photo: NASA)

But as the article reminded readers:

We’re only talking about biomass quantities being offset, though; the loss of rain forests also mean the loss of many species of animals and plants, as well as unique habitats that can’t be replaced by other regions elsewhere, such as the savannah of Africa or the Australian Outback. So while this is good news, we can’t declare victory over deforestation just yet!

Nonetheless, I am sure that I am not the only one to welcome this reminder of the power of Nature. Or in the closing words of that MNN article:

In the period between 2003-2012, the total amount of vegetation above the ground has increased by about 4 billion tonnes of carbon. Any way you slice in, 4 billion tonnes is significant!

This is particularly important because around 25 percent of the CO2 that we release into the atmosphere by burning formerly buried hydrocarbons is absorbed by plants, so having more of them can help slow down (but not stop) climate change, and there’s a limit to plants’ rate of absorption. Still, it’s nice to get good news for a change …

While it may be a long way yet from them being tonnes of carbon, let me close with three pictures of ‘increasing tree biomass‘ right here on Hugo Road in Merlin, Oregon.

The oak.
The oak.

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The madrone.
The madrone.

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The cedar.
The cedar.

Nature really does have all the answers to man’s long-term survival.