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.



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).


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.


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


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!


This seems to have a good smell about it!


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!

15 thoughts on “Trees and drought.

  1. I agree. Trees are vital to the planet. Too bad these fires keep happening every year. We had them in AZ as you know & I had them in CA where I used to live. Everywhere I look friends are telling me 10% containment. Wow. I hope everyone stays safe.

    Liked by 1 person

    1. Especially so many facing the imminent arrival of Hurricane Florence. I read the following a few moments ago, from the BBC News site: The National Hurricane Center said: “Some strengthening is expected during the next day or so, and Florence is expected to be an extremely dangerous major hurricane through Thursday night.”

      Makes our forest fires look like a walk in the park!

      Liked by 1 person

  2. I know I am weird but I look at all of creation in similar ways where plant or animal and with that being said, the middle aged life forms have the strongest systems; Human, animals even trees. When young, the strength and immune systems are not fully developed. When old, those same systems are in decline and environment adds to or pulls from those systems. When in the middle of our life cycle, we are usually at our strongest.


    1. That’s not weird, not in the slightest. What you demonstrate are the power of thought and the power of words, coupled with one of the most incredible languages ever developed: English!

      You may assume that I rather liked what you wrote! 😎

      Liked by 1 person

  3. Here on the east coast, we have had an over abundance of rain this summer. The result is fungus and leaf drop. Perhaps we need to take a bigger perspective and look at the planet as a whole, rather than what is impacting each of us locally.
    It doesn’t make it easier, but increases understanding for all of us. 💕
    Hang in there 💛


    1. It struck me that both Monika’s reply and yours, Val, could be best responded to together. I’m researching the history of temperature trends for our planet going back 500,000 years or more. Going to turn it into a blog post one day.

      But your idea, Val, about looking at the planet as a whole resonated with my research findings. For there have been 4 peaks of high global temperatures over many thousands of years. The present warming trend has not, so far, overtaken the previous one.

      Yet the present rising trend does seem, uniquely, to be partly the result of human activities in the last 100 years. But in a 1,000 years from now our human influence on global conditions may seem both minuscule and temporary.

      A truly global perspective devoid of vested interests is sorely needed.


  4. Climate change deniers are just idiots. They like to sound learned and sharp, whereas they are just self-obsessed brutes closed to reality. That today’s temps have not overtaken the Eemian peak (110,000 years ago) is not crucial: we will be there very soon. What’s important is that we have higher CO2, than any time in the last 3 million years, and this leads temps, theory and observation say. All forests in places like the American West, will burn:

    As soon as the Arctic sea ice melts, and that will be soon, and sudden, now we know that for sure:


  5. These cycles have been on going for thousand of years, though I do feel this particular cycle of climate change is hitting home harder given that we can instantly access places around the world being affected by either drought or floods..I would be interested in reading more of your research into this area Paul.. And Science has known our planet has heated up and cooled down dramatically at various intervals and geographic evidence has been gathered to sustain these results..
    One has to look further afield too Paul.. At the rotation of our planet and what ‘heavenly bodies’ planets have entered into our solar system.. When one sees these affects our own Sun’s performance, we then begin to understand how Solar Storms affect our own Earths behaviours and gravitation pull…
    I hope you keep digging deeper into your research Paul… It will be amazing what conclusions come into our awareness…
    The planet is in Crisis no doubt about it.. But Mankind while adding to its accelerated with its carbon footprint is not the whole cause of this escalation. .. And when one looks back in various places where Science is not serving other agendas we then can see other factors that have not always been made visible to the general public..

    Love and Blessings to you and Jean Paul ❤


    1. Dear Sue, such a thoughtful reply from you. I know in my heart (and mind!) that this is so much more complex a situation and doesn’t lend itself to ‘instant’ declarations. That’s why I have started the research. As I come to my own conclusions I will share them in this place.

      Once again, Sue, thank you! You are a good friend of this blog.

      Liked by 1 person

      1. I know you will Paul… I have been looking deeper into these things for years and until you discover the truth for one’s self.. 🙂 lol.. We all have a responsibility to find the truth of such things.. And sort the wheat from the chaff.. 🙂 Enjoy your day both of you,, I am just tuning out for the evening.. 😀


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