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  1. I don't know what "a bit diffused" here means.

  2. Do other plants also "prefer their sunlight a bit diffused"?

     Mount Pinatubo was the most powerful volcanic eruption in nearly one hundred years. Within two hours of the main blast, sulfuric ash had reached twenty-two miles into the sky. By the time it was done, Pinatubo had discharged more than 20 million tons of sulfur dioxide into the stratosphere. What effect did that have on the environment?
     As it turned out, the stratospheric haze of sulfur dioxide acted like a layer of sunscreen, reducing the amount of solar radiation reaching the earth. For the next two years, as the haze was settling out, the earth cooled off by an average of nearly 1 degree Fahrenheit, or .5 degrees Celsius. A single volcanic eruption practically reversed, albeit temporarily, the cumulative global warming of the previous hundred years.
     Pinatubo created some other positive externalities too. Forests around the world grew more vigorously because trees prefer their sunlight a bit diffused. And all that sulfur dioxide in the stratosphere created some of the prettiest sunsets that people had ever seen.

Dubner, Levitt. SuperFreakonomics: Global Cooling, Patriotic Prostitutes, and Why Suicide Bombers Should Buy Life Insurance (2009). p 176.

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    $\begingroup$ I strongly doubt this is true, and I wouldn't get my biology info from Levitt and Dubner. Do they provide a reference? (SuperFreakonomics is, by the way, generally considered a big step down from Freakonomics in quality.) $\endgroup$
    – Raghu Parthasarathy
    Commented Dec 5, 2020 at 5:43
  • $\begingroup$ Who asked the trees what they preferred ? $\endgroup$
    – blacksmith37
    Commented Dec 5, 2020 at 19:47

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The studies are very complex and varied. There is evidence that strong omnidirectional light can get through to the understory of dense foliage more effectively.

Here is a Dutch study for crops in dutch greenhouses using light-diffusing rooves which maintain the quantity of light while making it omnidirectional. They report higher growth from diffuse light. https://www.researchgate.net/publication/40803021_The_Effect_of_Diffuse_Light_on_Crops

Studies of tree rings after volcanic eruptions have also found an overall higher growth for the periods following 5 major eruptions.

quotes: Under the presence of clouds, some studies have reported increases in both photosynthetic carbon gain (due to light levels closer to optimal) and water use efficiency, with less impact of photoinhibition due to excessive sunlight (Germino and Smith 2000; Gu et al. 2002)

This research suggests higher growth from direct sunlight in open forests and higher growth in dense, shaded forest under cloudy condition (research)

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