Did you have a question about it,
@Gina1960 ?
Lee-Roy, I don't understand the comment about water/gas exchange. The physical barrier of the cardboard is a temporary thing. The smothered spot should not be disturbed and used until the cardboard has decomposed. By the time a smothered spot is used, the dirt under the former cardboard layer should have begun a noticeable improvement.
And adding organic matter to the soil is so rarely "an evil." Leaves belong on the soil surface, and mulch is just expediting the physical rendering of wood, which is also something mother nature puts on the ground. For example, if one used 2 feet of walnut leaves, it might take longer before plants can grow in that spot, but there aren't many examples that I've encountered. The soil-dwelling critters that transform organic matter into the "good soil" particles can't just show up overnight because cardboard was laid and covered with leaves or mulch. They need time to establish and then to do their work.
I originally learned the concept under the name lasagna gardening but I've come away from using that because it implies that there are specific layers that are needed. Layers of stuff are fine, but any quantity of organic matter that is a single layer will work, as long as it is heavy and dense enough to block all of the light and be physically heavy enough to prevent seedlings from being able to get through.
And it's not really a gardening method, but a way to clear an area of everything currently growing there while improving the soil in the process - to be used for gardening when it is ready.
But the name is unimportant, as the title of this discussion shows. Everyone familiar with the concept probably recognized the subject right away.
Every spot where I've tried to garden w/o smothering first has been much less successful. More about how I have used this in the past, in OH and AL:
https://garden.org/ideas/view/...
But don't just take my word for it. A microbiologist can enlighten:
https://www.youtube.com/watch?...
