After writing about what happened to abandoned turf in Japan, Thailand, and Michigan, I remembered the Broadbalk Wilderness experiment at Rothamsted. I was going to share only that, but as I was reading the introduction to Hubbard's Grasses today, I was struck by the relevance of this passage:

Most visitors to the British Isles are deeply impressed by the luxuriance of our meadows and pastures, as well as by the fine crops of the cereal grasses – wheat, barley, oats, and rye of arable land. The rich growth of the herbage grasses gives one the impression that here is a land ideally suited for such plants. This inference is correct, for our climate is most favourable for the production of this luscious green growth during a large part of the year. It is not realized, however, that these associations of grasses are almost entirely artificial in origin and due to the continuous labours of many generations of our ancestors, together with the cumulative action of the grazing and treading of their domestic animals. Under our climatic conditions and on most soils, these artificial grasslands, when removed from the control of man and beast and left to the effects of competition and natural selection, gradually revert to scrub, and in most cases from scrub to forest.

And that is just what happened, and quickly, at Broadbalk Wilderness. In 1882, about 0.2 ha of the Broadbalk wheat field was abandoned. It was fenced off to prevent grazing, and the wheat was not harvested, so the seeds could fall on the ground and have the opportuninity to regenerate. What happened? From Rothamsted's Guide to the Classical and other Long-term Experiments: "The wheat did not compete well with the weeds, and after only four years the few self-sown wheat plants that could be found were stunted and barely recognisable as cultivated wheat. One half of the area has remained untouched; it is now woodland dominated by ash, sycamore and hawthorn; the ground is covered with ivy in the densest shade, and with dog's mercury and other species present where shade is less dense."

The other half has been stubbed (woody species removed annually), and since 1957, half of the stubbed section has been treated by mowing, then grazing, and since 2001 by mowing. 

So part of this abandoned field is woodland, and part is stubbed, and what happened in the area where mowing began in 1957? "The grasses did not increase substantially until the site was grazed by sheep. By 1962, perennial ryegrass and white clover had appeared, and they are now widely distributed. The ground ivy has almost gone, and the growth of other species is much restricted."

The Guide to the Classical and other Long-term Experiments is great reading. One finds an introduction and summary of Broadbalk Wilderness, and Park Grass, and Garden Clover, and Exhaustion Land, and so many other agricultural, botanical, and ecological experiments.