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I finished reading today:
A Practical Guide to Prairie Reconstruction
by Carl Kurtz
This was lent to me by the refuge manager of the NWR that us USGS folks share an office with. She had been assistant manager of a tallgrass prairie refuge in the midwest.
It was my introduction, as it were, to prairie ecology. It's a basic instruction book on tallgrass prairie reconstruction. When to plant, what to plant, when to mow/burn/spray herbicide. Soil prep before planting... etc...
Pretty basic stuff, but all brand new to me. The major themes being...
*species diversity
*preemptive weed control
Basically a diverse established prairie habitat will crowd out invasives. Natives have evolved in that habitat and are, ultimately, better at existing there than weeds. But they have evolved to be part of a dynamic, diverse, and established prairie.
For restoration purpose this means that invasives will present problems only during the first few years if the diversity is adequate. Low diversity will allow weeds to colonize even years after establishment.
Disturbance is part of any habitat, especially one as dynamic as tallgrass prairie. Prairies with a high species diversity will have multiple species whose primary ecological function is to colonize disturbed areas. Some of these colonizers will be specialized for capitalizing on specific disturbance conditions. So that when a disturbance occurs, there is a native species in the seed bed to move in.
In a prairie with low species diversity, there will not be as many disturbance specialized native species. This leaves a ecological vacuum that invasives are ready to exploit.
This is why species diversity is so important in restoration of prairies, (or any other ecosystem, I would assume). Invasives love a vacuum and high diversity minimizes vacuums.
But, of course, restoration itself is a huge disturbance. There are people with soil tillers, compactors, and seed broadcasting equipment. Biologists poking around for critters. Which is why it's important to prevent weed predominance during the critical first years of restoration with timely and routine management.
Most prairie species are perennials while most invasives are annuals. This allows for a window of opportunity in which preventing weeds from going to seed will not significantly decrease the viability of the natives. Natives will continue to establish their root stock and sprout from that.
Techniques for weed control include spraying herbicide, mowing, and burning.
Mowing will remove seed heads from invasives and mowing level can be controlled to destroy seed heads while leaving stalks and greenery in order to allow natives to continue forming rootstock. Mowing can also be timed carefully to before invasive seeds are viable but late enough to prevent reseeding. So the weed lifecycle is halted while the natives keep going. (This technique seems like it would be useful in a variety of ecosystems.)
Burns are also important. Fire induces germination. In the first few years, fire can be used to induce any dormant invasive seeds remaining in the soil to germinate in order to manage the adult plants with mowing or spraying. Fire of course induces natives to germinate as well. (Doubleplus there. Two birds, one stone. Useful.)
This was the bulk of the information I took from the book. General prairie characteristic and soil prep were also new to me. (synopsis 1: prairies are cool and as the growing season progresses, the predominant species change into taller and taller species. synopsis 2: erosion is bad, mmmm-kay. and can be partially prevented by soil compaction.) But didn't inspire further gedanken exploration.
Along those lines... much of the above are my thoughts only, not actual scientific knowledge. Especially the why diversity is good and gets rid of bad weeds paragraphs.
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