and tailored for a North Branch Restoration Project seminar.)
Why plant seeds?
Why not just wait and see what comes up on its own? We’ve tried that many times, and the results have tended to be a temporary “weed patch” that did not become a sustainable ecosystem but just tall goldenrod, briars, and, eventually, buckthorn once again. Planting a diverse mix of (now rare) local ecotypes of grasses and wildflowers can restore the habitats of hundreds of species of plants and animals.
Why is it important to plant seeds in the right place?
Many species that we plant are now common and easy to gather in our restored areas. But some of our most important species are still rather rare – and harvesting them from the wild, as we do, diminishes the ecosystem they’re taken from. If we remove too much too often – we do damage. This is especially true of the seeds of some now-rare, formerly dominant conservative species. So we want them in our mixes, but we don’t want to waste them.
Also, we don’t get as much seed as we need. Wetland plants won’t propagate on dry ground; species of full sun won’t grow in the shade. Our goal is to conserve rare biodiversity; we can’t ethically waste seed where it won’t grow.
Should we plant the same species in bare ground (where brush was cut) … compared to an area that just needs more diversity?
Many of the most important species won’t do well on bare ground, so we save them for “turf” mixes.
How do I recognize where I should stop broadcasting the prairie seed mix and start doling out savanna seeds?
The first answer is that you’ll want to overlap those mixes a bit – as no one is so smart that they know for sure, and, indeed, the species mix naturally.
The second answer is that it depends on how far apart and how big the trees are in your savanna. A rule of thumb: if full sun shines on a piece of ground for two thirds of the day or more, plant prairie seeds. But there’s much more on this, below.
In restoring an oak woodland, should all the invading shade be removed before I plant my first seeds, or should the process be staged?
Our knowledge of how to restore biodiverse woodlands is even more primitive than with prairies and savannas. Some approaches lead to an understory of briars, poison ivy, and other rank vegetation that seems to head in the opposite direction from quality. If you’re prepared to put in a lot of effort, open the canopy enough for oak reproduction … then plant diverse species for that level of sunlight, and let ecological processes take it from there. But other approaches may also show promise.
Some Visuals That Might Help
Many restoration principles can be expressed simply, but recognizing how to apply them on the ground in a specific place is the real challenge. Don’t expect to be perfect at it. In fact, just go ahead and assume that you won’t be right all the time and in every detail. But thinking about the principles ought to help. And field exercises help the most. The visuals below were designed to help prepare for field exercises.
Our seed mixes are called “Prairie,” “Savanna,” and “Woods.” That works well in the prairie and a uniformly shady woods, but in the savanna, probably the mixes should be called something like “Full Sun,” Part Sun,” and "Dappled Shade.”
SIMPLIFIED DIAGRAM
The graphic above simplifies the decision by considering only the amount of sun. Most open savanna should be seeded with the “Prairie” mix. But immediately under and around and especially to the north of isolated large trees (considering how the sun’s rays slant at our latitude), plant the “Savanna” mix. In the darkest parts of the savanna, blend in some “Woods” mix.
There is no “maple forest mix” on this map, because the North Branch had little of the maple/basswood or beech/ maple forest (and those fine natural communities are a good deal less threatened than oak communities, so there’s been less research on restoration techniques or conservation goals or priorities). The darkest community we’re considering in this exercise is oak woodland and oak forest, which have much brighter understories than a maple forest.
Notice, above, that the seed mixes to be planted in a savanna may be mostly the Open (“prairie”) mixes, and a woodland may have open meadows and many areas (depending on the spacing of the trees) for the “Intermediate” mix. In fact it is in these areas that the bur and white oaks reproduce.
ONE STEP MORE COMPLICATED
This graphic adds wetness to our decision-making. On the North Branch we deal with few areas of “dry” soils or even “dry-mesic” soils, so we’ll focus here on “mesic” and “wet-mesic” soils.
(“Mesic is just fancy jargon for “average” moisture. That is, it’s half way between dry and wet.)
Thus the graphic suggests where to plant the six different seed mixes that we need here:
WMP: Wet-Mesic Prairie
WMS: Wet-Mesic Savanna
WMW: Wet-Mesic Woods
and
MP: Mesic Prairie
MS: Mesic Savanna
MW: Mesic Woods
Note that the very open woodland here has as much "savanna" as woodland seed.
How do we define the term “Savanna” for seed mix purposes? It’s an area that sometimes has full sun but is shady 40 to 60 percent of the time – whether because one or two big trees puts it in full shadow for part of the day, or because the overall tree canopy has enough holes in it that any given piece of ground gets sun for 40 to 60 percent of the day.
The graphic may seem complicated, but on the ground you can work it out. In relation to trees, are you: a) far from, b) near, and c) under? Recognizing whether you’re in mesic, wet-mesic or wet soils is trickier. You can often tell from the existing vegetation. For example, white oaks suggest “mesic.” Swamp white oaks suggest “wet-mesic” or “wet”. But you can also often judge more simply (especially as you’ve become more familiar with your site) because on the day you’re seeding, the areas you know to be mesic may be light brown; the wet-mesic on that day are dark and damp, and the wet areas have standing water.
Consider Existing Quality
When broadcasting seed, consider competition from the species already growing there. It you have bare ground where brush was just cut, plant a simple basic mix. If an area is dense with tall goldenrod and briars, don’t invest too much rare seed there yet.
On the other hand, the highest-quality seed (“Turf”) prairie mix should be broadcast into thin old-field turf (made up, for example, of bluegrass, daisy, carrot, and early or gray goldenrod). This approach has been proven effective by long experience on the North Branch. Check out photos of and comments on such areas.
If you’ve thinned trees in a pretty good quality woodland (with some understory plants like Penn sedge, pussytoes, elm-leaved goldenrod, bellwort, etc.), save your more conservative species for there. These might include shooting star, wide-leaved panic grass, and rue anemone. For more detail on “high quality” or “conservative” species see:
https://woodsandprairie.blogspot.com/2018/07/a-myth-coming-true.html
What’s your experience?
Please keep careful records, and share what you learn.
If you’d like more detail on these questions
Acknowledgements
Thanks to Eileen Sutter for much improving this post for North Branch seminar use.
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