This post is the first draft of our plan.
Yet, we “plan and do” kind of quickly. So some of the
experiments are already under way.
On the other hand, we really do want input from anyone with
good ideas, and we hope this plan will change thanks to good input.
We – the Somme 2030 group (or the “Somme-east-aas”) –
experiment constantly, but we decided to be more deliberate about our
experiments this year. Of course, this is “battlefield medicine,” and when we’re
trying to heal whole ecosystems, so many things change so complexly all the
time, that it’s hard not to get caught up in the moment and forget about next
month – to say nothing of next decade and next generation. We do our best.
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| Our first experiment, fall 2013, was to rake a dozen circular patches to see how raking away the leaves would effect seedling establishment. This photo shows some of the raked and planted circular patches. They did great. The seeded but unrated areas were pretty much just dead leaves. We want to do more variations on this experiment. |
We were reminded to quicken our seed efforts by advisor Tom
Vanderpoel when he remarked on November 19th, that he sure hoped he
could get the last of his seed broadcast before the snow. He plants earlier
than most. His impression is that the seed of some species does better if it’s
had the full treatment of both spring and fall freeze-and-thaw cycles. We hope
to test that this year.
We’re considering doing some or all of the following
experiments in seed planting this year. We work mostly in degraded oak woods,
where we have already determined that herb reproduction is poor if the seeds
are covered by the natural thick mulch of fallen leaves.
Thus we would compare the following treatments:
1. Unburned areas:
Unraked
- Broadcast seed into leaves in fall with leaves not raked.
(Control: compare with all other treatments.)
Raked
- Broadcast seed in early fall after raking.
- Broadcast seed in late fall or early winter after raking.
- Broadcast seed in early spring after raking.
- Broadcast seed in late spring after raking.
2. Fall burn areas:
- Broad scale: Broadcast seed in early fall after burn. [DONE
Nov. 20]
- Broadcast a more intensely planted circle (in an area the
gps shows we missed?).
3. Spring burn areas:
- Broad scale: like in fall (save some of the same mix
planted Nov 20?).
- Plant in a more intensely planted small plots.
Note: We may want
to do mesic vs. wet mesic versions of all treatments. Wetter areas have
different fire dynamics (e.g. they usually don’t burn), different leaf litter
dynamics (Rot faster? Or slower? Easier on germinating seeds? Harder?), and
different species involved.
On the other hand: If we do all the experiments listed
above, with a mere three replicates each, that means marking, raking, and
seeding 27 plots, which might be a lot for us? Or would it?
Complicating the decisions is the fact that we don’t know if
we’ll get a spring burn and if so, what it would cover. But this is the
environment we do this science in, so, we decide how much of our time, energy,
and seed to invest in what, and then we do it.
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| This is how much mesic woodland seed we got. Our larger priority this year was wet and wet-mesic woodland, not fully prepped for broadcast yet. But we're getting close. No species list compiled yet either. But first things first! |
Plot size:
perhaps 1 rake radius? In that case our plots would have a radius of about 1.43
meters and an area of about 6.4 meters. The numerical precision here is kind of
a joke, as leaves blow around; the deer kick them out of the way looking for
acorns; people and raccoons do stuff, etc.
What might we find
out?
a. Perhaps that we should invest most all our seed in burned
areas.
b. Thus, perhaps we should broadcast it in lower priority
areas like the few that got burned this fall and only invest as much seed as we
can rake leaves for in other areas.
c. Or perhaps we should save most of our seed for spring,
hoping for a good burn of priority areas then.
d. Perhaps the data may suggest that, in years without a
fall burn, we should rake leaves and plant as much as we can in fall. (At some
point we perhaps should also do an experiment on how fast most species spread
when we get them established in patches strategically spread around.)
e. Perhaps this what we find for wetter areas will not be
true for drier areas – so then we’d follow two different protocols depending on
hydrology.
f. We could outline a lot more possibilities, but perhaps
this is sufficient to suggest why we go to the trouble to do these experiments.
Another note: How
much land are we trying to restore … and how fast? The overall area we’re
currently working on in Somme East is about .25 km2 or about 60
acres. That may seem like a big bite to take at one time (for example, with no
funding for seed, modest priority on the burn schedules, etc.), but we got an
outstandingly effective controlled burn in fall 2014, and we’re trying to take
best advantage of it. We put a huge amount of time into spraying re-sprouts
from that burn, gathering seed, and made a good start last fall, planting roughly
.09 km2 or 23 acres. Much of this was planted very thinly, but the
seed of those species will spread annually, forever. One of our limitations is
to keep this year’s experiments out of the areas planted last year.
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| Only one small area got burned this fall. Here, with thick leaves mostly gone, it was time to plant. We raced over, as soon as the mesic woods seed was ready, and put out a bag and a half, while we could see the ground, before the snow. |
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| Here's the same area after the snow that evening. We think it's fine to broadcast seed onto snow, but only if we know where there's enough soil exposed to give the seeds a fighting chance once they've settled down through it. The seeds sown here the day before are so happy to start their natural journey through winter! |
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| Detail of seed in bag. It's not happy there. Indeed, it calls out to us, "Get us out into the cold damp earth. We have lives to lead, and we need more help. Hurry!" They're demanding - but appreciative in the end. |
Sounds like a worthwhile experiment, I have many of these same questions. I wanted to get our seed down before the snow also so we could rake some areas before sowing, but did not get it done. I used to just broadcast onto the leaf litter but that was probably not the best idea, as your results seem to confirm.
ReplyDeleteI like to compare frequent fire in oak woodlands to being like raking a lawn. What happens to a lawn when the leaves aren’t raked from it? (rhetorical) It is quite possible that the treatments where seeding has been so successful will degrade without continuation of the conditions which created the success (raking, fire, etc.).
ReplyDeleteIn contrast, I grew some woodland grasses from seed in a garden under a tree. Once these woodland grasses matured they never produced much seed. After a few years of little seed production I piled additional raked leaves around the plants. Ironically, the grasses all produced abundant seed the following season.
Variations in habitat reduce leaf litter and tend to be occupied by certain species. Examples of variations include slope, wind exposure, and small changes in topography. If you tend to find a species growing on the raised mound of a decaying stump or log then seeding would likely be most successful if it was directed toward the same type of situation. Accounting for the preference of individual species is important.
In my garden leaf litter decomposes faster in partially shaded areas as compared to sunnier areas. I believe this is because the sun dries the leaves on the surface faster reducing the time available for decomposition. This might be a variable you will want to consider too.
I took a walk through some woods recently thinking of your seed experiment. I specifically was looking for plants growing on rotting logs and stumps. I found a few vascular plants on logs that had not yet lost their bark. However, I quickly realized that vascular plants are not prevalent on old stumps and logs in our fire adapted ecosystem. This contrasts with ecosystems that are not adapted to fire which are rare relicts in our area.
ReplyDeleteAfter closer inspection I realized the mounds I had been remembering that were covered with woodland plants were not old decaying stumps. I realized these mounds were made from soil being deposited when trees had tipped over.
I have noticed an even more common habitat for small and delicate woodland species. These small and delicate woodland plants have a tendency to grow around the base of large trees. I think the area around trees tends to be free of leaves because these locations are slightly elevated and the trunk constricts the flow of air making the wind blow slightly faster. These observations suggest that the base of trees might be a good location for you to sow seed of woodland species like Hepatica, Dutchman’s breeches, or Bedstraw.
As I walked through the woods I also noticed another pattern. The areas with Pennsylvania sedge were largely free of leaves. This wide-spreading-mat-forming sedge seems to deal with the problem of smothering leaves by creating such a flat surface that the leaves simple blow right across. In contrast, other taller grasses catch the leaves like a snow fence but are not smothered because of their height.
It is apparent that leaves are virtually absent in certain spots and are very thick in other locations. The accumulation or absence of leaves in woodlands is very much like the shifting of sand in dunes. How this relates to where seeds of specific species should be sown is quite a complex problem. The best location to sow a given species may not only depend on slope, topography, and wind pathway. The best location could change over time as vegetation develops.
http://www.jstor.org/stable/2259827?seq=1#page_scan_tab_contents
ReplyDeleteAbove is a journal article that discusses the redistribution of leaf litter. Unfortunately, my previous discussion and the article in the link do not apply much to your situation since your site does not appear to have much slope.