Fire, oaks, rare plants, and civilization - through photos

Sometimes as we stewards walk and look and think ... we take photos, so we can share the thoughts they illustrate and ask for feedback and discussion. This post resulted from such a walk. 

We had hoped for a burn.

This mowed path is the 2024 firebreak through the savanna. We'd hoped for a good burn in the fall. Much of Somme Prairie Grove is too wet in spring for an effective burn. Some sites got good burns in November, but we're short on human resources More volunteers and staff who are trained, experienced, determined, and deeply care are needed to give biodiversity the nurture it deserves.

What caused this?

Benefits and evils - of shade and civilization - are on display here. This old bur oak predates its new neighbor, Dundee Road. When this tree was young, a couple of hundred years ago, there was shade to its left (east) but open prairie to the right (west). Huge old limbs survive to this day on the sunny side. Limbs on the east were amputated by shade of other trees (though, thanks to recent restoration, new limbs are sprouting there). 

As for the road and cars and houses, civilization, using the word charitably, saved this preserve from the plow and the bulldozer. If it had stood well outside the metro area, it would almost certainly have become a cornfield.

Here again, that firebreak is visible, parallel to the road. We'll burn here only with a wind from the south. Smoke management is crucial in the midst of a major population center. But it is the great numbers of people that, through a process like panning for gold, end up rising to the occasion and providing the expert volunteers (and funding and staff) that make all the difference.

There are many more preserves in the metro area than in most rural counties, and it's more challenging to burn them, but much more of them get burned. 

Who trampled this? 

Two months ago, this area was tall, rare and uncommon sedges in an ephemeral pond. But it's a natural amphitheater, and every fall the bucks trample it to dust as the potential mates watch them compete from the high ground. Animal impacts on the plants are natural influences.

A drama under way

This south-facing savanna slope has more formerly-threatened savanna blazing stars (Liatris scariosa) than anywhere else in the preserve. So for years we pulled sweet-clover but chose not to broadcast seed, thinking it was better to leave well-enough alone. A few years ago we decided that we were just delaying the inevitable. This area needs a conservative turf to "be all it can be" and sustainable for the long term. So we broadcast the savanna seed mix.  It now has small, young warm-season grasses (dropseed, little blue, Indian) along with obedient plant, cream gentian, leadplant, rue anemone, and meadow parsnip (Thaspium). We're eager to learn as we watch it mature. 

A Tale of Two Trees

They're side by side. On the right is a Hill's oak, many skinny re-sprout stems up to three feet tall. They'll burn off again this year. On the left is a bur oak, one solid trunk about eight feet tall. 

Many years ago these two oak were the same size - about two feet tall. For some years we chose to protect the bur from fire and deer. It's now large enough to protect itself. A farmer had cut down most of the trees here prior to Forest Preserve acquisition. But savanna biodiversity here needs bur oaks scattered here and there, as discussed in more detail below.

Playing God With Oaks? 

Some accuse us of "playing God." Oh, please. The oak on the left with the impressively thick corky bark (uncomfortably in a cage for now) is more needed by this savanna than the still-leafy Hill's oak on the right. Scattered mature trees provide the full-to-dappled sun needed for savanna biodiversity. For three decades we said, naively, "Let the fire decide." If we'd been willing to wait a hundred years, perhaps chance would protect some trees. But for three decades all the young oaks burned off with every fire, and then the over-populated deer ate the re-sprouts mercilessly. This oak is nearly big enough to be released from its cage.

Freedom! 

Indeed, this bur is now free of its cage. I easily count fifteen Hill's oaks that are still burning back to shrubs with every fire. They're fine. Oak shrubs are part of the savanna habitat.  

Who did this!?

This oak was mutilated by buck deer, wreaking havoc with their antlers. They practice that way. You can see that this one was scarred years ago. This time the damage may girdle and kill it. We place cages at "antler height" to protect them from this until they're a bit bigger. Once the trunks are big enough that the deer can't bend them, they lose interest.

Why do this?

We cut - but did not herbicide - a Hill's oak that stood among many others, jointly making shade, as they grew bigger annually, too dense for the savanna vegetation that survived beneath them. In ages past, when the wilderness burned sometimes with much more intense fires, even larger thin-barked Hill's oaks would be "top killed" and start again as shrubs. But that was then.

Today, after too many decades of "not playing God," we cut oaks to reduce shade, so as not to lose the quality biodiversity that survived here (for an alternative see Sad Story, below). We cut most of the red oaks in this patch and about half of the Hill's oaks. 

Is this a high-quality savanna or woodland turf? 

A few feet from the re-sprouting oak above. It may not look like much today, but it is a diverse mix of conservative species. Some of those found here include:

Bent grass (Agrostis perannans)

Rue anemone (Anemonella thalictroides)

Meadow parsnip  (Thaspium trifoliatum)

 Robin's plantain (Erigeron pulchellus)

Savanna blazing star (Liatris scariosa)

Wild licorice (Gallium circaezans)

Cream gentian (Gentiana alba)

Wood rush (Luzula multiflora)

Grove sandwort (Moehringia lateriflora)

and many, many more (Plus plura)

Sad story

In our early days studying the savanna at Somme, this area was one of our treasures. Lots of New Jersey tea, violet wood sorrel, purple milkweed and other savanna species under the young trees. We made sure to burn it regularly. We monitored it with intensive quadrat sampling. We pulled all garlic mustard and sweet clover, now gone.

Then it died - or lost all its quality species. It was like the frog-in-boiling-water metaphor. We didn't notice - focusing elsewhere - because we thought it was great, and we were giving it all it needed. Shade slowly increased and increased. Trees grow. Finally we started girdling too-dense and too-shady trees (mostly bitternut hickory and red oak), like the tree second from the right here. But we were too late. Tall goldenrod took over. Here we and the ecosystem are starting again. 

Fortunately, we learn. Ecosystem health is as complicated as human health. More complicated, actually. Good stewards make fewer and fewer ineffective decisions. We celebrate more and more returning diversity and health. 

More sad story, but yet hope

The tree on the right is a red oak, dead, killed by fire, or something. On the left (skinny and pale) is a bur oak that grew like a pole, barely surviving, in the shade of the red. This beanpole bur is a pathetic specimen. But now, thanks to the death of that "red oak in the wrong place" - it's branching out and may have a fine future here. Studies show that the bur oak is the keystone tree species of the rich-soil savannas and woodlands here. 

Who killed these trees?

We did, of course. They were invasive black locust. We thought we could just girdle them, but the locust needs herbicide too. They've been dead for at least three decades. It's remarkable how they're still standing after all that time. One's even burned a bit but stands yet. All this takes sweet time. 

Two Fine "Prairie Grasses"

In the open savanna, warm season grasses rule. Richly russet little bluestem on the left; a fine-leaved clump of "prairie dropseed" on the right. 

Knowing the grasses helps the winter landscape speak to us. These two are among the best indicators of quality. If an area has none, we want to broadcast seed there.

It seems to trouble some people that the principal open savanna grasses are called "prairie grasses." The grasses are misnamed, because savanna consciousness arrived late. To be clearer, perhaps these should be called "warm-season" grasses. 

Five Fine Savanna Grasses

Four of them are warm-season grasses.

Little bluestem - richly russet

Dropseed - fine-leaved pale clumps

Indiangrass - tall and with an unbranched top

Big bluestem - tall and with a branched stem

But the fifth (and especially classy) grass here is Leiberg's panic grass, a cool-season grass. It has the palest leaves in this photo, short little leaves, for a grass. 

Though this area is rich in colorful rare flowers, butterflies, and birds. It's good to learn those grasses as they're key to savanna fire and structure. As we study and plan in the winter, they help us think.

And speaking of thinking, just for the fun of it, here are two last photos of what this area will look like during the next growing season:

Late June

Early September