Hepatica – speculation – conservation

Many oak woodland herbs are green all winter. Few prairie plants are. What might that contrast tell us about conserving fire-maintained prairies vs. fire-maintained oak woods? 

This post has a few observations and questions. Mostly it raises possibilities and considers experiments. It takes a stab or two at practical conservation issues, but it's mostly a nerdy celebration of very early spring flora .

To obtain the photo above (in early April), I first had to rake off most of the leaf litter. Underneath was "a surprise" – those hairy, green and bronze-purple leaves in a solid carpet. They are robin’s plantain – an uncommon species of oak woods. (For scientific names of species of this post, see Appendices 1 and 2.) Before being uncovered, the green leaves were invisible, underneath brown. Why stay green if you’re in the dark?

The above photo is one before raking. Mostly brown, but notice a couple of green "tongues" sticking out. For comparison with the next photo, also notice the curved stick, upper right. 

There's that same curved stick for reference, and now, with dead leaf duff mostly removed, a treasure. Other spring flora may be barely starting to emerge, but those big luscious, three-lobed hepatica leaves have been green, underneath all that brown deadness all winter long. This spring, we stewards uncovered some, as we did here. Is such “improvement” on nature helpful? Or perhaps harmful? See discussion below. 

To see the early diversity in this photo, note shining bedstraw (tiny-leaved whorls) and spring beauty – very narrow, simple leaves which emerge a dull purple and then turn green. One green spring beauty leaf is clearly visible (if you zoom in) beneath the acorn at center right. A dull purple one crosses the hepatica leaf to its left. The very long, thin leaves almost everywhere are Penn sedge.  

Formerly common, hepatica is now rare in the North Branch woods, and in many damaged woods. As we try to restore rich biodiversity, we rightly focus especially on conservative species like hepatica. But at Somme we have so few hepaticas (about thirty, at last count), and they reproduce so slowly. We think maybe it's worthwhile to try to help. Yes?

And yet, our human manipulation of nature has a checkered history at best. Yes, much restoration is now demonstrably successful. But at each step, we need to ask whether we do more good than harm.

Perhaps we should also admit that we remove the duff in part for emotional reasons. It’s like a peanut hunt rewarded with little salvations. Do we successfully release some of our few hepaticas for an earlier spring? Perhaps they’ll be a bit healthier and produce more or fatter seed? 

Last winter, we rashly experimented with the one plant that conveniently grows beside a main trail. That experiment consisted of removing accumulated dead tree leaves from time to time all winter long. That plant is shown below, in April. 

After this treatment, the leaves are not green, but neither are they lifeless. Truly dead hepatica leaves shrivel and crumple into dust. These leaves have changed to a purple-brown, mauvish color, but they’re thick and “alive” looking. Many winter-hardy leaves turn reddish or purplish colors and continue to photosynthesize. Was this plant harmed by the exposure – or did it benefit, despite now looking less robust than the green, duff-protected leaves of the previous photo? Note the healthy-looking, furry flower buds, ready to rise, where the leaf stems come together. (See Endnote: Experiments.)

And, by chance, Eriko Kojima sent me a photo of this same plant a few days later. The liveliness of those leaves in her photo are all the more apparent (below).

Oak Woodland Management Question

And now a broader question arises, not just about hepatica, but about management regimes for oak woodlands generally. The historic record is stingy in providing herb detail on original oak woods. But a fine paper by Doug Ladd on oak woodlands in Missouri (see References) quotes dozens of observers on various aspects. One haunting (to me) quotation from Joseph Nicollet, described the woods of 1845 along the Mississippi River near St. Louis this way:

“The slope of the hills on the river-side was covered by a growth of heavy timber, overshadowing an almost evergreen sward, free from undergrowth, which terminated gently in a point on the very margin of the river…” 

Hmmmm. Really? “An almost evergreen sward.” And, indeed, we see rare winter-hardy species increasing in some areas as we restore our Somme oak woods. Consider the clearly evergreen woodland phlox, below:

These bright-green-all-winter leaves were also mostly under the duff, but we find this phlox with many leaves peeking out and a) they don’t turn purple and b) they start growing again from their tips in spring. (Those winter-hardy hepatica leaves die as the season progresses, and, after flowering, each plant puts up fresh leaves that will live for the next full year.)

There are many other woodland herbs that have winter-hardy leaves. (See Appendix 1.) What happens when such green leaves get consumed by a fall burn? I don’t remember noticing many of them growing back afterwards. But what if that’s because our practice these days is to wait until most vegetation is dormant? What if we sometimes tried burning in early fall? Yes, we’d burn up the gentian and aster seeds, but they don’t need to reproduce every year. What if we found that, after a burn in August or September, a great many species re-grew, especially including those species that are green all winter?  

What’s going on here - physiologically? 

Why do many woodland plants keep green leaves all winter long, in the dark, under deep leaf litter? Whatever good could it do them? Why do few prairie plants do that? 

(And, aside from the pure science, might the answers tell us anything about the best burn regimes for biodiversity conservation?)

  

Here are some hypotheses: 

• Could it be that for millions of years, woods fires were often ignited by lightning in August or September (the most likely time for a conjunction of lightning and dry fuel)? May some species be adapted to re-growing leaves for the fall, winter, and earliest spring? 

• A few odds and ends of green leaves by chance don’t get covered by tree-leaf litter. Is it possible that they photosynthesize enough to be worth maintaining all those leaves?

• Might the covered green leaves be there for storage? Do resources from the over-wintering leaves end up in the new spring leaves once the plant sends them up? 

• Does enough sunlight actually penetrate the thin layer of leaves for some winter photosynthesis?

Every spring we wonder and marvel at our few hepaticas. But then as spring unfolds, one hundred other questions begin crowding these out. Maybe we'll have time, some year. Or you?

Endnote: Experiments

What might we want to do next?

Botanists with sufficient resources would have to tackle some of the above questions. But what preliminary observations might we want to make? And what simple science might we do to replace at least some of these speculations with data?

In each of the experiments suggested below, a person would want to select a group of “experimental plants” and divide them into two or more groups at random. (Note: “at random” requires flipping a coin or some other truly random process to place plants or groups of plants in the “treatment” vs. the “control” group. Putting them arbitrarily into groups "for no particular reason" is not random.) 

To answer the question "Does enough sunlight actually penetrate the thin layer of leaves for some winter photosynthesis?" how would it be if we cut off all leaves of some plants and leave them on others? Would the plants without winter leaves do better or worse, compared to others left alone?

If we were to remove tree-leaf litter all winter, would those plants:

• Bloom earlier – or later? 
• Make more (or less) seed? 
• Put up more (or larger) leaves – or the opposite? 
• Live longer – or die sooner? 
• Compete better (or worse) against nearby plants?

Would the results be similar or different if we removed tree-leaf litter in spring after the worst cold is past?

If the all-winter (or the spring only) uncovered ones produced better seed, got bigger, and lived longer, then we might be on our way to a useful answer. 

A curious and complicating observation to consider: plants that have somehow lost their leaves seemed to be the ones blooming early (from a very limited sample). 

In the scene above, there appear to be at least five hepatica plants with healthy leaves, now uncovered. None of them is putting up flowers. In contrast, two plants are putting up tufts of blooms, and neither of them has surviving last-year leaves. (Plants may have lost last year’s leaves when some animal ate them?) 

Endnote: Garden vs. Wilderness

The first and fifth photos in this post were taken in my "wild garden" seed-production plots. The plants may be more "larger than life" than most wilderness examples would be. For example, look at the robin's plantain photo below, from the recently burned Somme Prairie Grove savanna.

It appears that the fire, on a cool and humid day, burned lightly over some of the robin's plantain leaves. If the remaining half-burned leaves were raked off, a good deal more robin's plantain would be visible. But not so dense near-monoculture as in the photo that opens this post.

A winter-hardy alumroot in the seed production garden looks seriously dramatic.

Compare that to alumroot in the very high quality Somme Prairie:

Yes, it's beautiful and rich looking, but a good deal less triumphant.

I went to the prairie to double check my impression that few leaves there survived the winter.

Indeed, in most of the best areas there was little or no green.
But wild strawberry was everywhere.

Strawberry is definitely a champion - thriving in the best and the most degraded areas all the way from prairies through savannas to woodlands.
For a comparison with raking, I made rakes out of my fingers and raked a few areas.
Most showed bare dirt under the dried thatch.
But here's one before raking:

And here it is after my half-baked finger-raking. Sure enough, sedges here. Probably Mead's sedge, the commonest in this prairie.

And for this post's one last, lingering photo, the scene below contrasts the old year with the new. The green is nodding wild onion, survivor of the winter. Unlike the woodland plants, the green union leaves don't hide under matted duff. They stand up in the cold. Somehow. The frilly purple is prairie betony. Like most prairie plants it retreats back into its roots for the winter, but in early spring its feathery leaves survive freezing and frost just fine. Welcome back, betony.

Appendix 1.

Savanna and Woodland species that stay green all winter

Names below from Swink and Wilhelm

Aster shortii – Short’s aster

Blephilia hirsuta – wood mint

Carex species – sedges - albursina, blanda, jamesii, pensylvanica, springellii, woodii, what others?

Erigeron pulchellus – robin’s plantain

Hepatica acutiloba - hepatica

Penstemon digitalis – foxglove beardtongue (often cited as a prairie plant and grows well for a while in “prairie restorations” – but in quality habitats seems more of a savanna species). 

Phlox divaricata – woodland phlox (note: prairie phlox does not stay green)
Polemonium reptans - Jacob's ladder

Silene virginica – fire pink

Viola conspersa – dog violet

Species of both woodland and prairie– that stay green all winter

Allium cernuum – nodding wild onion

Carex  meadii  – Mead’s sedge

Fragaria virginiana – wild strawberry

Heuchera richardsonii – alumroot

References

Ladd, D., 1991. Reexamination of the role of fire in Missouri oak woodland. In: Burger, G., Ebinger, J., Wilhem, G. (Eds.), Proceedings of the Oak Woods Management Workshop, Eastern Illinois University, Charleston, IL, pp. 67-80.

Actual Flower Photos

A touchier-feelier version of this post - with sure-nuff photos of these hepaticas in bloom, is at https://vestalgrove.blogspot.com/2019/04/first-flowers-of-spring-be-still-my.html

Acknowledgements

Thanks to Kathy Garness and Eriko Kojima for proofing and edits - and to Eriko for that interesting extra photo.