Sunday, October 21, 2012

Buckthorn Kills

Or is that ugly green mess really more of a symptom?

Hundreds of species of animals and plants have been lost from this
formerly open white oak woodland, under suffocating invasive shade.
But neither buckthorn nor asphalt is the major threat to our remaining
October is a good time to teach people that the smothering green of buckthorn is an evil. But what about the claim that it's really more of a symptom more than a cause? More on that later. The fact is that buckthorn is easy for people to understand, so teaching about it is step one.

In the fall when it stays green later than everything else, everyone can see it. Buckthorn brush densely lines highways, parking lots, and any neglected corner. It invades people's yards. Once people know it, they swear at it, at least subconsciously, every time they see it. 

The wine-colored white oaks (right, above) cry out for help: "Get this stuff off of my ecosystem!" Long gone are the butterflies, birds, wildflowers, woodland sedges and grasses - and hundreds of other species that once lived here. While there has been no oak reproduction here for decades, at least the old trees survive to beg us to be stewards.  

In the scene to the right,
the buckthorn was cut from the foreground last spring. Hundreds of baby buckthorns then sprouted and were herbicided. The oak ecosystem will be 'restarted' by sowing the seed of wildflowers and wild grasses this fall. The two spreading trees in this photo are bur oaks. This species needs plentiful sunlight to survive as saplings. The smaller skinny trees in the foreground are red oaks. They tolerate some shade. No young bur oaks have grown here for decades.

The evil of buckthorn is obvious
on the right side of this photo, where it hasn't yet been cut. But another "evil" is less obvious on the left. Those yellow leaves are maple - as shady a character as buckthorn. Now we get a bit closer to the root of the problem. If the killer of these oak woods wasn't buckthorn, it would be maple or some other invasive tree. In the absence of burns, shade tolerant trees in the oak woods are like cancer cells, growing out of control, enough to kill the ecosystem.   

In parts of Somme Woods, all the oaks have already died. Here the young trees are basswood and ash. But check out the big trees with spreading branches in the distance. Survivor oaks are still nearby. Squirrels have been "planting" their acorns decade after decade. Soon, once thinning has provided enough light, "the oaks will rise again."

Elsewhere in this preserve,
outside the woods,
along the edges of the open grassland, hundreds of young bur oaks do indeed rise up. Notice prairie grass and dense wildflowers around this one. This great little tree grew in full sun. It's happy.

Back in the woodland we have the remains of a white oak. Oh, golly, my heart goes out to it. Look at those shade-killed lower branches, though the top (outside this photo) is still verdant and beautiful. Where are the other big old oaks with spreading branches? Only one is visible here - dead - lying on the ground - rotting into history. The anorexic young trees that stand behind it grew un-oak-like in the absence of fire. Nor are there many white oaks among them; dark bark means the skinny trees are mostly red oaks. Dense young reds are not as bad as maple, but they too mean the end of the white oaks woods -  and the end of the dappled-sun-dependent animals and plants that pal around with the big gray monsters. More fire would help this woods.

Lack of fire is the root problem. Buckthorn, maple and red oak are the symptoms. There is a "light hierarchy" among trees. Bur oak grows next to the prairie and needs the most fire and the most light. Then comes white oak - in open woodlands. Last is red, mixed with the maples where oaks are on the way out. Bur can't grow in the shade of white, which can't grow in the shade of red, which can't grow in the shade of maples and basswoods. Plants and animals need us to restore remnants of all types. White oak woods like this deserve to be opened up enough for the old white oaks to reproduce.

This is what grows under the buckthorn - seedling buckthorn and little else. Without fire, this is dead end for a formerly rich and beautiful woodland. If the understory were young maple, the result would be just as fatal, but not nearly so obvious to the casual observer.

Compare the monoculture above with the richness on the left. Where restoration has provided its benefits for decades, the ground layer supports a more than 100 rare plant species. Shown here: long-awned wood grass, Short's aster, and woodland puccoon (with all those white seeds). 

Conservative diversity means health to the ecosystem. With this richness, the birds and butterflies thrive. Oak seedlings rise slowly but surely. beating out the weak, small-seeded, fire-intolerant invader trees.

That's why we cut brush
every winter
and gather seeds every fall
to help the oak woods of Somme
heal their wounds
and burgeon
once again with diversity of life.

We rejoice at the recovery.
This is the home of the woodcock, blue-spotted salamander, Bicknell's geranium, and hundreds of other species of now-rare plants and animals.
And we are none too soon. Look at the state of these oaks! We can almost hear them gasp:

"Oh, thank you for making space for our seedlings. You rescued us just in time!" Really? Ancient trees are that thankful? It's so nice of them to appreciate our work. 


Anonymous said...

Stephen, The aspect of buckthorn that makes it worse than Maples and shade tolerant species of oaks is the fuel quality and leaf retention. The litter under buckthorn either does not burn or burns poorly. In addition to Buckthorn leaves being a very poor quality fuel, the fact that buckthorn retains its leaves so late in the year means it shades the fuel. The prevention of sunlight incidenting on the fuel keeps the fuel from drying properly during prime burn season.

In contrast, the leaves of maples, basswood, and red oak will burn well. Regular burning prevents these species from regenerating shifting the balance back to the oaks. Thinning of these species on South or West facing slopes is often done to speed this natural shift. However, in ravines, on the east side of water courses, or east facing slopes fire intensity is reduced and these native species do have their place.


Anonymous said...


Since you have amphibians to consider for your management plans, the results of the following study many interest you.

Buckthorn is directly impacting the ability of your amphibians to reproduce.


Mary Ann said...

Thanks for this great description of the restoration. It gives me hope.

Stephen Packard said...

Thanks for the good comments. One point I was trying to make, that I may have left obscure, is that there is a complex set of relationships among causes and symptoms. While I think of buckthorn as a symptom of lack of fire, it creates its own stresses. For an ill person, a fever may be "just" a symptom of some infection, but too high a fever can kill you even if the infection would be cured by your body's defenses, if they had time to do their work.