Friday, March 17, 2017

The Nature of the Unnatural

Earlier last week, I set out for the Ozarks for two days of checking firelines. Driving south on a 30 degree morning in early March, I noticed very little green on the landscape. The roadside fescue was starting to green up, henbit had turned tilled fields into swaths of lavender flowers, but along a long stretch of the 150 mile route, the roadsides were a homogeneous deciduous winter brown. Well, winter brown interspersed with a few cedars and the stark white billowing flowers of Bradford pear trees, trees that stuck out sickly sweet from the otherwise winter landscape.

Around seven years ago, I had heard that Bradford pears, the fast-growing non-native landscape tree that always maintains a perfect lollipop tree stature, were showing up deep in the Ozarks in vegetation sampling plots. Efforts to eradicate them from disturbed areas continue, but landscapers still choose this flowering and fruiting tree for horticultural instant gratification. And now they're spreading everywhere. On March 8, they were the only flowering tree on the landscape barring the early bud break of serviceberry, mostly found in nicer intact woods and certainly not as prevalent as the persistent Bradford pears along the highway. In fact, during two days of hiking through high quality natural areas, I only encountered a couple serviceberries in flower, always among the first of the native spring trees to bloom, usually three to four weeks earlier than dogwood.

Considering that so much of our landcover has been disturbed by logging, grazing, interruption of natural fire regimes and development encroachment, it came as no surprise that I could take this classic photo of what would happen if we stopped managing our native places and allowed homogenization to occur on a landscape scale. Dominant plants to include bush honeysuckle, Bradford pear and cedars with nothing in the understory, and any native flora clipped off by Missouri's ever-burgeoning deer population, maybe some scattered plants like broomsedge, wintercreeper, and the weedier Geum. But this was on a roadside next to a grocery store which I had stopped into for plain Greek yogurt and some peanuts for the field.

Nevertheless, with so much development pressure in the Ozarks, fragmentation, lack of fire, and exotics (and deer overpopulation), many of our native settings are turning into this. Away from the lot next to the grocery and in a 17,000 acre nature preserve to conduct browse surveys, I encountered cedar trees that had been browsed so heavily by deer in the absence of other food that they looked like alien trees. When you encounter a cedar that looks like this, there may be too many damned deer.

Unnatural levels of deer herbivory as a direct result of too many deer on the landscape, the lack of predators and increased biogeographical islands being formed by development pressure will result in serious overbrowsing. At least I only saw serviceberry and some scattered spring ephemerals in flower here rather than a greening out understory of bush honeysuckle and Bradford pear.

So, as is customary of exotics in the Ozarks and elsewhere, the Bradford pears and bush honeysuckle were triggered to break dormancy because of the warm weather. With climate change occurring on our clock, the warm spells in February and the first week of March lasted a lot longer and were warmer than in years past. But the bulk of the natives seem to be smarter than to come out when the threat (and reality) of 15 degree nights are still probable and likely in March, our traditionally snowiest month, with the last frost-free date not until mid-April. The shading out of the woodland floor by bush honeysuckle and the allelopathic nature of the rootstock are the precise reasons landowners in the Ozarks need to be worried about this wave of a closed canopy-thriving exotic shrub. Our spring wildflower displays are usually so incredible because the spring wildflowers are able to break through the leaf litter during early spring because there is no shading from the oak and hickory-dominated canopy. Bush honeysuckle puts an end to that.

This week, when the temperatures plummeted to the teens and highs just barely above freezing, the Bradford pear flowers all burned, straight to brown. Every time I see a browned out Bradford pear, I smile, knowing that now that the flowers are toast, they probably won't be pollinated, which means this year they won't produce fruit, which means birds won't spread the seed at least this one year. Sadly, the bush honeysuckle is still thriving. Passive management just may not cut it anymore if we want to keep natural areas full of native nature.

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