Sunday, December 17, 2017

Gardening The Woods

There may have been a moment (or two) when I looked at my field of garlic, its plethora of weeds, its need for harvest, or even the bare soil in need of turning, and felt overwhelmed. Gardening the woods doesn't meet that level, it exceeds it. It is farm work spread over a decade -or more. In spring I garden the garlic mustard and in fall, I start on the buckthorn.

I refer to this process as gardening because restoration is a fallacy. There will be no restoration, only limited choices, however informed by research and good intentions. My work amounts to weeding, seeding, planting, observing and acting like any gardener would. My preference for plants native to this biome is practical and aesthetic. Practical because they are survivors that, once established, do not require my care. Aesthetic because they become part of the whole and offer surprises. I like the unexpected.

The oldest buckthorn trees line the edges of the sunny, wetland clearings where birds congregate and eat from a quantity of berries. Under roost trees, seed density can easily reach several hundred per square meter and sapling density averages 100 per square meter. As the birds move through the woods, so do their droppings. Consider the image, above, a map of bird roost sites, droppings turned young saplings in a green stream flowing north.

This panorama shows the stream of saplings progressing northward from the great wetland. It follows the bird flight pattern, but also the soil moisture of a seasonally flooded depression that in turn takes out trees that enables sunlight to hit the forest floor, increasing germination and growth. Yes, the buckthorn does grow up the slopes, perpendicular to the stream, but sporadically compared to the edges of the vernal pooling. However, in time and without my gardening, the whole of the area will become a thicket as these saplings mature and produce berries to seed the slopes.

It is early November, when all native deciduous plants have dropped their leaves in preparation for winter. This makes it simple to identify the greenery above as 100 percent buckthorn. On this southern slope, descending to the great wetland, the age diversity of buckthorn increases dramatically, topping out at mature, multi-stemmed, 25 foot trees at the wetland edge. Why such an incredible age difference merely 40 feet away? It may be because our woods have seen several mature oak trees come down over the last twenty five years, opening light to the forest floor and eliminating a thick cover of oak leaves that studies suggest limit buckthorn seed germination. More sun has broken the lowland canopy as our once considerable bank of green, black, and white ash trees die off due to emerald ash borer spreading since 2002. Dead or alive, felled trees take out additional trees as they come down, further enhancing the light hitting the forest floor.

An impenetrable thicket wasn't on this slope ten years ago. In summer, 2012 a thunderstorm took out two large oaks that were, maybe, 150 years old each. In five years this is what has become of the buckthorn seed bank.

The reason for Rhamnus cathartica's success? It outcompetes in photosynthesis, carbon gain, shade tolerance, light tolerance, moisture tolerance, earliest leaf out, latest leaf senescence, seed production, female to male ratios, age to fertility, germination rates, and mortality. It also germinates well in the particularly barren late summer soils of our mature forests, a by product of non native earthworms and growing deer populations. It's leaves are higher in nitrogen, decompose faster, and are eaten by the worms first, quickly cycling nutrients under buckthorn stands. It has no issue with anthropogenic disturbance. This plant does not create thickets in its native ranges, but it does in the midwest where it responds to fertile, calcium rich, mineral soils. As plants go, buckthorn has a lot going in its favor.

So why go after it? Why commit so much time and labor to removing it (no easy task)? Again, I liken it to the garden. Imagine your garden was only hydrangea, everywhere hydrangea, but this hydrangea never flowered and had thorns. Who would want a garden like that? 

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If I do not respond to your comment right away, it is only because I am busy pulling out buckthorn, creeping charlie, and garlic mustard...