El finale

Jan. 3 8:10AM 48F

This is my last visit, it's not nearly as cold as one year ago. I've sat here watching a deer browse the hill slope above me, 3 squirrels chase each other all over a snag, a turkey vulture ride the thermals just about the tree canopy. I hear a few songbirds but can't put eyes on them.

I think about what's changed in or around the mandala over the past year. It's gotten wetter through the wettest year on record. For the second half of the year, there's always been standing water near the mandala. The soil's been soft, rubber boots a necessity. Several big trees have fallen nearby and just recently a 9" diameter limb on the mandala's edge. The stream has changed course a bit, scoured by flooding and held up by natural debris.

What hasn't changed is the solitude of this forest, a simple retreat from the suburban hustle and campus bustle. As peaceful as this spot is, it cannot escape human influence. Most days, anthropogenic noise exceeds that of nature. The accumulation of trash is no less than disgusting. ORV use is perhaps the most disturbing as new trails appear and old trails become deeper and more eroded. I worry about the future of this little piece of forest with new campus development expected soon.

One of the other things that hasn't changed is my pleasant surprise at what the trail cameras have caught passing through the mandala. Of course there have bit a boat load of deer, and though we knew they were around, we've seen lots of foxes especially recently. I've found lots and lots of raccoon tracks in the area but haven't caught too many on the cameras. Apparently they use different trails than larger species, largely sticking to the water's edge. Coyotes too. Certainly they were here but now there's photo evidence. Perhaps my biggest surprise from the cameras was the great blue herons in the tiny tributary along the mandala. These cameras have helped to show a bit of what we don't know - pieces of the foodweb that remain out of sight and out of mind. We can be sure that there's much more here than we can easily observe. That's some of the beauty of ecology, the mystery, the complexity. That's why I do this, and why I'll be back.

My mandala perch

Got deer?

Dec. 13 10:40AM 46F

This morning's visit to the mandala offers a reprieve from finals week's exams and grading. The building is much noisier than usual this morning. The mandala offers a stark contrast. There's little obvious activity here now. I saw a squirrel from a distance, heard/saw two birds nearby including a woodpecker bouncing on a small branch just below the tulip's canopy above the mandala, also heard crows farther away, and spooked two deer on my walk to the mandala. On the log below, I found the remnants of somethings dinner spread. Critters are certainly around but probably hiding in plain sight.

Since my visit ~3 weeks ago, nearly all leaves have fallen, just a few stubborn oak trees holding on to brown leaves. Old tulip flowers are the most pronounced thing in the forest canopy now. On the ground, there are fresh white and red oak leaves, less fresh tulip leaves, very fresh tulip seeds, plus others of course. There's still some green on the forest floor, the easiest recognized belongs to multiflora rose. I don't appreciate its thorns or invasive status but I have to respect its heartiness. I discovered a boxelder hanging over the stream, a species that I haven't encountered too often.

Around the mandala, deer appear to be some of the most abundant, visible animals. Certainly there are many more invertebrates that escape casual observation, perhaps small vertebrates too. Maybe a better descriptor would be impactful. Again, there might be other animals that have greater ecological influence over the mandala but that's difficult to imagine. The effects of deer are born of their abundance and activity, both of which are strongly evidenced here. First, I originally chose this mandala location because of the apparent wildlife highway passing through here. There are always fresh deer tracks and the trail cameras offer ample pictorial evidence too. Their pattern over the year has been interesting, as the fawns appeared in early summer and then the bucks appeared in numbers and the does disappeared during the rut. However, I cannot find piles of deer scat in the mandala. So, they pass through, eat some snacks here but don't poop? Perhaps it's hidden under fresh leaf fall but that doesn't seem likely. Maybe our deer follow the Leave No Trace ethic and don't go near the stream, but that's equally doubtful. A group of students in my intro biology" ecology lab this semester systematically counted deer poop in habitats nearby and estimated 50-500 deer per square mile. Those are incredible numbers, though based on some big assumptions regarding the number of times deer poop in a day and how long that poop persists in the environment. Regardless, certainly there's an abundance of deer here. Second, the deer here have a big impact on the mandala through their activity. There's a distinct browse line with very little green between 1-6 feet aboveground. Presumably, deer are heavily browsing in this range, effectively erasing most of the green, though some persists and much of this looks to belong to unpalatable non-native species. Looking through the mandala, its easy to find browsed seedlings and shrubs. From a colleague that's studied deer, I learned that the deer browse is fairly easy to distinguish for the lack of clean break. They leave a rough break due to tearing, rather than cleanly cutting twigs. In sum, it doesn't seem like the forest stands much of a chance, at least with respect of regeneration. We've built an environment that benefit deer, from the eradication of natural predators to creating ideal edge habitat. The rough density numbers above are way above the 10-15 deer per square mile that forests need in order to be able to regenerate. What will happen to this forest as the big trees die and fall, will there be saplings to take their place and fill the canopy gaps? The likelihood of that seems slim considering current patterns of deer.

Autumn

Nov. 21 1PM 50F

It's pretty quiet here today, or at least it seems so. Campus is deserted for the Thanksgiving break. The natural sounds of the mandala - the stream, leaves in the breeze, are overwhelmed by traffic noise, sounds from the construction concrete plant nearby, occasionally of airplanes. Such a tranquil setting can't escape the human bustle.

We're in the thick of autumn now. It both looks and feels that way today. Less than a week ago, the mandala was covered in snow but there's no longer evidence of the short-lived early winter storm. One of the biggest seasonal changes in the forest has been steady leaf senescence and leaf fall. There are still leaves on the trees, more than I expected. Most are a dull brown, likely from the oaks. A large white oak not far away still has green or mostly green leaves, as do a few other trees but these are by far the exception. As the breeze picks up, leaves continue to flutter to the ground, accompanied by abundant tulip poplar seeds. You can still see the tulip's flowers, like ornaments in the canopy. The leaf fall has bee accumulating on the forest floor, representing a substantial nutrient pool. Just a month ago, the ground was mostly bare having been scoured by the late summer flooding. The waters washed away old decaying leaves and their nutrients. Does that loss hinder nutrient uptake in the next season? It would be interesting to have a good record of soil inorganic N and mineralization rates to see what effect, if any, the flooding has on the soil nutrient pool There may be other effects too, like an input of new sediment or a shift in the microclimate following the removal of the soil's organic horizon. But now it's fall, and the O horizon makes a comeback. The leaves and the nutrient pool that they represent are back and beginning to fuel the decomposer food web and the recycling of nutrients from the trees back to the soil.

The leaves themselves only contain a fraction of the nutrients that they had a few weeks ago. As fall progresses and days become shorter and temperatures drop, the green leaves lose their green. The chlorophyll that gives the leaves their greenness breaks down, unmasking other pigments in the leaf, exposing the reds and yellows from anthocyanins and other pigments, the fall colors we so cherish. These nutrients that form the building blocks for the trees photosynthetic machinery are broken down and stored in the perennial tissue of the tree. This is an important nutrient conservation adaptation whereas deciduous trees recapture about half of their leaf nutrients to use the next year. While the leaves are generally somewhat disposable, at least in comparison to the longer-lived coniferous leaves, the plants still recycle much of the leaf material.

So then you have two pathways from which trees get their nutrition each year: leaf fall and decomposition or resorption. It makes sense that trees in infertile habitats will conserve nutrients and rely more heavily on the resorption pathway, and in contrast, trees in nutrient rich habitats will take up the majority of their nutrient demand from the soil through roots. Unfortunately this isn't easy to research and what has been done isn't entirely conclusive (though some of my previous research has documented modest nutrient conservation via enhanced resorption in relatively nutrient-poor habitats). In the mandala, I generally expect that the soil here in the floodplain is relatively fertile as the nutrients from uphill leach downslope. I wonder if the falling leaves here compared to up the hill might be more nutrient rich, representing less resorption. If that's the case, we could argue that the trees here are utilizing the decomposition pathway more than the upslope trees that rely more on the resorption pathway. While these patterns can be stronger confounded by species or functional group (e.g. deciduous vs coniferous species), the trees here are common throughout and could offer some insight into these processes.