Thursday, December 1, 2011
What Can You Learn From an Old Field?
To a farmer like my grandfather an old field was just that - a field that wasn't being used for growing crops or for even allowing cattle to graze. It just sat there and became, well, old.
Curtis and his students however recognized old field communities as one of the principal building blocks of the evolution of plant communities. Old fields are where the first seeds of growth take root after land has been disturbed. Old fields are where saplings take root and if they are lucky over time turn into trees that become part of a forest. With time microclimates are created in old fields and what may seem inconspicuous to the untrained eye become an essential part of where we are.
Lets imagine an old field. In that old field there are plants that some would call "weeds" and others would call early invasives and still others would call them evolutionary building blocks. After all were it not for all of these primimal communities what possibly could follow.
Old fields are home to things like mice and like snakes. Creatures that to the uninitiated are "icky" and that have no value. However to a biologist a snake is an essential part of the environment that eats rodents before they become too many. Mice eat herbs and keep those herbs in check. If they didn't soon there would be more herbs than an area could handle. Lots of mice attact predators like gray foxes (or red foxes further north) and the foxes soon find a cornicopia of food items on which to feed themselves. Meanwhile larger herbivores like rabbits munch on the taller grasses and soon all of the rabbits attract great horned owls. Owls take the rabbits and keep them in check and then the owls themselves die and recycle their nutrients back into the soil. What was once a ferocious great horned owl is soon reduced to a pile of feathers on a hillock in an old field where its body decomposes and feeds the grasses that feed the mice and the cycle begins anew.
It becomes a cycle within a cycle or more accurately a cycle within a circle and we all are a part of that cycle and the circle.
This morning while completing 5 miles of my normal 9 mile hike (I had some higher priorities to take care of so I cut my walk short) I walked by the old field community shown in the picture above.
There to the untrained eye was a multitude of grass and maybe some shrubs and that was it. To most people it was just a place that was and had no purpose.
Aldo Leopold is considered by many to be the father of wildlife biology. From humble beginnings in Burlington Iowa, in 1888 he rose through the ranks and was first a forester and then finally a professor of wildlife biology at the greatest college on earth - the University of Wisconsin. Leopold was an ecologist in the strictest sense of the word - ecology isn't about saving baby seals from being clubbed to death for their fur as so many think. Ecology is about understanding the interaction of an organism with its environment.
A colleague of mine when I first started working for the US Fish and Wildlife Service in 1977 honored me one day with a tale about taking a graduate level course from Leopold. I don't remember the courses name but that is not important. The course was all about how organisms interacted with each other. After spending a grueling semester trying to understand how all the parts, no matter how seemingly inconsequential, fit together, Leopold took this students out to the field for their final exam. I don't remember now how much of the final grade was to be dervived from that final exam but Leopold knew how to find out just how much learning his students had accomplished as opposed to how much they read.
For the final exam they walked to an old field community on the arboretum of the University of Wisconsin at Madison. There Leopold made his students take out a pen and paper and as he he looked across the landscape he asked his students a simple question - "Tell me what happened here." That was his final exam question. As the story goes most of the students failed the final exam because they didn't get it. Leopold wasn't interested in theory or what someone recently published in a paper or what the latest buzz was from his colleagues at the University of Wisconsin Department of Wildlife Biology. He wanted his students to look at an old field and tell him how it came to be, where it was going, why it was going there, what perils laid ahead for the creatures in the field, and most importantly, if evolution was allowed to follow its course, what that old field of weeds and saplings was going to look like some day in the future, no dobut when Leopold was long gone.
I remember vividly in the fall of 1975 when I was a graduate assistant in Wildlife Biology at the University of Wisconsin River Falls. There my major professor gave me the assignment of preparing the final exam for that quarter's class. At the time I did not know about Leopold's final exam question some thirty years earlier on a Dane County old field. Instead, I walked students along the banks of the south fork of the Kinnikinnic River. There we encountered a colony of beavers. The beavers had done what beavers do - they chewed down trees, they built dams, they made winter food caches and they just generally went on about being beavers. I still remember looking over that beaver colony that afternoon and asking the students "Tell me what happened here."
Several of the students gave a strong argument for the need to trap beavers to keep their population in check. But trapping beavers wasn't the question. Not too many students got an A on that final exam.
What happened was that evolution took control and converted things that were into things that are. Given the opportunity for evolution to move forward unheeded there would soon be trees where saplings stood and there would be annual plants (like wild ginger) growing where saplings had been and there might be great horned owls nesting in trees that on that day only supported field sparrow nests on a weak branch. Maybe some day Baltimore orioles would be nesting in those same saplings that then were easily crushed by an over zealous foot.
All those things were there and all those things are possible and with luck and the passage of time all of those things will come to pass. But today they are just a thought. They are a plan in someone's mind that if x and y really equal z all of these wonderful things can come to be. Baltimore orioles will sing where today field mice cower in fear of a gray fox turning them into lunch.
Life and the relationships that come and go with it are very much the same. That old field that I will see tomorrow when I go on my daily walk wlll still be there. Mice will be hiding and great horned owls will be pondering and saplings will wonder (if a young tree can actually wonder) if they will be around tomorrow to watch the drama of life unfold around it.
Despite how we view things in our lives we are all an old field evolving from what was into, hopefully, what we can eventually be. Some times we make mistakes and some times we fail and many times we succeed. However to get to where we can succeed we have to go through trial and error and get our saplings beaten back and have our prairie grasses eaten short by someone who at the time is stronger than us. But in the end, if we are wisened by our experience, we can all pass Aldo Leopold's final exam question and explain to everyone who asks what we got to see because we took the time to find out how it got there.