If plants had religion, oaks would be shamans. Human history is thickly forested with sacred trees, and no other native Great Plains presence symbolizes the aspiration to traverse the realms of heaven, earth and underworld. In this, bur oaks have no equal, being unmatched in longevity and reach. And they have another eco-mystical ability. They can enter and occupy a wide range of distant and forbidding habitats. Unlike other oaks, bur oaks are unperturbed by prairie fire, alkaline soils, drought, big bovines and competition by deep-rooted grasses. Even at their northwest extreme in Saskatchewan’s Qu’Appelle Valley, they survive hardship and the passage of time better than any other native tree. Spiritual leaders of the First Nations bear the ancient wisdom that empowers them to navigate unseen realms and to sustain the spirit of their communities. They emulate bur oaks.
Bringing Stones to Life
Life is made possible by the ancient power of photosynthesis. All plants synthesize sugar and release oxygen with the sun’s power; trees have done this above and beyond other plants since the primal advent of wood. Another solar-powered process is vital for life on earth. Plants transform essential mineral elements into usable and accessible forms. By harvesting the sun, trees bring stones to life.
These essential elements are particles from exploded stars that aggregated in deep time to form the earth’s rocky crust. Mineral particles have to become small enough to be dissolved in water so that they can enter the roots of plants. Some of this happens through atmospheric and geological action, but the real work is done by plants and their living soil partners. Roots grow into rock crevices and break them as they elongate and expand. They also release rock-dissolving acids mixed with sugary compounds. Root exudates also feed soil fungi and bacteria that aid in the transformation and acquisition of mineral elements.
The rock-dissolving capabilities of plants and their associates are impressive, but most of the elements that plants require are recycled from organic matter. The failure to grasp this might help explain why so many people rake and dispose of leaves that fall on their lawns, then apply synthetic fertilizer and mulch to their landscapes, or pay someone to do all this. Native soil fertility is created by the digestion of leaves and other plant and animal debris. Humus is the result of organic matter (mostly the shed parts of plants) being consumed and expelled over and over again by smaller and smaller organisms. At each stage, compounds are released and reduced to particles small enough to be taken in by roots with the help of beneficial fungal infections. It is not an exaggeration to say that plants in partnership with soil organisms make the soil they need to grow. Bur oaks do this on a grand scale, often in places other trees must struggle simply to survive.
The impact of a mature bur oak on native soils is hard to fathom when one takes into account the huge and ever-increasing rhizosphere (the area of soil occupied and directly influenced by the root system). Exudates are released at the root tips where beneficial infections create fungus-root organs that increase root surface area and function. An old bur oak can have more than 100 million infected root tips, and these connect to an extensive fungal web in the wild. In the context of a community, it’s hard to say where a single oak begins and ends.
An old bur oak grows in Sarpy County, Nebraska. It was known by the aboriginal peoples of that place and by the Europeans settlers that drove them out. It has survived countless storms and natural disasters. It has witnessed cattle drives, wagon trains and all-terrain vehicles. A rail line, complete with depot, was built a few hundred feet away and dismantled after many decades of use. Sadly, it has recently faced a newcomer that threatens its survival: the half-ton pickup.
I first encountered this earth-mother oak during a botanical study I was conducting for a government agency. Surveyors had recently driven just outside the edge of her canopy, and a parade of mowers and managers followed. A large, corresponding part of the canopy had died and fallen. Branch shedding is a common symptom of root injury and disease in oaks, and often indicates an irreversible decline syndrome. Savanna oaks like this one typically have low, spreading crowns. The canopy reached at least 30 feet in each direction, and the root system of this tree extended much farther. The immense root system of an old oak is both an asset and a liability; the huge expanse of rhizosphere is vulnerable to many mechanical impacts.
The equipment corridor was well outside what many would consider a safe working distance. Planners often make tree protection zones coterminous with canopy spread; this is the “drip line” approach. Advocates of this method clearly underestimate the size and sensitivity root systems. Seizing this tragedy as a teaching opportunity, my colleagues and I designed a protection zone that calculated distance and shape according to species, age, size, soil conditions, drainage and other factors. Trunk diameter measured 48.5 inches at standard height, and the resulting protection zone reached 110 feet from the trunk in all directions.
But distance really isn’t the point. Many developers, including the agency seeking to “improve” the land where she has been growing for a couple hundred years, show little flexibility or interest in meaningful tree preservation. Centuries of ecological wisdom and the promise of a fertile future are easily sacrificed for building projects that will not stand the test of time. Saving oaks requires seeing them for what they are and what they mean in human and in evolutionary history. Oaks are saved with wisdom. And desire.