A Case Study: How soils form on glacial plains
The most delicate and unique landscapes can be found in the most barren locations.
This is true of the natural community our botanists recently found on an ancient limestone glacial plain. The bedrock exists just inches beneath the soils’ surface, and is completely exposed in other areas. Yet, this landscape supports a vast plant community thriving in these mere inches of organic matter. It begs the question: “where did the soil come from, anyway”? Landscapes like these offer a unique opportunity to witness, at each stage, how soils form on glacial plains. One can see plainly how the grooves formed by ancient glacial erratics have allowed for pioneer moss growth, giving way to grasses and eventually forests thriving on nothing but a slab of rock.
First Signs of Life
In this case, the limestone bedrock was first shaped by a glacier grating across the rock, forcing it into a smooth, flat plain. Small grooves and cracks formed as the ice carved its way across, leaving sand and small impressions in its wake. Certainly, organic matter would be able to accumulate in those small grooves over a long period of time, but the process is accelerated on the base limestone material, as it is more susceptible to erosion from acid rain and freeze/thaw events. As cracks and cervices deepen, moisture can accumulate and eventually provide just the right conditions for moss and algae to grow. Thus, the first layer of organic matter develops.
The organic material build-up is a slow process—even on limestone—that further agitates and transforms the terrain. As mosses and algae grow in the moist cervices, they accumulate more moisture, succumb to decay, which in turn provides more opportunities for new mosses and algae to take hold. Over time, birds and insects are attracted to the vegetated areas and contribute further to organic matter build-up. Thick mats of decaying mosses and roots, naturally fertilized by passing birds, eventually give way to the first pioneer clumps of grass, or even a small shrub.
And with that, a boom occurs. Plant material grows, dies off as conditions change, decays, and supports the next plant community to grow faster and stronger than the last. Though it takes thousands of years, the limestone bedrock is eventually covered in nutrient-rich soils able to support entire forests. Of course, this landscape is not immune to natural events such as fires, floods, and freezes, which can halt or even alter this soil life cycle—as can human interventions like agriculture and pollution. These, as well as other micro-differences in conditions cause soils to develop at different rates at various locations—even on the same glacial plain. Being able to witness a sprawling landscape experiencing all stages of growth provides insight on exactly how this life cycle occurs, and exactly how soils form on glacial plains.