The prairie ecosystem is like a puzzle. When parts of the puzzle go missing, it is difficult to understand the complete picture. At Wind Cave, as many parts of this puzzle are preserved as is possible. As a result, this park is a refuge for prairie plants and animals, and a great place to see a remnant of the North American grasslands.
The prairie is divided into the eastern tall grass prairie, the central mixed grass prairie, and the western short grass prairie. Tall grass prairies receive 30 or more inches of rain per year, while short grass prairies receive about 12 inches of rain. Mixed grass prairie receives rainfall between these amounts. The species composition is determined by the climate, fire frequency, and the degree and frequency of grazing. The mixed grass prairie is an ecotone that results where species composition is constantly shifting between the tall and short grass prairies.
To understand life on the prairie, one needs to understand the climate extremes withstood by prairie dwellers. Yearly fluctuations in temperature of 140 degrees Fahrenheit are common. Some years may bring intense drought. Intense weather events such as hail, tornadoes and wildfires occur periodically.
With such an extreme environment, it is a wonder that anything can survive. But there is one type of organism that dominates the prairie—grass. Grass provides food and habitat for many species, and covers the prairie.
Grasses are able to maximize their growth and production, even in constantly changing environments. More than half of their mass is below the ground, in the form of roots. This helps build and hold soil and creates a food store that the plants use during winter or during droughts. Grasses have also adapted to pressure from grazing. Silica, a hard mineral found in soil, is incorporated into the plant’s cells. This makes the leaves coarse and less palatable to grazers. Also, the growing parts are at the base of the plant, so grazing animals do not kill the plant. When the photosynthesizing tissue is removed by grazing, the rate of photosynthesis within the uneaten tissue is increased.
In response to wide temperature fluctuations, grasses have evolved to cool- and warm-season species. Cool-season grasses, such as needle-and-thread grass, grow well in the spring and fall when the temperatures are cooler and more water is available. Warm-season grasses, such as blue grama, await the summer months. They grow best in high temperatures.
By winter, the surface portions of grasses have died and most of the plants' energy has been transferred to the root system. What remains is the dry carpet of grass that crunches underfoot. This dead material is an important source of food for the grazing animals throughout the winter.
Many of the animals on the prairie rely on the prairie grasses for survival. Large ungulates like bison, elk, deer, and pronghorn graze on the grasses and forbs that grow on the prairie. Smaller animals like the prairie dog also rely on the grass for survival. Predators of the prairie, like birds of prey, mountain lions, coyotes, and black footed ferrets prey on the herbivorous animals.
To us humans, fire is often seen as a threat. But fire can be constructive and is a natural part of the prairie environment. In fact, the survival of the prairie depends upon fire.
When fires are suppressed, tree saplings are able to sprout on the prairie. Over time, these saplings mature into larger trees, and forest takes over the prairie. Additionally, dead plants build up over the soil, acting like natural mulch and blocking new plants from growing.
Fires burn the layers of dead material from previous years. Fire also helps shape the grassland community by killing competing trees and shrubs, maintaining the balance between the forest and prairie. During a fire, most of the grass remains unharmed in the ground. After the fire, grasses benefit as more space, light and water become available for more growth.
The suppression of fires in the Black Hills, the area in which Wind Cave is located, has led to higher forest density. This has contributed to the decline in plant diversity, and also contributes to more intense fires when they do occur. Wind Cave National Park routinely conducts prescribed fires. These fires are closely monitored to ensure the health of the environment, but also ensures that human lives and property are protected.
Few ecosystems have seen the destruction endured by the prairie. Prior to European settlement, the prairie was a vast, unbroken stretch of plant and animal communities. With the advent of agriculture in the American west, the prairie became fragmented. Widespread animal and plant declines, and the introduction of invasive species, led to a sharp decline in biodiversity. One example of this is the decline and near extinction of the bison.
Many scientists estimate that there has been a 99% reduction in tallgrass prairie, and a 75% reduction in shortgrass prairie. Many native prairie plants and animals struggle to survive without the prairie. The first step to saving and rebuilding this ecosystem is to learn how to appreciate it. Wind Cave National Park is a great place to start.
Though this park was created to protect a cave system, its national park status was saved from an uncertain future by incorporating a game preserve on the park’s surface. Since 1912, the park’s dual mission was to ensure the survival and health of the prairie habitat which it occupies.
Today, it is one of the best places on the continent to experience the mixed-grass prairie. Bison are a common sight here, grazing and wallowing among prairie dog towns. From up high, one can view the mosaic of prairie grasses and wildflowers waving in the wind. One can close their eyes, listening to the wild sounds of the prairie, and imagine that nothing’s changed here for hundreds of years. Solitude is found amongst the wind rushing, birds chattering, bison bellowing, and insects clicking. Here, the pieces of the prairie puzzle are intact.
Last updated: July 3, 2020