NEBRASKAland Magazine is dedicated to outstanding photography and informative writing with an engaging mix of articles and photos highlighting Nebraska’s outdoor activities, parklands, wildlife, history and people.
Issue link: http://mag.outdoornebraska.gov/i/683373
JUNE 2016 • NEBRASKAland 59 The Foundations of Resilience In the engineering world, resilience is the ability of something to bend or squish under pressure but then bounce back exactly to its prior state. In the natural world, resilience is a little different. A resilient prairie is like a ball in a bowl. Events like droughts, grazing or mowing might push the ball around the bowl, but as long as it remains in the bowl, it is still a prairie. As it moves around that metaphorical bowl, a prairie can look very different from year to year – vegetation might be short-cropped in some years, tall and dense in others, or full of "weedy" opportunistic plants in others. The key to resilience is that the prairie maintains its community of species and those species continue to perform their roles in the ecological system, regardless of what happens to the prairie or how it looks as it responds. There are two major factors that make grasslands resilient. The first is size, the second is species diversity, and the two are strongly interconnected. Large grasslands can support big populations of species, and lots of them. Big populations are resilient because it's unlikely that every individual in a population of pocket mice, sharp-tailed grouse or digger bees will be wiped out in a drought, disease outbreak or fire. Some individuals will probably survive and rebuild the population. Even if a population does get knocked out by a severe event, a large grassland will have numerous other populations that can send colonizers in to start a new population where the old one previously was. Large grasslands also provide lots of habitat types. Soils and topography combine to create a broad array of growing conditions for plants, creating various plant communities that each support characteristic species of invertebrates and wildlife. Clearly, larger grasslands will have more combinations of soils and topography than will smaller grasslands, and so will have more habitat types. Not only does that variety support lots of different animal and plant species, it also gives them alternatives as weather and climate change. For example, during periods of dry, hot weather, species that normally enjoy sunny south-facing slopes might seek out cooler moisture north-facing slopes instead. If those hot dry conditions persist for many years, even plants can move (over multiple generations) to find more appropriate habitat. In addition to soil and topography combinations, habitats are also defined by factors such as fire and grazing, which alter the structure of the vegetation. Every wildlife species has its own set of habitat structure requirements, so more variety in patches of habitat structure supports more wildlife species. Most habitat structure today is controlled by land managers who employ strategies such as haying, grazing and prescribed fire. Small prairies are likely to contain only a few management units (a pasture or two and maybe a hay meadow), meaning that there are few options for habitat patch types. A large grassland landscape, however, will have a much wider variety of those patch types, giving wildlife species a good chance to travel around and find what they need. The second major factor that defines grassland resilience is species diversity. Healthy prairies have an incredible diversity of animals, invertebrates, plants and even soil microbes. That diversity allows that prairie to function as a community through just about any weather, fire or grazing event. In human communities, we each play different roles Droughts are likely to intensify in coming years, making ecological resilience in prairies even more important. While some species do poorly in droughts, others are able to thrive.