Introduction

This little guide to native grassland within the United States and Canada attempts to explain in simple terms what prairie is, how best to enjoy it and how not to get lost trying to find it.

Prairie is usually thought of as a vast North American warm season grassland (and precursor to an extraordinarily rich farm belt) centered in the Great Plains and extending into the upper Midwest. There are many further categorizations of prairie based upon soil, precipitation or flora but I like the simple Chicago all inclusive definition best. In Chicago ‘prairie’ is often used to refer to a weedy vacant lot - as in ‘Why don’t you kids go out and play in the prairie for awhile?’ This popular definition is actually not too far off the mark as some of the earliest prairie restorations did indeed start out disguised as weedy vacant lots in failed Cook County housing projects.

For the purposes of this guide and its tables a prairie is native North American grassland with a distinct dormant season and usually dominated by one or more grasses from a small group of signature (and usually warm season) perennial species. This includes most native grassland but not some closely related seasonal wetlands. I have also included some barrens, glades, alvars and savannas if they include a notable proportion of prairie plants. These areas often support small patches of grassland plants in regions where the climate in the last few thousand years has shifted away from supporting more extensive grassland.

John Weaver and Frederic Clements in their classic work Plant Ecology used the qualified term prairie for a wide variety of grasslands beyond the boundaries of the Great Plains and Midwest. Before their collaboration Weaver had completed extensive field studies in the Palouse Prairie of the Pacific Northwest while Clements had studied the Mojave Desert’s grasslands. They divided the grasslands of the continental United States into eight major divisions with climate the principal determining difference but emphasized that these divisions had often overlapped in the past. Just as there once was a rich tallgrass ‘prairie peninsula’ that extended across northern Illinois and Indiana into western Ohio there was also in the not too distant past a similar peninsula of surprisingly lush high desert grassland across New Mexico and Arizona into the Central Valley of California. Since their pioneering work further outlier prairie parcels have been identified as far east as central Pennsylvania, Ontario, New York’s Long Island and the Piedmont region of the Carolinas. In the south the cotton and rice belts before they were settled had almost as much tallgrass prairie (or its closely related coastal analogue) as the Midwest.

To expand the definition of prairie a bit lets talk about the four broad categories of prairie that Weaver and Clements identified in the general region of the Great Plains and the Midwest. The tallgrass and shortgrass prairies are just that – prairies that are dominated by grasses that are either very tall or very short respectively. The mixed grass prairie is in between the zone of tallgrass prairie in the east and shortgrass prairie in the west and usually designates a broad area dominated by mid grasses with an understory of short grass. There are many subcategories in the mixed grass prairie and often short, medium and tall grasses intermingle in somewhat distinct areas. For example in the dry climate of the Great Plains it is not unusual to see a narrow ribbon of tallgrass along with some bur oaks or cottonwood trees along the many seasonal creeks that progresses into shorter grass the farther up slope away from the moisture one goes. This is still collectively a zone of mixed grass prairie. Finally, the term ‘true prairie’ is sometimes used to describe grassland that can be thought of as the final stable form of prairie in regions of moderate precipitation and occasional severe drought. The two grasses that Weaver and Clements considered characteristic of the true prairie – Porcupine Grass (Hesperostipa spartea) and Tall Dropseed (Sporobolus compositus) – can readily withstand drought and desiccating winds but compared to other prairie grasses are more sensitive to grazing pressure or early season fire. True prairie unlike mixed grass prairie usually does not have a broad understory of short grass and it often has brilliant displays of summer wildflowers which do not suffer from the severe over shading that a dense tallgrass prairie can have. The crucial difference between the true and tallgrass prairies is that the latter is a subdominant ecosystem that without continual disturbance – usually in the form of fire – eventually becomes either a deciduous forest or a true prairie (to simplify Weaver and Clements). These types of prairies are all abstractions to some extent and in reality blend together at the edges in dynamic zones of transition and often tension referred to as ‘ecotones’.

One further point with some controversy surrounding it concerns the relative stability of the shortgrass prairie. That the tallgrass prairie is a subdominant ecosystem does not seem to be very controversial – most will agree that this is a zone where the climate now favors deciduous forest and the prairie hangs on through periodic disturbance. Weaver and Clements also considered the shortgrass prairie of the western Great Plains to be subdominant – a position which has been subsequently challenged.

Here is the background to the controversy. It might seem logical that in the rain shadow of the Rocky Mountains that short drought tolerant native grasses would represent a sort of stable endpoint, but actually this is not really true. Many of the taller grasses of the mixed grass prairie are reasonably drought tolerant as well and once established during a few relatively wet years their overshadowing traits begin to trump their shorter neighbors’ advantage during drought. If a drought does occur many of the mid-grasses can go dormant for long stretches of time. The equilibrium changes when one looks beyond the plant life. All of those large groups of mammals of the shortgrass prairie kept the balance in favor of the shorter grasses by continually eating, trampling or clipping the taller grasses that would otherwise cause a shortgrass prairie to eventually become a mixed grass prairie. Weaver and Clements during the grim dustbowl era conducted experiments on carefully controlled plots of land and concluded that shortgrass prairie was in most cases an overgrazing indicator. In their view plants are the dominants of any ecosystem and overgrazing a disturbance that rolls back the sequence of natural plant succession – hence the shortgrass prairie is a ‘short-grass subclimax’. Animals can not be considered dominants in an ecosystem because they do not exert a ‘controlling reaction upon their habitat’ (p421, Plant Ecology 1929). Today I would hazard a guess that most biologists and habitat managers would consider the animals of an ecosystem as integral as the plants in determining that ecosystem’s overall stability. I plead agnosticism and will not discuss here a corollary controversy concerning a gregarious little rodent that helps to keep the shortgrass prairie short – namely the black-tailed prairie dog.

Perhaps the visitor to this website has heard that prairie is a very rare ecosystem and may be curious as to exactly how many parcels of prairie there might be. An indirect answer is less than there should be but more than you might imagine – at least a thousand. There are now well over a thousand plots of land managed at least partially as native grassland in the United States and Canada. More than half - and much more than that in terms of total acreage - came into legal existence after 1990. The majority have at least some minimal type of public access though sometimes that may not be more than an annual workday or very rare guided tour. Generally prairie that was set aside originally as public hunting land can be accessed with the fewest restrictions while private land under conservation easement often has no access at all. The actual number of prairie parcels is a growing but inexact number. Several state departments of transportation have been actively restoring prairie along highways, rest stops and railroad right-of-ways – many of these efforts are significant but lack names. Also, unbeknownst to the general public, the US Fish and Wildlife Service in an often complex set of agreements with various private organizations has purchased tens of thousands of acres of conservation easements in the prairie pothole region of the northern great plains. These lands mostly can not be visited by the general public but often surround and enhance existing sanctuaries. Finally there has been an amazing number of local projects – particularly by schools and park departments in the towns and cities of the Midwest – to reestablish prairie and savanna. This year has been the first when all efforts to preserve or reestablish prairie have shown up in sufficient numbers on the internet to fill a table with over a thousand external links in it.

If you live in the middle third of the United States or Canada the odds are very good that you live near a prairie parcel that you can readily visit. Even if you live in the other two thirds the odds are reasonably good – there are many parcels of native grassland outside of the Midwest and the Great Plains. These plots of land can usually be visited and something of interest discovered year round.

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