Friday, June 10, 2011

The Goodness of Legumes

On the Great Plains, the land of open vistas and widely spaced little towns, it's difficult to find native vegetation mixed in with all the smooth brome. I returned today from a week in Sand Hills country--I went looking for native prairie, not reconstructed, not recreated from who-knows-what in the seed mix, but native prairie. I found one, a tiny little tract of land owned by an Audubon chapter, but it's been hayed so much that diversity is extremely low. Among the native plants I found were a lovely penstemon (pale blue, tall, unpalatable to cows), Western wallflower (also known from the Western Ozarks on a glade by the same name), one single Lithospermum incisum (also known from few high quality glades in the Ozarks) and not a single legume.

Driving back along I-70 past the suffocating overstocked dense woodlands this morning, I already missed the long views and dramatic skies of the Sand Hills. But I didn't miss the truly depressing and depauperate prairies that have been irreversibly damaged by overgrazing by domestic livestock. It is irrelevant to compare Missouri's high quality native prairies to the Great Plains, and I remain stalwartly opposed to the concept and practice of introducing domestic livestock to any native landscapes in the state. The damage is done out west, the prairies of the Sand Hills are clearly not "resilient and ever-changing," and neither are our prairies and native ecosystems in Missouri. If prairies were indeed so resilient and ever-changing (and able to withstand cows for extended periods over the course of 100 years), we would likely have more native prairie in Missouri and throughout the Great Plains. Prairies remain the most endangered ecosystem in North America largely due to our wanton abuse by grazing cattle to grow protein.

Nice vistas on the Great Plains, no diversity except on the one or two stretches of rural roadside that hasn't been treated with 2-4D and cows, and even there you had to comb through the exotic cool season grasses.

It's neither here nor there regarding the Ozarks, a discussion on the Great Plains and native prairies in Missouri (until I write about Tingler Prairie Natural Area around Licking, the last high quality prairie in the Missouri Ozarks), but I was struck by the complete absence of native legumes in the Great Plains. So my thoughts turned to the site I was birding in last week where I was surrounded by at least 20 species of legumes.


If you burn a tract of woodlands in the Ozarks that has not seen fire in many years, and that tract of woodland isn't chocked full of buckbrush pre-fire (grazing increaser), a good sign of recoverability is the immediate appearance of a host of legumes. Desmodiums, native lespedezas, Psoralea (pictured)... if these show up in high numbers the first spring after a fire, there's a good chance that the woods weren't damaged beyond repair by overgrazing. As restoration continues, the rest of the suite of quality native forbs should appear, namely the asters and goldenrods. But if the fire program has continued for many years and legumes, asters and goldenrods aren't showing up in high numbers, there may be little hope for true restoration. Cows love native forbs, especially the highly nutritious legumes. Just ask any range manager in the Great Plains if they have the rich suite of native legumes, goldenrods and asters on their prairies.

Cows aren't the only culprits in the degradation of native ecosystems in the Ozarks. White tailed deer are responsible for turning decent enough woodlands into veritable monocultures of Desmodium nudiflorum in some parts of the region. The nutritional value of tasty legumes is high, and some (now the more conservative ones) are more palatable than others. D. glutinosum is another legume that deer don't seem to prefer, however.

Nevertheless, quality legumes and other forbs remain good indicators of ecosystem health. Without them, ground feeding animals like bobwhite quail wouldn't have nutritious seeds to forage. Unfortunately, in overgrazed landscapes, the legumes are usually the first plants to disappear. I didn't see a single one in an entire week on the Great Plains. I can't wait to return to my birding site next week.

10 comments:

Mike Whittemore said...

I can see why legumes are such a valuable indicator of strong ecosystems because of their relationship with nitrogen fixing bacteria. I'm sure many high quality plants depend on them.

While in ND, I've definitely noticed a stronger presence of legumes such as leadplant, oxytropis spp. and a high abundance of astragalus spp. throughout the unbroken sod. I also see western wallflower and narrow-leaved stoneseed in high numbers. Though, smooth brome has really done a number here as well.

Harry said...

Allison,
Before cattle, there were at times millions of bison, elk and antelope grazing the prairies. Can you discuss their preferences for legumes and grasses?

Allison Vaughn said...

Bison, antelope, elk never stayed in one place for successive seasons and years like cattle. This is the imminent problem with trying to emulate natural disturbance factors of grazing on modern day prairie tracts--even at the site I work with, a 5,000+ acre tract, is too small to emulate historic grazing patterns. Grazing with domestic livestock wouldn't be so detrimental if managers allowed their cows on a prairie for two weeks then took them off. But no permittee will agree to such a short time of grazing. Bison and other native grazers would graze one section and then not come back for years. With our highly altered systems and lack of contiguous landscapes, mimicking natural grazing behavior is impossible. Even the father of patch burn grazing says that the practice doesn't work on tracts as large as 23,000 acres--the lands need to be bigger. Cows and bison have some of the same behaviours, with both of them preferring certain suites of forbs, neglecting woody species, etc., but the way cows are being managed and have been since the Civil War is inherently destructive.

Paul Nelson said...

I strongly agree with Allison. She nailed it on the bison and elk preference for legumes. Sadly I'm not sure we can continue to manage small isolated prairies trying to emulate historic patterns with bison or cattle. Just simply too small, especially when managing agencies like MDC is more defensive about managing with cattle with their primary driver being appeasement of ranchers and managing for bird diversity; not biodiversity. I've never heard any MDC manager claim that their primary objective is to preserve biodiversity thus they want to graze with cattle to assure that happens. Instead we are left with fields of weedy increaser plant species, exotics and decreasing sensitive plants. Worse yet most managers do not know the difference but assume that if grazing occurred historically then heavy grazing must be good. Oh and I guess prairies are ever changing and resilent IF you want fields of smooth brome, fescue and generalist prairie plants. Its easy to plant generalist prairie species but you cannot replicate the assemblage of ancient complex associated conservative prairie plants once destroyed. If Missouri prairies are concluded to be resilient and ever changing then why is 99.5% of it destroyed?

Harry said...

What factors limited the bison population over thousands of years if forage was so plentiful? I'm not arguing, just uninformed. I realize that bison have long gestations and small litters.

Allison Vaughn said...

Predators. Today, predators are few and far between. Predators are also responsible for movement. I recall Yellowstone since the reintroduction of wolves, and now the elk are not so prone to hang out in the bottoms eating the aspens to a nubbins. Now that the riparian zones are built up again, the beavers are back and wetlands are returning to the landscape. Many in the field think that fire was the only factor in the movement of large herbivore herds, but predators and weather conditions also impacted movement. The prairie at Custer and Wind Cave are being irreparably damaged by overgrazing in the absence of predators. In fact, if you actually SEE a mountain lion, you're to report it because they're so uncommon there.

Chris said...

I'm curious to know more about where you were looking at Sand Hills Prairie. Were you in the Nebraska Sandhills?

Allison Vaughn said...

Yes, in the Nebraska Sand Hills. Love the vistas, but no large landscapes with any integrity left. I really enjoyed wine made with Vitis riparia, too.

Chris Helzer said...

Interesting. I'd be curious to know where you were. I know the sandhills prairies intimately and it's really rare to find one that has low numbers of legumes. Amorpha, Psoraleas (old name), Daleas, Astragalus, and Oxytropis are all very common genera in sandhills prairies - among others.

The sandhills are dunes that are ephemerally stabilized. When Charles Bessey (well-known botanist) was surveying the sandhills in the late 1800's he found very active dunes with superabundant populations of the blowout penstemon - now a federally listed endangered plant. Earlier explorers also emphasized the open blowing nature of the dunes. Recent relatively wet climate and careful grazing (to avoid creating blowouts) has stabilized the dunes - temporarily - quite a bit more. That's assuredly part of a long-term cycle of open and closed vegetation communities that has gone on for centuries.

Anyway, the point is, that I think it's awfully difficult to compare a prairie system like that to the productive and stable soil prairies of Missouri. They're just different. Both are good. Unfortunately, the most accessible public lands in the sandhills often have the least forby prairie because they are the least grazed. No grazing pushes those prairies to grass dominance pretty quickly.

Also, you mentioned Lithospermum incisum. That's a very common plant in the sandhills and much of Nebraska (along with L. caroliniense) and does very well under even repeated intense grazing. It's rarely abundant where grazing is absent.

I think it's great that prairies vary so much from place to place, and that plants that are considered rare or conservative some places are rampant in others. Diversity is good!

Allison Vaughn said...

I wish I had consulted you before my trip to Nebraska. I sought out prairies, mostly TNC sites that upon visiting I learned were "reconstructed" prairies, which are not real prairie, but planted grasslands. I agree that the sand hills cannot be compared to our prairies of southwest Missouri, but we also have loess hill prairie in Missouri and Iowa and have an ancient association of native high quality forbs associated with them. Cattle and bison cherry pick native forbs, and while I understand the importance of grazing as a disturbance factor, when done improperly like it has been throughout the Great Plains and now in Missouri, the conservative species drop out, leaving behind forbs, yes, but not the conservative ones. Neither cows nor deer like Tephrosia or Astralagus, and nor do they like the woodies like lead plant (and, coincidentally, sumac, which spreads like a plague across overgrazed land in the Midwest). I certainly appreciate your knowledge and understanding of prairies of the Great Plains, and I would never consider myself an expert on such systems. However, I think that before the age of extraction began with European settlement, these ancient systems were mantled in species richness, and not just grazing increasers like the Brassicas and a handful of forbs. I recall a range expert pointing to a ragweed, and saying to me, "see, cows are great for forbs." We wouldn't have so many extirpated and conservative plants today if we hadn't raped the land by open range and confined grazing. A species list of 20 natives and a bunch of exotic cool season grasses on the sand hills surely doesn't represent its historic character. I don't doubt that blowouts like we have on certain sand prairies did not have a species list of 400 native forbs on a 200 ac. tract like we have in southwest Missouri, but surely historically it was richer than what I saw in a week in Nebraska. I'll add, however, that I am not an expert in the sand hills ecology as you are, and I respect that a lot. I'm glad there are those who understand these systems on an intimate level, and hopefully strive to protect what integrity remains after so many years of abuse.