After obtaining a PhD in Biology from Syracuse University in 2002, David moved to southeastern Colorado to study the National Grasslands with the US Forest Service. Today, he is a landscape ecologist with the USDA Agricultural Research Service studying cattle production issues in the shortgrass prairie. He has expertise in plant-herbivore interactions, the ecology and management of semi-arid rangelands, and conservation biology.
The following interview has been edited for clarity and length.
Steve Rosenzweig: Explain to me what you see when you’re walking through the shortgrass prairie.
David Augustine: So as we walk across the prairie here, what I'm looking at is the mixture of the cool season and the warm season grasses and what we have here is the state grass of Colorado. This is blue grama, the dominant plant of the short grass steppe, and you see this is intermixed with a community of cool season grasses that are what we might call the over story and a really diverse community of forbs. But this mixture of short grass, the warm season short grass and the cool season mid-grasses is really what I think of as the typical short grass steppe plant community.
SR: What roles do these warm season and cool season grasses play in the ecosystem?
DA: So I think it's the mixture of these grasses, these 2 types of grasses that really give the shortgrass what you might call its function. This blue grama is one of the most drought tolerant plant species in the plant community and the ability of blue grama to tolerate droughts of all kinds – from short-term droughts in the middle of the summer to multi-year droughts over an entire decade. This ecosystem’s ability to survive through those droughts and the ability to produce when they are little bits of rain are what I think gives it resilience and really makes it differ from dryland agriculture. And then just as important in terms of being able to survive droughts is the ability to respond when you have wet periods. We have this really nice layer of cool season mixed grasses over top of the blue grama understory, and so the ability of these grasses to respond when you get those wet pulses, when you get those deluges, that's what gives the system its productivity. So if it was just up to blue grama the system would not be very productive it would just be resilient to drought but when you have the blue grama mixed with the cool season community then you have both that ability to tolerate droughts and the ability to respond and be productive in the wet years.
SR: What do you think dryland producers can learn from this ecosystem?
DA: So I think the main issue that dryland agriculture in this region has to contend with is: how do you produce a crop with so little rainfall and also such unpredictable rainfall from year to year? And really that's what the species in this ecosystem have evolved to deal with. They have a whole suite of mechanisms for dealing with the fact that they can't predict what kind of precipitation they're going to get from year to year. First of all it's a perennial community here in the short grass steppe, and that native perennial community stores a huge amount of biomass below ground each year and that below ground storage is what enables it to persist through droughts and to persist with a lack of predictability. And that's the contrast with dryland agriculture where you don't have any storage belowground; we have to reseed in the source of propagules every year. Most of our agricultural systems are not based on perennials and that's a real challenge for agriculture. But the prairie is no-till, and it's perennial, and it's diverse. And like I said, the two components that are really important for diversity are 1) having this component that can really do well under extreme dry conditions, and 2) having a separate component, these cool season grasses, that can be productive under wet conditions. A single plant species can't do both of those things. You have to have more than one plant species to be able to respond to both of those conditions. So I think that's a big lesson for agriculture out here.
SR: What role did bison play in this ecosystem?
DA: In this ecosystem, we have a whole suite of different strategies for dealing with herbivory. And that diverse suite of strategies is what's evolved with bison over the past 10,000 years. For instance, blue grama is the dominant plant and it contends with grazing by allocating a significant part of its productivity below ground every year. Every time it rains, blue grama is shunting a whole bunch of its photosynthate below ground. Its innate strategy is to constantly be doing that. You also have annual grasses out here. Here's a native annual grass, six weeks fescue. It's evolved to avoid grazing because its roots are so shallow that when a grazer bites a clump of that grass, most of the roots will pull up, and if the animal were to ingest that clump it's going to take a lot of soil into its rumen. They'll actually spit the grass out and stop grazing it because they take in too much soil. So that's a totally different strategy for avoiding herbivory. You've got cactus out here that's an important part of the plant community. Obviously that is avoiding herbivory by using spines, and it's able to photosynthesize under very dry conditions.
SR: What do you find interesting about the shortgrass prairie?
DA: Driving down the road, I feel like so many people, their only knowledge of the short grass is driving across I-70 going 75 to 80 mph and they just think it's this low diversity, homogenous expanse of never-ending grass. But if you stop and get out – and you really have to get out and be 1 foot tall and really look around – you realize how diverse and interesting it is. Even here in this conservation area, the Soapstone Prairie Natural Area, they have cattle grazing out here so it is producing food for all of us. And that's what's great about them. They can do both. They can conserve biodiversity and produce meat through ranching. It's just when you plow it and turn it upside down you lose that biodiversity.
SR: Can you find a plant for me that not many people know lives out here?
DA: This is a wild onion. If you dig this up there's a bulb down there and it smells like onion, tastes like onion. You could use it on your sandwich.
Steve Rosenzweig is a PhD Candidate at Colorado State University. This interview was conducted as part of a film project to document emerging innovations in dryland agriculture, which can be viewed here.