AoR 51: Matt Germino, Nitrogen and Carbon Cycling on Rangelands

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>> Welcome to The Art of Range, a podcast focused on rangelands and the people who manage them. I'm your host Tip Hudson, Range and Livestock Specialist with Washington State University Extension. The goal of this podcast is education and conservation through conversation. Find us online at artofrange.com. My guest today on The Art of Range is Matt Germino. He's a Rangeland Scientist with the US Geological Survey in Idaho, who's been on the show before. Matt, welcome back.

>> Thanks, Tip. It's great to be here.

>> I want to talk with you about what I think is a little understood topic in rangeland science, especially on the grazing side of range science, and maybe I'm just trying to shore up my own ignorance here. I suppose they do say that all research is me search. But if that's the case, we'll take a few people along for the ride. In most agricultural plant communities, yield is an indicator of success. Like in tree fruit, tree fruit people say that, that fruit volume is a good indicator of plant health. And in crops, including even dryland cropping in the West, higher yield, at least to the point where the marginal cost of increasing production a little bit more is more than offset by the increase in revenue, that's usually considered economically beneficial. And an irrigated pasture, more forage for more of the year, is generally better than it's commonly recommended to apply some kind of fertilizer whether that's manure or synthetic fertilizer. And further, the economic benefits of increasing yield often justify the intensive agricultural inputs, like fertilizer and herbicide that are necessary to achieve the increased yield. But, but this is a point, I feel where rangeland livestock production departs significantly from tame pasture livestock production. You know, in cultivated or planted or tame pasture, what we're building is an agronomic system dedicated to producing pounds of forage, and in rangeland grazing, I guess I'm resisting calling rangeland areas pastures because I think the term pasture connotes a single purpose for the land. Even though I realize that in range, we use the term pasture sometimes to refer to individual management units that are enclosed by fence on landscape. But in rangeland grazing, the goal is, or I think ought to be maintaining a natural plant community that provides a broad suite of ecological goods and services. So if that's the case, maximizing production of one component of that ecosystem, you know, for example, grasses preferred by livestock, may not be the best option ecologically or economically. But I'm not quite confident enough of that to outright discourage soil nutrient supplementation. Maybe you can change my mind. Well, here's, here's a story maybe to launch this line of questioning. It has been one of my beliefs that rangelands are limited both by nutrients and water and almost as much by nutrients as by water. So that speeding up nutrient cycling a little bit, such as you know, by adding legumes, or increasing the abundance of legumes in a grass-dominated plant community would increase total plant yield. And I mean, all the plants together, even with no change in precipitation for a given site, and of course, increased precipitation makes a difference. So here's the story. I had a silviculture class as part of my master's program with a professor at the University of Idaho who was working with a private timber company to develop a model that would predict under what forest stand conditions fertilizing a stand of trees would pay off. And the concern specifically on the sites that we visited was that these were, you know, drier conifer types on poor soils. This was decomposed granite soils in a 20-inch rainfall zone that had been harvested 20 or 30 years ago, and the trees were not growing very well. They had small tree rings. One of the things they'd already found in research here was that the practice of piling slash and burning it was removing much of the nutrients from the system since most of the nutrients were in the trees rather than in the soil. So this professor had a variety of light fertilizer treatments, a variety of mixes of macros and micros, that they had applied in a six-foot diameter ring around a bunch of trees at various sites. And we cored some of the trees and we could see the difference in the last two or three years under that fertilization, but what was most noticeable was the grass height inside the circle around the tree. The grass was approximately double the height of the grass outside the circle. Same precipitation, just a little bit of nutrients, and we're talking like five or ten pounds of nitrogen. So I'm, I'm interested in picking your brain about the role of nitrogen in rangeland plant communities. And whether there's benefit to adding nitrogen, whether that's, you know, more natural forms of nitrogen like in increasing the amount of legumes that are in the plant community, not spraying them out, various forms of nitrogen. So everyone knows that adding nitrogen to the soil makes plants grow bigger and sometimes healthier. Rangelands are limited by water, but also by nutrients. So what are your thoughts on nutrients being limited in rangeland communities, and whether that's a problem?

>> Well, there's a number of different ways to look at this problem. If you add fertilizers to just about any ecosystem type, generally speaking, you should see some sort of enhancement of productivity. In a grassland, that might be taller grasses with a greater percent cover of ground area and more biomass production. That response though, is not evenly observed at high and low levels of background soil fertility. So we expect the response to be more hump-shaped, if you will. Adding a little bit of fertilizer will generally stimulate an increase in productivity of the whole entire plant community. But then adding increasing amounts, eventually you'll reach a peak of the effect, and thereafter adding more fertilizer, especially nitrogen, you might actually begin to observe decreases in productivity. So that's the first tenet is that, that there's probably like an optimum level of fertility. And so that's concept number one. Concept number two, I think it's useful to think about what plant physiology teaches us about the effects of limiting resources. And one, one tenet is that plants generally do not operate in a way that causes them to be limited more by one particular factor than all others. That's a highly inefficient way of operating. Instead, plants alter their growth pattern such that they're co-limited by a suite of factors which are collectively limiting plant growth. So for example, plants will shift their allocation of growth to roots or to shoots to leaves. And then within leaves, they'll make adjustments so that the overall functioning of the plant is co-limited, by water, nutrients, several types of nutrients, and light. And what this means is that you can, you can add water, and sometimes you can add light in many rangelands. And generally you can add nitrogen or phosphorus and expect to see a stimulation of growth to a point, as I mentioned before with that hump-shaped concept. So I don't think the question is so much can we add fertilizer and get more yield? I think the answer is yes to an extent. However, does that really achieve the greater ecosystem, does that actually achieve greater ecosystem services to us and particularly the livestock industry? That's the real question. And I really liked how you began this discussion by talking about the differences between actively and intensively managed pastures, versus rangelands that are more semi natural and more passively managed. I think that's a really key distinction. For passively managed, semi natural rangelands, we have to think about the, the maintenance and the stability of those landscapes. We can't be, you know, plowing and intensely managing the soils and vegetation on these passive, semi natural rangelands. And if we're not careful, we can, you know, experience very negative, like liabilities that can occur on those landscapes if those landscapes become destabilized. And the classic example of that, for rangelands in the western United States, is the annual grass fire cycle, which has occurred throughout many rangelands and is in itself one of the biggest impacts to productivity of forage and many other ecosystem services. And so, from my perspective, we really need to think about the balance of productivity of the plant species that are most desirable for forage. And that's generally [inaudible] bunch grasses as it relates to the factors which affect the overall functioning and stability of the landscape. When the landscape, you know, begins to burn at excessively high fire return intervals, or when exotic and noxious species begin to invade, the value of those landscapes for rangeland activities, it decreases immensely. So then the next question is, well, how do nitrogen and phosphorus and other nutrients affect annual grasses versus perennial, desirable perennial bunch of grasses? And herein lies the problem. Many of these exotic species are a lot more apt to capture nitrogen or other nutrients in soils than are desirable, slower growing perennial species.

>> I've heard--I'm not an agronomist, but I've heard agronomists use the term referring to certain kinds of plants that they're luxury consumers of nitrogen. In other words, there's not a top to the response curve. I suppose you'd eventually find it but you know, there are some plants that can take 200, 300, 400 pounds of nitrogen and continue responding to that in a way that you know, blows everything else out of the water. It sounds like cheatgrass may be one of those, at least to a limit that's significantly higher than most of the perennial grasses.

>> That could be true, I'm trying to think of a study which actually looks at very high rates of nitrogen addition and how that affects cheatgrass versus other species. I think the real problem is more that when extra nitrogen becomes available in the ecosystem, cheatgrass is more likely to snap it up, and then grab it than many perennial species. In fact, we think that one of the mechanisms by which cheatgrass and other exotic annuals affect the ecosystem is by altering the natural cycling of nutrients like nitrogen in ways that effectively accelerate the cycling and make the nitrogen a little bit more available for rapid uptake, especially like in the early spring, and cheatgrass maybe selectively, it might be more poised to take up that nitrogen compared to perennial bunch grasses. In fact, several studies seem to suggest that.

>> One of the things that I'm interested in is what is the qualitative difference in different kinds of nitrogen and how it would ordinarily move through, say, a rangeland ecosystem.? And I'm aware that in a lot, a lot of rangelands where people have been concerned about some of the more common nitrogen fixing forbs, they have been removed sometimes by herbicide and sometimes take a while to come back if they're not planted back. How is how is the nitrogen that's provided by those nitrogen fixing plants, different than say, you know, just straight nitrate that could be applied in fertilizer, because there are some people that fertilize rangeland. And I guess I'm thinking of situations that feel to me like a crossover between tame pasture and rangeland where you've got, you know, say, a seeded dry land pasture that doesn't receive a lot of precipitation, but people do fertilize them. What's the qualitative difference between you know, just putting synthetic fertilizer on that versus trying to get something in the mix, that's more of a long term supplier of nitrogen that's in a natural form, whatever that natural form might be?

>> So, the main ways that nitrogen exists in our landscape are firstly in the gaseous form as dinitrogen and air, so air is 80% nitrogen, the molecular composition of air is 80% nitrogen. Plants, including biocrusts, can some plants and in some biocrusts, I should say, can take that, that dinitrogen which is two nitrogen molecules very tightly bound together and some plants can reduce that nitrogen and turn it into ammonia and then eventually possibly nitrates. And when they do that, that nitrogen is considered organic nitrogen. It's bound within the you know, the, you know, the protein and the other macromolecules of the plant. That nitrogen becomes most available to the ecosystem when the plant either sheds tissues or exudes compounds into the soil or dies and begins to decompose. And then that nitrogen in soil is in a, you know, is in an organic structure and they become available to some other plants via microbial symbiosis such as mycorrhizal fungi. But the general nitrogen cycle and probably the, the greatest amount of nitrogen transfer occurs when microbes decompose the organic matter and liberate that organic nitrogen back into ammonia and nitrate forms. And in many rangeland ecosystems in the western US, that oftentimes occurs in the spring where you have a flush of these inorganic nitrogen forms again ammonium and nitrate. And that flush of nitrogen oftentimes can occur in a very short time span. Species like cheatgrass can readily snap up that you know, that available inorganic nitrogen. Now, fertilizer is you know, the main forms of nitrogen in it are generally nitrates and ammonium ions. And so when you add fertilizer for the most part, what you're adding is these forms of nitrogen that are highly available for rapid uptake. Unless the fertilizer's been either structurally or chemically modified in ways that will slow down the release of the nitrogen and products like that are common for turfgrass management. For example, like some lawn fertilizers, maybe like the slow-release type made possible by binding the nitrogen in different ways. But for the most part, fertilizers generally contain nitrogen in a form that is quickly available for plant uptake compared to how most nitrogen is contained within a natural ecosystem, which is in organic forms. So that's a key distinction right there. So, legumes, plants in the pea family, have special nodules in their roots, where a macromolecule known as leghemoglobin exists, and those little nodules and this biochemical are able to again take that nitrogen from air and reduce it into these inorganic nitrogen forms, which are then folded into the organic structure of the plant, producing a more slowly available or producing a type of nitrogen which is more stable in the plant and also more concentrated in the ecosystem because the plants that are nitrogen fixers are effectively becoming little hotspots for nitrogen.

>> One of the known, I guess, ecosystem-level problems with invasive annual grasses like cheatgrass is that they can accelerate this nitrogen cycling, and you mentioned that just a few minutes ago, can shift the nitrogen into the mineralized form and affects, it affects significantly, what's going on in the soil carbon pool. Can you talk a little bit more about that?

>> Yes, so soil carbon and nitrogen are very tightly related in especially in rangeland ecosystems. And, you know, it's useful to think about how nitrogen enters these ecosystems, which is generally through the fixing of atmospheric nitrogen. By the way, the air around plants is 80% nitrogen, so there's a lot of it there in the molecular composition of air, but it's through plants like legumes and some microbial crusts, that the nitrogen enters and is reduced from gaseous nitrogen into ammonium or nitrate forms, which then are quickly used to form organic nitrogen. And then that organic nitrogen is a fairly stable way that nitrogen exists in an ecosystem. When the plant sheds its leaves or dies or senesces. that organic nitrogen then is subject to decomposition. And eventually the microbes will liberate that organic nitrogen into, back into ammonium or nitrate forms, which can be taken up by plants. And annual grasses like cheatgrass are what are known to accelerate the nitrogen cycling in ways that make the production of ammonia and nitrate in soils a little flashier. There's several studies that have taken resolute measurements of soil temperature and soil water availability at very fine temporal resolutions over the course of a year. And so for example, with cheatgrass, we can see that in springtime, when snow's melting, when it's still a little cool out and having freezing nights, sites where cheatgrass have come to dominate have a much flashier increase in these inorganic nitrogen forms. And what that's telling us is that the, the annual grasses are stimulating the nitrogen cycle in ways that cause greater flushes of these inorganic nutrients which then interestingly, the grasses themselves, these exotic grasses are more apt to take up that available nitrogen than the slower growing perennial bunch grasses. So the annual grasses are effectively [inaudible] the nitrogen cycle to their selective advantage.

>> Which increases their vigor and reproductive success, and then dominance in the local ecosystem.

>> That's right. Another interesting factor here is that many perennial species rely on, at least partly rely on microbial symbiosis such as mycorrhizae has ways to tap into organic nitrogen forms. You might have like decaying leaves or perhaps an insect, where nitrogen is bound in organic, into organic forms like proteins. In the normal nitrogen cycle, plants must wait for the microbes to liberate the nitrogen. But fungi, which are by design good at decomposition, can obviously get their nitrogen directly from the organic forms. And if those fungi are part of mycorrhizal networks, and are attached to roots, then the native perennial species who have the mycorrhizae can benefit from organic nitrogen. Now when cheatgrass comes to dominate a site, several studies show that the beneficial mycorrhizal fungi become depleted. And we think that the depletion of these mycorrhizal fungi from sites is a factor that inhibits the restoration potential of some sites.

>> And is that the chicken or the egg? Is that resulting because of the presence of cheatgrass? Or is it a leading thing that causes the increase in cheatgrass?

>> Well, you hit on another challenge in this overall topic which is making inferences about cause and effect. I will say in this case, there are some studies which manipulated the abundance of cheatgrass and observed the outcome on mycorrhizal fungi. And so we know that dominance by exotic annual grasses does lead to a depletion of the beneficial microbes in soil in terms of the nitrogen cycle.

>> So it's possible that the finding, finding ways to decrease the amount of cheatgrass in the system would begin to cause that to spiral back up in a sort of a positive feedback loop possibly?

>> Correct.

>> Is that too much speculation?

>> Well, no, no, I think that's, that is a very tenable hypothesis. We should expect to see, you know, the pattern you just described, provided that as the annual grasses become less abundant on the landscape, that there's an increase in the desirable perennials, and over time, who knows how long it takes, but over time, you should start to see the beneficial mycorrhizae coming back into the soils.

>> Yeah, one of the things that I'm wondering here is whether there are certain perennial grass species that are more effective than others at helping to facilitate that, that shift. I want to say I saw some research out of Idaho a number of years ago about blue bunch wheat grass, and I believe bottlebrush squirrel tail as being two grass species that were more effective, one at reoccupying, a site that had been infested with cheatgrass, and then resisting the reinvasion of cheatgrass once they had been established. Does that ring any bell?

>> Yes, there's several studies that show that the key features of those two species are that they are number one, that they can be locally abundant, but they can co-dominate many sites, many different types of ecological sites. So that's an important thing for considering how they contribute to site resistance to annual grasses. But their growth traits are also very important. Blue bunch wheat grass especially tends to green up relatively early in the year. It can also have a fall green up. And it's using soil water and nitrogen almost at the same time as exotic annual grasses such as cheatgrass And that overlap in what we call phenology, with a seasonal timing of growth is really critical.

>> There are two early birds that are both chasing the same March worm?

>> Correct. Yeah. You know, squirrel tail is shifted a little bit more towards the warmer season compared to blue bunch wheat grass. But nonetheless, these growth traits are really important. And they're, the abundance of the species and also the fact that you can get seeds for both the species have led to them be highly prioritized in rangeland seeding efforts.

>> I think you mentioned in a conversation when we were discussing some possibilities for this episode that the presence of cheatgrass can increase the amounts of secondary metabolites. Can you talk more about that? I wasn't sure if you meant in the invasive annual grasses or in the perennials.

>> There's a new study in Journal of Applied Ecology, which is a meta-analysis of how annual grasses affect the carbon cycle, which is an important thing to consider when we're trying to understand how nitrogen availability is affected by you know, grasses. And that study, like many others, compares how nutrients and site fertility on sites dominated by cheatgrass or other exotic annuals compares with intact sagebrush steppe systems. But the problem is that sagebrush steppe plant communities have always had a natural temporal pattern of increasing woody plant dominance with years to decades after disturbances such as fire, but right after fire, the sites are dominated by grasses in the natural condition. It would be perennial bunch grasses, as well as forbs and biocrusts. So it's really important when we think about how species like cheatgrass affect the nitrogen cycle, that we compare the effects of cheatgrass to the effects of too much wheat grass or squirrel tail and other perennial native bunch grasses and not focus solely on the comparison of cheatgrass-invaded sites to fully intact, late successional stage sagebrush steppe sites. That's a real complicating factor. There's many methodological issues in assessing how nitrogen affects annual grasses and conversely, how especially how annual grasses impact site fertility,

>> Right. I think you mentioned too that a lot of these even macronutrients are somewhat tied to each other you mentioned already that carbon and nitrogen cycling is tied. But carbon also affects phosphorus availability correct?

>> It does. Yeah, organic matter in particular. So the way that carbon exists in soils is a very important control on phosphorus.

>> And fire often leads to some depletion of soil organic matter?

>> Yes, especially where the organic matter and carbon are concentrated at the soil surface, which is generally typical of most rangeland sites. Combustion can remove that organic matter. And post-fire erosion such as wind erosion oftentimes depletes all of the surface soil organic matter, and therefore a lot of the carbon in the sites.

>> So there's another possible downward spiral. If you have a depletion of solar organic matter following fire, and then you have reduced infiltration of water or and or retention of water if soil organic matter is largely responsible for enabling the soil to hold more water, and if the number-one limiting factor in the plant community is water, then this is a big problem.

>> Absolutely. You're hitting the nail on the head here. We can't think of nitrogen or any particular nutrient by itself. The impacts of a particular nutrient are very tightly linked to the other nutrients. For nitrogen, that means carbon and phosphorous as well as by their micronutrients. And especially water. They're all interrelated. So a pretty typical pattern, after many large mega fires is you might have a site before the fire which has sagebrush and perennial bunch of grasses and maybe a little bit of cheatgrass, and some soil crusts. After many decades, the, these perennials have built up the, you know, the litter in the organic matter on the soil surface. And the nitrogen in the ecosystem, like the cycling is very tightly linked to the litter and the decomposition of that litter. After the fire, you've combusted away a lot of that organic matter. And the soil carbon begins to be a little bit more depleted on the soil surface. And if the site is subject to erosion, oftentimes we see especially on loam soil sites, that the soil surfaces begin to get hard and crusty after rain events, so in the days following a wetting event, when the soil surface begins to dry up, you get to, you get these circular physical crusts, where mineral crystallization processes create a very hard soil surface that does not accommodate seed very well. And similarly, like you mentioned, the soil surface becomes less permeable to any rains that might come especially during the early or late summer. So not only do seeds have a hard time dealing with this hard surface, but you're having less infiltration of water. And so here's an example of how the losses in site fertility, like for example, carbon, have an effect that really leads to something that looks like desertification, where for a given amount of rainfall, the expected productivity is not observed. Instead, you're having much less productivity because of this syndrome where problems with one limiting resource are compounded by the synchronized losses in the growth of related growth resources. It's kind of complex, but these feedbacks are critical for understanding how rangeland fertility works.

>> I think Hugh Baird was the one who first said that we, with regard to the hydrologic function, we need to be able to capture and store and safely release all of the water that lands on rangelands since they're water-limited ecosystems. How can we influence soil organic matter?

>> Well, it's hard to do when you're talking about pastures that might be a few thousand, sometimes 50 or 100,000 acres in size. You know, back to your point you made at the start of this discussion. There's very intensively and actively managed pastures out there. They tend to be pretty small. And then there's passively managed rangeland landscapes where there's a real limit to how much we can influence the soil and the plant composition actively. In other words, our main tool on rangeland landscapes is how we manage livestock, or how we manage disturbances such as fire and the recovery of landscape after fire. And so how can you manage soil carbon? Well, people tend to think of doing things like adding compost or manure. It's not really feasible to do over massive land areas. There are some efforts to, or that I should say that there's some research looking at adding carbon in very efficient form such as biochar, in other words, charcoal. Those are highly experimental. Again, I questioned whether or not we could apply them over massive areas. It might be more feasible on the scale of a few thousand acres at most. So what does that leave us with? Really, it's managing the disturbance regimes and the invasion. So it all goes back to what we might consider to be preventative medicine. Where you have a healthy, reasonably diverse plant community, we probably ought to think about preserving the condition of that plant community so that it has resistance to exotic plant invasion, especially exotic annual grasses and resilience to disturbance. Because once the fire happens, and exotic plant invasions increase, we get stuck in a cycle of feedbacks that appear to involve a loss in site fertility, which ultimately could impact the productivity of desirable rangeland perennial grasses. So I guess the short answer is the only way, probably the only way we can deal with managing soil organic carbon and site fertility on large rangeland areas is again by fostering healthy plant communities in a general sense, so that when fires or other disturbances roll through a landscape, landscape is able to rebound in ways that avoid a loss in soil site fertility.

>> Yeah, maintaining the natural processes that are responsible for creating sort of organic matter, and then protecting it. And it sounds like also a species composition that permits the survival of some of the soil microorganisms and fungi that are also responsible for, I guess, mediating nutrient availability to plants, and also hanging on to silica carbon.

>> Absolutely, unfortunately, one challenge that we have in rangeland ecosystems is that they aren't as well studied as other ecosystem types, especially more productive grasslands, like in the Midwest or forest ecosystems that have timber value, and therefore, have traditionally received more support for science and investigation. So unfortunately, in many rangeland landscapes that are semi-arid, we don't have as good an understanding about the diversity in those landscapes, especially below ground. So there's some, you know, some knowledge gaps out there that affect our ability to, to manage for particular species that might have stronger effects on soil microbial communities and nitrogen cycling. But we do know about legumes like you mentioned earlier in the call. We know that we also know that in some semi-arid rangelands, the presence of lupins and other nitrogen fixing species. You know, sometimes those nitrogen fixers actually can create hotspots of invasion, particular, particularly after a fire. So, we're still learning, you know, about all of this. It's a, it's difficult to make generalizations about whether or not we can actively manage soil and site fertility and delivery places, you know, actively.

>> Maybe one more rabbit trail and then we're probably going to run out of time, but there's been some effort to apply a human biosolids on rangelands, decomposed human waste. And, you know, societally, there's interest in figuring out things that we can do with that. But some people are pretty skeptical of whether it's a good idea to put that on, essentially, native or natural plant communities. And it does seem to me, you know, relative to our other conversations about different kinds of soil treatments, you can't do much soil amendment on a million acres, and so bio salts applications would likely always be kind of a small-scale effort. And but do you have any thoughts on whether that could be or would be or for sure would not be useful or beneficial on rangelands?

>> Well, you know, again, I think we have a problem with this, the practical scale issue of this. If it were shown to be beneficial, it probably is something that would apply to relatively small areas of rangeland. People have already been working with, with animal compost, animal-based composts like such as from chickens or cows themselves. What I would like to see though, is studies that don't just look at the response of the growth of desirable perennial bunch grasses directly to the fertilization, but how the whole plant community, including the exotics, as well as the native species are responding to the effect of fertilization through using these waste products. And I've not seen many studies that explore that net balance of the risk factors with the direct benefits. So that's really a critical thing. You know, I want to note that there, there have been some large-scale studies which provided uniform fertilization and uniform measurements to fertilization experiments around the world in grasslands, the most notable of which is called the nut net. And nut net is short for nutrient network. This includes 48 different sites around the world. One study in 2014, in the journal Nature by Hardier showed that the fertilization that these researchers did around the world and grasslands greatly affected the, the relationship of diversity to the stability of the landscapes in terms of how annual productivity varied from year to year, and normally, more diverse landscapes like more species diversity confers more stability, like reliable productivity from year to year. And what they found from these fertilization studies is that invariably, the fertilization diminished that enhancement of stability by diversity, in other words became dominated by fewer species. And that was a detriment to the landscape. And that's actually the real big picture here that we want people to consider when they consider using human bio waste products or manure or whatever, on rangelands.

>> There's a quote by Baxter Black that I've mentioned before, on the podcast. He liked to say that, "There's nothing that comes out of the end of a [inaudible] gun or a hypodermic needle that can compensate for subpar animal husbandry." And I'm reminded of that in thinking about applying human waste on rangelands. I suspect that in some places where that is considered, it's because the plant community seems like it's lacking, lacking in diversity yield, you know, general health. And Don Nelson, who was an extension beef specialist at WSU for a long time said, "You can't fix a problem without figuring out why you had the problem in the first place." And I'm struck by that same impulse here. I think it's probably important to look at especially in intensively managed rangeland pastures, to look at what the grazing management looks like before trying to, you know, shore that up or compensate in some way by trying to fertilize.

>> Absolutely. All too often we find when people are dealing with severe problems like, you know, grass invasions, and, you know, wildly changing fire regimes, it's, it's understandable that people would like to have silver-bullet solution to the problem. And many different silver bullets have been proposed. I think the last time we talked it was on the topic of weed suppressive bacteria, which people had high hopes for that, you know, we could just spray this bacteria on our landscapes and it would help us with our issues with annual grass invasion of perennial rangelands. And the evidence for it is not strong at all. And similarly, spreading fertilizers or biosolids on our rangelands. It is possible that it might be part of a strategy to correct our plant community conditions, but for sure, it's not going to be a silver bullet solution. In fact, there probably is no silver bullet solutions to such complex problems like our rangelands are experiencing with these stressors. That's really important to keep in mind. We need to do the hard work of thinking about how we utilize the landscape for livestock, how climate invasives altered disturbance regimes all come together to affect the basic resistance and resilience of these expansive semi-natural landscapes.

>> Right then, because of the economic marginality of any large-scale inputs, anything that that is an input that costs money needs to be an intervention that, you know, causes the system to turn a corner and begin moving back in the direction. It can't be something that is applied on a regular basis like annual fertilizer, or a biosolids application every five years.

>> Absolutely. And the other economic thing to consider is, you know, with improper stewardship of sites, when you begin having more fire activity, the cost of fire suppression or the cost of post-fire rehabilitation seedings, and herbicide applications, or the costs of risks to human safety or health that are associated with the fires that accompany the loss of perennial bunch grasses and the increases in exotic annuals. I mean, those costs associated with our low-value rangelands, low economic value rangelands are, you know, really paramount to consider here. So the value of good stewardship of our rangelands for site fertility, as well as for making the overall cost benefits workable for our human values for wildlife and, you know, livestock and everything. I mean, that that really, preventative strategies are really critical.

>> I think I have one last question to close us out. If you were talking to a rancher about how they could manage grazing in a way that maintains soil organic matter and species diversity, and soil health and hydrologic function, what would, what would be your rules of thumb?

>> Number one is the integrity of your plant community and its relationship to soils is essential. Preserve what you have that is intact. Because prevention appears to be much more cost effective and feasible than correcting a problem once the plant community becomes degraded. And actually, I think that's the biggest, most important point.

>> Staying on the high side of that threshold, the tipping point?

>> Absolutely. And when a site is lost, and goes to the low side, now a challenge is ahead of us. And those challenges oftentimes can only be met with very strategic adaptive management that involves trying to learn from any treatment actions that might be taken. Usually that's done in a collaborative way to both get the treatments done and also enhance the learning potential. The problem is that we don't know enough about how to deal with these issues. There's a lot of uncertainty out there. And it means that we have to be learning from our management actions. And having that mindset, I think is really important.

>> And the economic problems are multiplicative. You know, once you've tipped over into a degraded stable state, it's worth less economically. But it costs significantly more to try to get it back to something that has economic value.

>> Absolutely.

>> A no win situation.

>> Yeah. And, you know, it's really important to take the long view as well. Oftentimes, for example, after a fire we see sometimes that understandably, rangeland, livestock operators would like to, you know, get livestock back out on landscape to try to sustain their operations. But if that affects the integrity of the perennial bunchgrass community in the long run in ways that increase the likelihood of grass invasions and more fires occurring in the future, while that will, we can expect that to lead to a loss in site fertility and productivity in the long run. So trading off between the short-term needs and benefits with longer term stability. and sustainability I think is really important. And that's a really hard balance for everyone to deal with. Because if we're not careful in the short run, you know, if you were seeing that some livestock operators have a hard time operating in these disturbance regimes, the short term economic challenges can be really severe. If we lose those operators from the landscape, that affects, that also affects the ability to glean ecosystem services from a site in the long term. I think this issue of balancing the short term and the long term utilization of our rangelands that are threatened by disturbances like fire, invasives like cheatgrass is a real challenge.

>> Any other rules of thumb?

>> I think I go back to what we've said a number of times, which is preventative medicine is really critical if you're concerned with having fertile sites that are productive in the long run.

>> Matt, I want to thank you again, for joining me for the interview today. I think these are pretty relevant topics, especially for rangeland-based livestock producers. Some of the stuff is pretty complex. There's a lot to chew on there. Is there, do you have something written up that people can read if they want to get into this topic in a little bit more depth?

>> Yeah, well, thank you, Tip, very much for inviting me to talk to you again. It's always enlightening for me, and I really appreciate the opportunity. One resource that comes to mind I was directly involved with, and it was a product of a network of researchers and managers who are dedicated to understanding the ecology and management prospects for brome grasses like bromes tectorum, which is cheatgrass or bromes [inaudible] which is [inaudible]. And one of the key products from this network of specialists was a book called Exotic Brome Grasses in Arid and Semi-arid Ecosystems of the Western US. There's something like 16 chapters in that book, and a number of them deal with these questions of site fertility, especially how site fertility relates to altered fire regimes and different management options. One chapter directly addresses the ecosystem impacts of exotic annual invaders in the genus bromes. And it reviews many dozens of studies on the topic, and helps us understand to what extent we have good knowledge on the site fertility and the effects of cheatgrass on site fertility, but more importantly, it calls out and identifies where there is knowledge gaps that both the researcher as well as the manager should be aware of. And there's a website on the Springer Publisher page, where this could be obtained. And also just doing a Google search on it will bring it up. And it's also available on the USGS website as well.

>> Excellent, I have not seen that book. So I'll be looking at that. And we will put a link to the Nutrient Network as well as this book on, on the bromes genus in the show notes. Matt Germino, Thank you again for your time.

>> Thank you.

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