 Pamela Sullivan. She is a professor at Oregon State University. Our research focuses on developing and understanding how terrestrial water storage and water quality are influenced by humans and by climatic perturbations. And the title of Pam's talk is, are rate changes in biotic processes altering subsurface hydrologic partitioning in the end of the sea? And with that, I'm going to give the floor to Pam. Well, good morning, everyone. While I get my screen shared, I'm assuming everyone can hear and see everything. So I modified my title a little bit this morning to make it something a little more tangible. But this is a question. And I think maybe we don't have an answer to this question. And in my opinion, it's, it might be something that's exciting for you all to think about as, as you move through this, this meeting. And it's something I've been thinking about with a whole cast of characters, as you can see at the bottom, faculty members and postdocs and graduate students and undergraduate students. And what we're asking is, is subsurface plumbing responding to climate and land use change in the Anthropocene? And I want to take a second and I want you to think, does it, if it is changing, does it matter? Would you want to be able to bring that into your models? Now, the idea behind this is that we have anthropocene, climate change that's taking place in the Anthropocene. We know that land cover has been changing. Our atmospheric concentrations of CO2 are rising, which can have cascading biotic effects. And so can the eutrophication that's occurring across our landscapes. So we're asking the question, are all of these processes altering that subsurface structure? And if they alter that subsurface structure, what we have taking place is the potential for changes in the hydraulic properties of our soils and our regolith, changes in the preferential flow paths of those systems. And then we also have then changes in the depth distribution of the organic carbon in these systems. These feedback to them influence potentially the storage of water on terrestrial earth. It's partitioning between different compartments of the mirror service and the ground waters. This impacts the functioning and distribution of our microbial communities in these environments. And that functioning and that distribution then feeds back to influence those hydraulic properties and to influence the rate at which dissolved organic carbon is being decomposed. These therefore interact together, the way that water flows, the way that carbon cycled to alter the propensity of weathering, which feeds back into our climate systems. But just in and of itself, that water storage has the potential to impact our climates as well. So the premise of this talk is kind of based on one fact that the distribution of pores in our subsurface govern the way that water flows. And that if you change that distribution of pores, you change that flow path, you change those water residence times, you change water mineral interactions, and therefore you can change water chemistry. This is a figure by Leisham Jen. It's a great one because it depicts macro pore presence that could be influencing vertical flow, but it also shows the interaction between horizons and horizon boundaries that can help to support lateral flow in the subsurface as well. So the interactions of these different kinds of properties of our soil can begin to austrially change the way that water flows through it. So if we take a really simplified approach to this, we can say, okay, well are there changes that are taking place in our landscape such that they change the proportion of interflow and the proportion of groundwater recharge such that they might even impact the chemistry and the water quantities and the timing of those to our streams themselves. Now this is a simple character, a simple figure by Leely, but I think it helps us to understand these potential impacts that are taking place. Now here this is one example from the Coal Creek. It's in Gunnison, Colorado, so not far from at least the land lab area right now. And what we're looking at here are concentrations of two constituents, dissolved organic carbon on the top and magnesium on the bottom. And what's been observed as we've had this decline in this environment of 40% snow cover over the last 20 plus years is a change in the concentrations of dissolved organic carbon making it into the streams. And here that's about a tripling or quadrupling, but we haven't seen it in some of the geogenic species like magnesium, but we have seen it in things like iron and manganese. And so there's a question here. Is this simply just a biogeochemical cycle that is changing or is it a relationship to a change in flow past in the system that are delivering different solutes to the system? And so we're taking modeling approaches to start thinking about that. Now there are other observations that are taking place that have shown us that soil structure is changing and it may be changing rapidly at least in the last 15 years if maybe not even in the last couple of decades. So this is work by Daniel Hermes, 48,000 petons through a natural resource conservation service. He used that with the changes in our past precipitation of the last 50 years to examine the soil structure in its response to changes in mean annual precipitation. What was observed here is that we have mean annual precipitation regressed against mean residual effective porosity. Now that residual effective porosity means that we've actually taken it and we've been able to normalize it for clay content and for organic matter content and then look to see what's driving these changes or how it relates to mean annual precipitation. And we see that in the A horizon and the B horizon, it declines that effective porosity with increasing mean annual precipitation. Now you could say to me okay well this could happen over very long time periods as these soils are forming. But what we see is that soils that have been plowed recently that this rearrangement of fabric is also taking place. If we use this idea of fabric being rearranged as a result of changes in our climate on mean annual precipitation and we run that out into the future to 2100, we can then begin to think what does that mean for our saturated hydraulic conductivity, the way that water flows through the system. We could look at an area like the Pacific Northwest where I live right now and what you can see is that you could have a reduction in saturated hydraulic conductivity by up to 60%. Now porous structure isn't only changing near the surface. We have evidence that's from the shale hills critical zone observatory but also other places like the Snake River which is showing that they may also be sensitive at depth to changes in groundwater table dynamics. So here's just some drill core material going all the way down to 20 meters. When we're at depth, we see this presence of pyrite framboids. As we move to the surface, we see the opening of porosity and slight infilling of iron oxides. In this environment, this location where this transition occurs, we call that the pyrite reaction front, it's actually governed by the position of where we have deep dissolved rich permanent interflow which is rich in dissolved oxygen and then we have our regional groundwater which is low in dissolved oxygen. Where these interact, these young waters and these old waters actually governs that boundary that's there and so we can think to ourselves well over time if our incoming precipitation changes for land cover changes in these environments or if pumping in some environment changes and changes the interaction of these water table dynamics then we could have cascading effects on the generation of porosity at depth. Now it's not only just the idea that we have changes in our structure that are resulting maybe from mean annual precipitation or changes in water table dynamics but we also see that there's something very powerful that's been changing in the Anthropocene and that's the potential that rooting depth has been changing globally. So this is work by a PhD student Emma Hauser at the University of Kansas. Here what you're looking at is a comparison of rooting depth distributions pre-anthropocene and rooting depth distributions now. You'll see in the red we're getting to shallower roots and the blue we're getting to deeper roots and what it demonstrates to us at least since the start of the Anthropocene is we have shallow roots by 16 centimeters globally but if we run that on into the future to 2100 what we find is that even given different kinds of climate scenarios we will still be shelling by another 60 centimeters globally. Now these roots are really important because they help to support potentially up to 70 percent of the macro pores that are in our soils so those macro pores that we have are about 50 nanometers or bigger in size and they are what helps to transport our liquids some more particles in our gases and systems. So if we take kind of a conceptual image of this we can think to ourselves well macro pores themselves they only represent two percent of the soil volume or regular volume but they actually in control 70 percent of the water flow potentially fits through those so we have to ask the question as our landscapes change right let's say we have a woodied environment and that woody environment changes we have some macro pores that are left behind what does it actually mean as our land cover itself changes does it actually alter the hydraulic partitioning of these environments. So there's some other kinds of fun research that's coming to light right now and this is work done by Sharon Billings lab at the Calhoun Critical Zone Observatory and she puts forward what she calls the below ground wetterman hypothesis and in this what we what we state is that the Anthropocene's modification to rooting networks and ecosystems imparts structural and biogeochemical signatures deep within regulus profiles. Now we know that we can change things near the surface if we change our land cover but what she's what we're showing here is that here in the old growth system compared to this agriculture I'm ever generating pine in this environment we see that we have at depth two meters really large differences in the rooting densities of these environments but we also see really large differences in the actual chemistry and the biogeochemical processes that might be taking place so I'll bring your eye over here to these hardwood systems and what we see is that the organic acid concentration compared to the soil organic carbon content is much greater in these at depth in these environments compared to regenerating pine and agriculture so we have this potential for for stimulating more weathering in the system down here in addition what we see is that at least at two meters of depth 22 percent more modern carbon at depth here in this hardwood system than compared to what you might have in regenerating primes or agricultural systems so it indicates to us there's these large changes that are potentially taking place in the subsurface not only in terms of its physical structure but its biogeochemical interactions as well so this is work that's been done by my phg student Erin Coop and here we're trying to ask the question okay to what degree do these soils start to even matter to our climate system themselves and so using that same nrcs database and and conglomerating it using huck six levels he looked to say okay well each of these watersheds or each of these huck six levels and basins that we see how far do they fall away from the butico so how much are they able to meet their evaporative domain and we said okay well that distance that they fall away from this um empirical curve can we explain that actually using the information about the soils themselves and so when we analyze this data what we what is revealed is that soil structure which is the roundness and the solidity and the organic carbon content along with the eridity index is able to help explain about 50 of the deviation away from that butico curve so it's giving us this hint right that these soils are playing such an important role potentially in governing what's taking place in our climates so the question is do these changes to the critical zone subsurface be back to govern climate so before we had our our pre-anthropocene kind of condition right we had one rooting network we had hydrologic cycle that was taking place in one one manner we moved forward into the Anthropocene in some places we've shallowed our roots in some places we've deepened our roots and we can take a look and ask the question well what does that mean that rooting depth distribution in this instance to the degree of coupling to our atmosphere and to the critical zone weathering engine and we might we might theorize right that as we change those rooting depth distributions we actually shift the degree of coupling between our atmosphere and that weathering engine so the question is is this important for climate projections so i'm going to open it up for questions and thank you very much and let you know about a couple of upcoming opportunities