00530nas a2200121 4500008004500000245010200045210006900147100001200216700001900228700002300247700001100270856012700281 In Press eng d 00aEffects of vegetation rooting characteristics on carbonate weathering and critical zone evolution0 aEffects of vegetation rooting characteristics on carbonate weath1 aWen, H.1 aSullivan, P.L.1 aMacpherson, G., L.1 aLi, L. uhttp://knz.lternet.edu/content/effects-vegetation-rooting-characteristics-carbonate-weathering-and-critical-zone-evolution00626nas a2200193 4500008004100000245007400041210006900115300001100184490000800195100002700203700001700230700002300247700002100270700001800291700001700309700001900326700001100345856007600356 2023 eng d00aDrier streams despite a wetter climate in woody-encroached grasslands0 aDrier streams despite a wetter climate in woodyencroached grassl a1303880 v6271 aSadayappan, Kayalvizhi1 aKeen, Rachel1 aJarecke, Karla, M.1 aMoreno, Victoria1 aNippert, J.B.1 aKirk, M., F.1 aSullivan, P.L.1 aLi, Li uhttps://www.sciencedirect.com/science/article/abs/pii/S002216942301330601265nas a2200457 4500008004100000022001300041245013100054210006900185300001100254490000800265100001900273700001900292700001500311700001100326700001400337700001600351700001900367700001400386700001600400700001500416700001600431700001300447700001500460700001500475700001400490700001300504700001800517700001800535700001800553700001500571700001400586700002100600700001800621700001600639700001900655700001900674700002100693700001400714700001200728856006700740 2022 eng d a0012825200aEmbracing the dynamic nature of soil structure: A paradigm illuminating the role of life in critical zones of the Anthropocene0 aEmbracing the dynamic nature of soil structure A paradigm illumi a1038730 v2251 aSullivan, P.L.1 aBillings, S.A.1 aHirmas, D.1 aLi, L.1 aZhang, X.1 aZiegler, S.1 aMurenbeeld, K.1 aAjami, H.1 aGuthrie, A.1 aSingha, K.1 aGimenez, D.1 aDuro, A.1 aMoreno, V.1 aFlores, A.1 aCueva, A.1 aKoop, A.1 aAronson, E.L.1 aBarnard, H.R.1 aBanwart, S.A.1 aKeen, R.M.1 aNemes, A.1 aNikolaidis, N.P.1 aNippert, J.B.1 aRichter, D.1 aRobinson, D.A.1 aSadayappan, K.1 ade Souza, L.F.T.1 aUnruh, M.1 aWen, H. uhttps://linkinghub.elsevier.com/retrieve/pii/S001282522100374300555nas a2200157 4500008004100000245009400041210006900135100002100204700002300225700001900248700001800267700001900285700001800304700001800322856005700340 2022 eng d00aImpacts of riparian and non-riparian woody encroachment on tallgrass prairie ecohydrology0 aImpacts of riparian and nonriparian woody encroachment on tallgr1 aKeen, Rachel, M.1 aNippert, Jesse, B.1 aSullivan, P.L.1 aRatajczak, Z.1 aRitchey, Brynn1 aO’Keefe, K.1 aDodds, W., K. uhttps://link.springer.com/10.1007/s10021-022-00756-700503nas a2200157 4500008004100000245008500041210006900126300001000195490000700205100001200212700001900224700002100243700001900264700001100283856005100294 2021 eng d00aDeepening roots can enhance carbonate weathering by amplifying CO2-rich recharge0 aDeepening roots can enhance carbonate weathering by amplifying C a55-750 v181 aWen, H.1 aSullivan, P.L.1 aMacpherson, G.L.1 aBillings, S.A.1 aLi, L. uhttps://bg.copernicus.org/articles/18/55/2021/00558nas a2200157 4500008004100000245012400041210006900165300001400234490000700248100001900255700001400274700001300288700001400301700002300315856006200338 2020 eng d00aTowards a new conceptual model for groundwater flow in merokarst systems: Insights from multiple geophysical approaches0 aTowards a new conceptual model for groundwater flow in merokarst a4697-47110 v341 aSullivan, P.L.1 aZhang, C.1 aBehm, M.1 aZhang, F.1 aMacpherson, G., L. uhttps://onlinelibrary.wiley.com/doi/abs/10.1002/hyp.1389803035nas a2200229 4500008004100000245012400041210006900165300001100234490000800245520230900253653002402562653001802586653000902604653002002613653002102633653001802654653001002672653001402682100002302696700001902719856006702738 2019 eng d00aDust, impure calcite, and phytoliths: modeled alternative sources of chemical weathering solutes in shallow groundwater0 aDust impure calcite and phytoliths modeled alternative sources o a1188710 v5273 a

In highly reactive, carbonate terrains that constitute more than one-fifth of critical zone landscapes, quantifying bedrock weathering processes may require understanding the realities of carbonate mineral impurity on solubility, biotically-produced minerals as an integral part of leaky biogeochemical cycles, and dust-deposited minerals as important high-surface-area, first-contact solute sources. The potential impact of these processes has not been thoroughly investigated as groundwater solutes are mostly thought to be sourced from chemical reactions with soil and bedrock, although dust is often viewed as an important delivery mechanism of nutrients to other ecosystems, including those in mountain and tropical settings. We present results of computer and hand-calculated (manual) inverse modeling of two years of stream-water chemistry, spanning a dry and a wet year, for a groundwater-fed headwater stream at the Konza Tallgrass Prairie Long-Term Ecological Research Site in northeastern Kansas. Weathering of the limestone and shale bedrock at the site provide a possible source of solutes to the groundwater-fed stream, but our modeling suggests an alternate source considering the pathway of groundwater recharge likely encounters highly reactive phases before encountering bedrock. We used the mineralogy and geochemistry of local dust collected previously, estimates of a possible chemical composition of phytolith containing potassium, and an impure calcite representing measured limestone bedrock chemistry to show that chemical reactions with the current dust flux are adequate to account for the groundwater chemistry. Average annual amounts were about: 1) 380 kg ha−1 yr−1 dust dissolved, 2) 80 kg ha−1 yr−1 bedrock carbonate dissolved, and 3) 320 kg ha−1 yr−1 phytoliths precipitated. Small amounts of cation exchange were also required to balance the models. There were only small differences between the computer and manual inverse models; both methods resulted in up to 4.6 times more mass of dust dissolved than bedrock. We suggest that dust weathering may be a process that occurs widely, considering the ubiquitous dust flux in continental regions.

10aChemical weathering10aCritical zone10aDust10aDust deposition10aHeadwater stream10aInverse model10aKarst10aMerokarst1 aMacpherson, G., L.1 aSullivan, P.L. uhttps://linkinghub.elsevier.com/retrieve/pii/S000925411830398X02019nas a2200157 4500008004100000245005200041210005200093300001100145490000800156520155500164100001901719700002301738700001701761700001601778856006701794 2019 eng d00aEvolution of carbonate and karst critical zones0 aEvolution of carbonate and karst critical zones a1192230 v5273 a

Carbonate terrains (CT) underlie one-fifth of terrestrial, ice-free land and are an important supply of potable water to the world's population, and yet processes endemic to CT critical zones (CZ) and responses of these processes to climatic and anthropogenic pressures are not well understood. Given the rapid dissolution rates and ability to generate well-developed networks of secondary porosity these landscapes can be highly sensitive to impacts from climate change (e.g., modifications of temperature, precipitation, sea level) and human disturbance (e.g., water withdrawal/diversions, changes in land use/land cover). This special issue includes 16 papers focused on CT-CZ processes and potential responses to climatic and human perturbations. Five major themes emerge from these papers, namely: (1) anthropogenic climate and land use changes alter CT-CZ weathering rate and diagenesis, (2) metal and carbon fluxes in CT-CZ will respond to increasing hydrologic variance caused by climate change, (3) endogenous and exogenous processes operating over short time periods (<10,000 yrs) form landscape patterns in carbonate terrains, (4) rates of carbonate mineral dissolution depend on vadose zone and soil thickness, and (5) open systems may not always promote greater carbonate weathering rates in CT-CZ. These findings reflect the importance of carbonate minerals in Earth's CZ, both in terms of processes unique to carbonate minerals, as well as a predictor of future responses to anthropogenic and environmental changes.

1 aSullivan, P.L.1 aMacpherson, G., L.1 aMartin, J.B.1 aPrice, R.M. uhttps://linkinghub.elsevier.com/retrieve/pii/S000925411930318303030nas a2200229 4500008004100000245012900041210006900170300001100239490000800250520230600258653001802564653003102582653001002613653002302623100001902646700001602665700002302681700001102704700001702715700001802732856005002750 2019 eng d00aHow landscape heterogeneity governs stream water concentration-discharge behavior in carbonate terrains (Konza Prairie, USA)0 aHow landscape heterogeneity governs stream water concentrationdi a1189890 v5273 a

Mounting evidence suggests ecosystem changes that alter subsurface water fluxes and carbon dioxide concentrations in carbonate terrains may drive measurable changes in chemical weathering rates, stream water chemistry, and flow path evolution on human timescales. We test this idea by exploring if the encroachment of woody vegetation into grasslands in a carbonate terrain landscape at the Konza Prairie (KS, USA) has resulted in differences in landscape-stream connectivity and, thus, the behavior of stream water solutes. Woody encroachment (up to 60% cover) at Konza has been observed on watersheds, particularly those that experience a fire return interval of four years or greater. We focus on three headwater catchments (two grassland and one woody-encroached) and a downstream confluence, and analyze stream water discharge and chemistry (major anions, cations, and dissolved nutrients) measured from 2015 to 2016.

We observe that the woody-encroached watershed exhibits a greater area-normalized solute flux and greater degree of chemodynamic behavior for most geogenic species compared to the less encroached grassland watersheds. The downstream confluence exhibits the most chemostatic behavior for these same solutes compared to the low order watersheds. We interpret the chemodynamic behavior of the woody-encroached watersheds to arise from a greater diversity of flow paths and solute sources that contribute to this stream. End member mixing analysis (EMMA) supports this hypothesis but also indicates a possible “missing” end member which we interpret to be solutes likely derived from clay weathering along limestone-mudstone boundaries. We invoke differences in rooting systems between grass and woody species to explain the differences in flow paths and solute generation between these headwater sites given that they sit adjacent to each other, dissect the same nearly horizontal (dip 0.1–0.21°NW) lithologic units, and experience the same climate. If these processes hold true at other sites, then the globally observed encroachment of woody vegetation into grasslands may deepen flow paths and enhance chemical weathering fluxes from ecosystems, and over long-time periods alter the trajectory of soil development and landscape evolution.

10aCritical zone10aEnd member mixing analysis10aKarst10awoody encroachment1 aSullivan, P.L.1 aStops, M.W.1 aMacpherson, G., L.1 aLi, L.1 aHirmas, D.R.1 aDodds, W., K. uhttps://doi.org/10.1016/j.chemgeo.2018.12.00202135nas a2200217 4500008004100000245008800041210006900129300001000198490000700208520147500215100002301690700001901713700001801732700001801750700001601768700001601784700001501800700001501815700002301830856006401853 2019 eng d00aIncreasing groundwater CO2 in a midcontinent tallgrass prairie: Controlling factors0 aIncreasing groundwater CO2 in a midcontinent tallgrass prairie C a060080 v983 a

Alkalinity and groundwater CO2 have increased linearly from 1991–2017 at the Konza Prairie Biological Station (KPBS), a tallgrass prairie research site in northeastern Kansas. The projected increase in groundwater alkalinity (as HCO3-) and CO2 based on an earlier trend was confirmed in 2016, with predictions nearly equal to recent values (e.g., 408 ppm vs 410 ppm as HCO3-, respectively). Both the water balance and groundwater CO2 trends within the study watershed could be impacted by long-term changes in land use and climate: 1) encroachment of woody vegetation (1983–2012) as a result of the 4-year fire return interval, 2) re-introduction of bison (phased in, 1994–2006), 3) increases in air temperature, and 4) changes in precipitation patterns. If only linear processes are driving the observed water chemistry changes, then the linear increase in air temperature (1983–2017) that stimulates soil respiration may be the most likely factor enhancing groundwater HCO3- and CO2, as air temperature has risen ~1 to 1.4°C over 34 years. If groundwater chemistry is driven by more threshold behaviour, woody encroachment, which was linear but in three distinct phases, may drive groundwater chemistry. The ~2 to 3‰ decrease in the discontinuous δ13C data in the groundwater-dominated stream suggests enhanced inputs of microbially-respired labile carbon, CO2 sourced from C3 (woody vegetation), or a combination of the two.

1 aMacpherson, G., L.1 aSullivan, P.L.1 aStotler, R.L.1 aNorwood, B.S.1 aChudaev, O.1 aKharaka, Y.1 aHarmon, R.1 aMillot, R.1 aShouakar-Stash, O. uhttps://www.e3s-conferences.org/10.1051/e3sconf/2019980600801883nas a2200133 4500008004100000245008900041210006900130300001100199490000800210520140200218100002301620700001901643856008701662 2019 eng d00aWatershed-scale chemical weathering in a merokarst terrain, northeastern Kansas, USA0 aWatershedscale chemical weathering in a merokarst terrain northe a1189880 v5273 a

Carbonate weathering in the merokarst landscape at the Konza Prairie (near Manhattan, KS) is governed by kinetically rapid reaction rates, similar to other carbonate settings. The geology of the site consists of repeating couplets of shale and limestone mantled by Pleistocene loess, on which most soils are built. The headwater stream that is the subject of this study is intermittent and well connected to the secondary porosity in the limestone aquifers, such that the water chemistry is groundwater-dominated. Despite increasing in situ weathering rates shown by increasing solute concentrations, long-term (~21 of 24 years) decline in stream-water discharge has reduced chemical denudation. The current chemical denudation rate is 0.02 mm yr−1. Limestone bedrock thickness (~26.6 m) is 38% of total bedrock thickness (~70 m); the present landscape would have taken 1–4 million years to dissolve at current weathering rates. Despite paleogeographic reconstructions suggesting exposure for the past 260 Ma, estimates of the time to erode younger strata using current physical and chemical denudation rates are 80–159 Ma, still much less than the age of the rocks. An alternate source of material, dust, is proposed that may slow limestone weathering, which in turn protects shales from physical erosion, thereby slowing landscape evolution.

1 aMacpherson, G., L.1 aSullivan, P.L. uhttps://www.sciencedirect.com/science/article/abs/pii/S0009254118305874?via%3Dihub02414nas a2200205 4500008004100000245011200041210006900153300001100222490000700233520174800240100001701988700002302005700001902028700002102047700002302068700001702091700001402108700001602122856007002138 2018 eng d00aDeveloping a conceptual framework of landscape and hydrology on tallgrass prairie: A critical zone approach0 aDeveloping a conceptual framework of landscape and hydrology on  a1 - 110 v173 a

Agricultural intensification and urbanization have greatly reduced the extent of tallgrass prairie across North America. To evaluate the impact of these changes, a reference ecosystem of unperturbed prairie is required. The Konza Prairie Biological Station in northeastern Kansas is a long-term research site at which a critical zone approach has been implemented. Integration of climatic, ecologic, and hydropedologic research to facilitate a comprehensive understanding of the complex environment provides the basis for predicting future aquifer and landscape evolution. We present a conceptual framework of the hydrology underpinning the area that integrates the extensive current and past research and provides a synthesis of the literature to date. The key factors in the hydrologic behavior of Konza Prairie are climate, ecology, vadose zone characteristics and management, and groundwater and bedrock. Significant interactions among these factors include bedrock dissolution driven by cool-season precipitation and hence a climatic control on the rate of karstification. Soil moisture dynamics are influenced at various timescales due to the short- and long-term effects of prescribed burning on vegetation and on soil physical characteristics. The frequency of burning regimes strongly influences the expansion of woody species in competition with native tallgrasses, with consequent effects on C and N dynamics within the vadose zone. Knowledge gaps exist pertaining to the future of Konza Prairie (a model for US tallgrass prairie)—whether continued karstification will lead to increasingly flashy and dynamic hydrology and whether compositional changes in the vegetation will affect long-term changes in water balances.

1 aVero, S., E.1 aMacpherson, G., L.1 aSullivan, P.L.1 aBrookfield, A.E.1 aNippert, Jesse, B.1 aKirk, M., F.1 aDatta, S.1 aKempton, P. uhttps://dl.sciencesocieties.org/publications/vzj/pdfs/17/1/170069