01464nas a2200181 4500008004100000245008700041210006900128300001300197490000600210520090200216100001701118700001601135700001701151700001701168700002001185700002001205856005701225 2019 eng d00aDecadal-scale shifts in soil hydraulic properties induced by altered precipitation0 aDecadalscale shifts in soil hydraulic properties induced by alte aeaau66350 v53 a

Soil hydraulic properties influence the partitioning of rainfall into infiltration versus runoff, determine plant-available water, and constrain evapotranspiration. Although rapid changes in soil hydraulic properties from direct human disturbance are well documented, climate change may also induce such shifts on decadal time scales. Using soils from a 25-year precipitation manipulation experiment, we found that a 35% increase in water inputs substantially reduced infiltration rates and modestly increased water retention. We posit that these shifts were catalyzed by greater pore blockage by plant roots and reduced shrink-swell cycles. Given that precipitation regimes are expected to change at accelerating rates globally, shifts in soil structure could occur over broad regions more rapidly than expected and thus alter water storage and movement in numerous terrestrial ecosystems.

1 aCaplan, J.S.1 aGimenez, D.1 aHirmas, D.R.1 aBrunsell, N.1 aBlair, John, M.1 aKnapp, Alan, K. uhttps://advances.sciencemag.org/content/5/9/eaau663503030nas 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.2018.12.002