02923nas a2200181 4500008004100000245015400041210006900195260004800264300000700312490000900319520225400328653002202582653001502604653002902619100002002648700002502668856004802693 2023 eng d00aCharacterizing velocity gradients in the McMurdo Dry Valleys with high-resolution optical imagery, feature-tracking methods, and in situ observations0 aCharacterizing velocity gradients in the McMurdo Dry Valleys wit aBoulder, CObUniversity of Colorado Boulder a430 vM.S.3 a

In the water-limited McMurdo Dry Valleys – the largest ice-free region of Antarctica – glaciers are the only significant source of meltwater to ephemeral streams and ecosystems. Understanding changes to the flow of these glaciers, along with characterizing how they are growing or shrinking, can elucidate how these physical controls on the region’s hydrology and ecology are responding to changing environmental conditions. Because in situ observations are difficult to collect and discrete by nature, various computer vision techniques are increasingly used to track glacier surface velocities from satellite optical and radar datasets. The most common of these techniques is image cross-correlation in the form of template matching or particle image velocimetry (PIV). Although exact methods vary, generally, cross-correlation works by co-registering temporally offset image pairs using similarity in pixel values resulting from distinctive surface features, such as crevasses, large sastrugi and snow dunes. When surface features are well-resolved with respect to an image pair’s spatial resolution, and well-preserved relative to its temporal resolution, velocity estimates can have sub-pixel precision. However, when glaciers lack meaningful surface texture – a common occurrence for the low-gradient, frozen-bed glaciers of the McMurdo Dry Valleys – cross correlation performs poorly. Using high-resolution (sub-meter per pixel) imagery can help derive texture from minor cracks and small erratics on otherwise smooth, uncrevassed surfaces, but additional adaptations are needed to improve cross correlation performance. These include additional filtering and histogram stretching steps, along with informed search area windows. Velocity estimates derived from this workflow are shown to be comparable to recorded ranges, in situ measurements, and manual feature tracking, but provide a much higher spatial and temporal resolution dataset. Alongside contemporaneous analyses of glacier mass balance, terminal thickness and surface roughness, these glacier velocity data help characterize how glaciers are dynamically evolving in response to environmental conditions in the Dry Valleys.

10across correlation10acryosphere10aglacier surface velocity1 aVanderwilt, Mia1 aGooseff, Michael, N. uhttps://www.proquest.com/docview/291637751902219nas a2200349 4500008004100000022001400041245012300055210006900178260001200247520113200259653000901391653001901400653001601419653001201435653000901447653001301456100002001469700002501489700001601514700002501530700002101555700001701576700002501593700002501618700002101643700002501664700002601689700002201715700002301737700001801760856009101778 2022 eng d a0006-356800aCross-site comparisons of dryland ecosystem response to climate change in the US Long-Term Ecological Research Network0 aCrosssite comparisons of dryland ecosystem response to climate c c08/20223 a

Long-term observations and experiments in diverse drylands reveal how ecosystems and services are responding to climate change. To develop generalities about climate change impacts at dryland sites, we compared broadscale patterns in climate and synthesized primary production responses among the eight terrestrial, nonforested sites of the United States Long-Term Ecological Research (US LTER) Network located in temperate (Southwest and Midwest) and polar (Arctic and Antarctic) regions. All sites experienced warming in recent decades, whereas drought varied regionally with multidecadal phases. Multiple years of wet or dry conditions had larger effects than single years on primary production. Droughts, floods, and wildfires altered resource availability and restructured plant communities, with greater impacts on primary production than warming alone. During severe regional droughts, air pollution from wildfire and dust events peaked. Studies at US LTER drylands over more than 40 years demonstrate reciprocal links and feedbacks among dryland ecosystems, climate-driven disturbance events, and climate change.

10aANPP10aclimate change10aDisturbance10adrought10aLTER10awildfire1 aHudson, Amy, R.1 aPeters, Debra, P. C.1 aBlair, J.M.1 aChilders, Daniel, L.1 aDoran, Peter, T.1 aGeil, Kerrie1 aGooseff, Michael, N.1 aGross, Katherine, L.1 aHaddad, Nick, M.1 aPastore, Melissa, A.1 aRudgers, Jennifer, A.1 aSala, Osvaldo, E.1 aSeabloom, Eric, W.1 aShaver, Gaius uhttps://academic.oup.com/bioscience/advance-article/doi/10.1093/biosci/biab134/665484002885nas a2200241 4500008004100000245006300041210006200104260004100166300001200207520209300219653003102312653003602343653002402379653001902403653002402422100001602446700001702462700002302479700001702502700002402519700002502543856007502568 2021 eng d00aChemical weathering in the McMurdo Dry Valleys, Antarctica0 aChemical weathering in the McMurdo Dry Valleys Antarctica aHoboken, NJbJohn Wiley & Sons, Inc. a205-2163 a

While chemical weathering has not always been considered an active process in the McMurdo Dry Valleys (MDV), Antarctica, long‐term geochemical and hydrological investigations have provided an overall better understanding of chemical weathering in this polar desert environment. Liquid water on the landscape is limited to stream channels as well as shallow subsurface melt features, as there is no overland flow. Stream total suspended sediment loads are low, with the sources of sediment from stream channels, aeolian input, and/or from the surfaces of glaciers. MDV soils contain high concentrations of soluble salts with little clay material, but since absent of water, these soils are a minimal location of chemical weathering. Hyporheic zones exchange water during streamflow, and these areas control the stream geochemistry over various temporal scales. Hyporheic zones promote rapid aluminosilicate weathering by moving dilute glacial meltwater into intimate contact with sediment surfaces. Rapid weathering of the aluminosilicates in the streambed and hyporheic zones is the most plausible explanation for chemostasis observed in these streams, indicating that little to no catchment processes are necessary to explain the observed chemostasis in the MDV. Shallow subsurface waters with distinct geochemical signatures have much higher dissolved Si concentrations than the stream waters and indicate that they are responsible for enhanced aluminosilicate weathering in this polar desert environment. The dissolution of CaCO3 is also a major process in the hyporheic zones as generally the streams are unsaturated with respect to calcite. Cation‐exchange reactions are also important in the evolution from Na‐Cl brines to Ca‐Cl brines within the soil column, while authigenic CaCO3 can both dissolve and precipitate depending on the condition of the system. Recently, stream channel landscapes are changing due to the melting of buried ice, creating thermokarst and water track features, resulting in a sediment and solute influx to the stream.

10aaluminosilicate weathering10aCaCO3 dissolution/precipitation10achemical weathering10ahyporheic zone10aMcMurdo Dry Valleys1 aHunt, Allen1 aEgli, Markus1 aFaybishenko, Boris1 aLyons, Berry1 aLeslie, Deborah, L.1 aGooseff, Michael, N. uhttps://agupubs.onlinelibrary.wiley.com/doi/10.1002/9781119563952.ch1104166nas a2200565 4500008004100000022001400041245007900055210006900134260001200203300001100215490000700226520245300233653001802686653002702704653001902731653001902750653001202769653001202781653001502793653008902808653002002897100002302917700002502940700002602965700002702991700002103018700002503039700001703064700002203081700002903103700002603132700002403158700002603182700002403208700002103232700001603253700002703269700002403296700002303320700002203343700002403365700002303389700001503412700002203427700002103449700002203470700002603492700002403518856005803542 2021 eng d a2150-892500aConnectivity: Insights from the U.S. Long Term Ecological Research Network0 aConnectivity Insights from the US Long Term Ecological Research  c05/2021 ae034320 v123 a

Ecosystems across the United States are changing in complex and surprising ways. Ongoing demand for critical ecosystem services requires an understanding of the populations and communities in these ecosystems in the future. This paper represents a synthesis effort of the U.S. National Science Foundation-funded Long-Term Ecological Research (LTER) network addressing the core research area of “populations and communities.” The objective of this effort was to show the importance of long-term data collection and experiments for addressing the hardest questions in scientific ecology that have significant implications for environmental policy and management. Each LTER site developed at least one compelling case study about what their site could look like in 50–100 yr as human and environmental drivers influencing specific ecosystems change. As the case studies were prepared, five themes emerged, and the studies were grouped into papers in this LTER Futures Special Feature addressing state change, connectivity, resilience, time lags, and cascading effects. This paper addresses the “connectivity” theme and has examples from the Phoenix (urban), Niwot Ridge (alpine tundra), McMurdo Dry Valleys (polar desert), Plum Island (coastal), Santa Barbara Coastal (coastal), and Jornada (arid grassland and shrubland) sites. Connectivity has multiple dimensions, ranging from multi-scalar interactions in space to complex interactions over time that govern the transport of materials and the distribution and movement of organisms. The case studies presented here range widely, showing how land-use legacies interact with climate to alter the structure and function of arid ecosystems and flows of resources and organisms in Antarctic polar desert, alpine, urban, and coastal marine ecosystems. Long-term ecological research demonstrates that connectivity can, in some circumstances, sustain valuable ecosystem functions, such as the persistence of foundation species and their associated biodiversity or, it can be an agent of state change, as when it increases wind and water erosion. Increased connectivity due to warming can also lead to species range expansions or contractions and the introduction of undesirable species. Continued long-term studies are essential for addressing the complexities of connectivity. The diversity of ecosystems within the LTER network is a strong platform for these studies.

10aalpine tundra10aAntarctic polar desert10aarid grassland10aarid shrubland10acoastal10aestuary10asalt marsh10aSpecial Feature: Forecasting Earth’s Ecosystems with Long-Term Ecological Research10aurban ecosystem1 aIwaniec, David, M.1 aGooseff, Michael, N.1 aSuding, Katharine, N.1 aJohnson, David, Samuel1 aReed, Daniel, C.1 aPeters, Debra, P. C.1 aAdams, Byron1 aBarrett, John, E.1 aBestelmeyer, Brandon, T.1 aCastorani, Max, C. N.1 aCook, Elizabeth, M.1 aDavidson, Melissa, J.1 aGroffman, Peter, M.1 aHanan, Niall, P.1 aHuenneke, L1 aJohnson, Pieter, T. J.1 aMcKnight, Diane, M.1 aMiller, Robert, J.1 aOkin, Gregory, S.1 aPreston, Daniel, L.1 aRassweiler, Andrew1 aRay, Chris1 aSala, Osvaldo, E.1 aSchooley, Robert1 aSeastedt, Timothy1 aSpasojevic, Marko, J.1 aVivoni, Enrique, R. uhttps://onlinelibrary.wiley.com/doi/10.1002/ecs2.343202111nas a2200205 4500008004100000245010700041210006900148260001200217300001600229490000700245520142400252100002401676700002201700700002501722700002101747700002101768700002001789700002501809856007101834 2021 eng d00aCounting carbon: Quantifying biomass in the McMurdo Dry Valleys through orbital and field observations0 aCounting carbon Quantifying biomass in the McMurdo Dry Valleys t c10/2021 a8597 - 86230 v423 a

We use correlative field studies and high-resolution multispectral remote sensing data from the WorldView-2 instrument to estimate the abundance of photosynthetically active biomass (photoautotrophs consisting primarily of microbial mats and mosses) in Canada Stream in Taylor Valley, McMurdo Dry Valleys (MDV), Antarctica. In situ field investigations were performed to (1) acquire ground validation targets for atmospherically correcting satellite imagery, (2) derive spectra of “pure” geologic and biological endmembers, (3) estimate photoautotroph cover from remote sensing data, and (4) convert these coverage estimates to biomass using data collected in the field. Our results suggest that, on the morning of 12 December 2018, the Canada Stream system contained more than 3,800 kg of photosynthetically active carbon. Extrapolating our unmixing results to the entirety of the Fryxell basin of Taylor Valley, Antarctica, we model the presence of more than 750,000 kg of photosynthetically active carbon across the landscape and carbon fixation rates roughly equivalent to five hectares of tropical rainforest. The ability to spatially and temporally quantify the amount of photosynthetically active biomass using remote sensing data in the MDV of Antarctica is a revolutionary development that will help elucidate the ecological drivers and environmental responses in this cold desert landscape.

1 aSalvatore, Mark, R.1 aBarrett, John, E.1 aBorges, Schuyler, R.1 aPower, Sarah, N.1 aStanish, Lee, F.1 aSokol, Eric, R.1 aGooseff, Michael, N. uhttps://www.tandfonline.com/doi/full/10.1080/01431161.2021.198155902723nas a2200229 4500008004100000245015600041210006900197260001200266300001600278490000700294520192000301100002202221700002102243700002402264700002002288700002502308700001702333700002402350700002902374700002502403856006502428 2017 eng d00aCharacterizing hyporheic exchange processes using high-frequency electrical conductivity-discharge relationships on subhourly to interannual timescales0 aCharacterizing hyporheic exchange processes using highfrequency  c05/2017 a4124 - 41410 v533 a

Concentration-discharge (C-Q) relationships are often used to quantify source water contributions and biogeochemical processes occurring within catchments, especially during discrete hydrological events. Yet, the interpretation of C-Q hysteresis is often confounded by complexity of the critical zone, such as numerous source waters and hydrochemical nonstationarity. Consequently, researchers must often ignore important runoff pathways and geochemical sources/sinks, especially the hyporheic zone because it lacks a distinct hydrochemical signature. Such simplifications limit efforts to identify processes responsible for the transience of C-Q hysteresis over time. To address these limitations, we leverage the hydrologic simplicity and long-term, high-frequency Q and electrical conductivity (EC) data from streams in the McMurdo Dry Valleys, Antarctica. In this two end-member system, EC can serve as a proxy for the concentration of solutes derived from the hyporheic zone. We utilize a novel approach to decompose loops into subhysteretic EC-Q dynamics to identify individual mechanisms governing hysteresis across a wide range of timescales. We find that hydrologic and hydraulic processes govern EC response to diel and seasonal Q variability and that the effects of hyporheic mixing processes on C-Q transience differ in short and long streams. We also observe that variable hyporheic turnover rates govern EC-Q patterns at daily to interannual timescales. Last, subhysteretic analysis reveals a period of interannual freshening of glacial meltwater streams related to the effects of unsteady flow on hyporheic exchange. The subhysteretic analysis framework we introduce may be applied more broadly to constrain the processes controlling C-Q transience and advance understanding of catchment evolution. 

1 aSingley, Joel, G.1 aWlostowski, Adam1 aBergstrom, Anna, J.1 aSokol, Eric, R.1 aTorrens, Christa, L.1 aJaros, Chris1 aWilson, Colleen, E.1 aHendrickson, Patrick, J.1 aGooseff, Michael, N. uhttp://onlinelibrary.wiley.com/doi/10.1002/2016WR019739/full02223nas a2200205 4500008004100000245012900041210006900170260001200239300001200251490000700263520146400270100001701734700002401751700002401775700002501799700002201824700003301846700001501879856012301894 2014 eng d00aCharacterization of Growing Bacterial Populations in McMurdo Dry Valley Soils through Stable Isotope Probing with 18O-water.0 aCharacterization of Growing Bacterial Populations in McMurdo Dry c08/2014 a415-4250 v893 aSoil microbial communities of the McMurdo Dry Valleys, Antarctica (MDV) contain representatives from at least fourteen bacterial phyla. However, given low rates of microbial activity, it is unclear whether this richness represents functioning rather than dormant members of the community. We used stable isotope probing (SIP) with (18) O-water to determine if microbial populations grow in MDV soils. Changes in the microbial community were characterized in soils amended with H2 (18) O and H2 (18) O-organic matter. Sequencing the 16S rRNA genes of the heavy and light fractions of the bacterial community DNA shows that DNA of microbial populations was labeled with (18) O-water, indicating these micro-organisms grew in the MDV soils. Significant differences existed in the community composition of the heavy and light fractions of the H2 (18) O and H2 (18) O-organic matter amended samples (Anosim P < 0.05 of weighted Unifrac distance). Control samples and the light DNA fraction of the H2 (18) O amended samples were dominated by representatives of the phyla Deinococcus-Thermus, Proteobacteria, Planctomyces, Gemmatimonadetes, Actinobacteria and Acidobacteria, whereas Proteobacteria were more prevalent in the heavy DNA fractions from the H2 (18) O-water and the H2 (18) O-water-organic matter treatments. Our results indicate that SIP with H2 (18) O can be used to distinguish active bacterial populations even in this low organic matter environment.1 aSchwartz, E.1 aVan Horn, David, J.1 aBuelow, Heather, N.1 aGooseff, Michael, N.1 aBarrett, John, E.1 aTakacs-Vesbach, Cristina, D.1 aOkie, J.G. uhttps://mcm.lternet.edu/content/characterization-growing-bacterial-populations-mcmurdo-dry-valley-soils-through-stable00701nas a2200193 4500008004100000245009100041210006900132300001200201490000600213100002500219700002200244700002700266700001500293700002200308700002200330700001200352700003300364856011000397 2007 eng d00aControls on the spatial dimensions of wetted hydrologic margins of two antarctic lakes0 aControls on the spatial dimensions of wetted hydrologic margins  a841-8480 v61 aGooseff, Michael, N.1 aBarrett, John, E.1 aNorthcott, Melissa, L.1 aBate, Brad1 aHill, Kenneth, R.1 aZeglin, Lydia, H.1 aBobb, M1 aTakacs-Vesbach, Cristina, D. uhttps://mcm.lternet.edu/content/controls-spatial-dimensions-wetted-hydrologic-margins-two-antarctic-lakes