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Soil properties and chemical compostition and extractable nutrients

Soil properties and chemical compostition and extractable nutrients.

  • 1986_to_presentgsbbag - Nitrogen mineralization was determined on LTER and Sag River tussock tundra using the buried bag method. Yearly bags have been deployed every August since 1990.

  • 1987_2002gsext - Plant available NH4, NO3, and PO4 was determined at sites near ARC LTER Toolik acidic tundra and at a toposequence along the floodplain of the Sagavanirktuk River using 2 N KCL and weak HCL extracts. This file complies data collected at different times from 1987 through 2001 and includes initial extracts taken for buried bag method of net nitrogen mineralization.

  • 1991gsext - Extractable NH4-N and NO3-N (2 N KCl), PO4-P (0.025 N HCl) and pH (0.01 M CaCl2) were measured on soils from a transect along the Dalton road. Sites are Gus Shaver flowering sites and Arctic LTER sites.

  • 1993gsbulk - Carbon, nitrogen and phosphorus content in thawed soils are described for four arctic tundra vegetation types located near the Toolik Field Station.

  • 1993_to_currentsoilthaw - Late season thaw depth was measured in the ARC LTER experimental plots (Moist Acidic Tussock, Moist Non-acidicTussock, Moist Non-acidic Non-tussock, Wet Sedge) at Toolik Lake, AK using a thaw probe.

  • 1997lgextnuts - Plant available NH4, NO3, and PO4 was determined at three site (LTER Toolik acidic tundra, LTER Toolik nonacidic tundra, and Sagwon acidic tundra) and three community combinations (tussock, watertrack, and snowbed), three times during the season. pH was also determined in July and strong acid phosphorous in August.

  • 1997shextsoilcats - Extractable soil cations (K, Ca, Mg, Na) for intertussock O and B horizon soils on moist acidic and non-acidic tundra.

  • 1997shtotsoilnuts - Total soil cations (Al, Ca, K, Mg, Na, P) for intertussock O and B horizon soils on moist acidic and non-acidic tundra.

  • 20022004gsimwatchem - Water chemistry (NO3, NH4, TDN, DON, DOC) from Imnavait watershed along hillslope. Sample waters were either collected by lysimeters, needle with syringe, or extracting soil with water or 1N KCl.

  • 20032004gsimresin - Concentrations of NO3 and NH4 and d15N of NO3 and NH4 collected on resin bags from 15N addition plots along hillslope in Imnavait watershed.

  • 20032005gsimsoil - Physical (bulk density, soil thickness) and chemical (total C and N, d13C and d15N) information of soil cores taken from 15N addition plots in Imnavait watershed.

  • 2003gsimCFN - Pool size and d15N values for chloroform-extractable N, extractable-N, and non-extractable N pools. Samples collected in Aug. 2003 from 1st Organic Layer of 15N addition plots in Imnavait watershed. 1st Organic Layer = the upper 10 cm of organic soil or, if the organic layer was < 10 cm thick, the entire layer (e.g., there was never > 4 cm of organic soil at Crest).

  • 2005gsimHydrlysN - Hydrolyzable N pool size and 15N atom % of natural and enriched soils collected from Imnavait watershed in summer of 2005.

  • 2006-2007_JD_SnowShrub_Litter_Decomp - In arctic tundra near Toolik Lake, Alaska, we incubated a common substrate in a snow addition experiment to test whether snow accumulation around arctic deciduous shrubs altered the environment enough to increase litter decomposition rates. We compared the influence of litter quality on the rate of litter and N loss by decomposing litter from four different plant functional types in a common site. We used aboveground net primary production values and estimated k values from our decomposition experiments to calculate community-weighted mass loss for each site.

  • 2006-2007_JD_SnowShrub_NetNmineralization - In arctic tundra, near Toolik Lake, Alaska, we quantified net N-mineralization rates under ambient and manipulated snow treatments at three different plant communities that varied in abundance and height of deciduous shrubs. Our objective was twofold: 1) to test whether the amount of snow that accumulates around arctic deciduous shrubs maintains winter soil temperatures high enough to stimulate microbial activity and increase soil N levels (effect of soil microclimate) and 2) to compare the relative effects of shrubs on N availability via effects on the controls over N mineralization (effect of soil organic matter (SOM) quality). Net nitrogen mineralization was measured using in situ soil cores capped with mixed bed ion exchange resin bags. Seperate cores were incubated in the organic and mineral soils at 10 cm depth in the ambient and snow addition treatments located in moist acidic tundra and two seperate shrub tundra plant communities. Organic soil cores were incubated in the summer and winter while mineral soils were only incubated in the winter.

  • 2008Toolik_ProteolyticActivity - The original focus of this study was an analysis of proteolytic enzyme activity of Alaskan arctic tundra soils, however initial results raised questions regarding the method (Watanabe and Hayano, 1995). Thus, the goals of the study changed to 1) an investigation of the method, and 2) a comparison of enzyme activities of two different soil layers from the arctic tundra. Methodological examination included the impact of toluene, used to prevent immobilization of the product, and blank correction of enzyme activity, and a search for a true 6-h linear rate of activity during a 48-hour incubation. We measured native and potential, using casein as an artificial substrate, activities as net amino acid production in mineral and organic soil layer samples. Varying toluene concentration had no clear effect on activity; omitting toluene resulted in zero native activity and reduced potential for the organic samples, but not for the mineral. Comparison of activities with and without blank correction indicated, particularly for potential activity of samples with low native rates, that correction was required for accuracy. Native and potential activity of the organic samples, and native of the mineral were linear for the first 6 h of incubation; linearity was observed during the 6 to 24 h incubation for potential activity of the mineral. Soil layer activity data indicated that native activity was higher in organic soils as compared with mineral. The organic layer potential activity was ten-fold greater than the native, suggesting substrate limitation; potential and native activities did not differ in the mineral layer, indicating substrate sufficiency. Casein addition changed the kinetic pattern for both layers from hyperbolic to sigmoidal for the mineral and linear for the organic, implying different enzyme pools or behavioral changes of existing pools. Native activity based on total soluble protein was higher for the mineral samples relative to the organic, reiterating substrate capacity differences and variations in enzyme/substrate interactions.

  • 2010_MAT_SoilThawTemp_lg - In 2010, thaw depth and soil temperature were measured throughout the growing season in control and fertilized plots in the Arctic LTER's moist acidic tundra sites.

  • 2011_MAT_89_06_NP_aggs_soil_JCM - Soil aggregate size distribution, aggregate carbon and nitrogen, and light fraction carbon were determined for mineral soils in moist acidic tundra. Soil was sampled in control, and N+P plots of the Arctic LTER Moist Acidic Tundra plots established in 1989 and 2006.

  • 2011_MAT_89_06_NP_Enzyme_JCM - Soil samples were collected from control, and N+P plots from within a set of treatments in Arctic LTER Moist Acidic Tundra plots established in 1989 and in 2006 . At the time of sampling the soil was separated into organic horizon, organic/mineral interface, and the upper 5cm of the mineral soil. In the lab the potential activities of seven hydrolytic enzymes was determined using fluorometric techniques (Saiya-Cork et al. 2002) modified following Steinweg et al(.2012).

  • 2013_MM_Shrub_Soil_Characteristics - Organic and mineral soil cores were collected from 18 transects differentiated by shrub height into three replica groups: high (average 64 cm ± SE 1.01); medium (39 ± SE 1); and low (18 ± SE 0.4); and percent plant functional group cover. Replica sample cores were taken from each transect, and after homogenization and K2SO4 extraction, if required, samples were analyzed for % C (carbon) and N (nitrogen); non-purgeable organic C (NPOC); total N (TN); dissolved inorganic and organic N (DIN, DON); microbial biomass C (MB-C) and N (MB-N). As a measure of N status, protease activity (native and potential) was determined together with total free amino acids and total soluble protein. Bulk density and pH values were also measured. K2SO4 extracted samples from a three-month incubation were analyzed as above and net mineralization was assessed.

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