uid=ARC,o=EDI,dc=edirepository,dc=org all public read 2006-2007_JD_SnowShrub_NetNmineralization Net nitrogen mineralization from shrub gradient and snow manipulations, near Toolik field station, collect in the summer of 2006 and winter of 2006-2007 Jennie DeMarco
Center for Environment and Sustainability, Western State Colorado University, 600 N. Adams St. Gunnison CO 81231 US
jdemarco@western.edu https://www.jenniedemarco.com/
Michelle Mack
Northern Arizona University, Center for Ecosystem Science and Society, PO Box 5620 Northern Arizona University Center for Ecosystem Science and Society PO Box 5620 AZ 86011 US
Michelle.Mack@nau.edu https://orcid.org/0000-0003-1279-4242
M. Syndonia Bret-Harte
Institute of Arctic Biology,Irving I room 311 Fairbanks AK 99775-7000 US
msbretharte@alaska.edu https://orcid.org/0000-0001-5151-3947 associated researcher
2009 English
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.
inorganic nutrients Core Areas inorganic nutrients soil organic matter dissolved organic nitrogen nitrification mineralization soil temperature LTER Controlled Vocabulary resin bags shrub tundra snow manipulation Toolik Field Station Arctic LTER Vocabulary
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https://arc-lter.ecosystems.mbl.edu/2006-2007jdsnowshrubnetnmineralization Low shrub tundra fence: Snow fence snow manipulation experiment in deciduous shrub (low height and aboundance), west of Toolik Field Station and south of Toolik Lake. -149.613998413086 -149.613998413086 68.621101379395 68.621101379395 771 771 meter Medium shrub fence: Snow fence snow manipulation experiment in deciduous shrub (medium height and abundace), east of Toolik Field Station and southeast of Toolik Lake -149.578002929688 -149.578002929688 68.633499145508 68.633499145508 748 748 meter High shrub tundra fence 1: Snow fence one snow manipulation experiment in deciduous shrub (high height and abundace), east of Toolik Field Station and northeast of Toolik Lake -149.569000244141 -149.569000244141 68.637397766113 68.637397766113 749 749 meter High shrub tundra fence 2: Snow fence one snow manipulation experiment in deciduous shrub (high height and abundace), east of Toolik Field Station and northeast of Toolik Lake -149.567001342773 -149.567001342773 68.638702392578 68.638702392578 754 754 meter 2006-09-01 2007-09-01 species Vaccinium vitis-idaea species Vaccinium uliginosum species Salix richardsonii species Salix pulchra species Betula nana not ongoing-Data has been published in DeMarco et al. 2014. Effects of arctic shrub expansion on biophysical versus biogeochemical drivers of litter decomposition. Ecology In press. Updated Metadata sheet Version2: Keywords added Version 3: Keywords and publication info updated (Dec2013-JD) Version 4: Checked keywords against the LTER network preferred list and replaced non-preferred terms. Jim L 27Jan14 Version 5: Changed Distrubution URL since the LTER network DAS system is being discontinued. JimL 9Apr2015 Arctic_LTER Information Manager Arctic Long Term Ecological Research
7 M B L St Woods Hole MA 02536 US
(508) 548-3705 arc_im@mbl.edu
Arctic Long Term Ecological Research
Site Selection: In the fall of 2005, three sites were selected that varied primarily in deciduous shrub abundance, hereafter referred to as low, medium and high shrub sites. Sites were chosen to have similar state factors (climate, relief, parent material, and time) but varied in the abundance of deciduous shrubs (Jenny, 1994). The sites represent a natural gradient of increasing shrub abundance because the same species of deciduous shrubs (Betula nana, and Salix pulchra) are found at all three sites (except S. richardsonii, which is found only at the medium shrub site); however, their percent cover increases from 15 to 94 %. Our sites are within 1 km of each other, and have similar parent material, and time since last glaciation (Itkillik I, deglaciated ca. 60 000 yr), and regional climate, although microclimates vary across sites due to differences in slope and aspect. The low shrub site is located on top of gently rolling hills, while the medium and high shrub sites are located in depressions along water tracks of ephemeral streams fed by spring snowmelt. Our low shrub abundance site is located in moist acidic tussock tundra where the vegetation consists of approximately equal biomass of graminoids (Eriophorum vaginatum and Carex bigelowii), dwarf deciduous shrubs (B. nana, Vaccinium uliginosum, and S. pulchra), evergreen shrubs (Ledum palustre ssp. decumbens and V. vitis-idea), and mosses (Hylocomium splendens, Aulacomnium turgidum, Dicranum spp., and Sphagnum spp.) (Shaver and Chapin, 1991). In our medium shrub abundance site, vegetation consists of graminoids (primarily C. bigelowii), deciduous shrubs (B. nana, V. uliginosum, S. pulchra and S. richardsonii), and mosses (H. splendens and Dicranum spp.). Our high shrub abundance site has predominantly deciduous shrubs (B. nana, S. pulchra, and some Potentilla fruticosa) with some evergreen or wintergreen shrubs (V. vitis-idaea and Linnaea borealis), forbs (Polygonum bistorta, Petasites frigidus, Stellaria longipes, Valeriana capitata, and Artemisia alaskana), graminoids (Poa arctica, C. bigelowii, and Calamagrostis canadensis), and mosses (Sphagnum spp. and H. splendens). Snow Manipulation: To manipulate snow depth, snow fences (1.5 m high and 62 m long) were set up in the fall of 2005 at the low and medium sites to manipulate snow depth. For the high site, the patchy nature of the shrub stands made it necessary to set up two separate snow fences (1.5 m high and 32 m long) in patches with similar shrub composition and density. Our purpose for adding snow was to simulate the amount of snow that might be trapped by deciduous shrubs; therefore, the height of the snow fences was selected to match the maximum shrub height within the region. Fences were oriented E-W, and snow drifts accumulated on the northern side of the fences. Two treatments (control=ambient snow and drift=manipulated snow) were set up at each site. The drift plots were set up 4 m from the fence on the northern side of the fence, because this was the zone of maximum snow accumulation. At the low and medium sites, the control plots were set up on the southern (non-drift) side of the fence, 10 m from the fence at the low site, and 7 m from the fence at the medium site. These buffer zones were left to prevent the control from being exposed to snow trapped by the fence. At the high shrub sites, control plots were located in line with one of the fences, beginning 5 m from its end, and in 3 discontinuous blocks of tall shrubs to the south (control side) of the fence, beginning approximately 15 m from the fence. This arrangement was chosen because the cover of tall shrubs was discontinuous on the southern (control) side of the fences. For all sites, plots on the drift side of the fences were located in the zone of maximum snow accumulation, which was relatively uniform. Within each treatment, 18 2 by 10 m plots, with 1 m buffer strips between, were established. For this study, six plots per treatment (n=6) were randomly assigned to measure N mineralization and nitrification. Remaining plots were used for additional experiments. Soil temperature: Soil temperature, at 5 cm within the organic layer, was measured continuously (1-3 h intervals) from June 2006-June 2007 in each study plot (n= 3-4) by using Ibutton temperature data loggers (IButtonLink, LLC, East Troy, WI). Weekly mean soil temperatures were calculated from mid-June 2006 through mid-May 2007 for all treatments and sites. Annual soil temperatures were calculated for each site and treatment and included 336 days of measurements. Net N-mineralization: We used the in situ soil incubation method (Di Stefano and Gholz 1986, Hart and Firestone 1989) to assess (1) site differences in net N mineralization and nitrification, (2) snow effects on net N mineralization and nitrification, and (3) SOM versus microclimate effects on net N mineralization and nitrification. To determine N availability across our sites, we measured net N mineralization in the unmanipulated control plots (n=6) at each site (N=18). To test the effects of snow on N availability, soil cores were removed from the control plots at each site and incubated in the snow addition plots (n=6) in each site (N=18). To assess the relative importance of SOM quality and site microclimate on net N mineralization, soil cores were removed from the control plots (n=6) at each site (N=18) and either replaced for in situ incubation or reciprocally transplanted to the control side at each of the other sites. In each replicate of incubation experiment, four soil cores were removed from the top 10 cm in either June or September of 2006 for each layer sampled. Organic soils were sampled with a 5 cm diameter metal corer; new frost boils and Eriophorum vaginatum tussocks were avoided. One core (initial) was removed from the ground, chilled, and processed (within 48 h of sampling) for pools of inorganic N (N-NH4+ and N-NO3-), dissolved organic N (DON), chloroform-fumigated microbial biomass N (MB-N), bulk soil percent C and N, and soil moisture. The other three cores (final) were placed in a 12 cm long and 5 cm diameter PVC tube and capped at the top with one resin bag, and at the bottom with two resin bags. Resin bags were made of nylon that was soaked in 1.2M HCl for 2 h before filling with ion exchange resins. Bags contained 17 g fresh weight (49.4% moisture, 8.28 g oven-dry equivalent) of mixed-bed ion exchange resins (IONAC® NM-60 H+/OH- form, type I beads 16-50 mesh; J. T. Baker, Phillipsburg, New Jersey, USA). One core was then returned to its original hole in the control plot, one core was transplanted to a randomly assigned snow addition plot within the same site for incubation, while the other two remaining cores were each transplanted to a randomly assigned control plot from one of the other two sites for incubation. By doing this, we held the substrate constant but altered the environment of the incubation. All final cores were incubated for 74 days in the summer (mid June 2006-Sept 2006) and 280 days in the winter (Sept 2006-mid June 2007) to look at seasonal affects on N availability. At the end of the incubation periods, soil cores were removed and the soil was processed (within 48 hours of sampling) for pools of N-NH4+ and N-NO3-, DON, MB-N, bulk soil percent C and N, and soil moisture in exactly the same way as the initial core. Resin bags were removed from cores and frozen until processing (see below). Net N mineralization was calculated as the difference between the DIN (NH4+ and NO3-) in the initial soil core and the DIN in the final soil core plus the DIN accumulated on the middle resin bag. Net N nitrification was calculated as the difference between the nitrate in the initial soil core and the nitrate in the final soil core plus the nitrate accumulated on the middle resin bag. The percent of mineralized N that was nitrified was calculated by dividing the N nitrified by the amount of N that was mineralized and multiplying by 100. Nutrient pool sizes and annual net N mineralization were calculated using the soil bulk density obtained from soil harvest conducted in 2007. Prior to analysis, soils were homogenized by hand and the >2 mm diameter fraction (e.g., roots, rhizomes, course woody debris, and rocks) was removed. Soil water content was calculated by subtracting the dry weight of the soil (60 °C for 48 h) from the wet weight of the soil and then dividing by the dry weight of the soil. To determine bulk soil percent C and N, a subsample of <2mm soil fraction was dried at 60º C for 48 h, ground to a fine powder on a Wiley-mill with a #40 mesh screen, and then analyzed using an ECS 4010 elemental analyzer (Costech Analytical, Valencia, California, USA). Pools of dissolved inorganic N (N-NH4+ and N-NO3-) were measured by extracting 10 g of fresh soil with 50 ml of 0.5 M K2SO4. The soil slurry was agitated on a shaker table for 2 h, allowed to sit overnight in a cooler, and then vacuum filtered through a Whatman GF/A filter. Filtrate was frozen until analyzed colorimetrically, on segmented flow autoanalyzer (Astoria analyzer, Astoria-Pacific, Inc, Clackamas, Oregon, USA). Dissolved organic N (DON) was measured on a subsample of the K2SO4 extract that was digested with a persulfate oxidation digestion procedure (Sollins et al., 1999) prior to colorimetric analysis. Because this digestion procedure converts all forms of N to NO3-, DON was calculated by subtracting the DIN measured previously from the total N that was determined in the digestion procedure. Microbial biomass N was determined using the chloroform fumigation method. Ten grams of fresh soil was incubated with 100 ml of pentene stabilized chloroform in a glass dessicator for 24 h. Post incubation, soils were extracted with 0.5 M K2SO4 exactly the same way as for DIN. Fumigated extracts were digested using the same persulfate oxidation procedure used for DON analysis. Nitrate was then measured colorimetrically. Chloroform labile-N was calculated by subtracting the DON and DIN concentrations from the initial, un-fumigated sample from the total N that was extracted from the post-fumigated sample. After incubation, resin bags were rinsed with deionized water to remove soil and then extracted with 50 ml of 2N KCl. Resins and KCl were agitated for 1 h and then filtered through a pre-leached Whatman #1 filter. Filtrate was immediately frozen. At time of analysis, extracts were thawed and measured for N-NH4+ and N-NO3- colorimetrically. Data has been published in DeMarco et al. 2014. Effects of arctic shrub expansion on biophysical versus biogeochemical drivers of litter decomposition. Ecology In press. See Publication for further explanation of methods and references.
2006-2007_JD_SnowShrub_NetNmineralization_csv Net nitrogen mineralization from shrub gradient and snow manipulations, near Toolik field station, collect in the summer of 2006 and winter of 2006-2007 2006-2007_JD_SnowShrub_NetNmineralization.csv 26433 7a3005971f6cccfcdf43b36bd2c68315 04c5370f33102cd1a6ea0d6ff633ff1cc14e205b 1 0 \r\n column , " https://arc-lter.ecosystems.mbl.edu/sites/default/files/data/terrestrial/2006-2007_JD_SnowShrub_NetNmineralization.csv Vegetation type Vegetation type there are three vegetation types that vary in their shrub abundance: Low=low shrub site; Med=medium shrub site; High=high shrub site string there are three vegetation types that vary in their shrub abundance: Low=low shrub site; Med=medium shrub site; High=high shrub site Treatment Treatment there are two treatments of snow levels: C=ambient snow cover; S=snow addition string there are two treatments of snow levels: C=ambient snow cover; S=snow addition Plot Plot within each site and each treatment there are six 10 x 10 m plots string within each site and each treatment there are six 10 x 10 m plots Season collected Season collected season in which N-mineralization and N-nitrification was measured: summer 2006 = cores incubated from x to z; winter 2006-2007 cores incubated froom x to z string season in which N-mineralization and N-nitrification was measured: summer 2006 = cores incubated from x to z; winter 2006-2007 cores incubated froom x to z Soil type Soil type soil was designated as organic or mineral string soil was designated as organic or mineral Incubation location Incubation location vegetation type and treatment where in situ net N-mineralization core was incubated string vegetation type and treatment where in situ net N-mineralization core was incubated Time point Time point time point of core: initial = first core removed prior to incubation; final = core incubated over that season string time point of core: initial = first core removed prior to incubation; final = core incubated over that season Days incubated Days incubated total number of days cores was incuabted in the field number real bulk density bulk density this was calculated by dividing the 60C dried post homogenized bulk soil weight by the core volume for the initial soil core only gramPerCentimeterCubed real -999 not measured Bulk soil % N initial Bulk soil % N initial the concentration of organic N measured from bulk soi prior to in situ incubation for Net N-min and N-Nit percent real -999 not measured Bulk soil % C initial Bulk soil % C initial the concentration of total C measured from bulk soi prior to in situ incubation for Net N-min and N-Nit percent real -999 not measured Initial ammomium concentration Initial ammomium concentration the concentration of total ammonium measured from the initial soil core microgramPerGram real -999 not measured Initial nitrate concenctration Initial nitrate concenctration the concentration of total nitrate measured from the initial soil core microgramPerGram real -999 not measured Net N-mineralization concentration Net N-mineralization concentration the net accumulation of ammonium in the soil incubated plus the net accumulation of the resin bag immediately below the incubated soil core microgramPerGram real -999 not measured Net N-nitrification concentration Net N-nitrification concentration the net accumulation of nitrate in the soil incubated plus the net accumulation of the resin bag immediately below the incubated soil core (microgramN-NO3-Per Gram Ovendried soil PerDay) microgramPerGramPerDay real -999 not measured 259 2006-2007_JD_SnowShrub_NetNmineralization_excel Excel file with metadata and data sheets. Net nitrogen mineralization from shrub gradient and snow manipulations, near Toolik field station, collect in the summer of 2006 and winter of 2006-2007 2006-2007_JD_SnowShrub_NetNmineralization.xls 480768 a77b09a65b0ff923b4ed95e3e387ebe4 3192118f5e77ce8acaa4e5d39fa983f0686c99c2 application/vnd.ms-excel https://arc-lter.ecosystems.mbl.edu/sites/default/files/data/terrestrial/2006-2007_JD_SnowShrub_NetNmineralization.xls document
grams per cubic centimeter ratio of two quantities as percent composition (1:100) micrograms per gram