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The re-use of scientific data has the potential to greatly increase communication, collaboration and synthesis within and among disciplines, and thus is fostered, supported and encouraged. Permission to use this dataset is granted to the Data User free of charge subject to the following terms:

1) Acceptable use. Use of the dataset will be restricted to academic, research, educational, government, recreational, or other not-for-profit professional purposes. The Data User is permitted to produce and distribute derived works from this dataset provided that they are released under the same license terms as those accompanying this Data Set. Any other uses for the Data Set or its derived products will require explicit permission from the dataset owner.
2 ) Redistribution. The data are provided for use by the Data User. The metadata and this license must accompany all copies made and be available to all users of this Data Set. The Data User will not redistribute the original Data Set beyond this collaboration sphere.
3 ) Citation. It is considered a matter of professional ethics to acknowledge the work of other scientists. Thus, the Data User will properly cite the Data Set in any publications or in the metadata of any derived data products that were produced using the Data Set. Citation should take the following general form: Creator, Year of Data Publication, Title of Dataset, Publisher, Dataset identifier. For example:

Shaver, G. 1989. Above ground biomass in acidic tussock tundra experimental site, 1989, Arctic LTER, Toolik, Alaska. Arctic LTER, Marine Biological Lab, Woods Hole, Ma 02543. 1989gsttbm http://ecosystems.mbl.edu/arc/terrest/biomass/index.shtml 

4 ) Acknowledgement. The Data User should acknowledge any institutional support or specific funding awards referenced in the metadata accompanying this dataset in any publications where the Data Set contributed significantly to its content. Acknowledgements should identify the supporting party, the party that received the support, and any identifying information such as grant numbers. For example:

Data sets were provided by the Arctic LTER. This material is based upon work supported by the National Science Foundation under Grants #DEB-981022, 9211775, 8702328; #OPP-9911278, 9911681, 9732281, 9615411, 9615563, 9615942, 9615949, 9400722, 9415411, 9318529; #BSR 9019055, 8806635, 8507493.

5 ) Notification. The Data User will notify the Data Set Contact when any derivative work or publication based on or derived from the Data Set is distributed. The Data User will provide the data contact with two reprints of any publications resulting from use of the Data Set and will provide copies, or on-line access to, any derived digital products. Notification will include an explanation of how the Data Set was used to produce the derived work.
6 ) Collaboration. The Data Set has been released in the spirit of open scientific collaboration. Data Users are thus strongly encouraged to consider consultation, collaboration and/or co-authorship with the Data Set Creator.

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While substantial efforts are made to ensure the accuracy of data and documentation contained in this Data Set, complete accuracy of data and metadata cannot be guaranteed. All data and metadata are made available "as is". The Data User holds all parties involved in the production or distribution of the Data Set harmless for damages resulting from its use or interpretation.

Dataset URLs:METADATA: HTML, Rich Text, XML(EML compliant)
DATA: Comma Delimited, Excel file with Metadata and data, Dataset via LTER Data Poral
Dataset ID:2006-2007_JD_SnowShrub_Litter_Decomp.02
Dataset Title:Mass, C, N, and lignin from litter decomposed across a shrub gradient and with snow manipulations near Toolik Field Station between 2003 and 2009.
Investigator 1: 
First Name:Jennie
Last Name:DeMarco
Organization:New Mexico State University
Address line 2:Department of Biology
Address line 3:MSC 3AF
City:Las Cruces
State:NM
Zip Code:88012
Country:USA
Investigator 2: 
First Name:Michelle
Last Name:Mack
Organization:University of Florida
Address line 2:Department of Biology
Address line 3:P.O. Box 118525
City:Gainesville
State:FL
Zip Code:32611
Country:USA
Investigator 3: 
First Name:M. Syndonia
Last Name:Bret-Harte
Organization:University of Alaska, Fairbanks
Address line 2:Institute of Arctic Biology
Address line 3:Irving I room 311
City:Fairbanks
State:AK
Zip Code:99775-7000
Country:USA
Associate Investigators:
Keywords:snow manipulation, shrub tundra, soil temperature, litter decomposition, Toolik Field Station, common garden, snow manipulation
Abstract: 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.
For questions about the Metadata and data contact the Investigators.
For information about this web site contact:
Arctic LTER Information Manager
The Ecosystems Center
Marine Biological Lab
7 MBL St
Woods Hole, MA 02543
Phone (508) 289 7496
Email: arc_im@mbl.edu
Online URL: http://ecosystems.mbl.edu/ARC/
DATA FILE INFORMATION:
Data File URL http://metacat.lternet.edu/das/dataAccessServlet?docid=knb-lter-arc.10499&urlTail=terrest/bulk/data/2006-2007_JD_SnowShrub_Litter_Decomp.csv
Data File Name 2006-2007_JD_SnowShrub_Litter_Decomp
Beginning Date 6/1/2003
End Date 7/1/2009
Number of Data Records 1071
Other Files to Reference 2006-2007_JD_SnowShrub_NetNmineralization.xls
Availability Status data available
Quality Control Information all data has been checked for quality
Maintenance Description 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.
Log of Changes: Version 1: Data entered and checked by J.DeMarco, metadata verified and uploaded (JD-Dec 2013)
Version 2: Checked keywords against the LTER network preferred list and replaced non-preferred terms. Jim L 27Jan14
 
RESEARCH LOCATION:                  
Location Name Low shrub tundra-ambient snow Low shrub tundra-snow addition Medium shrub tundra-ambient snow Medium shrub tundra-snow addition High shrub tundra-ambient snow High shrub tundra-snow addition Common garden site Select Site or enter New One  
Geographic Description west of Toolik Field Station and south of Toolik Lake west of Toolik Field Station and south of Toolik Lake east of Toolik Field Station and southeast of Toolik Lake east of Toolik Field Station and southeast of Toolik Lake east of Toolik Field Station and southeast of Toolik Lake east of Toolik Field Station and southeast of Toolik Lake west of Toolik Field Station and south of Toolik Lake Enter Description  
Location Bounding Box                  
West Bounding Coordinate                  
East Bounding Coordinate                  
North Bounding Coordinate                  
South Bounding Coordinate                  
OR if single point location                  
Latitude 68.633 68.633 68.633 68.633 68.633 68.633 68.633 In Decimal Degrees  
Longitude -149.633 -149.633 -149.633 -149.633 -149.633 -149.633 -149.633 In Decimal Degrees  
Elevation 764 m 765 m 766 m 767 m 768 m 769 m 764 m In Meters  
Link to Google Map View on Google Map View on Google Map View on Google Map View on Google Map View on Google Map View on Google Map View on Google Map    
                   
 
TAXONOMIC COVERAGE:
Organisms studied Carex bigelowii; Eriophorum vaginatum; Alnus viridis; Betula nana; Betula neoalaskana; Betula papyrifera; Rubus chamaemorus; Salix pulchra; Vaccinium uliginosum; Ledum palustre; Vaccinium vitis-idaea; Aulacomnium turgidum; Hylocomium splendens; Sphagnum spp.; Alnus crispa, Salix glauca
 
Methods: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.

Snow addition effects on litter decomposition (common substrate experiment):
To directly test the effect of microclimate and snow addition on litter decomposition rates we incubated the senesced leaves from a common substrate, B. neoalaskana (Sarg.), in the ambient and snow manipulated plots across all three sites. Senesced leaves were collected from trees growing near Fairbanks, AK. Leaves were still attached to the trees but the petiole had already started to abscise. This common substrate was used because the large leaf size and relative abundance allowed us to collect enough material for our study. Leaves were air dried, well mixed, and then subsampled for litter bags. One gram of leaves was sewn into 2 mm mesh bags, 8 x 8-cm in size. Litter bags were incubated beneath the live moss and litter layer starting in early June of 2006. The moss and litter in this system are well mixed so bags were inserted in this layer. Four identical bags were strung together for four separate annual harvests. Bags were placed in six treatment plots in each site (n=6), with three sub-replicates within each plot. Bags were removed in July of 2007, 2008, and 2009 and were kept frozen until they could be processed.
At time of processing, bags were thawed and then gently rinsed with deionized (DI) water to remove soil and loose litter attached to the outside of the bag. All original leaf litter was removed, dried at 45° C for a minimum of 48 hours and weighed. To determine the percent C and N of the litter, samples were 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). Percent of initial mass remaining was calculated by dividing the incubated mass by the initial mass and multiplying by 100. Percent of initial C (ICR) and initial N remaining (INR) was calculated by the following equation:
??????=((??_(1 ????????) × ??_(1 ????????????) ))/((??_(0 ????????) × ??_(0 ????????????)))× 100


Initial litter quality effects on litter decomposition (common garden experiment):
To compare differences in litter decomposition rates among species, we incubated senesced leaf litter from 13 species and stem litter from four shrub species collected across seven sites located in the arctic foothills region on the North Slope of Brooks Range, Alaska, USA. Three of the sites were the control plots at the low, medium, and high shrub sites. Four sites were dominated by alder shrubs (Alnus crispa)-two near the Sagavanirktok River and two along the Dalton Highway ~ 32 km north of Toolik Field Station. Alders are one of the deciduous shrubs that have been documented as expanding in many arctic regions so we chose to include litter from these shrubs as well. All litter was collected and processed using the same method as described previously in the common substrate experiment except that only 1.6 mm mesh bags, 4 x 8-cm in area, were used and leaf samples were replicated six times while stem litter was replicated three times. Litter bags were installed in early June of 2006 and replicate bags were removed in July of 2007, 2008, and 2009.
In addition, we incubated leaf litter collected from seven different species growing in three long-term fertilization experiments to better understand the influence of litter quality on litter decomposition rates. All three sites, “Historic” (Chapin et al. 1995, Mack et al. 2004), “LTER” (Bret-Harte et al. 2001), and “Species Removal” (Bret-Harte et al. 2008) are located in moist acidic tundra and were fertilized annually with both 10 g of N and 5 g of P m-2 year-1 for 20, 14, and five years, respectively. Litter from these bags were installed in the field in July of 2003, removed in July of 2004, 2005, 2007, and 2008, and processed as described above.
Calculations. The exponential decay constant, k, was determined by assuming a single exponential decay model (Olson 1963): Mt = Moe-kt, where Mt = litter mass at time t, and MO = initial mass. The slope of the regression of proportion of initial mass remaining against time was used to determine decay constant for each substrate at each site.
Initial Litter Quality. A subsample of each leaf and stem collections was analyzed for percent C, percent N, and C quality to determine the quality of the litter substrates prior to decomposition. Percent C and N was determined on samples that had been ground to a fine powder on a Wiley-mill, with a #40 mesh screen, and then analyzed using an ECS 4010 elemental analyzer. C quality measurements were carried out on an ANKOM fiber analyzer (Ankom Technology, Macedon, N. Y.) and included determination of (1) soluble cell contents (carbohydrates, lipids, pectin, starch, and soluble protein), (2) hemicelluloses plus bound proteins, (3) cellulose, and (4) lignin plus other recalcitrants (Ryan et al. 1990).

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.

REFERENCES:
Bret-Harte, M.S., Mack, M.C., Goldsmith, G.R., Sloan, D.B., DeMarco, J., Shaver, G.R., Ray, P.M., Biesinger, Z., Chapin III, F.S. (2008) Plant functional types do not predict biomass responses to removal and
fertilization in Alaskan tussock tundra. Journal of Ecology, 96:4, 713-726.
Chapin III, F.S., Shaver, G.R., Giblin, A.E., Nadelhoffer, K.J., Laundre, J.A. (1995) Responses of arctic tundra experimental and observed changes in climate. Ecology, 76: 3, 694-711.
Mack, M.C., Schuur, E.A.G., Bret-Harte, M.S., Shaver, G.R., Chapin III, F.S. (2004) Ecosystem carbon storage in arctic tundra reduced by long-term nutrient fertilization. Letters to Nature, 431, 440-443.
Olsen, J.S. (1963) Energy storage and the balance of producers and decomposers in ecological systems. Ecology, 44:2, 322-331.
Ryan, M.G., Melillo, J.M., Ricca, A. (1990) A comparison of methods for determining proximate carbon fractions of forest litter. Canadian Journal of Forest Research, 20:2, 166-171.
Shaver, G.R., Chapin III, F.S. (1991) Production: Biomass relationships and element cycling in contrasting arctic vegetation types. Ecological Monographs, 61:1, 1-31.

Data Table

Variable Name Variable Description Data Type Units DateTime Format Code Information Missing Value Code
Experiment Type of experiment: a common substrate or a common garden: CS=common substrate; CG=common garden text        
Treatment there are two treatments of snow levels for the Common substrate experiment: C=ambient snow cover; S=snow addition The Common garden experiment was fertilized where: C=no treatment; F=fertilized with nitrogen text        
Litter tissue type there are two litter tissue types (leaves and stems) text        
Site of litter collection this is the site were the litter was originally collected text        
Species name of the plant species text        
Plant growth from functional type of plant where DE=deciduous shrub; EV=evergreen shrub; GR=graminoid; MO=moss text        
Site of incubation site and vegetation type of where litter was incubated in the field: Low=low shrub site (moist acidic tundra); Med=medium shrub site (low deciduous shrub tundra); High=high shrub site (tall deciduous shrub tundra) text        
Plot within each site and each treatment there are six 10 x 10 m plots text        
Year collected year litter bags were removed from the field: Note: Common substrate bags installed in June 2006 and removed in June 2007, 2008, 2009; Common garden litter bags installed July 2003 and removed 2004, 2005, 2007, and 2008 text        
Days in the field number of days that litter bags was incubating in the field number number     NA=not measured
IMR percent of initial mass remaining as calculated as IMR=(t1 mass)/(t0 mass) × 100 number percent     NA=not measured
C percent of C in the litter as measured on a elemental analyzer number percent     NA=not measured
N percent of N in the litter as measured on a elemental analyzer number percent     NA=not measured
ICR percent of initial C remaining in the litter calculated as ICR=((t1 mass) × t1 C) ))/((t0 mass) × t0 C)))× 100 number percent     NA=not measured
INR percent of initial N remaining in the litter calculated as INR=((t1 mass) × t1 N) ))/((t0 mass) × t0 N)))× 100 number percent     NA=not measured
NPE non-polar extracts (carbohydrates, lipids, pectin, starch, and soluble proteins) number percent     NA=not measured
WS hemicullulose and bound proteins number percent     NA=not measured
AS cellulose number percent     NA=not measured
Lignin lignin number percent     NA=not measured

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