Methods in brief for each site in the synthetic dataset
At the Arctic LTER site there were 5 experiments conducted in distinct community types, contact Laura Gough for original data. 10 g/m2 N added as NH4-NO3, experiment began 1985, relative abundances of plant species were calculated from percent cover measures based on 1m2 plots, the data here are from 1998. Biomass data are also available for 4 of the 5 experiments.
At the Carpinteria California coastal marsh there were 6 experiments conducted in distinct community types, contact Steven Pennings for original data. 420 g/m2 N was added in the first year (1999) and 820 g/m2 was added in subsequent years in the form of pellets, 20:10:5 NPK, derived from ureaformaldehyde and ammoniated phosphate. Relative abundance was calculated from percent cover measured on 0.25 m2 plots. The data here are from 1999-2005. Biomass data were not collected.
At the Cedar Creek LTER experiments were conducted in old-fields of different ages, 2 experimental fields are included in this dataset, contact Chris Clark for original data. 9.52 g/m2 added as NH4-NO3, experiment began 1982, relative abundance was calculated from biomass harvests from 0.3m2 plots. The data here are from 1999-2001.
At the Georgia Coastal Ecosystems LTER 5 experiments were conducted in distinct community types along a tidal gradient, contact Steven Pennings for original data. 1560 g/m2 N was added as pelletized 29:3:4 NPK, experiment lasted two years 1996 and 1997, only 1997 data is included here. Relative abundance was measured with a biomass harvest on 0.25 m2 plots.
The Jasper Ridge Global Change Experiment is located near Stanford University in California. This is a factorial experiment with 4 treatments - the N addition and water addition treatments are included in this dataset and defined as 2 experiments. Additional warming and elevated CO2 treatments are not included - contact Elsa Cleland for original data. 7 g/m2 N was added as calcium nitrate, experiment began in 1998, relative abundance was calculated from pin counts performed on a 0.5 m2 plot. The data here are from 1998-2002. Biomass data are also available.
At the Kellogg Biological Station LTER 2 experiments were conducted in oldfields that are annually tilled versus un-tilled, contact Kay Gross for original data. 12.3 g N/m2 added as NH4-NO3, experiment began in 1989 and is ongoing, the data here are from 1989-2001. Relative abundance is based on a biomass harvest, plot size varied over time 1989 = 0.2 m2, 1990-1991 = 0.3 m2, 1992-2001 = 1 m2.
This synthetic dataset contains 8 experiments from the Konza Prairie LTER. 4 are from a factorial burning, mowing and fertilization experiment where additional P treatments are coded as blocks (none added block = 1, P added block=2). The other 4 experiments are from a factorial N x water x location experiment (uplands versus lowlands). Contact Scott Collins for additional data.
At the Niwot Ridge LTER, 2 experiments were conducted in dry versus wet meadow communities, contact William Bowman for original data. N was added as liquid urea, the amount varied among years, 25 g/m2 was added in 1990, none in 1991, 10 g/m2 1992-2000. Relative abundance calculated based on pint hits in 1m2 plots using a point frame. Note, blocking indicates P addition (1=none, 2=P added). Data for the wet meadow are from 1990-1996, data for the dry meadow are from 1990-2000 with 1997 and 1999 missing. Biomass data were also collected.
At the Sevilletta LTER, 1 experiment was conducted that included a P addition, this is indicated with a blocking factor as described in the column heading, contact Scott Collins for original data. N was added as
Relative abundance was calculated based on percent cover measures in a 1m2 plot. Experiment began in
Data here are from 2004 and early 2005, biomass was not collected.
At the Shortgrass Steppe LTER, 2 experiments (actually with and without water addition), contact Bill Lauenroth for original data. 6 g/m2 N was added yearly 1997-2000, 3 g/m2/yr 2001-present, in the form of NH4-NO3. Relative abundance is based on percent cover measured in 0.1m2 plots. Data here is from 2000, biomass data were also collected.