E002 - Long-Term Nitrogen Addition to Disturbed Vegetation
Introduction
Established at the same time in 1982, Experiment 002 is a nitrogen addition experiment whose initial design was almost identical to Experiment 001. Like Experiment 001, and often in connection with it, Experiment 002 has been used to examine the effects of low-level nitrogen addition on nitrogen-limited grassland ecosystems. Unlike Experiment 001, however, the native vegetation in Experiment 002 was disturbed via thorough agricultural disking prior to the start of treatments. Also, the Experiment 002 plots were established in only three locations, all of which were successional grassland fields (54 plots each). In each field, nine treatments are imposed on sets of replicate plots (54 plots per field). Two of the treatments are controls, neither of which receives ammonium nitrate fertilization, but one of which receives other nutrients (P, K, Ca, Mg and trace metals). The seven remaining treatments add ammonium nitrate at varying rates as well as the other nutrients. Plots have been sampled for above ground biomass (sorted by species) annually through 2004, and once subsequently in 2008. Plots are sampled intermittently for soil chemistry (NH4, NO3, Ca, Mg, P and K), belowground biomass, light penetration, and small mammal densities.In 1986, aluminum flashing was buried between the individual plots to prevent plants from spreading by vegetative reproduction. Initially, the plot grids were enclosed by fencing to exclude large mammalian herbivores, however in 2004 this
was removed. Gophers are trapped and removed. In 1992, two modifications were made to the Experiment 002 treatment regime. In two of the three fields, cessation treatments were initiated with all nutrient addition being discont
inued for half of the replicates. In the third field, fertilization treatments are ongoing, but half of the replicates are burned annually.
Key Results
Within a decade after establishment and after undergoing rapid successional changes, plots that shared the same treatment in Experiment 001 and Experiment 002 had converged in composition, plant abundances (Fig 1; Inouye and Tilman 1995). While Experiment 002 plots were initially dominated by annual species, often not of native origin, these were quickly replaced by native perennials.
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![]() | Figure 1 Graphs of Percent Similarity (PS) vs. time for convergence within fields. Each set of eight graphs presents data comparing disturbed and undisturbed grids in one field, separated by nitrogen treatment (fertilization rates increase alphabetically). Small circular points represent individual comparisons of two plots of the same treatment, one plot on the undisturbed grid and one plot on the disturbed grid. Each graph contains36 such points for each year (six disturbed plots x six undisturbed plots). Stars indicate average PS for each year. For regression analyses, transormation were done on average PS (arcsine square-root) and (year - 1981). Thirteen years after nitrogen cessation treatments began, a period comparable to the 10 years of elevated nitrogen addition, relative plant species numbers returned to control levels (Fig 2, Clark and Tilman,2008). Plant species abundances, however, were not seen to recover. |
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Figure. 2 Recovery of relative species number after cessation of nitrogen addition. Relative species number of all plots that continued to receive nitrogen (+N) and of those plots for which nitrogen addition ceased from 1991 and on (-N) is shown as the average across all nitrogen addition levels each year. There were no significant interactions between the rate of nitrogen addition and either year or the cessation treatment. (Clark and Tilman 2008) |
![]() | Figure 3. Proportional species loss versus nitrogen input rate for (a) 2002-2004 and (b) 1983-1985. Plot averages for each field over the three year-period fitted to a logarithmic curve excluding controls (95% confidence curves included). P values correspond to the significance of the nitrogen input term (N input = experimental N addition + atmospheric N deposition) in a model of the proportional loss of species regressed on the natural logarithm of the nitrogen input rate, Field, and their interaction. Dashed lines correspond to linear interpolation between the mean effect at the highest nitrogen addition rate and controls. (Clark and Tilman 2008) |
Datasets for e002: Long-Term Nitrogen Deposition During Grassland Succession
Dataset ID | Title | Range of Years (# years with data) |
---|---|---|
nle002 | Litter carbon and nitrogen | 2009-2009 (1 year) |
lpe002 | Percent light penetration | 1982-1990 (9 years) |
ple002 | Plant aboveground biomass data | 1982-2019 (29 years) |
rcne002 | Root Carbon and Nitrogen | 2009-2009 (1 year) |
rbe002 | Root biomass data | 1988-2013 (6 years) |
mse002 | Small mammal abundance | 1982-1985 (4 years) |
cae002 | Soil Calcium | 1982-1982 (1 year) |
care002 | Soil carbon | 1982-2011 (5 years) |
mge002 | Soil magnesium | 1982-1982 (1 year) |
nohe002 | Soil nitrate and ammonium | 1985-2013 (7 years) |
ne002 | Soil nitrogen | 1982-2011 (6 years) |
phe002 | Soil pH | 1982-1990 (5 years) |
pe002 | Soil phosphorous | 1982-1982 (1 year) |
ke002 | Soil potassium | 1982-1982 (1 year) |
Selected Recent Publications
Yue, K., Y. Peng, D. A. Fornara, K. Van Meerbeek, L. Vesterdal, W. Yang, C. Peng, B. Tan, W. Zhou, Z. Xu, X. Ni, L. Zhang, F. Wu, and J.-C. Svenning. 2019. Responses of nitrogen concentrations and pools to multiple environmental change drivers: A meta-analysis across terrestrial ecosystems. Global Ecology and Biogeography. DOI 10.1111/geb.12884 2019 e002 e141
Ratajczak, Z., D`Odorico, P., Collins, S. L., Bestelmeyer, B. T., Isbell, F. I., and Nippert, J. B. (2017). The interactive effects of press/pulse intensity and duration on regime shifts at multiple scales. Ecological Monographs, accepted article. doi:10.1002/ecm.1249 2017 e001 e002 e097
Wilcox, K. R., A. T. Tredennick, S. E. Koerner, E. Grman, L. M. Hallett, M. L. Avolio, K. J. La Pierre, G. R. Houseman, F. Isbell, D. S. Johnson, J. M. Alatalo, A. H. Baldwin, E. W. Bork, E. H. Boughton, W. D. Bowman, A. J. Britton, J. F. Cahill, S. L. Collins, G. Du, A. Eskelinen, L. Gough, A. Jentsch, C. Kern, K. Klanderud, A. K. Knapp, J. Kreyling, Y. Luo, J. R. McLaren, P. Megonigal, V. Onipchenko, J. Prevey, J. N. Price, C. H. Robinson, O. E. Sala, M. D. Smith, N. A. Soudzilovskaia, L. Souza, D. Tilman, S. R. White, Z. Xu, L. Yahdjian, Q. Yu, P. Zhang and Y. Zhang (2017). "Asynchrony among local communities stabilises ecosystem function of metacommunities." Ecology Letters 20(12): 1534-1545. DOI 10.1111/ele.12861 2017 e001 e002
Hautier, Y.; Tilman, D.; Isbell, F.; Seabloom, E. W.; Borer, E. T.; Reich, P. B.; Anthropogenic environmental changes affect ecosystem stability via biodiversity. Science, 2015, 348, 6232, 336-340 DOI:10.1126/science.aaa1788 2015 [Full Text] e001 e002 e003 e012 e098 e120 e141 e245 e247 e248
Isbell, F.; Tilman, D.; Polasky, S.; Binder, S.; Hawthorne, P.; Low biodiversity state persists two decades after cessation of nutrient enrichment; Ecology Letters (2013) 16: 454?460 DOI: 10.1111/ele.12066 2013 [Full Text] e001 e002 e120 e141
Isbell, Forest; Reich, Peter B.; Tilman, David; Hobbie, Sarah E.; Polasky, Stephen; Binder, Seth. Nutrient enrichment, biodiversity loss, and consequent declines in ecosystem productivity. Proceedings of the National Academy of Sciences of the United States of America. 2013 110 (29):11911-11916. 2013 [Full Text] e001 e002. e120 e141
Fornara, Dario A.; Tilman, David; Soil carbon sequestration in prairie grasslands increased by chronic nitrogen addition; Ecology, 2012, 93, 9, 2030 - 2036 2012 [Full Text] e001 e002
Tilman, D.; Reich, P. B.; Isbell, F.; Biodiversity impacts ecosystem productivity as much as resources, disturbance, or herbivory; Proceedings of the National Academy of Sciences; 2012; 109, 26, 10394-10397 2012 [Full Text] e001 e002 e003 e004 e012 e062 e098 e120 e141 e172