Title:Effects ofdifferential grazing on decomposition rate and nitrogen availability in aproductive mountain grassland

Authors: María Victoria Vaieretti 1*, Ana María Cingolani 1,2, Natalia Pérez Harguindeguy 1,2 and Marcelo Cabido 1,2

Running title: Decomposition and nitrogen availability in grassland patches maintained by grazing

1Instituto Multidisciplinario de Biología Vegetal, (CONICET-Universidad Nacional de Córdoba). CC 495, (5000) Córdoba, Argentina.

2Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Córdoba, Av. Vélez Sarsfield 299, (5000) Córdoba, Argentina.

*Corresponding author e-mail:

Tel.: 54 351 433 1097

Fax.: 54 351 433 1056

Online Resource 1. Mean cover (%) of the most abundant species, and the chemical and physical properties of soils(mean ± SE) for each vegetation patch type. Soil water content was measured from January to July 2007. We calculate the average in soil water content, for each patch type, for two periods: January to March 2007, and January to July according to the decomposition experiment incubations.TG = tussock grasslands

Patch type
Lawns / Open TG / Closed TG
Most abundant species
Poa stuckertii(Hack.) Parodi / 0.3 / 8 / 71
Deyeuxia hieronymi (Hack.) Türpe / 2.4 / 50 / 21.3
Eringyum agavifolium Griseb. / 6.4 / 10 / 3.8

Lachemilla pinnata Ruiz & Pav.

/ 37.7 / 9 / 1.6
Carex fusculad' Urv. / 14.1 / 5 / 0.04
Eleocharis albibracteataNees & Meyen ex Kunth / 14.3 / 0 / 0
Juncus uruguensisGriseb. / 7.9 / 0.6 / 0
Muhlenbergia peruviana(P Beauv.) Steud. / 6.4 / 0.2 / 0.02
Festuca circinataGriseb. / 5.8 / 0.01 / 0
Soil characteristics
Organic C (%) / 6.1 (0.52) / 5.9 (0.47) / 5.8 (0.42)
Total N (%) / 0.5 (0.05) / 0.5 (0.04) / 0.5 (0.04)
P (ppm) / 1.8 (0.65) / 2.1 (0.16) / 2 (0.25)
pH / 4.9 (0.10) / 4.9 (0.09) / 5 (0.07)
Clay (%) / 13.9 (1.39) / 14.6 (0.66) / 16.4 (1.26)
Silt (%) / 32.2 (1.45) / 32.9 (1.10) / 33.3 (1.50)
Sand (%) / 53.9 (2.11) / 52.5 (1.47) / 50.3 (0.82)
Bulk density(g.cm-3) / 0.76 (0.06) / 0.91 (0.06) / 0.84 (0.04)
Soil water content (%) (January-March 2007) / 35 (3.2) / 30.2 (2.1) / 34.2 (1.3)
Soil water content (%) (January-July 2007) / 34.7 (3.1) / 30.4 (2.0) / 34.5 (1.4)

Online Resource 2. Chemical quality and decomposability of the litterbelonging to the each vegetation patch types and faeces. Data of litter chemical parameters and decomposability represent means ± SE, result of averaging 10 samples of the litter collected in September 2006 in each site of the three patch types selected. Data of chemical quality of faeces result of averaging three sub-samples of the one compound samplecollected in September 2006, and data of faeces decomposability result of averaging the values obtained of 10 sub-samples of the same compound sample. TG = tussock grasslands, C:N = carbon:nitrogen; lignin:N = lignin:nitrogen; LCH = lignin+cellulose+hemicellulose. The decomposability of litter and faeces was determined as the percentage of dry weight loss (% DWL) of the substrates, in a common garden experiment, after a period of incubation. 75Decomposability and 198Decomposability = decomposability at 75 and 198 days of incubation, respectively. Different letters indicate significant differences among patch types at p < 0.05 (mixed-effect ANOVA). Data of faeces were not including in this analysis.

Lawn / Open TG / Closed TG / Faeces
C (%) / 45.7±0.27 a / 46±0.48 a / 46.7±0.37 a / 43.3
N (%) / 1.3±0.07 a / 0.9±0.05 b / 1±0.06 b / 1.3
P (%) / 0.06±0.005 a / 0.05±0.003 a / 0.06±0.005 a / 0.16
Lignin (%) / 9.2±0.43 a / 6.9±0.34 b / 8.2±0.45 ab / 14.5
Cellulose (%) / 33.8±0.69 b / 37.5±0.67 a / 39.1±0.48 a / 32.6
Hemicellulose (%) / 22.8±1.17 b / 27.7±0.71 a / 27.3±1 a / 18.3
C:N ratio / 35.7±2.07 b / 50.8±2.75 a / 49.5±3.31 a / 32.8
Lignin:N ratio / 7.1±0.41 b / 7.5±0.24 ab / 8.5±0.35 a / 10.9
LCH / 65.8±0.91 b / 72.1±0.94 a / 74.5±1.02 a / 65.4
75Decomposability (% DWL) / 8.1±0.74 a / 5.4±0.50 b / 4.4±0.61 b / 9.8
198Decomposability (% DWL) / 18±0.89 a / 14.8±0.88 b / 14.5±0.69 b / 21

Online Resource 3. The significant of differences between faeces and litter of each patch type in quality parameters and decomposability was tested with one sample t-tests (because we had only one value of each parameter for faeces). In the table we show the t values for each comparison. * p<0.05; ** p<0.01; ***p<0.001; ns, indicates not significant differences. Values of chemical quality parameters measured and decomposability of the litter belonging to the each vegetation patch types and faecesare shown in Online Resource 1.Note that the litter belonging to open and closed tussock grasslands were significantly different than faeces (p < 0.05) for all quality parameters measured and decomposability. TG = tussock grasslands, C:N = carbon:nitrogen; lignin:N = lignin:nitrogen; LCH = lignin+cellulose+hemicellulose, % DWL = percentage of dry weight loss, 75Decomposability and 198Decomposability = decomposability at 75 and 198 days of incubation, respectively.

Lawn / Open TG / Closed TG
C (%) / 8.7 *** / 5.6 *** / 8.9 ***
N (%) / -0.2 ns / -7.3 *** / -5.5 ***
P (%) / -18.8 *** / -29.2 *** / -19.1 ***
Lignin (%) / -12.1 *** / -22.6 *** / -13.9***
Cellulose (%) / 1.8 ns / 7.3 *** / 13.5 ***
Hemicellulose (%) / 3.8 ** / 13.3 *** / 8.9 ***
C:N ratio / 1.4 ns / 6.5*** / 5.1 ***
Lignin:N ratio / -9.2 *** / -14.4*** / -6.9***
LCH / 0.4 ns / 7.1 *** / 8.9 ***
75Decomposability (% DWL) / -2.2 * / -8.6 *** / -8.9 ***
198Decomposability (% DWL) / -3.5 ** / -7.1 *** / -9.4 ***

Note: Positive t value indicates that litter quality value (of each patch type) was higher than quality value of faeces. Negative t value indicates the opposite.

Online Resource 4.In situ decomposition (% of dry weight loss) of litter and both common plant substrates (Muhlenbergia peruviana and Poa stuckertii) after 198 days of incubation, in the three vegetation patch types. Different letters indicate significant differences (ANOVA, p < 0.05) among patch types for each substrate separately. TG = tussock grasslands.

Online Resource 5.Relationships between in situ litter decomposition (% of dry weight loss) and, A) Muhlenbergia peruviana decomposition, B) Poa stuckertii decompositionafter 198 days of incubation, in the three vegetation patch types.r = Pearson correlation coefficient; p= level of significance of the analysis; TG = tussock grasslands.