Electronic Supplementary Material

Fine root dynamics in relation to nutrients in oligotrophic Bornean rain forest soils

Amy Kochsiek1, Sylvester Tan2, and Sabrina E. Russo1, 3

1 School of Biological Sciences, University of Nebraska, Lincoln, Nebraska, 68588 USA

2 Center for Tropical Forest Science – Arnold Arboretum Asia Program, Harvard University, Cambridge, MA USA 02138

3 Author for correspondence: , School of Biological Sciences – Manter Hall, University of Nebraska, Lincoln, Nebraska, 68588-0118 USA

Table S1. Pairwise correlations between supply rates of nutrients in clay and sandy loam surface soils (n = 13 and 11 plots for clay and sandy loam, respectively) underlying Bornean rainforest. Probabilities and Pearson correlation coefficients are above and below the diagonal, respectively, with statistically significant values in bold typeface.

NH4+ / NO3- / K+ / Ca2+ / Mg2+ / PO43-
NH4+ / - / 0.678 / 0.125 / 0.837 / 0.568 / 0.679
NO3- / -0.09 / - / 0.304 / 0.036 / 0.005 / 0.006
K+ / 0.32 / -0.22 / - / 0.730 / 0.088 / 0.007
Ca2+ / -0.04 / 0.42 / 0.07 / - / < 0.001 / 0.088
Mg2+ / -0.12 / 0.55 / 0.36 / 0.65 / - / 0.930
PO43- / 0.09 / -0.55 / 0.54 / -0.36 / -0.02 / -

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Table S2. Variation in standing biomass, length, and areaof fine roots with nutrient supply rates in surface soils underlying Bornean rainforest. Nutrients were tested in separate linear models for each root parameter with main effects of the nutrient supply rate and soil type (clay or sandy loam). Interactions between soil type (clay versus sandy loam) and each nutrient were never statistically significant. Values of the F-statistic and associated probabilities are given for main effects in each model, with the coefficient of determination (R2) for the model. Values in boldface type highlight statistically significant effects; n = 11 plots per soil type.

Biomass / Length / Area
Main effect / F1,19 / P / R2 / F1,19 / P / R2 / F1,19 / P / R2
NH4+ / 0.001 / 0.973 / 0.22 / 0.185 / 0.672 / 0.00 / 0.475 / 0.499 / 0.02
Soil type / 7.763 / 0.012 / 1.815 / 0.194 / 1.991 / 0.174
NO3- / 4.294 / 0.052 / 0.20 / 0.603 / 0.447 / 0.00 / 1.598 / 0.222 / 0.03
Soil type / 2.841 / 0.108 / 1.381 / 0.254 / 1.095 / 0.308
K+ / 9.299 / 0.007 / 0.35 / 4.837 / 0.040 / 0.15 / 5.039 / 0.037 / 0.17
Soil type / 4.135 / 0.056 / 0.835 / 0.372 / 1.163 / 0.294
Ca2+ / 1.532 / 0.231 / 0.17 / 0.129 / 0.723 / 0.01 / 0.271 / 0.609 / 0.03
Soil type / 4.816 / 0.041 / 2.044 / 0.169 / 2.300 / 0.146
Mg2+ / 0.067 / 0.799 / 0.26 / 0.021 / 0.885 / 0.03 / 0.087 / 0.772 / 0.05
Soil type / 9.383 / 0.006 / 2.686 / 0.118 / 2.982 / 0.100
PO43- / 5.627 / 0.028 / 0.19 / 2.298 / 0.146 / 0.02 / 1.654 / 0.214 / 0.02
Soil type / 1.348 / 0.260 / 0.186 / 0.671 / 0.830 / 0.374

Table S3. Variation in biomass,length, and areagrowth rates of fine roots with nutrient supply rates in surface soils underlying Bornean rainforest. Nutrients were tested in separate linear models for each root parameter with main effects of the nutrient supply rate and soil type (clay or sandy loam). Interactions between soil type (clay versus sandy loam) and each nutrient were never statistically significant. Values of the F-statistic and associated probabilities are given for main effects in each model, with the coefficient of determination (R2) for the model (n = 13 and 11 plots for clay and sandy loam, respectively). Values in boldface type highlight statistically significant effects.

Biomass / Length / Area
Main effect / F1,21 / P / R2 / F1,21 / P / R2 / F1,21 / P / R2
NH4+ / 0.915 / 0.350 / 0.12 / 4.182 / 0.054 / 0.33 / 5.480 / 0.029 / 0.29
Soil type / 4.159 / 0.054 / 9.393 / 0.006 / 6.032 / 0.023
NO3- / 1.152 / 0.295 / 0.12 / 2.941 / 0.101 / 0.32 / 2.486 / 0.130 / 0.24
Soil type / 3.974 / 0.059 / 9.951 / 0.005 / 6.818 / 0.016
K+ / 0.210 / 0.651 / 0.12 / 3.930 / 0.061 / 0.35 / 3.998 / 0.059 / 0.29
Soil type / 4.874 / 0.039 / 10.479 / 0.004 / 7.330 / 0.013
Ca2+ / 1.938 / 0.178 / 0.12 / 2.872 / 0.105 / 0.32 / 1.619 / 0.218 / 0.25
Soil type / 3.155 / 0.090 / 9.996 / 0.005 / 8.021 / 0.010
Mg2+ / 2.757 / 0.112 / 0.125 / 5.748 / 0.026 / 0.32 / 5.343 / 0.031 / 0.25
Soil type / 2.515 / 0.128 / 7.161 / 0.014 / 4.497 / 0.046
PO43- / 5.499 / 0.029 / 0.16 / 15.011 / 0.001 / 0.40 / 10.705 / 0.004 / 0.31
Soil type / 0.856 / 0.365 / 2.301 / 0.144 / 1.587 / 0.222

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Figure legends

Figure S1 Fine root growth rate versus NH4+ supply rates (mg N/L extract/g resin/month) in clay and sandy loam soils underlying Bornean rainforest. Root parameters are reported per cm3 soil. The line is the least-squares regression line based on a statistically significant relationship with the nutrient supply rate in a linear model (Table S2). Triangles are mean values for clay plots; circles are the mean values for sandy loam plots (n = 13 and 11 plots for clay and sandy loam, respectively).

Figure S2 Fine root (A) length and (B) area growth rates versus Mg2+ supply rates (mg Mg/L extract/g resin/month) in clay and sandy loam soils underlying Bornean rainforest. Root parameters are reported per cm3 soil. The line is the least-squares regression line based on a statistically significant relationship with the nutrient supply rate in a linear model (Table S2). Triangles are mean values for clay plots; circles are the mean values for sandy loam plots(n = 13 and 11 plots for clay and sandy loam, respectively).

Figure S3 Root biomass turnover rate (yr-1) versus (A) K+ and (B) Mg2+ supply rates (mg cation/L extract/g resin/month) on clay and sandy loam soils underlying Bornean rainforest. The line is the least-squares regression line based on a statistically significant relationship with the nutrient supply rate in a linear model. Triangles are mean values for clay plots; circles are the mean values for sandy loam plots (n = 13 and 11 plots for clay and sandy loam, respectively).

Figure S1

Figure S2


Figure S3

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