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Determining Vertical Root and Microbial Biomass Distributions from Soil Samples

^a CSIRO Land and Water, 120 Meiers Road, Indooroopilly, QLD 4068, Australia, and The Univ. of Queensland, St. Lucia, QLD 4067, Australia
^b Manaaki Whenua–Landcare Research, P.O. Box 69, Lincoln, New Zealand

View larger version (10K): [in a new window]   Fig. 1. Relations between the sampling depth interval, zi, and depth at the top of the sample, zi, for different values of the length scale bias, , according to Eq. [11]. A constant and negative bias of 10% was used in the calculations.

View larger version (14K): [in a new window]   Fig. 2. (a) Relations between root biomass density, R, and depth, z, beneath a tropical forest according to Veldkamp et al. (2003). The lines and data points are explained in the legend. (b) Same data as in (a), plotted as log-linear to highlight differences.

View larger version (15K): [in a new window]   Fig. 3. Relation between a normalized root biomass density, R* from Eq. [A6], and depth, z, for three values of ß. The insert shows the relationship between RGG and z according to Eq. [A5] based on the reasoning of Gale and Grigal (1987; see their Fig. 3).

View larger version (10K): [in a new window]   Fig. 4. Relations between the maximum bias and parameter C determined for a vertical root biomass distribution and 1, a sampling depth interval to length scale ratio, according to Eq. [10]. The maximum bias is denoted by negative values to indicate the required correction.

View larger version (6K): [in a new window]   Fig. 5. Relationship between Y0*/Y0, ratio of apparent to actual soil property at the surface, and i, a sampling depth interval to length scale ratio, according to Eq. [11].

View larger version (15K): [in a new window]   Fig. 6. (a) Relations between root biomass density, R, and depth, z, according to Eq. [5] and [7]. For Eq. [7], values of i were calculated using characteristic length scale (Zr) = 0.184, R0 = 1111 g m–3, and discrete soil sample depth intervals, z, of 0.1 (five solid circles between the surface and z = 0.5 m), 0.5 (2 solid squares shown at z = 0.75 and 1.25 m) and 1.0 m (3 open squares shown at z = 1.5, 2.5, and 3.5 m). The data points were calculated to a depth of 4 m. The three curves were derived by least squares fitting of i and i to Eq. [5] using all the values calculated for a single z, and led to a single value of Zr (= 0.184), but three values of R0 including 1115, 1487, and 3092 g m–3 for z of 0.1, 0.5, and 1.0 m, respectively. (b) Same data plotted as log-linear to better illustrate the intercept shift.