Figure 1.
Soil profile at the control site (Panel a) and the charcoal hearth (Panel b).
The letters indicate different pedologic horizons. In the charcoal hearth the dark anthropogenic layer (Acoal; 0–10 cm) can be easily identified.
Table 1.
Parameters, coefficients and variables used to distinguish and quantify the different carbon pools in charcoal soil layer (means ± standard error, n = 3).
Table 2.
Total carbon and nutrient stocks in the control soils and charcoal hearths and the estimated amount added by carbonization calculated according to Eq. [2].
Table 3.
Total and available nutrient concentrations (mg kg−1 dry matter ± standard error; n = 3) measured in control soils, charcoal hearths, old and new charcoal fragments and larch wood.
Figure 2.
Correlation between average annual atmospheric deposition of P, K+, Ca2+, Mg2+, Na2+ (mg l−1 y−1) and the difference between the input of the same elements due to charcoal application in 1858 and the amount found today in hearth’s soils (Δelement, kg hearths−1) (y = 2.50×–14.31, R2 = 0.82, p = 0.035).
Dashed lines represent 95% confidence interval.
Figure 3.
Keeling plots measured by CRDS showing the δ13C of respired CO2 fluxes versus the reciprocal of CO2 concentration for control and charcoal hearth incubated soils (δ13CCONTROL = 7353*[CO2]−1−24.8, R2 = 0.99; δ13CCHARCOAL HEARTH = 7467*[CO2]−1−25.2, R2 = 0.99).
Horizontal and vertical bars indicate standard deviations (n = 3).
Figure 4.
SEM micrographs showing the inner morphology of charcoal fragments and the absence of any microbes or plant debris.
a) is a radial section b) a longitudinal section.
Figure 5.
Carbon content of charcoal produced from larch wood at different temperatures.
Wood samples were collected in close proximity to the hearths. Charcoal was produced in a muffle furnace at 400°, 500° 600° and 860°C. Dashed lines represent 95% confidence interval. (Y = 26.9+0.15 X-9.2 10−5 X2; r2 = 0.94; p<0.0001).
Table 4.
Description of larch forests considered as analogues of the larch forest harvested for charcoal production in Val di Pejo (mean ± standard error).
Table 5.
Parameters, coefficients and variables used to estimate charcoal stability in soil (mean ± standard error; n = 3).
Table 6.
Uncertainty and sensitivity analysis results for the setimation of equation 3 parameters.