Abstract
We report carbon stock in biomass, litter and soil estimated for six locations in natural Quercus ilex L. stands of the Middle and High Moroccan Atlas. Twenty trees at each location were selected according to their diameter classes and felled to measure the biomass of trunk, branches, twigs and leaves and determine allometric relationships. Soil was sampled in five depths (0 - 15, 15 - 30, 30 - 50, 50 - 70 and 70 - 100 cm) and litterfall production measured in all tree stands. The total carbon stock in above-ground biomass ranged between 17 Mg·haǃ in Aït Aamar stand (High Atlas) and 91 Mg·haǃ in Ksiba stand (Middle Atlas). Perennial organs (trunk, branches and twigs) stored over 95% of the tree carbon stock. Soil organic carbon concentrations ranged from 0.01% (in 70 - 100 cm in all stands) to 8.1% (in 0 - 15 cm in the Ajdir stand in Middle Atlas). The total organic carbon stock in the soil ranged between 141.4 t·haǃ in Ajdir and 24.6 t·haǃ in Asloul. The litter contained 0.2 Mg C haǃ in the clearing (C2) stand of High Atlas and 14.3 Mg C haǃ in (Ajdir) of carbon. The best fitted model for predicting carbon stock in tree biomass was obtained by applying the allometric equation Y = aXb for each biomass fraction and stand, where Y is the aboveground biomass (dry weight) and X is the DBH (Mean diameter at breast height, 1.30 m). These previous data obtained in the present study confirm the important function of these natural forests as longterm C sinks, in forest biomass, litter and soil. The potential long term C storage of these systems is moderately high, especially in less-intensively managed forests that include large trees. The established relationship between DBH and carbon stock in different tree organs can be used for forest carbon accounting, and also synthesize available information on oak forest as a sink for atmospheric CO2, and identify the management options that may enhance the capacity for C capture/ storage in forest soils.
Highlights
Carbon sequestration in forests helps to mitigate the accumulation of greenhouse gases in the atmosphere (Adams et al, 1999)
The soil organic carbon concentrations (%) ranged from 0.01% to 8.1%, with minimum values recorded in the 70 - 100 cm of all stands and maximum―in the 0 - 5 cm layer of Ajdir stand
They decreased following an exponential curve with a negative exponent in all stands selected, as well as the deviation among the organic carbon stocks of different depth intervals in all sampled stands decreased with the soil depth
Summary
Carbon sequestration in forests helps to mitigate the accumulation of greenhouse gases in the atmosphere (Adams et al, 1999). Forests currently store a substantial stock of carbon, amounting to 826 billion metric tons in trees and soil (Brown, 1998). This stock can be further enhanced by implementing appropriate forest management strategies, such as regulating timber harvest intensity or rotational length (Murray 2000) and by increasing the land area under forests (Adams et al 1999). The forest soils may become a significant source of CO2, followed by a climatic global warming, since this last could carry out a mineralization of organic matter, higher than the primary net production of vegetation (Liski 1999; Bernoux et al 2005). Minor changes of organic carbon reservoir in the soil may significantly affect the CO2 concentration in the atmosphere, since the soil contains twice more carbon than the atmosphere (Schlesinger 1997; Post and Kwom 2000; Torn et al, 1997; Watson et al 1990)
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