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Nutrient Storage in Wood Biomass

Early researchers who found very low concentrations of nutrients in highly weathered soils of the lowland tropics suggested that nutrients were stored primarily in the above-ground biomass of the trees and that that was how nutrients were conserved (Richards 1952). However, a survey that compared nutrient stocks in above-ground biomass in a variety of tropical forests indicated that only certain nutrients are stored primarily in the living biomass (Fig. 2.10). For example, this is true for calcium and potassium in lowland ecosystems that receive more than 2,000 mm/year precipitation. Both calcium and potassium are highly soluble and they are rapidly leached from soils by heavy rains. For these same ecosystems, organic phosphorus is also primarily stored in aboveground biomass. Upon decomposition, the organically bound phosphorus becomes soluble and available to roots through direct recycling. That which is not recycled leaches down to the mineral soil where it becomes bound by iron and aluminum. Although the total amount of inorganic phosphorus in the mineral soil can be high, little is generally available to trees because of the fixation by iron and aluminum. The pattern for nitrogen is different. Relatively little is stored in the trunk of trees. Most is in the organic matter of the soil (Jordan 1985).

Because most of the cations in tropical forests on nutrient-poor soils are stored in the above-ground biomass or the soil organic matter, clear-cutting and removal of the native forest can result in loss of a large portion of the nutrient stocks, even if the area is immediately replanted with trees (Folster and Khanna 1997).

Fig. 2.10. Comparisons of stocks of nutrients in biomass (living vegetation plus litter) and soils of tropical and temperate forests: a calcium and potassium; b phosphorus and nitrogen. The sites are: 1 rain forest, Venezuela; 2 rain forest, Manaus, Brazil; 3 moist forest, Para, Brazil; 4 Banco plateau forest, Ivory Coast; 5 mature forest, Thailand; 6 40-year-old forest, Ghana; 7 seasonal forest, Venezuela; 8 montane forest, Puerto Rico; 9 rain forest, Costa Rica; 10 montane forest, New Guinea; 11 slope forest, Colombia; 12 montane forest, New Guinea; 13 montane forest, Venezuela; 14 beech forest, Sweden; 15 beech forest, Germany; 16 hardwoods, New Hampshire, USA; 17 yellow poplar, Tennessee, USA; 18 oak forest, Oklahoma, USA; 19 oak forest, Virelles, Belgium; 20 30-year-old pine forest, Ontario, Canada; 21 Douglas fir forest, Washington, USA; 22 spruce-fir, British Columbia, Canada; 23 montane fir, Washington, USA; 24 mixed oak, Tennessee, USA; 25 aspen-maple, Wisconsin, USA. (Sources of data are given in Jordan 1985, pp 40-41. Adapted from Jordan 1985, with permission of John Wiley and Sons Ltd., publisher)

Fig. 2.10. Comparisons of stocks of nutrients in biomass (living vegetation plus litter) and soils of tropical and temperate forests: a calcium and potassium; b phosphorus and nitrogen. The sites are: 1 rain forest, Venezuela; 2 rain forest, Manaus, Brazil; 3 moist forest, Para, Brazil; 4 Banco plateau forest, Ivory Coast; 5 mature forest, Thailand; 6 40-year-old forest, Ghana; 7 seasonal forest, Venezuela; 8 montane forest, Puerto Rico; 9 rain forest, Costa Rica; 10 montane forest, New Guinea; 11 slope forest, Colombia; 12 montane forest, New Guinea; 13 montane forest, Venezuela; 14 beech forest, Sweden; 15 beech forest, Germany; 16 hardwoods, New Hampshire, USA; 17 yellow poplar, Tennessee, USA; 18 oak forest, Oklahoma, USA; 19 oak forest, Virelles, Belgium; 20 30-year-old pine forest, Ontario, Canada; 21 Douglas fir forest, Washington, USA; 22 spruce-fir, British Columbia, Canada; 23 montane fir, Washington, USA; 24 mixed oak, Tennessee, USA; 25 aspen-maple, Wisconsin, USA. (Sources of data are given in Jordan 1985, pp 40-41. Adapted from Jordan 1985, with permission of John Wiley and Sons Ltd., publisher)

Fig. 2.10 b
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