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Fire and Nutrient Cycling in a Douglas‐Fir/Larch Forest

Stark, Nellie M.
Ecology 1977 v.58 no.1 pp. 16-30
Pseudotsuga menziesii, biogeochemical cycles, burning, calcium, fires, forests, fuels, fuels (fire ecology), iron, losses from soil, nutrient retention, nutrients, overland flow, pH, rhizosphere, soil types, soil water, surface temperature
Twenty control burns performed with a wide range of fuel loadings and moisture conditions were used to study the effectiveness of old fuel reduction under standing Douglas—fir/larch forest. This paper reports the influence of burning on nutrient retention and loss from the soil. Sixty % of the fires were successful in reducing residual fuels with no accelerated loss of nutrients below the root zone. Net less of Ca⁺ ² and Mg⁺ ² occurred below the root zone when soil surface temperatures exceeded 300°C, but were insignificant when soil surface temperatures remained below 200—300°C. No other elements were loss (net) from the soil as a result of burning. Precipitation on control soils delivers as much Ca⁺ ² as is normally lost below the root zone in the absence of fire. Iron concentration in the soil water is a good indicator of the intensity of burn. The hotter the fire, the less iron in the soil water as a result of the alkaline pH. Ash shows a definite pattern of nutrient release under the influence of precipitation. Homogeneous subsamples of litter showed predictable nutrients losses when ignited at different temperatures. Overland flow and surface erosion are of little significance on this soil type. Decomposition of Douglas—fir litter was only slightly more rapid on hot burned substrates than on control (unburned) substrates. When the biological life concept was applied to this soil, it showed that this soil is young and capable of withstanding many years of cyclic intensive burns.