Cations in solution from forest soils subjected to forest floor removal and compaction treatments

Degree of compaction and loss of organic matter from the forest floor have direct influence on the weathering rates of minerals, nutrient mineralization and consequently of plant growth. However, due to the complicated nature of nutrient depletion and uptake, continued study is essential in order to quantify the components involved in the long-term effects of forest operations (e.g., harvesting and site preparation) on nutrient supply. The objective of this investigation is to compare the amounts of Ca2+, Mg2+, K+, and Al3+ in leachates from forest soils subjected to forest floor removal and soil compaction treatments in the long-term site productivity sites of the BC Ministry of Forests. A leaching experiment was conducted to simulate the long-term impacts of forest operations on soil fertility on 15 cm diameter undisturbed soil core collected from surface soil down to the lower boundary of Ae horizons. Approximately 25 l of water were leached through each column from October 1997 to April 1998. Leachates collected during the experiment were analyzed for Ca2+, K+, Mg2+ and Al3+ and other cations using inductively coupled plasma-atomic emission spectrometry. Results showed that the amounts of Ca2+, K+, Mg2+ and Al3+ in soil solution were highest in the treatment where forest floor was retained and the soil was not compacted and least in soils stripped of forest floor and subjected to compaction treatments. The availability indices for K+ and Ca2+ also decreased with the removal of forest floor. The slopes of linear fits between the amount of cations leached against cumulative volume of leachates could be used as indicators for the long-term effects of forest operations on soil fertility. For instance, and based on these slopes in Topley site, the long-term reduction in the concentration of K+ in soil solution due to forest floor removal and compaction treatments could be as high as 88%. (C) 2000 Elsevier Science B.V. All rights reserved.