Canadian Forest Service Publications
Influence of afforestation on soil: The case of mineral weathering. 2013. Lafleur, B.; Paré, D.; Claveau, Y.; Thiffault, E.; Bélanger, N. Geoderma 202-203:18-29.
Available from: Laurentian Forestry Centre
Catalog ID: 34660
CFS Availability: PDF (request by e-mail)
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Although concerns have been raised that increased nutrient demand by fast growing tree species could deplete soil nutrient pools, recent research suggests that some species are able to obtain nutrients via soil mineral weathering. Hybrid poplars, which are fast growing and nutrient demanding species, are increasingly used in intensive silvicultural settings. Understanding whether hybrid poplars have an effect on long term nutrient availability and can promote soil mineral weathering is therefore important. We investigated the levels of base cations (i.e. K, Ca, Mg, and Na) of surface soils (0–20 cm) in 13 hybrid poplar plantations in Quebec, and compared the results with those of adjacent abandoned agricultural fields. To evaluate whether exchangeable base cation pools and non-exchangeable pools (i.e. those in the crystal lattice of minerals) were being depleted, we used a sequential leach with diluted salt (BaCl2 for exchangeable) and weak acid solutions (HCl and HNO3 for non-exchangeable). Levels of exchangeable and non-exchangeable cations were not statistically different between land use types. Exploratory analyses, however, revealed trends toward a greater depletion of Ca, Mg and Na in non-exchangeable forms following afforestation. The depletion of these non-exchangeable base cations due to afforestation occurred at sites where greater levels were initially present in soil. The results suggest increased soil mineral weathering due to greater amounts of minerals susceptible to dissolution and, in part, high clay content. Based on Ca, Mg and K concentrations of the different leaches and their molar ratios (Ca/ΣAl + Fe, Mg/ΣAl + Fe and K/ΣAl + Fe), we propose a lesser role of soil mineral weathering on Ca cycling than Mg and K, which could lead to faster depletion of exchangeable Ca pools of the surface soil due to fast growth and high Ca demand by the poplars.
Plain Language Summary
A study was conducted to assess the impact of the presence of hybrid poplars – which are fast growing – on soil fertility. The research was carried out in 13 hybrid poplar plantations established on abandoned farmland in Quebec. The researchers concluded that the presence of hybrid poplar plantations does not deplete soils in the short term; the quantity of available nutrients remains much the same as in unplanted sites. This is due to the ability of poplars to draw the nutrients they need from the soil, even when nutrient availability from minerals in the same soil is low.
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