Changes in nutrient availability and forest floor characteristics in relation to stand age and forest composition in the southern part of the boreal forest of northwestern Quebec

Impact of harvesting and logging slash on nitrogen and carbon dynamics in soils from upland spruce forests in northeastern Ontario

“…The minimal surface water impacts of harvesting reported for the Canadian boreal forest region (Nicolson et al, 1982;Carignan et al, 2000;Lamontagne et al, 2000;Steedman 2000;Prepas et al, 2001), even in studies where no shoreline buffer zones had been established, may be partly explained by the limited potential of upland boreal forest soils to mineralize organic-N to inorganic forms. In general, unharvested boreal forest organic and mineral soils have been shown to have low net inorganic-N production, particularly NO À 3 -N. This has been shown in Quebec (Brais et al, 1995;Smith et al, 2000) and Michigan (Stottlemyer and Toczydlowski, 1999) on the boreal shield and in Saskatchewan on the boreal plain (Walley et al, 1996).…”

Temporal trends in chemical parameters of upland forest soils in southern Finland

“…Binkley and Valentine 1991, Knoepp and Swank 1994, Drohan and Sharpe 1997 and in Canada (e.g. Brand et al 1986, Brais et al 1995, give good grounds to hypothesise that forest soils in southern Finland have undergone acidification, i.e. acidity has increased and base cation concentrations have decreased, during the last decades.…”

“…soil forming processes (podzolisation) (Aaltonen 1935, Jauhiainen 1969, tree stand development (Tamminen 1991, Brais et al 1995, biomass harvesting (Staaf andOlsson 1991, Olsson et al 1996), and the deposition of acidifying compounds (Ulrich et al 1979, Berdén et al 1987). In Nordic conditions, i.e.…”

“…In soils over 10 000 years old, changes in soil properties due to soil-forming processes are assumed to be minimal. Changes in soil properties related to tree stand ageing and growth can be explained on the basis of slower mineralization of organic matter due to cooler, moister soil (Bhatti et al 2000), and perhaps to the occurrence of deeper, longer-lasting soil frost caused by the shading of the tree canopies (Yli-Vakkuri 1960, Päivänen 1973, on the basis of nutrient accumulation in tree biomass, the exudation of acidic material (H + and organic compounds) by tree roots (Gobran et al 1998), the accumulation of acidic coniferous litter on and in the soil (Nihlgård 1971), and more acidic soil water percolating down through the forest floor (Alriksson and Olsson 1995, Brais et al 1995, Krause 1998, Griffiths and Swanson 2001. The organic layer becomes thicker, the organic and uppermost mineral soil layers become more acidic, and the nitrogen and base cation concentrations decrease (Tamminen 1991, Brais et al 1995.…”

Understanding ecosystem retrogression

“…1); this decline in biomass over lengthy time scales is what distinguishes retrogressive ecosystems from those in which biomass is inherently low due to other factors (e.g., climate). This retrogression is also quite distinct from age-related declines in forest biomass or productivity that frequently occur over far shorter time scales as a result of changes in the physiological properties of plants (e.g., declining photosynthesis to respiration ratios, increasing stomatal limitation as trees age), increasing hydraulic limitation as trees grow taller, and reductions in soil nutrient mineralization rates (e.g., Brais et al 1995, Gower et al 1996, Ryan et al 1997, Magnani et al 2000. In contrast to these age-related declines, ecosystem retrogression involves multiple generations of the dominant plant species and is largely a pedogenically driven process.…”