Soil oxygen within boreal forests across an age gradient

Abstract

Fenton, N., Légaré, S., Bergeron, Y. and Paré, D. 2006. Soil oxygen within boreal forests across an age gradient. Can. J. Soil Sci. 86: 1-9. Globally, soil anoxia and water table rise play a role in the development of peatlands from forests. Cited causes have included a diversity of internal and external mechanisms, including Sphagnum and feather mosses, hardpan development, and peatland expansion. The objectives of this study were to examine water table depth in black spruce stands of the Clay Belt of Quebec and Ontario, and to associate changes with potential stand scale causal factors (primarily biological). A methodological issue, the link between oxygen zone and water table, was also addressed. Within stands less than 100 yr post-fire, oxygen zone and water table position were only loosely related, and no other potential factors were significantly correlated. Across a chronosequence of stands, while oxygen zone thickness in the soil profile was relatively constant, its position relative to the mineral soil changed, as it rose from the mineral soil into the forest floor. Forest floor thickness was the dominant explanatory factor in oxygen zone position, suggesting that in these forests other postulated mechanisms are less important. At the landscape level, the movement of the oxygen zone into the forest floor has important consequences for the long-term productivity of this intensively exploited forest region. 1-9. Partout dans le monde, l'anoxie du sol et l'élévation de la nappe phréatique jouent un rôle dans la transformation des forêts en tourbières. Ces deux causes cachent une diversité de mécanismes internes et externes, notamment le rôle des sphaignes et des hypnums, le développement de la cuirasse et l'expansion des tourbières. L'étude devait préciser la profondeur de la nappe phréa-tique dans les peuplements d'épinettes noires de la ceinture d'argile du Québec et de l'Ontario, et associer les changements observés aux facteurs causaux d'une échelle forestière potentielle (à caractère essentiellement biologique). Les auteurs se sont aussi penchés sur une question de méthodologie, à savoir le lien entre la zone oxygénée et la nappe phréatique. Dans les peuplements de moins de cent ans, après destruction par le feu, la zone oxygénée présente très peu de liens avec la hauteur de la nappe phréatique, et il n'existe aucune corrélation significative avec d'autres facteurs éventuels. Dans une série de peuplements classés chronologiquement, on remarque que si l'épaisseur de la zone oxygénée du sol est relativement constante, son emplacement varie par rapport à celle du sol minéral quand elle s'en détache pour migrer vers le tapis forestier. L'épaisseur du tapis forestier est le principal facteur qui explique l'emplacement de la zone oxygénée, ce qui laisse croire que d'autres mécanismes postulés ont moins d'importance dans les forêts de ce genre. Au niveau du relief, le déplacement de la zone oxygénée vers le tapis forestier a d'importante répercussions sur la productivité à long terme de cette région forestiè...

Disturbance legacies and paludification mediate the ecological impact of an intensifying wildfire regime in theClayBelt boreal forest of easternNorthAmerica

“…This transition implies higher soil moisture conditions (Fenton et al. ; Simard et al. ; Terrier et al.…”

The pyrogeography of eastern boreal Canada from 1901 to 2012 simulated with the LPJ-LMfire model

“…In the Clay Belt, the poor drainage conditions induced by the presence of an impermeable clay substrate, flat topography, and a cold climate facilitate the accumulation of thick layers of organic soil, an edaphic process that is referred to as paludification (Fenton et al, 2006). Once Sphagnum species increase on the forest floor, the depth of burn varies only slightly in response to changes in weather conditions, owing to very low fluctuations in the degree of water saturation of the organic layer (Fenton et al, 2006).…”

“…The spatiotemporal variability in a fire regime depends upon the coincidence of favourable conditions for fire ignition, fire propagation, and fuel availability, which are controlled by ignition agents, weather and climate, and vegetation (Flannigan et al, 2009;Moritz et al, 2010). Almost half of the fires that occur in eastern boreal Canada are ignited by lightning and represent 81 % of the total area burned (Canadian Forest Service, 2016), while the remaining fires originate from human activities.…”

The pyrogeography of eastern boreal Canada from 1901 to 2012 simulated with the LPJ-LMfire model

“…Similarly, improving LPJ-LMfire parametrization to account for mosses could reduce overestimation of quantities of fuel that was available in northern areas. In the Clay Belt, poor drainage conditions that were induced by the presence of an impermeable clay substrate, flat topography and a cold climate facilitate the accumulation of thick layers of organic soil, an edaphic process that is described as paludification (Fenton et al, 2006). Once Sphagnum 10 species increase on the forest floor, the depth of burn varies only slightly in response to changes in weather conditions, owing to very low fluctuations in the degree of water saturation of the organic layer (Fenton et al, 2006).…”