Impacts of clearcut harvesting and wildfire on soil nutrient status in the Quebec boreal forest

Abstract

, T. 2001. Impacts of clearcut harvesting and wildfire on soil nutrient status in the Quebec boreal forest. Can. J. Soil Sci. 81: 229-237. Wildfire has historically been the major cause of stand initiation in the boreal forest, shaping species diversity, successional and ecosystem processes. Clearcut harvesting may differ from fire in its effects on soil and vegetation processes and thus may cause long-term changes in stand productivity or biodiversity. This study compared the soil properties of mesic black spruce (Picea mariana) stands burned 2, 14, 21 yr prior to sampling, with stands clearcut within ±3 yr of each wildfire and recently undisturbed control stands. The forest floor (FH) and mineral soil (0-10 cm) were sampled volumetrically, air dried and analysed for pH, organic carbon content, available P, Ca, Mg, and K, mineralizable N and nitrification. Forest floors were also digested and analysed for total N, P, K, Ca and Mg. Significant differences between disturbed and control stands were observed in all study areas, with disturbance effects generally decreasing with time since disturbance. Burned stands generally had forest floors with thinner humus layers, lower mass of organic carbon, higher pH, and higher concentrations of total and available nutrients than in either clearcut or control stands. Significant losses in the total mass of N and K in the forest floor were observed in the youngest burned stands as well as a pulse of extractable P that was at least four times higher than cut or control stands in any other treatment or study area. The forest floor of cut stands had greater mass of organic matter and total nutrients, and higher levels of potentially mineralizable N than either fire or control stands. No significant nutrient loss was observed following clearcut harvesting in any study area. Overall, this study suggested that clearcut harvesting can result in changes to the status of soil nutrients that are different from those produced by wildfire. Further study is necessary to determine whether these differences have significant effects on the long-term productivity or biodiversity of the boreal forest. Les feux irréprimés ont toujours été la principale cause du renouvellement des peuplements dans la forêt boréale. Ce sont eux qui commandent la diversité des espèces, la succession de ces dernières et les fonctionnement de l'écosystème. La coupe à blanc pourrait ne pas avoir les mêmes conséquences sur les processus du sol et de la végétation, et on pourrait se assister à des changements à long terme au niveau de la productivité ou de la diversité biologique du peuplement. Les auteurs ont comparé les propriétés du sol de peuplements mésiques d'épinettes noires (Picea mariana) ravagés par le feu 2, 14 et 21 ans avant l'échantillonnage à celles du sol de peuplements coupés à blanc plus ou moins trois ans avant les feux de forêt et de peuplements témoins intacts. Les auteurs ont prélevé des échantillons volumétriques de la couverture morte (CM) et du sol minéral (de 0 à 10 cm), les ont séchés à l'a...

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

“…While sample preparation was similar and the temperature and moisture conditions comparable the length of our incubation period was twice that used in the Quebec study. The low levels of net nitrification for F horizon and surface mineral soils from our unharvested sites relative to other forest types have been consistently reported for laboratory and field incubations of soils from black spruce forests (Pare´and Bergeron, 1996;Smith et al, 1998;Simard et al, 2001). Low levels of net mineralization and the absence of nitrification has been most often attributed to the poor nutrient quality of coniferous litter (low N and high C:N ratio).…”

“…However, 15 years after harvest the uncut stands in this study had higher net mineralization rates than the harvested sites. Forest harvesting has increased, decreased or resulted in no change to forest floor and mineral soil horizon ammonification and nitrification rates when compared to unharvested boreal stands (Gordon and Van Cleve, 1983;Walley et al, 1996;Smith et al, 1998Smith et al, , 2000Simard et al, 2001;Carmosini et al, 2002Carmosini et al, , 2003. The results from these studies agree with the main conclusion of Grenon et al (2004) in their examination of forest floor N dynamics in coniferous ecosystems in British Columbia.…”

“…Levels of inorganic-N accumulation for the F horizon of unharvested stands at the ELRA were somewhat greater ARTICLE IN PRESS than those reported for the organic layers from black spruce stands in the Quebec boreal forest (Simard et al, 2001). While sample preparation was similar and the temperature and moisture conditions comparable the length of our incubation period was twice that used in the Quebec study.…”

“…In addition, the variability in substrate between harvested and unharvested sites affected microbial biomass cycling that controlled N availability in the forest soil. This is a significant result in that NO À 3 -N production in soils could produce impacts on surface water quality several more years after harvest than anticipated from previous studies where terrestrial production of NO À 3 -N peaked in the first few years after logging (Gordon and Van Cleve, 1983;Simard et al, 2001;Bradley et al, 2002). The foliage addition experiment indicated that maintenance of logging slash on site has the potential to immobilize N and minimize the risk of off-site N losses; however, this effect appeared to be short-lived, as inorganic-N as NO À 3 -N was available in the soils of recent clearcuts.…”

Ecosystem management in paludified boreal forests: enhancing wood production, biodiversity, and carbon sequestration at the landscape level

“…While some studies have focused on natural disturbances (Carcaillet et al 2001;Bergeron et al 2004) and stand dynamics (Harper et al 2003;Gauthier et al 2004;Lecomte et al 2006a), others sought to contrast the effects of silvicultural treatments with those of natural disturbances (Nguyen-Xuan et al 2000;Bescond et al 2011;Simard et al 2001;Arseneault et al 2012;Lafleur et al 2010bRenard et al 2016).…”