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Tree regeneration and growth is generally reduced at forest harvest landing areas because of significant soil compaction, but it is commonly believed that harvesting in winter can reduce these impacts and that recovery occurs naturally with time. We used lidar data to assess differences in vegetation height between landing and general harvest areas across 79 sites in northern Minnesota, United States, that had been harvested in either summer/fall or winter and between 2 and 175 months since harvest. Vegetation height was significantly lower at landing areas compared with general harvest areas; however, there was no effect of harvest season on the difference (p = 0.50), indicating that impacts occur during all seasons. There was a significant (p < 0.01) positive relationship between the difference in vegetation height and time, regardless the harvest season, providing evidence that recovery occurs across a wide range of conditions within our time period of assessment. Sites with three landings present had the lowest relative landing area and also had the lowest differences in vegetation height between landing and general harvest areas, demonstrating the potential for optimized landing configurations to minimize impacts to growth. Based on our findings, landing areas should be kept as small as reasonably possible during all seasons of harvest, but the need for active reclamation practices is probably not warranted given that recovery occurs within the first few decades after harvest. Key words: winter harvesting, soil compaction recovery, forest soils, Lake States. La regeneration et la croissance des arbres sont generalement plus faibles sur les jetees amenagees pour la recolte du bois a cause de la forte compaction du sol, mais on croit generalement que le fait de recolter en hiver peut attenuer ces impacts et que les proprietes du sol se retablissent naturellement avec le temps. Nous avons consulte des donnees lidar pour evaluer les differences de hauteur de la vegetation entre les jetees et le reste de l'aire de coupe dans 79 stations du nord du Minnesota, aux Etats-Unis. Ces stations ont ete recoltees soit durant l'ete et l'automne, soit durant l'hiver, et les donnees ont ete recueillies de 2 a 175 mois apres la recolte. La hauteur de la vegetation etait significativement plus faible sur les jetees qu'ailleurs dans l'aire de coupe, mais la saison de recolte n'avait pas d'effet (p = 0,05) sur la difference; ce qui signifie que les impacts surviennent Durant toutes les saisons. Il y avait une relation positive significative (p < 0,01) entre la difference de hauteur de la vegetation et le temps ecoule depuis la recolte, peu importe la saison de recolte; ce qui prouve que les proprietes du sol se retablissent dans toutes sortes de conditions a l'interieur de notre periode d'evaluation. Les stations oU il y avait trois jetees avaient la plus faible superficie relative de jetee et avaient aussi les plus faibles differences de hauteur de la vegetation entre les jetees et le reste de l'aire de coupe; cela illustre le potentiel d'optimisation de la configuration des jetees pour minimiser les impacts sur la croissance. Sur la base de nos resultats, on devrait garder les jetees aussi petites qu'il est raisonnablement possible de le faire peu importe la saison de recolte, mais il n'est probablement pas necessaire d'avoir recours a des mesures actives de rehabilitation etant donne que le retablissement des proprietes du sol survient durant les premieres decennies suivant la recolte. [Traduit par la Redaction] Mots-cles: recolte hivernale, retablissement des proprietes du sol a la suite de la compaction, sols forestiers, Etats limitrophes des Grands Lacs., Introduction Forest landings are used during harvesting operations to store and load wood, maintain and stage harvest machinery, and serve as central areas to coordinate harvest activities. Landings are characterized [...]

We evaluated effects of topsoil scarification by heavy machinery on growth of two valuable, shade-intolerant tree species--Nothofagus dombeyi (Mirb.) Oerst. (evergreen and considered to be very plastic to different soil fertility levels) and Nothofagus alpina (Poepp. & Endl.) Oerst. (deciduous and considered to be sensitive to soil fertility) - seedlings that were underplanted in Nothofagus old-growth forests, which were subjected to shelterwood cuttings without the final cut in the Chilean Andes. We compared tree basal diameter growth as it responds to light availability and soil compaction (as measured by resistance to penetration) by fitting a growth model based on the Michaelis-Menten equation. Predicted growth of N. dombeyi was greater than N. alpina in high and low light levels; however, there were no significant differences between the species. Both species showed significant differences at high levels of penetration resistance (>2000 kPa). Differences for N. dombeyi occurred above ~40% in total light, and differences occurred for N. alpina above ~20% in total light. However, they were not different when compared at low and intermediate levels of penetration resistance. The results suggest that partial shelterwood cuts may provide adequate light levels to achieve appropriate growth of underplanted Nothofagus seedlings. However, if regeneration of N. alpina is desired, scarification of topsoil needs to be implemented with more caution in canopy openings, as traffic and soil removal by heavy machinery can have detrimental effects on growth of this species and other species that are more sensitive to soil compaction. Key words: Michaelis-Menten, shade tolerance, soil resistance to penetration, stress conditions, underplanting. Nous avons evalue les effets du scarifiage de la couche superieure du sol avec de la machinerie lourde sur la croissance de semis de deux especes d'arbre precieuses et intolerantes a l'ombre, Nothofagus dombeyi (Mirb.) Oerst. (espece a feuilles persistantes qui est consideree comme etant tres plastique a differents niveaux de fertilite du sol) et Nothofagus alpina (Poepp. & Endl.) Oerst. (espece decidue qui est consideree comme etant sensible a la fertilite du sol). Ces semis ont ete plantes sous le couvert de vieilles forets de Nothofagus soumises a des coupes progressives sans la coupe finale dans les Andes chiliennes. Nous avons relie la croissance en diametre au collet des semis a la disponibilite de la lumiere et a la compaction du sol (mesuree par la resistance a la penetration) en ajustant un modele de croissance fonde sur l'equation de Michaelis-Menten. La croissance predite de N. dombeyi etait plus grande que celle de N. alpina sous des intensites lumineuses forte et faible, mais sans qu'il y ait de differences significatives entre les especes. Des differences significatives ont ete observees chez les deux especes lorsque la resistance a la penetration etait elevee (>2000 kPa). Les differences ont ete observees chez N. dombeyi au-dessus de ~40 % de la lumiere totale alors qu'elles l'ont ete au-dessus de ~20 % dans le cas de N. alpina. Toutefois, aucune difference n'a ete observee lorsque la resistance a la penetration etait faible ou intermediate. Ces resultats indiquent que les coupes progressives peuvent procurer des niveaux de lumiere adequats pour obtenir une croissance appropriee des semis de Nothofagus plantes sous couvert. Cependant, si on desire que la regeneration de N. alpina s'etablisse, le scarifiage de la couche superieure du sol doit etre realise plus prudemment dans les ouvertures du couvert parce que la circulation et l'enlevement du sol par la machinerie peuvent avoir des effets nefastes sur la croissance de cette espece et d'autres qui sont plus sensibles a la compaction du sol. [Traduit par la Redaction] Mots-cles: Michaelis-Menten, tolerance a l'ombre, resistance du sol a la penetration, conditions de stress, plantation sous couvert., Introduction Silvicultural practices manage canopy structures with the objective of regenerating and reallocating growing space for desired crop species (Nyland 2002; Puettmann et al. 2008a). Questions on which resource levels [...]

There is considerable interest in understanding the repercussions of compaction and organic matter removal on soil quality and forest productivity. However, long-term field trials examining the effects of machinery and forest biomass removal on soil quality and stand regeneration are scarce. We present 20-31 years of tree growth results from four unique stump removal field trials. Each site had both treatments with varying amounts of organic matter removal (from tree stem harvesting to removal of tree stumps to loss of roots) and treatments with different levels of compaction due to site preparation machinery. Tree heights among the different treatments at midrotation were the same or taller than those with minimal organic matter removal and compaction. However, when stand development was evaluated using the quantity of tree volume for the given number of trees planted, treatment effects were clearly evident; tree volumes were significantly lower in compacted treatments, whereas organic matter removal did not appear to effect stand production. Although the sites were not directly comparable, when combined, the field trials provide insights to the possible implications of forest biomass harvesting on stand regeneration and overall forest soil quality. Key words: forest soil quality, compaction, organic matter removal, stumping, root rot. La comprehension des repercussions de la compaction et du prelevement de la matiere organique sur la qualite des sols et la productivite de la foret suscite un interet considerable. Cependant, il y a peu d'experiences a long terme sur le terrain qui portent sur les effets de la machinerie et du prelevement de la biomasse sur la qualite du sol et la regeneration des peuplements. Nous presentons des resultats de croissance des arbres provenant de quatre essais experimentaux particuliers 20 a 31 ans apres un dessouchage. Des traitements consistant a enlever differentes quantites de matiere organique (integrant successivement la recolte du tronc des arbres, le dessouchage et l'elimination des racines) ont ete appliques dans chacun des sites qui avaient aussi subis differents degres de compaction du sol par la machinerie utilisee pour la preparation du site. A mi-rotation la hauteur des arbres etait semblable dans les differents traitements ou plus grande que dans le traitement ou il y avait eu le minimum de prelevement de matiere organique et de compaction du sol. Cependant, lorsque le developpement du peuplement etait evalue en utilisant le volume des arbres pour un nombre donne d'arbres plantes, l'effet des traitements etait nettement visible : le volume des arbres etait significativement plus faible dans les traitements ou le sol avait ete compacte tandis que le prelevement de la matiere organique ne semblait pas avoir d'effet sur la production du peuplement. Bien que les sites ne soient pas directement comparables, lorsqu'ils sont combines les essais experimentaux donnent un apercu des consequences potentielles de la recolte de la biomasse forestiere sur la regeneration des peuplements et la qualite generale des sols forestiers. [Traduit par la Redaction] Mots-cles: qualite des sols forestiers, compaction, prelevement de la matiere organique, dessouchage, carie de racines., 1. Introduction Mechanization of the forest industry in North America increased through the 1940s, and this prompted a growing concern on the impacts of harvesting techniques on forest soil quality. [...]

Soil erosion is seen as a kind of pollution. The trend towards applying soil stabilization techniques in protecting the environment is discussed. This trend has boosted the market for soil improvement tools.

Fluxes of the greenhouse gases, [N.sub.2]O and C[H.sub.4], were measured across a skid trail at three beech (Fagus sylvatica L.) forest sites with soils of different texture. At each site three skid trails were established by applying two passes with a forwarder. Soil compaction in the middle of the wheel track caused a considerable increase of [N.sub.2]O emissions with values elevated by up to 40 times the uncompacted ones. Compaction reduced the C[H.sub.4] consumption at all sites by up to 90%, and at the silty clay loam site its effect was such that C[H.sub.4] was even released. These changes in [N.sub.2]O and C[H.sub.4] fluxes were caused by a reduction in macropore volume and an increase of the water-filled pore space (WFPS). Additionally, the slipping of the forwarder's wheels led to a mixing of the humus layer with the mineral soil, which resulted in a new layer. This layer reduced gas exchange between the soil and the atmosphere. Trace gas fluxes were altered in the trafficked soil and in the adjacent areas. Despite the significant changes in the trace gas fluxes on the skid trails, the cumulative effect of the two gases on the atmosphere was small with respect to total emissions. However, if soil trafficking is not restricted to the established skid trail system the area of compaction and consequently the atmospheric load by greenhouse gases may increase with every harvesting operation.

Increased use of heavy equipment and more frequent entry into forest stands has increased the potential for soil compaction and decreased productivity. We examined compaction and tree growth relationships on three California soils of contrasting textures (clayey, loamy, and sandy loam) on plots from which the organic soil horizon had been removed. Compacted and noncompacted treatments were compared. Changes in bulk density ([D.sub.b]), soil strength, and total porosity, measured during the growing season, were greatest in the 15- to 30-cm depth at all sites. Bulk density increases were greatest in the loamy soil (30%) and least in the sandy loam (23%). Total porosity decrease in the upper 45 cm averaged 20, 9, and 13% for the clay, loam, and sandy loam textures, respectively. In the 30- to 45-cm soil depth, compacted soils reached critical water potentials (< -1.5 MPa) 50 d sooner in the loam and 67 d sooner in the clay. In the sandy loam, compaction extended the period of plant-available water for 86 and 48 d in the 1- to 15- and 15- to 30-cm soil depths. Midday stem water stress was greater for trees in compacted plots of loamy and clayey textures, but less on sandy loam. Soil compaction did not reduce tree growth universally in these 3- to 8-yr-old plantations. Effects were detrimental, insignificant, and beneficial for clayey, loamy, and sandy loam soils, respectively. Results show that compaction effects depend strongly on soil texture and soil water regime. Soil physical values, per se, are not always reliable criteria for evaluation.

Lakes and streams are important features that attract recreationalists (Lime 1971; Clark and Downing 1985). Riparian systems associated with these areas have a number of functions not found in upland [...]

A case study of the settlement of gravelly sand backfill is presented. Flatwork, which had been constructed on top of the backfill, was damaged due to the settlement. It is likely that the cause of the settlement was improper compaction methods and/or too low of a compaction standard. Laboratory tests were performed to investigate the settlement behavior of the gravelly sand. If the gravelly sand had 0-20% oversize particles, there were not enough oversize particles to interfere with compaction and the settlement behavior depends on the matrix dry density. For 20-40% oversize particles, they begin to interfere with compaction, but the settlement behavior still depends on the matrix dry density. For 40-70% oversize particles, they continue to interfere with compaction, and the settlement behavior is very complex and depends on the proportion of vertical stress carried by the oversize particles. For 70-100% oversize particles, the compaction energy is absorbed by the oversize particles and the settlement behavior depends on the compression behavior of the oversize particles.

The relation between streambank stability and herbaceous roots is discussed. Samples from six meadow stream reaches were subjected to unconfined compressive strength, root-length density,plant community and engineering soil characteristics measurements. Correlation were made between these parameters. Results indicate that noncohesive soils were strengthened by herbaceous roots.

A study seeks to determine the relative importance of environmental and genetic factors and the interaction between them on the expression of an avoidance strategy of the desert lily Pancratium sickenbergeri. Results indicate that mean bulb depth of the desert lily differs considerably among populations differing in the level of herbivory by the dorcas gazelle, with a possible confounding factor being the degree of sand compaction, which may retard the downward growth of the bulb.