ALBERT

Description: Constraints of the physical environment affect forest growth and forest operations. At a local scale, these constraints are generally considered during forest operations. At regional or continental scales, they are often integrated to larger assessments of the potential for a given land unit to be managed. In this study, we propose an approach to analyze the integration of physical-environment constraints in forest management activities at the regional scale (482 000 km2). The land features that pose constraints to forest management (i.e., hydromorphic organic deposits, dead-ice moraines, washed till, glacial block fields, talus, and active aeolian deposits, slopes 〉 40%) were evaluated within 1114 land districts. To distinguish land districts that can be suitably managed from those where constraints are too important for sustainable timber production, we carried out a sensitivity analysis of physical constraints for the 1114 land districts. After analysis of two portions of the study area under management, a land district was considered suitable for management when more than 20% of its land area consists of features imposing few constraints or, for mountain-type relief districts, when more than 40% of the land area consists of features imposing few constraints. These cutoff values were defined by expert opinion, based on sensitivity analyses performed on the entire study area, on analyses of two different sectors with different types of constraints and on a strong understanding of the study area. Our results show that land districts where the physical environment posed significant constraints covered 7.5% of the study area (36 000 km2). This study shows that doing an a priori classification of land units based on permanent environmental features could facilitate the identification of areas that are not suitable for forest management activities.

Description: Following spruce budworm (Choristoneura fumiferana (Clem.)) outbreaks, Baskerville's model (G.L. Baskerville. 1975. Spruce budworm: super silviculturalist. For. Chron. 51: 138-140), referred to as the cyclic model, is generally accepted as one of the best established regeneration models in wet boreal fir stands typical of northeastern America. According to that model, old virgin fir stands killed by the insect are replaced by other fir stands. In this study, we wanted to check if the cyclic model would work with wet boreal fir stands originating from harvest and having reached the felling age (50-60 years old) observed in Quebec. The study set up after the last budworm outbreak (1974-1987) shows that, although coniferous regeneration is abundant, the seedling bank is obviously immature: young and small seedlings, empty microsites. In most cases, the regeneration is codominated or dominated by deciduous species, which may bring about the development of a deciduous stand. Thus, the cyclic model does not seem suited to describe dynamics of second-growth boreal fir stands when it is kept in a premature state (

Description: The renewal of boreal fir stands after harvesting is related to the abundance of fir advanced regeneration. The objective of this study was to compare the advanced regeneration in 45-years-old balsam fir stands of second growth to determine if ecological site conditions could explain some regeneration problems noted in the balsam fir – white birch ecoclimatic domain. Seven ecological phases were studied; these are among the most common in the Laurentians north of Québec. On the basis of fir seedling densities (2 years old and more), three groups could be distinguished using a cluster analysis method for grouping means. Dry balsam fir – herb-and-moss type on well drained tills formed a first group characterized with very high seedling densities (〉 60 000 seedlings/ha). A second group, characterized with high seedling densities (25 000 – 40 000 seedlings/ha), was constituted of three phases with an important moss cover:the mesic balsam fir – moss-and-herb type on moderately well drained tills, the humid balsam fir – moss-and-herb type on imperfectly drained tills with seepage, and the humid balsam fir – moss type on imperfectly drained tills. A third group, with low seedling densities (

Description: Application of base-cation fertilizers has been shown to increase tree growth and vigour in declining sugar maple (Acersaccharum Marsh.) stands in southern Quebec but little is known about the effects of such fertilizers on litter quality or decomposition. Sugar maple foliage litters from fertilized and unfertilized plots on a base-poor site and from a naturally base-rich site were incubated in litterbags of 1- and 3-mm mesh sizes on fertilized and unfertilized plots at the base-poor site. Mass loss of unfertilized litter was slower in fertilized than in unfertilized plots, suggesting a negative effect of fertilization on the decomposer community. Faster mass loss of fertilized than unfertilized litter incubated in the same plot indicated that changes in litter quality brought about by fertilization enhanced decomposition. Mass loss of fertilized litter on fertilized plots did not differ from that of unfertilized litter on control plots, indicating that although decomposition processes are affected by fertilization the overall effect on decomposition is negligible. Mass loss was significantly, but only slightly, higher in large mesh than in small mesh bags indicating that larger soil fauna play a limited role in litter decomposition in this forest.

Description: We used an extensive vertebrate exclosure experiment to evaluate black spruce (Picea mariana (Mill.) B.S.P.) postdispersal seed and seedling predation by invertebrates in three boreal habitats of Eastern Canada: recent burn, sprucemoss, and lichen woodland. Between 9% and 19% of seeds were eaten by invertebrates. Seed predation was higher in recent burns than in sprucemoss and lichen woodlands. Abundance and diversity of potential invertebrate seed consumers sampled in pitfall traps also varied among habitat types. Among the invertebrate seed consumers sampled, Myrmica spp. (Hymenoptera: Formicidae) and Pterostichus adstrictus (Eschscholtz, 1823) (Coleoptera: Carabidae) were the most numerous; Formica spp. (Hymenoptera: Formicidae) and Pterostichus punctatissimus (Randall, 1838) (Coleoptera: Carabidae) were also present. Between 2% and 12% of juvenile black spruce seedlings were eaten by invertebrates. The most important seedling consumers were slugs (molluscs). Invertebrate predation of seeds and seedlings was highest (19% and 12%) in recent burns, indicating that invertebrate predation may significantly influence black spruce regeneration in these sites.

Description: Land application of liquid manures is a major source of atmospheric ammonia. The presence of crop residues on the soil surface usually increases emissions by retarding slurry infiltration, whereas incorporation of slurry into soil reduces emissions. Our objective was to quantify the relative reduction in NH3 volatilization resulting from the soil incorporation of pig slurry (PS) applied on canola (Brassica napus) residues under fall conditions in Quebec, Canada. Pig slurry was applied at 7.4 L m–2 on six plots covered by canola crop residues. Slurry and residues were incorporated in the top 5 cm of soil (INCORP) in half of the plots, while the other half were left untouched (SURF). Ammonia volatilization was measured following application for 10 d using wind tunnels. Soil NH4+ and NO3− contents, pH, moisture and temperature were also monitored to explain variations in NH3 fluxes. Soil NH4+-N in the surface soil was lower than expected shortly after slurry application, maybe as a result of fixation by clays or interception by crop residues. The volatilization of NH3 was higher (P 〈 0.05) on SURF plots than on INCORP plots in 20 of the 26 measuring periods, with total NH3 losses being five times greater in the former. Cumulated emissions during the first 11 h accounted for the 60 and 53% of total NH3 emissions for the SURF and INCORP plots, respectively. Our results confirm that a large fraction of the NH3 volatilization from slurry application on canola residues can be greatly reduced if the slurry and crop residues are incorporated into the soil immediately after slurry application. Despite significant reduction (80%) of NH3 volatilization in INCORP compared with SURF plots, no difference was found in soil mineral N between treatments, suggesting that other processes such as N mineralization or denitrification were more active in INCORP plots. Key Words: Ammonium, nitrate, nitrogen cycle, organic amendments

Description: The influence of 40 years of red pine and Norway spruce growth on forest floor and soil nutrient status was examined in a well-replicated series of plantation blocks established on abandoned agricultural land. Concentrations of N, P, K and Ca, and mass of organic matter and all nutrients in the forest floor were higher under spruce than under pine. In the mineral soil, concentrations of exchangeable K and Ca were higher under spruce whereas Mg, extractable P and mineralizable N did not differ between the species. Forest floor pH was higher under spruce but mineral soil pH did not differ between the species. The soil characteristics reflected litter chemistry of the two species. Relative to pine, spruce foliage litter was consistently higher in nutrient concentration and had lower acidity and higher ash bases. The results are inconsistent with the reputation of Norway spruce as a species that strongly acidifies soils, an observation that may be the result of elevated levels of Ca and K in our soils relative to those in other studies where acidification has been observed. This research demonstrates that soil fertility can be altered significantly by tree species effects over the period of a single rotation. Key words: Forest soil fertility, plantation, acidity, forest floor, leaf litter

Description: Liquid hog manure (LHM) addition to soils in corn silage (Zea mays L.) production may benefit microbial activity by providing C and other nutrients. The objective of this study was to compare the effects of a LHM application to that of inorganic fertilizers (IF) on the biological activity of a Le Bras silt loam soil (Humic Gleysol) under continuous corn production and LHM fertilization. Amounts of 0 to 120 m3 LHM ha−1 and 150 N–150 P2O5–150 K2O kg ha−1 were applied to silage corn. The 0- to 15-cm and 15- to 30-cm soil layers were sampled 28 d after the 18th yearly LHM application. The LHM inputs, particularly at 90 m3 ha−1, resulted in higher enzyme activities and microbial biomass C (MBC) than IF or the unamended control in the 0- to 15-cm soil layer. The 90 m3 LHM ha−1 also gave higher microbial biomass N (MBN) than IF in this soil layer. Application of LHM had no effect on the activities of the enzymes studied or on the MBC and MBN contents in the 15- to 30-cm layer. Ammonifier population was highest with 60 m3 LHM ha−1 in both soil layers. Nitrifier population was not affected by LHM in the top soil layer, but was linearly increased by LHM rates in the 15- to 30-cm layer. This study showed that LHM addition may enhance enzyme activities, microbial biomass and the N mineralizer population in the plow layer of a soil in a corn silage monoculture. Key words: Corn, pig slurry, microbial biomass, monoculture, soil enzyme

Description: Agricultural soils often receive annual manure applications over long periods. The objective of this study was to describe the temporal variations of CH4 fluxes during the growing season in an agricultural soil receiving pig slurry for the 19th consecutive year. In mineral-fertilized control plots, CH4 fluxes were small and negative (uptake) during the experiment. Fluxes were also negative in the manured plots except during the first 4 d following slurry application when net emissions were measured. Despite their short duration, these post-application emissions were almost equivalent to the amount of CH4 taken up by these soils during the rest of the snow-free season. Key words: Geenhouse gases, static chamber, methane concentration in soils