Stéphane Daigle

Biomass productivity and wood energy of Salix species after 2 years growth in SRIC fertilized with wastewater sludge

Abstract The energy equivalent of willows in short-rotation intensive culture (SRIC) varies in terms of yield and woody biomass characteristics. Three willow species ( Salix discolor Muhl., Salix petiolaris Smith and Salix viminalis L.) were planted on two sites, well-drained and poorly drained, in two different densities (20 000 and 30 000 plants per ha). Four doses of dried and granulated sludge were applied: the equivalents of 0, 100, 200 and 300 kg “available” N per ha. At the end of the second season, above-ground biomass was similar for S. discolor and S. viminalis , and greater than that of S. petiolaris on both sites and for all sludge treatments. On the well-drained site, each increment in the sludge dose significantly increased the performance of the species, regardless of plant density. Fertilized with a sludge dose equivalent to 300 kg N per ha, S. viminalis and S. discolor yielded 30.17 and 24.97 t/ha of dry matter respectively. On the poorly drained site, differences in performance were also observed between fertilized and unfertilized plots, but not among the various treatments. The calorific value of the wood of the three species being similar (19.21–19.59 kJ/g), the energy equivalent of a hectare of willows is proportional to the yield of each species. Thus the energy equivalent of S. viminalis and S. discolor is two to three times that of S. petiolaris. S. viminalis had the highest woody biomass quality, with an FVI (fuelwood value index) of 1030.58 (100%), followed by S. petiolaris with 954.25 (92.6%) and S. discolor with 849.08 (82.4%).

Effect of wastewater sludge on growth and heavy metal bioaccumulation of two Salix species

Fast-growing tree species, such as willows, can benefit from sludge application. While sludges are good fertilizers, they may contain heavy metals which could reduce productivity and cause environment risks. The aims of the present research were to: i) determine the biomass production of Salix discolor Mühl. and Salix viminalis L. when supplied with various amounts of dried and pelleted sludge and ii) assess the uptake and accumulation of heavy metals. Trials were carried out using unrooted cuttings that were planted in large plastic pots containing sandy soil and grown outdoors for a 20-week period. Five doses of sludge were applied: the equivalents of 0 (T0), 40 (T1), 80 (T2), 120 (T3), 160 (T4) and 200 (T5) kg “available” N ha-1. Trees which received the highest dosage of sludge showed the best growth. Stem biomass was significantly greater for S. viminalis which had received sludge treatments. The relationship between the total biomass yield Y (g) and the rate of fertilization X (equivalent to kg of “available” nitrogen provided per hectare) is linear. Regression equations of predicted biomass production were established as follows: S. discolor, Y=28.36+0.56X and S. viminalis, Y=39.95+0.64X. For both species, the greatest stem biomass per g of N applied was produced with treatment 4 and 5. Amounts of nitrogen per leaf area (N/LA) and per dry leaf mass (N/DL) were higher for S. viminalis. The metal transfer coefficient did not vary between the species but was significantly different for Cd and Zn. Plants were able to absorb Cd and Zn, but were less able to absorb Ni, Hg, Cu, and Pb. It was concluded that the dried and pelleted sludge is a good fertilizer. S. discolor and particularly S. viminalis can be used as filters for the purification of wastewater sludge as well as for biomass production purposes. R F Huettl Section editor

Effects of wastewater sludge and woodchip combinations on soil properties and growth of planted hardwood trees and willows on a restored site

Abstract Sludge from wastewater treatment plants and woodchips produced from urban tree pruning residues were used to improve soil conditions of a degraded site restored by planting trees and shrubs. The release of soil nitrogen resources was set by the proportions of sludge and woodchips applied. Combining 187 kg N/ha of sludge in one application with 200 m3/ha of woodchips instead of 100 m3/ha reduced first year N mineralization by 50%. The same can be said for the application of 125 kg N/ha of sludge in two applications, over 2 years. The degradation of sludge–woodchips and nitrate leaching was reduced even with the smallest sludge application. Survival and growth of Acer saccharinum L., Fraxinus pennsylvanica Marsh. and Salix discolor Muhl. did not vary much with sludge and woodchips quantities. However, differential soil nitrogen availability and the degradation process of organic amendments induced by the treatments may result in better sustainable growth for planted woody species. Some undesirable elements were measured in the soil, particularly Fe, Cd, Pb and NO3–N. Because of these, care should be taken when choosing sites to be restored using sludge and woodchips.

Growth patterns and biomass productivity of two Salix species grown under short-rotation intensive culture in southern Quebec

Samples of two species of Salix, Salix discolor, which grows naturally in the northern half of North America and S. viminalis, which originated from central Europe, were studied to compare their productivity and their growth patterns under the short-rotation, intensive-culture system (SRIC). The study was conducted in the nursery of the Montreal Botanical Garden on former agricultural land. The plantation was established at a density of 27,000 trees per hectare from unrooted cuttings without any fertilizer or irrigation. Growth parameters were measured at regular intervals during summer of the two first years following planting. At the end of each growing season, after leaf drop, a part of each plot was cut down and the stems and branches were harvested and weighed to evaluate their annual growth rates and their biomass yields. For the first growing season, height growth in both species was greater than 2 m. Although S. viminalis grew more rapidly early in summer, S. discolor grew about three weeks longer and its total height at the end of the growing season was greater than the former. Meanwhile the stem-branch dry weight of S. discolor was similar to the one produced by S. viminalis. Two growing seasons after establishment, the total tree height was about 3.5 m for both species, while the biomass of stems and branches of S. viminalis was weakly superior in comparison to S. discolor and reached very high values-about 27 Mg ha−1 for S. viminalis. The growth patterns and yields of the one-year-old coppice (one-year-cycle) were similar to those recorded at the end of the first year for trees developed directly from cuttings. Both species produced a comparable quantity of sprout biomass. The yield of the trees harvested two years after planting was about twice the total biomass harvested two times, at the end of each growing season, suggesting that a two-year cycle is more productive than a one-year cycle.

Improving hardwood afforestation success: an analysis of the effects of soil properties in southwestern Quebec

Abstract Seven hardwood tree species, planted over five different soil types on abandoned farmland sites of southwestern Quebec, and free of competition for light and soil resources, are assessed (at 7 years) in order to identify soil properties associated with their successful establishment and growth. Best red oak and bur oak “live stem growth” (height or diameter of surviving trees only) occurred on soils derived from non-dolomitic parent material (less alkaline). “Total red oak growth” (height or diameter weighted to include mortality effect by dividing by initial number of trees) was reduced with higher soil water content. Mean soil water content was positively associated to live stem growth of red ash and black walnut, and negatively related to total white ash growth. Analyses of white ash also indicated that highest “total tree diameter” (diameter weighted to include mortality) was positively associated with soil nitrification. Best white ash growth was attained where lower foliar concentrations of nitrogen and phosphorus were measured, thus raising the question of long term growth advantage on these soils. High soil nitrogen mineralization was important in producing high mean live stem growth of black walnut and butternut. Species which can maximize productivity on each soil type were identified to improve afforestation success on former farmland.

Use of Mixtures of Allelochemicals to Compare Bioassays Using Red Maple, Pin Cherry, and American Elm

Toxicity threshold levels for five different bioassays (germination in combination with radicle length, seedling growth, callus growth, plating, and cell suspension growth) were determined on three invasive arborescent species [American elm (Ulmus americana), red maple (Acer rubrum), and pin cherry (Prunus pensylvanica)] using two different mixtures of allelochemicals. Thresholds for the duckweed (Lemna minor) bioassay and lettuce (Lactuca sativa) seed germination bioassay were also determined for comparison with the same mixtures. All five bioassays showed a sensitivity similar to those of duckweed and lettuce bioassays. The lowest sensitivity was in mixtures containing about 5000 μg/liter of each chemical, but the species tested and the mixture applied influenced the outcome. Some bioassays could not be used with red maple (plating and cell suspension) and pin cherry (germination and seedling growth). Cell suspension growth was the most sensitive in in vitro culture, whereas callus culture was the least sensitive. Cell suspension growth in multiwell culture plates should be favored in allelopathy studies because of its sensitivity and the need for relatively small volumes of sample. Detection of phytotoxicity using whole plant systems (germination and seedling growth) and tissue culture appeared not to be directly correlated. We conclude that using many bioassays produces the most conclusive evidence of allelopathic activity.