The Future Forest Ecosystems Scientific Council (FFESC) was created in 2008 following a one-time ... more The Future Forest Ecosystems Scientific Council (FFESC) was created in 2008 following a one-time allocation of funding from the BC provincial government to support research that would inform adaptation of BC’s current forest management policies to a changing climate. A key goal of the council was to maximize the utility of the research to inform provincial policy. The eightstep process that we developed to achieve this goal is described in this paper. In roughly chronological order, the eight steps were: determining the research needed to inform policy, connecting scientists and policy-makers, requiring interdisciplinary teams including both natural and social scientists and relevant stakeholders, assessing proposals for their value to inform policy, fostering scientific excellence, fostering ongoing communication between scientists and policy-makers, tailoring communication to policy-makers, and disseminating the policy-relevant outcomes in a timely and targeted manner. Based on the FFESC experience, we suggest best practices for engaging policy-makers in research and scientists in policy development and adaptation.
Foliose lichens with cyanobacterial bionts (bipartite and tripartite) form a distinct assemblage ... more Foliose lichens with cyanobacterial bionts (bipartite and tripartite) form a distinct assemblage of epiphytes strongly associated with humid microclimatic conditions in inland British Columbia. Previous research showed that these cyano-and cephalolichen communities are disproportionately abundant and species-rich on conifer saplings beneath Populus compared to beneath other tree species. More revealing, lichens with cyanobacterial bionts were observed beneath Populus even in stands that did not otherwise support them. We experimentally test the hypothesis that this association is due to the interception of glucoserich nectar that is exuded from Populus extra-floral nectaries (EFN). Using CO 2 flux measurements and phospholipid fatty acid (PLFA) analysis with experimental applications of 13 C 6-labeled glucose, we demonstrate that cyano-and cephalolichens have a strong respiratory response to glucose. Lichens treated with glucose had lower net photosynthesis and higher establishment rates than control thalli. Furthermore, lichens with cyanobacterial bionts rapidly incorporate exogenous 13 C into lichen fatty acid tissues. A large proportion of the 13 C taken up by the lichens was incorporated into fungal biomarkers, suggesting that the mycobiont absorbed and assimilated the majority of applied 13 C 6 glucose. Our observations suggest that both cyanolichens and cephalolichens may utilize an exogenous source of glucose, made available by poplar EFNs. The exogenous C may enable these lichens to become established by providing a source of C for fungal respiration despite drought-induced inactivity of the cyanobacterial partner. As such, the mycobiont may adopt an alternative nutritional strategy, using available exogenous carbon to extend its realized niche.
Forest floor samples from a 25-year-old plantation of three tree species (Douglas-fir (Pseudotsug... more Forest floor samples from a 25-year-old plantation of three tree species (Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.), and paper birch (Betula papyrifera Marsh.)) growing on the same site were incubated (aerobically) in the laboratory for 29 days. Rates of N mineralization in the forest floors of Douglas-fir (165.1 µg/g) was significantly greater than either birch (72.9 µg/g) or lodgepole pine (51.2 µg/g). Douglas-fir forest floors also had the highest N concentration, lowest C/N ratio, and highest NH 4-N concentrations, followed by paper birch and lodgepole pine. Douglas-fir forest floors also mineralized more N per unit of either N or C than the other species. There were no differences in rates of CO 2-C mineralization in forest floors among the three species. Nitrogen mineralization rates were positively correlated with the N concentration of the forest floor (r 2 = 0.81) and also with the C/N and NH 4-N concentration of the forest floor. Nitrogen concentration, C/N, and lignin/N of foliar litter were poor predictors of N mineralization rates resulting from Douglas-fir litter having the lowest N concentrations in litter but the highest rates of net N mineralization in the forest floor. Nitrogen mineralization in the forest floor was negatively correlated (r 2 = 0.67) with the lignin concentration in foliar litter. Douglas-fir litter had low lignin concentrations, which may allow more of the mineralized N to remain in inorganic forms rather than being bound in humus. Our results suggest that a component of Douglas-fir might improve N availability in coniferous forest floors. Résumé : Des échantillons de la couverture morte prélevés dans une plantation âgée de 25 ans, où croissent sur le même site trois espèces d'arbres, le douglas de Menzies (Pseudotsuga menziesii (Mirb.) Franco), le pin lodgepole (Pinus contorta Dougl. var. latifolia Engelm.) et le bouleau blanc (Betula papyrifera Marsh.), ont été incubés en condition aérobique au laboratoire pendant 29 jours. Le taux de minéralisation de N dans la couverture morte du douglas de Menzies (165,1 µg/g) était significativement plus élevé que ceux de la couverture morte du bouleau (72,9 µg/g) ou du pin lodgepole (51,2 µg/g). La couverture morte de douglas de Menzies avait également la concentration en azote la plus élevée, le plus faible rapport C/N et la concentration en N-NH 4 la plus élevée suivi du bouleau blanc et du pin lodgepole. La couverture morte de douglas de Menzies minéralisait également plus de N par unité de N ou de C que celle des autres espèces. Il n'y avait pas de différence dans le taux de minéralisation de C-CO 2 entre les couvertures mortes des trois espèces. Le taux de minéralisation de N était positivement corrélé avec la concentration de N dans la couverture morte (r 2 = 0,81) et également avec le rapport C/N et la concentration de N-NH
The contribution of coarse woody debris to C, N, and P cycles was assessed in forests of lodgepol... more The contribution of coarse woody debris to C, N, and P cycles was assessed in forests of lodgepole pine (Pinus contorta Dougl. ex Loud.), white spruce (Picea glauca (Moench Voss), and subalpine fir (Abies lasiocarpa (Hook.) Nutt.)-Engelmann spruce (Picea engelmannii Parry ex Engelm.) in southwestern Alberta. Mass loss and changes in C, N, and P concentrations in decomposing log segments were measured for 14 years. Litter input was measured during 10 years for coarse woody debris, 1 year for ground vegetation, and 5 years for other aboveground litter types. Release of C, N and P from decomposing litter were simulated for a period of 40 years. After 14 years, log segments of pine, spruce, and fir had lost on average 71, 38, and 40%, respectively, of their dry mass. The N content of the pine logs increased, spruce changed little, and fir lost N. Phosphorus accumulated in all logs. The greatest imports of N and P occurred at the pine sites and fir sites, respectively, where these nutrients were the least available, indicating that wood decay organisms may compete with vegetation for limiting nutrients in these forests. Coarse woody debris comprised 3-24% of aboveground litter and contributed less than 5% of the N and P released. Coarse woody debris does not appear to make a significant contribution to N and P cycling in these forests. Résumé : La contribution des débris ligneux grossiers aux cycles de C, N et P a été évaluée dans des forêts de pin lodgepole (Pinus contorta Dougl. ex Loud.), d'épinette blanche (Picea glauca (Moench) Voss) et de sapin subalpin (Abies lasiocarpa (Hook.) Nutt.)-épinette d'Engelmann (Picea engelmannii Parry ex Engelm.) dans le sud-ouest de l'Alberta. La perte de masse et les changements dans les concentrations de C, N et P dans des segments de billes au sol en décomposition ont été mesurés pendant 14 ans. L'apport de litière a été mesuré pendant 10 ans dans le cas des débris ligneux grossiers, 1 an dans le cas de la végétation au sol et 5 ans dans le cas des autres types de litière épigée. La libération de C, N et P dans la litière en décomposition a été simulée pour une période de 40 ans. Après 14 ans, les segments de billes au sol de pin, d'épinette et de sapin avaient perdu en moyenne respectivement 71, 38 et 40% de leur masse sèche. Le contenu en N des billes de pin a augmenté, il a peu changé chez l'épinette et a diminué chez le sapin. Le contenu en phosphore a augmenté dans toutes les billes. Les plus fortes importations de N et de P sont survenues respectivement dans les sites avec pin et dans les sites avec sapin, là où ces nutriments étaient les moins disponibles, ce qui indique que les organismes responsables de la décomposition du bois sont probablement en compétition avec la végétation pour les nutriments qui sont déficients dans ces forêts. Les débris ligneux grossiers représentaient 3 à 24% de la litière épigée et contribuaient moins de 5% de N et de P rendus disponibles. Les débris ligneux grossiers ne semblent pas apporter une contribution significative au cyclage de N et P dans ces forêts.
The effects of increased exogenous N availability on rates of litter decomposition were assessed ... more The effects of increased exogenous N availability on rates of litter decomposition were assessed in several field fertilization trials. In a jack pine (Pinus banksiana Lamb.) forest, needle litter decomposed at the same rate in control plots and in plots fertilized with urea and ammonium nitrate (1350 kg N ha-I) with or without P and K. Mixed needle litter of western hemlock (Tsuga heterophylla (Raf.) Sarg.), western red cedar (Thuja plicata Donn) and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) incubated in plots recently amended with sewage sludge (500 kg N ha-I) lost less weight during 3 years than did litter in control plots. Forest floor material also decomposed more slowly in plots amended with sewage sludge. Paper birch (Betula papyrijera Marsh.) leaf litter placed on sewage sludge (1000 kg N ha-I), pulp sludge, or sewage-pulp sludge mixtures decomposed at the same rate as leaf litter in control plots. These experiments demonstrate little effect of exogenous N availability on rates of litter decomposition. The influence of endogenous N availability on rates of litter decomposition was examined in a microcosm experiment. Lodgepole pine (Pinus contorta var. latijolia Engelm.) needle litter collected from N-fertilized trees (525 kg N ha-I in ammonium nitrate) were 5 times richer in N than needles from control trees (l.56% N versus 0.33~ N in control trees), but decomposed at the same rate. Green needles from fertilized trees contained twice as much N as needles from control trees (l.91 % N versus 0.88% N), but decomposed at the same rate. These experiments suggest that N availability alone, either exogenous or endogenous, does not control rates of litter decomposition. Increased N availability, through fertilization or deposition, in the absence of changes in vegetation composition, will not alter rates of litter decomposition in forests.
Forest fragmentation is increasing rapidly around the world, and edge effects caused by fragmente... more Forest fragmentation is increasing rapidly around the world, and edge effects caused by fragmented forests can influence ecosystem functions and ecological processes, including coarse woody debris (CWD) decomposition. Understanding the influencing mechanisms of edge effect on CWD decomposition is needed to assess the effects of forest fragmentation on C cycling and storage. We measured rates of mass loss of CWD of Cinnamomum camphora and Pinus taiwanensis over two years at two distances (0-5m vs. 60m) from a forest edge at two altitudes (215 and 1400 m a.s.l.), in a subtropical forest. In addition, we determined the microbial community of each CWD and the soil beneath via phospholipid fatty acids (PLFAs). Mass loss of CWD 60 m from the forest edge was > 15 % greater than that at the edge (0-5m). Mass loss was positively correlated with the abundance of microbial community and moisture content of the decaying CWD. Distance from edge explained 17.4% of the total variation of the microbial abundance in CWD. The results indicated that the reduced abundance of microbial communities and moisture content at forest edges reduced rates of decomposition of CWD. Long-term experiments with more tree species and more forest types are needed to assess the edge effect's generality.
Connecting ecological science and management in forests for scientists, managers and pocket scien... more Connecting ecological science and management in forests for scientists, managers and pocket scientists 1. Introduction The structures, patterns, and processes of the forests of the world develop from ecological interactions among hugely diverse types of organisms interacting with environmental factors at specific places and times on the Earth's surface. The science of ecology helps us develop frameworks for understanding these structures, patterns and processes, leading to descriptive studies and experiments that increase our insights into the nature of forests across space and time. Forest management changes the structure, patterns, and processes of forests, produce goods and services for people. These activities may be informed by scientific insights, though forest management has a much longer history than ecological science. Modern forest management relies heavily on insights from ecological science. Management approaches may call for the use of "the best available science," but the dynamics of real forests may not be very deterministic and more flexible views of science and management may be productive (cf. Aplet and McKinley, 2017, Matonis et al., 2017). Various simple characterizations might represent the classical framework of ecological insight informing forest management (Fig. 1). In this Editors Note from the IUFRO Regional Congress for Asia and Oceania in Beijing in 2016, we suggest that a more effective framing is possible, where science and management are developed in interacting, powerful ways. We develop these ideas with two examples where science was used to inform management, and then flip the direction with two examples of how landscape-scale managed forests led to improved scientific understanding. The idea of "pocket science" is developed as an explicit approach that helps forest managers pull science and management together at the scale of forest operations, enhancing both understanding and management. 2. Classic science experimental design Forest research often uses classical experimental designs with treatments applied to replicate plots within a single stand. The choice of locating all replicates (degrees of freedom) stems from a desire to minimize variation among plots, allowing the signal of the treatment response to be detected more clearly. Insights from these experiments may apply to other forests and other times if other ecological factors do not interact with the factors examined in the classic experimental design. 2.1. Biogeochemistry in fast-growing Eucalyptus plantations Highly productive plantations Eucalyptus species are commonly established on low-fertility soils, and large nutrient exports at the harvest every 6-7 years pose a challenge for sustainability (Gonçalves et al., 2013). Large amounts of fertilizers are applied to increase nutrient supply and countered losses in forest harvest (Stape et al., 2006, 2010). How does the addition of fertilizers change the cycling of elements in forests and soils? Are the added nutrients retained in the soil, in the trees, or lost by leaching during the rainy seasons? How long after fertilization are rates of nutrient cycling increased? How variable would these responses be around the world? The scientific curiosity behind these questions has led to experiments that may be quite valuable for sustaining high growth rates in plantations. Matching fertilization regimes to tree requirements requires improving our understanding of the biogeochemical processes controlling the dynamics of nutrient availability in soils. Comprehensive studies have been carried out in the Congo and in Brazil for contrasting nutrient supplies to quantify the main fluxes of N, P, K, Ca and Mg at the scale of the ecosystem in Eucalyptus plantations, from planting to harvesting (for details, see Laclau et al., 2010). These plantations are typically established on very deep soils, and Eucalyptus roots descend deep into the soil almost at the rate the crowns rise into the air. Soil mineralogy as well as the main soil physical and chemical properties have been characterized down to depths > 5 m. Nutrient accumulation in the trees, nutrient returns to soil with litterfall and nutrient releases during litter decomposition were also measured throughout stand rotation. Moreover, the nutrient fluxes dissolved in gravitational solutions were quantified to assess the losses by deep drainage after clear-cutting and to provide practical recommendations for the fertilization regimes. Strong differences in soil, climate, eucalypt species and silvicultural practices between the commercial eucalypt plantations at the two sites led to much higher productivities in Brazil (about 50 m 3 ha −1 yr −1) than in the Congo (about 20 m 3 ha −1 yr −1). Although the soils in both locations was predominantly sand (90% sand in the Congo, 75-80% sand in Brazil), nutrient losses in deep drainage were very low at the two sites (lower than atmospheric deposition). The largest fluxes of nutrients deep into the soil came when the previous stands were clearcut, and post-logging residues as
The contribution of coarse woody debris (CWD) to carbon, nitrogen, and phosphorus cycles was asse... more The contribution of coarse woody debris (CWD) to carbon, nitrogen, and phosphorus cycles was assessed in forests of lodgepole pine, white spruce-lodgepole pine, and subalpine fir-Engelmann spruce in southwestern Alberta. Mass loss and changes in C, N, and P concentrations in decomposing log segments were measured over a 14-year period. Organic matter input was measured during 10 years for CWD, 1 year for ground vegetation, and 5 years for other aboveground litter types. Carbon, N, and P release from decomposing litter were simulated for a period of 40 years to determine the relative contributions of each aboveground litter type, including CWD. After 14 years, pine log segments had lost 71 percent of their dry mass; spruce and fir lost 38 percent and 40 percent, respectively. The nitrogen (N) content of the logs increased in pine, changed little in spruce, and decreased by almost 30 percent in fir logs. Phosphorus (P) accumulated in decaying log segments of all three species, especially fir logs in which the P content was nearly five times the initial content after 14 years. Tree species with the lowest initial concentration had the greatest relative accumulation. Thus, wood decay organisms may compete with vegetation for limiting nutrients in these forests. The proportion of coarse woody debris (CWD) in aboveground litter input was 19 percent at the pine site, 3 percent at the spruce site, and 24 percent at the fir site. The contribution of CWD to N and P release was 2 percent or less, except at the fir site where CWD released 5 percent of the N. Coarse woody debris does not appear to make a significant contribution to N and P cycling in these forests.
A pervasive belief in soil ecology is that consumption and gut passage of litter by soil macro-ar... more A pervasive belief in soil ecology is that consumption and gut passage of litter by soil macro-arthropods, such as earthworms, millipedes, myriapods, diplopods and various insect larvae (also referred
A factorial thinning and fertilization experiment was established in central British Columbia in ... more A factorial thinning and fertilization experiment was established in central British Columbia in a 36-year-old high-density fire-origin lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) stand to examine the effects of density, nutrition, and their interaction on tree and stand growth, foliage biomass per hectare, and growth efficiency. Volume growth was increased from 2 to 7 m3·ha1·year1 when fertilizer was applied without thinning and to 5 m3·ha1·year1 when fertilizer was applied with thinning. Thinning increased tree-level foliage biomass and growth efficiency by concentrating limited resources onto fewer trees, resulting in increased tree-level volume growth. Stand-level volume growth was reduced by thinning because of the large reduction in stocking. However, by year 4, stand-level volume growth was the same on control and thinned plots, suggesting that thinned trees have already recaptured the site potential. Fertilization increased both tree-level and stand-level productivity through increases in resource availability per tree and per hectare. This resulted in increased foliage biomass and growth efficiency at the tree and stand level. The combination of thinning and fertilization resulted in the greatest tree-level growth because of increased tree-level foliage biomass and growth efficiency. Boron appears to be the most limiting element followed by sulfur and nitrogen.
Scarification is a widely used silviculture method and is suggested to improve organic matter dec... more Scarification is a widely used silviculture method and is suggested to improve organic matter decomposition rate. In this study, I made the use of an experiment that buried humus material into mineral soil after clear-cuts and studied its effects on humus decomposition rate in four biogeoclimatic zones (CWH, ESSF, ICH and IDF) in British Columbia. Litterbags containing local humus materials (mixture of F and H layers) were placed on the forest floor surface or buried in the soil (5-10 cm deep). Samples were retracted annually and dry mass and carbon (C) content were measured to calculate the remaining C mass in each sample for three continuous years. The remaining C mass at all of four sites was lower when buried than placed on the surface, but the difference was significant only at the drier IDF site. Humus in forests with better climatic conditions, such as abundant precipitation and suitable temperature, responded weakly to burying. Stimulation of humus decomposition through scarification is most likely to occur in dry forests in B.C.
Prescott, C. E. 2014. The scientific value of long-term field trials in forest soils and nutritio... more Prescott, C. E. 2014. The scientific value of long-term field trials in forest soils and nutrition research: An opportunist's perspective. Can. J. Soil Sci. 94: 255–262. Long-term field trials are essential in allowing accurate prediction of stand responses to silvicultural treatments. Less well appreciated is the added value that long-term field trials afford to science through a variety of means, often not included in the original experimental plan. Long-term field trials provide a platform upon which additional studies can be conducted; for example a suite of alternative silvicultural trials allowed assessment of influences of forest harvesting on rates of litter decomposition. Well-designed, long-term field trials can be re-purposed to address questions not related to the original research; for example, many of the common garden experiments used to discern influences of different tree species on soil were not originally intended for this purpose. Long-term trials may reveal effects on other ecosystem components such as understorey vegetation or soil organisms, which can generate new hypotheses about ecosystem functioning. Finally, including unusual or non-operational treatments can generate insights that would not occur where trials were constrained to current operational practices. Improved accounting of the additional scientific insights afforded by long-term field trials would go some way towards improved accounting of their true value to science.
Fish-wood compost and wheat straw were applied to chlorotic plantations of western redcedar (Thuj... more Fish-wood compost and wheat straw were applied to chlorotic plantations of western redcedar (Thuja plicata Donn ex D. Don) on northern Vancouver Island to determine their effectiveness as fertilizers. Two years after application, tree growth was greater in the compost-and straw-amended plots than in control plots. The greatest growth response was in straw-amended plots. The first year after application, foliar concentrations of N, P, K, and S were higher in trees in the straw and compost plots. Two years after treatment, foliar nutrient concentrations returned to pretreatment levels in the compost plots, but remained elevated in the straw plots. Concentrations of KCl-extractable N in forest floors 2 years after treatment were greater in the straw plots than in the control plots prior to and after a 29-day incubation. The rate of CO 2 evolution from the forest floor was also greatest in the straw plots 2 years after treatment. These results suggest that addition of a fresh residue such as straw to these sites may promote a long-term increase in N availability and tree growth. Résumé : Un compost de poisson ou de bois ainsi que de la paille de blé furent appliqués dans des plantations chlorotiques de thuya géant (Thuja plicata Donn ex D. Don) établies dans la partie nord de l'île de Vancouver afin d'évaluer leur efficacité comme fertilisants. Deux ans après l'application, la croissance des arbres était plus forte dans les parcelles amendées avec le compost ou la paille. La plus forte croissance est survenue dans les parcelles amendées avec la paille. La première année après l'application, les concentrations foliaires de N, P, K et S étaient plus élevées dans les parcelles traitées avec le compost ou la paille. Deux ans après le traitement, la concentration foliaire des nutriments est revenue au niveau antérieur au traitement dans les parcelles traitées avec le compost mais elle est demeurée élevée dans les parcelles traitées avec la paille. La concentration de N extractible au KCl dans la couverture morte, 2 ans après le traitement, était plus élevée dans les parcelles traitées avec la paille que dans les parcelles témoins avant et après une période d'incubation de 29 jours. Le taux d'évolution du CO 2 dans la couverture morte était également plus élevé dans les parcelles traitées avec la paille 2 ans après son application. Ces résultats suggèrent que l'addition dans ces sites de résidus non décomposés tels que la paille peut amener une augmentation à long terme de la disponibilité de N et de la croissance des arbres. [Traduit par la Rédaction]
We tested several hypotheses to explain the superior growth and nitrogen (N) status of lodgepole ... more We tested several hypotheses to explain the superior growth and nitrogen (N) status of lodgepole pine (Pinus contorta Dougl. ex Laws. var. contorta) compared with Sitka spruce (Picea sitchensis (Bong.) Carrière) on a N-poor site by comparing N distribution, N retranslocation, rooting distribution, and mycorrhizal fungi in plots of 11-year-old trees on a cedar-hemlock cutover. Aboveground N content was nine times greater in pine than in spruce of the same age, and thus, we conclude that pine acquired more N during the 11 years than spruce. Greater N acquisition by pine was not related to rooting depth, as both species rooted primarily in the residual forest floor. There were differences in mycorrhizal fungal associates: a high proportion of pine roots were infected with Suillus-like fungi. Pine produced more aboveground biomass per unit N (388 compared with 292 g•g-1 in spruce) and distributed more N to young foliage. Nitrogen retranslocation efficiency (based on foliar N contents in July and October) was higher in pine (50-52%) than in spruce (24-36%). These characteristics all appear to contribute to pine's abilities to both acquire more N and use it more efficiently and, thus, outperform spruce on this N-poor site. Résumé : Nous avons testé plusieurs hypothèses pour expliquer pourquoi le pin lodgepole (Pinus contorta Dougl. ex Laws. var. contorta) a une meilleure croissance et un meilleur bilan de l'azote (N) que l'épinette de Sitka (Picea sitchensis (Bong.) Carrière) sur un site pauvre en N. Des parcelles ont été établies dans un peuplement de cèdre et de pruche coupé à blanc où les arbres étaient âgés de 11 ans afin de comparer la distribution de N, la translocation de N, la distribution des racines et les champignons mycorhiziens. Le contenu en azote épigé était neuf fois plus élevé chez le pin que chez l'épinette du même âge. Par conséquent, nous concluons que le pin a emmagasiné plus de N que l'épinette au cours des onze années de croissance. La plus forte accumulation de N par le pin n'était pas liée à la profondeur de l'enracinement car le système racinaire des deux espèces se développait principalement dans la couverture morte résiduelle. Les champignons mycorhiziens associés aux deux espèces étaient différents. Une forte proportion des racines de pin étaient infectées par des champignons apparentés à Suillus. Le pin produisait plus de biomasse épigée par unité de N (388 comparativement à 292 g•g-1 pour l'épinette) et distribuait davantage de N vers le jeune feuillage. L'efficacité de la translocation de N, basée sur le contenu en N en juillet et octobre, était plus élevée chez le pin (50-52%) que chez l'épinette (24-36%). Ces caractéristiques semblent toutes contribuer à l'acquisition de plus de N et à son utilisation plus efficace par le pin qui déclasse l'épinette sur ce site pauvre. [Traduit par la Rédaction] Bothwell et al. 1279
Vegetation plays an important role in determining soil organic carbon (SOC) stocks, and influence... more Vegetation plays an important role in determining soil organic carbon (SOC) stocks, and influences the mechanisms through which SOC is stabilized within the soil. The type of vegetation selected for use in reclamation may therefore influence the accumulation rate and residence time of SOC in these ecosystems. Earlier studies at reclaimed sites in the Alberta Oil Sands demonstrated that reclaimed ecosystems planted with deciduous trees accumulated the most soil organic matter in the top 10 cm of reclamation material, followed by grass sites, while coniferous sites accumulated the least SOM. The objective of this study was to assess differences in SOC stabilization in the upper 10 cm of soil among revegetated deciduous, coniferous and grass ecosystems 20–40 years following reclamation. We compared soil C in unprotected, physically protected, and chemically protected forms among the three reclamation treatments using density flotation to isolate free particulate (unprotected) SOC from ...
Abstract The nature and properties of the soil, along with other site factors such as climate, sl... more Abstract The nature and properties of the soil, along with other site factors such as climate, slope position, elevation, and aspect, determine the availability of water and nutrients to plants and therefore influence the success of forest restoration programs. Characteristics of the soil therefore warrant careful consideration when estimating the potential of a site for afforestation or reforestation. Many sites being considered for forest landscape restoration have soils that have been degraded through various human activities, which will need to be rehabilitated as part of the restoration process. Characteristics of degraded soils include loss of structure and organic matter, susceptibility to erosion by wind or water, diminished aeration and water-holding capacity, insufficient or excess nutrient supply, excess acidity or salinity, and diminished soil biota. In this chapter, we discuss each of these impairments and the restoration practices that can be applied to rehabilitate degraded soils.
The Future Forest Ecosystems Scientific Council (FFESC) was created in 2008 following a one-time ... more The Future Forest Ecosystems Scientific Council (FFESC) was created in 2008 following a one-time allocation of funding from the BC provincial government to support research that would inform adaptation of BC’s current forest management policies to a changing climate. A key goal of the council was to maximize the utility of the research to inform provincial policy. The eightstep process that we developed to achieve this goal is described in this paper. In roughly chronological order, the eight steps were: determining the research needed to inform policy, connecting scientists and policy-makers, requiring interdisciplinary teams including both natural and social scientists and relevant stakeholders, assessing proposals for their value to inform policy, fostering scientific excellence, fostering ongoing communication between scientists and policy-makers, tailoring communication to policy-makers, and disseminating the policy-relevant outcomes in a timely and targeted manner. Based on the FFESC experience, we suggest best practices for engaging policy-makers in research and scientists in policy development and adaptation.
Foliose lichens with cyanobacterial bionts (bipartite and tripartite) form a distinct assemblage ... more Foliose lichens with cyanobacterial bionts (bipartite and tripartite) form a distinct assemblage of epiphytes strongly associated with humid microclimatic conditions in inland British Columbia. Previous research showed that these cyano-and cephalolichen communities are disproportionately abundant and species-rich on conifer saplings beneath Populus compared to beneath other tree species. More revealing, lichens with cyanobacterial bionts were observed beneath Populus even in stands that did not otherwise support them. We experimentally test the hypothesis that this association is due to the interception of glucoserich nectar that is exuded from Populus extra-floral nectaries (EFN). Using CO 2 flux measurements and phospholipid fatty acid (PLFA) analysis with experimental applications of 13 C 6-labeled glucose, we demonstrate that cyano-and cephalolichens have a strong respiratory response to glucose. Lichens treated with glucose had lower net photosynthesis and higher establishment rates than control thalli. Furthermore, lichens with cyanobacterial bionts rapidly incorporate exogenous 13 C into lichen fatty acid tissues. A large proportion of the 13 C taken up by the lichens was incorporated into fungal biomarkers, suggesting that the mycobiont absorbed and assimilated the majority of applied 13 C 6 glucose. Our observations suggest that both cyanolichens and cephalolichens may utilize an exogenous source of glucose, made available by poplar EFNs. The exogenous C may enable these lichens to become established by providing a source of C for fungal respiration despite drought-induced inactivity of the cyanobacterial partner. As such, the mycobiont may adopt an alternative nutritional strategy, using available exogenous carbon to extend its realized niche.
Forest floor samples from a 25-year-old plantation of three tree species (Douglas-fir (Pseudotsug... more Forest floor samples from a 25-year-old plantation of three tree species (Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), lodgepole pine (Pinus contorta Dougl. var. latifolia Engelm.), and paper birch (Betula papyrifera Marsh.)) growing on the same site were incubated (aerobically) in the laboratory for 29 days. Rates of N mineralization in the forest floors of Douglas-fir (165.1 µg/g) was significantly greater than either birch (72.9 µg/g) or lodgepole pine (51.2 µg/g). Douglas-fir forest floors also had the highest N concentration, lowest C/N ratio, and highest NH 4-N concentrations, followed by paper birch and lodgepole pine. Douglas-fir forest floors also mineralized more N per unit of either N or C than the other species. There were no differences in rates of CO 2-C mineralization in forest floors among the three species. Nitrogen mineralization rates were positively correlated with the N concentration of the forest floor (r 2 = 0.81) and also with the C/N and NH 4-N concentration of the forest floor. Nitrogen concentration, C/N, and lignin/N of foliar litter were poor predictors of N mineralization rates resulting from Douglas-fir litter having the lowest N concentrations in litter but the highest rates of net N mineralization in the forest floor. Nitrogen mineralization in the forest floor was negatively correlated (r 2 = 0.67) with the lignin concentration in foliar litter. Douglas-fir litter had low lignin concentrations, which may allow more of the mineralized N to remain in inorganic forms rather than being bound in humus. Our results suggest that a component of Douglas-fir might improve N availability in coniferous forest floors. Résumé : Des échantillons de la couverture morte prélevés dans une plantation âgée de 25 ans, où croissent sur le même site trois espèces d'arbres, le douglas de Menzies (Pseudotsuga menziesii (Mirb.) Franco), le pin lodgepole (Pinus contorta Dougl. var. latifolia Engelm.) et le bouleau blanc (Betula papyrifera Marsh.), ont été incubés en condition aérobique au laboratoire pendant 29 jours. Le taux de minéralisation de N dans la couverture morte du douglas de Menzies (165,1 µg/g) était significativement plus élevé que ceux de la couverture morte du bouleau (72,9 µg/g) ou du pin lodgepole (51,2 µg/g). La couverture morte de douglas de Menzies avait également la concentration en azote la plus élevée, le plus faible rapport C/N et la concentration en N-NH 4 la plus élevée suivi du bouleau blanc et du pin lodgepole. La couverture morte de douglas de Menzies minéralisait également plus de N par unité de N ou de C que celle des autres espèces. Il n'y avait pas de différence dans le taux de minéralisation de C-CO 2 entre les couvertures mortes des trois espèces. Le taux de minéralisation de N était positivement corrélé avec la concentration de N dans la couverture morte (r 2 = 0,81) et également avec le rapport C/N et la concentration de N-NH
The contribution of coarse woody debris to C, N, and P cycles was assessed in forests of lodgepol... more The contribution of coarse woody debris to C, N, and P cycles was assessed in forests of lodgepole pine (Pinus contorta Dougl. ex Loud.), white spruce (Picea glauca (Moench Voss), and subalpine fir (Abies lasiocarpa (Hook.) Nutt.)-Engelmann spruce (Picea engelmannii Parry ex Engelm.) in southwestern Alberta. Mass loss and changes in C, N, and P concentrations in decomposing log segments were measured for 14 years. Litter input was measured during 10 years for coarse woody debris, 1 year for ground vegetation, and 5 years for other aboveground litter types. Release of C, N and P from decomposing litter were simulated for a period of 40 years. After 14 years, log segments of pine, spruce, and fir had lost on average 71, 38, and 40%, respectively, of their dry mass. The N content of the pine logs increased, spruce changed little, and fir lost N. Phosphorus accumulated in all logs. The greatest imports of N and P occurred at the pine sites and fir sites, respectively, where these nutrients were the least available, indicating that wood decay organisms may compete with vegetation for limiting nutrients in these forests. Coarse woody debris comprised 3-24% of aboveground litter and contributed less than 5% of the N and P released. Coarse woody debris does not appear to make a significant contribution to N and P cycling in these forests. Résumé : La contribution des débris ligneux grossiers aux cycles de C, N et P a été évaluée dans des forêts de pin lodgepole (Pinus contorta Dougl. ex Loud.), d'épinette blanche (Picea glauca (Moench) Voss) et de sapin subalpin (Abies lasiocarpa (Hook.) Nutt.)-épinette d'Engelmann (Picea engelmannii Parry ex Engelm.) dans le sud-ouest de l'Alberta. La perte de masse et les changements dans les concentrations de C, N et P dans des segments de billes au sol en décomposition ont été mesurés pendant 14 ans. L'apport de litière a été mesuré pendant 10 ans dans le cas des débris ligneux grossiers, 1 an dans le cas de la végétation au sol et 5 ans dans le cas des autres types de litière épigée. La libération de C, N et P dans la litière en décomposition a été simulée pour une période de 40 ans. Après 14 ans, les segments de billes au sol de pin, d'épinette et de sapin avaient perdu en moyenne respectivement 71, 38 et 40% de leur masse sèche. Le contenu en N des billes de pin a augmenté, il a peu changé chez l'épinette et a diminué chez le sapin. Le contenu en phosphore a augmenté dans toutes les billes. Les plus fortes importations de N et de P sont survenues respectivement dans les sites avec pin et dans les sites avec sapin, là où ces nutriments étaient les moins disponibles, ce qui indique que les organismes responsables de la décomposition du bois sont probablement en compétition avec la végétation pour les nutriments qui sont déficients dans ces forêts. Les débris ligneux grossiers représentaient 3 à 24% de la litière épigée et contribuaient moins de 5% de N et de P rendus disponibles. Les débris ligneux grossiers ne semblent pas apporter une contribution significative au cyclage de N et P dans ces forêts.
The effects of increased exogenous N availability on rates of litter decomposition were assessed ... more The effects of increased exogenous N availability on rates of litter decomposition were assessed in several field fertilization trials. In a jack pine (Pinus banksiana Lamb.) forest, needle litter decomposed at the same rate in control plots and in plots fertilized with urea and ammonium nitrate (1350 kg N ha-I) with or without P and K. Mixed needle litter of western hemlock (Tsuga heterophylla (Raf.) Sarg.), western red cedar (Thuja plicata Donn) and Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) incubated in plots recently amended with sewage sludge (500 kg N ha-I) lost less weight during 3 years than did litter in control plots. Forest floor material also decomposed more slowly in plots amended with sewage sludge. Paper birch (Betula papyrijera Marsh.) leaf litter placed on sewage sludge (1000 kg N ha-I), pulp sludge, or sewage-pulp sludge mixtures decomposed at the same rate as leaf litter in control plots. These experiments demonstrate little effect of exogenous N availability on rates of litter decomposition. The influence of endogenous N availability on rates of litter decomposition was examined in a microcosm experiment. Lodgepole pine (Pinus contorta var. latijolia Engelm.) needle litter collected from N-fertilized trees (525 kg N ha-I in ammonium nitrate) were 5 times richer in N than needles from control trees (l.56% N versus 0.33~ N in control trees), but decomposed at the same rate. Green needles from fertilized trees contained twice as much N as needles from control trees (l.91 % N versus 0.88% N), but decomposed at the same rate. These experiments suggest that N availability alone, either exogenous or endogenous, does not control rates of litter decomposition. Increased N availability, through fertilization or deposition, in the absence of changes in vegetation composition, will not alter rates of litter decomposition in forests.
Forest fragmentation is increasing rapidly around the world, and edge effects caused by fragmente... more Forest fragmentation is increasing rapidly around the world, and edge effects caused by fragmented forests can influence ecosystem functions and ecological processes, including coarse woody debris (CWD) decomposition. Understanding the influencing mechanisms of edge effect on CWD decomposition is needed to assess the effects of forest fragmentation on C cycling and storage. We measured rates of mass loss of CWD of Cinnamomum camphora and Pinus taiwanensis over two years at two distances (0-5m vs. 60m) from a forest edge at two altitudes (215 and 1400 m a.s.l.), in a subtropical forest. In addition, we determined the microbial community of each CWD and the soil beneath via phospholipid fatty acids (PLFAs). Mass loss of CWD 60 m from the forest edge was > 15 % greater than that at the edge (0-5m). Mass loss was positively correlated with the abundance of microbial community and moisture content of the decaying CWD. Distance from edge explained 17.4% of the total variation of the microbial abundance in CWD. The results indicated that the reduced abundance of microbial communities and moisture content at forest edges reduced rates of decomposition of CWD. Long-term experiments with more tree species and more forest types are needed to assess the edge effect's generality.
Connecting ecological science and management in forests for scientists, managers and pocket scien... more Connecting ecological science and management in forests for scientists, managers and pocket scientists 1. Introduction The structures, patterns, and processes of the forests of the world develop from ecological interactions among hugely diverse types of organisms interacting with environmental factors at specific places and times on the Earth's surface. The science of ecology helps us develop frameworks for understanding these structures, patterns and processes, leading to descriptive studies and experiments that increase our insights into the nature of forests across space and time. Forest management changes the structure, patterns, and processes of forests, produce goods and services for people. These activities may be informed by scientific insights, though forest management has a much longer history than ecological science. Modern forest management relies heavily on insights from ecological science. Management approaches may call for the use of "the best available science," but the dynamics of real forests may not be very deterministic and more flexible views of science and management may be productive (cf. Aplet and McKinley, 2017, Matonis et al., 2017). Various simple characterizations might represent the classical framework of ecological insight informing forest management (Fig. 1). In this Editors Note from the IUFRO Regional Congress for Asia and Oceania in Beijing in 2016, we suggest that a more effective framing is possible, where science and management are developed in interacting, powerful ways. We develop these ideas with two examples where science was used to inform management, and then flip the direction with two examples of how landscape-scale managed forests led to improved scientific understanding. The idea of "pocket science" is developed as an explicit approach that helps forest managers pull science and management together at the scale of forest operations, enhancing both understanding and management. 2. Classic science experimental design Forest research often uses classical experimental designs with treatments applied to replicate plots within a single stand. The choice of locating all replicates (degrees of freedom) stems from a desire to minimize variation among plots, allowing the signal of the treatment response to be detected more clearly. Insights from these experiments may apply to other forests and other times if other ecological factors do not interact with the factors examined in the classic experimental design. 2.1. Biogeochemistry in fast-growing Eucalyptus plantations Highly productive plantations Eucalyptus species are commonly established on low-fertility soils, and large nutrient exports at the harvest every 6-7 years pose a challenge for sustainability (Gonçalves et al., 2013). Large amounts of fertilizers are applied to increase nutrient supply and countered losses in forest harvest (Stape et al., 2006, 2010). How does the addition of fertilizers change the cycling of elements in forests and soils? Are the added nutrients retained in the soil, in the trees, or lost by leaching during the rainy seasons? How long after fertilization are rates of nutrient cycling increased? How variable would these responses be around the world? The scientific curiosity behind these questions has led to experiments that may be quite valuable for sustaining high growth rates in plantations. Matching fertilization regimes to tree requirements requires improving our understanding of the biogeochemical processes controlling the dynamics of nutrient availability in soils. Comprehensive studies have been carried out in the Congo and in Brazil for contrasting nutrient supplies to quantify the main fluxes of N, P, K, Ca and Mg at the scale of the ecosystem in Eucalyptus plantations, from planting to harvesting (for details, see Laclau et al., 2010). These plantations are typically established on very deep soils, and Eucalyptus roots descend deep into the soil almost at the rate the crowns rise into the air. Soil mineralogy as well as the main soil physical and chemical properties have been characterized down to depths > 5 m. Nutrient accumulation in the trees, nutrient returns to soil with litterfall and nutrient releases during litter decomposition were also measured throughout stand rotation. Moreover, the nutrient fluxes dissolved in gravitational solutions were quantified to assess the losses by deep drainage after clear-cutting and to provide practical recommendations for the fertilization regimes. Strong differences in soil, climate, eucalypt species and silvicultural practices between the commercial eucalypt plantations at the two sites led to much higher productivities in Brazil (about 50 m 3 ha −1 yr −1) than in the Congo (about 20 m 3 ha −1 yr −1). Although the soils in both locations was predominantly sand (90% sand in the Congo, 75-80% sand in Brazil), nutrient losses in deep drainage were very low at the two sites (lower than atmospheric deposition). The largest fluxes of nutrients deep into the soil came when the previous stands were clearcut, and post-logging residues as
The contribution of coarse woody debris (CWD) to carbon, nitrogen, and phosphorus cycles was asse... more The contribution of coarse woody debris (CWD) to carbon, nitrogen, and phosphorus cycles was assessed in forests of lodgepole pine, white spruce-lodgepole pine, and subalpine fir-Engelmann spruce in southwestern Alberta. Mass loss and changes in C, N, and P concentrations in decomposing log segments were measured over a 14-year period. Organic matter input was measured during 10 years for CWD, 1 year for ground vegetation, and 5 years for other aboveground litter types. Carbon, N, and P release from decomposing litter were simulated for a period of 40 years to determine the relative contributions of each aboveground litter type, including CWD. After 14 years, pine log segments had lost 71 percent of their dry mass; spruce and fir lost 38 percent and 40 percent, respectively. The nitrogen (N) content of the logs increased in pine, changed little in spruce, and decreased by almost 30 percent in fir logs. Phosphorus (P) accumulated in decaying log segments of all three species, especially fir logs in which the P content was nearly five times the initial content after 14 years. Tree species with the lowest initial concentration had the greatest relative accumulation. Thus, wood decay organisms may compete with vegetation for limiting nutrients in these forests. The proportion of coarse woody debris (CWD) in aboveground litter input was 19 percent at the pine site, 3 percent at the spruce site, and 24 percent at the fir site. The contribution of CWD to N and P release was 2 percent or less, except at the fir site where CWD released 5 percent of the N. Coarse woody debris does not appear to make a significant contribution to N and P cycling in these forests.
A pervasive belief in soil ecology is that consumption and gut passage of litter by soil macro-ar... more A pervasive belief in soil ecology is that consumption and gut passage of litter by soil macro-arthropods, such as earthworms, millipedes, myriapods, diplopods and various insect larvae (also referred
A factorial thinning and fertilization experiment was established in central British Columbia in ... more A factorial thinning and fertilization experiment was established in central British Columbia in a 36-year-old high-density fire-origin lodgepole pine (Pinus contorta Dougl. ex Loud. var. latifolia Engelm.) stand to examine the effects of density, nutrition, and their interaction on tree and stand growth, foliage biomass per hectare, and growth efficiency. Volume growth was increased from 2 to 7 m3·ha1·year1 when fertilizer was applied without thinning and to 5 m3·ha1·year1 when fertilizer was applied with thinning. Thinning increased tree-level foliage biomass and growth efficiency by concentrating limited resources onto fewer trees, resulting in increased tree-level volume growth. Stand-level volume growth was reduced by thinning because of the large reduction in stocking. However, by year 4, stand-level volume growth was the same on control and thinned plots, suggesting that thinned trees have already recaptured the site potential. Fertilization increased both tree-level and stand-level productivity through increases in resource availability per tree and per hectare. This resulted in increased foliage biomass and growth efficiency at the tree and stand level. The combination of thinning and fertilization resulted in the greatest tree-level growth because of increased tree-level foliage biomass and growth efficiency. Boron appears to be the most limiting element followed by sulfur and nitrogen.
Scarification is a widely used silviculture method and is suggested to improve organic matter dec... more Scarification is a widely used silviculture method and is suggested to improve organic matter decomposition rate. In this study, I made the use of an experiment that buried humus material into mineral soil after clear-cuts and studied its effects on humus decomposition rate in four biogeoclimatic zones (CWH, ESSF, ICH and IDF) in British Columbia. Litterbags containing local humus materials (mixture of F and H layers) were placed on the forest floor surface or buried in the soil (5-10 cm deep). Samples were retracted annually and dry mass and carbon (C) content were measured to calculate the remaining C mass in each sample for three continuous years. The remaining C mass at all of four sites was lower when buried than placed on the surface, but the difference was significant only at the drier IDF site. Humus in forests with better climatic conditions, such as abundant precipitation and suitable temperature, responded weakly to burying. Stimulation of humus decomposition through scarification is most likely to occur in dry forests in B.C.
Prescott, C. E. 2014. The scientific value of long-term field trials in forest soils and nutritio... more Prescott, C. E. 2014. The scientific value of long-term field trials in forest soils and nutrition research: An opportunist's perspective. Can. J. Soil Sci. 94: 255–262. Long-term field trials are essential in allowing accurate prediction of stand responses to silvicultural treatments. Less well appreciated is the added value that long-term field trials afford to science through a variety of means, often not included in the original experimental plan. Long-term field trials provide a platform upon which additional studies can be conducted; for example a suite of alternative silvicultural trials allowed assessment of influences of forest harvesting on rates of litter decomposition. Well-designed, long-term field trials can be re-purposed to address questions not related to the original research; for example, many of the common garden experiments used to discern influences of different tree species on soil were not originally intended for this purpose. Long-term trials may reveal effects on other ecosystem components such as understorey vegetation or soil organisms, which can generate new hypotheses about ecosystem functioning. Finally, including unusual or non-operational treatments can generate insights that would not occur where trials were constrained to current operational practices. Improved accounting of the additional scientific insights afforded by long-term field trials would go some way towards improved accounting of their true value to science.
Fish-wood compost and wheat straw were applied to chlorotic plantations of western redcedar (Thuj... more Fish-wood compost and wheat straw were applied to chlorotic plantations of western redcedar (Thuja plicata Donn ex D. Don) on northern Vancouver Island to determine their effectiveness as fertilizers. Two years after application, tree growth was greater in the compost-and straw-amended plots than in control plots. The greatest growth response was in straw-amended plots. The first year after application, foliar concentrations of N, P, K, and S were higher in trees in the straw and compost plots. Two years after treatment, foliar nutrient concentrations returned to pretreatment levels in the compost plots, but remained elevated in the straw plots. Concentrations of KCl-extractable N in forest floors 2 years after treatment were greater in the straw plots than in the control plots prior to and after a 29-day incubation. The rate of CO 2 evolution from the forest floor was also greatest in the straw plots 2 years after treatment. These results suggest that addition of a fresh residue such as straw to these sites may promote a long-term increase in N availability and tree growth. Résumé : Un compost de poisson ou de bois ainsi que de la paille de blé furent appliqués dans des plantations chlorotiques de thuya géant (Thuja plicata Donn ex D. Don) établies dans la partie nord de l'île de Vancouver afin d'évaluer leur efficacité comme fertilisants. Deux ans après l'application, la croissance des arbres était plus forte dans les parcelles amendées avec le compost ou la paille. La plus forte croissance est survenue dans les parcelles amendées avec la paille. La première année après l'application, les concentrations foliaires de N, P, K et S étaient plus élevées dans les parcelles traitées avec le compost ou la paille. Deux ans après le traitement, la concentration foliaire des nutriments est revenue au niveau antérieur au traitement dans les parcelles traitées avec le compost mais elle est demeurée élevée dans les parcelles traitées avec la paille. La concentration de N extractible au KCl dans la couverture morte, 2 ans après le traitement, était plus élevée dans les parcelles traitées avec la paille que dans les parcelles témoins avant et après une période d'incubation de 29 jours. Le taux d'évolution du CO 2 dans la couverture morte était également plus élevé dans les parcelles traitées avec la paille 2 ans après son application. Ces résultats suggèrent que l'addition dans ces sites de résidus non décomposés tels que la paille peut amener une augmentation à long terme de la disponibilité de N et de la croissance des arbres. [Traduit par la Rédaction]
We tested several hypotheses to explain the superior growth and nitrogen (N) status of lodgepole ... more We tested several hypotheses to explain the superior growth and nitrogen (N) status of lodgepole pine (Pinus contorta Dougl. ex Laws. var. contorta) compared with Sitka spruce (Picea sitchensis (Bong.) Carrière) on a N-poor site by comparing N distribution, N retranslocation, rooting distribution, and mycorrhizal fungi in plots of 11-year-old trees on a cedar-hemlock cutover. Aboveground N content was nine times greater in pine than in spruce of the same age, and thus, we conclude that pine acquired more N during the 11 years than spruce. Greater N acquisition by pine was not related to rooting depth, as both species rooted primarily in the residual forest floor. There were differences in mycorrhizal fungal associates: a high proportion of pine roots were infected with Suillus-like fungi. Pine produced more aboveground biomass per unit N (388 compared with 292 g•g-1 in spruce) and distributed more N to young foliage. Nitrogen retranslocation efficiency (based on foliar N contents in July and October) was higher in pine (50-52%) than in spruce (24-36%). These characteristics all appear to contribute to pine's abilities to both acquire more N and use it more efficiently and, thus, outperform spruce on this N-poor site. Résumé : Nous avons testé plusieurs hypothèses pour expliquer pourquoi le pin lodgepole (Pinus contorta Dougl. ex Laws. var. contorta) a une meilleure croissance et un meilleur bilan de l'azote (N) que l'épinette de Sitka (Picea sitchensis (Bong.) Carrière) sur un site pauvre en N. Des parcelles ont été établies dans un peuplement de cèdre et de pruche coupé à blanc où les arbres étaient âgés de 11 ans afin de comparer la distribution de N, la translocation de N, la distribution des racines et les champignons mycorhiziens. Le contenu en azote épigé était neuf fois plus élevé chez le pin que chez l'épinette du même âge. Par conséquent, nous concluons que le pin a emmagasiné plus de N que l'épinette au cours des onze années de croissance. La plus forte accumulation de N par le pin n'était pas liée à la profondeur de l'enracinement car le système racinaire des deux espèces se développait principalement dans la couverture morte résiduelle. Les champignons mycorhiziens associés aux deux espèces étaient différents. Une forte proportion des racines de pin étaient infectées par des champignons apparentés à Suillus. Le pin produisait plus de biomasse épigée par unité de N (388 comparativement à 292 g•g-1 pour l'épinette) et distribuait davantage de N vers le jeune feuillage. L'efficacité de la translocation de N, basée sur le contenu en N en juillet et octobre, était plus élevée chez le pin (50-52%) que chez l'épinette (24-36%). Ces caractéristiques semblent toutes contribuer à l'acquisition de plus de N et à son utilisation plus efficace par le pin qui déclasse l'épinette sur ce site pauvre. [Traduit par la Rédaction] Bothwell et al. 1279
Vegetation plays an important role in determining soil organic carbon (SOC) stocks, and influence... more Vegetation plays an important role in determining soil organic carbon (SOC) stocks, and influences the mechanisms through which SOC is stabilized within the soil. The type of vegetation selected for use in reclamation may therefore influence the accumulation rate and residence time of SOC in these ecosystems. Earlier studies at reclaimed sites in the Alberta Oil Sands demonstrated that reclaimed ecosystems planted with deciduous trees accumulated the most soil organic matter in the top 10 cm of reclamation material, followed by grass sites, while coniferous sites accumulated the least SOM. The objective of this study was to assess differences in SOC stabilization in the upper 10 cm of soil among revegetated deciduous, coniferous and grass ecosystems 20–40 years following reclamation. We compared soil C in unprotected, physically protected, and chemically protected forms among the three reclamation treatments using density flotation to isolate free particulate (unprotected) SOC from ...
Abstract The nature and properties of the soil, along with other site factors such as climate, sl... more Abstract The nature and properties of the soil, along with other site factors such as climate, slope position, elevation, and aspect, determine the availability of water and nutrients to plants and therefore influence the success of forest restoration programs. Characteristics of the soil therefore warrant careful consideration when estimating the potential of a site for afforestation or reforestation. Many sites being considered for forest landscape restoration have soils that have been degraded through various human activities, which will need to be rehabilitated as part of the restoration process. Characteristics of degraded soils include loss of structure and organic matter, susceptibility to erosion by wind or water, diminished aeration and water-holding capacity, insufficient or excess nutrient supply, excess acidity or salinity, and diminished soil biota. In this chapter, we discuss each of these impairments and the restoration practices that can be applied to rehabilitate degraded soils.
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