Life cycle environmental impact assessment of biochar-based bioenergy production and utilization in Northwestern Ontario,Canada

Biochar-based bioenergy production and sub- sequent land application of biochar can reduce greenhouse gas emissions by fixing atmospheric carbon into the soil for a long period of time. A thorough life cycle assessment of biochar-based bioenergy production and biochar land application in Northwestern Ontario is conducted using SimaPro Ver. 8.1. The results of energy consumption and potential environmental impact of biochar-based bioenergy production system are compared with those of conventional coal-based system. Results show that biocbar land application consumes 4847.61 MJ per tonne dry feedstock more energy than conventional system, but reduces the GHG emissions by 68.19 kg CO2e per tonne of dry feed- stock in its life cycle. Biochar land application improves ecosystem quality by 18 %, reduces climate change by 15 %, and resource use by 13 % but may adversely impact on human health by increasing disability adjusted life years by 1.7 % if biomass availability is low to medium. Replacing fossil fuel with woody biomass has a positiveimpact on the environment, as one tonne of dry biomass feedstock when converted to biochar reduces up to 38 kg CO2e with biochar land application despite using more energy. These results will help understand a comprehensive picture of the new interventions in forestry businesses, which are promoting biochar-based bioenergy production.

An application of data envelopment analysis to investigate the efficiency of lumber industry in northwestern Ontario,Canada

This study aims at exploring the technical efficiency of lum- ber industry in northwestern Ontario, Canada using data envelopment analysis （DEA）. The DEA model analyzes relative technical efficiency of lumber mills with disproportionate inputs and outputs by dividing the 10- year time series data, for inputs and outputs of 24 lumber mills, over two periods （1999-2003 and 2004-2008）. Four inputs, namely, material （log volume）, labour （man-hours）, two types of energy （hog-fuel and electric- ity）, and one output （lumber volume） are used in this study. The trend analysis shows an annual reduction of 10%, 13% and 13% for lumber output, log consumption （input） and number of employees, respectively, during the period 1999-2008. The results from DEA with two scenarios with energy inputs and without energy inputs, for the two periods are found to be mixed and interesting. While some mills have improved their performance in terms of best use of available scarce inputs in the second period, some have shown negative per cent change in efficiency. In the with energy input and the without energy input scenario, some of the mills show a reduction in efficiency in the second period from the first period, with the highest estimated reductions of-13.9% and -47.6%, respectively. A possible explanation for these negative performances of mills in the latter period is the decline in production in the second period compared to the first period, where these mills were not able to adjust their inputs （mostly labour） as proportional lay-offs might not have been possible. These results provide policy makers and industry stakeholders with an improved understanding of the trends of efficiency and employ- ment as well as reallocation opportunities of future inputs in order to increase benefits from this sector.

Life cycle cost and economic assessment of biochar-based bioenergy production and biochar land application in Northwestern Ontario, Canada

Background： Replacement of fossil fuel based energy with biochar-based bioenergy production can help reduce greenhouse gas emissions while mitigating the adverse impacts of climate change and global warming. However, the production of biochar-based bioenergy depends on a sustainable supply of biomass. Although, Northwestern Ontario has a rich and sustainable supply of woody biomass, a comprehensive life cycle cost and economic assessment of biochar-based bioenergy production technology has not been done so far in the region. Methods： In this paper, we conducted a thorough life cycle cost assessment （LCCA） of biochar-based bioenergy production and its land application under four different scenarios： 1） biochar production with low feedstock availability; 2） biochar production with high feedstock availability; 3） biochar production with low feedstock availability and its land application; and 4） biochar production with high feedstock availability and its land applicationusing SimaPro, EIOLCA software and spreadsheet modeling. Based on the LCCA results, we further conducted an economic assessment for the break-even and viability of this technology over the project period. Results： It was found that the economic viability of biochar-based bioenergy production system within the life cycle analysis system boundary based on study assumptions is directly dependent on costs of pyrolysis, feedstock processing （drying, grinding and pelletization） and collection on site and the value of total carbon offset provided by the system. Sensitivity analysis of transportation distance and different values of C offset showed that the system is profitable in case of high biomass availability within 200 km and when the cost of carbon sequestration exceeds CAD S60 per tonne of equivalent carbon （CO2e）. Conclusions： Biochar-based bioenergy system is economically viable when life cycle costs and environmental assumptions are accounted for. This study provides a medium scale slow-pyrolysis plant scenario and we recommend similar experiments with large-scale plants in order to implement the technology at industrial scale.

Allometric models for aboveground biomass of six common subtropical shrubs and small trees

The aboveground biomass(AGB)of shrubs and small trees is the main component for the productivity and carbon storage of understory vegetation in subtropical secondary forests.However,few allometric models exist to accurately evaluate understory biomass.To estimate the AGB of five common shrub(diameter at base<5 cm,<5 m high)and one small tree species(<8 m high,trees’s seedling),206 individuals were harvested and species-specific and multi-species allometric models developed based on four predictors,height(H),stem diameter(D),crown area(Ca),and wood density(ρ).As expected,the six species possessed greater biomass in their stems compared with branches,with the lowest biomass in the leaves.Species-specific allometric models that employed stem diameter and the combined variables of D~2H andρDH as predictors accurately estimated the components and total AGB,with R^(2) values from 0.602 and 0.971.A multi-species shrub allometric model revealed that wood density×diameter×height(ρDH)was the best predictor,with R^(2) values ranging from between 0.81 and 0.89 for the components and total AGB,respectively.These results indicated that height(H)and diameter(D)were effective predictors for the models to estimate the AGB of the six species,and the introduction of wood density(ρ)improved their accuracy.The optimal models selected in this study could be applied to estimate the biomass of shrubs and small trees in subtropical regions.

Soil Temperature and Phosphorus Supply Interactively Affect Physiological Responses of White Birch to CO₂Elevation

Phosphorus (P) is a common limiting nutrient element to plants and its supply and uptake by plants are strongly influenced by soil temperature. However, the interactive effects of the two factors on the physiological responses of plants to global change are poorly understood. In this study, we examined how P supply and Tsoil interacted in affecting physiological responses in white birch (Betula papyrifera) to [CO2]. We exposed seedlings to 7°C, 17°C and 27°C Tsoil, 0.1479, 0.3029 and 0.5847 mM P2O5, and 360 and 720 μmol·mol-1 [CO2] for four months. We have found that both the low soil temperature and CO2 elevation resulted in photosynthetic down regulation but the specific mechanisms of the down regulation were different between the two treatments, particularly the relative contributions of biochemical and photochemical capacity, mesophyll conductance and sink strength for carbohydrate utilization to the down regulation. Furthermore, our data suggest that morphological adjustments, such as reduced leaf size and total leaf area, were the primary form of responses in white birch to low phosphorus supply and no significant physiological acclimation to P supply was detected. Our results suggest that white birch will likely enhance water use efficiency under the projected future climate conditions with doubled carbon dioxide concentration, particularly at warmer soil temperatures. Although a trade-off between water use efficiency and nutrient use efficiency is widely accepted, our results suggest that there does not have to be a trade-off between the two, for instance, CO2 elevation increased both use efficiencies and low soil temperature and reduced nitrogen efficiency without affecting water use efficiency under elevated CO2.

Estimation of Small Reservoir Sedimentation in Semi-Arid Southern Zimbabwe

Small surface reservoirs play an important role of providing ready and convenient source of water for various uses in semi-arid areas which are characterized by erratic and low rainfall. Lack of current data on reservoir capacity loss due to sedimentation is one of the challenges to the sustainable management of surface reservoirs. The study investigated the capacity loss due to sedimentation from 2000-2012, and estimated the trap efficiency of the Mutangi reservoir which is located in semi-arid Chivi, Southern of Zimbabwe. Hydrographic surveys, grab sampling and water depth-capacity methods were used to determine the capacity of the dam as of 2012. To compute capacity loss from 2000 to 2012, the 2000 and 2012 dam capacities were compared whilst the trap efficiency of the reservoir was determined using a set of empirical models that relates trap efficiency to the capacity-watershed area ratio and capacity-inflow ratio. The results show that Mutangi reservoir has a trap efficiency of 95% - 98% (av = 96.4%) and has lost 37% of its capacity due to sedimentation in 12 years (2000 and 2012). Rates of sedimentation were 8539 t·yr-1, 9110?t·yr-1 and 8265 t·yr-1 for the hydrographic survey, grab sampling and water depth-capacity method respectively, and the little difference in these figures demonstrates that any method can be used to determine sedimentation rates. The area specific sediment yield (ASY) ranged from 14 - 15.5 t·ha-1·yr-1 (av = 14.956 t·ha-1·yr-1). At the current rate of sedimentation the projected dead level of the reservoir will be lost to sedimentation in 8 years while the useful life of the reservoir is estimated to be 30 years. Capacity loss due to sedimentation is further complicating the already strained water scarcity situation in semi-arid areas and management decisions should be made based on the current sedimentation rates estimated by different methods. These results imply that management practices that reduce erosion, hence sedimentation in these small reservoirs should be practiced in order to prolong their lifespan.

Radial Growth Responses of Four Deciduous Species to Climate Variables in Central Ontario, Canada

To address the central question of how climate change influences tree growth within the context of climate will become warmer and drier in central Ontario, we used dendroclimatological analysis to understand the radial growth responses of four co-occurring hardwood species: sugar maple (Acer saccharum Marsh.), yellow birch (Betula alleghaniensis Britton), American beech (Fagus grandifolia Ehrh.), and red oak (Quercus rubra L.) to climatic variables in central Ontario, Canada. Ring width chronologies were developed for the target species within three regions (Algonquin Park, Haliburton, and North Bay) of the study area. Seven of the eleven chronologies exceeded the 0.85 expressed population signal (EPS) and were used for further analysis. Mean sensitivity and standard deviation values of the Ontario chronologies indicated lower sensitivity to climate fluctuations than in southern North America. Positive correlations with precipitation variables from the current and prior growing season supported previous studies in sugar maple, while a positive response to growing degree days suggested the importance of warmer temperatures and a longer growing season at the northern limit of the distribution range of sugar maple. Yellow birch ring width was correlated with precipitation from the previous growing season and from the end of the current growing season also suggesting that mature trees with deep root systems might utilize moisture from deep soil. Radial growth of American beech positively correlated to precipitation of the previous season, suggesting that the amount of moisture reserves stored in the previous year might affect growth in the following year. Drought stress at the start of the growing season for red oak had negative correlations with precipitation in August indicating possible cessation of cambial activity. This decline in growth process would also affect ring width of red oak the following year as expressed by negative correlations with mean annual temperature from the previous year. Abnormally, warm seasonal temperatures may be indicative of drought stress in red oak.

Interactive Effects of Elevated [CO₂] and Soil Water Stress on Leaf Morphological and Anatomical Characteristic of Paper Birch Populations

The leaf morphological and stomatal characteristics of four paper birch (Betula papyrifera Marsh) populations, grown at four treatment conditions of carbon dioxide [CO2] and soil water levels were investigated to determine whether future increases in atmospheric [CO2] and water deficit affected the leaf characteristics. The populations from Cussion Lake, Little Oliver, Skimikin and Wayerton were grown for 12 weeks under ambient (360 ppm) and elevated (720 ppm) [CO2] at both high and low water levels. The populations significantly differed in leaf area and stomatal characteristics due to the interaction effects of [CO2], water levels and population differences. Most leaf morphological characteristics and stomatal density varied due to the effects of [CO2] and/or populations, but not due to the effect of water levels. Although elevated [CO2] alone barely affected stomatal area of the birch populations, simultaneous elevated [CO2] at both water levels had stimulated stomatal characteristics within and among the populations. Overall, elevated [CO2] reduced leaf area and increased stomatal density;and low water level resulted in smaller stomatal area, pore area and guard cell width. However, the populations responded differently to an increase in [CO2] and water levels. All populations showed plastic responses with respect to [CO2] and water levels either by decreasing stomatal area under low water level or by increasing stomatal density under elevated [CO2]. Hence, integration between and within leaf characteristics had helped paper birch populations maintain balance between [CO2] gain and water loss.

Stand age structural dynamics of conifer, mixedwood, and hardwood stands in the boreal forest of central Canada

To study the effects of stand development and overstory composition on stand age structure, we sampled 32 stands representing conifer, mixedwood, and hardwood stand types, ranging in ages from 72 to 201 years on upland mesic sites in northwestern Ontario. We defined the stages of stand development as: stem exclusion/canopy transition, canopy transition, canopy transition/gap dynamics, and gap dynamics. Stand age structure of conifer stands changed from bimodal, bimodal, reverse-J, and bimodal, respectively, through the stages of stand development. Mixedwood and hardwood stands revealed similar trends, with the exception of missing the canopy transition/gap dynamic stage in mixedwoods. Canopy transition/gap dynamic stage in hardwoods showed a weaker reverse-J distribution than their conifer counterparts. The results suggest that forest management activities such as partial and selection harvesting and seed-tree systems may diversify standard landscape-level age structures and benefit wildlife, hasten the onset of old-growth, and create desired stand age structures. We also recommend that the determination of old-growth using the following criteria in the boreal forest: 1) canopy breakdown of pioneering cohort is complete and stand is dominated by later successional tree species, and 2) stand age structure is bimodal, with dominating canopy trees that fall within a relatively narrow range of age and height classes and a significant amount of understory regeneration.

Photoperiod and Nitrogen Supply Limit the Scope of Northward Migration and Seed Transfer of Black Spruce in a Future Climate Associated with Doubled Atmospheric CO2 Concentration

The predicated changes in precipitation and temperature associated with the continued elevation of atmospheric CO2 concentration will trigger the northward shift of the Climate Envelopes for 130 North America tree species by as much as 10 degrees. However, climate envelope models do not take into account changes in other factors that may also influence the survival and growth of plants at the predicted new locations, such as photoperiod and nutrient regimes. This study investigated how photoperiod and nitrogen supply would affect the ecophysiological traits of black spruce (Picea mariana (Mill) B. S. P.) that are critical for survival and growth at new locations predicted by climate envelope models. We exposed black spruce seedlings to the photoperiod regime at the seed origin (PS) and that 10° north of the seed origin (PNM) as predicted by climate envelope models under the current and doubled atmospheric CO2 concentration and different levels of N supply (30 vs. 300 μmol·mol-1 N). We found that the PNM and the 30 μmol·mol-1 N supply both had negative impact on the development of seedling cold hardiness in the fall, and led to earlier burst of the terminal bud and greater rate of mortality in the following growing season. While the PNM stimulated seedling growth in the first growing season, the effect was not sustained in the second growing season. Our results suggest that the photoperiod regimes and poor nutrient conditions at higher latitudes will likely constrain the scope of the northward migration or seed transfer of black spruce.

The Effect of Water Hyacinth (<i>Eichhornia crassipes</i>) Compost on Tomato (<i>Lycopersicon esculentum</i>) Growth Attributes, Yield Potential and Heavy Metal Levels

The potential of different water hyacinth compost application rates in influencing growth attributes, yield and heavy metal accumulation of lead (Pb), copper (Cu), nickel (Ni) and zinc (Zn) in tomato fruit was studied in Masvingo. Four treatments of water hyacinth compost rates of 0, 37, 55.6 and 74.1 t·ha-1 were each replicated three times and applied in a randomized complete block design set up. Results showed that water hyacinth compost application rates significantly affected plant height, days to maturity and yield but had no influence on the number of tomato fruits per plant. The plant height at application rate of 74.1 t·ha-1 was 25%, 56% and 63% higher than the control at week 6, 9 and 12, respectively. At application rates of 56.6 t·ha-1, plant heights were 11%, 13% and 12% higher than the control whilst marginal plant height differences of -4%, 6% and 4% were recorded between application rate of 34.7 t·ha-1 and the control at week 6, 9 and 12, respectively. Tomato plants under compost rates of 34.7, 56.6 and 74.1 t·ha-1 in comparison to the control delayed maturity by 10, 17 and 20 days, respectively. Yields of 52, 55, 60 and 68 t·ha-1 were realized from hyacinth compost rates of 0, 34.7, 56.6 and 74.1 t·ha-1, respectively. Heavy metal concentrations increased with increase in the water hyacinth compost rate but at all application rates, the average concentrations were 85%, 93% and 86% lower than the Codex Alimentarious Commission permissible levels for Pb, Cu and Zn. Water hyacinth compost at a rate of 74 t·ha-1 therefore can be used for increased tomato yield without exposing consumers to heavy metal toxicity.

Effect of Tillage Systems and Vine Orientation on Yield of Sweet Potato (<i>Ipomoea batatas</i>L.)

In Zimbabwe sweet potato (Ipomoea batatas L.) production is practiced under different tillage systems with varying vine orientations, which contribute to variable yields. Limited research on yield loss due to these different practices is available despite that the majority of farmers are growing sweet potatoes to sustain their livelihoods. A field study was carried out at Midlands State University in the 2013/14 rainy season, to determine the effect of tillage systems and vine orientation on yield of sweet potato. A 2 × 3 factorial treatment structure in a randomized complete block design (RCBD), with three replications was used. Tillage systems had two factors (ridge and mound) and three vine orientations were used (horizontal, fold and loop). Data on storage root length, storage root diameter and storage root weight was subjected to Analysis of Variance (ANOVA) at 5% significance level. There was no interaction (p < 0.05) between tillage systems and vine orientations on storage root diameter, storage root length and storage root yield. The horizontal vine orientation gave statistically significant (p < 0.05) storage roots diameter of width 405 mm. Conversely the loop vine orientation had statistically the least (316 mm) storage root diameter. Horizontal vine orientation had significantly (p < 0.05) wider storage roots than the loop vine orientation. The ridge recorded longer (134.2 mm) mean storage root length, while those from mounds had shorter (115.9 mm) root length. The loop and the horizontal vine orientations recorded statistically the highest (35.5 t/ha and 34.8 t/ha respectively) sweet potato storage root yield. On the other hand, the fold vine orientation obtained significantly the lowest (28.7 t/ha) storage root yield. The research concluded that the horizontal and fold vine orientations had the widest storage root diameter and the ridge had longer storage root lengths. The loop and horizontal vine orientations are recommended in sweet potato production if high yields are to be achieved.

Assessing effects of seed source and transfer potential of white birch populations using transfer functions

Trees have adapted to their local climates, but with changes in the climate, they may currently or in the near future occupy climates that are sub-optimal for growth and survival. The goal of current reforestation is therefore to establish a new generation of trees with growth adapted to the future climate(s). Here, we present preliminary data of a study assessing the effects of seed source and transfer potential of white birch populations. Seeds from twenty-five white birch (Betula papyrifera Marsh.) populations collected acrossCanadawere grown in the greenhouse and observed for emergence time, germination and growth. The seedlings were later planted in a common garden. After one year, the seedlings were measured for height, root-collar diameter (RCD) and survival rate and average volume per seedling calculated. Transfer functions were used to estimate the climatic distance from which populations may be transferred to the test site. There was a significant effect of population on all growth variables. Initial height was positively correlated with 1-year height and survival. Germination rate negatively correlated with emergence time. Principal component analysis showed effects of seed origin on performances of the populations in the common garden. Summer temperature was the best predictor of the transfer distance.

Interaction of Trembling Aspen and Lodgepole Pine in a Young Sub-Boreal Mixedwood Stand in Central British Columbia

Strategies for managing mixed broadleaf-conifer stands in British Columbia (BC) have been under review in recent years as the benefits of mixedwood management have been recognized. More has been learned about the role of broadleaves in forest ecosystems however ecosystem-specific knowledge about the competitive interactions between mixed broadleaf-conifer stands is still scarce. Therefore a competitive interactions study was conducted to facilitate ecosystem-specific management for lodgepole pine (Pinus contorta Dougl. Ex Loud. Var. latifolia Engelm.) and trembling aspen (Populus tremuloides Michx.) in the sub-boreal spruce (SBS) zone of central BC. The experiment was a completely randomized block design with six different aspen densities replicated three times. Each replicate was sampled three times between ages 14 to 19 years. Pine diameter and height growth were influenced by aspen density. Our current quantitative findings suggest that lodgepole pine growth was not impacted when growing with aspen densities up to 2500 stems ha-1. Considering free growing (FTG) and not free growing (NFTG) pine at the time of trial establishment, an insignificant difference was found for DBH, height and crown volume responses. Leaf area index (LAI) and diffuse non-interceptance (DIFN) radiation were also not significantly different between FTG or NFTG trees suggesting our results exceed the current BC’s free growing standard. Further work is recommended to determine whether or not the current free growing standards are appropriate for producing the desired crop outcome.

Effects of Tianda 2116 Plant Growth Regulator on Growth and Yield of Winter Wheat (Triticum aestivum L.)

To achieve optimum yield of wheat, supplementation of soil and foliar applied fertilizers with plant growth regulators is vital to assure effective assimilation of nutrients by plants. A trial was conducted at Gwebi Agricultural College Farm in Mashonaland West Province of Zimbabwe, during the 2012 winter wheat season (May to August), to evaluate the effects of differing times of application of Tianda 2116 plant growth regulator on the growth and yield of wheat (variety SC Sekuru). The trial was laid out in a Randomized Complete Block Design with three replications. The treatments were: Tianda 2116 applied at the following weeks after planting (WAP): 2 WAP, 3 WAP, 4 WAP, 5 WAP, 6 WAP, 14 WAP and no Tianda 2116 applied (control). No significant differences (P > 0.05) were noted among treatments for mean number of tillers per plant and mean number of spikes per plant. Application of Tianda 2116 at 2 and 3 WAP delayed flowering and physiological maturity. Early application of Tianda 2116 increased the number of spikelets per spike, thousand grain weight and grain yield. Conclusively, Tianda 2116 applied 2 or 3 WAP is effective in reducing growth while enhancing yield parameters in wheat production.

Morphological Response of Jack Pine to the Interactive Effects of Carbon Dioxide, Soil Temperature and Photoperiod

Responding to the predicted shift in climate envelope jack pine, (Pinus banksiana Lamb.) might migrate 10° northward between 2071 and 2100 and will be exposed to a different photoperiod regime. Successful migration of the species might depend on the initial acclimating capability to the conditions of new location. The impacts of elevated carbon dioxide concentration [CO2], soil temperature and photoperiod on the phenological traits, growth and biomass responses in jack pine seedlings were investigated. Seedlings were grown in greenhouses under two [CO2] (400 and 950 μmol•mol-1), two soil temperatures (ambient soil temperature at seed origin and 5°C warmer) and three photoperiod regimes (photoperiods at seed origin, 5° north of the seed origin and 10° north of the seed origin). Budburst and bud setting time were recorded and the seedling height (Ht), root collar diameter (RCD), root biomass, stem biomass and leaf biomass were measured after six months of treatment. It was observed that under elevated [CO2], ambient Tsoil and photoperiods associated with 10° northward migrations budburstis advanced by 10 days. Photoperiods toward north significantly prolonged the bud setting time. However, tri-factor interactive effect on bud set was not statistically significant. Elevated [CO2] significantly (P < 0.05) increased the RCD, volume of the seedlings and total biomass and longer growing season photoperiods towards north significantly increased the seedling heights. Though elevated [CO2] significantly increased the projected leaf area, it had no significant effect on specific leaf area. Elevated [CO2] significantly reduced the shoot to root ratio, which indicated higher biomass allocation in roots under elevated [CO2]. However, all these growth and biomass responses were statistically insignificant under tri-factor interactive effects. The results suggest that climate change induced northward migration will not affect the growth of jack pine. However, a long distance migration (e.g. 10° north) will expose the species to late-spring frost damage.

Biochar-based bioenergy and its environmental impact in Northwestern Ontario Canada: A review

Biochar is normally produced as a by-product of bioenergy. However, if biochar is produced as a co-product with bioenergy from sustainably managed forests and used for soil amendment, it could pro- vide a carbon neutral or even carbon negative solution for current envi- ronmental degradation problems. In this paper, we present a comprehen- sive review of biochar production as a co-product of bioenergy and its implications. We focus on biochar production with reference to biomass availability and sustainability and on bioehar utilization for its soil amendment and greenhouse gas emissions reduction properties. Past studies confirm that northwestern Ontario has a sustainable and sufficient supply of biomass feedstock that can be used to produce bioenergy, with biochar as a co-product that can replace fossil fuel consumption, increase soil productivity and sequester carbon in the long run. For the next step, we recommend that comprehensive life cycle assessment of bio- char-based bioenergy production, from raw material collection to bioehar application, with an extensive economic assessment is necessary for making this technology commercially viable in northwestern Ontario.

Base cation concentrations in forest litter and topsoil have different responses to climate and tree species along elevational gradients

The forest litter is an essential reservoir of nutrients in forests, supplying a large part of absorbable base cations(BC) to topsoil, and facilitating plant growth within litter-soil system. To characterize elevational patterns of base cation concentrations in the forest litter and topsoil, and explore the effects of climate and tree species, we measured microclimate and collected the forest litter and topsoil(0-10 cm) samples across an elevational range of more than 2000 m(1243 ～ 3316 m a.s.l.),and analyzed the concentrations of BC in laboratory. Results showed that: 1) litter Ca concentration displayed a hump-shaped pattern along the elevational gradients, but litter K and Mg showed saddle-shaped patterns. Soil Ca concentration increased with elevation, while soil K and Mg had no significant changes. 2) Ca concentration in the forest litter under aspen(Populus davidiana) was significantly higher than that in all other species, but in topsoil, Ca concentration was higher under coniferous larch and fir(Larix chinensis and Abies fargesii). Litter K and Mg concentrations was higher under coniferous larch and fir, whereas there were nosignificant differences among tree species in the concentrations of K and Mg in topsoil. 3) Climatic factors including mean annual temperature(MAT), growing season precipitation(GSP) and non-growing season precipitation(NGSP) determined BC concentrations in the forest litter and topsoil. Soil C/N and C/P also influenced BC cycling between litter and soil. Observation along elevations within different tree species implies that above-ground tree species can redistribute below-ground cations, and this process is profoundly impacted by climate. Litter and soil Ca, K and Mg with different responses to environmental variables depend on their soluble capacity and mobile ability.

Biochar-Induced Priming Effects in Young and Old Poplar Plantation Soils

The priming effect(PE)induced by biochar provides a basis for evaluating its carbon(C)sequestration potential in soils.A 60 days’laboratory incubation was conducted,which involved the amendment of biochar(1%of soil mass)produced from rice straw at 300℃(B300)and 500℃(B500)to young(Y)and old(O)poplar plantation soils,with the aim of studying the responses of biochar-induced PEs to poplar plantation ages.This incubation included six treatments:Y+CK(control),Y+B300,Y+B500,O+CK,O+B300,and O+B500.Carbon dioxide(CO_(2))emissions were significantly increased(p<0.05)in the B300 amended soils,while it was decreased in the B500 amended soils compared to the CK.The primed CO_(2) emissions were 2.35 times higher in the Y+B300 than the O+B300 treatments,which was measured to be 18.6 and 5.56 mg C·kg^(-1) with relative PEs of 12.4%and 3.35%,respectively.However,there was little difference between the primed CO_(2) emissions in Y+B500 and O+B500 treatments,which were measured to be-24.9 and-29.6 mg·C·kg^(-1) with relative PEs of-16.6%and-17.8%,respectively.Dissolved organic carbon(DOC)was significantly lower in the young poplar plantation soil than that in the old poplar plantation soil regardless of biochar amendment throughout the incubation,indicating greater C-limit of soil microorganisms in the young poplar plantation soil.Using ^(13)C isotope tracing,neither B300 nor B500 decreased native soil-derived DOC,which indicated that the negative B500-induced PEs were not due to a reduction in the availability of native soil-derived C.In conclusion,the response of biochar-induced PEs to poplar plantation age depends on biochar types while soil available C indirectly affects biochar-induced PEs.Further studies should focus on how the interactive effects between soil C availability and microbial community impacts biochar-induced PEs.

Leaf morphological variation among paper birch (<i>Betula papyrifera</i>Marsh.) genotypes across Canada

Variations in leaf morphological characteristics have been extensively studied at both interand intraspecific levels although not explicitly on paper birch (Betula papyrifera Marsh). Paper birch populations might have considerable genotypic and leaf morphological variations that have allowed them to inhabit wide environmental gradients. In this study, we analyzed variations in leaf morphological characteristics in 23 paper birch populations collected across Canada and grown in a greenhouse. Furthermore, we examined whether the variations in leaf morphological characteristics observed were related to the climate of the population’s origin. We found significant genotypic differences in all leaf morphological characteristics (p < 0.05) measured among the birch populations. Thus, we expected that the morphological variations in birch might be related to natural diversity in birch populations due to environmental differences at habitat origin. Principal component analysis (PCA) reduced thirteen leaf morphological variables to five principal components (PC) explaining 84.74% of the total variance in the original data. PCs accumulated with specific leaf area, petiole and leaf width were positively related to latitudinal, longitudinal, and elevational gradients at the population’s origin. Unpredictably, these PCs were significantly negatively correlated to precipitation and aridity index at the origin. Thus, we analyzed if correlations within leaf morphological characteristics had supported the birch populations to acclimate and produce unpredictable relations with the environment of origin. Our results showed that the populations originated in limited precipitation (during growing season) had large leaf width and petiole size but low leaf hairs on adaxial surface. Thus, all these leaf morphological features provide a basis for the birch to reduce water loss from leaves and balance water use efficiency in reduced precipitation. Furthermore, the leaf characteristics measured may also include phenotypic plasticity of the birch as an acclimation to the environment as in the greenhouse.