Peat Mineral Soil Research Articles

Effect of different type of soil as growing media on physiological quality of harvested okra (Abelmoschus esculentus)

Soil properties are very important to be well understood before planting any crop. Different types of soil will possess different properties. The properties of soil will influence the yield and quality of crops. For instance, poor soil properties will produce low quality of okra, thus reducing consumer demand. It is necessary to find conditions that are suitable for soil in order to get the best okra quality to fulfil the demand of consumers. The purpose of this research is to determine the physiological quality of harvested okra on different types of soil which are peat soil (T1), mineral soil (T2) and alluvium soil (T3). Each treatment was replicated five times and was applied with the same amount of fertilizer (NPK 12: 12: 17: 2); 10 g. Parameters in term of quality of physical appearances were taken once after the fruits were harvested. The parameters taken include the length of fruit (cm), the diameter of fruit (mm), the colour of fruits and fruit tenderness. Parameters for growth performance were also taken for each treatment. The result obtained shows a high significant difference in term of physical features of okra such as length of fruit (cm), the diameter of fruit (mm) and fruit tenderness for each treatment. Harvested alluvium soil -based okra was found to be the most promising for fruit yield, physical quality and quantitative characteristics. This is because the result of parameters of alluvium soil (T3) is higher than peat soil and mineral soil in term of length of fruits; 17.18 cm, diameter of fruit; 19.42, yield produced; 9.8 and tenderness; 9.2. The T3 soil also has rich in micronutrients especially potassium. In conclusion, properties of soil whether chemically or physically will influence the yield and quality of crops either directly or indirectly.

Drivers of understory species richness in reconstructed boreal ecosystems: a structural equation modeling analysis

Understory vegetation accounts for the most diverse part of the plant community in boreal forests and plays a critical role in stand dynamics and ecosystem functions. However, the ecological processes that drive understory species diversity are poorly understood and largely unexplored for reconstructed boreal ecosystems. The current study explored the relationships between understory species richness and biotic and abiotic factors in sites reclaimed after oil sands mining in northern Alberta, Canada, three and six growing seasons post-reclamation. Reclaimed sites with two main surface soils, forest floor mineral soil mix (FFMM) and peat mineral soil mix (PMM), were used along with post-fire benchmarks. A number of soil physicochemical (including nutrients) and vegetation properties were measured and considered in the a-priori hypothesis framework. Structural equation models (SEM) were used to evaluate the multivariate relationships. In general, the FFMM sites had greater species richness than the PMM sites, even six growing seasons after reclamation. A maximum 254% increase in graminoid and shrub cover was observed on FFMM between year 3 and 6 post-reclamation, whereas a maximum 137% increase in forb and bryophyte cover was recorded on PMM. The post-fire sites showed a significant increase (70%) only in shrub cover. Major driving factors of understory species richness varied among soil types. The SEM revealed a strong interdependency between species richness and soil and vegetation factors on FFMM with a positive control from soil N on species richness. In contrast, on PMM soil nutrients had a negative effect on species richness. Temporal changes in the drivers of species richness were mostly observed on FFMM through a negative vegetation control on species richness. The models and significant causal paths can be used in monitoring changes in understory species relationships in reclaimed sites and in identifying future research priorities in similar systems.

Effects of Capping Strategy and Water Balance on Salt Movement in Oil Sands Reclamation Soils

The success of oil sands reclamation can be impacted by soil salinity depending on the materials used for soil reconstruction and the capping strategies applied. Using both a greenhouse-based column experiment and numerical modeling, we examined the potential pathways of salt migration from saline groundwater into the rooting zone under different capping strategies (the type and the thickness of the barrier layer) and water balance scenarios. The experimental results showed that there would be salinity issues in the cover soil within several growing seasons if there was a shallow saline groundwater table and if the soil was not properly reconstructed. The thickness of the barrier layer was the most significant factor affecting the upward movement of saline groundwater and salt accumulation in the cover soil. The suitable thickness of the barrier layer for preventing the upward movement of saline groundwater and salt accumulation in the cover soil for each material varied. A numerical simulation for a 15-year period further indicates that, when the cover soil was 50 cm of peat-mineral soil mix and when wet, dry, or normal climatic conditions were considered, the minimum barrier thickness to restrain salt intrusion into the cover soil in the long term was about 75 or 200 cm for coarse tailings sand or overburden barrier material, respectively. In view of the above, to minimize salt migration into the rooting zone and ensure normal plant growth, oil sands reclamation should consider salt migration when designing soil capping strategies.

Growth and physiological responses of tree seedlings to oil sands non-segregated tailings

Bitumen recovery from oil sands in northeastern Alberta, Canada produces large volumes of tailings, which are deposited in mining areas that must be reclaimed upon mine closure. A new technology of non-segregated tailings (NST) developed by Canadian Natural Resources Limited (CNRL) was designed to accelerate the process of oil sands fine tailings consolidation. However, effects of these novel tailings on plants used for the reclamation of oil sands mining areas remain to be determined. In the present study, we investigated the effects of NST on seedlings of three species of plants commonly planted in oil sands reclamation sites including paper birch (Betula papyrifera), white spruce (Picea glauca) and green alder (Alnus viridis). In the controlled-environment study, we grew seedlings directly in NST and in the two types of reclamation soils with and without added NST and we measured seedling growth, gas exchange parameters, as well as tissue concentrations of selected elements and foliar chlorophyll. White spruce seedlings suffered from severe mortality when grown directly in NST and their needles contained high concentrations of Na. The growth and physiological processes were also inhibited by NST in green alder and paper birch. However, the addition of top soil and peat mineral soil mix to NST significantly improved the growth of plants, possibly due to a more balanced nutrient uptake. It appears that NST may offer some advantages in terms of site revegetation compared with the traditional oil sands tailings that were used in the past. The results also suggest that, white spruce may be less suitable for planting at reclamation sites containing NST compared with the two studied deciduous tree species.

Effects of Stockpiling and Organic Matter Addition on Nutrient Bioavailability in Reclamation Soils

Core Ideas Stockpiling and organic matter admixing effects on reclamation soils were tested. Stockpiling effects were stronger on forest floor based reclamation soils. Organic matter admixing showed fertility and microbial benefits mostly in mineral sub‐soils. A faster microbial assimilation was achieved in soils admixed with forest floor organic matter. Nutrient bioavailability is crucial for vegetation establishment and organic matter cycling after major ecosystem disturbance such as open pit mining. In this study, the stockpiling and organic matter admixing effects on nutrient bioavailability were examined in soils used for reclaiming oil sands disturbed sites in northern Alberta, Canada. Stockpiled and directly salvaged peat mineral soil mix (PMM) and forest floor mineral soil mix (FFMM), the two main oil sands reclamation soils, and a nutrient poor mineral sub‐soil (SS) were used in this experiment. Reclamation soils were inter‐mixed at different ratios (PMM to FFMM or SS at 60:40, 80:20 and 90:10) to examine the organic matter admixing effects. Significant stockpiling effects on nutrient bioavailability and microbial functions were mostly observed in FFMM. Microbial biomass C was greater, and mineralization of lignin substrate was lower in both stockpiled PMM and FFMM soils compared to the directly salvaged soils. Significant fertility benefit was found in the FFMM‐admixed SS and PMM soils through an increase in N and K availability. FFMM admixing also increased microbial functional diversity and assimilation rate compared to the non‐admixed soils. Mineralization of polymeric substrates was the main driver of nutrient availability in stockpiled PMM, whereas carboxylic acids and carbohydrates were the major drivers in directly salvaged PMM, as indicated by the Random Forest models. The findings suggest that stockpiling effects are much stronger in FFMM than in PMM, and FFMM admixing to reclamation soils may provide nutritional and microbial functional benefits, especially in nutrient‐poor soils.

Effects of land reclamation practices on the productivity of young trembling aspen and white spruce on a reclaimed oil sands mining site in northern Alberta

Identifying the main drivers of tree height growth on reclaimed oil sands sites of northern Alberta can provide useful information on what can be done to shorten the recovery time of these disturbed sites. The effect of water availability, foliar nutrient concentrations, competition, and soil chemical properties on young trembling aspen and white spruce height across two soil types (peat-mineral mix and forest floor-mineral mix) and two fertilizer levels (200 kg NPK ha−1 and no fertilizer) was examined. For comparison, we also studied a natural site that burned the same year the reclaimed site was established. On the reclaimed site, peat-mineral soil had the greatest tree height for both species, though not by a significant margin in the case of white spruce. The fertilizer treatment had no apparent effect on tree height on the forest floor-mineral soil and a negative effect on the peat-mineral soil. Fertilization increased vegetation cover on both soil types, which, when combined with the negative or lack of durable effect of fertilization on tree height, suggest that the increase in competition for resources could have had a stronger effect on tree height than the increase in immediately available nutrients following fertilization. The majority of tree height growth drivers found were related to nutrient availability and, as far as we can tell, did not significantly differ between reclamation soil types. Aspen sucker height on the burned site was not strongly correlated to the measured variables, suggesting that suckers do not yet fully rely on their environment for height growth.

AGROECOLOGICAL EFFICIENCY OF SEWAGE SLUDGE AND VERMICOMPOST IN AGROCENOSES OF CULTIVATED OAT

Aim. The article suggests research on biotransformation of sewage sludge from treatment facilities in the city of Ryazan into organomineral fertilizer. An ecological analysis of the efficiency of fertilizer use in oat cultivation is proposed. Methods. Determination of growth and development indices of plants, structure of the oats crop of the Skakun variety, agrochemical indices of the soil. Results. Analyzed the effect of sewage sludge and vermicomposts, which are the basis for the cultivation of oats (Avena sativa) on organic soils (peat-mineral soil) which forms favorable conditions for the development of plants and the formation of high productivity of the crop, ensuring the production of ecologically safe grain products. Conclusion. The effect of the dehydrated sewage sludge and vermicomposts from the biological treatment plant in the city of Ryazan on the productivity of the Skakun oat has been revealed. The use of sewage sludge and vermicomposts is marked by an increase in the elements of the crop structure of the grain crop, as a consequence, by an increase in the bioproductivity of the phytocenosis, which indicates the advisability of using sewage sludge as a fertilizer.

Contrasting responses of gross and net nitrogen transformations to salinity in a reclaimed boreal forest soil

Plant growth is often affected by low soil nitrogen (N) availability and soil salinity in the Athabasca oil sands region (AOSR) of Alberta, Canada, as the reclaimed cover soil of peat–mineral soil mix (PMM) releases N slowly, and may be affected by salts moving upward from the underlying saline tailings sand (TS) or overburden (OB) materials used for land reclamation. Whether soil salinity affects N transformation and thus N availability is not clear. We studied the effect of soil salinity on net and gross N transformation rates in a reclaimed boreal forest soil in an incubation experiment using the 15N isotopic pool dilution technique. To simulate the salinity in reclaimed soils, sodium chloride was added to a PMM soil to form five salinity levels represented by electrical conductivity (EC) of 2, 4, 6, and 8 dS m−1 (based on 1:2 w/v soil to water ratio) and the control. Gross N mineralization, nitrification, and immobilization rates were significantly different among salinity levels, with the rates suppressed by high soil salinity, but they were not completely inhibited even when soil EC reached 8 dS m−1. As the soil EC increased from 2 to 8 dS m−1, gross N immobilization rates decreased faster than gross N mineralization rates, resulting in less negative net N mineralization rates at high salinity levels. The immobilization of NH4+-N was a greater process for NH4+-N consumption than nitrification and possible NH3 volatilization, regardless of the salinity level. In contrast to gross nitrification rates, net nitrification rates were not affected by soil salinity in the studied soil, indicating that the influence of soil salinity on NO3−-N production and consumption was similar. We conclude that soil salinity had different effects on gross versus net rates of soil N transformation and reduced N mineralization and nitrification rates under high soil salinity would lower N availability and thus increase the need for N fertilization in reclaimed soils.

Nitrogen fertilization improves the growth of lodgepole pine and white spruce seedlings under low salt stress through enhancing photosynthesis and plant nutrition

The effectiveness of nitrogen (N) fertilization in improving tree growth in saline forest soils is poorly understood. Hence, in this study, the interactive effect of N fertilization and salt stress on seedling physiology and growth was examined to improve our understanding of possible mechanisms for fertilization to mitigate salt stress. We compared physiological characteristics, growth, and foliar and root nutrient concentrations in lodgepole pine (Pinus contorta) and white spruce (Picea glauca) seedlings planted in a peat-mineral soil mix during a three months study with N fertilization (0 and 300mgN seedling−1) and salinity (0, 50, 100, 150mmolL−1 NaCl) in a greenhouse experiment. Nitrogen fertilization significantly increased net photosynthetic rates (Pn) and N concentrations in needles and roots, resulting in improved seedling height and root collar diameter growth and total seedling biomass for both species when seedlings were subjected to low salinity (50mmolL−1 NaCl), while it did not help tree growth under high salinity (150mmolL−1 NaCl). The physiological responses to combined salt stress and N fertilization did not differ between the two species; however, fertilization improved the growth of pine seedlings more than that of spruce seedlings under different salinity levels. The results suggest that the effectiveness of N fertilization in mitigating the salinity effect on seedling growth was species specific. Our study demonstrates that N fertilization improves tree growth through enhanced photosynthesis and N nutrition under low salinity and provides valuable insights into strategies to manage N nutrition in saline boreal forest soils.

Exponential fertilization promotes seedling growth by increasing nitrogen retranslocation in trembling aspen planted for oil sands reclamation

Vegetation reestablishment in land reclamation is often challenged by high mortality and slow growth of planted species because of low nutrient availability and severe understory competition. We tested the effectiveness of exponential fertilization in nursery trembling aspen (Populus tremuloides Michx.) seedling production for improving revegetation success on reconstructed soils in the Oil Sands in a two-year field experiment using a 2 (exponentially vs conventionally fertilized seedlings)×2 (weed intact vs weed removed) factorial design. The experiment was conducted on two different cover soil types: peat mineral soil mix (PMM) and LFH mineral soil mix (LFH). Nitrogen (N) retranslocation in outplanted seedlings was traced using 15N labeling. Exponential fertilization and weed removal increased height and root collar diameter growth but did not affect seedling survival over two growing seasons. Exponential fertilization increased new stem and leaf biomass and N content but decreased the percent allocation of biomass to roots. On average, 80% (on the PMM site) and 73% (on the LFH site) of total N demand of new tissues was met by internal N retranslocation. Exponential fertilization increased N retranslocation by 34% (P<0.01) and 25% (P=0.02) on the PMM and LFH sites, respectively. Weed competition reduced N retranslocation by 37% (P<0.01) and N uptake by seedlings from the soil by 61% (P=0.01) on the LFH site. We conclude that greater accumulation of nutrient reserves and greater N retranslocation helped to increase the growth of exponentially fertilized aspen seedlings that were outplanted for oil sands reclamation. Exponential fertilization of aspen seedlings for oil sands reclamation should be operationally tested for improving land reclamation in the Oil Sands.

Trace element transport in western Siberian rivers across a permafrost gradient

Abstract. Towards a better understanding of trace element (TE) transport in permafrost-affected Earth surface environments, we sampled ∼ 60 large and small rivers (&lt; 100 to ≤ 150 000 km2 watershed area) of the Western Siberian Lowland (WSL) during spring flood and summer and winter baseflow across a 1500 km latitudinal gradient covering continuous, discontinuous, sporadic and permafrost-free zones. Analysis of ∼ 40 major and TEs in the dissolved (&lt; 0.45 µm) fraction allowed establishing main environmental factors controlling the transport of metals and TEs in rivers of this environmentally important region. No statistically significant effect of the basin size on most TE concentrations was evidenced. Two groups of elements were distinguished: (1) elements that show the same trend throughout the year and (2) elements that show seasonal differences. The first group included elements decreasing northward during all seasons (Sr, Mo, U, As, Sb) marking the underground water influence of river feeding. The elements of the second group exhibited variable behavior in the course of the year. A northward increase during spring period was mostly pronounced for Fe, Al, Co, Zn and Ba and may stem from a combination of enhanced leaching from the topsoil and vegetation and bottom waters of the lakes (spring overturn). A springtime northward decrease was observed for Ni, Cu, Zr and Rb. The increase in element concentration northward was observed for Ti, Ga, Zr and Th only in winter, whereas Fe, Al, rare earth elements (REEs), Pb, Zr, and Hf increased northward in both spring and winter, which could be linked to leaching from peat and transport in the form of Fe-rich colloids. A southward increase in summer was strongly visible for Fe, Ni, Ba, Rb and V, probably due to peat/moss release (Ni, Ba, Rb) or groundwater feeding (Fe, V). Finally, B, Li, Cr, V, Mn, Zn, Cd, and Cs did not show any distinct trend from S to N. The order of landscape component impact on TE concentration in rivers was lakes &gt; bogs &gt; forest. The lakes decreased export of Mn and Co in summer and Ni, Cu, and Rb in spring, presumably due to biotic processes. The lakes enriched the rivers in insoluble lithogenic elements in summer and winter, likely due to TE mobilization from unfrozen mineral sediments. The rank of environmental factors on TE concentration in western Siberian rivers was latitude (three permafrost zones) &gt; season &gt; watershed size. The effect of the latitude was minimal in spring for most TEs but highly visible for Sr, Mo, Sb and U. The main factors controlling the shift of river feeding from surface and subsurface flow to deep underground flow in the permafrost-bearing zone were the depth of the active (unfrozen) seasonal layer and its position in organic or mineral horizons of the soil profile. In the permafrost-free zone, the relative role of carbonate mineral-bearing base rock feeding versus bog water feeding determined the pattern of TE concentration and fluxes in rivers of various sizes as a function of season. Comparison of obtained TE fluxes in WSL rivers with those of other subarctic rivers demonstrated reasonable agreement for most TEs; the lithology of base rocks was the major factor controlling the magnitude of TE fluxes. Climate change in western Siberia and permafrost boundary migration will essentially affect the elements controlled by underground water feeding (DIC, alkaline earth elements (Ca, Sr), oxyanions (Mo, Sb, As) and U). The thickening of the active layer may increase the export of trivalent and tetravalent hydrolysates in the form of organo-ferric colloids. Plant litter-originated divalent metals present as organic complexes may be retained via adsorption on mineral horizon. However, due to various counterbalanced processes controlling element source and sinks in plant–peat–mineral soil–river systems, the overall impact of the permafrost thaw on TE export from the land to the ocean may be smaller than that foreseen with merely active layer thickening and permafrost boundary shift.

Nitrogen transformation rates are affected by cover soil type but not coarse woody debris application in reclaimed oil sands soils

This study was conducted to test if applying coarse woody debris (CWD) can increase nitrogen (N) transformation rates and N availability in cover soils, forest floor mineral soil mix (FMM) and peat mineral soil mix (PMM), commonly used for reclamation of open-pit oil sands mining disturbed land in northern Alberta, Canada. Mean rates of net N mineralization and nitrification rates were greater (p<0.05) in FMM than in PMM due to greater microbial and enzyme activities in FMM. Applying CWD increased gross N mineralization and nitrification rates as well as N immobilization rates, resulting in lack of difference in net N mineralization and N supply rates between near and away from CWD. Using FMM as a cover soil for land reclamation post open-pit oil sands miningis better choice relative to PMM. Applying CWD for land reclamation is recommended to create spatial variability and diverse microsites.

Coarse woody debris effects on greenhouse gas emission rates depend on cover soil type in oil sands reclamation

Peat mineral soil mix (PMM) and forest floor mineral soil mix (FMM) are cover soils commonly used for land reclamation, while coarse woody debris (CWD) can be added to create structural diversity and provide an additional source of organic matter. However, the effect of cover soil type and CWD on emission rates of greenhouse gases, such as carbon dioxide (CO2) methane (CH4) and nitrous oxide (N2O) in reclaimed oil sands soils has not been studied. Soil respiration, CH4 uptake and N2O emission rates were studied in a factorial experiment consisting of 2 cover soils (FMM vs PMM)×2 sampling distances from the CWD (near vs away from CWD). Greenhouse gas emission rates were measured in July, August, and September 2012 and 2013 using static chambers. Soil respiration rates were greater in FMM than in PMM regardless of the distance from CWD at each sampling time (p<0.05). Rates ranged from 461 to 1148 and 293 to 677mg CO2 m−2h−1 for FMM and PMM, respectively, in 2012, and from 355 to 1318 and 235 to 700mg CO2 m−2h−1, respectively, in 2013. The CWD increased soil respiration by 22–33% in FMM but not in PMM. Soil respiration rates were positively related to microbial biomass carbon (p=0.004) and nitrogen (p<0.001). Soil respiration rates decreased from July to September in 2012 and 2013, and were positively related to soil temperature (p<0.01) but not with soil water content measured at 5cm depth. Methane uptake rates were greater in FMM (0.026–0.037) than in PMM (0.015–0.028mg CH4 m−2h−1). The CWD increased CH4 uptake rates only in July and August 2012 in FMM, and were negatively related to soil water content (p<0.001) but not to soil temperature. Nitrous oxide emission rates (0.001–0.016mgN2Om−2h−1) were not affected by either cover soil type or CWD. Global warming potential of CO2, CH4 and N2O effluxes was greater in FMM than in PMM and near CWD than away from CWD, especially in FMM. Our study demonstrates that applying CWD for oil sands reclamation increases organic matter decomposition (increased CO2 evolution), driven by the effect on microbial populations. Results from this study provide support to findings in earlier studies that CWD application benefits vegetation establishment through enhancing soil processes in reclaimed oil sands lands.

Coarse Woody Debris Increases Microbial Community Functional Diversity but not Enzyme Activities in Reclaimed Oil Sands Soils.

Forest floor mineral soil mix (FMM) and peat mineral soil mix (PMM) are cover soils commonly used for upland reclamation post open-pit oil sands mining in northern Alberta, Canada. Coarse woody debris (CWD) can be used to regulate soil temperature and water content, to increase organic matter content, and to create microsites for the establishment of microorganisms and vegetation in upland reclamation. We studied the effects of CWD on soil microbial community level physiological profile (CLPP) and soil enzyme activities in FMM and PMM in a reclaimed landscape in the oil sands. This experiment was conducted with a 2 (FMM vs PMM) × 2 (near CWD vs away from CWD) factorial design with 6 replications. The study plots were established with Populus tremuloides (trembling aspen) CWD placed on each plot between November 2007 and February 2008. Soil samples were collected within 5 cm from CWD and more than 100 cm away from CWD in July, August and September 2013 and 2014. Microbial biomass was greater (p<0.05) in FMM than in PMM, in July, and August 2013 and July 2014, and greater (p<0.05) near CWD than away from CWD in FMM in July and August samplings. Soil microbial CLPP differed between FMM and PMM (p<0.01) according to a principal component analysis and CWD changed microbial CLPP in FMM (p<0.05) but not in PMM. Coarse woody debris increased microbial community functional diversity (average well color development in Biolog Ecoplates) in both cover soils (p<0.05) in August and September 2014. Carbon degrading soil enzyme activities were greater in FMM than in PMM (p<0.05) regardless of distance from CWD but were not affected by CWD. Greater microbial biomass and enzyme activities in FMM than in PMM will increase organic matter decomposition and nutrient cycling, improving plant growth. Enhanced microbial community functional diversity by CWD application in upland reclamation has implications for accelerating upland reclamation after oil sands mining.

Fine root dynamics in lodgepole pine and white spruce stands along productivity gradients in reclaimed oil sands sites.

Open-pit mining activities in the oil sands region of Alberta, Canada, create disturbed lands that, by law, must be reclaimed to a land capability equivalent to that existed before the disturbance. Re-establishment of forest cover will be affected by the production and turnover rate of fine roots. However, the relationship between fine root dynamics and tree growth has not been studied in reclaimed oil sands sites. Fine root properties (root length density, mean surface area, total root biomass, and rates of root production, turnover, and decomposition) were assessed from May to October 2011 and 2012 using sequential coring and ingrowth core methods in lodgepole pine (Pinus contorta Dougl.) and white spruce (Picea glauca (Moench.) Voss) stands. The pine and spruce stands were planted on peat mineral soil mix placed over tailings sand and overburden substrates, respectively, in reclaimed oil sands sites in Alberta. We selected stands that form a productivity gradient (low, medium, and high productivities) of each tree species based on differences in tree height and diameter at breast height (DBH) increments. In lodgepole pine stands, fine root length density and fine root production, and turnover rates were in the order of high > medium > low productivity sites and were positively correlated with tree height and DBH and negatively correlated with soil salinity (P<0.05). In white spruce stands, fine root surface area was the only parameter that increased along the productivity gradient and was negatively correlated with soil compaction. In conclusion, fine root dynamics along the stand productivity gradients were closely linked to stand productivity and were affected by limiting soil properties related to the specific substrate used for reconstructing the reclaimed soil. Understanding the impact of soil properties on fine root dynamics and overall stand productivity will help improve land reclamation outcomes.

Coarse woody debris extract decreases nitrogen availability in two reclaimed oil sands soils in Canada

Forest floor mineral soil mix (FMM) and peat mineral soil mix (PMM) are common cover soils and sources of organic matter for reclamation of open-pit mining disturbed land in the Athabasca oil sands region. Coarse woody debris (CWD) can be an additional source of organic matter and can provide nutrient and habitat for plant growth. However, the effect of CWD on nitrogen (N) cycling in reclaimed oil sands soils has not been studied. A laboratory incubation experiment was conducted to assess chemical effects of a CWD extract on gross and net N transformation rates in FMM and PMM using the 15N pool dilution method. The CWD extract was used to simulate CWD leachates (with rainwater as a control) that are produced in the field. The effect of the simulated CWD leachate on the cover soils was studied in a 2 (FMM vs PMM)×2 (CWD extract vs rainwater addition) factorial design. There was no difference in gross N mineralization rates between FMM and PMM, although net N mineralization rates were greater in FMM than in PMM (p<0.001) due to greater NH4+ immobilization rates in PMM. Gross and net nitrification rates were greater in FMM than in PMM (p<0.001). The ratio of gross nitrification to gross NH4+ immobilization rates (N/IA) was greater in FMM than in PMM (p<0.001), as the greater NH4+ immobilization rates in PMM decreased gross nitrification rates by decreasing NH4+ availability. Addition of the CWD extract decreased gross (p<0.01) and net (p<0.001) N mineralization rates, increased (p<0.001) NH4+ immobilization and decreased (p<0.001) gross nitrification rates in both cover soils. The N/IA ratios were decreased by the CWD extract addition, indicating that heterotrophic NH4+ immobilization was superior to autotrophic nitrification due to the high C/N ratio of the CWD extract. We conclude that FMM will have greater N availability for oil sands reclamation than PMM. Leachates from CWD would decrease N availability by decreasing gross N mineralization and nitrification rates and by increasing N immobilization rates.

The role of seedling nutrient status on development of ectomycorrhizal fungal communities in two soil types following surface mining disturbance

Abstract Severe disturbances, such as those caused by surface mining, sever connections between ectomycorrhizal (ECM) fungi and their hosts. In this study, we examined the importance of internal plant nutritional status and soil type on the abundance and composition of ECM communities in newly established reclamation areas. Ectomycorrhizal fungi were examined on two aspen (Populus tremuloides) seedling stock types that differed in root nutrient concentrations at time of planting. Stock types were planted into two salvaged soil types, an upland forest soil and a lowland peat-mineral soil mix, placed on a reclaimed mining site. Two growing seasons following planting, ECM fungal richness and abundance was low with only four operational taxonomic units identified across the reclamation site. Initial seedling nutrient status affected the total amount of ECM fungi on seedling roots; seedlings with initially high root nutrient reserves (N, P and starch) had more root tips colonized by ECM fungi than seedlings with initially lower nutrient tissue concentrations. Soil type did not affect total amount of ECM colonization; however, the relative abundance of an individual species, Cenococcum geophilum, was influenced by soil type. Seedling nutrient reserves, independent of soil nutrition, affects the amount of ECM root colonization, while soil type affects the relative abundance of some ECM fungi colonizing roots.

Imaging tropical peatlands in Indonesia using ground-penetrating radar (GPR) and electrical resistivity imaging (ERI): implications for carbon stock estimates and peat soil characterization

Abstract. Current estimates of carbon (C) storage in peatland systems worldwide indicate that tropical peatlands comprise about 15% of the global peat carbon pool. Such estimates are uncertain due to data gaps regarding organic peat soil thickness, volume and C content. We combined a set of indirect geophysical methods (ground-penetrating radar, GPR, and electrical resistivity imaging, ERI) with direct observations using core sampling and C analysis to determine how geophysical imaging may enhance traditional coring methods for estimating peat thickness and C storage in a tropical peatland system in West Kalimantan, Indonesia. Both GPR and ERI methods demonstrated their capability to estimate peat thickness in tropical peat soils at a spatial resolution not feasible with traditional coring methods. GPR is able to capture peat thickness variability at centimeter-scale vertical resolution, although peat thickness determination was difficult for peat columns exceeding 5 m in the areas studied, due to signal attenuation associated with thick clay-rich transitional horizons at the peat–mineral soil interface. ERI methods were more successful for imaging deeper peatlands with thick organomineral layers between peat and underlying mineral soil. Results obtained using GPR methods indicate less than 3% variation in peat thickness (when compared to coring methods) over low peat–mineral soil interface gradients (i.e., below 0.02°) and show substantial impacts in C storage estimates (i.e., up to 37 MgC ha−1 even for transects showing a difference between GPR and coring estimates of 0.07 m in average peat thickness). The geophysical data also provide information on peat matrix attributes such as thickness of organomineral horizons between peat and underlying substrate, the presence of buried wood, buttressed trees or tip-up pools and soil type. The use of GPR and ERI methods to image peat profiles at high resolution can be used to further constrain quantification of peat C pools and inform responsible peatland management in Indonesia and elsewhere in the tropics.

Limiting factors for lodgepole pine (Pinus contorta) and white spruce (Picea glauca) growth differ in some reconstructed sites in the Athabasca oil sands region

Peat-mineral soil mix (PMM) over tailings sand (TS) or overburden (OB) is a commonly used prescription for oil sands reclamation. The TS and OB (the substrates) often have unfavorable conditions such as high salinity, soil compaction, low nutrient availability in OB, and low nutrient and water availabilities in TS, which may limit tree growth. The objective of this study was to identify limiting factors for growth of lodgepole pine (Pinus contorta) on PMM over TS and white spruce (Picea glauca) on PMM over OB in the Athabasca oil sands region, Alberta, Canada. In the pine sites, mean annual growth of height (HG), diameter at breast height (DBHG) and aboveground biomass (ABG) were significantly correlated with volumetric water content (VWC) in PMM and foliar δ13C in current-year needles. Sites with high productivities had the lowest foliar δ13C relative to sites with low and medium productivities. The VWC and dissolved organic carbon (DOC) together explained 80% of the variation in both the current annual increment of height (HI) (p=0.007) and aboveground biomass (ABI) (p=0.008). In the spruce sites, foliar potassium (K) and foliar and soil nitrogen (N) concentrations were positively correlated with HG, DBHG and ABG, consistent with patterns in K and inorganic N (the sum of NH4+-N and NO3−-N) concentrations in PMM in those sites. Soil electrical conductivity (EC) and bulk density (Db) were greater in low than in medium and high productivity sites. The Db and inorganic N concentration together explained 67% of the variation in HI (p=0.037), while Db and EC together explained 79% of the variation in ABI (p=0.009). In conclusion, lodgepole pine trees planted on PMM over TS sites were limited by low water availability, while low soil N availability and high salinity limited the growth of white spruce trees planted on PMM over OB sites. Reclamation practices need to address water and nutrient limitations to ensure the success of reclaiming disturbed areas in the oil sands region.

Organic capping type affected nitrogen availability and associated enzyme activities in reconstructed oil sands soils in Alberta, Canada

Organic materials applied in land reclamation play a key role in the development of ecosystem properties and functions. Peat mineral soil mix (PMM) and LFH (identifiable litter (L), fragmented litter (F) and humus (H)) mineral soil mix (LFH) are commonly used organic amendments for oil sands reclamation in northern Alberta. These materials have contrasting soil properties, with organic matter in LFH more decomposed and having a lower carbon-to-nitrogen (C:N) ratio than that in PMM. We quantified the effects of LFH and PMM capping material on N availability and enzyme activities during early ecosystem development in the oil sands region. Monthly samples were taken from 0 to10 and 10 to 20cm layers from June through October in 2011 and 2012. The N availability and activities of soil enzymes including β-1,4-N-acetyl glucosaminidase (NAGase), urease, arylamidase and protease were measured. In-situ N availability was measured using plant root simulator (PRS™) probes. Repeated measures ANOVA indicated that N availability and NAGase, arylamidase and protease activities were greater in LFH than in PMM and were affected by time of sampling. These differences were attributed to the lower C:N ratio in LFH than in PMM. We found greater N availability and enzyme activities in the fall than in the summer in both years. These differences were likely caused by fresh labile C inputs through root exudates and litter fall during fall that induced greater enzyme activities and led to greater N mineralization despite the potential limitation by the lower fall temperature. Overall, the greater N availabilities and enzyme activities in LFH suggest that LFH would be a better soil capping material than PMM for early ecosystem development in oil sands reclamation.