British Columbia Soils Research Articles

In vitro bioaccessibility round robin testing for arsenic and lead in standard reference materials and soil samples.

In this study, we assessed the suitability of using a standard reference material (SRM) other than National Institute of Standards and Technology (NIST) 2710a or NIST 2711a in USEPA Method 1340 to determine arsenic (As) and lead (Pb) in vitro bioaccessibility (IVBA) and the capabilities of Canadian-based laboratories to perform the method. Five laboratories participated in an initial round robin study and analyzed NIST 2710a, NIST 2711a, BGS119, and Enviromat SS-2. Intra- and inter-laboratory variability were generally acceptable with percentage relative standard deviations (RSD) of less than 20%. The mean total As and Pb concentrations obtained for BGS119 (332 and 936 mg/kg, respectively) and the mean IVBA values (As = 14.3% and Pb = 78.1%) suggested it may be a suitable and acceptable SRM, whereas the concentration of As in Enviromat SS-2 as received (3.2 mg/kg) was deemed too low. Ten soil samples from sites with varying land use were analyzed in a follow-up round robin study using the modified IVBA method that included BGS119 as SRM. The concentrations of As and Pb in the IVBA extracts reported by the participating laboratories were comparable. The mean As IVBA values for the field-collected samples ranged from 0.1% to 56.4%; for Pb, they ranged from 7.0% to 121%. The lowest IVBA values were measured in mine site samples; the highest values were associated with smelter-affected soils. The low IVBA values correlated with high iron content. Intra- and interlaboratory reproducibility were acceptable (RSD < 30%). Based on the findings of the study, laboratories can use the modified method to provide reproducible and comparable As and Pb IVBA data. The use of BGS119 as an alternative SRM to assess contaminated sites in the province of British Columbia for regulatory purposes is recommended, as it is representative of As and Pb concentrations in contaminated soils in British Columbia. Integr Environ Assess Manag 2024;20:1486-1495. © 2024 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals LLC on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

Forest Management Impacts on Greenhouse Gas Fluxes from Riparian Soils Along Headwater Streams

Increasing concentrations of atmospheric greenhouse gases (GHGs; CO2, CH4, N2O) cause climate change. Depending on the conditions, soils have the potential to store carbon or to be a source of GHGs to the atmosphere. Riparian soils in particular have high potential to store carbon, but also to be sources of CH4 and N2O. Headwater streams make up a large proportion of stream length in a drainage network, and their riparian zones have valuable ecosystem functions. In parallel, the riparian zones of headwater streams are particularly vulnerable to forest harvest. Studies of GHG fluxes from these unique ecosystems remain limited. Our objective was to quantify the effects of forestry practices and groundwater discharge (DIS) areas on GHG emissions from riparian forest soils in coastal British Columbia. We compared nine sites with three different forest management protocols: (1) harvesting with a riparian buffer, (2) no buffer, and (3) reference sites without harvesting. We measured gas fluxes, soil temperature, soil moisture and depth to the groundwater table alongside headwater streams monthly over one growing season. We found that CH4 uptake rates were 65% lower at the no buffer sites, and N2O emission rates were 52% lower at the no buffer sites, when compared to the reference sites. Additionally, CH4 uptake was 54% lower at DIS areas than in non-DIS areas. The results of our research help inform forest management by demonstrating that maintaining riparian buffers can be effective in protecting the ecosystem functions contributing to soil GHG fluxes.

Phosphorus saturation index and water-extractable phosphorus in high-legacy phosphorus soils in southern British Columbia, Canada

Understanding of the risk of phosphorus (P) loss to the environment is crucial to monitor soil P and implement policies for P management. We assessed P sorption characteristics and adapted a P saturation index (PSI) for silage corn and blueberry fields in south coastal British Columbia (BC), Canada. We used 284 composite soil samples with contrasting P levels collected from eight silage corn and 23 blueberry fields across south coastal BC. The P sorption maximum (Smax) varied between 982 and 2532 mg P·kg−1 and was influenced by aluminum concentration and organic matter content. The degree of P saturation was related to water-extractable P (Pw) by a quadratic regression with R2 = 0.85. A critical Pw = 3.7 mg·kg−1 was established across the two cropping systems. The silage corn fields with pH &gt; 5.5 had critical PSI value of 10.4%, and blueberry fields with pH &lt; 4.7 had critical PSI value of 18.0%. These results showed that the risk of P loss from soil in the silage corn was high, but it was low for blueberry because the critical PSI for silage corn fields was lower than for blueberry fields, and therefore, saturation would be more easily reached, even though more P is applied to blueberry fields. The combination of a critical PSI and Pw as agri-environmental indicators will help farmers and professionals to identify fields with risk of P loss, to implement a nutrient management plan, and to monitor how this risk changes with time.

Combined Starter Phosphorus and Manure Applications on Silage Corn Yield and Phosphorus Uptake in Southern BC

Phosphorus (P) management using mineral and manure P in excess of plant needs contributes to legacy soil P in coastal British Columbia, Canada. The objectives of this study were (a) to assess the effects of starter P at early growth stages and their carryover through corn maturity, and (b) to determine how corn yields relate to soil P saturation indicators. Eleven 1-year experiments were conducted on sites with contrasting legacy soil P in 2018 (three sites) and 2019 (eight sites). Six combinations of starter and manure P rates (T1: 0Pstarter + 0Pmanure; T2: 0Pstarter + 35Pmanure; T3: 5Pstarter + 30Pmanure; T4: 10Pstarter + 25Pmanure; T5: 15Pstarter + 20Pmanure; T6: 20Pstarter + 15Pmanure) were assigned to a RCBD with four replicates. In 2018, corn dry matter weight (DMW) at the 6-leaf stage was affected by starter P in all sites, and the response curve was described by a linear-plus-plateau model with critical starter P of 5 and 7.5 kg ha 1. In 2019, corn DMW at early growth stages was not affected by starter P. Corn DMW at harvest varied between 15.15 Mg ha–1 in sites with low initial soil P and 27.20 Mg ha–1 in sites with excess P. Four sites exhibited a trend of high DMW with treatment comprising low starter P and high side-dressed manure P additions. The degree of P saturation (DPS, 14% to 38%) and P saturation index (PSI, 3% to 14%) were related to corn DMW by quadratic functions (R2 = 0.76 - 0.94). From these results, we can conclude that the effect of starter P on young corn plants varies with year, but does not carryover through harvest. Moreover, current starter P (30 - 40 kg ha–1) recommended for corn can be reduced by up to 75% (5 - 7.5 kg ha–1) without affecting yield, thus reducing annual P inputs and farmers’ production costs. Finally, PSI as a proxy of DPS is a possible agro-environmental indicator that, coupled with reduced starter P fertilizer, can further contribute to reducing the risk of P transfer from agricultural soils in coastal British Columbia.

Soil disturbance and juvenile Douglas-fir growth following stump removal on moderately coarse textured soils in southwestern British Columbia: 10-year results

Mechanized treatment for root diseases such as Coniferiporia sulphurascens (Pilát) L. W. Zhou &amp; Y. C. Dai (syn. Phellinus sulphurascens Pilát) and Armillaria ostoyae (Romagn.) Herink (syn. Armillaria solidipes Peck) is often avoided due to cost or the perception that removal of stumps creates detrimental soil disturbance or degradation that hinders site productivity. Our study tested five diseased stands that were treated by extracting stumps following harvesting and replanted with susceptible Douglas-fir. Soil disturbance surveys were conducted in treated and untreated plots, and individual planted spots were assessed and categorized for soil disturbance using existing and proposed new categories specific to disturbance caused by the stump removal. Tree measurements were taken at intervals over the first 10 years of stand development, and foliage was sampled for nutrient analysis. The percentage of total and counted disturbance was 20%–46% and 8%–11% greater, respectively, in treated versus untreated plots; however, mean tree growth in height and diameter was not statistically different between treatments and was more positive for treated plots at all sites but one. Tree nutrition and survival to age 10 was not negatively affected by stump removal. Total site productivity represented by basal area and tree volume differed widely between sites but was not significantly different between treatments.

Long-term grazing effects on rough fescue grassland soils in southern British Columbia

Krzic, M., Lamagna, S. F., Newman, R. F., Bradfield, G. and Wallace, B. M. 2014. Long-term grazing effects on rough fescue grassland soils in southern British Columbia. Can. J. Soil Sci. 94: 337–345. Rough fescue (Festuca campestris Rydb.) is a highly palatable forage species with little resistance to continuous grazing. The objective of this study was to evaluate the effects of long-term cattle grazing on soil properties, above-ground biomass, and canopy cover of key grass species on rough fescue grasslands in the southern interior British Columbia. Soil and vegetation properties were determined on a total of six open grassland sites located at the Lac du Bois and Hamilton Mountain. At all sites, grazing use has decreased over time, with the heaviest grazing occurring prior to 1960. The long-term (25–75 yr) elimination of grazing on these semi-arid grasslands has led to greater above-ground biomass and canopy cover of rough fescue, as well as increased soil polysaccharides; however, no differences in total soil C, N, and aggregate stability were found between pastures with and without grazing. Both soil bulk density and mechanical resistance were greater on grazed plots compared with those without grazing, with differences being more pronounced at the Hamilton Mountain location. The current grazing regime has not allowed for the elimination of negative effects of overgrazing on soil compaction on these rough fescue grasslands, especially at the location that continued to be grazed more heavily (i.e., Hamilton Mountain). Our findings suggest that soils in these grazing-sensitive grasslands need more than 75 yr to fully recover from the impacts of overgrazing.

Soils of temperate rainforests of the North American Pacific Coast

Temperate rainforests have high conservation and natural resource value, but the soils of this bioregion have not previously been studied as a unit. Here we examine the soils of North America's Pacific coastal temperate rainforests, utilizing databases from the United States Natural Resources Conservation Service and the Canadian Centre for Land and Biological Resources Research to (i) identify the soil taxa, (ii) evaluate the soil properties, and (iii) compare soils in temperate and tropical rainforests. There are strong climate gradients within these temperate rainforests, with the mean temperature declining from 11.7°C to 6.1°C and the mean annual precipitation increasing from 1500mm to around 3000mm from northern California (CA) to northwestern British Columbia (BC) and southeastern Alaska (AK). There is also high pedodiversity in this region, with soils representing 8 orders and 31 suborders, and, in the US portion, 65 great-groups, 142 subgroups, and 482 soil series. Twenty-six percent of described soil series are endemic to temperate rainforests in the US portion of the region, with the proportion declining with latitude. Dominant soil suborders vary along the latitudinal gradient from Humults–Udalfs/Ustalfs–Udepts–Udults in CA, to Udands–Udepts–Udands Humults in western Oregon (OR) and Washington (WA), to Orthods–Folists in BC and Cryods–Saprists in AK. The dominant diagnostic horizons are ochric/argillic (CA), umbric/cambic (OR, WA), and albic–histic/spodic (BC, AK). Whereas soils in CA, BC, and AK tend to have a mixed mineralogy, those in northern OR and WA commonly are derived from volcaniclastic materials and have a ferrihydritic or isotic mineralogy. Soils in this region are generally deep, hold abundant moisture, are not subject to deep-freezing, and are enriched in extractable Fe and Al. Organic C and total N contents are high overall, but also variable, with right-skewed distributions. Compared to tropical rainforest soils in the Pacific Basin, Pacific temperate rainforest have greater weatherable minerals, cation-exchange capacities, soil organic C, and total exchangeable base cations. However, soils of both bioregions tend to be deep, acidic Al-saturated, and can have large N reservoirs. This investigation provides a foundation for a more unified understanding of the soils of a globally significant bioregion.

Comparison of surface properties of synthetic and soil struvite

Baugé, S. M. Y., Lavkulich, L. M., Wilson, J. E. and Schreier, H. E. 2014. Comparison of surface properties of synthetic and soil struvite. Can. J. Soil Sci. 94: 169–176. X-ray, Raman and nuclear magnetic resonance (NMR) analyses of intensively managed agricultural soils in southwestern British Columbia reported the presence of the Mg-phosphate mineral, struvite. Soils are heterogeneous, thus analytical techniques based on single minerals require calibration in order to provide reliable results. A synthetic struvite was used to compare the properties of the soil phosphate with struvite. The results confirmed the presence of struvite and possibly additional species of Mg. Time of flight–secondary ion mass spectroscopy (TOF-SIMS) revealed that the surface of struvite, to 2nm depth, is dominated by Mg with other cations, notably Fe and NH4 that were measured in minor amounts and were associated with the Mg rich surface layer. The results suggest that P is located within the struvite structure. Chemical reactions of struvite and phosphorus chemistry in these soils appear to be governed by the Mg surface layer.

Brunisolic soils of Canada: Genesis, distribution, and classification

Smith, C. A. S., Webb, K. T., Kenney, E., Anderson, A. and Kroetsch, D. 2011. Brunisolic soils of Canada: Genesis, distribution, and classification. Can. J. Soil Sci. 91: 695–717. Brunisols are considered as moderately developed soils formed under forest cover. They have a wide range of physical and chemical properties and no single dominant pedogenic process drives the development of these soils. Brunisols are some of the more common soils in Canada, occupying over 1.2 million km2 of land, roughly equivalent to the area of Podzolic soils, and about half the area of the most common soil order in Canada, the Cryosols. Brunisols occur mainly within the boreal forest regions, but extend across the country with the exception of the Arctic and prairie regions. Within the zone of discontinuous permafrost they co-exist on landscapes with Cryosols. In humid regions of both eastern and western Canada they form a continuum of soil development with Podzolic soils. Within subhumid to semi-arid regions they often co-exist with Luvisolic soils, occurring on parent materials too coarse to enable Luvisolic soil formation. Brunisols equate closely to the Cambisol reference group in the World Reference Base taxonomic system and to several suborders of the Inceptisol order in Soil Taxonomy. Both Melanic and Sombric Brunisols are important agricultural soils in British Columbia, Ontario and the Maritime provinces. Eutric and Dystric Brunisols support commercial forest stands throughout the boreal forest and western cordillera of Canada.

Early Growth Responses of Lodgepole Pine and Douglas-Fir to Soil Compaction, Organic Matter Removal, and Rehabilitation Treatments in Southeastern British Columbia

Abstract Effects of soil compaction, organic matter removal, and rehabilitation on lodgepole pine (Pinus contorta Dougl. ex. Loud.) and Douglas-fir (Pseudotsuga menziesii var. menziesii) were studied after three growing seasons in a long-term soil productivity study established on three calcareous soils in southeastern British Columbia. Effects of soil compaction and organic matter removal on tree growth were site and species specific. Moderate soil compaction increased the diameter and height increment of both species within the stem-only harvest treatment on all three sites, particularly at the coarser textured site (Emily Creek). Compaction tended to reduce tree mortality. Growth of both species was reduced by forest floor removal in the noncompacted soil at Mud Creek and Emily Creek and by whole-tree harvest in the moderately compacted soil at Mud Creek and Kootenay East, possibly due to treatment-induced water limitation. Whole-tree harvest and forest floor removal stimulated lodgepole pine and Douglas-fir growth in the noncompacted soil at Kootenay East. The rehabilitation treatment (established by tilling a heavily compacted soil) reduced lodgepole pine tree mortality on all sites and increased rootcollar diameter and height increment at Mud Creek and Kootenay East. Our findings may provide early growth indication and help assess long-term tree growth trends at these and other long-term soil productivity or related sites.

Maximum Bulk Density of British Columbia Forest Soils from the Proctor Test: Relationships with Selected Physical and Chemical Properties

The widespread use of heavy equipment during timber harvesting and site preparation can lead to reduced soil productivity and warrants development of new methods to assess compaction. We evaluated the effects of soil particle density, organic matter, particle size distribution, extractable oxides, and plastic and liquid limits on the maximum bulk density (MBD) of forest soils in British Columbia. Soil samples were collected from 33 sites throughout British Columbia, covering the major forest and soil types of the province. The standard Proctor test was used to determine MBD and related parameters, including the gravimetric water content (WMBD) and porosity (fMBD) at which MBD was achieved. The significance levels of single soil properties in predicting MBD were in the order plastic and liquid limits, organic matter, oxalate‐extractable oxides, and particle size distribution. For all samples, liquid limit and clay were most closely related to MBD (R2 = 0.83). Addition of organic matter to the model increased the regression coefficients, and oxidizable organic matter caused a greater increase than did total C. Stratification of the sample set into groups based on plasticity led to higher R2 values in multiple regressions, and different soil properties were important for nonplastic soils than for those with high, moderate, and low plasticity. Prediction with multiple regression explained the most variation in MBD for nonplastic soils, while properties of highly plastic soils explained the least variation in MBD and moderately plastic soils were intermediate. Based on our findings, we propose an approach for using MBD to help better interpret bulk density data in forest soil compaction studies.

Genetic diversity of Metarhizium anisopliae var. anisopliae in southwestern British Columbia

The abundance and genetic diversity of the entomopathogenic fungus, Metarhizium anisopliae var. anisopliae, in southwestern British Columbia (BC) and southern Alberta was examined. The fungus was found to be widespread in soil throughout southwestern BC, and was recovered from 56% of 85 sample sites. In contrast to southwestern BC, no M. anisopliae isolates were recovered in southern Alberta. An automated fluorescent amplified fragment length polymorphism (AFLP) method was used to examine genetic diversity. In excess of 200 isolates were characterized. The method identified 211 polymorphic amplicons, ranging in size from ≈92 to 400 base pairs, and it was found to be reproducible with a resolution limit of 86.2% similarity. The AFLP method distinguished Metarhizium from other entomopathogenic fungal genera, and demonstrated considerable genetic diversity (25 genotypes) among the reference strains of M. anisopliae isolates examined (i.e. recovered from various substrates and geographical locations). Although 13 genotypes of M. anisopliae var. anisopliae were recovered from southwestern BC soils, the vast majority of isolates (91%) belonged to one of two closely-related genotypes. Furthermore, these two genotypes predominated in urban, agricultural and forest soils. The reasons for the limited diversity of M. anisopliae var. anisopliae in southwestern BC are uncertain. However, findings of this study are consistent with island biogeography theory, and have significant implications for the development of this fungus for microbial control of pest insects.

Changes in soil properties, tree growth, and nutrition over a period of 10 years after stump removal and scarification on moderately coarse soils in interior British Columbia

Silvicultural site preparation treatments that involve severe soil and forest floor disturbance may, in the long-term, reduce soil productivity and negate the initial increased forest productivity obtained by controlling root diseases or vegetation. The effect of a range of stump removal treatments on selected soil chemical and physical properties, and growth of planted lodgepole pine ( Pinus contorta) and hybrid spruce ( Picea glauca (Moench) Voss × Picea engelmanii Parry), was examined at three sites in the Interior Cedar–Hemlock (ICH) zone of British Columbia. Changes in forest floor and mineral soil chemistry and bulk density were measured 1 year after treatment and again 9 years later. Tree growth and foliar nutrient status of planted seedlings were measured 3, 5 and 10 years after planting. Forest floor mass and depth were altered by treatment, and decreased significantly between years 1 and 10. Mineral soil bulk density was greater in all stump-removal treatments than in the non-stumped treatment in year 1; however, 10 years after treatment, bulk densities had decreased and no treatment effects were apparent. Changes in forest floor chemistry that were measured in year 1 had largely disappeared by year 10. Mineral soil chemical concentrations were not affected by treatment at any time, except for a significant increase in carbon (C) concentration between years 1 and 10. Lodgepole pine height and diameter were increased over the measurement period by the most intense, scarified treatment, whereas spruce growth was largely unaffected by stump removal treatment. Both tree growth and soil measurements suggest that, on the moderately coarse soils within the climatic regime of the present study, soil limits to tree growth have not been exceeded.

Emission of legacy chlorinated pesticides from agricultural and orchard soils in British Columbia, Canada

Air samples were collected above agricultural fields in the Fraser Valley and orchards in the Okanagan Valley, British Columbia, Canada, to investigate volatilization of organochlorine pesticides used in the past. Concentrations of pesticides in air were elevated over soils that contained higher residues. Soil/air fugacity ratios at sites with the higher soil residues were calculated relative to air sampled at 40 cm height and background air. The fugacity ratios in the first case indicated net volatilization or soil-air equilibrium for most compounds and occasional net deposition for p,p'-dichlorodiphenyldichloroethene (p,p'-DDE), whereas those in the second case showed a strong potential for net volatilization of all compounds. The enantiomer fraction (EF) of chiral compounds alpha-hexachlorocyclohexane (alpha-HCH), trans-chlordane, cis-chlordane, and o,p'-DDT were determined in overlying air samples and soils. Enantiomer fractions in air corresponded to those in soils at fields in which soil concentrations were high but were decoupled from soil signatures at fields with low soil residues. Mean EFs in air sampled over soils were significantly (p < 0.001) nonracemic for alpha-HCH and the chlordanes and agreed with published EFs in regional ambient air. The mean EF of o,p'-DDT for all air samples did not show a significant deviation from racemic EFs (p > 0.2), but EFs of individual samples reflected the ambivalent nature of o,p'-DDT degradation, sometimes preferring the (+) enantiomer and other times the (-) enantiomer. The study indicates that soils are continuing to emit "legacy" pesticides into the regional atmosphere.

Binding of inorganic sulphate and phosphate in humid-climate soils measured using column leaching, equilibration and extraction methods

The ability of soil samples to bind applications of inorganic sulphate and phosphate was examined in the laboratory using column leaching, solution equilibration and extraction methods. Eleven soil samples from the Fraser Valley of British Columbia with a range of soil characteristics and management histories were examined. Column leaching trials showed that sulphate was bound to soils, but not as strongly as phosphate. There was no evidence of significant sulphate binding during the equilibration trials but there was substantial native sulphate bound by the soils as shown by extraction of significant sulphate concentrations by bicarbonate extraction following equilibration. This shows that sulphate is not bound according to the traditional theory of adsorption, but other undefined mechanisms are involved. Both column leaching and equilibration results showed that the samples studied varied considerably in their native phosphate retention attributes, with some samples releasing no phosphate and others releasing considerable phosphate into the water treatments. Equilibration trials showed that some of the soils bound large quantities of phosphate resulting in no phosphate in the soil solution whereas others bound much less resulting in significant phosphate concentrations in the soil solution. Phosphate binding followed the Freundlich equation in eight of the samples, the Tempkin equation in one sample and a direct linear relationship in two samples. The Langmuir equation fitted most of the samples that had followed Freundlich equation reasonably well, but did not fit the other samples. This showed that determination of the maximum amount of phosphate that can be bound by the sample (i.e., P saturation) using the Langmuir equation cannot be used for all humid-climate soils of British Columbia. Two alternate direct measurements are proposed to determine the potential risk of phosphate in soils to contaminate water: amount of phosphate released during equilibration with water (native unbound phosphate) and amount of phosphate bound during equilibration with a low (approximately 25 mg P kg-1) phosphate solution (potential for the soil to bind applied P). These results show that sulphate and phosphate binding mechanisms by coastal British Columbia soils are not well understood. The nature of the binding mechanisms needs to be determined to develop and interpret soil analyses for agronomic and environmental purposes. Key words: Sulphate binding, phosphate binding, P saturation, soil solution P

Properties of hydrocarbon- and salt-contaminated flare pit soils in northeastern British Columbia (Canada)

Many contaminated sites in Canada are associated with flare pits generated during past petroleum extraction operations. Flare pits are located adjacent to well sites, compressor stations and batteries and are often subjected to the disposal of wastes from the flaring of gas, liquid hydrocarbons and brine water. This study was conducted to evaluate the physical, chemical, electrical and mineral properties of three flare pit soils as compared to adjacent control soils. Results showed that particle size distribution, pH, total N, cation exchange capacity, exchangeable Mg 2+, and sodium adsorption ratio were similar in soils from flare pits and control sites. Total C, exchangeable Ca 2+, K + and Na +, soluble Ca 2+, Mg 2+, K + and Na + and electrical conductivity were higher in flare pit soils compared to control soils. X-ray diffraction and scanning electron microscopic analyses showed the presence of gypsum [CaSO 4 · 2H 2O], dolomite [CaMg(CO 3) 2], pyrite [FeS 2], jarosite [KFe 3(OH) 6(SO 4) 2], magnesium sulphate, oxides of copper and iron + copper in salt efflorescence observed in flare pit soils. Soils from both flare pits and control sites contained mica, kaolonite and 2:1 expanding clays. The salt-rich materials altered the ionic equilibria in the flare pit soils; K Mg–Ca selectivity coefficients in control soils were higher compared to contaminated soils. The properties of soils (e.g., high electrical conductivity) affected by inputs associated with oil and gas operations might render flare pit soils less conducive to the establishment and growth of common agricultural crops and forest trees.

Soil properties influencing compactability of forest soils in British Columbia

The widespread use of heavy machinery during harvesting and site preparation in timber plantations in British Columbia (BC) has led to concerns that compaction causes a reduction in long-term soil productivity. Impacts of properties such as total C, water content, and texture on compactability of forest soils in BC were assessed. Two compactability indices were used: maximum bulk density (MBD) and susceptibility to compaction (SC) determined by the standard Proctor test. Soil samples were collected from 16 sites throughout BC covering a wide range of biogeoclimatic zones. Soils varied in texture (12 to 87% sand, 9 to 76% silt, and 2 to 53% clay) and organic matter content (18 to 76 g kg-1 total C). A strong negative correlation was observed between MBD and gravimetric water content at which MBD was achieved (WMBD) and between MBD and total C. Similarly, WMBD and total C had strong effects on SC. The estimation of either MBD or SC values was not substantially improved by including texture parameters to the regression equations in addition to the total C. The implication of the relationships observed in this study is that increases in soil organic matter reduce the risk of compactability, which is particularly important for forest soils where compaction is generally not corrected by implements after tree planting. The information is also useful for assessing the extent of compaction on soils affected by machine traffic. Key words: Soil compaction, Susceptibility to compaction, maximum bulk density, Proctor test, total carbon

Control of Verticillium Yellows in Chinese Cabbage by the Dark Septate Endophytic Fungus LtVB3

ABSTRACT Three hundred forty-nine fungal endophytes were obtained from a total of 1,214 root segments of eggplant, melon, barley, and Chinese cabbage grown as bait plants in a mixed soil made up of samples from different forest soils in Alberta and British Columbia, Canada. Three of the 349 isolates, when inoculated in axenically reared Chinese cabbage seedlings grown in petri dishes, almost completely suppressed the effects of a postinoculated and virulent strain of Verticillium longisporum. Two isolates effective against the pathogen were Phialocephala fortinii, which had been obtained from the roots of eggplant and Chinese cabbage. The third isolate was a dark septate endophytic (DSE) fungus obtained from barley roots. Hyphae of P. fortinii grew along the surface of the root and formed microsclerotia on or in the epidermal layer. Hyphae of the DSE fungus heavily colonized root cells of the cortex. Seedlings grown for 1 week in the presence of the endophytes were then challenged with the Verticillium pathogen. In DSE-treated roots, some of cell walls in the epidermal and cortical layers showed cell wall appositions and thickenings, which appeared to limit the ingress of the pathogen into adjacent cells. Such marked host reactions were not observed in the root cells colonized by P. fortinii. Chinese cabbage preinoculated with the above endophytes and, for comparison, a previously reported disease-suppressive fungal endophyte, Heteroconium chaetospira, were transplanted into the field and disease symptoms were assessed. The DSE could most effectively inhibit the development of Verticillium yellows, with reductions in the percentages of external and internal disease symptoms of 84 and 88%, respectively. The protective values against the disease are extremely high compared with those of other isolates. Most of the DSE-treated plants in the plots achieved marketable quality.

Response of forage grass to sulphur applications on coastal British Columbia soils

Little is known about the S requirement of coastal British Columbia soils. Spring gypsum applications increased yield in two and decreased yield in one of six forage grass rate-of-application field trials. Yield effects did not occur at every cut. At the sites where yield depression was observed, the effect primarily occurred at the intermediate rates and S concentration increased with increased rate of application. Luxury uptake of S (increased S concentrations without a yield effect) showed residual effects occurred into the third season after application, despite the abundant winter precipitation common in the area. Yields were affected in a form × rate × time trial, but not at every cut. Powdered elemental S was available to plants sooner than Agri-Sul (an elemental S fertilizer), but neither as quickly as gypsum. Four of five traditional soil test S extractants were significantly correlated with first-cut uptake of S in the control treatment, with the bicarbonate extraction having the highest coefficient (r2= 0.29). The smaller amount of sulphate in calcium chloride compared to the other extractants showed soil adsorption. Soil S tests are required to manage S for optimum yield without accelerated soil acidification. Key words: S fertilizer forms, S rates, gypsum, elemental S fertilizer, Agri-Sul, plant S uptake, soil S tests

Aspen development on similar soils in Minnesota and British Columbia after compaction and forest floor removal

Forest management practices that decrease soil porosity and remove organic matter can reduce site productivity. We evaluated effects of four treatments—merchantable bole harvest (MBH) with three levels of soil compaction (none, light, or heavy), and total woody vegetation harvest plus forest floor removal (FFR)—on fifth-year regeneration and growth of aspen (Populus tremuloides Michx.) growing on soils with similar textures (20–40 cm silt loam over clay loam till) in northern Minnesota (MN) and northeastern British Columbia (BC). Overall mean sucker density was significantly greater in BC than in MN, and mean height was significantly lower. Soil compaction did not affect sucker density in BC, but significantly reduced it in MN, primarily due to late spring treatment. In BC, mean sucker heights generally decreased with level of compaction, but only the differences between non-compacted and the heavy compaction treatments were significant. On the MN plots, sucker heights were reduced significantly by compaction. Treatment responses were similar on both sites: (1) the greatest sucker densities were in the FFR treatment; (2) greatest mean heights were on the non-compacted MBH plots and were significantly greater than those in the FFR treatment; (3) sucker heights generally decreased with level of compaction; and (4) soil compaction decreased the number of suckers that had reached a dbh of 25 mm after five years and will likely delay future stand development and reduce site productivity. Key words: sustainable management, organic matter removal, soil compaction, aspen sucker density, height growth