Shallow Till Research Articles

Changes to soil profile carbon and nutrient distribution following pasture renewal with full inversion tillage

ABSTRACT Full inversion tillage (FIT) at pasture renewal is a management option aiming to increase carbon stocks in long-term pasture, to achieve carbon neutrality. This study investigated the effects of FIT on carbon and nutrient distribution in the soil profile (0–7.5, 7.5–15, 15–22.5 and 22.5–30 cm depths) as well as nutrient uptake, and subsequent fodder crop and/or pasture yields across three pasture renewal trials (Trials 1 and 3: Alfisol; Trial 2: Andisol). These effects of FIT were assessed against standard tillage treatments (no till, shallow till), and non-renewed pasture within 8–18 months post-tillage. FIT changed soil carbon stratification, causing 16%–46% reduction in topsoil (0–7.5 cm) cation exchange capacity across the three trials. However, nutrient levels after FIT remained within recommended ranges for crop and/or pasture growth, avoiding any yield reductions. Topsoil fertility post-FIT depended on original degree of nutrient stratification in the soil profile. At Trial 1, temporary deficiencies caused by low subsoil P and K soil tests pre-FIT were anticipated and corrected with fertiliser nutrients for the following break crop and resown pasture. We conclude that soil testing the cultivation depth prior to FIT at pasture renewal provides the necessary soil test information to manage yield expectations.

Soil carbon storage and mineralization rates are affected by carbon inputs rather than physical disturbance: Evidence from a 47-year tillage experiment

In spite of the large number of studies conducted on the drivers of soil organic carbon (SOC) stocks, there is still no consensus on the impact of tillage on the distribution and turnover rate of SOC in the soil profile. Few studies have characterized precisely the turnover of SOC using 13C natural tracing or simulated the SOC evolution per soil layer. In this study, we combined several approaches (diachronic analysis of SOC stocks, isotopic tracing and modelling) for characterizing the SOC evolution per soil layer in one of the oldest tillage experiments comparing no-till (NT), shallow till (ST) and full inversion tillage (FIT) combined with six crop managements. The new measurements made in 2017 reported in this paper confirm that i) tillage had no effect on SOC stocks integrated over the old ploughed layer (∼0−28 cm) or deeper (∼0−58 cm) and ii) reduced tillage affected the SOC distribution in the soil profile, with SOC storage in the upper layer (∼0−10 cm) offset by a SOC loss in the underlying layer (∼10−28 cm). The change in rotation (from C4 to C3 crops) in two crop management treatments allowed to quantify the decrease in C4 stocks during 19 years and calculate the specific mineralization rates relative to tillage treatments and soil layers. The mineralization rates did not vary significantly between tillage treatments in the whole (old) ploughed layer (∼0−28 cm) but varied according to depth and tillage. The highest rates were found in the layer 0−5 cm of NT or ST and the lowest rates in the layer 10−28 cm of the same tillage treatments. The rates were highly correlated with estimated C inputs and particulate organic matter contents in each layer, but not with tillage intensity. The evolution of total SOC and C4 stocks of each soil layer was simulated with AMG model during 47 years. The standard model (with a single mineralization rate) gave a good prediction of SOC evolution when applied to the whole profile (∼0−28 cm) but not for each individual layer. Including a relationship between C input and mineralization rate in the model allowed to well simulate the SOC evolution in all soil layers. This study shows that the main effect of a change in tillage on SOC storage is the change in the distribution of C input throughout the profile and the corresponding variation of the priming effect rather than the change in physical soil disturbance.

Gold exploration using heavy minerals in till and weathered bedrock in Petäjäselkä, northern Finland

As a part of a gold exploration project in Petäjäselkä, northern Finland, carried out by the Geological Survey of Finland, heavy mineral studies and detailed till geochemical and stratigraphical studies were used for mineral exploration. These studies covered c . 22 km 2 in the Petäjäselkä area. The objective of this research was to find out how heavy minerals and till geochemistry can be used in gold exploration, and how they reflect the glacial dispersion in shallow till areas in Petäjäselkä. Furthermore, an automated mineralogical identification method (SEM-EDS) was tested in the indicator mineral research. Samples from till and underlying, pre-glacially weathered bedrock were collected from the test pits and trenches. A total of 381 heavy mineral and 713 geochemical samples were collected. The heavy mineral samples were concentrated with a spiral concentrator and a Knelson concentrator. The geochemical samples were analysed by ICP-AES and GF-AAS following aqua regia decomposition. The elevated gold contents and distinct anomalies found in till and weathered bedrock indicate the whole study area to have potential for gold mineralization. Based on microscopic and automated mineralogical studies, native gold was the only useful indicator mineral present in the heavy mineral samples for gold exploration in Petäjäselkä.The detailed till geochemical results show that the glacial transport distance in Petäjäselkä is short, only some tens of meters. Differences in the Au-Ag contents of the gold grains were noted between the three gold mineralized targets in Kerolaki, Selkä-Mäntypää and Ranta-Mäntypää. Arsenic, bismuth and tellurium proved to be pathfinder elements for gold mineralization both in till and weathered bedrock. The results of this study show that the heavy mineral studies, together with till geochemical studies, provide a useful method for identifying exploration targets in glaciated terrain. However, different methods of heavy mineral concentration affect the recovery of gold grains and thereby the final results of this study.

Aspects and methods in reconstructing the medieval terrain and deposits in Vilnius

The article deals with the geomorphological diversity (confluence of Neris and Vilnia rivers, junction of two ice ages, erosion hill terrains, terrace levels, etc.) of Vilnius city which played an important role in choosing the place for the city to be established and in formation of its defence structure. The diversity of terrain of Vilnius city and its environs is demonstrated by the distinguished morphogenetic zones: 20 morphogenetic units including 5 zones within the area of the medieval city. From the point of view of the history of environment, the historical relief of Vilnius city has five types of relief. The research was carried out in one of the five types of city topography: moraines left by glaciers (part of the Kuprijoniškės-Salininkai morainic complex). The shallow till acted as an impermeable barrier and created conditions for accumulation of groundwater. Springs emanated at the slope bottom turning into streams. The largest among them is the Vingrė River, which marks the boundary between two types of topography. The studied territory occupies 2.6 km2. Through the reconstruction of the primordial terrain, it would be possible to trace the direction of Vingrė stream and the location of the defensive wall. LIDAR topography and borehole data, topographic maps of 1842 and 1994, and archaeological data were used. Geophysical and digital methods were applied. The research contributes to reconstruction of the pre-anthropogenic terrain, indicating possibilities for its optimal use and living conditions.

Long-term effect of contrasted tillage and crop management on soil carbon dynamics during 41 years

Although numerous studies have been conducted on the effect of tillage on soil organic carbon (SOC), there is still no consensus on the importance of sequestration which can be expected from reduced tillage. Most studies have used a synchronic approach in fields or long-term experiments which were often poorly characterized with respect to initial conditions. In this paper, we used a diachronic approach to quantify SOC changes in a 41 years experiment comparing no-till (NT), shallow till (ST) and full inversion tillage (FIT) combined with crop managements (residues removal, rotation and catch crops). It included SOC measurements at time 0 and every 4 years, calculations at equivalent soil mass within or below the old ploughed layer. Results show that tillage or crop management had no significant effect on SOC stocks after 41 years both in the old ploughed layer (ca. 0–28cm) and deeper (ca. 0–58cm). Tillage had no effect on crop yields and residues. In the reduced tillage treatments (ST and NT), SOC accumulated in the surface layer (0–10cm), reaching a plateau after 24 years but declined continuously in the lower layer (10–28cm) at a rate of 0.42–0.44% yr−1. The difference in SOC stocks (ST or NT minus FIT) over the old ploughed layer followed a non-monotonic pattern over time. Reduced tillage caused a rapid SOC sequestration during the first 4 years which remained more or less constant (mean=2.17 and 1.31tha−1, resp.) during the next 24 years and disappeared after 28 years. The drop was attributed to the higher water balance recorded during years 24–28. In the reduced tillage treatments, the changes in SOC over time were negatively correlated with the water balance, indicating that sequestration rate was positive in dry periods and negative in wet conditions. This study highlights the interest of diachronic approaches to understand the effect of tillage and its interaction with environmental and management factors.

Porphyry Cu indicator minerals in till as an exploration tool: example from the giant Pebble porphyry Cu-Au-Mo deposit, Alaska, USA

ABSTRACT Porphyry Cu indicator minerals are mineral species in clastic sediments that indicate the presence of mineralization and hydrothermal alteration associated with porphyry Cu and associated skarn deposits. Porphyry Cu indicator minerals recovered from shallow till samples near the giant Pebble Cu-Au-Mo porphyry deposit in SW Alaska, USA, include apatite, andradite garnet, Mn-epidote, visible gold, jarosite, pyrite, and cinnabar. Sulphide minerals other than pyrite are absent from till, most likely due to the oxidation of the till. The distribution of till samples with abundant apatite and cinnabar suggest sources other than the Pebble deposit. With three exceptions, all till samples up-ice of the Pebble deposit contain 40grains/10kg) are in close proximity to smaller porphyry and skarn occurrences in the region. The distribution of Mn-epidote closely mimics the distribution of garnet in the till samples and further supports the interpretation that these minerals most likely reflect skarns associated with the porphyry deposits. All but two till samples, including those up-ice from the deposit, contain some gold grains. However, tills immediately west and down-ice of Pebble contain more abundant gold grains, and the overall number of grains decreases in the down-ice direction. Furthermore, all samples in the immediate vicinity of Pebble contain more than 65 % pristine and modified grains compared to mostly re-shaped grains in distal samples. The pristine gold in till reflects short transport distances and/or liberation of gold during in-situ weathering of transported chalcopyrite grains. Jarosite is also abundant (1–2 500 grains/10kg) in samples adjacent to and up to 7 km down-ice from the deposit. Most jarosite grains are rounded and preliminary Ar/Ar dates suggest the jarosite formed prior to glaciation and it implies that a supergene cap existed over Pebble West. Assuming this interpretation is accurate, it suggests a shallow level of erosion of the Pebble deposit by glacial processes. Overall the results of this study indicate that porphyry Cu indicator minerals in till samples may be useful in the exploration for porphyry deposits in SW Alaska.

ON-FARM WHEAT TRIALS IN BANGLADESH: A STUDY TO REDUCE PERCEIVED CONSTRAINTS TO YIELD IN TRADITIONAL WHEAT AREAS AND SOUTHERN LANDS THAT REMAIN FALLOW DURING THE DRY SEASON

This research set out to find ways to increase wheat production in Bangladesh. The approaches were (1) to increase the area planted to wheat, concentrating on developing a suitable management system for the very hot, often saline and hitherto largely untested fallow lands of the south; and (2) to increase economic and sustainable yield of wheat in the traditional rice-wheat zones. Five mechanized reduced tillage and planting systems were compared. They were used to enable 200 co-operating farmers at 11 locations to plant on time and avoid the reduction in yield that accompanies delays, found in this study to average 2 % d−1. Methods that placed seeds in rows were zero tillage, full or strip surface shallow till, and raised beds. A partially mechanized version of the traditional manual system called New Conventional, in which seeds and fertilizers were broadcast, was also tested. Farmers' wheat yields averaged more than 3.5 t ha−1 for the two seasons of the study. Farmers in the untested lands averaged more than 2.5 t ha−1 on their farms, well above the 0.5 t ha−1 needed to cover all costs and equal to normal production levels in traditional wheat areas. Surprisingly, full and strip till did not produce higher yields overall than New Conventional in either season. Reasons for the lack of difference are discussed in relation to other aspects of management and variation between the farmers themselves. Farmers had varying opinions and mixed success with zero till and beds. The economic consequences to farmers of using the different systems are also discussed with the suggestion that the low-tech New Conventional method will be preferable for novice wheat farmers in the historically fallow lands where the study indicated potential production is 1 million tonnes.

Summer Squash Planting Systems Following a Rye Cover Crop

Commercial organic vegetable production requires using soil improvement practices and effective weed control measures. Rye (Secale cereale) cover crops are known to suppress annual weeds. Research was begun in 2004 to measure crop yield, annual weed infestation, and weed control requirements for vegetable planting systems that begin with a rye cover crop. Poultry litter was used to supply nutrients and was applied based on a soil test and commercial vegetable recommendations. Rye `Elbon' was seeded 21 Oct. 2004 on beds with 1.8-m centers. Zucchini squash (Cucurbita pepo) `Revenue' was planted the following year using three crop establishment dates, such that transplanting occurred on 6 May, 3 June, and 29 June. Planting system treatments included: conventional tillage (CT), CT and plastic mulch (P), CT with stale seedbed, mow, mow and burn-down, mow and shallow till (ST), ST and burn-down. Following field preparation, squash was transplanted in a single row at the bed center with 0.77-m plant spacing. Drip irrigation was used in all plantings. Emerging weeds were removed by hoeing. Squash was harvested from each planting over approximately 3 weeks and total marketable fruit counts were determined. Marketable yields with P were approximately double those of the CT and ST treatments in the 6 May transplanting. Yields were comparable for CT and ST in the 3 June transplanting, but were significantly lower for the P treatment. There were no significant differences among the treatments that received tillage in the 29 June planting. However, the non-tilled treatments had significantly lower yields compared to tilled treatments.

Factors influencing windthrow in balsam fir forests: from landscape studies to individual tree studies

Windthrow hazard depends upon the interaction of numerous factors whose relative importance has yet to be assessed in the specific context of Eastern Canadian boreal forests. This paper presents results from three studies looking at their relative importance at different scales in the context of balsam fir stands. First, factors involved in a catastrophic windthrow are examined in order to assess their importance at a regional and local scale. Wind speeds were estimated from a numerical model and overlayed with windthrow, soil and stand maps. The two regions that were damaged presented many predisposing factors: high occurrence of shallow soils, of vulnerable species and of overmature stands. Moreover, both regions have been identified as high wind areas. No consistent effect of wind speed on windthrow could be demonstrated, but the increasing vulnerability of stands with increasing proportion of balsam fir in one region and increasing age in balsam fir stands in both regions was significant. In one region, shallow tills experienced more damage in comparison with deep tills but not in the other. The second study looks at windthrow in riparian buffer strips at a local level. It includes a wind tunnel study and a field monitoring in stands of similar species composition and age. Results have shown that windthrow after 7 years was very variable and did not differ with strip width or thinning in the strip. In fact, it was more closely related to locations exposed to stronger winds stressing the importance of wind exposure estimation. It also confirms the greater vulnerability of balsam fir. The last study addresses the identification of external indicators of mechanical weaknesses on individual trees. It involves dissections and winching of trees with and without defects. Results tend to indicate a reduction in resistance when cracks are present on balsam fir. These three studies provide some information to begin considering windthrow hazard in the management of balsam fir forests.

Water transit times and flow paths from two line injections of3H and36Cl in a microcatchment at Gårdsjön, Sweden

To investigate groundwater transit times and flow paths in shallow till soil, within an acidification study at Gardsjon, Sweden, two line injections of Cl-36 and H-3 Were made in groundwater during ...

Episodic sulphate export from wetlands in acidified headwater catchments: Prediction at the landscape scale

Sulphate (SO4-2) concentrations in 34 intensively measured Canadian Shield streams near the Dorset Research Centre, central Ontario, were used to test a hydrogeologic model that uses simple measures of wetland area and till depth to identify catchments that produce SO4-2 pulses. Mean annual measured maximum SO4-2 concentrations were significantly greater in shallow till ( 1 m depth) containing wetlands or catchments with no wetlands. Average maximum SO4-2 concentrations in wetland catchments during years with dry summers were >20 mg/L in 19 of 20 catchments with average till depths of 1 m. Peaks in mean annual maximum SO4-2 concentrations from wetland catchments with shallow till occurred during summers with rain fall 150–200 mm less than potential evaporation estimates. There were no significant differences in mean average annual SO4-2 concentration among the different catchments during wet summers, with SO4-2 concentrations ranging from 6 to 13 mg/L. These observations suggest that a large portion of the temporal and spatial variation in SO4-2 chemistry and export can be predicted in headwater catchments of the Canadian Shield and perhaps in other landscapes where till depth influences upland-wetland hydrologic connections.

Sulphate Mobilization and Pore Water Chemistry in Relation to Groundwater Hydrology and Summer Drought in two Conifer Swamps on the Canadian Shield

Variations in sulphate (SO42-) concentration of porewater and net SO42- mobilization were related to differences in water level fluctuations during wet and dry summers in two conifer swamps located in catchments which differed in till depth and seasonality of groundwater flow. Sulphate depletion at the surface and in 20 cm porewater coincided with anoxia and occurred mainly during the summer when water levels were near the peat surface and water flow rates were low in both catchments. There was an inverse relationship between net SO42- mobilization and water level elevation relative to the peat surface, explaining variation in SO42- dynamics between the swamps during summer drought periods. Aeration of peat to 40 cm and a large net SO42- mobilization (10–70 mg SO42- m-2 d-1) occurred during a dry summer in which the water level dropped to 60 cm below the surface in the swamp receiving ephemeral groundwater inputs from shallow tills within the catchment. This resulted in high SO42- concentrations in the surface water and porewater (30–50 mg L-1), and elevated SO42- concentrations remained through the fall and winter. In contrast, within the swamp located in the catchment with greater till depth (> 1 m), continuous groundwater inputs maintained surface saturation during the dry summer, and SO42- mobilization and concentrations of SO42- in the pore water during the following fall did not increase. Susceptibility to large water table drawdown and mobilization of accumulated SO42- is influenced by the occurrence of ephemeral vs. continuous groundwater inputs to valley swamps during dry summer periods in the Canadian Shield landscape. This study reveals that extrapolation of results of SO42- cycling from one wetland to another requires knowledge of the hydrogeology of the catchment in which the wetlands are located.

Substrate type and the distribution of sugar maple at its elevational limit in the White Mountains, New Hampshire

The relationships between tree species distribution and substrate characteristics were examined at the upper elevational limit of sugar maple (Acer saccharum Marsh.) in the White Mountain National Forest, New Hampshire. Four tree species were studied: sugar maple, balsam fir (Abies balsamea (L.) Mill.), red spruce (Picea rubens Sarg.), and yellow birch (Betula alleghaniensis Britton). At 51 individual trees (>=2.5 cm diameter at breast height) of each species, "substrate type" was described based on the parent material, soil horizons, depth and texture of the B and C horizons, nature of surface boulders, and the depth to and type of impermeable layer. Substrate type was significantly (p < 0.001) associated with tree species. Sugar maple was relatively more frequent on deep fine and compact tills, less frequent on washed or shallow till, and absent on shallow, organic, or grus (weathered granite) substrates. Red spruce, balsam fir, and yellow birch were less sensitive to substrate type. Red spruce and yellow birch were most frequent on organic material or grus over rock. Balsam fir most frequently occurred on washed till. As the frequency of substrates favorable to sugar maple declined with elevation, it is possible that the upper elevational range limit of this species is influenced by substrate availability.

Relationships between change in fire frequency and mortality due to spruce budworm outbreak in the southeastern Canadian boreal forest

Abstract. We present a simple empirical model that allows an estimation of mortality due to spruce budworm (Choristoneura fumiferana) outbreak in relation to fire frequency and site characteristics. The occurrence of a recent spruce budworm outbreak around Lake Duparquet (48° 30’N, 79° 20’W, ca. 300 m a.s.l.) in northwestern Québec permitted a reconstruction of the stand composition before the outbreak, and also of the mortality of Abies balsamea due to the outbreak. The basal area of A. balsamea increases with time since fire in all site types but with increasing values for (1) rock and shallow till, via (2) till and mesic clay up to (3) hydric clay. Mortality (measured as percentage loss of basal area due to the outbreak) increases with time since fire but did not vary with site type. The increasing abundance of A. balsamea with time since fire is mainly responsible for this increase in mortality. Mortality for a specific basal area is, however, lower for the more recently burned stands suggesting a significant residual effect of time since fire. A landscape model integrating mortality due to the outbreak for stands of different age is developed. Both absolute and relative losses of basal area increased with the length of the fire cycles. According to this model, changes in fire cycle could explain a large portion of the spatio‐temporal variations observed in outbreak mortality in the southeastern boreal forest of Canada.

Migration of landfill leachate into a shallow clayey till in southern New Brunswick: a field and modelling investigation

Migration of landfill leachate into a shallow clayey till in southern New Brunswick: a field and modelling investigation

Height growth of jack pine (Pinushanksiana) in relation to site types in boreal forests of Abitibi, Quebec

A combination of surface deposit and moisture regime class was used to investigate the utility of site type as a predictor of jack pine growth in northwestern Quebec. Height–age curves produced from stem analyses of dominant trees from 96 sample plots produced three jack pine (Pinusbanksiaina Lamb.) productivity classes. The low productivity class includes moderately dry shallow tills, shallow organic deposits over bedrock, and fluvioglacial sands with moisture regime classes moderately dry and fresh. Moderately dry to very moist deep tills and moderately dry to moist clays are classified as having high and very high productivity, respectively. The large difference in height growth between these latter two groups and the low productivity class precluded the definition of a moderate productivity class. The form of the height-growth curves was very similar among site types except for sandy, moderately dry sites, which showed a growth delay at young ages. On dry sites, particularly on well-drained tills, density and basal area were higher than on clay sites. Although volume yield of natural stands on tills and clays would thus be similar, it would likely be spread among a greater number of stems on tills. There was little difference in site index between natural jack pine growing on clays and tills. The low nutrient and moisture requirements and strong taproot of jack pine could explain why soil depth and bulk density are more important than soil richness. Although site type, expressed as a combination of surface deposit and moisture regime class, may be more detailed than needed, it provided an adequate prediction of potential jack pine productivity.

Sulphate mass balances of Precambrian Shield wetlands; the influence of catchment hydrogeology

The sulphate budgets of two valley-bottom conifer swamps, located in headwater catchments with contrasting till depth, typical of the southern Canadian Shield were determined from June 1990 to August 1992. Temporal variations in the retention of SO42− in both swamps were related to the magnitude of upland runoff and water level in the wetlands. Contrasts in catchment till depth and nature of groundwater flow resulted in differences in SO42− retention between years and swamps. Transient groundwater inputs entering the swamp in the thin-till catchment resulted in a large water-table drawdown during dry summers, export of SO42− the following fall, and low annual SO42− retention. Continuous discharge of groundwater into the swamp in the moderate-till catchment maintained saturated surfaces and efficient SO42− retention during both years with dry and wet summers. Greater SO42− retention in this swamp may also be contributed by the greater interaction of groundwater, rich in SO42−, with deeper peat. Data from these two sites indicate that within the shallow till – rock ridge physiographic region of the Canadian Shield, small variations in catchment till depth can result in a large range in temporal and spatial variations in SO42− retention in valley wetlands.

Weed Management in Peanut Using Stale Seedbed Techniques

Field studies were conducted from 1991 through 1993 to determine the effects of stale seedbed management practices on weed control in peanut. Main plots were four levels of stale seedbed management: deep till (23 cm) and plant the same day (standard system), deep till 6 wk early and shallow till (7.6 cm) at 2 wk intervals prior to planting, deep till 6 wk early and application of glyphosate (1.1 kg ai ha−1) 1 wk prior to planting, and deep till 6 wk early without additional treatment prior to planting. Sub-plots were three levels of weed management following peanut planting; intensive, basic, and cultivation alone. Stale seedbed management practices stimulated weed emergence when followed by other control measures prior to planting. Populations of Florida beggarweed, Texas panicum, and yellow nutsedge were lower when stale seedbeds were shallow tilled at 2 wk intervals prior to planting, resulting in greater peanut yields. Weeds on nontreated stale seedbeds were difficult to control once peanut was planted and reduced yields. Stale seedbed management practices generally had no effect on the quantity of foreign material contaminants originating from weeds, soil, or peanut plant in harvested peanut. These results indicate that shallow tillage on stale seedbeds can reduce weed populations prior to planting and increase peanut yields.

Soil management and termite damage to maize(Zea maysL.) in a semi‐arid tropical alfisol†

Abstract Termite damage to maize (Zea mays L.) was studied in relation to soil management practices in an alfisol. Microtermes obesi Holmgren and Odontotermes obesus (Rambur) together damaged 11 ‐16% of plants across the soil management treatments. The damage caused by M. obesi was greater (9–14% of plants) than that of O. obesus (1–2% of plants). A higher number of plants were damaged in shallow and deep till plots whereas the number was low in plots with zero tillage, and prior perennial cover of pigeonpea, Stylosanthes hamata (L.) Taubert and both in combination. However, the soil management treatments did not show any significant effect on the percentage of termite‐damaged plants. Termite damage was noticed towards the end of the crop season, and gradually intensified as the plants senesced.

Ecological factors affecting abundance of advanced growth in jack pine (Pinus banksiana Lamb.) stands of the boreal forest of northwestern Quebec

Natural regeneration in jack pine (Pinus banksiana Lamb.) stands in Quebec is only sufficient 4% of the time and up to only 33% of the time in mixed stands. This study evaluates the usefulness of forest ecological types as defined by the Quebec Ministry of Forests in predicting abundance of advanced growth in pure and mixed jack pine stands of the Abitibi region, in north-western Quebec. Trees above 1.3 m in height and up to 5 cm DBH were tallied in 102 quadrats of 20 × 20 metres to evaluate advanced growth densities. No significant difference in advanced growth densities was observed between the two main types of surficial geological deposit in the region, lacustrine clays and glacial tills. Only shallow till and organic deposits over bedrock and fluvio-glacial sands showed significantly higher advanced growth densities. Prediction can be improved by using ecological variables such as soil texture, moisture regime, distance from a seed source and stand composition. Abundance of black spruce (Picea mariana (Mill.) B.S.P.) regeneration is positively associated with the proportion of sand in the soil profile and with drier sites; advanced growth of balsam fir (Abies balsamea (L.) Mill.) and white spruce (Picea glauca (Moench) Voss.) is weakly associated with the distance to a fire-preserved zone containing seed trees. Abundance of pin cherry (Prunus pensylvanica L.f.), probably associated with canopy openings, is positively linked with abundance of balsam fir and white spruce advanced growth. Jack pine regeneration by means of advanced growth occurs almost exclusively in jack pine stands on sand; higher proportions of hardwoods in the overstory appear to be negatively linked to jack pine advanced growth. Although the site variables studied showed some significant relationships with advanced growth abundance (maximum R2 = 0.32) which were slightly improved with stand composition variables (maximum R2 = 0.38), no satisfactory predictive model could be implemented. Key words: jack pine, advanced growth, ecological classification