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With a growing body of research dedicated to understanding earthworm seed preferences, we conducted a preliminary investigation of two previously unconsidered factors: seed density and previous earthworm egestion. We used no-choice feeding experiments with the common European earthworm Lumbricus terrestris L. and seed of the biennial forb Alliaria petiolata (M. Bieb) Cavara & Grande. Earthworm seed ingestion increased exponentially when available seed density was doubled (+305%) and was reduced when encountering seed that had previously been egested by another earthworm (−30%). Impacts of seed density and previous earthworm egestion have broader ecological implications for earthworm granivory behaviour and earthworm-plant interactions in natural and managed ecosystems. We recommend both factors as promising candidates for future experimentation.

There has been minimal study of how ecosystem engineering anecic earthworms such as Lumbricus terrestris L. may influence the distribution of mulch amendments across the soil surface by collecting residues into middens. The two primary research objectives of this study were: (1) to determine how rapidly earthworms change the surface distribution of mulch following amendment, and (2) to produce a more spatially explicit map of earthworm aggregation of mulch. This study used a microcosm experiment to assess the immediate, short-term impacts of earthworms on recently added mulch at a small scale, and an opportunistic field study of the longer-term impacts of earthworms on the distribution of corn ‘stubble’ mulch in a former agricultural field. In the microcosm experiment, earthworms rapidly redistributed mulch within the first week post amendment, decreasing initial ground cover (15-29% decrease). Over the subsequent five weeks, initial cover continued to decrease (20-45% decrease) as mulch was spread thinly onto adjacent, initially bare soil (49-69% increase). Higher mulch amendment mitigated losses in initial cover. In the field study, earthworms aggregated mulch across the soil surface, collecting 40% of the woody corn residues into 17% of the total area in regularly distributed middens. These results demonstrate the potential for L. terrestris to alter the distribution of mulch rapidly in the first several days and weeks following application and in the longer term over several years, increasing the spatial heterogeneity of soil resources. This physical redistribution has only been minimally investigated and may help inform models of earthworm impacts on various ecological processes and improve soil amendment and residue management in earthworm-occupied soils.

Transport by earthworms contributes to the secondary dispersal of seeds and influences patterns of plant community structure and function. To date, however, research on earthworm seed dispersal has focused primarily on vertical transport and the collection of seeds into middens at the soil surface, with no efforts to map horizontal distribution after burial. This study used an emergence depth assay and depth-stratified seedling emergence from soil microcosm cross-sections to map earthworm seed transport in three dimensions using commercial grass seed and the anecic earthworm Lumbricus terrestris L. While specific seed burial profiles should not be considered representative of burial under field conditions (due primarily to high earthworm densities under artificially limiting microcosm conditions), we created what we believe to be the first three-dimensional and most detailed map of earthworm seed burial, visualizing and quantifying the ability of L. terrestris to redistribute seed both vertically and horizontally throughout the soil profile. L. terrestris buried 6.5 to 17.4% of the total seeds and reduced aboveground grass biomass by 59–65 %. Vertically, L. terrestris buried seeds evenly across the 13 cm deep microcosms. Horizontally, L. terrestris aggregated seeds into small clusters aligned obliquely across soil depths, which suggest seeds being deposited in burrow walls (variance to mean ratio: 3.39 ± 2.49). Seeds were aggregated regardless of L. terrestris density but covered a greater cross-sectional area of the soil profile when more earthworms were present. Spatial patterning of shallow buried seed still capable of emergence is a newly described mechanism by which L. terrestris might influence the spatial structure of plant communities.

Wood ash is produced by burning wood residues for energy and is often landfilled but can be more sustainably used as a forest soil amendment. We investigated how different fly and bottom wood ashes applied at a moderate 10 Mg∙ha−1 (dry) affected earthworms, a key group of forest soil biota. We conducted a field experiment with different wood ashes and application timings to determine the effects on population densities of different earthworm functional groups three weeks and one year post-amendment. We also used three laboratory microcosm experiments focused on the geographically widespread and ecologically influential anecic earthworm Lumbricus terrestris to test how wood ashes affect acute survivorship as well as habitat avoidance and surface feeding behaviors. In the field, wood ash amendment generally decreased or had no impact on earthworm densities in the first three weeks following amendment (with density decreases up to − 52 m−2), but had neutral or minor positive impacts one year later (up to + 21 m−2). In the laboratory, wood ashes generally had no effects on short-term earthworm survivorship or growth, but earthworms did respond behaviorally to certain wood ashes by habitat avoidance and reduced surface activity, with decreases in the overall frequency of aboveground events (−63%), the individual duration of each event (−63%), and the percentage of events that involved contact with litter (−53%). Across all experiments, fly ash tended to have a stronger effect than bottom ash. Overall, our study suggests that while some wood ashes may have limited short-term impacts on earthworm abundances, they may cause more subtle but ecologically important behavioral changes. Additionally, these earthworm-wood ash interactions are likely influenced by highly scenario-specific circumstances, including wood ash type, application site, and timing of application.

Summary Earthworm-seed interactions are increasingly recognized as ecologically important. Efforts to study these interactions make use of either no-choice or choice feeding trials due to logistical constraints or differing objectives, however, evidence is lacking regarding the consistency of feeding preferences by earthworms between these scenarios. We conducted a small-scale study in which we compared ingestion and egestion of eleven seed species by the anecic earthworm Lumbricus terrestris L. between no-choice and choice feeding dish trials. We found that seed ingestion and egestion differed between species and the seed ingestion preferences were relatively consistent (Pearson Correlation, r = 0.695) between the feeding trials. These results indicate that seeds preferred in isolation are similarly detectable and preferred alongside other options, aiding in the interpretation of results of other anecic earthworm-seed feeding experiments and suggesting that L. terrestris has a surprisingly strong ability to discriminate between and selectively consume specific seeds from a larger and diverse pool of species options.

Plant communities are often seed-limited, and while rodents and birds are considered to be the primary contributors to surface seed removal, there is growing appreciation for the role of soil invertebrates, including earthworms. There have been very few studies assessing the relative importance of earthworms as granivores under field conditions compared to other taxa. We conducted a small-scale experiment in which we used earthworm inoculations and field exclosures to control access to surface-sown grass seed in an open field habitat and monitored impacts on initial grass recruitment. In isolation, earthworms reduced grass recruitment under field conditions (−22% biomass), but their impact was smaller than the reductions that occurred irrespective of earthworm presence when aboveground taxa had access to plots (−80–83%). The results of this small-scale study suggest that although earthworm-seed interactions may be ecologically important overall, in some habitats other taxa may be more influential than earthworms in terms of total surface seed removal.

The treatment of municipal wastewater can be problematic in the remote cold climate environment of the Canadian Arctic, because of a variety of operational, financial, and technical and bureaucratic reasons. As a result, treatment facilities for many communities are thought to only achieve preliminary to primary treatment of municipal wastewater; wastewater often being discharged directly onto the tundra. In this study we provide the first season long study of tundra wetland systems in the Canadian Arctic. In 2008, we studied the performance of six wetland systems used for wastewater treatment in the Kivalliq Region of Nunavut, Canada. The wetland systems studied services communities of approximately 320–2300 residents, including commercial and government buildings, but generally minimal industry. In total, the systems receive a flow rate of approximately 28–163 m 3 /day of wastewater. We observed average weekly percent reduction in all parameters, with deviations immediately after snow-melt and at the beginning of freeze-up. For the six parameters monitored we observed reductions of 47–94% cBOD 5 , 57–96% COD, 39–98% TSS, >99% TC, >99% E. coli , 84–99% NH 3 -N and 80–99% TP. In three of the systems, the water discharged from the wetlands and into the receiving environment maintained similar concentrations, and significant similarities in NH 3 -N and TP as observed in the natural background concentrations of nearby wetlands. The performance of tundra wetlands to treat the wastewater demonstrates that they are an appropriate technology for remote Canadian Arctic communities. This study also exemplifies the ability of natural systems to act as sinks and transformers, acknowledging that mechanistic assessments will be required to identify primary processes involved in the treatment of Arctic wastewater.

Invasive species have received considerable attention in recent years, but research has primarily focused on invasive species of natural habitats. Furthermore, cropland weeds have often been viewed as possessing a “general-purpose genotype” and therefore exhibiting relatively static genetics. However, a more current view is that weeds are capable of rapid genetic change, thereby making analysis of their evolutionary ecology a potentially valuable component for the development of sustainable weed management systems. In particular, further analysis of ongoing evolutionary change in cropland weeds is important because (1) most cropland weed species exhibit considerable adaptability, (2) cropland agriculture is continuously changing, and (3) further research on weed adaptability is needed to design cropping systems to address evolutionary change. In this review, we examine the potential of cropland weeds to evolve so as to affect their invasiveness. There is abundant evidence of genetic variation within and among weed populations in traits relevant to invasiveness, including seed germination patterns, life history traits, physiological adaptability and adaptation to disturbance and resource fluctuations. Approximately half of cropland weed species are primarily selfing, and species with a high degree of selfing tend to exhibit homogeneity within populations but divergence among populations. We identified four critical areas for future research: conflicting selection pressures on weeds in agroecosystems, feed-back driven dynamics of human-weed co-evolution, co-evolutionary mechanisms of weed adaptation in conjunction with other weed species or organisms, and the role of weed evolution in the restoration of agroecosystems.

Energy used (GJ) per tonne of crop produced defines energy efficiency. Low energy use/tonne of crop produced indicates higher energy efficiency. Because of improved crop breeding (more stress tolerance, genetic gain) crop yields have increased. Concurrently, energy used has decreased. Based on an analysis of energy use/crop produced for Ontario's major row crops (corn and soybean), energy efficiency of crop production increased from 1975 to 1991. In corn, energy efficiency increased 49.8% from 87.95 l of diesel fuel equivalent (LDFE)/t of crop produced to 44.16 LDFE/t from 1975 to 1991. Total corn production (t) and yield (t/ha) increased by 60.0% and 20.1%, respectively, whereas energy use/ha (LDFE/ha) and total energy use (LDFE) decreased by 39.7% and 19.7%, respectively. For soybean, energy use/ha (LDFE/ha) decreased by 46.3% but total energy use (LDFE) increased by 93.8%. The increase in total energy use was caused by a 260.8% increase in soybean acreage (ha). Because the increase in soybean production (t) of 278.2% was much greater than the increase in total energy use (LDFE), energy efficiency increased 48.7% from 75.46 LDFE/t to 38.67 LDFE/t. The proportion that fertilizer manufacturing contributes to total annual energy use in corn decreased slightly (74.2–71.0%) between 1975 and 1991; however, energy use in fertilizer manufacturing declined by 42.4% because of the increased efficiency of manufacturing nitrogen fertilizers. Increased efficiency of fertilizer application also decreased energy use, although application is a much smaller proportion of the total energy use budget. Similar decreases occurred in soybean production. Our analysis of no-till systems using various herbicides and application rates indicated that the systems using the highest herbicide application rates required the least energy, because decreased herbicide application rates may require increased cultivation. This, however, depends on the timing (pre-plant, planting, post-emergent) and type (banded, broadcast) of application and is true only for newer herbicides with low application rates.