Joann K. Whalen

McGill University | McGill · Department of Natural Resource Sciences

Earthworms are abundant invertebrates in agricultural soils that have a myriad of well-documented effects on soil functions and plant production. Earthworm activities are linked to changes in hydrological flows and accelerated biogeochemical cycling, which readily connects earthworms to the buffering and regulatory processes at an ecosystem level....

Forest soils often contain more carbon (C) than living trees, with significant variation in soil organic carbon (SOC) stocks due to stand type and soil characteristics. This study evaluates SOC stocks in the Moroccan Middle Atlas forests using field measurements and machine learning models. Soil profiles across 16 forest types were analysed, identi...

In addition to supporting plant productivity and nutrient cycling, arbuscular mycorrhizal (AM) fungi contribute to multiple functions within terrestrial ecosystems. However, as ecosystems face increasing temperatures and changes in precipitation, these factors may affect how AM fungi interact with ecosystem multifunctionality. Here, we investigated...

Cyanobacteria proliferate in warm, nutrient-rich environments and release toxic secondary metabolites (e.g., cyanotoxins, anabaenopeptins, etc.) into natural waters. Using the toxic secondary metabolites -contaminated water to irrigate crops could expose humans and biota to cyanotoxins, but the risk may be low if agricultural soils can sorb and ret...

This chapter describes the inherent elemental composition and physico-chemical properties that affect the biochar nutrient content (environmental reactions that alter the nutrient supply from biochar, such as leaching and biological reactions in soil-plant systems, are explained in Chapters 12, 13, and 16). Here, the focus is on how feedstocks and...

Biodiversity can enhance soil multifunctionality through strengthening biotic interactions in soil food webs, but largely unknown in agroecosystems. We therefore predicted that vermicompost, serving as an organic amendment and soil health conditioner, could enhance trophic interactions among bacteria, fungi and nematodes and mediate synergies and t...

Silver nanoparticles (AgNPs) are present in biosolids from wastewater treatment facilities, a common soil amendment. Exposing earthworms (Eisenia fetida) to AgNP and AgNO3 in soil with 0 and 7.5 g biosolids kg⁻¹ for 28 days showed AgNO3 was more lethal to earthworms in artificial soil (LC20 ≤ 325 mg Ag kg⁻¹) than natural soil (LC20 ≥ 573 mg Ag kg⁻¹...

Animals are expected to choose foods that optimize their growth, reproduction and survival, but it remains unclear how environmental stressors modulate their dietary preference. Here, we provide the first report of nematode stress resulting from exposure to earthworm-produced cyclic peptides, and confirm that this stress changed the dietary choice...

Subsurface tile drains under agricultural field crops are a major source of phosphorus (P) discharge to aquatic ecosystems, contributing to the eutrophication of surface waters. Adsorption reactors for P removal from drainage water (P‐reactors) could reduce P outflow from agricultural land but were rarely studied in cold, temperate climates. In our...

Municipal biosolids are a nitrogen (N)-rich agricultural fertilizer which may emit nitrous oxide (N2O) after rainfall events. Due to sparse empirical data, there is a lack of biosolids-specific N2O emission factors to determine how land-applied biosolids contribute to the national greenhouse gas inventory. This study estimated N2O emissions from bi...

Biobased residues are local and cost‐effective sources of soil amendments, that can efficiently provide nutrients to crops, enhance soil health, and serve as alternatives to mineral fertilizers. The objective of our study was to comprehensively evaluate soil health and crop productivity of temperate agroecosystems amended with different types of or...

Subsurface tile drains under agricultural field crops are a major source of phosphorus (P) discharge to aquatic ecosystems, contributing to the eutrophication of surface waters. Adsorption reactors for P removal from drainage water (P-reactors) could effectively reduce P outflow from agricultural land but were rarely studied in cold, temperate clim...

Soil with persistent macroaggregates should maintain its integrity following wetting disturbance. This study determined how wetting-drying cycles affect two pre-sieved macroaggregate size fractions (2–4 mm and 0.6–2 mm) of clay and organic soils pretreated with organic carbon substrates. Soil aggregates were unamended or treated with organic carbon...

Sodium-rich water may deteriorate calcite-stabilize soil. The objective of this work was to determine whether calcite solution prepared with sodium-rich water were capable of forming stable soil macroaggregates. Calcite solutions were 2.6 g Ca2+ L-1 of CaCO3 mixed with water containing 2.6, 5 or 10 g Na+ L-1 from NaCl. Arid desert soil (5 cm layer,...

Plant roots exude nitrogen (N)-containing compounds, which are assimilated by the rhizobiome to maintain stoichiometric homeostasis. Various 15N-tracing methods exist to estimate the rhizobiome-N derived from root exudation but have never been validated with a full factorial experiment. We exposed ryegrass (Lolium multiflorum) to 15N solutions thro...

Nematodes are a crucial component of rhizosphere biodiversity, affecting plant health as the most abundant and functionally diverse soil animals. Plant-parasitic nematodes are generally considered harmful, which may overlook their potential benefits to plants when coexisting with free-living nematodes in soil. We provide new insights into nematodes...

Drought events are increasingly affecting the planet’s biodiversity. While shrinking body size in response to drought has been observed in many vertebrate animals, whether this rule applies to microscopic animals and the mechanisms during this process remains largely unknown. To address this knowledge gap, we conducted a regional-scale investigatio...

Biobased residues derived from organic urban waste materials can be processed to produce soil amendments that enhance soil fertility and carbon sequestration. However, the extent of carbon sequestration by biobased residues depends on the interaction between their physicochemical properties, climate, and agroecosystem management practices. Our obje...

Soil multifunctionality is the consequence of biotic interactions that drive decomposition, nutrient cycling and net primary production. Energy flux describes the energy consumed and transferred among multitrophic groups in the soil food web, which are logically linked to multifunctionality. In a subtropical agroecosystem with an annual sweet potat...

No-tillage agriculture and agroforestry have many environmental benefits, such as maintaining soil productivity, storing water and reducing labor and energy. These practices may also reduce soil erosion in hilly landscapes with a Mediterranean climate by leaving more crop residues on the surface that allow rain and irrigation water to infiltrate th...

Cyanobacteria proliferate in warm, nutrient-rich environments, and release cyanotoxins into natural waters. If cyanotoxin-contaminated water is used to irrigate agricultural crops, this could expose humans and other biota to cyanotoxins. However, cyanotoxins may be degraded by the diverse microbial consortia, be adsorbed or otherwise dissipate in a...

Aggregate stability, an indicator of soil structural resistance to mechanical forces, depends upon the strength of binding substances within the aggregate. Adhesion of calcium (Ca 2+) oxide-based compounds to soil primary particles is expected to create stable aggregates. This occurs because Ca 2+ will flocculate clay and silicate minerals, and pre...

Human and ecological health depends on the vitality of freshwater systems, but these are increasingly threatened by cyanotoxins released from harmful algal blooms (HABs). Periodic cyanotoxin production, although undesirable, may be tolerable when there is enough time for cyanotoxins to degrade and dissipate in the environment, but the year-round pr...

Maize roots vary their growth in response to nitrate ( NO 3 - ) concentration in the environment, but growth plasticity differs among root types. We assessed the morphological response of lateral and axial roots on the primary, seminal, and crown root types exposed to 0, 1, 2, 3.9, and 7.8 mmol L⁻¹ NO 3 - . Higher NO 3 - concentration did not chang...

Roots assemble a diverse community of soil microorganisms in their rhizosphere, the biologically active microenvironment that exists between the root surface and the bulk soil. Roots and their rhizobiome, which include root-associated and endophytic microorganisms, produce and respond to chemical signals. This cross-talk involves the exchange of hu...

Tile drainage is installed in agricultural fields to remove excess soil moisture to allow earlier planting of spring crops. Water moving from soil into tile drainage lines will potentially create a moist environment for earthworms. This study investigated how earthworms were distributed around tile lines, and how their abundance was affected by moi...

Commercial growers who wish to apply biochar to their field crops will need to use conventional agricultural machinery to amend large field areas. Biochar produced by fast pyrolysis of hardwood was applied at a target rate of 5.6 t ha-1 to a single swath (10 m x 100 m) in an agricultural field in Quebec, Canada, using a commercial lime spreader. Wi...

Municipal wastewater biosolids are nutrient-rich residuals with potential as crop fertilizer, if their alkalinity does not adversely affect soil biochemical processes. This study assessed the potential soil enzyme activity after three annual applications of biosolids in a conventionally tilled field under silage corn (Zea mays L.). Biosolids were m...

Soils change naturally as the parent material and minerals are progressively weathered, and in response to the growth of plants, animals and microorganisms across landscapes. In the past century, human-induced changes to the global climate and land use have put soils at risk of degradation. Erosion of fertile topsoil, loss of soil organic matter, e...

Earthworms stimulate organic nitrogen (N) mineralization and this is linked to plant N uptake and N loss from soil. Earthworms may also simultaneously transfer N-rich residues into physically protected soil fractions and temporarily increase N stabilization. This study evaluated soil N transformations and lettuce N uptake in soil microcosms amended...

Purpose Determination of phosphorus (P) species in soils and potential risk of P loss under different P fertilization regimes is of agronomic and environmental importance. However, knowledge on P speciation and potential P loss in the soils with periodic P fertilization is limited. This study evaluated P speciation and potential risk of P loss in s...

Microorganisms are centrally important to the soil organic carbon (C) cycle as decomposers that also contribute to long term C sequestration through physical stabilization and de novo production of soil organic matter (SOM). Bacterial secretions adhere to soil particles and colloidal materials, and these organo-minerals agglomerate into macroaggreg...

In temperate cold regions, the gradual resurgence of soil microbial activity during spring freeze-thaw events is frequently associated with greenhouse gas emissions. Enhanced greenhouse gas fluxes during spring freeze-thaw are related to the mineralization of bioavailable substrates, which may be elevated when soil is amended with organic residues...

Soybean responds to heat and water deficit by producing ethylene, which in high concentrations reduces plant biomass. One way for soybean to tolerate stress is to associate with rhizobacteria that lower the ethylene concentration by hydrolyzing the molecular precursor with the extracellular enzyme 1-aminocyclopropane-1-carboxylate deaminase (ACC de...

Background Urea is the most common nitrogen fertilizer applied to agricultural lands, and it is often treated with urease inhibitors to prevent loss of ammonia during urea hydrolysis. However, urease inhibitors like N‐(n‐butyl) thiophosphoric triamide (NBPT) are susceptible to degradation in soil. Aims This study tested dimethyl sulfoxide, ethylen...

Conceived and co-ordinated by Junwei Luan, Shirong Liu, Andreas Schindlbacher, Cindy Prescott, Alexia Stokes, and Joann Whalen. This Virtual Special Issue aims to bring together studies that provide mechanistic and quantitative knowledge and perspectives on plant and soil interactions, related to soil organic carbon and nutrient cycling in forest...

Municipal wastewater sludge may be processed into biosolids and applied to farmland for crop production, rather than be disposed of in landfills. Biosolids supply plant nutrients and increase soil organic carbon but also contribute to the production of greenhouse gases (GHGs). Computational models must therefore be refined to estimate the contribut...

Maize roots are colonized by arbuscular mycorrhizal fungi, but less mycorrhizal symbiosis is expected as the plant‐available phosphorus (P) concentration of soil increases, based on greenhouse and growth bench experiments. The objective of this study was to evaluate maize root colonization by arbuscular mycorrhizal fungi in a sandy loam soil with a...

• Soil C is the largest C pool in forest ecosystems that contributes to C sequestration and mitigates climate change. Tree diversity enhances forest productivity, so diversifying the tree species composition, notably in managed forests, could increase the quantity of organic matter being transferred to soils and alter other soil properties relevant...

Phosphorus (P) fertilizer should be applied in a way that avoids P accumulation in the topsoil, to limit P losses in surface runoff and leaching through the soil profile. This study compared two P fertilizer regimes (annual application vs. periodic application, once every six years) for their impact on soil P chemistry, P sorption capacity and wate...

Most horticultural crops are planted in soil, although modern cultivation techniques include other media, such as peat-based soil, compost, and inert substrates such as rockwool. A suitable growing media must provide anchorage and stability for the plant roots, considering the diverse life histories of horticultural crops. For example, plants that...

Field-grown horticultural crops are rooted in the soil, a layer of fragmented rocks and decomposing organic matter that provides the physical support as well as most of the water and essential nutrients for crop growth. The soil’s ability to buffer chemical reactions controls the supply of nutrients to crops and binds inorganic salts, trace metals...

Soil organic phosphorus (Po) that is hydrolyzed by phosphatases into inorganic phosphate is a source of phosphorus (P) for agricultural crops. However, the hydrolysis of Po compounds is contingent on their chemical form and stabilization in the soil matrix. We quantified three hydrolyzable Po pools (simple phosphomonoesters, phospholipids, and nucl...

Macroaggregates that dissipate external forces by resisting to disintegration and deformation should persist when subjected to slaking forces when wetted. Accordingly, soil with persistent macroaggregates should maintain its integrity following wetting disturbance. This study determined how repeated wetting affects two pre-sieved macroaggregate siz...

Aggregate stability, an indicator of soil structural resistance to mechanical force, depends upon the strength of binding substances within the aggregate. Adhesion of calcium (Ca)-based compounds to soil primary particles is expected to create stable aggregates. This occurs because Ca 2+ will flocculate with clay and silicate minerals, and precipit...

Microcystins produced by toxic cyanobacterial blooms are a growing threat to water quality because microcystin-contaminated water is unsafe for human consumption and other activities. To protect public health, various physicochemical...

Key points • Root exudates are the medium by which plants communicate with the soil microbiome. • Plant physiology determines the inherent composition of root exudates, which is then modulated by abiotic and biotic factors. • Root exudates allow plants to sense their soil environment and adapt their root architecture accordingly. • Root exudates ca...

Root mucilage is a sticky polymer that is secreted through root border cells. Primarily composed of polysaccharides, with some protein and lipid components, mucilage causes soil particles to adhere to the roots, creating the characteristic rhizosheath that is visible around many plant root systems. The mucilage layer retains water, which is importa...