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Article 09/09/2024

Soil carbon in the boreal region under climate and land use change

Vallotton, JD, Unc A. 2024. Soil Use and Management, 40, e13108. https://doi.org/10.1111/sum.13108

Abstract

Carbon cycling in boreal regions is controlled naturally by fire disturbance, climate, hydrology, snowmelt, soil heterogeneity, acidity, low nitrogen and phosphorus availability, mycorrhizal distribution, plant cover, and cryoturbation/permafrost at the northern edge. It is primarily altered by human management via and following land clearance. Each factor interacts with others in complex ways, creating a system characterized by high carbon storage and shaped by natural and anthropogenic disturbance. This paper examines boreal research to answer the question: ‘what are the primary factors controlling boreal carbon cycling?’ Though climate change threatens boreal systems, they may yet be resilient given many natural feedback loops that resist massive carbon loss. Perhaps the greatest danger is land conversion, which causes permanent losses and drastic alteration of certain carbon pools. Accordingly, it might be argued that it would be overall better to implement policies that keep these lands as forests, including managed forests, rather than convert to agriculture. Conversely, farming of marginal boreal soils might be managed to enhance carbon storage while satisfying local food security needs. However, the impact of agriculture on soil carbon storage is yet to be effectively quantified and initial results offer inconsistent assessments, reflected in the as-yet natural sciences data-scarce policy development. Research targeting long-term carbon cycling, land conversion practices, agroforestry, and communication between boreal scientists and other groups (climate scientists, policymakers, public, and farmers) must be addressed through creation of long-term experiments.

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Article 17/06/2024

Socio-ecological dynamics of diverse global permafrost-agroecosystems under environmental change

Melissa Ward Jones, Joachim Otto Habeck, Mathias Ulrich, Susan Crate, Glenna Gannon, Tobias Schwoerer, Benjamin Jones, Mikhail Kanevskiy, Prashant Baral, Amina Maharjan, Jakob Steiner, Andrew Spring, Mindy Jewell Price, David Bysouth, Bruce C. Forbes, Mariana Verdonen, Timo Kumpula, Jens Strauss, Torben Windirsch, Christopher Poeplau, Yuri Shur, Benjamin Gaglioti Nicholas Parlato, Fulu Tao, Merritt Turetsky, Stephanie Grand, Adrian Unc, and Nils Borchard. 2024. Arctic, Antarctic, and Alpine Research, 56(1). https://doi.org/10.1080/15230430.2024.2356067

ABSTRACT

Permafrost-agroecosystems include all cultivation and pastoral activities in areas underlain by permafrost. These systems support local livelihoods and food production and are rarely considered in global agricultural studies but may become more relevant as climate change is increasing opportunities for food production in high latitude and mountainous areas. The exact locations and amount of agricultural production in areas containing permafrost are currently unknown, therefore we provide an overview of countries where both permafrost and agricultural activities are present. We highlight the socioecological diversity and complexities of permafrost-agroecosystems through seven case studies: (1) crop cultivation in Alaska, USA; (2) Indigenous food systems and crop cultivation in the Northwest Territories, Canada; (3) horse and cattle husbandry and Indigenous hay production in the Sakha Republic, Russia; (4) mobile pastoralism and husbandry in Mongolia; (5) yak pastoralism in the Central Himalaya, Nepal; (6) berry picking and reindeer herding in northern Fennoscandia; and (7) reindeer herding in northwest Russia. We discuss regional knowledge gaps associated with permafrost and make recommendations to policy makers and land users for adapting to changing permafrost environments. A better understanding of permafrost-agroecosystems is needed to help sustainably manage and develop these systems considering rapidly changing climate, environments, economies, and industries.

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Article 12/03/2024

Corrigendum to “A review of nematodes as biological indicators of sustainable functioning for northern soils undergoing land-use conversion” [Appl. Soil Ecol. 195 (2023) 104762]

Young EH, Unc A. 2024. Applied Soil Ecology, Pages 105208, Volume 195, March 2024, 105208 https://doi.org/10.1016/j.apsoil.2023.105208

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Article 01/11/2023

The rate dependent efficacy of biochar for crop yield and nutrition on Podzols newly converted from boreal forests

Abedin J, Unc A, 2023. Field Crops Research, 303: 109121

Context

Under climate change and local and global food security pressures conversion to agricultural lands on Podzols developed under boreal forests is accelerating across the global north. After conversion Podzols, acid and sandy, are infertile requiring significant management to allow economic production. Biochar, while less useful on fertile soils, may accelerate fertility gains on such marginal lands; it is already considered or land-applied by local farmers, under minimal guidance.

Objective

A multi-year experiment assessed the utility of single or split application of biochar (BC), and of BC doses, for beet yields and nutrient uptake on newly converted Podzols. Time and rate-dependent progression of yields, macro- and micro-nutrients uptake, all parameters identified of interest by northern farmers, were evaluated.

Methods

Kiln-derived hardwood biochar was added at 0, 10, 20, 40 or 80 Mg BC-C ha−1 (BC0 to 80) either as single or as double application. Beet yields and elemental compositions were assessed over 4 years after biochar application. Work was done on a private farm in Labrador, Canada, under a scenario relevant to the boreal north.

Results

BC0 could not sustain significant crop growth, suggesting that post-conversion mineralization of residual soil organic matter cannot support plant growth. In the first one to three years after application of biochar yields increased above the control, but statistically independent of application rates. A statistically significant positive biochar-rate to yield dependency was verifiable only in year 4. Nevertheless, biochar’s positive effect on yields declined with time after application: e.g., BC10 matched BC0 yields in year 4. For the first three years, root nitrogen (N) concentrations were inversely correlated to yields and plant N% declined with biochar rate. In year 4 plant N% was directly correlated to plant biomass. In general, partitioning of nutrients between beet leaves and roots was not discernibly affected by the rate of biochar; an exception was boron whose preferential accumulation in leaves was directly related to the rate of biochar, indicating a role for the biochar for its mobilization.

Conclusions

Biochar had an immediate positive effect on the beet yields and affected plant stoichiometry. Initially this was independent of the biochar rate. Biochar’s utility declined with time at a rate inversely related to its application rate.

Implications or significance

Biochar is a recommendable fertility management tool for infertile, newly converted boreal Podzols; rates in the range of 10 Mg BC-C ha-1 may be repeated annually or every few years as practically feasible. Long term utilization requires further monitoring of micronutrients availability and uptake to inform any necessary management adjustments. Fertilizer management must consider the time since biochar’s addition to soil.

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Article 26/09/2023

Soil community catabolic profiles for a semiarid reclaimed surface coalmine

M. E. Tahtamouni, S. e. Khresat, M. Lucero, J. Sigala and A. Unc, International Journal of Mining, Reclamation and Environment 2023 Vol. 37 Issue 5 Pages 338-354, https://doi.org/10.1080/17480930.2023.2185438

Recovery of soil health offers insights into the mechanisms underpinning the stability of remediated ecosystems. Indirect assessment of enzymatic activity potential using substrate induced respiration (SIR), is commonly used to evaluate changes in soil microbial activity profiles, with their links to environmental and management factors. In this study, community level physiological profiling (CLPP) was employed to assess the impact of time on surface coal mine soil remediation. When compared with an adjoining control site, analysis of CLPP parameters offer useful insights and prospective tools for assessing soil health, following mining and remediation activities.

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Article 12/09/2023

A review of nematodes as biological indicators of sustainable functioning for northern soils undergoing land-use conversion. 

Young EH, Unc A. 2023. Applied Soil Ecology, 183: 104762, https://doi.org/10.1016/j.apsoil.2022.104762

Highlights

  • •New and existing boreal agriculture must be monitored for sustainability.
  • •Bioindicators can support management decisions pertinent to soil functions.
  • •Nematode assessments are reliable, cheap, and accessible.
  • •Literature on free-living nematode from boreal and arctic ecosystems is limited.

Abstract

Food webs and the functional status of soils are governed primarily by microbial carbon and nitrogen fluxes as determined by ecosystem type and management. In boreal regions, expanding and intensifying agriculture affects the functional status of soils due to biodiversity, carbon, and nitrogen losses. The status of northern soils must be monitored using informative, standardised methods that are comparable across land uses, managements, and scales. Food web nodes sensitive to complex changes in the soil environment, such as free-living nematodes, can be utilised to monitor alterations in the functional state of natural systems and inform management decisions to ensure that new and established agriculture is environmentally sustainable. The objectives of this a-priori review were to 1) describe the likely impacts of land use and land use change on nematode communities and indices in boreal regions, 2) determine if nematodes respond differently to land use and land use change in the global biomes, and 3) identify literature gaps related to nematodes in the boreal biome to draw attention to future research needs. Soil quality bioindicators were compared and 31 published, peer-reviewed, in-situ studies found in Web of Science and Scopus databases in March 2020 that assessed the impacts of land use and land use change on free-living nematode parameters across global biomes were systematically summarised. While the northern biomes have greater abundances of nematodes than other biomes, the literature search found zero articles pertaining to nematodes in boreal or Arctic agricultural systems highlighting the need for future work. Given the key roles that free-living nematodes have in the food web, their longer and more stable generation times than microbes, and relatively well-known taxonomy, life history traits, and feeding habits, the authors propose that nematodes could and ought to be employed as indicators of functional changes in boreal agricultural soils.

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Article 14/08/2023

Microbial denitrification

M. J. Goss, S. Blagodatsky and A. Unc, In: Encyclopedia of Soils in the Environment (Second Edition), edited by M. J. Goss and M. Oliver, Volume 1, 2023, Pages 261-269, Academic Press

https://doi.org/10.1016/B978-0-12-822974-3.00282-2

Denitrification is the transformation of plant available nitrogen (N) to gaseous forms that can return N to the atmospheric pool. Nitrous oxide, N2O, an important greenhouse gas is formed during both aerobic and anaerobic processes but the concentration of oxygen in the soil determines which processes predominate. The varied nature and uncertainties within the pathways, together with the range of gaseous products makes quantification of losses from soil particularly difficult. Fertilizer N accounts for about 43% of global N2O releases to the atmosphere from agriculture. The chapter summarizes the fundamental processes of N-transformation that generate gaseous forms of N.

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Article 14/08/2023

Soil respiration

J. D. Vallotton, S. Blagodatsky and A. Unc, In: Encyclopedia of Soils in the Environment (Second Edition), edited by M. J. Goss and M. Oliver, Volume 1, 2023, Pages 369-378, Academic Press 2023 

https://doi.org/10.1016/B978-0-12-822974-3.00264-0

Soil respiration is a useful indicator of global carbon balance and terrestrial carbon exchange with the atmosphere. Different soil carbon pools metabolize at variable rates based on environmental constraints on microbiological activity. Respiration is thus primarily controlled by climatic effects (temperature and hydrology) and soil management. Soil respiration can be measured both on site and in laboratory, with each method possessing distinct advantages and disadvantages relating to actual or potential respiration rates. These tests help us understand the importance of soil respiration as an indicator of soil conditions and C cycling and enable some predictions of changes in soil carbon under climate change.

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Article 14/08/2023

Microbial mobility and transport in soils

M. R. Mosaddeghi, A. Unc, A. A. Mahboubi and A. Safadoust, In: Encyclopedia of Soils in the Environment (Second Edition), edited by M. J. Goss and M. Oliver, Volume 1, 2023, Pages 512-521, Academic Press

DOI https://doi.org/10.1016/B978-0-12-822974-3.00276-7

Organic wastes are C-rich, beneficial amendments for improving soil conditions and plant growth. However, their land application is a major source of pathogenic microorganisms entering surface and groundwater systems. Persistence and transport of these microorganisms depend on interrelationships between properties of the organic amendments and seasonally variable environmental properties of the soil. Ionic and particulate components of amendments appreciably alter the physical and chemical properties of soil and microbe charged surfaces. Microbial persistence in soils determines the load of cells available for transport. Microorganism transport depends on structure-related macropore flow and their adsorption and desorption to soil and suspended particles.

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Article 14/08/2023

Septic systems and municipal waste disposal on land

C. P. Gerba, M. J. Goss and A. Unc, In: Encyclopedia of Soils in the Environment (Second Edition), edited by M. J. Goss and M. Oliver, Volume 1, 2023, Pages 567-577, Academic Press

https://doi.org/10.1016/B978-0-12-822974-3.00286-X

On-site – mainly septic systems – and centralized wastewater treatment systems treat vast volumes daily. Most wastewater from septic systems reaches soils via covered leaching beds. Municipal biosolids are applied to cropland for their nutrient value after receiving treatments of various intensity but the soil is relied on to act as a treatment medium by adsorbing and degrading contaminants, inactivating viruses, and reducing viability of other pathogens. The efficacy of soil treatment depends on climate, hydraulic loading which is managed to induce fast or slow infiltration, the hydraulic properties of the soil, and the functional state of the soil biology.

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