Bioavailability of Macro and Micronutrients Across Global Topsoils: Main Drivers and Global Change Impacts

Understanding the chemical composition of our planet\u27s crust was one of the biggest questions of the 20th century. More than 100 years later, we are still far from understanding the global patterns in the bioavailability and spatial coupling of elements in topsoils worldwide, despite their importance for the productivity and functioning of terrestrial ecosystems. Here, we measured the bioavailability and coupling of thirteen macro- and micronutrients and phytotoxic elements in topsoils (3–8 cm) from a range of terrestrial ecosystems across all continents (∼10,000 observations) and in response to global change manipulations (∼5,000 observations). For this, we incubated between 1 and 4 pairs of anionic and cationic exchange membranes per site for a mean period of 53 days. The most bioavailable elements (Ca, Mg, and K) were also amongst the most abundant in the crust. Patterns of bioavailability were biome-dependent and controlled by soil properties such as pH, organic matter content and texture, plant cover, and climate. However, global change simulations resulted in important alterations in the bioavailability of elements. Elements were highly coupled, and coupling was predictable by the atomic properties of elements, particularly mass, mass to charge ratio, and second ionization energy. Deviations from the predictable coupling-atomic mass relationship were attributed to global change and agriculture. Our work illustrates the tight links between the bioavailability and coupling of topsoil elements and environmental context, human activities, and atomic properties of elements, thus deeply enhancing our integrated understanding of the biogeochemical connections that underlie the productivity and functioning of terrestrial ecosystems in a changing world

A demographic analysis of sugar maple (Acer saccharum Marsh) seedlings at the species northern growth limit in Lake Superior Provincial Park, Ontario, Canada

Includes bibliographical references (pages [74]-80).M.S. (Master of Science

Short-term effects of wood ash application on soil properties, growth, and foliar nutrition of Picea mariana and Picea glauca seedlings in a plantation trial

Burning biomass for energy generates ash that could be applied as a soil amendment to ameliorate acidity and mitigate nutrient losses associated with biomass harvesting. These soil improvements may also enhance tree growth and foliar nutrition. In this study, we applied low- and high-carbon wood-derived ash at rates of 0 (control), 1000, and 10 000 kg·ha−1 (dry weight equivalents) to soils planted with Picea mariana (Mill.) B.S.P. and Picea glauca (Moench) Voss in a replicated (5) factorial design. We measured soil properties, tree seedling height, and foliar nutrient contents prior to and 4 mo after wood ash addition to determine the immediate effects on soil physical, chemical, and biological properties, and tree seedling performance. We conclude that there were no negative effects of applying either wood ash and that application of ash at 10 000 kg·ha−1, particularly with the low-carbon ash, produced the greatest changes. We anticipate that changes may become more evident over the longer term, especially with respect to tree growth and nutritional responses (e.g., as nutrient uptake demand increases) once the seedlings become more established.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Introductory Soils Courses: A Frontier of Soil Science Education in Canada

As the focus of soil science education in Canada and elsewhere has shifted towards non-soil science majors, it is important to understand if and how this has affected the scope of introductory soil science courses. The objectives of this study were to inventory Canadian postsecondary units that offer introductory soil science courses and to document attributes of instructors, students, and teaching approaches in these courses. We surveyed 58% of the instructors of introductory soil science courses across Canada, and most of these courses were offered by geography and environmental science units. The majority of instructors followed a traditional lecture (86%) and laboratory (76%) delivery format, while 36% used online teaching resources. Introductory courses were delivered by primarily one instructor, who held a PhD in a tenure track position and in most cases developed the course themselves. Over half of the instructors surveyed used either a required or a recommended textbook; pointing to the need for creation of a Canadian-authored soil science textbook. Several follow-up studies are needed to evaluate teaching methods used in the upper level soil science courses, studentâ s perceptions of teaching in soil science, and instructorsâ knowledge of resources available for online and/or blended learning.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Profiling Undergraduate Soil Science Education in Canada: Status and Projected Trends

Global declines in postsecondary enrollment in soil science programs over the last several decades have been mainly attributed to an overemphasis on the connection with agronomy and production agriculture but recent enrollment increases in the United States suggest change is afoot. To determine if similar trends are occurring in Canada, we inventoried undergraduate soil science course offerings at postsecondary institutions and conducted a survey to assess the status and projected trends in soil science education. We found that 64% of universities and 37% of colleges offer undergraduate soil science courses as part of degrees or diplomas where knowledge of soil science is important (e.g., agriculture, resource management). In Canada there are 149 undergraduate soil science courses taught in universities and 58 at colleges. On average, there are 3.2 courses taught at each university and 1.9 at each college that offer soil science courses. Soil science programs at the University of British Columbia, University of Saskatchewan, and University of Manitoba offer between 8 and 9 soil science courses and represent 17.4% of the national total. Enrollments in all courses across the country are projected to be steady with some anticipated growth, trends that are consistent with those reported in the United States and the Netherlands.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Bioavailability of macro and micronutrients across global topsoils:Main drivers and global change impacts

Understanding the chemical composition of our planet's crust was one of the biggest questions of the 20th century. More than 100 years later, we are still far from understanding the global patterns in the bioavailability and spatial coupling of elements in topsoils worldwide, despite their importance for the productivity and functioning of terrestrial ecosystems. Here, we measured the bioavailability and coupling of thirteen macro‐ and micronutrients and phytotoxic elements in topsoils (3–8 cm) from a range of terrestrial ecosystems across all continents (∼10,000 observations) and in response to global change manipulations (∼5,000 observations). For this, we incubated between 1 and 4 pairs of anionic and cationic exchange membranes per site for a mean period of 53 days. The most bioavailable elements (Ca, Mg, and K) were also amongst the most abundant in the crust. Patterns of bioavailability were biome‐dependent and controlled by soil properties such as pH, organic matter content and texture, plant cover, and climate. However, global change simulations resulted in important alterations in the bioavailability of elements. Elements were highly coupled, and coupling was predictable by the atomic properties of elements, particularly mass, mass to charge ratio, and second ionization energy. Deviations from the predictable coupling‐atomic mass relationship were attributed to global change and agriculture. Our work illustrates the tight links between the bioavailability and coupling of topsoil elements and environmental context, human activities, and atomic properties of elements, thus deeply enhancing our integrated understanding of the biogeochemical connections that underlie the productivity and functioning of terrestrial ecosystems in a changing world