Fiona Marie Soper

McGill University | McGill · Department of Biology

Arid and semiarid landscapes comprise ~40% of the earths' terrestrial land surface and are expected to be particularly susceptible to global change factors. As a result, there is considerable interest in the mechanisms defining the magnitude of surface-atmosphere carbon dioxide exchange in arid lands. We assessed the isotopic composition of soil-em...

Biological nitrogen fixation (BNF) in woody plants is often investigated using foliar measurements of δ15N and is of particular interest in ecosystems experiencing increases in BNF due to woody plant encroachment. We sampled δ15N along the entire N uptake pathway including soil solution, xylem sap, and foliage to: 1) test assumptions inherent to th...

Tropical forests exhibit significant heterogeneity in plant functional and chemical traits that may contribute to spatial patterns of key soil biogeochemical processes, such as carbon storage and greenhouse gas emissions. Although tropical forests are the largest ecosystem source of nitrous oxide (N2O), drivers of spatial patterns within forests ar...

The mechanistic links between nitrogen (N) availability and investment in plant phosphorus (P) acquisition have important implications for plant growth, species distributions, and responses to CO2 fertilization under global change, especially in P‐poor tropical ecosystems. Currently, it is unclear whether investment in strategies that enhance plant...

Difficulty in quantifying rates of biological N fixation (BNF), especially over long time scales, remains a major impediment to defining N budgets in many ecosystems. To estimate N additions from BNF, we applied a tree-scale N mass balance approach to a well-characterized chronosequence of woody legume (Prosopis glandulosa) encroachment into subtro...

Plants express diverse nutrient use and acquisition traits, but it is unclear how trait combinations at the species level are constrained by phylogeny, trait coordination, or trade‐offs in resource investment. One trait – nitrogen (N) fixation – is assumed to correlate with other traits and used to define plant functional groups, despite potential...

The Amazon Basin is at the center of an intensifying discourse about deforestation, land-use, and global change. To date, climate research in the Basin has overwhelmingly focused on the cycling and storage of carbon (C) and its implications for global climate. Missing, however, is a more comprehensive consideration of other significant biophysical...

The role of lowland tropical forest tree communities in shaping soil nutrient cycling has been challenging to elucidate in the face of high species diversity. Previously, we showed that differences in tree species composition and canopy foliar nitrogen (N) concentrations correlated with differences in soil N availability in a mature Costa Rican rai...

Climate change is a worldwide threat to biodiversity and ecosystem structure, functioning, and services. To understand the underlying drivers and mechanisms, and to predict the consequences for nature and people, we urgently need better understanding of the direction and magnitude of climate‐change impacts across the soil–plant–atmosphere continuum...

Mangrove forests play an important role in climate change adaptation and mitigation by maintaining coastline elevations relative to sea level rise, protecting coastal infrastructure from storm damage and storing substantial quantities of carbon (C) in live and detrital pools. Determining the efficacy of mangroves in achieving climate goals can be c...

This article is a Commentary on Bourgeois et al. 223: 1784–1794.

High rates of land conversion and land use change have vastly increased the proportion of secondary forest in the lowland tropics relative to mature forest. As secondary forests recover following abandonment, nitrogen (N) and phosphorus (P) must be present in sufficient quantities to sustain high rates of net primary production and to replenish the...

Forest dynamics and tree species composition vary substantially between Paleotropical and Neotropical forests, but these broad biogeographic regions are treated uniformly in many land models. To assess whether these regional differences translate into variation in productivity and carbon (C) storage, we compiled a database of climate, tree stem gro...

Though tropical forest ecosystems are among the largest natural sources of the potent greenhouse gas nitrous oxide (N2O), the spatial distribution of emissions across landscapes is often poorly resolved. Leaf cutter ants (LCA; Atta and Acromyrmex, Myrmicinae) are dominant herbivores throughout Central and SouthAmerica, and influencemultiple aspects...

Handbook for standardized methods in terrestrial global change experiments

Tropical forests exhibit significant heterogeneity in plant functional and chemical traits that may contribute to spatial patterns of key soil biogeochemical processes, such as carbon storage and greenhouse gas emissions. Although tropical forests are the largest ecosystem source of nitrous oxide (N2O), drivers of spatial patterns within forests ar...

Biological pumping of mineral elements (root uptake from the soil and concentration at the surface via litterfall) may be an important mechanism influencing their loss from terrestrial ecosystems by accelerating transport in runoff, though few estimates exist to assess this. In the Susquehanna Shale Hills Critical Zone Observatory (a temperate fore...

Primary tropical rainforests are generally considered to be relatively nitrogen (N) rich, with characteristically large hydrologic and gaseous losses of inorganic N. However, emerging evidence suggests that some tropical ecosystems can exhibit tight N cycling, with low biologically available losses. In this study, we combined isotopic data with a w...

Actinorhizal plants form symbiotic root associations with dinitrogen (N2 ) xing Frankia and are abundant in North American cold deserts. However, the extent to which actinorhizal species are actively xing N2 or altering ecosystem nitrogen (N) availability remains unclear. We used the 1 5N natural abundance technique to measure how three widespread...

Tropical forests exhibit significant heterogeneity in plant functional and chemical traits that may contribute to spatial patterns of key soil biogeochemical processes, such as carbon storage and greenhouse gas emissions. Although tropical forests are the largest ecosystem source of nitrous oxide (N2O), drivers of spatial patterns within forests ar...

Arid soils represent a substantial carbonate pool, and may participate in surface-atmosphere CO2 exchange via a diel cycle of carbonate dissolution and exsolution. We used a Keeling plot approach to determine the substrate δ13C of CO2 emitted from carbonate-dominated soils in the Mojave Desert, and found evidence for a non-respiratory source that i...

Information on denitrification (particularly N2) losses from dry ecosystems is limited despite their large area. Here, we present the first direct denitrification measurements for a northern hemisphere savanna, a Prosopis-dominated grassland/grove matrix in south Texas. We used the gas-flow intact soil core method to quantify N2, N2O and CO2 losses...

Savanna ecosystems are a major source of nitrogen (N) trace gases that influence air quality and climate. These systems are experiencing widespread encroachment by woody plants, frequently associated with large increases in soil N, with no consensus on implications for trace gas emissions. We investigated the impact of encroachment by N-fixing tree...

Difficulty in quantifying rates of biological N fixation (BNF), especially over long time scales, remains a major impediment to defining N budgets in many ecosystems. To estimate N additions from BNF, we applied a tree-scale N mass balance approach to a well-characterized chronosequence of woody legume (Prosopis glandulosa) encroachment into subtro...

Water and nitrogen (N) interact to influence soil N cycling and plant N acquisition. We studied indices of soil N availability and acquisition by woody plant taxa with distinct nutritional specialisations along a north Australian rainfall gradient from monsoonal savanna (1600-1300 mm annual rainfall) to semi-arid woodland (600-250 mm). Aridity resu...

Background/Question/Methods Graduate programs are increasingly recognizing the importance of explicit mentorship training for future faculty members. However, few students receive training specific to the unique practical and pedagogical challenges of mentoring in a field research context. This is problematic given that fieldwork and field course...

Background/Question/Methods Predicting the magnitude of symbiotic nitrogen (N) fixation by woody plants has traditionally been impeded by the difficulty of measuring fixation rates in the field. Foliar δ15N measurement is the most commonly applied method for estimating fixation in woody perennials, especially when root nodules cannot be reliably...

Background/Question/Methods Woody encroachment of nitrogen (N)-fixing trees has occurred extensively throughout semi-arid, subtropical grasslands and savannas over the last 150 years. In the Rio Grande Plains of Texas, encroachment of N-fixing Prosopis glandulosa (honey mesquite) is widespread and leads to soil N accretion, presumably from large...

While importance of amino acids as a nitrogen source for plants is increasingly recognised, other organic N sources including small peptides have received less attention. We assessed the capacity of functionally different species, annual and nonmycorrhizal Arabidopsis thaliana (L.) Heynh. (Brassicaceae) and perennial Lobelia anceps L.f. (Campanulac...

Background/Question/Methods Organic nitrogen (ON) is the most abundant nitrogen (N) form in most soils and includes compounds ranging from single amino acids to high molecular weight proteins. Despite increasing recognition that many species access amino acids as a N source, more complex forms of ON have not previously been considered accessible...

Modern agriculture is based on the notion that nitrate is the main source of nitrogen (N) for crops, but nitrate is also the most mobile form of N and easily lost from soil. Efficient acquisition of nitrate by crops is therefore a prerequisite for avoiding off-site N pollution. Sugarcane is considered the most suitable tropical crop for biofuel pro...