• NSERC: Discovery Grant (PI) 2022-2027
  • Clusters of Scholarly Prominence UTSC, Sustainable Food and Farming Futures Cluster (PIs M.E. Isaac and J. Sharma) 2021-2024
  • NSERC CREATE Design of Living Infrastructure for Ecosystem Services (PI J. Drake; Co-applicant: M.E. Isaac) 2019-2024
  • Agriculture and Agri-Food Canada, Agriculture Greenhouse Gases Program (PI N. Thevathasan, University of Guelph), 2017-2021
  • NSERC: Discovery Grant (P.I.), 2015-2022
  • Canada Research Chair (Tier 2), 2013-2018
  • SSHRC: Insight Development Grant (P.I.), 2011-2016
  • Agriculture and Agri-Food Canada, Agriculture Greenhouse Gases Program (P.I. A. Gordon, University of Guelph), 2011-2015
  • Canadian Foundation for Innovation (P.I), 2011, 2014
  • Ministry of Research and Innovation (P.I.), 2011, 2014
  • STINT Initiation Grant (P.I. G. Carlsson, Swedish Agricultural University), 2011-2012
  • Teaching Enhancement Grant, UTSC, 2011
  • IDRC/AUCC, CAREG (Co-P.I. with FORIG, Ghana) 2010-2012
  • Connaught Grant (P.I.), 2009-2011

Current Research Topics

Ecophysiology and biogeochemistry in agroforestry systems

Diverse agroecosystems are increasingly being recognized as an environmentally and economically sustainable alternative to biologically simplified conventional agricultural systems. Increasing diversity in agroecosystems, in particular the integration of perennial crops or trees (agroforestry), is one such alternative. Research has shown that interspecific interactions in multispecies agroforestry systems, operating at various spatial and temporal scales, confer many environmental benefits. Generally, the inclusion of greater diversity in agroecosystems has been shown to augment nutrient capture and cycling processes leading to a reduced reliance on fertilizers, while simultaneously enhancing the provisioning of other ecosystem services such as carbon sequestration or hydrological cycling. The overall objective is to determine optimal plant associations that maximize nutrient cycles and minimize external inputs. To do this, we test interactions in three diversified systems: Theobroma cacao (cocoa) agroforestry systems of Ghana, Coffea arabia (coffee) agroforestry systems of Central America and tree-based intercropping systems of Southern Ontario. We investigate nutrient and non-nutrient resource interactions on growth and nutritional response in perennial agricultural systems. My research group has also made notable technical progress in tree root ecology research, developing methods to perform some of the first applications of near-surface radar for non-invasive imaging of live tree roots in agroforestry systems.

The role of resource limitation on biological nitrogen fixation

Agricultural intensification has had unintended environmental consequences and the main source of this problem is excessive mineral fertilization, with subsequent disruption of localized biogeochemical processes under intensively managed monoculture cropping systems. The future of agricultural systems will require reduced dependency on external inputs and non-renewable resources as nutrient sources, providing a quantifiable ecosystem service. Therefore, I argue, the cultivation of N2 fixing legumes should be expected to rise and advanced work on nitrogen (N) budgets is urgently needed. The incorporation of dinitrogen (N2)-fixing crops and trees within agriculture has garnered attention from researchers, development organizations, governments, and farmers, as a revival of pro-environmental agricultural management. My research group has elucidated the magnitude of multiple determinants [soil phosphorous, light, nitrate deposition in throughfall, water limitation] on rates of biological N2 fixation and the transfer of fixed N in multiple agroforestry systems using 15N tracers and natural abundance analysis. With my graduate students, we assessed effects of N2 fixing trees on soil microbial populations and the fate of fixed N in multi-species systems.

Causes and consequences of functional traits in agroecosystems


Despite an interest in increasingly complex agroforestry arrangements and expanding suites of environmental response variables of interest, crop performance in response to agroforestry management remains primarily evaluated in strict agronomic approaches. Although classic agronomic paradigms have undoubtedly framed numerous important insights and management advances, their ability to test hypotheses on the mechanistic linkages between crops and ecological processes is tenuous. By comparison, understanding of the causes and consequences of functional trait variation in crops could provide novel insights into management effects on critical ecosystem processes in agroecological and agroforestry systems. Conceptually, analyses of functional trait variation among co-occurring species have provided important insights into the mechanistic bases of several contemporary ecological processes including plant-soil nutrient feedbacks and ecosystem carbon dynamics; they also simultaneously provide a framework for predicting future ecosystem responses to environmental change. While there is considerable opportunity to explore how trait-based research can be applied to questions in agroecosystem management, to date there are critical gaps that have limited this avenue of research, which my group addresses.

 Agrarian information networks and agroecosystem management

The current trend toward integrative and interdisciplinary ecological and social research is timely and exciting.  Accordingly, my research incorporates new approaches for understanding influences on agroforestry management, particularly the examination of farmer communication patterns.  The promotion of informal information networks can compensate for barriers to appropriate information on diversified agricultural management and lead to high adoption of land management approaches to improve ecosystem services. I concentrate my research efforts on informal networks and coupling local knowledge and land use change in production systems.