Evaluating tree root distribution in a tree-based intercropping system with use of ground penetrating radar

Paper presented at the 13th North American Agroforesty Conference, which was held June 19-21, 2013 in Charlottetown, Prince Edward Island, Canada.In Poppy, L., Kort, J., Schroeder, B., Pollock, T., and Soolanayakanahally, R., eds. Agroforestry: Innovations in Agriculture. Proceedings, 13th North American Agroforestry Conference, Charlottetown, Prince Edward Island, Canada, June 19-21, 2013.Within agroforestry systems, tree root architecture is a driver of important ecological processes such as belowground nutrient flows and C storage. Yet the belowground component of trees remains largely under-studied due to methodological restraints. Conventional subsurface sampling can overlook the heterogeneity of root systems, while complete excavations are destructive and unrepeatable. Thus, there is a need to develop non-intrusive technologies, such as ground penetrating radar (GPR), to measure root systems in situ. In this study we used GPR to detect coarse root distributions below five tree species (Quercus rubra, Juglans nigra, Populus sp., Picea abies, and Thuja occidentalis) at a temperate tree-based intercropping site in Guelph, Ontario. GPR geo-imaged transects were collected in 4.5 _ 4.5m grids that were centered on 15 individual trees. Subsequently, tree roots were identified across all geo-images (visualized as radar signal reflections) providing 3-dimensional root distribution data for each target tree. Roots detected by GPR accounted for approximately 80% of large coarse roots (�1cm) and 40% of small coarse roots (<1cm) that were later exposed in a subset of matched soil profiles. Significant inter-specific variations of coarse rooting depth preferences were detected. Additionally, preliminary analyses indicate different tree rooting patterns below the crop rows. To determine fine root distributions, fine roots were extracted from soil cores collected from the tree root study plots. Preliminary analysis indicates fine root length densities vary across species predominately in the upper 20cm. Limitations will be identified and applications will be discussed of GPR to answer ecological questions within agroforestry systems. Notably, we will highlight results from our complementary study that used the same GPR data to effectively estimate belowground biomass.Kira A. Borden (1), Marney E. Isaac (2) and Sean C. Thomas (1) ; 1. Faculty of Forestry, University of Toronto, 33 Willcocks Street, Toronto, Ontario, Canada, M5S 3B3. 2. Department of Physical and Environmental Sciences, University of Toronto at Scarborough, 1265 Military Trail, Toronto, Ontario, Canada, M1C 1A4.Includes bibliographical references

Tree Roots in Agroforestry: Evaluating Biomass and Distribution with Ground Penetrating Radar

The root systems of five tree species (Populus deltoides × nigra clone DN-177, Juglans nigra, Quercus rubra, Picea abies, and Thuja occidentalis) are described following non-intrusive imaging using ground penetrating radar (GPR). This research aimed to 1) assess the utility of GPR for in situ root studies and 2) employ GPR to estimate tree root biomass and distribution in an agroforestry system in southern Ontario, Canada. The mean coarse root biomass estimated from GPR analysis was 54.1 ± 8.7 kg tree-1 (± S.E.; n=12), within 1 % of the mean coarse root biomass measured from matched excavations. The vertical distribution of detected roots varied among species, with T. occidentalis and P. abies roots concentrated in the top 20 cm and J. nigra and Q. rubra roots distinctly deeper. I evaluate these root systems based on their C storage potential and complementary root stratification with adjacent crops.MAS

Uncovering Tree Roots: How Radar Technology Can Help Scientists Better Understand Belowground Ecology

Just as the branches of a tree extend to support leaves that capture sunlight for photosynthesis, a tree’s root system extends into the soil in search of water and nutrients, and provides the tree its stability. However, the exact location of where the roots grow (often called ‘root distribution’) and the size or amount of roots (‘root biomass’) is extremely challenging to study in soil. Without digging the tree out of the ground, how can scientists study tree roots? Typically only parts of the root system are removed in a partial excavation or by taking soil core samples. However, there is a risk that by only measuring a portion of the root system, a lot of information might be missed (perhaps you have seen a tree uprooted and noticed how complex a tree root system can be). Unfortunately, excavating the entire tree root system can take a lot of time and energy, not to mention it is quite destructive

Interspecific variation of tree root architecture in a temperate agroforestry system characterized using ground-penetrating radar

This is an accepted manuscript of an article published in Plant and Soil.Background and aims Root system architecture regulates belowground access to soil resources. Variation in root architecture is important in agroforestry systems given management objectives to optimize resource acquisition between trees and crops. However, the distributions of live tree roots in agroforestry systems remain understudied due to methodological constraints. In this study, we used ground-penetrating radar (GPR) to describe variation in whole-plant root architecture among tree species at the same agricultural site, with a specific focus on vertical coarse and fine root distributions within the zone of competition with neighbouring crops. Methods Using GPR, we detected coarse roots of five trees species (Quercus rubra L., Juglans nigra L., Populus deltoides × nigra DN177, Picea abies (L.) Karst, and Thuja occidentalis L.) at a tree-based intercropping system in southern Ontario, Canada. A subset of soil profiles were assessed for GPR accuracy. A cumulative root distribution function was used to estimate the rooting depth (D95) of coarse roots. We also measured tree coarse root distributions and fine root density distributions 2 m into the crop rows, in the zone of competition. Results GPR accurately detected approximately 58 % of coarse roots for each study tree. Coarse root architecture varied among species, with differences in D95 and rooting patterns. Fine root length density distribution also varied among species, but was consistently high at 0.10 and 0.20 m depths regardless of species. Conclusions Our results suggest differential tree suitability for minimizing belowground competition with crops. Additionally, we illustrate the viability of GPR to characterize vertical profiles of live tree root systems, which is critical for improving our understanding of whole-plant functional traits and belowground plant interactions.Funding for this project was from Agriculture and Agri-Food Canada’s Greenhouse Gases Program, the Faculty of Forestry at the University of Toronto, and a Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant to MEI

Data_Sheet_1_Trade-offs in organic nutrient management strategies across mixed vegetable farms in Southwest British Columbia.docx

Balancing economic and environmental objectives can present trade-offs for organic farmers maximizing crop yields while maintaining core principles of ecology and health. A primary challenge for achieving this balance is nitrogen (N) and phosphorus (P) management. Meeting crop N requirements with compost can build soil carbon (C) and soil health but often over-applies P and increases soil P and associated environmental risks. Alternatively, high-N organic fertilizers can provide N without surplus P but can be expensive and lack C inputs that composts supply. We evaluated these potential trade-offs in 2-year field trials on 20 mixed vegetable farms across three regions of Southwest British Columbia, Canada, capturing a range of climatic-edaphic conditions and organic amendments. Three nutrient management strategies were evaluated: High Compost: compost applied to meet crop N removal, Low Compost + N: compost applied to meet crop P removal plus an organic fertilizer to meet crop N removal, and Typical: varying combinations of composts and/or organic fertilizers (“typical” nutrient application on the farm). Nutrient strategies were evaluated in terms of yield, input costs, and soil properties [permanganate oxidizable C (labile C responsive to soil management), and post-season available N and P]. Soil P was 21% higher with High Compost than Low Compost + N. In one region characterized by inexpensive but nutrient-rich composts and soils high in P, input costs were lowest with Typical, but in the second year, High Compost outperformed Typical in crop yield. Principal component analysis showed a divergence in post-season NO3- between nutrient strategies in relation to compost and soil properties: High Compost using high-N composts increased post-season NO3- (0–30 cm), whereas relative yields in High Compost tended to be higher on farms with lower soil C and lower C:N composts, while yields with Typical were higher under opposite conditions but associated with higher post-season NO3-. Combining input types (e.g., Low Compost + N) can meet environmental objectives in reducing surplus soil P without short-term yield or cost trade-offs compared to High Compost. However, maintaining soil C needs to be investigated to achieve effective ecological nutrient management in organic vegetable production with improved nutrient balances.</p

Integrating nitrogen fixing structures into above- and belowground functional trait spectra in soy (Glycine max)

This is an accepted manuscript of an article published in Plant and Soil.Aims Phenotypic trait variation across environmental gradients and through plant ontogeny is critical in driving ecological processes, especially in agroecosystems where single genotypes exist in high abundances. While variability in root traits plays a key role in belowground processes, few studies have identified the presence of an intraspecific “Root Economics Spectrum” (RES) within domesticated plants. Furthermore, little is known regarding if an intraspecific RES changes through plant ontogeny, and how trophic interactions – namely root nodulation – relate to above- or belowground trait spectra. Methods We evaluated covariation among 12 root, nodule, leaf, and stem traits in 134 plants of a single genotype of soy (Glycine max). Variation in these traits was assessed across five managed environmental conditions, and three plant ontogenetic stages. Results Root traits covaried along an intraspecific RES that represents a trade-off between resource acquisition and resource conservation. Variation along the RES was closely coordinated with hydraulic traits, but was orthogonal to nodule and leaf economics traits. Trait relationships varied strongly across managed environmental conditions and plant developmental stages. Conclusions Our results indicate the presence of an intraspecific RES in soy that is independent of root nodule investment. Patterns of phenotypic variation in below and aboveground soy traits demonstrate multivariate trait syndromes vary across environmental gradients and are dynamic through plant ontogeny.This research was undertaken in part based on funding from the Canada Research Chairs program and a Natural Sciences and Engineering Research Council of Canada Discovery Grant to Marney E. Isaac, as well as a graduate research assistantship granted to Fallon Hayes courtesy of the Department of Physical and Environmental Sciences, University of Toronto Scarborough

Agroecology in Canada: Towards an Integration of Agroecological Practice, Movement, and Science

This article surveys the current state of agroecology in Canada, giving particular attention to agroecological practices, the related social movements, and the achievements of agroecological science. In each of these realms, we find that agroecology emerges as a response to the various social and ecological problems associated with the prevailing industrial model of agricultural production that has long been promoted in the country under settler colonialism. Although the prevalence and prominence of agroecology is growing in Canada, its presence is still small and the support for its development is limited. We provide recommendations to achieve a more meaningful integration of agroecology in Canadian food policy and practice.Land and Food Systems, Faculty ofNon UBCReviewedFacult