Carbon sequestration potential of a 27-year-old tree-based intercropping system in southwestern Ontario

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.This study aimed to quantify carbon (C) pools and fluxes in a 27-year-old tree-based intercropping (TBI) system as compared to a conventional agricultural system at the University of Guelph�s Agroforestry Research Station (43o 16�N 89o 26�W) (established 1987). Tree species quantified during this study include poplar hybrid (Populus spp.), Norway spruce (Picea abies), red oak (Quercus rubra), black walnut (Juglans nigra), and white cedar (Thuja occidentalis). In the TBI system, above- and belowground biomass, along with soil organic carbon (SOC) concentrations, litterfall, litter decomposition and soil respiration were quantified. In the conventional agricultural field, SOC, litter decomposition and soil respiration were quantified. Preliminary results indicated higher C sequestration potential rate with faster growing species such as poplar, and slower potential rate for slower growing species such as spruce and cedar. SOC accumulation was highest in the predominant wind direction (east), closest to the tree rows (0.5 m), and at shallower depths (10-20 cm) for all species. SOC accumulation was highest under poplar tree, followed by spruce, oak and walnut. Quantities of litterfall followed similar pattern and decomposition rates are still being analyzed. Soil respiration rates were higher in TBI systems and at distances closer to the tree row. Further results will be presented on the total measured C pools and fluxes and the importance of C sequestration potential of a 27-year-old TBI system to sequester atmospheric C and mitigate climate change. Accumulation of SOC can also have implications on crop yields and long term stability of TBI soils.Amy Wotherspoon (1), Idris Mohammed (1), Naresh V. Thevathasan (1), Andrew M. Gordon (1), and R. Paul Voroney (1) ; 1. School of Environmental Sciences, University of Guelph, Guelph, ON, Canada, N1G 2W1.Includes bibliographical references

Productivity and Carbon Storage in Silvopastoral Systems with \u3cem\u3ePinus ponderosa\u3c/em\u3e and \u3cem\u3eTrifolium\u3c/em\u3e spp. Plantations and Pasture on a Volcanic Soil in the Chilean Patagonia

Little information is available about carbon (C) sequestration potentials in ecosystems on Andisols of the Chilean Patagonia. This study was undertaken to measure the size of the C stocks in three predominant ecosystems: Pinus ponderosa-based silvopastoral systems (SPS), pine plantations (PPP) and natural pasture (PST), and to examine how clover (Trifolium spp.) affect tree growth and stocks of soil C. The C contents of trees and pasture were determined by destructive sampling and dry combustion. Soil samples were taken at 0-5, 5-20, 20-40 cm depths in order to determine soil C and N. For PPP and SPS, respectively, 38.4 and 53.1 kg/tree of total tree C were stored aboveground, whereas 21.3 and 23.4 kg/tree were stored belowground. Tree diameter at breast height increased 1 and 2 cm/year in PPP and SPS, respectively, and was significantly higher in SPS, an interesting value for the region. Tree growth in SPS was enhanced by lower tree competition and the additional soil N provided by the leguminous pasture, resulting in larger amounts of C being sequestered. Soil organic C (SOC) stocks at 0-40 cm depth were 193.76, 177.10 and 149.25 Mg/ha in SPS, PST and PPP, respectively. The conversion of PPP to SPS and PST to PPP resulted in an increase of 44.51 Mg/ha and a decrease of 27.85 Mg/ha in SOC, respectively, at 0-40 cm soil depth. A favourable micro-climate (air temperature, soil moisture) has been observed in SPS as well as a synergistic effect between trees and pasture

Photosynthetic Response of Soybean to Microclimate in 26-Year-Old Tree-Based Intercropping Systems in Southern Ontario, Canada.

In order to study the effect of light competition and microclimatic modifications on the net assimilation (NA), growth and yield of soybean (Glycine max L.) as an understory crop, three 26-year-old soybean-tree (Acer saccharinum Marsh., Populus deltoides X nigra, Juglans nigra L.) intercropping systems were examined. Tree competition reduced photosynthetically active radiation (PAR) incident on soybeans and reduced net assimilation, growth and yield of soybean. Soil moisture of 20 cm depth close (< 3 m) to the tree rows was also reduced. Correlation analysis showed that NA and soil water content were highly correlated with growth and yield of soybean. When compared with the monoculture soybean system, the relative humidity (RH) of the poplar-soybean, silver maple-soybean, and black walnut-soybean intercropped systems was increased by 7.1%, 8.0% and 5.9%, soil water content was reduced by 37.8%, 26.3% and 30.9%, ambient temperature was reduced by 1.3°C, 1.4°C and 1.0°C, PAR was reduced by 53.6%, 57.9% and 39.9%, and air CO2 concentration was reduced by 3.7μmol·mol(-1), 4.2μmol·mol(-1) and 2.8μmol·mol(-1), respectively. Compared to the monoculture, the average NA of soybean in poplar, maple and walnut treatments was also reduced by 53.1%, 67.5% and 46.5%, respectively. Multivariate stepwise regression analysis showed that PAR, ambient temperature and CO2 concentration were the dominant factors influencing net photosynthetic rate

Plant Diversity and Agroecosystem Function in Riparian Agroforests: Providing Ecosystem Services and Land-Use Transition

Achieving biologically diverse agricultural systems requires a commitment to changes in land use. While in-field agrobiodiversity is a critical route to such a transition, riparian systems remain an important, yet understudied, pathway to achieve key diversity and ecosystem services and targets. Notably, at the interface of agricultural landscapes and aquatic systems, the diversification of riparian buffers with trees reduces the non-point source pollution in waterways. However, in riparian agroforestry systems, little is known about herbaceous community patterns and, importantly, the herbaceous community&rsquo;s role in governing carbon (C) and nitrogen (N) cycling. Our study investigated herbaceous community taxonomic and phylogenetic diversity patterns in riparian (i) grasslands (GRASSLAND), (ii) rehabilitated agroforests (AGROFOREST-REHAB), and (iii) remnant forests (AGROFOREST-NATURAL). We then determined the biodiversity-ecosystem function relationships between community functional diversity metrics, C and N cycling, and greenhouse gas fluxes. We observed significant differences in taxonomic and phylogenetic diversity among riparian buffer types. We found that herbaceous plant communities in riparian agroforestry systems expressed plant trait syndromes associated with fast-growing, resource acquiring strategies, while grassland buffer plants exhibited slow-growing, resource conserving strategies. Herbaceous communities with high functional diversity and resource acquiring trait syndromes, such as those in the agroforestry riparian systems, were significantly correlated with lower rates of soil CO2 efflux and N mineralization, both of which are key fluxes related to ecosystem service delivery. Our findings provide further evidence that functionally diverse, and not necessarily taxonomically diverse, plant communities are strongly correlated to positive ecosystem processes in riparian agroforestry systems, and that these communities contribute to the transition of agricultural lands toward biologically and functionally diverse landscapes

Within plot microclimate and soybean responses 2, 4, and 6 m from tree row to three 26-year-old hardwood intercropping systems and monocropped soybeans.

<p>Across all treatments (control, poplar, maple, walnut), values in each row followed by the same letter are not significantly different (Tukey’s HSD, P<0.05).</p><p>* Significant at P<0.10 (10%) level.</p><p>Within plot microclimate and soybean responses 2, 4, and 6 m from tree row to three 26-year-old hardwood intercropping systems and monocropped soybeans.</p

Multiple regression analysis of environmental factors and photosynthetic rates of soybean in different treatments in 2012.

<p>*, ** indicate significant at 5% and 1% levels, respectively.</p><p>Note: Y is the predicted value of NA, X₁ is PAR, X₂ is air temperature, X₃ is RH, X₄ is CO₂ concentration, and X₅ is soil water content.</p><p>Multiple regression analysis of environmental factors and photosynthetic rates of soybean in different treatments in 2012.</p

Sampling locations from the tree row into the cropping alley.

<p>The crop like symbol refer to sample plot.</p

12 and 26-year-old trees (1997 and 2012, respectively) intercropped with soybean at the same study site.

<p>Note: DBH is the diameter at breast height of tree.</p><p>^a Data of 1997 adapted from Simpson [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0129467#pone.0129467.ref022" target="_blank">22</a>].</p><p>^b1997 data not measured.</p><p>12 and 26-year-old trees (1997 and 2012, respectively) intercropped with soybean at the same study site.</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