Variation in fine root traits reveals nutrient-specific acquisition strategies in agroforestry systems
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Variation in fine root traits reveals nutrient-specific acquisition strategies in agroforestry systems Kira A. Borden & Sean C. Thomas & Marney E. Isaac
Received: 20 September 2018 / Accepted: 20 February 2019 # Springer Nature Switzerland AG 2019
Abstract Aims Changes in root functional traits reveal important nutrient acquisition strategies, with well documented patterns in root trait expression within complex communities or along gradients of singular nutrients. In this field study, we investigate intra-root functional trait expression with six soil macro- and micro-nutrients in Theobroma cacao agroforestry systems. Methods Using image, chemical, and spatial analysis, the fine root distribution, architecture, and morphology of T. cacao were compared to localized soil nutrients on two-dimensional soil profiles with conspecific and heterospecific neighbours. Results Fine-scale variation in soil nutrients was observed within the range of T. cacao root systems. Higher
NH4+ and Ca2+ was associated with greater root length and biomass densities, coupled with greater investment to individual roots, expressed as increased fine root tissue density and diameter and lower specific root length. Conversely, NO3− had the opposite effect. Overall, roots tended towards higher acquisitive trait values when next to a shade tree. Conclusions Plants generally employ several concomitant and at times opposing strategies for nutrient acquisition in heterogeneous soils. We show that fine-scale root plasticity is highly linked to localized nutrientspecific and neighbour-specific effects, driving patterns of nutrient acquisition in agroforestry systems. Keywords Functional traits . Intercropping . Nutrient distribution . Root foraging . Root system . Theobroma cacao
Responsible Editor: Zhun Mao. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11104-019-04003-2) contains supplementary material, which is available to authorized users. K. A. Borden : M. E. Isaac (*) Department of Geography & Planning, University of Toronto, 100 St. George Street, Toronto, Ontario M5S 3G3, Canada e-mail: [email protected] K. A. Borden : M. E. Isaac Department of Physical & Environmental Sciences, University of Toronto Scarborough, 1265 Military Trail, Toronto, Ontario M1C 1A4, Canada S. C. Thomas Faculty of Forestry, University of Toronto, 33 Willcocks Street, Toronto, Ontario M5S 3B3, Canada
Abbreviations A:T Ratio of absorptive to transport fine root length D Average root diameter FRLD Fine root length density FRBD Fine root biomass density RTD Fine root tissue density SRL Specific root length
Introduction Agroforestry is a prime example of applied ecology: species combinations are, in principle, chosen to enhance niche complementarity and/or facilitation, and
Plant Soil
thus improve nutrient cycles. The success of these interactions largely depends on differences in plant root functions and/or spatial distributions that, when compared to monocultures, permit more complete acqu
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