EnRoot: a narrow-diameter, inexpensive and partially 3D-printable minirhizotron for imaging fine root production

Abstract

Background Fine root production is one of the least well understood components of the carbon cycle in terrestrial ecosystems. Minirhizotrons allow accurate and non-destructive sampling of fine root production. Small and large scale studies across a range of ecosystems are needed to have baseline data on fine root production and further assess the impact of global change upon it; however, the expense and the low adaptability of minirhizotrons prevent such data collection, in worldwide distributed sampling schemes, in low-income countries and in some ecosystems (e.g. tropical forested wetlands). Results We present EnRoot, a narrow minirhizotron of 25 mm diameter, that is partially 3D printable. EnRoot is inexpensive (€150), easy to construct (no prior knowledge required) and adapted to a range of ecosystems including tropical forested wetlands (e.g. mangroves, peatlands). We tested EnRoot’s accuracy and precision for measuring fine root length and diameter, and it yielded Lin’s concordance correlation coefficient values of 0.95 for root diameter and 0.92 for length. As a proof of concept, we tested EnRoot in a mesocosm study, and in the field in a tropical mangrove. EnRoot proved its capacity to capture the development of roots of a legume ( Medicago sativa ) and a mangrove species (seedlings of Rhizophora mangle ) in laboratory mesocosms. EnRoot’s field installation was possible in the root-dense tropical mangrove because its narrow diameter allowed it to be installed between larger roots and because it is fully waterproof. EnRoot compares favourably with commercial minirhizotrons, and can image roots as small as 56 µm. Conclusion EnRoot removes barriers to the extensive use of minirhizotrons by being low-cost, easy to construct and adapted to a wide range of ecosystem. It opens the doors to worldwide distributed minirhizotron studies across an extended range of ecosystems with the potential to fill knowledge gaps surrounding fine root production.

Fine root production in a chronosequence of mature reforested mangroves

“…We measured fine root (< 2 mm diameter) production using the EnRoot system, a minirhizotron designed for use in mangroves (see full description in Arnaud et al ., 2019). Commercially available minirhizotrons were unsuitable because their soil tubes were too large to fit between the stilt roots of Rhizophora and were impractical for remote swamps (too heavy, too large, camera not waterproof, need for power supply).…”

“…We used the EnRoot minirhizotron technique described by Arnaud et al (2019) to investigate fine root production in one of the largest restored mangroves in the world, in the Mekong Delta in Vietnam. We used a chronosequence to test whether:…”

“…We used the EnRoot minirhizotron technique described by Arnaud et al . (2019) to investigate fine root production in one of the largest restored mangroves in the world, in the Mekong Delta in Vietnam. We used a chronosequence to test whether: fine root production differed with stand age in reforested mangrove; fine root production had depth‐related patterns that accorded with reforested mangrove stand age. …”

The Ecology Underground coalition: building a collaborative future of belowground ecology and ecologists

“…Some key frontiers in this area of research include: (1) integrating root economics with root evolution (Valverde‐Barrantes et al ., 2020); (2) identifying trade‐offs between fine‐root and mycorrhizal fungal traits and the emergent traits from their partnerships (McCormack & Iversen, 2019); (3) adopting a whole plant perspective (Weemstra et al ., 2020); and (4) exploring patterns of intraspecific root and fungal trait variations (Defrenne et al ., 2019). These frontiers will be crossed as we start linking root and fungal trait databases, create new databases (TraitAM, Chaudhary et al ., 2020), develop novel techniques for the study of fine roots (R hizovision , Seethepalli et al ., 2020; E n R oot , Arnaud et al ., 2019) and standardize root classification, sampling, processing and trait measurements (Freschet et al ., 2020a).…”

A 3D Print Repository for Plant Phenomics

“…Therefore, 3D printing so far is largely being used to alleviate specific research problems which are likely routine or repetitive tasks and/or benefit from equipment standardization minimizing error. A small majority of 3D print papers focused on plant roots [ 3 – 7 ], which likely reflects the challenge of phenotyping roots and the need for custom solutions.…”