Allometric equations for the invasive vine air potato (Dioscorea bulbifera) in its exotic range in Florida

Authors: Rayamajhi, Min; ROHRIG, ERIC - Florida Department Of Agriculture And Consumer Services; Tipping, Philip; Pratt, Paul; Leidi, Jorge

Submitted to: Invasive Plant Science and Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/7/2020
Publication Date: 5/14/2020
Citation: Rayamajhi, M.B., Rohrig, E., Tipping, P.W., Pratt, P.D., Leidi, J.G. 2020. Allometric equations for the invasive vine air potato (Dioscorea bulbifera) in its exotic range in Florida. Invasive Plant Science and Management. 13(2):76-83. https://doi.org/10.1017/inp.2020.15.
DOI: https://doi.org/10.1017/inp.2020.15

Interpretive Summary: We developed allometric equations to estimate total and fractional biomass, quantities of aerial bulbils, and underground tubers of field grown Dioscorea bulbifera from natural areas in Florida. We selected four naturally infested sites representing its southern, central, and northern distribution in Florida. Across these four sites we measured patch area, stem densities, stem-base diameters and top crown height of 84 (21 site-1) discrete D. bulbifera patches late in the growing season of 2012. We destructively harvested select plants within each patch, sorted and weighed each by components (stems, leaves, bulbils, tubers and roots), counted units of regenerative structures (bulbils and underground tubers) patch-1, and dried to a constant weight. Patch area, patch height, stem density and basal diameter of the stem ranged widely from 0.02-13.6 m2, 0.01-7.00 m, 1-53, and 0.30-5.50 mm, respectively. Mean percentages of root, tuber, stem, leaf and bulbil fractions in total patch biomass were 1.43, 40.57, 15.59, 26.06 and 16.36, respectively. Optimal predictive models were developed for total D. bulbifera biomass, separate components (root, tuber, stem, leaf, and bulbil), and densities of regenerative structures (aerial bulbil and underground tuber). Predictive models provide a non-destructive method for estimating biomass components and units of vegetative structures capable of producing plants based on D. bulbifera patch size, stem density, stem diameter, and patch height. These models are critical for understanding the primary productivity of D. bulbifera in its exotic range, quantifying the influence of herbivory from intentionally introduced biological control agents, and estimating conventional control costs.

Technical Abstract: Dioscorea bulbifera L. (air potato), the exotic invasive plant of Afro-Asian origin has invaded public and private landscapes across Florida and other states in southeastern USA. Its prolific growth rate results in long vines that branch profusely, blanket native vegetation, kill plants underneath and produce a large number of vegetative propagules (bulbils). Vines die in fall and sprout back in spring. Various management methods (chemical, mechanical, cultural and biological) have been deployed to minimize its impact on native plant communities in various landscapes. More recently, biological control has significantly reduced this weedy vine’s impact at the landscapes level in various parts of Florida and some areas of the neighboring states. In order to gauge the effectiveness of biocontrol and other measures in suppressing biomass production and plant recruitment throughout its distribution range, a simple non-destructive method is needed. Allometric equations that use one or more independent variable such as height, diameter and crown parameters have been widely used in estimating total biomass and its constituents (wood, leaf, fruits, seeds etc) of tree, shrub, and woody vines in various parts of the world. There are paucity of such allometric equations for herbaceous vines, especially of air potato that can be used to measure effectiveness of currently deployed management tactics. Herein, we measured four independent variables (patch area, patch height, number of stems arising from the ground and their base-diameters) of D. bulbifera patches in natural infestations ranging from southern to northcentral part of Florida, destructively harvested vines, sorted constituent parts (root, tuber, stem, leaf and aerial bulbils) as dependent variables and developed allometric equations that will allow prediction of dependent components and compare them for management effectiveness regardless of the size and stage (incipient or well-developed ) of infestation in its adventive ranges.