Location: Invasive Species and Pollinator HealthTitle: Seasonal variation in growth, biomass and carbon storage allocation of Ludwigia hexapetala along water depth gradients in the Russian River Watershed [abstract]
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/3/2019
Publication Date: N/A
Technical Abstract: Seasonal growth and allocation of biomass and carbon storage reserves are fundamental aspects of plant competitiveness and invasiveness. Understanding variation of these factors across environmental gradients can inform development of effective management strategies by targeting weak points in weed life cycles. We evaluated seasonal growth, biomass and total nonstructural carbohydrate storage (TNC) of Ludwigia hexapetala and its variation with water depth at three contrasting river sites in the Russian River Watershed, California. The field study included five randomly located transects with biomass sampling through plant phenological stages for 18 months at four water depths (0, 25, 50, 100cm) at each site. Plant biomass core samples above and below the water surface, and root/rhizome samples from sediment were oven dried and weighed. Lower woody stem and below ground tissues were analyzed for TNC. Growth and biomass allocation varied with water depth and by site. In all cases, total live biomass was lowest in winter (semi-dormant stage), increased progressively through spring (pre-reproduction) and summer (flowering), with peak biomass attained in autumn (seed maturation and dispersal). Total biomass production was highest in shallow water, ranging from 1.5-6.8 ± 0.3 kg m-2 at 25 cm depth to 1.0-4.5 ± 0.2 kg m-2 at 50 cm depth in autumn. The percentage of total floating biomass where water was 25 cm deep increased from winter (9.7 ± 2.0 %) and spring (24.6 ± 4.4 %) to peak values in summer (43.6 ± 1.8 %) and autumn (45.2 ± 2.8 %). TNC reserves in lower woody stems and rhizomes varied by location and life stage, but in all cases were highest in fall - winter with depletion to lowest levels pre-reproductive and flowering stages. These results suggest targeted management actions at flowering stage when floating biomass exceeds submersed biomass could be most effective for foliar herbicide applications.