VIEWS: 8 PAGES: 21 POSTED ON: 8/25/2011
Does water hyacinth (Eichhornia crassipes) compensate to defoliation? Implications for compensate to defoliation? Implications for effective biocontrol Pushpa G. Soti and John C. Volin Florida Atlantic University University of Connecticut Water Hyacinth Worldwide Distribution: Tropical Worldwide Distribution: Tropical and subtropical regions worldwide, native to Amazon basin US Distribution: Gulf coast states, Florida, Georgia, South Carolina, Sacramento River Delta (California) Ecological: reduces DO, outcompetes native species, loss of water (high transpiration), etc. Economic Importance: Most important nuisance aquatic plant worldwide, and in US ($5M/yr in Florida), impacts fishing, recreation, p g provides mosquito breeding habitat, etc. Control of Water Hyacinth Biological Control Seven species introduced around the World •Seven species introduced around the World •Most effective are the Neochetina weevils •Not as effective as expected in Florida interference with other management -interference with other management practices -high growth rate of plant plant regulation (bottom up control) -plant regulation (bottom‐up control) -plant compensation or http://www.saj.usace.army.mil/Divisions/Operations/Branches/InvSpecies/Imag es/ControlMethods/biocontrol_NeochetinaEichhorniae_collage.jpg overcompensation Grazing Optimization Hypothesis Grazing Optimization Hypothesis Objective and Hypotheses We investigated whether the high amount of nutrient availability, as found in the canals of southern Florida, is facilitating water hyacinth plants to either compensate or overcompensate in growth h i th l t t ith t t i th to a low level of chronic simulated herbivory. (1) under high nutrient conditions water hyacinth would ( ) h h h h l overcompensate for low levels (i.e., 10%) of continuous simulated herbivory; (2) under low nutrient conditions compensation for low defoliation would be muted but sufficient to result in no difference in growth between the defoliated and control plants; and (3) that high defoliation (80%) would be too great for p g y compensation to occur regardless of nutrient level and thereby result in the lowest overall growth rates. Hypotheses Treatments High and Low Nutrients (50.5 mg l‐1 N, 2.56 mg l‐1 P; (50.5 mg l N, 2.56 mg l 5.5 mg l‐1 N, 0.20 mg l‐1 P) 3 Defoliation Levels (0, 10 and 80%) 3 Defoliation Levels (0, 10 and 80%) 12 mesocosms (100 L) (n=6) Growth Measurements ( ) Relative Growth Rate (RGR) RGR = [ln(final mass) – ln(initial mass)]/time Allocational: LMR=leaf mass/plant mass SMR=stem mass/plant mass StMR=stolon mass/plant mass StMR stolon mass/plant mass RMR=root mass/plant mass FMR=flower mass/plant mass Morphological: SLA=leaf area /leaf mass Physiological: Photosynthesis y Harvesting Photos synthesis ( 1 mol m2 s‐1) cm Specific Leaf Area (c 2 g‐1) 100 150 200 250 0 50 High nutrient Low nutrient y = 2E‐06x + 0.0472 R² = 0.9245 0.09 0.08 0.07 0.06 RGR 0.05 0.04 0.03 0.02 0.01 0 0 2000 4000 6000 8000 10000 12000 14000 SLA*PS l 1 1 Mass‐based Photosynthesis (nmol g‐1 s‐1) M b d Ph t th i ( Summary • No overcompensation occurred in the 10% defoliated plants in high nutrients (first hypothesis d f li d l i hi h i ( not supported) d f li d l d f ll i l • 10% defoliated plants compensated fully in low nutrient concentration (second hypothesis supported) supported) • Lowest growth rate occurred in the 80% defoliated plants but still maintained fairly high defoliated plants but still maintained fairly high growth rate (third hypothesis supported) Soti and Volin 2010 (Biological Control) Summary Summary Water hyacinth can switch its biomass allocation • Water hyacinth can switch its biomass allocation strategy depending on the stress – Allocates more to roots in low nutrient conditions – Allocates more to seed production in low nutrient conditions (seeds can remain dormant 15‐20 years) – Allocates more to asexual reproduction in high nutrients Considerations for Restoration Considerations for Restoration • Water hyacinth appears to fully compensate for low levels of continuous defoliation in high and l l l f ti d f li ti i hi h d low nutrient levels - Lowering nutrients or removing significant y amounts of leaf biomass is likely insufficient for water hyacinth control – although both need to be used as management tools - Evaluation of biocontrol efficacy is arguably the most important phase of biocontrol Questions? Q i ?
Pages to are hidden for
"Does water hyacinth _Eichhornia crassipes_ compensate to "Please download to view full document