Modeling the long-term effect of bio-control on the spread of an invasive tree: melaleuca

Transcription

1 Modeling the long-term effect of bio-control on the spread of an invasive tree: melaleuca Bo Zhang 1, Don DeAngelis 2, Min Rayamajhi 3 1. University of Miami 2. United States Geological Survey 3. USDA Invasive Plant Research Laboratory

2 Melaleuca quinquenervia

3 Current problem The value of services provided by wetlands: $14,785 per hectare. The lost value arising from current melaleuca infestations: nearly $30 million per year. Bio-control offers the best hope.

4 Bio-control 1997: Australian weevil (Oxyops vitiosa); Dr. Min B. Rayamajhi 2002: Melaleuca psyllid (Boreioglycaspis melaleucae Moore). 3.3 million individual biological control agents 407 locations 15 Florida counties

5 Effects of bio-control Rayachhetry et al, 2001 Center et al, 2000 L. Sevillano and C. C. Horvitz

6 83% decrease of growth rate How will melaleuca respond? Can melaleuca tolerate? L. Sevillano and C. C. Horvitz

7 Objective1: To test a hypothesis Trees can change their strategies of allocating carbon and nutrient, to maintain a high growth rate. (Give more carbon to foliage) The trade-off in investment between root and shoot (foliage).

8 Method: Process modeling Nutrient uptake Photosynthesis - carbon Allocation: foliage, wood and root ηfoliage + ηwood + ηroot = 1 Goal: maximize growth rate The model is based on the G DAY model of Comins and McMurtrie (1993), which was further developed by Ju (2008). Optimal allocation strategy???

9 Growth rate Optimal allocation strategy ηwood = 0.4 ηfoliage + ηroot = 0.6 Maximum G No Bio-control Optimal allocation strategy Fraction carbon allocated to foliage

10 Growth rate Growth rate decreased with stronger biocontrol; Melaleuca tended to allocate more carbon to foliage, especially with stronger biocontrol. G Maximum G (A) Optimal allocation strategy (C) No Bio-control Low Bio-control High Bio-control Fraction carbon allocated to foliage

11 Maximum Growth rate Soil nutrient level matters Low soil nutrient Tree died Defoliation rate / year

12 Maximum Growth rate Maximum Growth rate is higher in rich soil, at the same level of defoliation; Melaleuca can tolerate stronger bio-control in rich soil. G (A) High soil nutrient High soil nutrient 1 Low soil nutrient (C) Defoliation rate / year

13 Objective2: Use an individual based model to help understand: How melaleuca invades in two habitats. Cypress swamps and Bay swamps How bio-control influences melaleuca s invasion. How native species will respond over the longer term as a result of bio-control of melaleuca. Zhang et al. in press Landscape Ecology

14 Individual based model: JABOWA JABOWA simulates plant succession in a 0.01 hectare plot, characteristic of plants and environmental conditions. Slash pine (Pinuselliottii); Pond cypress (Taxodiumascendens); Dahoon holly (Ilexcassine); Sweet bay (Laurusnobilis); Loblolly bay (Gordonialasianthus )*; Melaleuca (Melaleucaquinquenervia) Dr. Daniel Botkin *This is rare in south Florida, but growth data were available Zhang et al. in press Landscape Ecology

15 Inputs a set of plot data: estimate site quality Direct competition: light Introduces new saplings to stand Kills some trees from stand Grows the remaining stand Reproduction Zhang et al. in press Landscape Ecology

16 Inputs a set of plot data: estimate site quality Introduces new saplings to stand Elevation, soil depth, soil moisture, nutrient, temperature, precipitation maximum reproduction rate Kills some trees from stand maximum age Grows the remaining stand maximum growth rate Zhang et al. in press Landscape Ecology

17 The basal area of native species with melaleuca in Cypress swamps without bio-control Pond cypress slash pine 40% Melaleuca pond cypress 57% Slash pine Zhang et al. in press Landscape Ecology

18 The basal area of native species with melaleuca in Cypress swamps without and with bio-control Pond cypress Melaleuca Slash pine Zhang et al. in press Landscape Ecology

19 The basal area of native species with melaleuca in Bay swamps without bio-control Melaleuca Pond cypress loblolly bay 57% sweet bay 35% Loblolly bay Zhang et al. in press Landscape Ecology

20 The basal area of native species with melaleuca in Bay swamps without and with bio-control Melaleuca Pond cypress Loblolly bay Zhang et al. in press Landscape Ecology

21 But this is not always the case.. Sensitivity analysis Non-efficiency bio-control agent Zhang et al. in press Landscape Ecology

22 Conclusions Bio-control decreased the invasion of melaleuca. With bio-control, native species can recover back to the habitat. Re-allocating more carbon to foliage helped compensate for the losses to bio-control, therefore, it is important to have a strong and efficiency biocontrol agent. (This work is being extended by working with others to the whole south Florida region using USGS dispersal models).

23 Funding Resources USGS s Greater Everglades Priority Ecosystem Science funding.