BIOLOGICALLY BASED INTEGRATED MANAGEMENT OF WEEDS ON WESTERN RANGELAND WATERSHEDS
Location: Exotic and Invasive Weeds Research
Title: Biocontrol alters litter chemistry and short-term decomposition in a Tamarisk-invaded ecosystem
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: December 15, 2008
Publication Date: February 18, 2009
Citation: Uselman, S.M., Snyder, K.A., Blank, R.R., Jones, T.J. 2009. Biocontrol alters litter chemistry and short-term decomposition in a Tamarisk-invaded ecosystem [abstract]. In: 2009 Tamarisk and Russian Olive Research Conference, Reno, NV. p. 28-29.
The release of the leaf beetle (Diorhabda elongata) has resulted in the defoliation of tens of 1000’s of hectares of Tamarix-invaded systems, however little is known about the effects of biocontrol on ecosystem nutrient dynamics. Weed invasion has been linked to disturbance-induced increases in nutrient supply, thus changes to nutrient dynamics resulting from biocontrol may have implications for future plant community composition. Freshly senesced leaf litter of Tamarix ramosissima was collected in 2007 from trees affected by Diorhabda elongata herbivory, as well as from control trees at a site along the terminal end of the Truckee River, Nevada. Litter was analyzed for differences in initial chemistry, and then allowed to decompose in 1 mm mesh litterbags in the field for 6 months. Litter quality differed significantly in several characteristics frequently correlated with rates of decomposition, including % N, P, and lignin, and the ratios of C:N, C:P, Lignin:N, and Lignin:P, which suggests that beetle-affected litter should decompose more rapidly than control litter. Although the magnitude of the water-soluble fraction of the litter did not differ, the SUVA254 index of this component was higher for control versus beetle litter. The SUVA254 index indicates that the water-soluble fraction of the control litter is more aromatic than beetle litter, which suggests it would decompose more slowly than beetle litter. Furthermore, preliminary results of the decomposition experiment showed that beetle litter decomposed faster than control litter (P<0.001). After 6 months, the percent mass remaining of control litter was 78 ± 1%, versus 64 ± 1% for beetle litter. These results suggest that litter resulting from beetle herbivory has higher nutrient (N and P) content, and in combination with higher rates of litter decomposition, this may lead to changes in nutrient availability at these sites. As yet, it is unclear whether short-term changes in nutrient dynamics will translate to long-term changes in site fertility. It is important to understand the ecosystem-level effects of this biocontrol effort, because of the ramifications for the restoration potential of these degraded systems.