ARS | Publication request: Impacts of insect biological control on soil N transformations in Tamarix-invaded ecosystems in the Great Basin

Submitted to: Western Society of Weed Science
Publication Type: Proceedings
Publication Acceptance Date: December 13, 2011
Publication Date: July 3, 2012
Citation: Uselman, S.M., Snyder, K.A., Blank, R.R. 2012. Impacts of insect biological control on soil N transformations in Tamarix-invaded ecosystems in the Great Basin. Proceedings of Western Society of Weed Science. 65:55.

Technical Abstract: Understanding the impacts of insect biological control of Tamarix spp. on soil nitrogen (N) transformations is important because changes to N supply could alter plant community succession. We investigated short-term and longer-term impacts of herbivory by the northern tamarisk beetle (Diorhabda carinulata) on soil N availability in Tamarix-invaded ecosystems by surveying soils (organic horizon and mineral soil, 0-10 cm) from three sites and assaying for potential net N mineralization using laboratory incubations as an index of soil N availability. Results partially supported our hypothesis that beetle herbivory would result in stimulated rates of net N mineralization in the short-term (i.e. in the first year of exposure to herbivory), and did not support our hypothesis that beetle herbivory would result in a sustained increase in net N mineralization rates in the longer-term (i.e. after several years of exposure). Short-term effects of herbivory differed by site, and were likely influenced by differences in the prevailing soil N status. In the longer-term, there was no impact on overall net N mineralization rates, even though there was a trend towards greater N immobilization in the mineral soil with more years of herbivory. This trend in the mineral soil may be attributable to declining organic matter inputs to soil due to progressive growth limitation from herbivore-induced stress. These results suggest that soil N availability will increase in the short-term and eventually decrease in the longer-term at low fertility sites, while soil N availability will not be impacted by beetle herbivory at high fertility sites.