|Raghu, Sathyamurthy -|
Submitted to: Weed Research
Publication Type: Proceedings
Publication Acceptance Date: December 4, 2009
Publication Date: December 1, 2010
Citation: Davis, A.S., Raghu, S. 2010. Weighing Abiotic and Biotic Influences on Weed Seed Predation Rates. Weed Research. 50:402-412. Technical Abstract: Weed seed predation is an important ecosystem service supporting weed management in low-external-input agroecosystems. Current knowledge of weed seed predation focuses on biotic mechanisms, with less understood about the relative impact of abiotic variables. In order to quantify relative contributions of abiotic and biotic variables to weed seed predation rates, a field study was made within a maize crop in central Illinois, USA, in 2005 and 2006. From late July through mid-October, weekly measurements were made of Abutilon theophrasti, Ambrosia trifida, and Setaria faberi seed removal rates by invertebrate and vertebrate granivores, and seed losses due to abiotic processes. Weed seed rain was measured concurrently in contiguous plots, as were air temperature, precipitation, wind speed, thermal units and invertebrate activity-density. Structural equation models of weed seed predation by invertebrates and vertebrates indicated that the relationship between seed supply and predator seed demand drove much of the variation in seed predation rates. When latent variables for abiotic seed losses and climatic variables associated with winter's approach were included in these models, their explanatory power and parsimony both declined. A mechanistic understanding of predator satiation will help guide agroecosystem design to increase weed seed destruction by granivores.