Title: A Simple Relationship Between Short- and Long-term Seed Predation Rates Authors
|Westerman, Paula -|
Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: September 21, 2009
Publication Date: February 11, 2010
Citation: Davis, A.S., Westerman, P.R. 2010. A Simple Relationship Between Short- and Long-term Seed Predation Rates. Weed Science Society of America Meeting Abstracts. 49:148. Technical Abstract: Weed seed predation is an important ecosystem service supporting weed management in low-external-input agroecosystems. For convenience, measurements of seed predation are often made at very short time scales (< 3 d). However, one of the primary uses of such data, the parameterization of models of cropping system management on weed population dynamics, requires estimates of weed seed predation at seasonal or annual time scales. The relationship between short- and long-term point estimates of seed predation has not previously been characterized, hindering weed modeling efforts. In order to quantify this relationship, a field study was made within a maize crop in central Illinois, USA, in 2005 and 2006. From late July through mid-October, weekly short-term measurements were made of Abutilon theophrasti, Ambrosia trifida, and Setaria faberi seed removal rates over 48 hr by invertebrate and vertebrate granivores. Next to each short-term predation arena, long term predation rates were also measured by adding seeds weekly in long-term arenas, but not recovering the seeds until the entire study period had elapsed. Short term predation rates were then used to predict long-term predation rates by two methods: 1) compounding short term predation rates over the study period, and 2) dividing the total number of seeds eaten over the study period by the total number of seeds added. Mixed-effects analysis of covariance indicated that method 2 provided a robust means of estimating long term predation rates from short term predation rates for all species and site-years (R2 = 0.74, p<0.001). Moreover, resampling analyses of 96 experimental units consisting of seed predation point estimates across all weekly sampling periods indicated that replication could be reduced by 90% without distorting the fundamental relationship between short and long-term estimates of seed predation. Future applications of this method should permit accurate estimates of long-term seed predation rates in agroecosystems with minimal sampling effort.