Experiment 1: 4 Amaranthaceae species & Glycine max • The study was conducted at the following field sites in southern Illinois: Cypress Creek National Wildlife Refuge (A. japonica), Chestnut Hills Nature Preserve (A. japonica), Belleville Research Center (A. palmeri, A. tuberculatus, G. max), and Beall Woods State Park (I. rhizomatosa). • Ten individual plants of each species at each site were randomly selected for measurements (see Sampling Method above). • Differences among wavelengths in % reduction taking into account plant height as a covariate were tested using an ANCOVA in SAS. Experiment 2: Achyranthes japonica in competition with Microstegium vimineum • The field site was located at Chestnut Hills Nature Preserve in Pulaski County, Olmsted, Illinois. • Twenty 1m2 quadrats containing mixed communities of A. japonica and M. vimineum with different proportions of A. japonica were sampled three times (T1, T2, T3) during July. • Vegetation was sampled by visually estimating plant cover in each 1m2 quadrat based upon the modified Daubenmire method for cover estimation. • Four individual plants within each plot were randomly selected for measurements (see Sampling Method above). • The relationship between the proportion of A. japonica and height to the mean % reduction of each light wavelength was examined using a stepwise regression in SAS. Introduction Materials and Methods Experiment 1 • All five species had significant differences between light wavelengths (Fig. 1). • The mean % reduction of the blue wavelength was consistently the highest among the four wavelengths, nearing 100%, followed by the red and far-red wavelengths, respectively (Fig. 1). • The far-red and white wavelengths had similar levels of reduction at approximately 44% in A. japonica at Cypress Creek and 59% in I. rhizomatosa, (Fig. 1a, e), while A. japonica at Chestnut Hills had a greater reduction in the white than far-red wavelength (Fig. 1b). Experiment 2 • There was a positive relationship between the mean % reduction in both the blue and red wavelengths and height for T1 and T3 (Fig. 2a, c). • There was a negative relationship between the mean % reduction in the far-red wavelength and the proportion of A. japonica for T1 (Fig. 2b). • There was a positive relationship between the red:far-red ratio and height for T1 and T2 (Fig. 2d). • There was a negative relationship between the mean % reduction of red wavelength and the proportion of A. japonica and a positive relationship with height for T2(Fig. 2e). • There were no significant relationships detected for the white wavelength. a) Blue Wavelength (Height) Height (cm) 20 30 40 50 60 70 80 90 100 Mean % Reduction 96.0 96.5 97.0 97.5 98.0 98.5 99.0 99.5 100.0 Time 1: blue = 97.666 + 0.01798 (height) F1,18 = 8.44, p = 0.0094, R2 = 0.3192 Time 3: blue = 97.744 + 0.01443 (height) F1,18 = 5.16, p = 0.0356, R2 = 0.2229 40 50 60 70 80 90 100 40 50 60 70 80 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 Mean % Reduction Height (%) Proportion of Achyranthes japonica e) Red Wavelength (Height & Proportion of Achyranthes japonica) 40% 50% 60% 70% 80% 90% 100% Time 1 Time 1 Regression Time 2 Time 2 Regression Time 3 Time 3 Regression c) Red Wavelength (Height) Height (cm) 20 30 40 50 60 70 80 90 100 Mean % Reduction 40 50 60 70 80 90 Time 1: red = 44.248 + 0.44211 (height) F1,18 = 11.35, p = 0.0034, R2 = 0.3868 Time 2: red = 60.15926 - 9.66842 (propachj) + 0.34795 (height) F2,17 = 9.8; p = 0.0015; R2 = 0.5354 Time 3: red = 56.29869 + 0.25306 (height) F1,18= 11.79, p = 0.0030, R2 = 0.3958 b) Far-Red Wavelength (Proportion of Achyranthes japonica) Proportion of Achyranthes japonica 0.2 0.4 0.6 0.8 1.0 Mean % Reduction 35 40 45 50 55 60 65 70 Time 1: far-red = 53.72696 - 9.15980 (propachj) F1,18 = 6.00, p = 0.0248, R2 = 0.2501 d) Red:Far-Red Ratio (Height) Height (cm) 20 30 40 50 60 70 80 90 100 Red:Far-Red Ratio 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 Time 1: ratio = 0.85063 + 0.01217 (height) F1,18 = 7.63, p = 0.0128, R2 =