Computational protocol: Effects of Orientation on Survival and Growth of Small Fragments of the Invasive, Clonal Plant Alternanthera philoxeroides

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[…] On 11–14 December 2009, we counted numbers of nodes and leaves on each fragment; measured leaf area (WinFOLIA Pro 2004a, Regent Instruments, Inc., Québec, Canada) and length of new stolons; divided each fragment into roots, leaves, and new stolons; dried the portions at 70°C for 48 h; and weighed them. We did not include the stolon internodes left attached to fragments at the time of planting, because these stolon portions would necessarily differ in length and mass between stolon length treatments.For analyses, we first calculated the percent survival and the means for each of the measures of size of the surviving fragments in each container. To test effects of treatments on survival, we ran an ANOVA with orientation and initial stolon length as fixed effects. To test treatment effects on measures of growth, we ran a MANOVA with the same effects and with all of the five measures of growth as dependent variables. Separate ANOVAs of each measure, reported along with the MANOVA, were also conducted. Student-Newman-Keuls tests (with P = 0.05) were used to test for differences between each of the ten combinations of the orientation and stolon length treatments and between the five orientation treatments across stolon length treatments. Values of survival were transformed to the arcsine of the square root and values of leaf area to the square root before analysis to increase normality and reduce heterogeneity of variance. Analyses were conducted with SPSS 16.0 (SPSS, Chicago, IL, USA).We predicted (1) that survival and final size of fragments of A. philoxeroides would be greater when the angle of departure from the horizontal position was less and, for a given angle, when the distal end of the fragment was pointed upwards rather than downwards. We also predicted (2) that effects of orientation would be less when the length of attached stolon was greater. […]

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