l he extent to which such small-scale abiotic heterogeneity influences population structure and individual fitness was investigated by Han- gerink and Bazzaz 1984 in a greenhouse experiment on the annual herb AlmtiUn thfepbrntfi Malsaceae . Heterogeneity was created at three densities in experimental plots by either adding nutrients sand or stones or by compacting the soil in seedling-sized patches. Single seedlings were grown in each of the patch types. Seedling populations were also grown in the coach handbagssame spatial arrangement in discount coach bagsplots in which every effort was made to eliminate mkrohalsitat heterogeneity. Several aspects coach pursesof performance were measured for the seedling and adult plants in each treatment. The effects of density and pitch type on seedling masses are show n in Fig. 11.14. Both density and coach outletthe interaction of patch type with presence or absence of heterogeneity had a significant effect on plant mass; the pattern of response to coach outlet storesdifferent types of patch in the heteroge¬neous treatment was significantly different from that of plants in the same locations but in homogeneous environments Seed production varied significantly with the type of patch in which the plants were grown. Much of the variance 47-62% depending on density in seedling coach bagsheight after 2 days of growih could be explained by patch type differences but as growth proceeded the level of coach handbagsexplanation due to pitch type fell reaching 20-2S% at the final harvest One-third of the variance in individual mass at final harvest was attributable to differences in patch type. Overall at final harvest 58-76% of the variance in plant maxs depending on density could be explained by a multiple regression in which most of the explained variance was due to patch type and seedling size early in growih In contrast to the experiments cued in section 11.2.1 individual plant sizes were nd correlated with the sizes of discount coach bagstheir immediate neighbours coach outletsee also Fowler IV84 . University of Chicago Press. 2000 - Science -181 pages