Studies on the Population Biology of the Genus Viola: IV. Spatial Pattern of Ramets and Seedlings in Three Stoloniferous Species

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Abstract
The spatial pattern of demographic variables of ramets and seedlings in 16 populations of V. blanda, V. pallens and V. incognita were analyzed using a variety of approaches (area and distance methods, G-tests of heterogeneity based on area counts, neighborhood analysis and spatial autocorrelation). The variables considered were the position of ramets in space and time, emergence, and mortality of ramets and seedlings. Emergence of new seedlings is clumped in space. The seedlings tend to be more numerous in areas where the overall ramet density is low, indicating that seed germination or seedling emergence or both are inversely correlated with overall density of ramets. Seedling survival is affected by density. Ramets 1 yr old or older appear to be aggregated or randomly distributed in space. The pattern of emergence of new ramets from stolons and the pattern of ramet death is random in space and not density dependent. Apparently, seedling germination or survival or both are density dependent, but the pattern of adult ramet distribution, vegetative production of new ramets and ramet mortality is more sensitive to environmental variables such as light, water and nutrients which are known to be unevenly distributed on the forest floor. The concept of safe site for seed germination has little predictive value in these populations of Viola.

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