Clonal growth strategies in simultaneously persistent and expanding Trifolium repens patches

Plants with clonal growth can generate patches dominated by a single species. In time, patches can change and may fragment, form a ring, dissolve or both persist and expand. For patches to maintain their original habitat and simultaneously increase in size, ramets or clonal fragments must both promote local persistence inside the patch and grow out of the patch into new habitats. This study analyses simultaneously expanding and persistent Trifolium patches in a nutrient-poor lawn that is frequently cut, and where the Trifolium is competitively superior to the grass species. Trifolium primary stolon growth strategies were analyzed in relation to their location (border, middle, and center) inside the patch, and according to patch size (small, medium, and large). It was hypothesized that different growth strategies inside a patch can explain both persistent and expanding patch of Trifolium, and that growth strategies were different between patch sizes. Primary Trifolium stolons had two different growth strategies inside and at the border of patches: (i) stolons at the border were long, grew fast, had few lateral stolons, and grew out of the patch, while (ii) stolons inside the patch were smaller, grew slowly, and had more lateral stolons and a wide range of growth directions. Growth strategies were not different between patch sizes. The directional growth and the high growth rate at the border will increase the patch size with time, while the growth strategy near the center consolidates the patch in space and time, by placing ramets inside the patch. Different growth strategies near the center and on the border result in Trifolium patches that are simultaneously persistent and on the increase. The results also indicate a division of labor among primary Trifolium stolons in a patch.