1. How can Trifolium repens patches simultaneously expand and persist?
Line Johansen
Norwegian Institute for Agricultural and Environmental Research,
Grassland and Landscape Division, Kvithamar, Norway
Introduction
Clonal plants can generate patches dominated by a single species. In time, patches can change and may fragment, form a ring, dissolve or expand. The aim of the study was to quantify growth strategies that can explain simultaneously persistent and expanding T. repens patches.
Methods
T. repens patches were studied in a nutrient-poor lawn that was frequently cut. The following variables were measured on primary stolons: stolon length, stolon growth, growth direction and number of lateral stolons. The growth strategies were related to location inside the patch (centre, middle and border zone) and the patch size.
Results
Growth strategies were different between location inside the patch (zone type), but not between patch sizes. The results indicated two growth strategies:
Border strategies: primary stolons long (df = 2, P < 0.001), grew fast (df = 2, P < 0.001) (figure 1), had few lateral stolons (df = 2, P = 0.03) and grew out of the patch (df = 8, P < 0.001).
Strategies inside the patch: primary stolons were small, grew slowly, and had more lateral stolons and a wide range of growth directions.
Figure 1. Mean and SD for a) stolon growth (mm) during 9 weeks and b) stolon length of Trifolium repens primary stolons in different patch zone types. Bars with different letters are significantly different (P > 0.05).
Conclusions
The directional growth and the high growth rate at the border will increase the patch size with time, while the growth strategy near the centre consolidates the patch in space and time, by placing ramets inside the patch. These two growth strategies together result in T. repens patches that are simultaneously persistent and on the increase.