Dynamics of Seed Populations of Rumex crispus and Rumex obtusifolius (Polygonaceae) in Disturbed and Undisturbed Soil

Abstract

Two perennial colonizing species of Rumex were studied in a series of experiments. Seed longevity, germination from various soil depths, and germination in disturbed areas of various sizes were measured. The percentage germination of achenes of both R. crispus and R. obtusifolius was reduced after burial; even burial at a depth of 1.0 cm significantly reduced germination. The effect was greater for R. crispus than for R. obtusifolius. The percentage emergence of both species in the field, was less when large patches (625 cm2) were disturbed than when small patches (25 or 100 cm2) were disturbed, but was not affected by sowing densities of 1-4/cm2. In contrast, the number of seedlings surviving over winter was related more to patch size than to sowing density, and was greatest at the largest patch size. Similar numbers of seedlings of the 2 spp. emerged during the first 18 mo. but more achenes of R. crispus than of R. obtusifolius remained viable after being sown on the soil surface. Soil disturbance during the year following sowing did not significantly affect the number of viable seeds remaining in the soil. The results are discussed in relation to the dynamics of seed populations in disturbed and undisturbed soil.