Background information and definitions
Spreading clippings may help to increase the colonization of shrubland plants as a result of introducing seed. Plant clippings may also help to increase organic material in the soil.
Supporting evidence from individual studies
A randomized, controlled study in 1988–1993 in Dorset, UK (Pywell et al. 1995) found that the addition of shoots and seeds of heathland plants increased the number of seedlings for two of seven species, increased the abundance of mature plants for one of six species, but did not increase abundance of mature plants for three of six species. For two of seven heathland species the number of seedlings in plots where the shoots and seeds of heathland species were spread (14–30 seedlings/m2) was higher than in plots where the shoots and seeds of heathland species were not spread (0 seedlings/m2). The abundance of one of six heathland plant species was higher where shoots and seeds of heathland species had been spread (8.5 shoots/m2) compared to plots where shoots and seeds were not spread (0.2 shoots/m2). However, there was no significant difference in the abundance of four of six heathland plant species where heathland shoots and seeds had been spread (0–3.9 shoots/m2) when compared to areas where they were not spread (0–3.9 shoots/m2). In December 1988 shoots of heathland species were harvested from a mature heathland. In three 500 m2 plots soil was disturbed using a rotary cultivator and shoots spread at a rate of 3 kg/m2, three other plots were disturbed but had no shoots spread. In 1990–1991 the number of seedlings was recorded in seven 0.5 m x 1 m quadrats in each plot. In 1993 the number of plant shoots was recorded in three 1 m2 quadrats which were randomly placed in each plot.Study and other actions tested
A randomized, controlled study between 1991 and 2004 in a former pine plantation in Kent, UK (3) found that 12 years after spreading heather Calluna vulgaris clippings the frequency of heather plants was the same as in areas where clippings were not spread. After 12 years there was no significant difference in the frequency of heather between areas where heather clippings were added (heather present in 95% of plots) and areas where clippings were not added (heather present in 99% of plots). Four blocks consisting of two 25 m2 plots were established. In one plot leaf litter was removed and in the other leaf litter was removed and heather clippings added. In each plot ten 0.25 m2 quadrats were placed and used to record frequency of heather plants.Study and other actions tested
A replicated, randomized, controlled study in 1989–1991 in one abandoned mineral quarry and one abandoned farmland site in Dorset, UK (2) found that spreading clippings from intact heathlands increased the density of heather Calluna vulgaris and Erica spp. seedlings, but did not increase the density of other heathland species. After two years, there were more heather seedlings in plots where clippings were spread (38–224 seedlings/m2) than in plots where no clippings were spread (0–2 seedlings/m2). The density of other heathland species (Ulex minor, Molinia caerulea, and Agrostis curtisii) did not differ significantly between plots were clippings were spread (31 seedlings/m2) and plots where no clippings were spread (1 seedling/m2). In 1990 at the quarry site nine 30 m2 plots were rotovated and clippings spread on the soil surface, while four plots were left unrotovated and no clippings were spread. At the abandoned farmland site in 1990 three 500 m2 plots were rotovated and clippings spread, while three plots were left unrotovated and no clippings spread. In 1991 the density of plants was recorded in twenty 0.3 m2 quadrats/plot at the quarry site and in seven 0.25 m2 quadrats/plot in the farmland site.Study and other actions tested
A replicated, randomized, controlled study between 2007 and 2011 in a karoo shrubland in Richtersveld, South Africa (4) found that spreading branches of the shrub Brownanthus pseudoschlichtianus on overgrazed plots did not increase plant cover or the number of plant species. After three years, plant cover of areas where shrub branches were spread (3%) did not differ significantly from areas where branches were not spread (4%). Similarly, the number of plant species in areas where shrub branches were spread (6 species) did not differ significantly from areas where branches were not spread (7 species). Five 1 ha blocks were divided using a fence to exclude cattle. In each block branches from B. pseudoschlichtianus were spread in one 10 m x 10 m plot while another plot was left with no branches spread. Vegetation in each 10 m x 10 m plot was assessed annually between 2008 and 2011.Study and other actions tested