Background
Established in 1969, the Lena Ward plots are in CG2 grassland at Aston Rowant NNR. This experiment was established to investigate scrub development on chalk and how burning or rotavating chalk grassland prior to scrub development affects the subsequent diversity of the scrub.
Design
There were four initial treatments; untreated (control), burnt, rotavated and grazed, on plots each measuring 10 x 12m. Each randomised block was replicated four times with two blocks on Beacon Hill and two on Linky Down. All treatments except the grazed plots were fenced against sheep and rabbits.
Sampling
Sampling was undertaken annually from 1969-2005 and in 2007. The positions of 3-4000 seedlings were recorded as they invaded, whilst plant communities, vegetation height and light infiltration were also monitored. The vegetation in two permanent quadrats in each plot was recorded each year on the Domin scale.
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Sampling continued...
Each plot was re-sampled in 2013 with the positions of each shrub or tree with a diameter at breast height (dbh) > 40 mm recorded along with the dbh of each stem. All the yew stems reaching breast height were plotted and their dbh was measured. It will prove possible to relate the current positions of many plants to the positions and order of colonisation of seedlings in 1969-99.
Results
Hawthorn seedlings are usual constituents of chalk grassland, kept in check by grazing. If grazing was abandoned, these hawthorn seedlings would quickly establish. The resulting scrub would be less diverse than if the seedlings had first been removed by burning or rotavation.
Preliminary investigations into the numbers of large shrubs of each species suggests that treatments have no statistically significant effects on overall species richness or diversity. Burning or rotavation significantly reduce the numbers of hawthorn plants compared to merely removing grazing. In the ungrazed plots, yew invasion and growth is retarded.
