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biodiversity
Changes in Plant Diversity: 1990-1998
Mean number of vascular 5 plant species recorded
| 1990 | 1998 | % change |
|---|
Per 1km square | 70.5 | 70.1 | - 0.6* |
|---|
Plots in acid grassland | 15.4 | 16.5 | 6.9* |
|---|
Plots in dwarf shrub heath | 14.4 | 13.4 | - 6.6* |
|---|
(*statistically significant, P<0.05)
Plant species diversity is one measure of botanical composition that can provide an indication of changes in habitat quality. Changes are often associated with land management and atmospheric pollution. Effects of climate change may become evident in the future.
The Countryside Survey 2000 6 reported changes between surveys in 1990 and 1998 of 193 1km sample squares. Plant diversity, in terms of the number of vascular plant species recorded, was estimated from plots placed within each square.
No overall change was detected in the mean number of plant species recorded per square (a decline of 0.6% was not statistically significant). There were no significant changes within most broad habitats, including the arable and horticultural broad habitat, which is subject to a high degree of year-on-year disturbance. Significant changes in plant diversity were observed only in acid grassland and dwarf shrub heath.
An estimated 6.9% increase in plant diversity in acid grassland was in part due to an increased abundance of plant species associated with less acid conditions. An estimated 6.6% decrease in the species richness of dwarf shrub heath was associated with a decline in the prevalence of stress-tolerant plant species associated with low-nutrient conditions. This was partly offset by an increase in competitor plant species, which tend to benefit from heavy grazing or nutrient enrichment.
SOURCE: COUNTRYSIDE SURVEY 2000, SCOTTISH NATURAL HERITAGE
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