Monitoring Portsdown Hill
Ecological Surveys and Vegetation measurement
A great deal of biodiversity is small and requires an uncommon expertise to identify it. Most species of insect can only be named by an experienced entomologist, while an exhaustive survey takes both time and this esoteric knowledge. .
Historical survey on Portsdown
The biggest survey performed on Portsdown was in the 1970's, by David Appleton, Michael Bryant, Richard Dickson M.B, B.Chir., and George Else F.R.E.S.. They published a report in 1975 entitled "The Insects and Plants of Portsdown Hill", which formed the basis of all the species lists within this website. The report is type-written and duplicated, and a copy usually sits in the Portsdown Hill Countryside office at Fort Widley. Their lists have since been added to and subtracted from, as different species are found, and some have been lost.
Ongoing surveying on Portsdown
Whilst it is important to know what there is and how well it is doing, often the best that can be done is to monitor changes in the vegetation and the more easily identified (and counted) invertebrates, such as butterflies. Records from visiting experts are always welcome.
In managing the site, it is important that changes in the abundance and distribution of certain species are noted. The site is being changed and the response of the local ecosystem must be monitored. Much of the scrub is being removed and grassland encouraged to replace it. Many of the species we want to encourage thrive on particular lengths of grass, such as the Adonis Blue butterfly (last seen in the 1960s), which requires very short, closely-cropped grass.
To monitor the effects of grazing, grass length and density is measured before
and after grazing.
Quadrat data from the grassland is also gathered and used to monitor changes in the distribution and abundance of plant species.
Students from the local University of Portsmouth often carry out their project work on the hill, which is always encouraged.
Grass survey
During grass measurement, an A4 board with a hole is used, the grassland 'densiometer'.
10 throws of this board, with several replicates, within each location are made and measurements are taken:
The height is the maximum length of the longest grass leaf at each board drop.
The density is the resting-height of the board above the ground, which gives an indication of the height of sufficient thickness of grass to support the board's weight. As the same board is used for every survey, this allows comparisons between sites and over years
Butterfly conservation
Voluntary surveyors from the SE Hants Butterfly Conservation Group have been monitoring, (through butterfly transects) the decline of Portsdown's butterfly population for many years and very kindly have continued monitoring its restoration.They conduct a transect to the south of Fort Southwick. Volunteers with the Countryside Service carry out a transect south of Fort Widley.
Visiting wildlfe enthusiasts
The rich array of insects and other wildlife attracts natural historians to Portsdown. Many pass on their findings which are usually illustrated by photographs. Some of their pictures appear in the Life pages.