Rare Chalk Grassland Takes 50 Years To Recover From Military Use

Working with historical aerial photographs taken on the Salisbury Plain Training Area between 1945 and 1995, Dr Rachel Hirst and colleagues from the Centre for Ecology and Hydrology and the University of Liverpool identified 82 sites from which they sampled vegetation and soil. They found that, while neutral (mesotrophic) grasslands took between 30 and 40 years to re-establish after disturbance during military training, areas of chalk grassland took at least 50 years to recover.

The long-lasting damage is due not only to vegetation being destroyed by tanks and shelling but also by soil compaction. According to Hirst: "Large military vehicles can change the horizontal and vertical structure of vegetation communities through the crushing and cutting of vegetation, and soil compaction effects decrease soil microporosity and rainfall infiltration capacity, altering nutrient availability and restricting root growth."

Covering 38,000 hectares, Salisbury Plain Training Area is the largest military training area in the UK, and the only training area suitable for large-scale tactical armoured vehicle exercises. However, it is also one of the largest Sites of Special Scientific Interest (SSSI) in the UK, containing the largest expanse of unimproved chalk grassland in north-west Europe - a habitat of particular conservation interest.

The findings not only have implications for how the Ministry of Defence manages the more than 250 SSSIs in its training areas, but also how much pressure certain areas of the countryside can bear from the increasing use of off-road vehicles.

"Chalk grasslands remain a rare and fragmented habitat type in north-west Europe, and outside Salisbury Plain, the rolling chalk downlands of southern England, much of which enjoy statutory protection, provide recreational resources for walking, horse riding and cycling. These activities cannot take place without some localised habitat disturbance, but can be managed more effectively if the ecosystem dynamics are better understood. Appreciation of the length of time that intensively disturbed grassland can take to re-establish may encourage more effective control measures at other sites," Hirst says.