A HUGE tree-planting project aimed at creating an area of native woodland on a scale unseen in Scotland since the Middle Ages will be launched today.

The afforestation of an 8500 hectare area, twice the size of Dundee, will begin taking shape across the heart of Loch Lomond and the Trossachs National Park over the next 20 years.

This vision follows the lease by Scottish Water of its 9600hectare property around Loch Katrine and Loch Arklet to Forestry Commission Scotland. Lewis Macdonald, the forestry minister, will make the formal announcement at a ceremony at the loch today.

The commission has ambitious plans to begin restoring thousands of hectares of natural habitats around the loch over the next 10 to 20 years, including at least 2000 hectares of native woodland habitat.

This project, when added to neighbouring properties where there is similar restoration, will create the biggest continuous area of this habitat south of the Highlands, and Scotland's biggest native woodland, comprising mostly broad-leaved trees rather than conifers.

The other restorations are at RSPB Scotland's Inversnaid property and the Woodland Trust Scotland's Glen Finglas estate.

Together with other afforestation projects, the woodland across the five contiguous properties will form the 8500 hectares, stretching up the eastern shore of Loch Lomond and across the Trossachs, almost as far east as Callander.

The woodland at Loch Katrine will comprise mostly birch and Scots pine, with oak on the lower slopes near the loch, as well as hazel, rowan, alder, willow, juniper, ash, bird cherry and aspen, with montane scrub of woody shrub species and stunted forest trees in the harsher environment of the higher slopes.

The exact area to be restored at Loch Katrine will depend on talks between Scottish Water and the commission based on the catchment's hydrological yield (the amount of water that runs off the land into the loch).

This can vary according to the type of vegetation.

As well as planting, natural regeneration from existing woodland areas will be encouraged.

Planting will use local seed sources, and tree species will be matched to suitable sites.

Wildlife species expected to benefit and grow in numbers as a result of the restoration include birds such as black grouse, wood warbler, redstart, crossbill, red grouse, eagles, ospreys, short-eared owls and pied flycatcher, butterflies such as the purple hairstreak and pearl-bordered fritillary, and animals such as mountain hares.