rich colours of autumn had arrived on the River Findhorn. Even on this dull, overcast day, Nature was doing her level best to impress - far more subtle and no less effective than the garish garb of a group of canoeists shooting the rapids created by recent heavy rain.

Steve Conolly, forest manager for the Cawdor estate, and John Parrott of Scottish Native Woods, an Aberfeldy-based charity concerned with the regeneration of native woodland, examine the extent of new tree growth high on an eroded section of the river bank.

Sure enough, they find plenty of evidence that miniature birch trees are sprouting in abundance, left alone to flourish now the sheep have disappeared from this part of the estate. It's just what they want to see, and although birch is far and away the dominant species, in the space of a few hundred metres they also identify oak, elm, aspen, alder, bird cherry, and more.

Cawdor estate has been in the Cawdor family for 650 years and covers a huge area from the Moray Firth in the north to Carrbridge in the south. The River Findhorn runs through the property and Drynachan is a magnificent 12km long stretch bounded by grouse moor and the remnants of more extensive birch woodlands. Its significance for the estate lies in income from the fishing rights.

The privilege of catching fish here is not cheap, with a two-rod beat for a week costing around #1500. Nevertheless, there are those prepared to pay the price. ``There are one or two clients who take a large number of weeks throughout the year,'' says Conolly.

Fishing is always unpredictable, of course, but having shelled out such a large amount, clients expect a good chance of a catch. The problem is that fish stocks here, and on other Scottish rivers, have been diminishing. In recent years, salmon and sea trout have dwindled to their lowest level on record, with many rivers reporting less than 50% of the catches recorded 45 years ago.

Enter Scottish Native Woods with an explanation and a solution to the dilemma. ``The estate had been faced with fish stocks getting perilously low,'' says Parrott, ``and one of the reasons for that was the decline in habitat for the fish.''

Highland River Purification Board had done a survey of the Findhorn and concluded that reintroducing tree cover was essential if fish stocks were going to improve.

There are several ways in which riverside, or riparian, woodlands contribute directly to the productivity of fresh waters. To begin with, the trees provide a valuable food source for fish. Insects fall from the leafy canopy into the water, while leaf litter contributes to the food chain.

Tree root systems stabilise the river banks, preventing erosion and the silting-up of river beds and spawning grounds. The roots also offer shelter to young fish and the leaf canopy provides shade. It's an intricate ecological interdependence which had deteriorated badly along the Findhorn.

Estate factor Gordon Robertson met Parrott at Moy game fair, and asked him to survey the woodland at Drynachan. He did so, and in 1994, with grants from the Forestry Authority's Woodland Grant Scheme, a project was set in motion to improve the broadleaf tree cover on the river banks.

To allow regeneration to begin, sheep roaming freely along the riverside, constantly nibbling away at shoots of infant trees, had to be removed. By mutual agreement with the estate, the tenant farmer was bought out and his stock, numbering around 2500 sheep, was sold.

Extensive and unsightly fencing usually has to be erected in this situation to prevent sheep from neighbouring tenancies getting on to the ground. At Drynachan, however, because of the sheer size of the Cawdor estate, this has not been necessary.

``As far as we are concerned this is something of a showpiece scheme for Scottish Native Woods,'' says Parrott. ``It's the biggest scheme I have been involved in, with 500 acres of woodland and a lot of ground in between.'' After two years without grazing sheep, the evidence is already there.

Apart from the commercial benefit to the estate through the improvement of fish stocks, aesthetic benefits will flow from increased broadleaved tree cover, as well as the habitat gain for birds and other wildlife.

The estate is planning to plant a native pinewood extending to 700 hectares, and last spring planted a community wood to provide informal recreational facilities close to Nairn.

n Scottish Native Woods has published a booklet for estate managers, Why Manage Riparian Woodlands? and a leaflet on the grants available for the management and restoration of riparian woodlands. Both publications can be obtained by contacting Scottish Native Woods at 3 Kenmore Street, Aberfeldy PH15 2BL. Tel: 0887 820392.