David Sulman is director of the Stirling-based UK Forest Products Association, which represents 60 British companies, one-third of them located in Scotland. He accused the FCS of risking "a rapid decline of the domestic wood processing industry" by failing to plan for future stocks of commercial conifers.
Sulman warned that increased scarcity of commercial conifers was causing "dangerous overheating" and "endangering future investment" in the Scottish wood market. This was partly caused, he said, by the wind farm-related felling, and partly because of increased demand stimulated by public subsidies for burning wood in power stations via renewables obligation certificates.
He said: "It feels as if the forest industries are being attacked from two sides. They both happen to be associated with renewable energy."
He also said that, in permitting the leasing of large tracts of forested land to wind farms, the FCS was failing to follow best practice in Scandinavia and the rest of Europe, where they practise so-called "keyholing" - restricting felling to trees immediately surrounding new turbines rather than clearing large areas.
Earlier this month the FCS disclosed under Freedom of Information legislation that more than 6200 acres of Scottish forestry land, or five million trees, have been felled for wind farms since 2007. In the same period, fewer than 2000 acres of trees have been replanted within the sites, a net loss of around 3.4 million trees.
Sulman said: "These developments may help to meet the Scottish Government's renewables targets and provides their coffers with significant revenue from developers.
"[But] at a time when people are increasingly recognising the need for more trees, as carbon dioxide 'stores' and as sources of sustainable construction products, it just seems wrong to be felling vast swathes of forest to replace them with wind turbines which are of more questionable benefit."
The Scottish Government, to which the FCS is accountable, previously rejected objections to the net loss of trees by claiming to be "supporting" more than 31,000 hectares of new planting. However, Paul Wheelhouse, the Environment Minister, did not specify whether this extended to the FCS planting like-for-like commercial trees on its own land.
The wood products industry has also complained that an initial Scottish Government commitment to ensuring "compensatory planting" (CP) - an obligation on renewables developers to replace felled trees - appears not to have been enforced.
Sulman said: "They have been talking about CP obligation almost as long as wind farms have been on the FCS estate. The requirement was simply 'advice to planners'. It didn't have to be done, and therefore it generally hasn't happened."
Concerns about the scale of the destruction of FCS tree stocks to make way for wind farms and for biomass have arisen because of the potential effect of a scarcity on price, and the related sustainability of a timber industry that employs 19,000 direct jobs and 38,500 indirect jobs in Scotland, according to Scottish Enterprise.
Sawn wood is an internationally traded commodity, and therefore highly price-sensitive. According to Alastair Kerr, director general of the Wood Panel Industries Federation, another industry body, falling stocks of commercial softwood from the FCS estate have contributed, albeit to an unknown extent, to a price rise of around 23% in industrial roundwood (ie, raw timber) in the past five years.
Productivity and quality improvements in the UK sawmill and panel-making industries have helped boost the proportion of native wood in the UK supply chain from 20% to 40% since 2003, displacing imports from Scandinavia and the Baltic states and elsewhere. However, the UK Forest Products Association fears that progress could be reversed if scarcity drives up UK prices, with damaging knock-on effects on jobs.
A Forestry Commission spokesman said: "The results from the 25-year softwood forecast shows that there is increasing potential timber availability until the early 2030s.
"We are already working closely with stakeholders to develop the forestry elements of the next Scotland Rural Development Programme, which will include measures aimed at incentivising the private sector to make a substantial contribution to our commitment of creating a further 100,000 hectares of new woodland over the next 10 years, with an increased emphasis on productive woodland."