They spoke after reports that Defra was toying with a mass clear out of land owned by the Forestry Commission. It survived last week's quango cull but ministers said it would be overhauled.
Newspaper reports said transfer of ownership of much of England's woods would take five years and was prompted by a desire to "energise forests, bring in fresh ideas and investment and put conservation in the hands of communities".
Institute of Chartered Foresters executive director Shireen Chambers said: "It's inevitable they will look at disposal but by no means inevitable they will do it. Scotland reviewed this last year and so did Margaret Thatcher in 1984. They didn't go ahead because timber is a huge resource."
Tree consultant Jeremy Barrell added: "It is right to revamp a group formed in 1919. It is inefficient and ineffective in dealing with urban trees - as big a resource as forests, but completely ignored.
"The commission is good at overseeing felling, planting and managing, but most of this is outsourced to private firms. As long as it can retain its influence and deliver overall strategy aims, it matters not a jot if the work is done privately."
Tree Council director-general Pauline Buchanan Black said: "This could be worrying if it results in vast tracts of commercial forestry because it would close down an option for improving health when this is high on the agenda.
"But change could result in the commission becoming a charity, which has benefits - you can attract more money, steer clear of Government business and campaign more. But woodland needs ongoing resources."
Arboricultural Association director Nick Eden said: "It is an opportunity to focus on urban green infrastructure - 90 per cent of people live in towns. But multiple owners could make site access tricky and thwart wildlife protection."
The Forestry Commission did not comment but Defra said a strategy looking at modernisation and growth in the forestry sector will be published later this autumn.
A representative said: "Forests will continue to play a full role in our efforts to combat climate change, protect the environment, enhance biodiversity and provide green space for access and recreation."
Meanwhile, business secretary Vince Cable this week called for high-profile woodlands to be protected, referring to the New Forest as a "national resource".
Wales and Scotland, as devolved administrations, were not believed to be part of the sell-off. Welsh rural affairs minister Elin Jones said: "Forestry is a devolved matter and decisions lie with Welsh ministers."