SSSI - Site of Special Scientific Interest https://www.gov.uk/guidance/protected-areas-sites-of-special-scientific-interest.
SACs Special Areas of Conservation and SPAs Special Protection Areas http://jncc.defra.gov.uk/page-23.
Ramsar (refers to the Ramsar Treaty for the conservation and sustainable use of Wetlands) http://jncc.defra.gov.uk/page-161
These confer special protection on the country's very best wildlife, geological and wetland sites.
Trees on these sites are likely to be subject to management agreements. http://www.naturalengland.org.uk/.