PROBLEMS OF YIELD CONTROL AND INVENTORY IN BRITISH FORESTRY

come from thinnings. Final fellings will come predominantly from overmature crops which are a legacy from the past or from unsatisfactory crops. Yields from thinning and felling must therefore be cqnsidered quite separately. Thinning yields will depend upon increment but yields from final felling will depend mainly upon the area of overmature crops to be removed within a predetermined period of years. The data required for thinning and felling control are discussed. Part II. The theory of sampling in relation to forest enumeration is discussed briefly. The standing volume of a forest may be estimated in three ways; by the application of yield tables; by visual estimation; or by measurement. The last method may mean measuring all the trees or only a sample and the theory of enumeration plot procedure is discussed. Increment may be estimated by comparing successive enumerations of the standing crop; from yield tables; or from measurements within the tree. Finally the choice of enumeration method is discussed