Yeast lees: Solid sludge-like sediment, primarily spent yeast, which settles to the bottom of a fermentation tank after the fermentation is completed. Yeast lees should not be allowed to remain in contact with the wine any longer than necessary. This is because spent and decomposing yeast is the primary source of H2S (the odour of rotten eggs) in wine. This can be confusing: the world's best sparkling wines are produced by deliberately leaving wine in intimate contact with spent yeast in sealed bottles during the secondary fermentation. The answer is in the strains of yeast used and the oxygen-free conditions inside a champagne bottle compared to the tank.
Low-yielding vineyards: Vineyards which produce lower amounts of fruit (grapes) on the vine, absorbing more minerality and nutrients from the soil which is passed to the fruit enhancing the quality of grapes and thus the wine. These vineyards are held for high quality production.