Calculate as: the Rank of previously marked leaf at one point in time, minus 1 (equivalent to the Rank of marked youngest leaf), divided by the time elapsed between the two Date of data collection events when the marked leaf was recorded as 1) the Rank of marked youngest leaf and 2) the Rank of previously marked leaf, e.g. (2 - 1) / 1 week = LER of 1 leaves/week during a particular time period. Weekly leaf emission rate - computation attribute variable_of method_of entity scale_of acronym