coverChange: Models the weighted mean of plant separation from time since...
In pzylstra/Impact: Fire impact functions for FRaME

Checks for alternate growth models

1	coverChange(st, a, cover, Flora, age)

`st`	The name of the stratum
`a`	The number of the record to be modelled
`cover`	A dataframe with the fields: species - Name of the species consistent with other tables constant - Mean plant separation (m) that does not change with age exp_a - The first constant in an exponential function describing plant separation with tsf exp_b - The second constant in an exponential function describing plant separation with tsf
`Flora`	A dataframe with the fields: record - a unique, consecutively numbered identifier per site species - the name of the species, which will call trait data from 'default.species.params' moisture - the moisture content of the species in whole numbers (eg 1 for 100 stratum - numeric value from 1 to 4, counting from lowest stratum comp - base, he, ht, top & w - canopy dimensions for that species (m). he and ht are optional clump - mean ratio of clump diameter to crown diameter openness - ratio of gap to clump size
`age`	The number of years since last fire