need to constrain community composition values to less than or equal to one so that data are entered only as decimal fractions

[srearl]

There was a problem with the 2023 annuals composition data in that (1) values were recorded as a mix of per cent and decimal fractions, and (2) total shrub cover was (at least for some if not all records) recorded as the sum of Larrea and Ambrosia cover. These oversights were corrected to the extent possible, with some entries unfortunately requiring conversion to NULL. A notes field was added to indicate records that were corrected, though notes are not reflected in records that probably should have been corrected but for which we did to have enough information. Further, a constraint was added to cover_events to ensure that only unique events (plot * year) are recorded.

For future surveys:

• the data entry application should constrain allowable entries to <= 1 to increase the likelihood that values are entered only as decimal fractions
• field crews should be reminded to score total cover as a separate measure that is not necessarily the sum of sub-components