In 2011 the Ministery of Economic Affairs, Agriculture and Innovation asked the BLWG to update
the Dutch Red List of bryophytes. The Red List is derived from distribution data recorded between
1900 and 2011 on a quadrant basis (5 x 5 km squares). The Dutch recording grid for distribution
data consists of 1476 quadrants.
The proper estimation of species richness for different time periods requires a method to correct
for recording bias. We used the method and Frescalo program published recently by Hill (2012).
This BLWG-report documents the implementation of the Frescalo program in Visual Basic for
Applications (MS Access 2010) including modules for input/output and describes the corresponding
database structure. Additional analyses evaluate parameter settings.
The Frescalo program estimates species richness by evaluating local frequencies in neighbourhoods
of each quadrant. The VBA-version determines neighbourhoods by considering physical distance
and abiotic similarity (features of soil, ground water and geomorphology).
Model output mainly depends on 1) the size of the neighbourhood used to estimate local species
frequencies; 2) the proportion of local benchmark species used to estimate sampling intensity; 3)
the expected mean neighbourhood frequency (assumed to be independent of species richness).
Frescalo output is used to calculate the expected number of quadrants per species for each decade
between 1900 and 2011.
|Number of pages||44|
|Publication status||Published - 2013|
- endangered species