I am trying to do a DCA in R with vegan package and decorana() function for a vegetation dataset. the Dataset consists of plots in rows, with abundance of dif. plant species in colums. When running

 dca_result <- decorana(species_data)

I get back

Error in decorana(species_data) : 
  'decorana' cannot handle negative data entries

the Data looks like this

str(species_data)

'data.frame':   419 obs. of  174 variables:
 $ Agrostis.canina              : num  0 2.5 0 0 0 0 0.2 0 0 6.5 ...
 $ Agrostis.stolonifera         : num  0 0 0 0 0 0 0 0 0 0 ...
 $ Ajuga.reptans                : num  0 0 0 0 0 0 0 0 0 0 ...
 $ Anthoxantum.odoratum         : num  0 0 0 0 0 0 0 0 0 0 ...
 $ Avenella.flexuosa            : num  0 0 0 0 0 0 0 0 0 0 ...
 $ Ahtyrium.filix.femina        : num  0 0 0 0 0 0 0 0 0 0 ...
 $ Betula.pendula               : num  0 0 0 0 0 0 0 0 0 0 ...
 $ Struthiopteris.spicant       : num  0 0 0 0 0 0 0 0 0 0 ...
 $ Calamagrostis.arundinacea    : num  0 0 0 0 0 0 0 0 0 0 ...
 $ Callitriche.spec             : num  0 0 0 0 0 0 0 0 0 0 ...
 $ Calluna.vulgaris             : num  3.5 0 0 0 18 0 0 0.2 0 0 ...

I did

library(fixr)
check_for_negative_values(species_data)

it returns

Data frame does not contain negative values.
NULL

so there should be no negative values right, what could be the problem then?