Prior summer rain gave no clear nitrogen contrast in four British butterfly samples in 1987-2012

We tested whether prior summer rainfall slopes of butterfly site indices differed with nitrogen deposition and host-plant nitrogen. Four fixed-effect models used 352,250 records in southern England and the other British sites in 1987-1999 and 2000-2012. All four main intervals included zero after correction for four tests. Site-year, site-species and regional species-year effects controlled shared observation conditions and broad species changes. Current summer rainfall and local seasonal temperature were controls. These results do not establish that nitrogen and dry weather do not interact. Static pollution, country-average rain, selected transects, missing records and 13 year clusters per fit limit inference. The package gives frozen inputs, source hashes, code, all checks and a figure.

butterflies · nitrogen deposition · rainfall · observation bias · regional comparison · uncertainty