Extraction dataset for a multilevel meta-analysis of biochar dose effects in green roof substrates

Row-level extraction dataset underlying a systematic review and multilevel meta-analysis of biochar dose effects in green roof substrates. 2,614 effect-size rows (50 fields) from 89 studies, of which 1,110 rows from 46 studies carry a biochar-dose contrast; 2,027 rows have a computable log response ratio and 1,013 a usable sampling variance. Every row carries its provenance (page, table or figure, and a verbatim source fragment) and a dose converted to volumetric percent where the required bulk densities were reported. A field dictionary and a README with integrity checks and SHA-256 checksums accompany the CSV. Files are under restricted access; access requests are accepted without restriction on requester or purpose.