Besides LOCNESS, is there any native corpus that has a special category of argumentative essays either by native learners or by native professionals? thanks
Michigan Corpus of Upper-Level Student Papers http://search-micusp.elicorpora.info/simple/
a collection of around 830 A grade papers (roughly 2.6 million words) from a range of disciplines across four academic divisions (Humanities and Arts, Social Sciences, Biological and Health Sciences, Physical Sciences) of the University of Michigan (U-M), Ann Arbor. MICUSP was created by a team of researchers and students at the U-M English Language Institute (ELI).