DIFFERENCES IN O-18 CONTENT OF THROUGHFALL AND RAINFALL IN HARDWOOD AND CONIFEROUS FORESTS

The differences between deltaO-18 in throughfall and open rainfall wer e studied for 16 selected spring and summer storms in deciduous, pine and spruce forests in central Pennsylvania, USA. Throughfall deltaO-18 averaged 0.17, 0.32 and 0.24 parts per thousand greater than deltaO-1 8 of open rainfall for all storms at the deciduous, pine and spruce si tes, respectively. Throughfall O-18 enrichment was greater in low inte nsity spring rainfall events than higher intensity growing season stor ms and greater in the coniferous stands than the deciduous hardwood st and. Maximum throughfall O-18 enrichment of 1.61 parts per thousand oc curred in the spruce forest during one spring event. The differences b etween rainfall and throughfall O-18 observed in this study for indivi dual storm events may have important implications for isotope flow sep aration studies.