Canopy interception of nitrogen in bulk precipitation by annually burned and unburned tallgrass prairie

Nitrogen content of bulk precipitation and throughfall (canopy leachates) was measured on annually burned and unburned tallgrass prairie during a 20 month period. Throughfall amounts averaged 58% of precipitation on unburned prairie while throughfall on annually burned sites averaged 76% of precipitation inputs. Stemflow was measured in late summer and autumn. Volumes were correlated with stem density; maximum stemflow volumes measured in this study averaged about 50% of throughfall volumes.Bulk precipitation averaged 530, 456, and 420 μg/l of nitrate, ammonium and organic nitrogen, respectively. Throughfall on burned sites averaged 345, 344 and 980 μg/l of nitrate, ammonium and organic nitrogen, and throughfall on unburned sites averaged 258, 196 and 1701 μg/l of nitrate, ammonium and organic nitrogen. Microbes on standing dead vegetation and litter of the unburned sites were estimated to remove more inorganic nitrogen from bulk precipitation than did foliage on burned sites. Only a portion of the inorganic nitrogen in bulk precipitation is immediately available for plant use, and this availability is influenced by the amount of detritus present on the prairie.