What happens to allochthonous material that falls into streams? A synthesis of new and published information from Coweeta

1. ,One of two things can happen to allochthonous material once it enters a stream: it can be broken down or it can be transported downstream. The efficiency with which allochthonous material is used is the result of these two opposing factors: breakdown and transport. 2. ,The present synthesis of new and published studies at Coweeta Hydrologic Laboratory compares biological use versus transport for four categories of particulate organic material: (1) large wood (logs); (2) small wood (sticks); (3) leaves; and (4) fine particulate organic matter (FPOM). 3. ,Over 8_years, logs showed no breakdown or movement. 4. ,The breakdown rate of sticks (≤3_cm diameter) ranged from 0.00017 to 0.00103_day−1, while their rate of transport, although varying considerably with discharge, ranged from 0 to 0.1_m_day−1. 5. ,Based on 40 published measurements, the average rate of leaf breakdown was 0.0098_day−1. The leaf transport rate depended on stream size and discharge. 6. ,The average respiration rate of FPOM was 1.4_mg_O2_g_AFDM−1_day−1 over a temperature range of 6–22_°C, which implies a decomposition rate of 0.00104_day−1. Transport distances of both corn pollen and glass beads, surrogates of natural FPOM, were short (