Agricultural land use alters temporal dynamics and the composition of organic matter in temperate headwater streams

AbstractIntensification of agricultural land use leads to riparian clear cutting, which disrupts stream aquatic-terrestrial linkages through the loss of terrestrial particulate organic matter (POM). POM is important for structuring habitats and serves as a basal resource for food webs. We studied the effects of agricultural land use on the fate and temporal dynamics of POM inputs and standing crops by comparing 2 agricultural and 2 forested reference streams for 15 mo. We used the C spiraling metrics downstream velocity of organic C (VOC) and index of retention (IR) to integrate information on the dynamics of benthic organic matter (BOM) with physical characteristics of the streams. Daily POM inputs into reference streams were 15 to 39× higher than inputs into agricultural streams, and mean standing crops of total BOM were significantly lower in agricultural streams than in reference streams. Agricultural streams had significantly higher standing crops of fine benthic organic matter (FBOM), but 1.8 to 3× ...