Linking nitrogen and phosphorous uptake to organic matter quantity and quality in a forested headwater stream

In headwater streams, allochthonous inputs dominate ecosystem metabolism. Previous research has linked nutrient uptake in these streams to metabolic parameters. Across biomes, respiration has been more closely linked to nutrient uptake, although the strength of this relationship is low. We hypothesize that while the amount of organic matter determines respiration, the quality of organic matter may mediate nutrient uptake. We investigated the relationship between OM quantity and quality and nutrient uptake velocities in a boulder and bedrock reach of a headwater stream in the Shawangunk Mountains, NY. We conducted short-term nutrient releases of both ammonium and SRP during summer and fall.  There were strong seasonal patterns in nutrient uptake velocities and nutrient uptake ratios that corresponded to the quantity and quality of OM. Nutrient uptake (NH₄ V_f:SRP V_f ) ratios were significantly and tightly correlated to organic matter N:P.  We conclude that although the quantity of organic matter is important; the quality of the organic matter drives nutrient uptake in these systems.