The capacity of forests to mitigate global climate change can be negatively influenced by tropospheric ozone that impairs both photosynthesis and stomatal control of plant transpiration, thus affecting ecosystem productivity and watershed hydrology. We have evaluated individual and interactive effects of ozone and climate on late season streamflow for six forested watersheds (38–970 000 ha) located in the Southeastern United S...

We measured uptake length of 15 NO 3 − in 72 streams in eight regions across the United States and Puerto Rico to develop quantitative predictive models on controls of NO 3 − uptake length. As part of the Lotic Intersite Nitrogen eXperiment II project, we chose nine streams in each region corresponding to natural (reference), suburban‐urban, and agricultural land uses. Study streams spanned a range of human land use to maximiz...

We measured denitrification rates using a field 15 NO 3 − tracer‐addition approach in a large, cross‐site study of nitrate uptake in reference, agricultural, and suburban‐urban streams. We measured denitrification rates in 49 of 72 streams studied. Uptake length due to denitrification ( S Wden n) ranged from 89 m to 184 km (median of 9050 m) and there were no significant differences among regions or land‐use categories, likely...

Streams are typically supersaturated and emit methane to the atmosphere. Much of this gas appears to be imported from groundwater and riparian zones, where anoxia and methane production are common. We investigated how methane evasion and the concentration in groundwater discharge varied between five stream sections with differing rates of groundwater discharge along the east fork of Walker Branch in eastern Tennessee. Evasion...

Wheat ( Triticum aestivum L.) cv. Minaret was grown in open‐top chambers (OTCs) in 1995 and 1996 under three carbon dioxide (CO 2 ) and two ozone (O 3 ) levels. Plants were harvested regularly between anthesis and maturity to examine the rate of grain growth (dG/dt; mg d –1 ) and the rate of increase in harvest index (dHI/dt;% d –1 ). The duration of grain filling was not affected by elevated CO 2 or O 3 , but was 12 days shor...

Spring wheat cv. Minaret was grown to maturity under three carbon dioxide (CO 2 ) and two ozone (O 3 ) concentrations in open‐top chambers (OTC). Green leaf area index (LAI) was increased by elevated CO 2 under ambient O 3 conditions as a direct result of increases in tillering, rather than individual leaf areas. Yellow LAI was also greater in the 550 and 680 μmol mol –1 CO 2 treatments than in the chambered ambient control; i...