There is considerable uncertainty in the magnitude and direction of changes in precipitation associated with climate change, and ecosystem responses are also uncertain. Multiyear periods of above‐ and below‐average rainfall may foretell consequences of changes in rainfall regime. We compiled long‐term aboveground net primary productivity ( ANPP ) and precipitation ( PPT ) data for eight North American grasslands, and quantifie...

Atmospheric CO 2 ( C a ) concentration has increased significantly during the last 20 000 years, and is projected to double this century. Despite the importance of belowground processes in the global carbon cycle, community‐level and single species root responses to rising C a are not well understood. We measured net community root biomass over 3 years using ingrowth cores in a natural C 3 –C 4 grassland exposed to a gradient...

We evaluated the influences of CO 2 [Control, ∼ 370 µ mol mol − 1 ; 200 µ mol mol − 1 above ambient applied by free‐air CO 2 enrichment (FACE)] and soil water (Wet, Dry) on above‐ and below‐ground responses of C 3 (cotton, G ossypium hirsutum ) and C 4 (sorghum, Sorghum bicolor ) plants in monocultures and two density mixtures. In monocultures, CO 2 enrichment increased height, leaf area, above‐ground biomass and reproductive...

Plant species richness influences primary productivity via mechanisms that (1) favour species with particular traits (selection effect) and (2) promote niche differentiation between species (complementarity). Influences of species evenness, plant density and other properties of plant communities on productivity are poorly defined, but may depend on whether selection or complementarity prevails in species mixtures. We predicted...

Plants may be more sensitive to carbon dioxide (CO 2 ) enrichment at subambient concentrations than at superambient concentrations, but field tests are lacking. We measured soil‐water content and determined xylem pressure potentials and δ 13 C values of leaves of abundant species in a C3/C4 grassland exposed during 1997–1999 to a continuous gradient in atmospheric CO 2 spanning subambient through superambient concentrations (2...