Gradient ANPP 2002_2016

This experiment occurs across five life zones along an elevation gradient in northern Arizona: mixed confer forest, 2620 m above sea level (masl), mean annual temperature (MAT) of 6.6 °C, and mean annual precipitation (MAP) of 543.3 mm, Ponderosa Pine Forest (2344 masl, MAT 8.9, MAP 392.8), Piñon-Juniper Woodland (2020 masl, MAT 10.8 , MAP 272.0), and Great Basin Desert (1556m, MAT 12.8, MAP 127.3). Each site is equipped with a weather station. From the mixed conifer, ponderosa pine, piñon-juniper, and high desert grassland life zones, 40 mesocosms (30 cm diameter x 30 cm deep) were removed from grass-dominated areas in 2002. Each mesocosm was placed intact into PVC cylinders. 20 mesocosms from each life zone were transplanted down-slope to the adjacent, lower elevation, life zone to effect a warming treatment. The 20 remaining mesocosms were transplanted within the site of origin as controls. The great basin desert site served as the warming treatment from the grassland life zone. Precipitation treatments at each site were effected using passive interceptors to divert precipitation off of each individual mesocosm (30% reduction), or to divert additional precipitation onto each mesocosm from the area around it (50% increase), with ambient precipitation as a control (n=6 or 7). These treatments were selected to span the range of projected precipitation changes according to Christensen et al. (2007).