In arid and semiarid regions around the world, extensive areas of grasslands have been replaced by shrublands. A better understanding of the ecology of these shrublands compared to historical grasslands would help land managers make decisions for the sustainable provision of ecosystem goods and services. We compared aboveground net primary production (ANPP) and its response to precipitation between shrublands and grasslands in the Chihuahuan Desert, with an emphasis on differences among seasons and among functional groups of species. The study site, Jornada Basin USDA-LTER site, is located in the northern Chihuahuan Desert. The ANPP and precipitation data were collected at 15 locations in 5 ecosystem types: 3 shrubland types and 2 grassland types (N=3 for each type) during 1990-2010.  Three seasons were defined: winter (Oct – Feb), spring (Mar – May), and fall (Jun- Sep).  ANPP was separated into three plant functional groups: shrubs, perennial grasses, and others. The results showed significant differences between shrublands and grasslands in the seasonal pattern of ANPP, and in the relationship between precipitation at different time periods with seasonal ANPP. Compared to grasslands where ANPP was highest in the fall, shrubland ANPP occurred more evenly among all three seasons. For most locations, seasonal precipitation did not explain the most variation in the current season’s ANPP. The precipitation period explaining the most variation in seasonal ANPP varied among ecosystem types and among locations within each type. These results suggest that other factors, such as soil water content, may be driving seasonal variation in ANPP, and that land management practices may need to be tailored to specific ecosystem types.