Land use change is one of the most important factors contributing to CO₂ emissions to the atmosphere, but also to the loss of biodiversity and alteration of hydrologic cycle in different biomes. In Central-Northern Mexico, the shortgrass steppe is highly threatened by different types of land use change including, overgrazing, agricultural development, and shrub encroachment. Recent assessments along the shortgrass steppe reported between 15 to 110 MT C ha^-1 y^-1, which summing the large extent of semiarid grasslands (~ 100,000 Km²). We used a large static chamber method (4.2 m diameter YurtDome 14 tent, Shelter Systems Inc., Arnone and Obrist, 2003) to quantify the NEE of CO₂ and water vapor. We selected five grassland sites subject to distinctive land use change as pat of the MX-iLTER site ‘GRACILIS’ in Central Mexico, sites include; a 30 year old grassland exclosure, an overgrazed site, srub encroachment, change in grass species composition, and transformation to agriculture. At each site, NEE, PPFD and air temperatures were measured at monthly intervals from 6 fixed plots, including three diurnal and one nocturnal observations. Preliminary results show important differences in NEE between wet and dry months (10 vs. 3 μmol CO₂ m^-2 s^-1) with October as the wettest month and January, the driest. Large differences in NEE were also observed among land use change types with switchgrass composition plots exhibiting the largest NEE uptake rates. Concurrently, the largest night ecosystem respiration was recorded for the same land use change type. Overall, dry months showed similar NEE and night respiration patterns for all five land use types. So far, a continuous vegetation cover rather than presence of key species appear to control a positive annual C balance into the ecosystem (uptake).