||About 30% of lands both globally and in the U.S. consist of semi-arid or arid landscapes, and over 1 billion people depend on these lands for their livelihood. Despite this importance, there have been almost no studies on the impacts of future climate change in these regions. Two years ago, we established plots where we warmed the soil 2 degrees C and/or increased the frequency of summer precipitation. In the warmed plots, we observed a dramatic (40%) mortality of the dominant grass species Hilaria jamesii. In the plots with increased summer rain frequency, we had almost 100% mortality of the dominant moss Tortula ruralis. Here, we propose to follow up on these findings and document how warming and/or altered precipitation affects (1) shallow versus deep rooting plants, (2) C3 versus C4 plants, (3) grasses versus shrubs, and (4) annual versus perennial plants. We will also use laboratory experiments to specifically investigate the mechanisms behind the increased mortality of Hilaria and Tortula.