THE RESTORATION AND MANAGEMENT OF RANGELANDS IS MORE CHALLENGING TODAY THAN AT ANY POINT IN HUMAN HISTORY. DRIER AND MORE VARIABLE RAINFALL PATTERNS COMPARED TO THE LAST CENTURY HAVE UNKNOWN CONSEQUENCES FOR PLANT COMMUNITIES, AND INVASIVE SPECIES HAVE ALTERED A RANGE OF ECOSYSTEM SERVICES IN RANGELANDS INCLUDING PRODUCTIVITY, BIODIVERSITY, AND RATES OF NUTRIENT AND WATER CYCLING. MOST ATTEMPTS TO RESTORE ECOSYSTEMS RELY ON TRIAL-AND-ERROR APPROACHES AND MANY FAIL, IN PART, DUE TO THE LACK OF A COMMUNITY-ORIENTED APPROACH. ECOLOGISTS HAVE LONG THEORIZED THAT A COMMUNITY ASSEMBLY FRAMEWORK THAT EMPHASIZES FUNCTIONAL TRAITS (CHARACTERISTICS OF SPECIES THAT INFLUENCE THEIR PERFORMANCE) COULD GUIDE AND ENHANCE RESTORATION, BUT EMPIRICAL TESTS OF THESE IDEAS ARE LACKING. APPLYING ECOLOGICAL THEORIES TO ACHIEVE RESTORATION GOALS ACROSS DIFFERENT COMMUNITY TYPES WOULD REPRESENT ONE OF THE GREATEST ACHIEVEMENTS FOR ECOLOGICAL RESTORATION.IT IS WIDELY ACCEPTED THAT FUNCTIONAL TRAITS INFLUENCECOMPETITIVE INTERACTIONS AND RESISTANCE TO STRESS, LIKE DROUGHT. THUS, SELECTING SPECIES FOR RESTORATION PROJECTS BASED ON FUNCTIONAL TRAITS SHOULD ALLOW MANAGERS TO MEET MULTIPLE GOALS IN RESTORED COMMUNITIES, INCLUDING DROUGHT TOLERANCE, INVASION RESISTANCE, AND THE LONG-TERM SUSTAINABILITY OF ECOSYSTEM SERVICES.THE SPECIFIC OBJECTIVE OF THE PROJECTIS TO TEST WHETHER A TRAIT-BASED MODEL CAN BE USED TO RESTORE VALUABLE ECOSYSTEM SERVICES BY STRENGTHENING DROUGHT TOLERANCE AND INVASION RESISTANCE. WE WILL WORK IN TWO ECOLOGICALLY DISTINCT AND ECONOMICALLY IMPORTANT RANGELANDS: ANNUAL-DOMINATED GRASSLAND IN CALIFORNIA AND PERENNIAL DOMINATED MIXED-GRASS PRAIRIE IN WYOMING. DROUGHT AND INVASIVE PLANTS ARE KEY CHALLENGES FACED BY PRODUCERS IN BOTH REGIONS. WE WILL FIRST COMBINE A NEWLY-DEVELOPED MODEL WITH DETAILED PLANT-TRAIT DATA FROM THE TWO SITES TO DESIGN SPECIES ASSEMBLAGES THAT ARE OPTIMIZED FOR DROUGHT TOLERANCE, INVASION RESISTANCE, OR FUNCTIONAL DIVERSITY. SPECIES MIXTURES WILLBE ESTABLISHED IN FIELD PLOTS AND SUBJECTED TO DROUGHT AND INVASION BY EXOTIC ANNUAL GRASSES. COMMUNITY COMPOSITION, PLANT PERFORMANCE, AND FOUR ECOSYSTEM SERVICES (PRODUCTIVITY, FORAGE QUALITY, NUTRIENT CYCLING, WATER USE) WILL BE MEASURED FOR THREE YEARS FOLLOWING COMMUNITY ESTABLISHMENT. THIS RESEARCH WILL BE A STRONG EMPIRICAL TEST OF TRAIT-BASED ECOLOGICAL THEORIES IN ECOSYSTEM MANAGEMENT, AND WILL ALLOW RANGELAND MANAGERS TO USE INCREASINGLY AVAILABLE PLANT TRAIT DATA TO TAILOR RESTORATIONS TO BOTH SITE CONDITIONS AND DESIRED ECOSYSTEM SERVICES.?