Community weighted trait means (CWMs) have been used in ecological research to demonstrate shifts in mean trait values selected from environmental disturbances. As fluctuations in global climatic patterns result in an increased frequency of prolonged drought periods, plant ecosystem shifts occur not only in species relative abundance, but also plant functional composition. Subsequent changes in species dominance affect ecosystem processes like aboveground net primary production, nutrient cycling, and leaf water economic strategy, which can be quantified by plant traits indicating ecosystem functionality in the mixed grass prairie ecosystem. Based on foliar cover data over a timespan of six years (2016 to 2022), this study uses nine target species to determine community weighted means of aboveground plant functional traits (SLA, LDMC, C:N, LMA, and N%) gathered from seven rainfall exclusion shelters in central Oklahoma, weighted according to their relative abundance. Using the resulting CWM values, we aim to determine the traits driving shifts in community assembly, and thereby identify successful life strategies of plant ecosystems under long-term drought.
Based on leaf traits weighted by abundance in moderate, control, and severe drought treatments, we found significant differences in weighted trait means of leaf chemical composition in mild treatments, while both control and severe rainfall exclusion shelters appeared to have similar leaf chemical trait values. In other words, the C:N ratio trait means for plant communities in the –100%, -60%, and –20% rainfall exclusion shelters were significantly different (P<0.01) than the leaf chemical composition in the -80% shelters. However, we also noted an increase in leaf C:N ratio weighted trait means (R2= 0.1275) with increasing rainfall availability from –100% to -20% exclusion. The latter of our results indicate that plant communities subject to more severe drought are likely to filter for plants with C:N traits at the slower end of the plant economics spectrum, and plants exhibiting higher N use efficiency. However, the significant differences in C:N trait means between moderate, and severe treatments signify a divergence successful life strategies under varying levels of drought.
