Understanding plant species response to environmental change is one of the greatest challenges ecologists face. Functional groups are relatively easy to measure characteristics of plant communities that relate to plant species survival strategies and allow species with similar strategies to be grouped together. Few studies have documented shifts in functional group strategies over time because long‐term data sets are limited. We analyzed a long‐term ecological data set from the Sierra Ancha Experimental Forest in central Arizona to evaluate how plant functional groups, species richness, and basal cover have changed from 1935 to 2017 in a chaparral community. Twenty-four permanent 1-m2 chart quadrats, which were established and mapped as early as 1935, were remeasured in 2017. We assessed changes in the functional strategies of the community using a traditional approach that examines changes in the relative abundance of plant functional types (C3 vs. C4 graminoids, and annual vs. perennial species).
Results/Conclusions
Preliminary results indicate that, over 82 years, plant basal cover increased by approximately 26%, and species richness increased by ½ species per square meter. The relative cover of C4 graminoids increased by 9.4% and C3 graminoids increased by 2.1% with half of the C3 graminoid increase attributed to the introduction of Bromus rubens, a non-native winter annual. The ratio of graminoids-to-forb species count increased from 1:7 in 1935 to 3:2 in 2017. Perennial species count decreased by approximately 4% and annual species count increased 171%. Other functional group types, such as rhizomatous vs. stoloniferous graminoids, native vs. exotic species, and half-shrubs will be analyzed and added to this study in the future. Overall, we observed a long‐term shift in composition toward more conservative drought-tolerant and grazing-tolerant graminoid species. Our findings illustrate how the usefulness of historical plots extends beyond their original objectives. Our analysis of temporal changes in plant composition and functionality provides a general framework for evaluating species and functional group response to environmental change over multiple decades.