Abstract Year effects are contingencies in community assembly ascribed to differences among years in which communities begin to establish and add uncertainty to restoration outcomes. Year effects are often attributed to differences in climate, but no studies have captured enough natural variation in climate among years communities establish to evaluate how fully planting‐year climate may explain year effects. We restored prairie communities every other year for 12 years, capturing natural interannual variation in climate to test the hypothesis that dissimilarity in planting‐year climate predicts dissimilarity in developing plant community composition. We also examined the extent to which planting‐year precipitation and temperature explain cover of species and major compositional groups to interpret climate‐community dissimilarity relationships. Percent cover of each plant species was surveyed in each restoration for the first 3 years of community development. Community dissimilarity matrices were related to planting‐year climate dissimilarity matrices using multiple regression on distance matrices. The explanatory power of planting‐year climate variables on the cover of individual species and broad compositional groups was examined using linear and exponential models. Dissimilarities in planting‐year precipitation variables were typically the strongest statistical predictors of community dissimilarity, and differences in planting‐year precipitation received shortly after sowing remained a significant predictor of community dissimilarity into the third growing season. In first‐year communities, forb cover was dominated by volunteer species and positively related to annual average daily temperature, whereas total annual precipitation explained significant variation in sown C 4 grasses. In subsequent years, forb cover (increasingly sown species) was best predicted by and inversely related to the early growing season window of the variable (precipitation) that predicted C 4 grass cover in the establishment year. Likewise, C 4 grass cover in subsequent years was best predicted by and inversely related to the early season window of the variable (temperature) that predicted forb cover in the establishment year. Synthesis and applications . This study demonstrates planting‐year climate can predict the cover of frequently occurring species and major compositional groups in prairie developing from seed. Our results advance understanding of factors contributing to variable restoration outcomes, which is needed to achieve conservation goals.
Storc et al. (Fri,) studied this question.