Understanding vegetative ecophysiological responses of herbaceous species from a Brazilian dry forest by simulating 60‐year precipitation extremes.

In the Caatinga, a Brazilian dry forest, low water availability is a limiting factor that affects the growth and survival of herbaceous plants. Thus, we hypothesize that simulated extreme changes in precipitation modify aboveground and belowground vegetative responses differently between annual and perennial herbaceous species. Seedlings of the species were obtained through seed germination. During 1 year, they were submitted to three rainfall simulation (RS) treatments, defined from a 60‐year sequence: Twet‐RS of rainy years; Tcontrol‐RS of years close to the historical average; Tdry‐RS of dry years; and with 30 repetitions per treatment. The daily water administration corresponded to the daily average of rainfall in the past. In the simulation of dry years, the annual species reduced the growth drastically, while the perennials showed a moderate reduction. All species reduced biomass and production and expansion of their leaves in dry years but invested in water storage and leaf longevity. Below ground, annuals explored surface water resources and perennials invested in root growth, accessing underground layers. If reductions in rainfall are confirmed, the allocation of herbaceous biomass may follow an “optimal partitioning” strategy, along with maintaining higher water content in the organs, which is an efficient survival strategy. [ABSTRACT FROM AUTHOR]