Effects of intrinsic precipitation‐predictability on root traits, allocation strategies and the selective regimes acting on them

Abstract

Climate change affects means, variances and the intrinsic predictability of the climate. However, experimental tests of how changes in intrinsic climatic predictability affects plant traits, allocation strategies and the selective regime acting on them are scarce, as well as evidence for the importance of root functional traits to cope with climatic uncertainty. Here, we experimentally manipulated intrinsic daily and inter‐seasonal precipitation‐predictabilities and tested their effect on root traits, root allocation strategies, the selective regime acting on them, and transgenerational root responses, using a four‐year field experiment and Onobrychis viciifolia. More predictable precipitation led to lower root biomass and a lower overall plant performance, and to higher allocation to roots and higher within‐root allocation (i.e. allocation to root branching and maximum rooting depth relative to allocation to roots). Differences in intrinsic daily and inter‐seasonal predictability induced differences in the strength of selection acting on the studied traits, but did not affect the type of the selective regime, nor the transgenerational responses. The results indicate that higher predictability constrained a plant's performance, while plants were able to cope with lower predictability. Absence of transgenerational responses in root traits with respect to the predictability treatments, points to slow or no inter‐generational changes of root traits in unpredictable habitats. Thus, adjustments in root allocation strategies and changes therein might be key to deal with increasing climatic uncertainty.