Plant traits controlling growth change in response to a drier climate

Abstract

Plant traits are increasingly being used to improve prediction of plant function, including plant demography. However, the capability of plant traits to predict demographic rates remains uncertain, particularly in the context of trees experiencing a changing climate. 2. Here we present data combining 17 plant traits associated with plant structure, metabolism and hydraulic status with measurements of long-term mean, maximum and relative growth rates for 176 trees from the world's longest running tropical forest drought experiment. 3. We demonstrate that plant traits can predict mean annual tree growth rates with moderate explanatory power. However, only combinations of traits associated more directly with plant functional processes, rather than more commonly employed traits like wood density or leaf mass per area, yield the power to predict growth. Critically we observe a shift from growth being controlled by traits related to carbon cycling (assimilation and respiration) in well-watered trees, to traits relating to plant hydraulic stress in drought-stressed trees. 4. We also demonstrate that even with a very comprehensive set of plant traits and growth data on large numbers of tropical trees, considerable uncertainty remains in directly interpreting the mechanisms through which traits influence performance in tropical forests.

Tropical tree growth sensitivity to climate is driven by species intrinsic growth rate and leaf traits

“…Most physiological traits directly related to photosynthesis (Table 1) successfully captured species differences in growth sensitivity to SRAD anomalies (Figure 5; Figure S6), confirming the importance of physiological traits to investigate potential mechanisms underlying differences in demographic responses to climate change among species (Brodribb et al, 2020; Powers et al, 2020; Rowland et al, 2021). Increasing values of these traits attenuated the tree growth reduction following increasing SRAD anomalies (Figure 5; Figure S7), suggesting that species investing in a more responsive and flexible photosynthetic machinery may cope better with unusually high direct exposure to sunlight.…”

Hard times for high expectations from hydraulics: predicting drought‐induced forest mortality at landscape scales remains a challenge

“…Venturas et al include trait changes across sites to account for acclimation in leaf area and photosynthetic capacity; however, GLM and RF models did not select identical acclimation scenarios nor did they suggest that acclimation consistently improved predictions, possibly highlighting the need to consider acclimation more carefully. Predicting how key combinations of traits, especially hydraulic traits, acclimate to spatial and temporal changes in environmental conditions will be essential in understanding how to model drought-induced mortality and changes to plant demography in the future (Rowland et al, 2021). To add to this, legacy effects of previous land use and disturbance events, including drought, are likely to be highly variable across sites and yet critical for properly capturing site-to-site differences in drought-induced mortality.…”

Tropical tree growth sensitivity to climate is driven by species intrinsic growth rate and leaf traits

“…As high growth rates may come with a cost of lower stresstolerance (Reich 2014;Gibert et al 2016), acquisitive strategies could increase growth sensitivity to climate anomalies, while conservative strategies could attenuate it. Physiological traits directly related to photosynthesis and water use efficiency are good candidates to reflect the effects of lightand water-related climate variables on tree growth and forest dynamics (Wagner et al 2014;Brodribb et al 2020;Powers et al 2020;Rowland et al 2021).…”