Plant traits controlling growth change in response to a drier climate

Lucy Rowland,Ingrid Coughlin,João A S Junior,Andre L Giles,Tomas Domingues,Leandro V Ferreira,Patricia De Britto Costa,Antonio C L Da Costa,Paulo R L Bittencourt,Maurizio Mencuccini,Steel S Vasconcelos,Alex A R Oliveira,Rafael S Oliveira,Patrick Meir

doi:10.1111/nph.16972

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. 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. 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. 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.

Highlights

Uncertainty concerning the net carbon balance of tropical ecosystems propagates to generate one of the greatest uncertainties in the global carbon budget (Tian et al, 2020; Piao et al, 2020)
New Phytologist (2020) www.newphytologist.com drought experiment as a case study, we explore how the relationships between plant traits and growth rates change when trees are exposed to prolonged soil drought stress
For the drought forest we find that alongside the correlations found for Jmax (R = 0.38) and Rstem (R = 0.46), there is a strong significant negative relationship between mean annual growth and SMP50, which is absent in the control forest (Fig. 4; Table 2)

Summary

Introduction

Uncertainty concerning the net carbon balance of tropical ecosystems propagates to generate one of the greatest uncertainties in the global carbon budget (Tian et al, 2020; Piao et al, 2020). Plant functional traits are commonly used to predict plant and ecosystem function (Reich et al, 1997; Poorter et al, 2008; Kattge et al, 2011; Diaz et al, 2016; Kunstler et al, 2016). This is largely because at large geographical scales, plant traits have been found to cluster and form trade-offs associated with leaf photosynthetic, wood density or plant life-history strategies (Wright et al, 2004; Chave et al, 2009; Patin~o et al, 2012; Adler et al, 2014; Diaz et al, 2016; Mencuccini et al, 2019). Considerable uncertainty remains concerning how plant traits are linked to plant demographic rates (Liu et al, 2016; Falster et al, 2018; J. Yang et al, 2018)

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Discussion

Conclusion