Starch and lipid storage strategies in tropical trees relate to growth and mortality

Abstract

Summary Non‐structural carbon (NSC) storage (i.e. starch, soluble sugras and lipids) in tree stems play important roles in metabolism and growth. Their spatial distribution in wood may explain species‐specific differences in carbon storage dynamics, growth and survival. However, quantitative information on the spatial distribution of starch and lipids in wood is sparse due to methodological limitations. Here we assessed differences in wood NSC and lipid storage between tropical tree species with different growth and mortality rates and contrasting functional types. We measured starch and soluble sugars in wood cores up to 4 cm deep into the stem using standard chemical quantification methods and histological slices stained with Lugol's iodine. We also detected neutral lipids using histological slices stained with Oil‐Red‐O. The histological method allowed us to group individuals into two categories according to their starch storage strategy: fiber‐storing trees and parenchyma‐storing trees. The first group had a bigger starch pool, slower growth and lower mortality rates than the second group. Lipid storage was found in wood parenchyma in five species and was related to low mortality rates. The quantification of the spatial distribution of starch and lipids in wood improves our understanding of NSC dynamics in trees and reveals additional dimensions of tree growth and survival strategies.

Variation of non‐structural carbohydrates across the fast–slow continuum in Amazon Forest canopy trees

“…Being longer lived, slow‐growing species are also more likely to experience additional stress such as drought. Our results are consistent with a recent study in southern Amazonia which also found that stem NSC storage was higher in slow‐growing species (Herrera‐Ramírez et al., 2021). Interestingly, a previous study on a semi‐deciduous forest in Panama (Würth et al., 2005) did not find a clear relationship between life‐history strategy (early and mid‐successional species) and NSC storage patterns.…”

“…Combinations of plant functional traits result in particular life‐history strategies (Salguero‐Gómez et al., 2016). For example, hard‐wooded species which invest in wood of high mechanical strength have slow growth rates and are expected to have increased investment in storage (Herrera‐Ramírez et al., 2021; King et al., 2006). This is often an advantageous strategy in habitats with low nutrient availability and other environmental stress, as it enhances plant capacity to survive pathogen attack, biomass loss or abiotic stress (Aleixo et al., 2019; O'Brien et al., 2014; Oliva et al., 2014; Quentin et al., 2015).…”

“…This is often an advantageous strategy in habitats with low nutrient availability and other environmental stress, as it enhances plant capacity to survive pathogen attack, biomass loss or abiotic stress (Aleixo et al., 2019; O'Brien et al., 2014; Oliva et al., 2014; Quentin et al., 2015). In contrast, soft‐wooded fast‐growing species have high water demand and photosynthetic rates, enabling faster growth, but reducing resistance to drought‐induced embolism (Chave et al., 2009; Hacke et al., 2006; Mcculloh et al., 2012; Oliveira et al., 2021) and may be associated with lower carbon storage, that is non‐structural carbohydrates (NSC; Falchi et al., 2020; Herrera‐Ramírez et al., 2021; Poorter & Kitajima, 2007). However, there have been very few empirical studies exploring the relationship between storage and life‐history strategies, particularly in adult tropical trees.…”

“…Non‐structural carbohydrates are the major form of energy storage in many plant species and have been shown to play a critical role in maintaining hydraulic function and enhancing survival during drought (Guo et al., 2020; Liu et al., 2018; O'Brien et al., 2014; Tomasella et al., 2017). Starch and soluble sugars comprise the most significant portions of NSC reserves in most tree genera (Martínez‐Vilalta et al., 2016), but other compounds such as lipids also play an important role as storage (Herrera‐Ramírez et al., 2021; Hoch et al., 2003). Soluble sugars are involved in multiple functions such as supporting new growth, for respiration and defence, regulating stress‐related genes and acting as osmoprotectants mitigating the negative effect caused by water stress (Krasensky & Jonak, 2012; MacNeill et al., 2017; Rosa et al., 2009; Sapes et al., 2019; Signori‐Müller et al., 2021a).…”

“…A priori, slow‐growing species would be expected to have greater NSC concentrations/pools in longer term storage tissues (e.g. stem, coarse roots) than fast‐growing species which primarily allocate carbon to growth over storage (Herrera‐Ramírez et al., 2021; Smith & Stitt, 2007). Fast‐growing species may also have more seasonal NSC dynamics as these have been found to concentrate most of their growth in the wet season, compared to slow‐growing species (Rowland et al., 2014).…”