Leaf:wood allometry and functional traits together explain substantial growth rate variation in rainforest trees

Geological Substrate Effects on Teucrium montanum L. (Lamiaceae) Morphological Traits: Geometric Morphometrics Approach

The shape-environment relationship in plants refers to the ways in which the physical characteristics and structures of plants are influenced by their environment. Plants have evolved a remarkable ability to adapt to their specific habitats, and their shape and form play a crucial role in determining their survival and reproductive success. This study aimed to examine differences in size and shape between morphological traits in mountain germander (Teucrium montanum L.) from different geological substrates (calcareous and serpentinite). For this study, 400 individuals of T. montanum from 20 populations (ten populations from the serpentinite and ten from the calcareous substrate) were selected. Using the geometric morphometrics approach, it was shown that the degree of phenotypic variation in the size and shape of the corolla, leaf, and stem of T. montanum depends on the type of substrate. The main differences between the populations are the narrower part of the lower lip of the corolla, the narrower leaf, and the wider central part of the vascular system stem from serpentinite populations. The results of this study will contribute to a better understanding of the morphological variability of T. montanum in relation to edaphic conditions. In addition, the results confirm that certain morphological differences play an important role in the adaptive response in relation to substrate composition, especially for substrates with increased metal content, such as serpentinite. The shape-environment relationship in plants could define diversity and complexity in plant life, and underscores the importance of shape as a key factor in their survival and success in different habitats.

Nitrogen concentration and physical properties are key drivers of woody tissue respiration

BACKGROUND AND AIMS

Despite the critical role of woody tissues in determining net carbon exchange of terrestrial ecosystems, relatively little is known regarding the drivers of sapwood and bark respiration.

METHODS

Using one of the most comprehensive wood respiration datasets to date (82 species from Australian rainforest, savanna and temperate forest), we quantified relationships between tissue respiration rates (Rd) measured in vitro (i.e. 'respiration potential') and physical properties of bark and sapwood, and nitrogen concentration (Nmass) of leaves, sapwood and bark.

KEY RESULTS

Across all sites, tissue density and thickness explained similar, and in some cases more, variation in bark and sapwood Rd than did Nmass. Higher density bark and sapwood tissues had lower Rd for a given Nmass than lower density tissues. Rd-Nmass slopes were less steep in thicker compared with thinner-barked species and less steep in sapwood than in bark. Including the interactive effects of Nmass, density and thickness significantly increased the explanatory power for bark and sapwood respiration in branches. Among these models, Nmass contributed more to explanatory power in trunks than in branches, and in sapwood than in bark. Our findings were largely consistent across sites, which varied in their climate, soils and dominant vegetation type, suggesting generality in the observed trait relationships. Compared with a global compilation of leaf, stem and root data, Australian species showed generally lower Rd and Nmass, and less steep Rd-Nmass relationships.

CONCLUSIONS

To the best of our knowledge, this is the first study to report control of respiration-nitrogen relationships by physical properties of tissues, and one of few to report respiration-nitrogen relationships in bark and sapwood. Together, our findings indicate a potential path towards improving current estimates of autotrophic respiration by integrating variation across distinct plant tissues.

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

A better understanding of how climate affects growth in tree species is essential for improved predictions of forest dynamics under climate change. Long-term climate averages (mean climate) drive spatial variations in species' baseline growth rates, whereas deviations from these averages over time (anomalies) can create growth variation around the local baseline. However, the rarity of long-term tree census data spanning climatic gradients has so far limited our understanding of their respective role, especially in tropical systems. Furthermore, tree growth sensitivity to climate is likely to vary widely among species, and the ecological strategies underlying these differences remain poorly understood. Here, we utilize an exceptional dataset of 49 years of growth data for 509 tree species across 23 tropical rainforest plots along a climatic gradient to examine how multiannual tree growth responds to both climate means and anomalies, and how species' functional traits mediate these growth responses to climate. We show that anomalous increases in atmospheric evaporative demand and solar radiation consistently reduced tree growth. Drier forests and fast-growing species were more sensitive to water stress anomalies. In addition, species traits related to water use and photosynthesis partly explained differences in growth sensitivity to both climate means and anomalies. Our study demonstrates that both climate means and anomalies shape tree growth in tropical forests and that species traits can provide insights into understanding these demographic responses to climate change, offering a promising way forward to forecast tropical forest dynamics under different climate trajectories.

AusTraits, a curated plant trait database for the Australian flora

We introduce the AusTraits database - a compilation of values of plant traits for taxa in the Australian flora (hereafter AusTraits). AusTraits synthesises data on 448 traits across 28,640 taxa from field campaigns, published literature, taxonomic monographs, and individual taxon descriptions. Traits vary in scope from physiological measures of performance (e.g. photosynthetic gas exchange, water-use efficiency) to morphological attributes (e.g. leaf area, seed mass, plant height) which link to aspects of ecological variation. AusTraits contains curated and harmonised individual- and species-level measurements coupled to, where available, contextual information on site properties and experimental conditions. This article provides information on version 3.0.2 of AusTraits which contains data for 997,808 trait-by-taxon combinations. We envision AusTraits as an ongoing collaborative initiative for easily archiving and sharing trait data, which also provides a template for other national or regional initiatives globally to fill persistent gaps in trait knowledge.

Applying the economic concept of profitability to leaves

Economic principles can be extended to biological organisms as they optimize the use of resources, but their use in biology has been limited. We applied concepts from traditional economics to the main production unit of plants, the leaf. We quantified the profitability (profit/cost of investment) of leaves from seven biomes worldwide and compared those to the profitability of companies. Here we demonstrate for the first time key similarities and differences between leaf and human economics. First, there was a weak, but positive relationship between profitability and size, both for leaves and companies. Second, environment has a strong effect on profitability, with high values in leaves from biomes with short growth periods and, for companies associated with innovation. Third, shorter longevity of productive units was related to higher profitability. In summary, by comparing economic behaviours of plants and humans there is potential to develop new perspectives on plant ecological strategies and plant evolution.

Convergent Variations in the Leaf Traits of Desert Plants

Convergence is commonly caused by environmental filtering, severe climatic conditions and local disturbance. The basic aim of the present study was to understand the pattern of leaf traits across diverse desert plant species in a common garden, in addition to determining the effect of plant life forms (PLF), such as herb, shrub and subshrub, phylogeny and soil properties on leaf traits. Six leaf traits, namely carbon (C), nitrogen (N), phosphorus (P), potassium (K), δ13C and leaf water potential (LWP) of 37 dominant desert plant species were investigated and analyzed. The C, N, K and δ13C concentrations in leaves of shrubs were found higher than herbs and subshrubs; however, P and LWP levels were higher in the leaves of subshrubs following herbs and shrubs. Moreover, leaf C showed a significant positive correlation with N and a negative correlation with δ13C. Leaf N exhibited a positive correlation with P. The relationship between soil and plant macro-elements was found generally insignificant but soil C and N exhibited a significant positive correlation with leaf P. Taxonomy showed a stronger effect on leaf C, N, P and δ13C than soil properties, explaining >50% of the total variability. C3 plants showed higher leaf C, N, P, K and LWP concentration than C4 plants, whereas C4 plants had higher δ13C than C3 plants. Legumes exhibited higher leaf C, N, K and LWP than nonlegumes, while nonlegumes had higher P and δ13C concentration than legumes. In all the species, significant phylogenetic signals (PS) were detected for C and N and nonsignificant PS for the rest of the leaf traits. In addition, these phylogenetic signals were found lower (K-value < 1), and the maximum K-value was noted for C (K = 0.35). The plants of common garden evolved and adapted themselves for their survival in the arid environment and showed convergent variations in their leaf traits. However, these variations were not phylogenetics-specific. Furthermore, marks of convergence found in leaf traits of the study area were most likely due to the environmental factors.

Why are tropical conifers disadvantaged in fertile soils? Comparison of Podocarpus guatemalensis with an angiosperm pioneer, Ficus insipida

Conifers are, for the most part, competitively excluded from tropical rainforests by angiosperms. Where they do occur, conifers often occupy sites that are relatively infertile. To gain insight into the physiological mechanisms by which angiosperms outcompete conifers in more productive sites, we grew seedlings of a tropical conifer (Podocarpus guatemalensis Standley) and an angiosperm pioneer (Ficus insipida Willd.) with and without added nutrients, supplied in the form of a slow-release fertilizer. At the conclusion of the experiment, the dry mass of P. guatemalensis seedlings in fertilized soil was approximately twofold larger than that of seedlings in unfertilized soil; on the other hand, the dry mass of F. insipida seedlings in fertilized soil was ~20-fold larger than seedlings in unfertilized soil. The higher relative growth rate of F. insipida was associated with a larger leaf area ratio and a higher photosynthetic rate per unit leaf area. Higher overall photosynthetic rates in F. insipida were associated with an approximately fivefold larger stomatal conductance than in P. guatemalensis. We surmise that a higher whole-plant hydraulic conductance in the vessel bearing angiosperm F. insipida enabled higher leaf area ratio and higher stomatal conductance per unit leaf area than in the tracheid bearing P. guatemalensis, which enabled F. insipida to capitalize on increased photosynthetic capacity driven by higher nitrogen availability in fertilized soil.