Spatial distribution and functional significance of leaf lamina shape in Amazonian forest trees

Abstract

Abstract. Leaves in tropical forests come in an enormous variety of sizes and shapes, each of which can be ultimately viewed as an adaptation to the complex problem of optimising the capture of light for photosynthesis. However, the fact that many different shape "strategies" coexist within a habitat demonstrate that there are many other intrinsic and extrinsic factors involved, such as the differential investment in support tissues required for different leaf lamina shapes. Here, we take a macrogeographic approach to understanding the function of different lamina shape categories. Specifically, we use 106 permanent plots spread across the Amazon rainforest basin to: (1) describe the geographic distribution of some simple metrics of lamina shape in plots from across Amazonia, and; (2) identify and quantify relationships between key environmental parameters and lamina shape in tropical forests. Because the plots are not randomly distributed across the study area, achieving this latter objective requires the use of statistics that can account for spatial auto-correlation. We found that between 60–70% of the 2791 species and 83 908 individual trees in the dataset could be classified as elliptic (=the widest part of a leaf is on an axis in the middle fifth of the long axis of the leaf). Furthermore, the average Amazonian tree leaf is 2.5 times longer than it is wide and has an entire margin. Contrary to theoretical expectations we found little support for the hypothesis that narrow leaves are an adaptation to dry conditions and low nutrient soils. However, we did find strong regional patterns in leaf lamina length-width ratios and several significant correlations with precipitation variables suggesting that water availability may be exerting an as yet unrecognised selective pressure on leaf shape of rainforest trees. Furthermore, we found a strong correlation between the proportion of trees with non-entire laminas (dissected, toothed, etc.) and mean annual temperature once again supporting the well documented association that provides a basis for reconstructing past temperature regimes.

Quantification and characterization of vegetation and functional trait diversity of the riparian zones in protected forest of Kashmir Himalaya, India

“…Our findings are comparable with those of Qadir and Tareen (1987), Greller (1988), Malik et al (2007), Asim et al (2016) and Haq et al (2018) who reported the dominance of similar leaf size spectra in their study areas. The leaf lamina structure represents a solution to the complex 'problem' of optimizing light capture and water loss while minimizing unnecessary energy expenditure in the production of leaf structures (Malhado et al 2009). Environmental pressures influence the evolution of both leaf size and shape as moisture retaining is critical when the root system is subjected to low temperatures resulting in a decrease of water and nutrient absorption from the soil (Givnish 1978).…”

Functional trait variation and sampling strategies in species‐rich plant communities

“…For many research questions, it is essential to be able to calculate community-level means accurately (Table 1). For example, understanding the links between climatic factors, vegetation types and ecosystem services requires a functional description of a large number of vegetation types across a climatic gradient (Wright et al 2005;Cornwell et al 2008;Malhado et al 2009). An accurate estimation of the community-wide variance in functional traits is also often informative.…”

Spatial trends in leaf size of Amazonian rainforest trees

“…Here, to aid direct comparisons with these studies (including a variety of leaf traits -e.g. Malhado et al, 2009), we follow the practice of splitting the Amazon into four main regions: Region 1, North Amazonia, containing plots from Guyana, Suriname and Venezuela; Region 2, Northwest Amazonia, containing plots from Ecuador, Colombia, and North Peru; Region 3, Central and East Amazonia, all Brazilian plots (states of Amazonas and Pará only); Region 4, Southwest Amazonia, containing plots from Bolivia and South Peru. The regional distribution of leaf size might be affected by the distribution of the largest family, the Fabaceae, so analyses were repeated both with the Fabaceae removed dataset and within the Fabaceae dataset.…”