Abstract
Key messageA highly significant and positive scaling relationship between bamboo leaf dry mass and leaf surface area was observed; leaf shape (here, represented by the quotient of leaf width and length) had a significant influence on the scaling exponent of leaf dry mass vs. area.ContextThe scaling of leaf dry mass vs. leaf area is important for understanding how plants effectively intercept sunlight and invest carbon to do so. However, comparatively few, if any, studies have focused on whether leaf shape influences this scaling relationship.AimsIn order to explore the effects of leaf shape on the scaling relationship between leaf dry mass and area, we examined 101 species, varieties, forms, and cultivars of bamboo growing in China and identified the relationship between the scaling exponent of leaf dry mass vs. area and leaf shape. This taxon was used because its leaf shape is conserved across species and, therefore, easily quantified.MethodsTen thousand and forty-five leaves from 101 bamboo species, varieties, forms, and cultivars growing in China were collected, and leaf dry mass, the quotient of leaf width and length, leaf area, and leaf dry mass per unit area were measured. The effect of leaf shape that can be easily quantified using the quotient of leaf width and length on the relevant and ecologically important scaling exponents was explored using this data base.ResultsLeaf dry mass and area differed significantly across bamboo genera, and even within the same genus. However, a statistically robust log-log linear and positive scaling relationship was observed for mass and area with a 1.115 scaling exponent (95% CI = 1.107, 1.122; r2 = 0.907). Leaf shape had a significant influence on the numerical values of the scaling exponent of leaf dry mass vs. area. When the median of the quotient of leaf width and length was below 0.125, the numerical value of the scaling exponent increased with increasing quotient of leaf width and length. When the median of the quotient of leaf width and length was above 0.125, the scaling exponent numerically decreased toward 1.0.ConclusionWe show, for the first time, that a significant relationship exists between leaf shape and the numerical values of scaling exponents governing the scaling of leaf dry mass with respect to leaf area. In addition, we show that with the quotient of leaf width and length increasing mean LMA increases, which implies a negative correlation between mean LMA and the estimated exponent of leaf dry mass vs. area for the grouped data based on the sorted quotients of leaf width and length.
Highlights
Previous studies have focused primarily on morphological and anatomical structure (Wright et al 2004a, 2005a, b; Niklas and Christianson 2011), most workers have largely neglected the relationship between leaf mass and area in tandem with lamina shape. Using these attributes of bamboo leaves, we address three important questions: (i) what is the relationship between the M vs. A scaling exponent and leaf shape, (ii) what is the scaling relationship between leaf mass and area among species, and (iii) do the scaling exponents of M vs. A significantly differ across species
The following protocol was used to examine the effect of leaf shape, defined as the quotient of leaf width and length (W/L), on the scaling exponent of leaf dry mass vs. area: (i) the pooled W/L data were sorted in increasing order and divided into v quantiles, where v is an integer set at 4, 8, 12, and 16; (ii) the log-transformed data of leaf dry mass and area associated with each quantile group was regressed to obtain the estimates of the scaling exponent for each quantile; and (iii) a scatterplot of the estimates of the scaling exponent versus the medians of W/L of the v quantiles was prepared and examined
It is well known that the values of Leaf dry mass per unit area (LMA) and density in broad-leaved species are greater in more arid environments (Niinemets 2001) and that long-lived leaves have higher LMA than short-lived leaves (Mediavilla et al 2001), the data presented here show that these relationships may be correlated with leaf shape
Summary
The relationship between plants and their environment has always been a focus of ecological investigation since the time of Darwin (1871; see Shipley 1995; Poorter and Evans 1998; Díaz and Cabido 2001; Norby and Luo 2004; Shipley et al 2006), and such plant-environment interactions can result in adaptive plant strategies reflected in morphology, anatomy, and physiology (Niklas 1999, 2000; Díaz and Cabido 2001; Vendramini et al 2002). Leaf traits mainly include lifespan (Reich et al 1991, 1992; Wright and Westoby 2002), lamina length and width, leaf dry weight, and leaf shape (e.g., the quotient of leaf width and length) (Reich et al 1998; Aranda et al 2004; Poorter et al 2009; Shi et al 2019a, b) Many of these functional traits reflect the adaptability of plants to cope with different environmental gradients, and provide measured and observed links between various environmental factors and metabolic activity (Ellsworth and Reich 1993; Schulze et al 1994; Reich et al 1998; Kikuzawa and Ackerly 2002; Wright et al 2004a). This phenomenon has been referred to as “diminishing returns” (Niklas et al 2007)
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