# Leaf Fresh Weight Versus Dry Weight: Which is Better for Describing the Scaling Relationship between Leaf Biomass and Leaf Area for Broad-Leaved Plants?

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## Abstract

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## 1. Introduction

_{2}, O

_{2}, and H

_{2}O), leaves must be as flat and thin as possible. However, if leaves are too thin and wide, they will quickly lose water. Thus, the foliar water content could balance leaf area against thickness [13]. Hughes et al. [14] reported that leaf area of several dicotyledonous genotypes was found to be an almost linear function of absolute leaf water content. Lin et al. [15] studied the scaling relationships between leaf fresh weight and area of 11 bamboo species. Because of the similarity of leaf shapes of the bamboos, the pooled data of 11 species showed a good linear relationship between the log-transformed leaf fresh weight and the log-transformed leaf area, and the estimate of the scaling exponent was 1.147 with 95% CIs (1.143, 1.152). Because work comparing the scaling relationship between leaf dry weight and area with that between leaf fresh weight and area is lacking, we still do not know (i) whether the scaling exponents based on two different biomass measures are the same or significantly different for broad-leaved plants, and (ii) which measure could exhibit a better scaling relationship on the condition that leaf fresh weight can be accurately measured for those plants. In the current study, we attempted to solve the above two questions using the plants of 15 species from three families (Lauraceae, Oleaceae, and Poaceae, subfamily Bambusoideae) that have broad and flat leaves, with ≥290 leaves for each species.

## 2. Materials and Methods

#### 2.1. Materials

#### 2.2. Experimental Methods

#### 2.3. Statistical Methods

## 3. Results

^{2}= 0.985), and the estimate of the scaling exponent approached one. Table S1 (Supplementary Materials) lists the detailed estimates of the parameters, the corresponding standard errors, and 95% confidence intervals. Figure 4a indicates that the leaf areas are significantly different among the 15 species with species 5 (i.e., P. sheareri) showing the largest leaves. Figure 4b provides a direct comparison of the ratio of leaf dry weight to fresh weight. We found that the intra-group difference in this ratio among the five Bambusoideae species was smaller than the inter-group differences of the family Lauraceae and especially of the family Oleaceae. Figure 4c provides a direct comparison of the ratio of leaf width to length. Here, we are mainly concerned with the intra-family difference in such a ratio. Species 5, 6, 9, 12, 13, and 14 (i.e., P. sheareri, F. viridissima, O. fragrans, B. multiplex, C. sichuanensis, and H. tranquillans, respectively) have the smallest leaf width/length ratio within the corresponding families to which those species belong.

^{2}= 0.869 in Figure 7b vs. R

^{2}= 0.601 in Figure 8b). The estimates of the scaling exponents of leaf fresh weight vs. leaf area for the 15 species of plants are all larger than one, which demonstrates the existence of “diminishing returns”. The derivative of leaf area to leaf fresh (or dry) weight is a decreasing function of leaf fresh (or dry) weight. However, the scaling exponent of leaf dry weight vs. leaf area might overemphasize diminishing returns.

## 4. Discussion

## 5. Conclusions

## Supplementary Materials

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## References

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**Figure 1.**Leaf examples of 15 species of plants: (

**a**) Cinnamomum camphora; (

**b**) C. chekiangense; (

**c**) Lindera angustifolia; (

**d**) Phoebe chekiangensis; (

**e**) P. sheareri; (

**f**) Forsythia viridissima; (

**g**) Ligustrum lucidum; (

**h**) L. sinense; (

**i**) Osmanthus fragrans; (

**j**) Syringa oblata var. alba; (

**k**) Bambusa emeiensis; (

**l**) B. multiplex; (

**m**) Chimonobambusa sichuanensis; (

**n**) Hibanobambusa tranquillans f. shiroshima; (

**o**) Indosasa sinica.

**Figure 2.**Scaling relationship of leaf dry weight to fresh weight at individual species level. Panels (

**a**–

**e**) belong to Lauraceae, panels (

**f**–

**j**) belong to Oleaceae, and panels (

**k**–

**o**) belong to Bambusoideae. In each panel, the open circles represent the observations, and the red straight line represents the reduced major axis regression line. Furthermore, y represents the natural logarithm of leaf dry weight in g, x represents the natural logarithm of leaf fresh weight in g, CI represents the 95% confidence interval of the slope, R

^{2}is the coefficient of determination used to measure the goodness of fit, and n represents the number of leaves sampled.

**Figure 3.**Scaling relationship of leaf dry weight to fresh weight for the pooled data of every family: (

**a**) Lauraceae; (

**b**) Oleaceae; (

**c**) Poaceae. In each panel, the colored points represent the observations, and the black dashed line represents the reduced major axis regression line. Furthermore, y represents the natural logarithm of leaf dry weight in g, x represents the natural logarithm of leaf fresh weight in g, CI represents the 95% confidence interval of the slope, R

^{2}is the coefficient of determination used to measure the goodness of fit, and n represents the total number of the sampled leaves for the five species of the same family. Different colored points represent different species in each panel, but points having the same color in different panels do not represent the same species.

**Figure 4.**Boxplots of leaf area (

**a**), the ratio of leaf dry weight to fresh weight (

**b**), and the ratio of leaf width to length (

**c**). The letters above the upper whiskers are used to show the significance of the difference between any two species. Species sharing the same letter indicate that there is no significant difference in the measure of interest. The scientific names associated with the corresponding species codes can be found in Table 1. The three colors from left to right represent Lauraceae, Oleaceae, and Bambusoideae.

**Figure 5.**Scaling relationship of leaf fresh weight to leaf area at individual species level. Panels (

**a**–

**e**) belong to Lauraceae, panels (

**f**–

**j**) belong to Oleaceae, and panels (

**k**–

**o**) belong to Bambusoideae. In each panel, the open circles represent the observations, and the red straight line represents the reduced major axis regression line. Furthermore, y represents the natural logarithm of leaf fresh weight in g, x represents the natural logarithm of leaf area in cm

^{2}, CI represents the 95% confidence interval of the slope, R

^{2}is the coefficient of determination used to measure the goodness of fit, and n represents the number of leaves sampled.

**Figure 6.**Scaling relationship of leaf dry weight to leaf area at individual species level. Panels (

**a**–

**e**) belong to Lauraceae, panels (

**f**–

**j**) belong to Oleaceae, and panels (

**k**–

**o**) belong to Bambusoideae. In each panel, the open circles represent the observations, and the red straight line represents the reduced major axis regression line. Furthermore, y represents the natural logarithm of leaf dry weight in g, x represents the natural logarithm of leaf area in cm

^{2}, CI represents the 95% confidence interval of the slope, R

^{2}is the coefficient of determination used to measure the goodness of fit, and n represents the number of leaves sampled.

**Figure 7.**Scaling relationship of leaf fresh weight to leaf area for the pooled data of every family: (

**a**) Lauraceae; (

**b**) Oleaceae; (

**c**) Poaceae. In each panel, the colored points represent the observations, and the black dashed line represents the reduced major axis regression line. Furthermore, y represents the natural logarithm of leaf fresh weight in g, x represents the natural logarithm of leaf area in cm

^{2}, CI represents the 95% confidence interval of the slope, R

^{2}is the coefficient of determination used to measure the goodness of fit, and n represents the total number of leaves sampled for the species of the same family. Different colored points represent different species in each panel, but the same colors in different panels do not represent the same species.

**Figure 8.**Scaling relationship of leaf dry weight to leaf area for the pooled data of every family: (

**a**) Lauraceae; (

**b**) Oleaceae; (

**c**) Poaceae. In each panel, the colored points represent the observations, and the black dashed line represents the reduced major axis regression line. Furthermore, y represents the natural logarithm of leaf dry weight in g, x represents the natural logarithm of leaf area in cm

^{2}, CI represents the 95% confidence interval of the slope, R

^{2}is the coefficient of determination used to measure the goodness of fit, and n represents the total number of leaves sampled for the species of the same family. Different colored points represent different species in each panel, but the same colors in different panels do not represent the same species.

**Figure 9.**Taylor’s power law for leaf dry weight of the 15 species of plants. The colored points represent the observations, and the black dashed line represents the reduced major axis regression line. The three colors represent the three families, and each point represents one species. Furthermore, y represents the natural logarithm of the variance of leaf dry weight in g, x represents the natural logarithm of the mean of leaf dry weight in g, CI represents the 95% confidence interval of the slope, R

^{2}is the coefficient of determination used to measure the goodness of fit, and n represents the number of data points (i.e., the pairs of means and variances of leaf dry weight for different species).

**Figure 10.**Gielis fit to the 15 leaf profiles: (

**a**) C. camphora; (

**b**) C. chekiangense; (

**c**) L. angustifolia; (

**d**) P. chekiangensis; (

**e**) P. sheareri; (

**f**) F. viridissima; (

**g**) L. lucidum; (

**h**) L. sinense; (

**i**) O. fragrans; (

**j**) S. oblata var. alba; (

**k**) B. emeiensis; (

**l**) B. multiplex; (

**m**) C. sichuanensis; (

**n**) H. tranguillans f. shiroshima; (

**o**) I. sinica. For every panel, the gray curve represents the scanned leaf profile, and the red curve represents the leaf profile predicted by the simplified Gielis equation. The leaves correspond to those in Figure 1.

**Table 1.**Leaf collection information of 15 species of plants that grow in Nanjing Forestry University campus, Nanjing, People’s Republic of China (32.08° north (N), 118.82° east (E)).

Species Code | Family | Scientific Name | Sampling Date | Sample Size |
---|---|---|---|---|

1 | Lauraceae | Cinnamomum camphora (L.) J. Presl | 1 September 2018 | 298 |

2 | Lauraceae | Cinnamomum chekiangense Nakai | 30 August 2018 | 299 |

3 | Lauraceae | Lindera angustifolia Cheng | 3 September 2018 | 306 |

4 | Lauraceae | Phoebe chekiangensis P.T. Li | 30 August, 2018 | 311 |

5 | Lauraceae | Phoebe sheareri (Hemsl.) Gamble | 4 September 2018 | 294 |

6 | Oleaceae | Forsythia viridissima Lindl. | 1 September 2018 | 311 |

7 | Oleaceae | Ligustrum lucidum W.T. Aiton | 2 September 2018 | 307 |

8 | Oleaceae | Ligustrum sinense Lour. | 2 September 2018 | 309 |

9 | Oleaceae | Osmanthus fragrans Lour. | 29 August 2018 | 297 |

10 | Oleaceae | Syringa oblata Lindl. var. alba Rehder | 28 August 2018 | 320 |

11 | Bambusoideae | Bambusa emeiensis ‘Viridiflavus’ Hsuen et Yi | 20 June 2018 | 315 |

12 | Bambusoideae | Bambusa multiplex (Lour.) Raeusch. ex Schult. & Schult.f. | 19 June 2018 | 310 |

13 | Bambusoideae | Chimonobambusa sichuanensis (T.P. Yi) T.H. Wen | 31 May 2018 | 310 |

14 | Bambusoideae | Hibanobambusa tranquillans f. shiroshima H. Okamura | 10 June 2018 | 299 |

15 | Bambusoideae | Indosasa sinica C.D. Chu & C.S. Chao | 7 June 2018 | 312 |

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**MDPI and ACS Style**

Huang, W.; Ratkowsky, D.A.; Hui, C.; Wang, P.; Su, J.; Shi, P.
Leaf Fresh Weight Versus Dry Weight: Which is Better for Describing the Scaling Relationship between Leaf Biomass and Leaf Area for Broad-Leaved Plants? *Forests* **2019**, *10*, 256.
https://doi.org/10.3390/f10030256

**AMA Style**

Huang W, Ratkowsky DA, Hui C, Wang P, Su J, Shi P.
Leaf Fresh Weight Versus Dry Weight: Which is Better for Describing the Scaling Relationship between Leaf Biomass and Leaf Area for Broad-Leaved Plants? *Forests*. 2019; 10(3):256.
https://doi.org/10.3390/f10030256

**Chicago/Turabian Style**

Huang, Weiwei, David A. Ratkowsky, Cang Hui, Ping Wang, Jialu Su, and Peijian Shi.
2019. "Leaf Fresh Weight Versus Dry Weight: Which is Better for Describing the Scaling Relationship between Leaf Biomass and Leaf Area for Broad-Leaved Plants?" *Forests* 10, no. 3: 256.
https://doi.org/10.3390/f10030256