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Data & Methods

Small island in Raja Ampat, West Papua, Indonesia
Rafflesia, Borneo

A simple method to estimate leaf size

Leaf size has considerable ecological relevance making it desirable to obtain leaf size estimations for as many species worldwide as possible. However, measuring leaf size is often time and labour intensive. We quantified scaling functions that estimate leaf size as product of leaf length, width and a leaf shape-specific correction factor. Our method presents a tractable solution to accurately estimate leaf size when only information on leaf length, width and shape is available. We see promise in applying our method to data from species descriptions, databases, field work and on herbarium vouchers, especially when non-destructive in-situ measurements are needed.

Schrader, J., Shi, P., Royer, D.L., Peppe, D.J., Gallagher, R. V., Li, Y., Wang, R., & Wright, I.J. (2021). Leaf size estimation based on leaf length, width and shape. Annals of Botany, 128, 395-406. doi: 10.1093/aob/mcab078

R package biogeom

biogeom can simulate and fit many shapes found in nature such as objects with radial or axial symmetry in a single plane. The package incorporates novel universal parametric equations that generate the profiles of bird eggs, flowers, linear and lanceolate leaves, seeds, starfish, and tree-rings, and three growth-rate equations that generate the profiles of ovate leaves and the ontogenetic growth curves of animals and plants. In addition, the package includes sigmoid curves derived from the three growth-rate equations, which can be used to model animal and plant growth trajectories and predict the times associated with maximum growth rate. ‘biogeom’ can quantify the intra- or interspecific similarity of natural outlines, and it provides quantitative information of shape and ontogenetic modification of shape with important ecological and evolutionary implications for the growth and form of the living world.

Shi, P., Gielis, J., Quinn, B.K., Ratkowsky, D.A., Schrader, J., Ruan, H., & Niinemets, Ü. (2022) biogeom: An R package for simulating and fitting natural shapes. Annals of the New York Academy of Sciences, 1516, 123-134. doi:

Raja Ampat tree dataset

This dataset yields detailed information on plant community structure and links incidence, abundance and functional trait data at different spatial scales on 60 islands in the Raja Ampat Archipelago, a remote and poorly studied region. This dataset is likely the first plant-island dataset for the study region, and provides important new information on species occurrences. I collected this dataset together with colleagues from the Papua State University in Manokwari, Indonesia.
The full dataset can be downloaded as supplementary material attached to the flowing paper:

Schrader, J., Moeljono, S., Tambing, J., Sattler, C., & Kreft, H. (2020). A new dataset on plant occurrences on small islands, including species abundances and functional traits across different spatial scales. Biodiversity Data Journal, 8, e55275. doi:10.3897/BDJ.8.e55275

In addition, species occurrence data is available in GBIF and trait data in TRY database.

Leaf area estimation – Leaf-IT

Leaf area is an important plant functional trait used in countless ecological studies. However, estimating leaf area can be complicated and involves the use of scanners and commercial software.
Together with a programmer, I developed the smartphone application Leaf-IT. Leaf- IT is free, designed for scientific purposes, and runs on Android 4 or higher. It estimates leaf area with high precision and accuracy. The app still has some limitations, especially in margin detection of damaged or complex leaf morphologies. We aim at progressively develop Leaf-IT further. If you encounter any problems with the app or have new ideas how Leaf-IT can be improved, please contact me.
Leaf-IT is available at Google Play Store. A full description to Leaf-IT can be found here:

Schrader, J., Pillar, G., & Kreft, H. (2017). Leaf-IT: An Android application for measuring leaf area. Ecology and Evolution, 7, 9731–9738. doi:10.1002/ece3.3485

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