We are honoured by the fact that algorithms of mobile application Petiole was used in the latest research of beech forest, carried by a group of Swiss scientists from the WSL.

Details about the Beech Forest Research by WSL

European Journal of Forest Research published a scientific article “Survival time and mortality rate of regeneration in the deep shade of a primeval beech forest”. The authors of this work are Roksolana Petrovska, Harald Bugmann, Martina L. Hobi, Shyamolina Ghosh and Peter Brang. They represent Swiss Federal Institute for Forest, Snow and Landscape Research.

Abstract of the Research

Low mortality rates and slow growth differentiate shade-tolerant from shade-intolerant species and define the survival strategy of juvenile trees growing in deep shade. While radial stem growth has been widely used to explain mortality in juvenile trees, the leaf area ratio (LAR), known to be a key component of shade tolerance, has been neglected so far.

We assessed the effects of LAR, radial stem growth and tree height on survival time and the age-specific mortality rate of juvenile Fagus sylvatica L. (European beech), Acer pseudoplatanus L. (sycamore maple) and Acer platanoides L. (Norway maple) in a primeval beech forest (Ukraine).

Aboveground and belowground biomass and radial stem growth were analysed for 289 living and 179 dead seedlings and saplings. Compared with the other species, F. sylvatica featured higher LAR, slower growth and a lower mortality rate. The average survival time of F. sylvatica juveniles (72 years) allows it to reach the canopy more often than its competitors in forests with low canopy turnover rate. In contrast, a combination of lower LAR, higher growth rate and higher age-specific mortality rate of the two Acer species resulted in their shorter survival times and thus render their presence in the canopy a rare event.

Overall, this study suggests that shade tolerance, commonly defined as a relationship between sapling mortality and growth, can alternatively be formulated as a relationship between survival time and the interplay of growth and leaf area ratio.

What is Leaf Area Ratio (LAR)?

Leaf Area Ratio (LAR) as the term has been firstly mentioned in the fundamental research " Growth Analysis Formulae: Their Use and Abuse" by Radford (1967). Leaf area ratio expresses the ratio between the area of leaf lamina to the total plant biomass

Leaf area estimates are required by hydrologic erosion, and growth or yield simulation models. They are important to the understanding of transpiration interception, CO2 fixation, and the energy balance for native plant communities.

How to calculate Leaf Area Ratio (LAR)?

To estimate Leaf Area Ratio (LAR) it is important to have the total leaf area measurements per plant in square centimetres and plant dry weight in grams. The main formula for Leaf Area Ratio (LAR) calculation is:

Leaf Area Ratio = Leaf area per plant / Plant dry weight

Petiole App to Help in Leaf Area Ratio Estimation

The Swiss ecologists used Petiole App to measure leaf area for further assessment of leaf area ratio (LAR) and directly mentioned this in their work:

All fresh leaves were scanned for leaf area with a smartphone (Petiole version 2.0.1, Petiole Ltd. 2019) after calibration of the camera.

Official credentials

Petrovska, R., Bugmann, H., Hobi, M.L. et al. Survival time and mortality rate of regeneration in the deep shade of a primeval beech forest. Eur J Forest Res (2021). https://doi.org/10.1007/s10342-021-01427-3

Received: 19 May 2021 Revised: 04 October 2021 Accepted: 21 October 2021 Published: 05 November 2021