Unraveling the secrets of mangrove development

Available SAS analytics code deployed in research project

The rather esoteric sounding research into the survival strategies of mangrove trees is in fact an environmental issue of
urgent worldwide importance. Nathalie Tonné, a PhD student at the Vrije Universiteit Brussel, is conducting just such
research into mangrove trees. Together with other members from her research team ANEMA (Anatomy and Ecophysiology
of Mangroves), Tonné is investigating the plant elements of mangrove forests unique to tropical and subtropical coastal
areas around the world. “Mangroves are critically important as a habitat for thousands of animal species. They also offer
vital natural protection against coastal storms,” she explains. “In recent years the worldwide mangrove population has been
under a growing threat due to human incursions. Attempts at reforestation and reintroduction of mangrove populations by
man have not been a consistent success.” Tonné uses SAS in her research to help unravel the complex secrets of mangrove
seedling development.

We believe that research on the development of mangrove seedlings will help us in improving replanting and reintroduction programs worldwide.

Nathalie Tonné
PhD student at the Vrije Universiteit Brussel

Trees that protect against coastal storms

Mangroves are small to medium-sized shrubs and trees that grow in the intertidal zone in the tropics and subtropics. These are physically and physiologically demanding environments for trees due to a number of key factors. These include high salt concentration in the soil water impeding water uptake and a tropical climate with high temperature and high relative air humidity counteracting the water transport. Other important factors include frequent seawater inundations and thus anaerobic conditions. There is an extreme dynamic in these environmental variables asking for a set of adaptations in order to guarantee continued water supply to the tree’s internal tissues. Large mangrove forests can be found along the coasts of South-East Asia, Australia, Africa, Central and South America and Florida.

The mangrove ecosystem worldwide is experiencing a serious decline, mostly due to deforestation for shrimp farming and other human activities.

World map of areas where  mangrove forests can be  found (© Wikipedia)
World map of areas where mangrove forests can be found (© Wikipedia)

“That’s bad news, because mangroves provide an ideal habitat for thousands of animal species, play an important role as fish nurseries, and are crucial in the protection of coral reefs and their related organisms against siltation,” reports Tonné. “In addition, mangroves are an important natural protective barrier against tsunamis and cyclones/hurricanes and other severe coastal storms. Disappearing mangrove forests make people living in these coastal areas far more vulnerable to the devastating effects of such meteorological, tidal and geological events. That’s why it’s important to protect the remaining mangrove forest stocks and launch programs to reintroduce it where it has been lost.”

VUB - Mangrove Forests
Mangrove forests in Florida (© Nathalie Tonné)

Research to improve replanting and reintroduction programs

However, a substantial number of the replanting and reintroduction programs launched in recent years have failed. The reasons for the failure are unknown or poorly understood at best. “Growing mangroves is not a straightforward affair,” explains Tonné. “They live under circumstances that no other woody plant can survive. They are unique in their ability to withstand a wide range of salinity values as well as live through extended periods of drought under tropical conditions, and facing frequent inundations by seawater. They thrive where all other woody plants fail. We understand some of the strategies they employ, for example that their roots filter seawater to reduce salinity, and that excess salt can be evacuated through shedding leaves. However, we know very little about the plant’s survival strategies in its early developmental stages. That’s why my research focuses on monitoring the development of settled mangrove seedlings or propagules, in order to better understand how they react to weather and other environmental factors. We believe that this will help us improve reforestation programs.”

VUB - Mangroves Dendrometer
Dendrometer measurements of a mangrove seedling (© Nathalie Tonné)

Dendrometer analysis in Florida

In January 2014, Tonné did fieldwork in Avalon State Park, Florida, a 650 acres undeveloped beachfront along the Atlantic Ocean, displaying rich mangrove vegetation. She used high-precision dendrometers to measure the variations in the radius of a number of mangrove seedlings and hence follow their development every ten minutes throughout an entire week.
“The variation in the radius of a mangrove seedling gives us an indication of the water relations within this young mangrove plant,” Tonné explains. “Our idea was to combine this information with data such as ambient temperature, relative humidity, water salinity, amount of rainfall, and time of day.”

Pattern analysis using SAS

Analysis was carried out using SAS. “We wanted to determine if there is a pattern in the fluctuations in mangrove seedling water content in relation to environmental factors, mainly rainfall and water salinity. Dendrometers give information about the radial

VUB - Pattern Analysis
Graph showing the similarities in the behavior of two seedlings in response to weather conditions (© Nathalie Tonné)

swelling and shrinking patterns of a plant, and therefore bring insight in the plant's internal water movement and storage patterns. I used SAS to analyze the data and establish concise water storage patterns for each of the studied seedlings. Analysis of two particular seedlings revealed striking similarities in the pattern of radial swelling and shrinking in response to rain. We are confident this will provide some of the fundamental building blocks to establish a seedling development model.”

Additional measurement campaigns carried out on mangrove seedlings under precisely monitored laboratory conditions have confirmed Tonné’s initial field study results.

A versatile tool

While further research is needed before any definitive conclusions can be drawn, Tonné confirms that reliable and versatile analysis software has been the key to the success of this research. “Using SAS was very convenient because they already had a code for dendrometer analysis. A scientist colleague had developed the code for SAS within the framework of a similar research project several years ago, and it enabled us to perform our data analysis in a far more timely and efficient manner. Without SAS, these types of analyses would be extremely time-consuming to carry out using traditional methods. This code saved us an enormous amount of time and vastly improved the reliability of our findings. Our SAS program made it much easier to detect and filter out anomalies, thus enabling me to evaluate and establish the reliability of the logged data and make our conclusions verifiable.”

Tonné is confident that the SAS code can be successfully used in other complex research projects as well. “It does not really matter whether you measure seedlings, trees or cereal crops,” she notes. “High-precision dendrometers can measure the development of any multicellular plant and the SAS code can be used for analyzing the results. I can envision using this tool in an enormous variety of contexts.”

Vrije Universiteit Brussel

Challenge

Analyzing dendrometer measurement data to uncover patterns in plant seedling behavior

Solution

SAS® Analytics Pro

Benefits

  • Quickly establish reliable plant behavior patterns based on comprehensive measurement data using available SAS analytics code
  • Easily detect and filter out measurement anomalies, making the end result more reliable
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