Ferry slik

My research focuses on trying to understand spatial and temporal patterns in plant distributions. I do this with the help of  remote sensing (GIS), molecular techniques and spatial and temporal modeling. One of my main research themes is how global change will affect plant communities and vegetation patterns. Based on this I try to design optimum conservation strategies that integrate economic and social development with environmental sustainability.

Most of the research is focused on tropical Asia, one of the fastest developing and changing tropical regions in the world. Its once continuous tropical forests are now fragmented and mostly degraded.  These changes have put enormous pressures on tropical Asia’s natural ecosystems.  My aim is to study these changes and try to find ways to maintain or restore the functions of tropical Asia’s natural ecosystems.

Tree -diversity model for Borneo

Plant geography and Conservation lab

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Sampling tiny plants (August 2015)

How many people do you know that study plants that don’t get bigger than a few cm? Not many I guess! UBD’s Shengbin Chen did just that by studying the diversity patterns of mosses and liverworts in China and found some worrying and interesting results.

Lets start with the bad news….. Many of the former bryophyte (general name of mosses and liverworts) surveys did not have enough sampling effort to correctly estimate total diversity of a site, meaning that their diversity estimates were generally too low. Studies using these raw data to relate diversity to environmental variables therefore did not produce robust models.

Now the good news….. Shengbin managed to correct for this sampling bias with a relatively simple procedure. His corrected diversity values produced much stronger correlations with the environment while the models describing these relationships were different from former studies using the uncorrected data.

It turned out that liverwort richness is mainly determined by water availability, while moss richness depends more on available energy. Many more interesting findings are presented in the paper.

You can find them here.

Looking the same but being different (September 2015)

Tropical dry forests and savannas look more or less the same all over the world. They are dominated by shrubby trees and grasses that are exceptionally well adapted to long periods of drought. If you would be randomly dropped in one of the worlds savannas, you might have a hard time finding out where exactly you are…..

That is, unless you know the plants. A new study by Kyle Dexter shows convincingly that unlike what many people thought, the savannas on each of the tropical continents have their own specific flora, which is more related to the local wet forests than to any of the other savannas around the world! This indicates that these savannas have all developed locally and don’t form a global biome.

This has important consequences for how we deal with dry forest and savanna conservation because it may mean that what works in one place may not necessarily work in other places! This study again shows how little we still know about some of the worlds most extensive ecosystems, and how important it is that people keep going out to set up monitoring stations and plots all over the world.

For more information go here.

Hold on to the first tree you meet (October 2015)

Lianas climb trees, but how do they decide which tree? Is it something in the bark characteristics that makes them decide to grow on a specific tree, or something with the tree diameter or species? Mareike Roeder wanted to know so she embarked on a intensive analysis of her huge liana data set collected in southwestern China.

It turns out that most lianas just climb onto the first tree they find, which is generally the tree growing closest to where the liana germinated. All other tested variables only influenced liana host choice minimally. Apparently lianas are not that picky in host selection, anything that helps them grow skyward will suffice.

So when you walk through tropical forests, and you wonder why some trees have lianas and others don’t, you can stop wondering whether it depends on the tree. It just means that a liana germinated close to the infected tree at some point in time…..

For more details you can go here.

Mosses are no trees (November 2015)

This seems rather obvious by just looking at them, but now Shengbin Chen has also shown that the diversity patterns of the two groups of plants are different. Trees show a very nice latitudinal gradient, with highest diversity near the equator and lowest diversity near the poles. For mosses and liverworts the picture is slightly more complicated because they showed no or only very weak latitudinal diversity gradients. Instead, most of the diversity patterns in mosses and liverworts is explained by contemporary environmental conditions.

This finding seems to confirm a long standing hypothesis that due the abundant production of easily dispersed spores by mosses and liverworts, they can reach almost any place with ease. However, survival is not equal in all habitats, resulting in a spatial diversity pattern that reflects current habitat preference rather than historical biogeographic factors.

Another interesting outcome of the study was that tree diversity is mostly shaped by temperature, while moss and especially liverwort diversity shows a strong relationship with rainfall patterns. This difference reflects the more efficient water use of modern woody plants, compared to the mosses and liverworts which miss the woody plant vascular system

For more info go here.

A brand new 15-ha large tree plot (December 2015)

After a year of hard work our first plot within the Brunei forest observatory is ready! And it is not just any plot, it’s a 15-ha plot, consisting of 375 subplots of 20 x 20 m. Within it we have identified and measured all trees with a diameter of more than 50 cm, the so called ‘giant trees’! In total we found 554 of such trees in the plot and they store almost half of the biomass in this patch of forest.

You may ask why we did all this work….. Well, there is considerable debate whether tropical forests are currently increasing their carbon storage or not. These kind of changes have so far mostly been measured in small 1-ha plots that only contain a few large trees. However, since up to half of the forest biomass is stored in these few trees, getting some reliable estimates of their dynamics is critical. This is why we decided to build a plot specifically for measuring and monitoring these giant trees.

The plot contains two ridges (red and green in the picture on the right), a river valley and a swampy part (the blue in the picture). It covers an elevational gradient of ca. 50 m. The soil in the plot mostly consists of coarse sands and is very poor in nutrients and acidic. Despite this, initial tree inventories indicate that it is probably one of the most diverse plots in the world.

I would like to invite anyone interested in tropical forests to come and make use of this plot for their research!

How heavy is this forest? (January 2016)

Trees are heavy, and many trees are enormously heavy. Forests on Borneo for example can weigh up to 700,000 kg per hectare. About half of that weight is pure carbon, which, when in the atmosphere, causes global warming. If forests are cut or burned, this is indeed what happens because the trees are decomposed into carbon dioxide that ends up in the atmosphere.

Because so much forest is currently disappearing, it is important to know how much carbon this forest loss contributes to the atmosphere. To know this you need accurate maps with forest weight (or biomass). This is exactly what Valerio Avitabile has done. He combined two extisting pantropical forest carbon maps with biomass data from hundreds of forest plots to make a combined forest biomass map with unprecedented accuracy.

From now on we know exactly where and how much carbon is stored in tropical forests, so that if forest loss is detected, we also know how much carbon has been released to the atmosphere.

To read more, go here.

Plant diversity of China  (February 2016)

In a new study by Ming-Gang Zhang, millions of collections from Chinese herbaria have been combined into a plant diversity map of China using a technique called ‘species distribution modeling’. This method determines the habitat niche of individual species based on the conditions observed in the locations where they have been collected. Based on these climate and soil niches it becomes possible to predict where species can be found.

If this is done for many species, as in this case, a species diversity map can be produced by adding all species models together (see map on the right). The result shows that the south of China is very diverse in plant species. Unfortunately, most of these areas no longer have their natural vegetation because of agricultural expansion.

However, the map can serve to help delineate special regions that still have their original vegetation, and may thus be useful for improving China’s protected forest system.

For more on this, go here.

Solving three riddles  (April 2016)

Joeri strijk (Guangxi University, China) visited Brunei for two weeks to study three of the most common, but surprisingly also least understood tree families in Asia: the tropical oaks (Fagaceae), laurels (Lauraceae) and meranti’s (Dipterocarpaceae). These three families of mostly trees dominate most forests in Asia, but we know almost nothing about their evolution and biogeography.

There are about 700 species of tropical oaks, but recent studies based on DNA comparisons suggest there may be many more! The laurels are even worse because it turns out that most of the subdivisions in this family are wrong and need to be redefined. The meranti’s, despite their economic importance as timber trees, still remain an evolutionary puzzle as no one knows for sure which species should be grouped together.

During his visit to Brunei, Joeri will make a first step to solve these three riddles using whole genome sequencing techniques.

Arthropod soup for conservation (May 2016)

Kingsly Beng has passed his PhD-defense on arthropod soup for conservation! He collected leaf litter arthropods from 70 paired sites (rubber plantation versus forest & tea plantation versus forest) in Xishuangbanna (Yunnan, China) to see how arthropods respond to landuse change.

In principle, arthropods are very useful for detecting change because they are everywhere, and there are so many of them. In fact, so many that identification based on just visual characteristics is challenging and time consuming. This has hampered their use as environmental indicators in the tropics.

Kingsly Beng circumvented this problem by grinding all arthropods from each site into an arthropod DNA-soup, sequencing the soup, and then grouping the DNA-sequences into taxonomic units using a 97% similarity measure. These DNA-sequences could also be assigned to arthropod orders, making it possible to study both the change in diversity and composition of arthropods due to different land use types.

If you are interested in the methods and outcomes, please read here.

Introducing the new UBD herbarium team! (June 2016)

Since June this year, eight student volunteers have joined the UBD herbarium. We are now georeferencing, databasing and photographing all specimens in our collections, as well as adding about 2000 new species of plants collected in East Kalimantan, Indonesia. It’s a great and fun team!!

Stormy days (July 2016)

Most cyclone studies come from the Caribbean region, where forests are hit by such storms once every few decades. In the Philippines, however, forests can be hit by as many as four cyclones per year! They therefore form a perfect natural experiment to test the impact of storm frequency on tropical forests.

Carla Monoy did just that by using data from the Palanan long term forest dynamics plot (which is hit by several cyclones per year) to study how cyclone severity and frequency affected the forest.

She found that over a 16 year period and several direct hits by cyclones, the forest does not change much at all and seems very well adapted to cope with cyclones. An important finding was that individual cyclone severity seems more important than cyclone frequency in relation to forest damage. This information may be useful to predict what may happen to these forests if cyclone severity or frequency changes due to increasing air and ocean temperatures.

If you are interested to get the details, look here.

UBD Botanical Garden (September 2016)

Since two years, Universiti Brunei Darussalam has a botanical and medicinal garden. This garden includes a shade-house where we store useful plants from Brunei, a demonstration garden where we grow all useful woody plants, and a forest area consisting of Keranga forest. The latter is full of pitcher plants and other interesting white sand species

We are currently databasing, photographing and locating (with GPS) all the plants in the garden, starting with the shade house. This work is done by Nora Sawal (in the picture on the right), with the help of two gardeners. Our latest additions were the Nipa palm and Rhizophora (a mangrove tree), which we planted in the pond inside the shade house.

Everybody is welcome to visit, entrance free!!!!

Diversity does not equal more biomass in tropical forests (February 2017)

Several studies in temperate grasslands have shown that an increase in diversity leads to in increase in vegetation biomass, possibly because a more diverse set of species can more efficiently use the available nutrients in the soil. Since these publications people have been wondering if this would also hold for tree communities, especially in the tropics.

It turns out that this is most likely not the case according to a pan-tropical study carried out by Martin Sullivan. Using a large database of forest inventories, and correcting for differences in biogeography, climates and soils, no relationship between tree diversity and forest biomass could be detected.

The patterns found in the temperate regions probably relate to biomass productivity (grasses are annual plants, so biomass likely reflects productivity). For long lived and heavy (in biomass) organisms like trees, productivity is only a fraction of total standing biomass, which may explain that no pattern was detected here.

For more details, take a look here.