Transformed trees! Drought changes the plumbing system of rainforest trees

Trees in tropical rainforests play an important role in the water balance of the planet. Every tree is like a fountain, drawing water up from the soil and putting it out into the atnosphere.

Just one large mature tree may transpire well over 100,000 litres of water a year.

Imagine how much water a forest of trees would put out into the atmosphere, and the importance of this in maintaining the local climate.

Yet, tropical rainforests in many part of the world are likely to face more frequent or more severe droughts due to climate change.

What is going happen to rainforest trees?

As part of Professor Susan Laurance´s research team at the James Cook University in Australia and collaborators University of Edinburgh and Imperial College in the UK, we set out to investigate how drought would affect rainforest trees.

But how does one go about studying changes in mature trees in a tropical forest?

The Daintree Drought Experiment

In 2015, Professor Susan Laurance established a large scale field experiment in the wet tropics of Australia to do just that.

In a preexisting 1-hectare rainforest monitoring plot in the dense lowland tropical rainforests of Cape Tribulation, northeast Queensland, Australia, Susan has set up the Daintree Drought experiment.

OutreachPics2

This setup includes an infrastructure of plastic sheets in the understorey of the rainforest which reduces the rainfall that gets into half hectare of rainforest to artificially create a drier dry season, while the other half a hectare obtains the normal amount of rain.

The purpose of the experiment is not to kill the trees, but to understand how trees are changing in the short term by simulating two years of drought in the field.

Specifically, we wanted to know if trees are changing in their ability to conduct water. In previous work, we showed how wood anatomy can reveal the strategies trees use to conduct water, and so we focused again on wood anatomy.

The wonderful advantage of this plot is also that it has a canopy crane that enables researchers to access the rainforest canopy. The crane allowed us to reach 30m up into the canopy to sample tree branches from four species of trees which we could find individuals of in both the drought-affected and non-drought affected areas of the forest.

StudySpecies

And from the cut ends of these branches, we made anatomical sections to examine more closely. We also examined some leaf features, such as leaf thickness, to see if there are any changes.

Traits

Inner transformations in trees

Our results have just been published in the journal Ecology and Evolution. Basically, we found that the trees were changing in their wood anatomy, consistent with the the fact that they have less water to use.

Some species developed smaller vessels.

VesselsSmaller

Others species showed a shrinkage in ground tissue (parenchyma tissues) in their wood, likely reflecting the use of water stores.

And one of the species even started to show blockages in their water conducting vessels.

Myristica occlussions

We also found thinner leaves in some of the drought-affected individuals.

We can conclude from our study is that mature rainforest trees can modify their anatomy to some degree as an adaptation to drought.

We do not know yet what is the limits of this plasticity, but the changes in the hydraulic properties of these trees would certainly reduce the ability of trees to transport water, and that would also mean the trees are less able to put out water into the atmosphere.

What we can speculate is that in the long term, if real and prolonged drought occurs, the reduced ability of trees to transport water may lead to local changes hydrological cycles, and ultimately changes in the forest vegetation.

We expect to get more insights on these issues with the ongoing Daintree Drought experiment.

References

Tng DYP, Apgaua DMG, Ishida YF, Mencuccunu M, Lloyd J, Laurance WF, Laurance SGW (Accepted) Rainforest trees respond to drought by modifying their hydraulic architecture. Ecology and Evolution doi.org/10.1002/ece3.4601

Apgaua DMG, Tng DYP, Cernusak LA, Cheesman AW, Santos RM, Edwards WJ, Laurance SGW (2017) Plant functional groups within a tropical forest exhibit different wood functional anatomy. Functional Ecology 31, 582-591.

Tng DYP, Apgaua DMG, Campbell MJ, Cox CJ, Crayn DM, Ishida FY, Laidlaw MJ, Liddell MJ, Seager M, Laurance SGW (2016) Vegetation and floristics of a lowland tropical rainforest in northeast Australia. Biodiversity Data Journal 4, e7599.

Laurance, S. (2015). A raincoat for a rainforest. Australasian Science, 36, 20–22.

Advertisements
Posted in Ecology, Plant Anatomy, Plant Morphology, Plant Science, Tropical Australia | Tagged , , , , , , , , , , , , , , | Leave a comment

The Knights among giant trees

Eucalyptus viminalis (White Knight)

Eucalyptus viminalis (White Knight)

It has been some time since I last visited Tasmania, but the memory of meeting giants (trees) there remain fresh in my memory.

To put it more accurately, emblazoned into my psyche.

Among the giants one could meet in Tasmania, the White Knights would certainly be among the most unforgettable, particularly because of the stunning white trunk that rises from the dark forest understorey and reaches towards the heavens.

Am very pleased therefore to write this post to accompany my recent popular article that has come out today in Tasmanian Geographic Issue 50.

For any of you who love big trees, the White Knights of Tasmania are a must-visit.

Posted in Giant Trees, Must see plants, Tasmanian plants | 2 Comments

Twitter and your Research Program: tweeting your publications

This is such an important post on Why and How scientists should tweet their reseach by Alex Smith (@Alex_Smith_Ants in Twitter, and also blogged by Stephen Heard) that I felt compelled to Press it.

via Twitter and your Research Program: tweeting your publications

 

Quote | Posted on by | Tagged , , , | Leave a comment

Meeting with Maya-caceae

Mayaca fluviatilis likely DSC_9627 (1)

Wading in a small shallow backwater rivulet in northern Bahia, Brazil, brought me to a plant family that I had never seen before – the Mayacaceae.

I had only managed to take a quick photo but back home I managed to identify the mysterious plant as Mayaca fluviatilis, or stream bogmoss – an aquatic plant that is widely distributed in the tropics and subtropics of the Americas.

It is well and truly a flowering plant, and is a close relative of the spiderworts (Commelinaceae) with spiderworts. However, the finely-structured mosslike stems does give it a resemblance to mosses.

The bog moss is also sought after by aquarists, and I can certainly understand why – it makes for a fine submerged plant in an aquarium.

One thing I have to say though, having come from Asia and also having lived in the northeastern parts of Australia – it is quite refreshing to be wading around in rivulents near mangroves without having to think about crocodiles.

Maybe this is a good excuse to get more involved with aquatic plants.

IMG_20180815_153900855

Mayaca was at the base of the mangrove roots, forming dark green mats. 

Posted in Aquatic Plants, Botany, Brazil | Tagged , , , | Leave a comment

Towers built on turd – the Tayloria mosses

pablo (3)

Tayloria gunnii, one of the more charismatic-looking mosses of Tasmania

The human-made structures that we know as towers must have been inspired by mosses.

Or maybe humans drew the idea for the design of towers from the superconscious, where the form of moss capsules are imprinted on the fabric of the ethers.

Metaphysical connotations aside, there is no denying the uncanny resemblance between the form of Tayloria moss capsules with the towers of man.

I made this association whilst stumbling upon three interesting species of mosses in Tasmania.

Tayloria gunnii in the image above looks like Seattle’s Space Needle tower, and it is not difficult to find simialr looking human-made structures that resemble Tayloria tasmanica below.

Tayloria tasmanica

Tayloria tasmanica is an uncommon moss found in the Tasmanian Wilderness World Heritage Area. The capsules resemble the Kuala Lumpur Tower. 

Everything else about these mosses are just as interesting, if not more.

These mosses belong to a family called the Splachnaceae (the namesake genus is Splachnum – commonly known as dung mosses)

Mosses from the Splachnaceae have a penchant for, and tend to grow on, animal poo. This feature is unique among mosses.

Unique point number two: these mosses are entomophilous, which mean that they are dispersed by insects – flies specifically. Unlike most other mosses that have wind disperse spores, these mosses have chemical means of attracting invertebrates to their capsules and in the process the flies “pick up” the sticky spores

Flies then go for poo, and the cycle is complete.

But these mosses are not restricted only to poo apparently.

One interesting piece of natural history comes from a historical collection of a Tayloria moss, which was made on the clothing of a decomposing human cadaver in the wilderness of Tasmania!

And I have seen some Tayloria mosses growing on a piece of animal bone.

Moss on bone

Tayloria octoblepharum on a piecce of animal bone

While the relationships between the northern hemisphere Splachnum mosses and fly dispersers are well established, those of Tayloria remain poorly studied.

I have not actually had any luck to observe a fly landing on the capsules of any of the Tayloria mosses I have seen.

Any keen students of plant-animal interactions to take on the challenge?

Two towers

Two towers! Tayloria gunnii growing amongst Tayloria octoblepharum.

References

See Awkward Botany’s blog post on the Splachnaceae

Posted in Appreciation, Botany, Mosses, Must see plants, Plant Curios, Plant Morphology, Tasmanian plants | Tagged , , , , , | Leave a comment

The metamorphosis of plants – a living example

FUCHSIA FLOWER parts

What is a flower actually?

How do they develop?

The subject of plant developmental is a very vibrant field of study, and in our modern age, scientists are using advanced molecular techniques and model species to pry into the secrets of how plant organs are formed.

Yet, what might come as a big surprise is that the basic idea of how flowers develop on a plant was actually conceived over two centuries ago in the brilliant mind of the famous German poet and philosopher Johann Wolfgang Goethe.

Goethe, in 1790, had no way of knowing the action of genes in the onset of flowering but his powers of observation would shame many a scientist today.

Mussaenda_CV_RUBIACEAE_061403_Sentosa

A cultivated Mussaenda. The white leaf-like structure is actually a modified leaf and not part of the flower itself.

He spent a lot of time observing the entire development of a date palm tree from seed to fruit and concluded that part of a plant represents a metamorphosis of the plant organ that we call a leaf.

His insights were discussed his very aptly titled essay: The Metamorphosis of Plants.

Even today in botany, we learn of how flowers consisting of 4 successive whorls: calyx (the whorl of sepals), corolla (the whorl of petals), male parts (the stamens) and female parts (the pistils).

In Goethe’s view, all these whorls of the flower can be interpreted as “leaves” made to fulfil another function – that of reproduction.

Some plants even modify leaves to make the real flowers look more obvious or attractive, such as Poinsettas and Mussaendas.

In Tasmania, I had the luck to experience the process of leaf to flower metamorphosis going the other way.

The Coral Heath (Epacris gunnii) is a common native Tasmanian shrub cultivated for its attractive sprays of flowers.

And in particular, there is a cultivated version of this species called a double form that produces small Camelia-like flowers.

Even though I knew that the aberration of genetic mechanism of these double form plants, I was still pretty surprised when I stumbled on this strange phenomena in an individual Coral Heath with a branch produce a ‘flower’ with a whorl of petals, and have a new shoot growing out of the whorl of petals.

But therein lies the genius of plants.

Just to be sure I even sliced the stem and ‘flower’ longitudinally to make sure and indeed, the new shoot just grew continuously out of the whorl of petals.

It is almost as thought the plant decided to make a flower but got sidetracked at the last minute and continued with vegetative shoot growth.

They transmutate.

They morph.

They make flowers from ‘leaves’.

And here it seems our aberrant Coral Heath, leaves from flowers.

References

Goethe, J. W. V. (1831). Essay on the metamorphosis of plants.

Posted in Botany, Early Botany, Plant Morphology, Tasmanian plants | Tagged , , , , , , , , , , , , | 2 Comments

Back to threads – the moss that is returning to an algae-like existence

Ephemeropsis trentepohlioides

A clump of the enigmatic moss Ephemeropsis trentepohlioides on a small tree branch in the wet forests of Tasmania. This clump measured no more than 2cm across

Algae needs water to reproduce, and anyone who has seen a pond or kept a fishtank has knows of the green thread-like algae that grows of submerged rock or wood surfaces.

So one of the major advances of mosses over alga was the development of leaves.

And indeed, many mosses have leaves with a diversity of form and shape almost comparable with flowering plants.

Yet one species of moss has seemingly decided to go back to being like an alga.

No leaves are to be found, but instead, the body of the moss is made up of single-celled wide thread-like green tissue resembling that of an alga. In moss-language, these “threads” are called protonema.

Ephemeropsis_trentepohloides_cropped

Closeup of the thread-like body of Ephemeropsis trentepohlioides

My first time seeing this moss was on a twig of a forest tree in Tasmania, where I was trained as a bryologist (i.e. a person who studies mosses and related plants).

And indeed, the Tasmanian species Ephemeropsis trentepohlioides is like a mass of alga threads (the specific epithet trentepohlioides alludes to the fact that it resembles the algae Trentepohlia)

This genus of moss, Ephemeropsis, is so called because it could scarcely be seen in the abscence of fruiting capsules.

But that narrow window of time when Ephemeropsis is fruiting is sufficient.

When mosses call – the moss lover answers.

Notes
Ephemeropsis is within the moss family Daltoniaceae. There is also a recent article by Thai botanists with great photos and drawings of Ephemeropsis tjibodensis.

Posted in Mosses, Must see plants, Plant Curios, Plant Morphology, Tasmanian plants | Tagged , , , , | Leave a comment