Posts Tagged ‘trees’

The Amazon contains 390 billion trees of 16,000 species (approximately)

October 19, 2013

Something to remember for your next game of Trivial Pursuit.

The Amazon contains 390 billion trees and 16,000 species and half the trees are accounted for by just 227 species.

Nobody actually counted them.

The ~6-million-km2 Amazonian lowlands were divided into 1° cells, and mean tree density was estimated for each cell by using a loess regression model that included no environmental data but had its basis exclusively in the geographic location of tree plots. A similar model, allied with a bootstrapping exercise to quantify sampling error, was used to generate estimated Amazon-wide abundances of the 4962 valid species in the data set. We estimated the total number of tree species in the Amazon by fitting the mean rank-abundance data to Fisher’s log-series distribution.

The data is generated by a mathematical model.  It is not clear how the 16,000 species is estimated from just 4,962 valid species. “This is very valuable information for further research and policymaking” says Hans ter Steege. It must be – after all a paper has been published in Science! According to the mathematical model roughly 6,000 tree species in the Amazon have populations of fewer than 1,000 individuals, which automatically qualifies them for inclusion in the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. But these species are so rare that scientists may never find them.

( I can’t help thinking that there must be very many species of tree coming to the end of their “natural” existence which we know nothing about. And does it matter?).

H. ter Steege et al, Hyperdominance in the Amazonian Tree FloraScience, 2013; 342 (6156): 1243092 DOI: 10.1126/science.1243092


A map of Amazonia showing the location of the 1430 Amazon Tree Diversity Network (ATDN) plots that contributed data to this paper.

Field Museum Press Release: 

Researchers, taxonomists, and students from The Field Museum and 88 other institutions around the world have provided new answers to two simple but long-standing questions about Amazonian diversity: How many trees are there in the Amazon, and how many tree species occur there? The study will be published October 17, 2013 in Science.

The vast extent and difficult terrain of the Amazon Basin (including parts of Brazil, Peru, Columbia) and the Guiana Shield (Guyana, Suriname, and French Guiana), which span an area roughly the size of the 48 contiguous North American states, has historically restricted the study of their extraordinarily diverse tree communities to local and regional scales. The lack of basic information about the Amazonian flora on a basin-wide scale has hindered Amazonian science and conservation efforts.

“In essence, this means that the largest pool of tropical carbon on Earth has been a black box for ecologists, and conservationists don’t know which Amazonian tree species face the most severe threats of extinction,” says Nigel Pitman, Robert O. Bass Visiting Scientist at The Field Museum in Chicago, and co-author on the study.

Now, however, over 100 experts have contributed data from 1,170 forestry surveys in all major forest types in the Amazon to generate the first basin-wide estimates of the abundance, frequency and spatial distribution of thousands of Amazonian trees.

Extrapolations from data compiled over a period of 10 years suggest that greater Amazonia, which includes the Amazon Basin and the Guiana Shield, harbors around 390 billion individual trees, including Brazil nut, chocolate, and açai berry trees.

“We think there are roughly 16,000 tree species in Amazonia, but the data also suggest that half of all the trees in the region belong to just 227 of those species! Thus, the most common species of trees in the Amazon now not only have a number, they also have a name. This is very valuable information for further research and policymaking,” says Hans ter Steege, first author on the study and researcher at the Naturalis Biodiversity Center in South Holland, Netherlands.

The authors termed these species “hyperdominants.” While the study suggests that hyperdominants – just 1.4 percent of all Amazonian tree species – account for roughly half of all carbon and ecosystem services in the Amazon, it also notes that almost none of the 227 hyperdominant species are consistently common across the Amazon. Instead, most dominate a region or forest type, such as swamps or upland forests.

The study also offers insights into the rarest tree species in the Amazon. According to the mathematical model used in the study, roughly 6,000 tree species in the Amazon have populations of fewer than 1,000 individuals, which automatically qualifies them for inclusion in the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. The problem, say the authors, is that these species are so rare that scientists may never find them.

Ecologist Miles Silman of Wake Forest University, another co-author of the paper, calls the phenomenon “dark biodiversity”.

“Just like physicists’ models tell them that dark matter accounts for much of the universe, our models tell us that species too rare to find account for much of the planet’s biodiversity. That’s a real problem for conservation, because the species at the greatest risk of extinction may disappear before we ever find them,” says Silman.

While the authors are confident that these hyperdominants also dominate the vast expanses of Amazonia where scientists have never set foot, they do not know why some species are hyperdominant and others are rare.

The authors note that a large number of hyperdominants – including Brazil nut, chocolate, rubber, and açai berry – have been used and cultivated for millennia by human populations in Amazonia.

“There’s a really interesting debate shaping up,” says Pitman, “between people who think that hyperdominant trees are common because pre-1492 indigenous groups farmed them, and people who think those trees were dominant long before humans ever arrived in the Americas.”

Are leaves redder this year? A sign of a hard winter to come?

October 13, 2013

Autumn in this part of the world (Sweden at 58.7000° N) is always a riot of colour. A kaleidescope with every possible shade of yellow and brown with a small splash of red. Never quite the dominating reds of New England but glorious in the late autumn sunlight. But this year I felt that there was much more red around than “usual”. A purely subjective perception of course and one which I put aside as being just the vagaries of visual memory.

Autumn October 13, 2013

Autumn October 13, 2013

But yesterday the local paper reported that this was a perception being shared by many others. Trees and bushes did seem to be redder than usual. And “reds”were  varying from deep rusts and maroons to bright scarlets and bleeding crimsons. But science did not really know why the colours might vary from year to year – just that they did vary.

Is it due just to how the weather has been through the summer?

Or is it because of the weather anticipated for the winter?

The three main pigments that color leaves are, chlorophyll (green), carotenoid (yellow, orange, and brown), and anthocyanin (red). Chlorophyll and carotenoid are always present in leaf cells. More sunlight means more chlorophyll and green summers. The reducing sunlight in autumn reduces the chlorophyll allowing the yellows and browns of carotenoid to show through more strongly. But high levels of sunlight may lead to an increase of anthocyanins.

In photosynthetic tissues (such as leaves and sometimes stems), anthocyanins have been shown to act as a “sunscreen”, protecting cells from high-light damage by absorbing blue-green and ultraviolet light, thereby protecting the tissues from photoinhibition, or high-light stress.

This summer of 2013 started late after a long winter and a very late spring. The number of sunshine hours have not been unusually high nor the amount of rain unusually low. Temperatures have not been particularly noteworthy. So just the number of sunshine hours seems inadequate as an explanation of the greater levels of red I perceive.

The Daily Green: Unlike the ever-present yellows that simply become unmasked when chlorophyll recedes, red pigments are actually created as a tree is going dormant. But why would a tree expend energy to produce a new pigment just as it’s hunkering down for the winter? And why do some trees make red pigments, when others don’t? Further, the reds of New England are so famous in part because they are unique to the new world. Why are European autumns so predominantly yellow? 

…… yellow trees are those that colonize open land first – so-called pioneer species that are tolerant of direct sunlight. Those that turn red are species that follow in the succession of species that come to dominate a landscape, and they tend to benefit from more protection from the sun. It’s not that the red leaves lack the yellow pigment; the red pigment is an addition, and in fall it is so intense that it masks the yellow, just as green does in summer. Those pioneer species are less susceptible to light damage, 

But why are European trees more yellow? It could be that falls there tend to be warmer and cloudier, so there was never any selective advantage for trees to evolve red pigments that would be protective of the sun.

According to the U.S. Forest Service:

A succession of warm, sunny days and cool, crisp but not freezing nights seems to bring about the most spectacular color displays. During these days, lots of sugars are produced in the leaf but the cool nights and the gradual closing of veins going into the leaf prevent these sugars from moving out. These conditions-lots of sugar and lots of light-spur production of the brilliant anthocyanin pigments, which tint reds, purples, and crimson. Because carotenoids are always present in leaves, the yellow and gold colors remain fairly constant from year to year.

So I don’t really know why the leaves look redder this autumn.  But I think trees may be better predictors of weather than we give them credit for. There are some signs that Europe may be in for another hard, long winter this year. Perhaps the trees already know this and are busy storing nutrients in their roots. Therefore they need more anthocyanin to allow them to do this.

The trees already know what to expect this winter. At least, that’s what I would like to think!

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