1. Earth has more than 60,000 known tree species.
Until recently, there was no thorough global census of tree species. But in April 2017, the results of a "huge scientific effort" were published in the Journal of Sustainable Forestry, along with a searchable online archive called GlobalTreeSearch.
The scientists behind this effort compiled data from museums, botanical gardens, agricultural centers and other sources, and concluded there are 60,065 tree species currently known to science. These range from from Abarema abbottii, a vulnerable limestone-bound tree found only in the Dominican Republic, to Zygophyllum kaschgaricum, a rare and poorly understood tree native to China and Kyrgyzstan.
Next up for this area of research is the Global Tree Assessment, which aims to assess the conservation status of all of the world's tree species by 2020.
2. More than half of all tree species exist only in a one country!
Aside from quantifying the biodiversity of trees, the 2017 census also highlights the need for details about where and how those 60,065 different species live. Nearly 58 percent of all tree species are single-country endemics, the study found, meaning each one naturally occurs only within the borders of a single nation.
Brazil, Colombia and Indonesia have the highest totals for endemic tree species, which makes sense given the overall biodiversity found in their native forests. "The countries with the most country-endemic tree species reflect broader plant diversity trends (Brazil, Australia, China) or islands where isolation has resulted in speciation (Madagascar, Papua New Guinea, Indonesia)," the study's authors write.
3.Trees didn't exist for the first 90 percent of Earth's history.
Earth is 4.5 billion years old, and plants may have colonized land as recently as 470 million years ago, most likely mosses and liverworts without deep roots. Vascular plants followed about 420 million years ago, but even for tens of millions of years after that, no plants grew more than about 3 feet (1 meter) off the ground.
4. Before trees, Earth was home to fungi that grew 26 feet tall.
From about 420 million to 370 million years ago, a mysterious genus of creatures named Prototaxites grew large trunks up to 3 feet (1 meter) wide and 26 feet (8 meters) in height. Scientists have long debated whether these were some kind of weird ancient trees, but a 2007 study concluded they were fungi, not plants.
"A 6-meter fungus would be odd enough in the modern world, but at least we are used to trees quite a bit bigger," study author and paleobotanist C. Kevin Boyce told New Scientist in 2007. "Plants at that time were a few feet tall, invertebrate animals were small, and there were no terrestrial vertebrates. This fossil would have been all the more striking in such a diminutive landscape."
5. The first known tree was a leafless, fern-like plant from New York
Several kinds of plants have evolved a tree form, or "arborescence," in the past 300 million years or so. It's a tricky step in plant evolution, requiring innovations like sturdy trunks to stay upright and strong vascular systems to pump up water and nutrients from the soil. The extra sunlight is worth it, though, prompting trees to evolve multiple times in history, a phenomenon called convergent evolution.
The earliest known tree is Wattieza, identified from 385 million-year-old fossils found in what's now New York. Part of a prehistoric plant family thought to be ancestors of ferns, it stood 26 feet (8 meters) tall and formed the first known forests. It may have lacked leaves, instead growing frond-like branches with "branchlets" resembling a bottlebrush (see illustration). It wasn't closely related to tree ferns, but did share their method of reproducing by spores, not seeds.
6. Scientists thought this dinosaur-era tree went extinct 150 million years ago--but then it was found growing wild in Australia
During the Jurassic Period, a genus of cone-bearing evergreen trees now named Wollemia lived on the supercontinent Gondwana. These ancient trees were long known only from the fossil record, and were thought to have been extinct for 150 million years — until 1994, when a few survivors of one species were found living in a temperate rainforest at Australia's Wollemia National Park.
That species, Wollemia nobilis, is often described as a living fossil. Only about 80 mature trees are left, plus some 300 seedlings and juveniles, and the species is listed as critically endangered by the International Union for Conservation of Nature.
While Wollemia nobilis is the last of its genus, there are also still other middle Mesozoic trees alive today. Ginkgo biloba, aka the ginkgo tree, dates back about 200 million years and has been called "the most ancient living tree."
7. Some trees emit chemicals that attract enemies of their enemies
Trees may look passive and helpless, but they're savvier than they seem. Not only can they produce chemicals to combat leaf-eating insects, for instance, but some also send airborne chemical signals to each other, apparently warning nearby trees to prepare for an insect attack. Research has shown that a wide range of trees and other plants become more resistant to insects after receiving these signals.
Trees' airborne signals can even convey information outside the plant kingdom. Some have been shown to attract predators and parasites that kill the insects, essentially letting an embattled tree call for backup. Research has mainly focused on chemicals that attract other arthropods, but as a 2013 study found, apple trees under attack by caterpillars release chemicals that attract caterpillar-eating birds.
8. Trees in a forest can 'talk' and share nutrients through an underground internet built by soil fungi.
Like most plants, trees have symbiotic relationships with mycorrhizal fungi that live on their roots. The fungi help trees absorb more water and nutrients from the soil, and trees repay the favor by sharing sugars from photosynthesis. But as a growing field of research shows, this mycorrhizal network also works on a much larger scale — sort of like an underground internet that connects entire forests.
The fungi link each tree to others nearby, forming a huge, forest-scale platform for communication and resource sharing. As University of British Columbia ecologist Suzanne Simard has found, these networks include older, larger hub trees (or "mother trees") that may be connected to hundreds of younger trees around them. "We have found that mother trees will send their excess carbon through the mycorrhizal network to the understory seedlings," Simard explained in a 2016 TED Talk, "and we've associated this with increased seedling survival by four times."
And, as Simard recently told CNN, mother trees may even help forests adapt to human-induced climate change, thanks to their "memory" of slower natural changes in past decades or centuries. "They've lived for a long time and they've lived through many fluctuations in climate. They curate that memory in the DNA," she said. "The DNA is encoded and has adapted through mutations to this environment. So that genetic code carries the code for variable climates coming up."
9. Most tree roots stay in the top 18 inches of soil, but they can also grow above ground or dive a few hundred feet deep.
Holding up a tree is a tall order, but it's often achieved by surprisingly shallow roots. Most trees don't have a taproot, and most tree roots lie in the top 18 inches of soil, where growing conditions tend to be best. More than half of a tree's roots usually grow in the top 6 inches of soil, but that lack of depth is offset by lateral growth: The root system of a mature oak, for example, can be hundreds of miles in length.
Still, tree roots vary widely based on species, soil and climate. Bald cypress grows along rivers and swamps, and some of its roots form exposed "knees" that supply air to underwater roots like a snorkel. Similar breathing tubes, called pneumatophores, are also found in the stilt roots of some mangrove trees, along with other adaptations like the ability to filter up to 90 percent of salt out of seawater.
On the other hand, some trees do extend remarkably deep underground. Certain types are more prone to grow a taproot — including hickory, oak, pine and walnut — especially in sandy, well-drained soils. Trees have been known to go more than 20 feet (6 meters) below the surface under ideal conditions, and a wild fig at South Africa's Echo Caves has reportedly reached a record root depth of 400 feet.
10. A large oak tree can consume about 100 gallons of water per day, and a giant sequoia can drink up to 500 gallons daily.
Many mature trees require a huge amount of water, which may be bad for drought-stricken orchards but is often good for people in general. Thirsty trees can limit flooding from heavy rain, especially in low-lying areas like river plains. By helping the ground absorb more water, and by holding soil together with their roots, trees can reduce the risk of erosion and property damage from flash floods.
A single mature oak, for example, is able to transpire more than 40,000 gallons of water in a year — meaning that's how much flows from its roots to its leaves, which release water as vapor back into the air. The rate of transpiration varies during the year, but 40,000 gallons averages out to 109 gallons per day. Larger trees move even more water: A giant sequoia, whose trunk may be 300 tall, can transpire 500 gallons a day. And since trees emit water vapor, large forests also help make it rain.
As a bonus, trees have a knack for soaking up soil pollutants, too. One sugar maple can remove 60 milligrams of cadmium, 140 mg of chromium and 5,200 mg of lead from the soil per year, and studies have shown farm runoff contains up to 88 percent less nitrate and 76 percent less phosphorus after flowing through a forest.
This article is republished from Treehugger--Sustainability for All blog.