This is Scientific American — 60-Second Science. I'm Christopher Intagliata.
You've probably heard the financial advice that a diversified portfolio is better in turbulent times? Well that same wisdom may hold true for our stocks of trees. Because ecologists say forests with a diversity of trees are better at weathering drought. The reason:
"There's a huge difference and a huge diversity of water transport strategies in trees." William Anderegg is an ecologist at the University of Utah. "It's everything from having deeper roots or shallower roots, to having these pipes that are incredibly well armored to withstand drought or incredibly weak in the face of drought."
Anderegg and his team studied droughts in 40 forests around the world. And the forests with diverse tree populations, with a mix of water-management strategies, did better than forests made up of just one or a few species. Could be a couple reasons for that.
"One is that there are other forces that are acting on the ecosystem at the same time. Other stressors like insect attack, or other things they're competing for, competing for light and for nutrients, and this is why a more diverse forest is going to be more functional. It'll be more resilient to drought but maybe also have higher carbon uptake rates over the long term."
The second possibility, he says, is that a monoculture of drought-ready trees may look really resilient to drought. "Up until the drought is severe enough that a whole bunch of the trees shut down or even die. And so that really threshold cliff response you would get in a one species forest and you may not get in a diverse forest." The full report is in the journal Nature.
The lesson for land managers, he says, is that forest restoration efforts following wildfires and disease outbreaks might want to focus on planting a diverse portfolio of tree species. So that even if water plummets, tree stocks will, hopefully, remain stable.
Thanks for listening for Scientific American — 60-Second Science. I'm Christopher Intagliata.
你可能听过这样的理财建议：在动荡时期，多元投资组合会更好 。这种智慧同样适用于树木储备 。因为生态学家表示，树木多样化的森林更耐旱 。其原因是：
“就水分输送策略来说，不同树木之间存在极大的差异和多样性 。”犹他大学的生态学家威廉·安德莱格说到 。“有些树木根深，有些树木根浅，有的树木武装完备可以抵御干旱，其他树木却在面对干旱时不堪一击 。”
安德莱格及其团队研究了全球40个森林的干旱情况 。树木种群多样化且拥有不同水源管理策略的森林，其耐旱性要好于只有一个或几个树种的森林 。原因可能有以下两点 。
“其一，有其他力量在同时作用于生态系统 。其它压力源的存在，比如昆虫攻击或它们在竞争的其它元素，比如争夺光和养分等，这就是树种多样化的森林将会更强大的原因 。这种森林对干旱的适应性更强，不过从长远看，这种森林的碳吸收率或许会更高 。”
他说，第二种可能性是，单一栽培的抗旱树种可能看起来更具抗旱性 。“直到干旱严重到足以让大片树木停止运转甚至死亡 。因此，你可能会在单一树种森林看到这种临界点反应，但不会在多样树种森林中看到 。”完整报告发表在《自然》期刊上 。
他表示，土地管理者可从中得到的经验是，爆发野火和病害之后，森林恢复工作可能要重点关注树种的多样化种植 。这样一来，即使水分骤降，树木储备也有希望保持稳定 。
谢谢大家收听科学美国人——60秒科学 。我是克里斯托弗·因塔利亚塔 。
1. hold true 同样适用；在…情况下亦然；
This law is known to hold true for galaxies at a distance of at least several billion light years.
2. in the face of 面对；在…面前；
She showed great courage in the face of danger.
3. be made up of （由…）构成的；（由…）制成的；
Speech is made up of sound waves that vary in frequency and intensity.
4. shut down (使)(工厂、公司等)关闭,歇业，停业；
Venerable dailies such as the Tokyo Times have shut down.