科学美国人60秒 SSS 森林起火引发北方气候谜团(1)（在线收听）

This is 60 Second Science, I’m Emily Schwing.

这里是60秒科学，我是艾米丽·施温。

The boreal forest is the largest terrestrial biome in the world. It covers 14 percent of the land on earth.

北方森林是世界上最大的陆地生物群落。 它占地球陆地面积的14%。

And, today, I’m here with my dogs on the north side of Denali National Park and Preserve.

今天，我和我的狗狗们来到了德纳里国家公园和保护区的北边。

I’m walking my dogs through the boreal forest.

我带着我的狗穿过北方森林。

It’s also known as taiga that covers 1.3 billion acres of the earth's surface.

它也被称为针叶林，其覆盖了地球表面13亿英亩的面积。

This forest is actually really beautiful.

这片森林美轮美奂。

There’s these black spruce trees....

这是黑云杉树林....

They’re stumpy, sometimes really short and goring in different directions.

这些树木粗短，有时非常短，而且朝不同的方向生长。

There’s lichen that hangs off of the dead branches, bright green lichen.

枯枝上布满青苔，鲜绿色的青苔。

Today, there’s a skim of snow on the ground overtop of this feather moss that just covers the forest floor.

今天，一层飞雪覆盖在羽毛苔藓上，下面覆盖着森林地面。

There's a magpie on a tree branch right in front of me....

在我面前的树枝上有一只喜鹊....

Wildfire is a normal part of the lifecycle for a boreal forest, but as the climate warms, this ecosystem is becoming increasingly vulnerable.

野火是北方森林生命周期中正常的一部分，但随着气候变暖，这个生态系统变得越来越脆弱。

That vulnerability risks turning this forest from carbon sink into a carbon source.

这种脆弱性有可能使这片森林从碳转变成成碳源。

When the boreal forest burns, it has the potential to release gigatons of carbon into the atmosphere.

当北方森林燃烧时，它有可能向大气中释放数十亿吨的碳。

Much of that carbon is actually in the forest floor.

大部分的碳实际上都在森林的地面上。

Jill Johnstone has been studying boreal forest ecology for decades.

吉尔·约翰斯通几十年来一直在研究北方森林生态学。

She does research through Canada’s Yukon University, and with the University of Alaska, Fairbanks.

她在加拿大育空大学和阿拉斯加费尔班克斯大学进行研究。

It's this undecomposed plant remains that accumulate through time.

这些未分解的植物残渣会随着时间积累。

And when a fire comes through the forest, it can just singe the surface of those accumulated plant remains, or it can burn deeply into them like a severe burn combusts most of that forest floor.

当一场大火穿过森林时，它只会烧焦那些堆积的植物残渣的表面，或者它可以像严重的起火一样深深地燃烧进森林的大部分地面。

That results in a pulse of released carbon into the atmosphere in the form of smoke and other aerosols and small carbon dioxide molecules.

其结果是碳以烟雾、其他气溶胶和二氧化碳小分子的形式释放到大气中。

And so that carbon is essentially lost from storage that burns away.

所以碳本质上是在储存过程中消耗掉的。

This past spring, a group of scientists released their findings from a 15-year study that looked at how boreal forests regenerate after wildfire.

今年春天，一组科学家公布了他们对北方森林野火后如何再生的15年研究的发现。

Johnstone was a co-author.

约翰斯通是作者之一。

Well, one of the things that we've been noticing in the past couple of decades is that fires are burning differently in the boreal forest than we understand them to have burned in the past.

在过去的几十年里，我们注意到的一件事是，在北方森林中燃烧的大火与我们过去所理解的不同。

And as a result of that, how the forest regenerates is changing.

因此，森林再生的方式也在改变。

Black spruce and fir are the dominant tree species in the boreal forest.

黑云杉和冷杉是北方森林的优势树种。

These trees are coniferous. They’re good at withstanding cold and they grow really slowly.

这些树是针叶树。它们很擅长抵御寒冷，而且生长得很慢。

Particularly fires that burn deep into the forest floor and they change the seed beds and that affects which tree species regenerate well.

特别是燃烧到森林地表深处的大火，它们改变了苗床，影响了哪些树种的再生。

And as a result we're seeing that recovering process shifting to what we call alternative trajectories.

结果，我们看到恢复过程转变为我们所说的替代轨迹。

A changing climate means fires are becoming more severe.

气候变化意味着火灾变得越来越严重。

It’s burning off the organic layer of soils that support species like black spruce.

它正在燃烧土壤的有机层，而这些有机层正是黑云杉等物种赖以生存的土壤。

So after a severe fire, the environment is better suited for deciduous tree species like birch and aspen to get a foothold. These trees grow much faster.

所以在一场严重的火灾之后，环境更适合像桦树和白杨这样的落叶树种找到立足点。 这些树长得更快。

And here’s where Johnstone and her colleagues discovered an unexpected twist.

约翰斯通和她的同事在这里发现了一个意外变化。

Even though extreme fires are burning up those carbon rich layers of organic soil and releasing that carbon into the atmosphere in the short term—what grows back is even more carbon hungry than what came before it.

尽管极端的大火正在燃烧那些富含碳的有机土壤层，并在短期内将碳释放到大气中，但生长回来的植物比之前的植物更需要碳。

Johnstone says this new kind of boreal forest is storing carbon four times faster than it would have before it burned.

约翰斯通表示，这种新型北方森林储存碳的速度是起火前的四倍。