Camille Stevens-Rumann recently sat on the ground and measured small trees to see how much they had grown in seven months.
She found they had grown five to 10 centimeters. Her team had planted several different kinds of trees, known as evergreens, two years ago in an area of the Rocky Mountains in Colorado, which had burned in a fire in 2020.
Stevens-Rumann and other researchers want to learn the relationship between tree growth and elevation.
Researchers say there are not enough small trees or seeds from living trees to replace burned trees. Even if there were enough, they say the U.S. does not have the workers to plant and care for them.
The Forest Service said the biggest delays they meet while replanting on public land are preparing environmental and cultural studies and preparing burned areas, so they are safe to plant. That can take years.
Stevens-Rumann said, "We're in a place of such drastic climate change that we are not talking about whether or not some of these places will be a different kind of forest, but whether or not they will be forests at all."
Hotter fires
In the past, the U.S. was able to replant burned forests. But the researchers say larger, more intense fires are destroying trees that normally provide seeds. They say the fires leave burn scars so large trees cannot naturally regrow.
Solomon Z. Dobrowski is a University of Montana forest management expert. He said more areas in the West need replanting after fires than can be replanted. He said at least 1.5 million hectares need to be replanted but officials are unable to do so. He said that number could triple by 2050.
Targeted tree planting
Matthew Hurteau is a forest ecologist at the University of New Mexico. He studied the way scarred forests had been replanted after a fire in 2011 at Los Conchas. That fire destroyed huge areas of ponderosa pine trees. Hurteau found most of the seedlings, or very young trees, had died from earlier replanting.
As a result, he planted seedlings of different species at several elevations and on hillsides facing different directions. Now he is watching carefully for changes in the soil and water.
Researchers say seedling survival is less likely at lower elevations. It is hotter, drier and more open there. Replanting the same trees in the same areas is likely to fail.
Jason Sieg is acting supervisor of the Arapaho and Roosevelt National Forests & Pawnee National Grassland. He said the Forest Service rules require planting the same species at the same elevations as before a fire. But, he said, it is clear the agency will "need to be flexible moving forward."
For now, that might mean replanting at different elevations or collecting seeds from another place. Over time, researchers say it could require planting trees that are not native to the area. The idea has been debated but is gaining support.
"I've seen people go from saying, 'Absolutely, we cannot move trees around' to, 'Well, let's maybe let's try it at least, and do a few experiments to see if this will work,'" said Stevens-Rumann.
Environmental groups are working on private land burned by the Cameron Peak fire. They are replanting ponderosa pines 150 meters higher than where they used to grow, said Megan Maiolo-Heath. Maiolo-Heath is a spokesperson for the Coalition for the Poudre River Watershed.
So far, 84 percent of trees planted there last year are still alive.
Problems with replanting
The Forest Service is modernizing how it grows young trees. It is also studying ways to grow more or work with private industry, states and groups like the New Mexico Reforestation Center.
Experts say trees might never return to some areas. But it is important that the U.S. does as much as possible in a thoughtful way.
"Trees live for hundreds of years so we need to be thinking about what's right as we plant trees today," Hurteau said.
卡米爾·史蒂文斯-魯曼(Camille Stevens-Rumann)最近坐在地上測量小樹，看看它們在七個月內(nèi)長了多少。
她發(fā)現(xiàn)它們長了5到10厘米。兩年前，她的團隊在科羅拉多州落基山脈的一個地區(qū)種植了幾種不同種類的樹木，這些樹木被稱為常青樹，該地區(qū)在2020年的一場大火中被燒毀。
史蒂文斯-魯曼和其他研究人員想要了解樹木生長和海拔之間的關系。
研究人員表示，沒有足夠的小樹或來自活樹的種子來取代被燒毀的樹木。他們說，即使有足夠的數(shù)量，美國也沒有足夠的工人來種植和照顧它們。
森林服務局表示，在公共土地上重新植樹時遇到的最大延誤是準備環(huán)境和文化研究，以及清理火燒區(qū)域以確保安全進行種植。這些準備工作可能需要數(shù)年時間。
史蒂文斯-魯曼說:“我們處在一個氣候變化如此劇烈的地方，我們討論的不是其中一些地方是否會成為另一種森林，而是它們是否會成為森林。”
過去，美國能夠重新種植被燒毀的森林。但研究人員表示，更大、更強烈的火災正在摧毀通常提供種子的樹木。他們說，大火留下了燒傷的疤痕，所以大樹不能自然再生。
所羅門·z·多布羅斯基是蒙大拿大學的森林管理專家。他說，西部有更多地區(qū)在火災后需要重新種植，而不是可以重新種植。他說，至少有150萬公頃的土地需要重新種植，但官員們無法做到這一點。他說，到2050年，這個數(shù)字可能會增加兩倍。
定向植樹
馬修·赫爾托(Matthew Hurteau)是新墨西哥大學的森林生態(tài)學家。他研究了2011年洛斯孔查斯大火后受損森林的重新種植方式。那場大火摧毀了大片黃松林。赫爾托發(fā)現(xiàn)，大多數(shù)幼苗，或非常年輕的樹木，都因早期重新種植而死亡。
因此，他在不同的海拔和面向不同方向的山坡上種植了不同種類的幼苗?，F(xiàn)在他正在仔細觀察土壤和水的變化。
研究人員表示，在低海拔地區(qū)，幼苗存活的可能性較小。那里更熱、更干燥、更開闊。在同樣的地區(qū)重新種植同樣的樹木很可能會失敗。
杰森·西格是阿拉帕霍和羅斯福國家森林和波尼國家草原的代理主管。他說，林務局的規(guī)定要求在火災前的相同海拔種植相同的物種。但是，他說，很明顯，該機構將“需要靈活地向前推進”。
目前，這可能意味著在不同的海拔重新種植或從其他地方收集種子。研究人員表示，隨著時間的推移，可能需要種植該地區(qū)以外的樹木。這個想法一直在爭論，但正在獲得支持。
史蒂文斯-魯曼說:“我看到人們從說，‘當然，我們不能移動樹木’到說，‘好吧，讓我們至少嘗試一下，做一些實驗，看看這是否有效?！?/p>
環(huán)保組織正在金馬倫山火燒毀的私人土地上開展工作。Megan Maiolo-Heath說，他們正在重新種植比以前高150米的黃松。Maiolo-Heath是波德雷河流域聯(lián)盟的發(fā)言人。
到目前為止，去年種植的樹木中有84%仍然活著。
重新種植的問題
林務局正在對小樹的種植方式進行現(xiàn)代化改造。它還在研究如何與私營企業(yè)、州和新墨西哥再造林中心等組織合作。
專家表示，一些地區(qū)可能永遠不會恢復樹木。但重要的是，美國要以深思熟慮的方式盡可能多地采取行動。
赫爾托說:“樹木可以存活數(shù)百年，所以我們在種樹的時候需要考慮什么是正確的?！?/p>
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