{"id":710,"date":"2017-01-02T18:10:46","date_gmt":"2017-01-02T18:10:46","guid":{"rendered":"https:\/\/techfragments.com\/?p=710"},"modified":"2022-08-12T18:22:39","modified_gmt":"2022-08-12T18:22:39","slug":"temperate-broadleaf-forests-heat-stress","status":"publish","type":"post","link":"https:\/\/techfragments.com\/temperate-broadleaf-forests-heat-stress\/","title":{"rendered":"Temperate Broadleaf Forests More Susceptible To Heat Stress"},"content":{"rendered":"

Temperate broadleaf forests, such as the stands of red oak<\/a> common in New England, absorb more carbon than expected along their edges but are more susceptible to heat stress.<\/p>\n

Over centuries, as humans have cleared fields for farms, built roads and highways, and expanded cities, we\u2019ve been cutting down trees. Since 1850, we\u2019ve reduced global forest cover by one-third.<\/p>\n

We\u2019ve also changed the way forests look.<\/p>\n

Much of the world\u2019s woodlands now exist in choppy fragments, with 20 percent of the remaining forest within 100 meters of an edge, like a road, backyard, cornfield, or parking lot.<\/p>\n

Good News<\/h2>\n

Scientists have studied fragmented forests for decades, mostly to gauge their effects on wildlife and biodiversity. But recently, two Boston University scientists<\/a>, Andrew Reinmann, a postdoctoral research associate, and Lucy Hutyra, an associate professor of earth and environment, have turned their attention to another issue: the effects of forest fragments on carbon storage and climate change.<\/p>\n

The research offers some good news and bad news about forest fragmentation. It suggests that while these forests may be more valuable carbon sinks than previously thought, they are also more sensitive to climate change.<\/p>\n

\u201cHaving accurate estimates of what those trees on the edge are doing\u2014how much carbon they\u2019re taking out of the atmosphere\u2014is really important when we think about our future climate,\u201d<\/p><\/blockquote>\n

says Reinmann, lead author of the paper.<\/p>\n

The annual atmospheric concentration of carbon dioxide, a potent greenhouse gas and agent of global warming, has increased by more than 40 percent since the start of the Industrial Revolution and continues to rise. Forests play a critical role as a carbon sink, absorbing about 25 percent of the CO2 emissions we humans put into the sky.<\/p>\n

Forest Fragments<\/h2>\n

Most of our understanding of forest carbon dynamics comes from studying intact rural forests like Hubbard Brook<\/a> in New Hampshire\u2019s White Mountains and Harvard Forest in Petersham, Massachusetts, not from studying forest fragments.<\/p>\n

\u201cWhen you fragment a forest, you change a lot of the growing conditions of the forest that\u2019s left behind,\u201d says Reinmann, \u201cbut we don\u2019t have a very good understanding of how that change affects carbon sequestration and storage.\u201d<\/p><\/blockquote>\n

To find out, Reinmann and Hutyra gathered data from 21 fragmented forest plots around Boston, measuring about 500 trees. In eight of those plots, they went a step further, taking sample cores from trees above 10 centimeters in diameter, a total of 420 cores from 210 trees.<\/p>\n

They used the cores, and other data, to calculate how fast the trees grew. A tree\u2019s size and growth rate indicate how much carbon it can absorb and also how much stress it\u2019s experiencing.<\/p>\n

\u201cIf this carbon sink all of a sudden shuts off, our projections for future climate will change,\u201d says Reinmann. \u201cSo our current understanding and ecological models, which don\u2019t account for this, are missing something important.\u201d<\/p><\/blockquote>\n

Reinmann and Hutyra found that forest fragments grow faster along the edges than intact forests, absorbing more carbon than expected.<\/p>\n

\u201cWhen you create that edge, you essentially are reducing competition and freeing up resources like light, water, and nutrients for trees,\u201d<\/p><\/blockquote>\n

says Reinmann, who notes that the effect extends in about 20 meters from the forest edge.<\/p>\n

Temperate Broadleaf Forests<\/h2>\n

Curiously, the finding may hold only for temperate broadleaf forests common in New England, the Appalachians, Canada, and Europe. Amazon rainforest has the opposite effect when fragmented, with lower biomass and less carbon storage along the edges.<\/p>\n

\u201cForesters and loggers have known this intuitively for a long time: if you go in and you reduce the competition for resources, the remaining individuals will grow faster,\u201d adds Hutyra. \u201cThe novel piece of this work was to quantify it across these edges, see how far into the forest it goes, and put it into context with how much this fragmentation matters in a portion of the world \u2014 southern New England \u2014 that we know is a large net carbon sink.\u201d<\/p><\/blockquote>\n

Though this seems like a win for patchy New England forests, deforestation is still bad for carbon sequestration overall.<\/p>\n

\u201cWhen you fragment a forest, the remaining forest can offset a little bit of what was lost, but not completely. So it may not be as terrible from a carbon perspective as we thought, but it\u2019s still bad,\u201d<\/p><\/blockquote>\n

says Reinmann.<\/p>\n

Bad News<\/h2>\n

Offsetting this somewhat good news is the paper\u2019s other finding.<\/p>\n

These forest edges, more exposed to wind and sun, grow more slowly when stressed by heat.<\/p>\n

\u201cYou lose a lot of carbon benefit in hot years. But once you get much past that threshold, the trees grow much slower,\u201d<\/p><\/blockquote>\n

says Reinmann, who found that the \u201cmagic number\u201d for local trees is about 27\u00b0 C (80.6\u00b0 F), which corresponds to the average high temperature in July, our hottest month.<\/p>\n

And the really bad news: if regional temperatures continue to increase at a steady pace, the current carbon benefit offered by forest edges may decline significantly.<\/p>\n

\u201cIf this carbon sink all of a sudden shuts off, our projections for future climate will change,\u201d says Reinmann. \u201cSo our current understanding and ecological models, which don\u2019t account for this, are missing something important.\u201d<\/p><\/blockquote>\n

Reinmann and Hutyra are currently expanding the work to study rural forests and are so far finding even larger effects there. They are also hoping to use high-resolution imaging and more precise chemical analyses to look closer at core samples to see how growth and photosynthesis change over days, seasons, heat waves, and other environmental stressors.<\/p>\n

More data may lead to better models, says Hutyra.<\/p>\n

The work was funded by the National Oceanic and Atmospheric Administration, the National Aeronautics and Space Administration, and the National Science Foundation.<\/p>\n

Original Study: Edge effects enhance carbon uptake and its vulnerability to climate change in temperate broadleaf forests<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"

Temperate broadleaf forests, such as the stands of red oak common in New England, absorb more carbon than expected along their edges but are more susceptible to heat stress. Over centuries, as humans have cleared fields for farms, built roads and highways, and expanded cities, we\u2019ve been cutting down trees. Since 1850, we\u2019ve reduced global…<\/p>\n","protected":false},"author":2,"featured_media":712,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[13,99],"_links":{"self":[{"href":"https:\/\/techfragments.com\/wp-json\/wp\/v2\/posts\/710"}],"collection":[{"href":"https:\/\/techfragments.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/techfragments.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/techfragments.com\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/techfragments.com\/wp-json\/wp\/v2\/comments?post=710"}],"version-history":[{"count":1,"href":"https:\/\/techfragments.com\/wp-json\/wp\/v2\/posts\/710\/revisions"}],"predecessor-version":[{"id":711,"href":"https:\/\/techfragments.com\/wp-json\/wp\/v2\/posts\/710\/revisions\/711"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/techfragments.com\/wp-json\/wp\/v2\/media\/712"}],"wp:attachment":[{"href":"https:\/\/techfragments.com\/wp-json\/wp\/v2\/media?parent=710"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/techfragments.com\/wp-json\/wp\/v2\/categories?post=710"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/techfragments.com\/wp-json\/wp\/v2\/tags?post=710"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}