Tall trees in the Amazon can suffer from warmer temperatures
Tall trees in Central Amazonia are impacted by periods of high maximum temperatures, which can cause them to shed their leaves and branches

Date:
February 17, 2022
Source:
University of Helsinki
Summary:
Tall trees in Central Amazonia are impacted by periods of high
maximum temperatures, which can cause them to shed their leaves
and branches.

With deforestation increasing, forests are becoming fragmented and
this exposes their interiors and increases the temperatures they
experience, making these losses even worse. With climate change
jeopardizing tall trees around the world, this new evidence of
spiraling negative effects from fragmentation is bad news, and
highlights the urgent need to reduce deforestation in the Amazon.



FULL STORY ========================================================================== Amazon forests are increasingly becoming fragmented by deforestation
and fire.

A new study published in Nature Communications and led by researchers
in the University of Helsinki, in cooperation with scientists across the
globe, uses a novel approach to quantify the impacts of fragmentation on
plant phenology. The study shows the annual life-cycle events in plants
from bud burst and leaf expansion to leaf and branch fall. Detailed measurements from terrestrial scanning LiDAR allowed the researchers to
track how different layers of the forest are affected by the changing environmental conditions caused by climate and fragmentation.


==========================================================================
The warming effects on Amazonian forests If very high greenhouse gases
(GHG) and CO2emissions double from current levels by 2050, maximum
temperatures in the Amazon will likely exceed 35 degrees Celsius at least
150 days a year by the end of the century, according to the IPCC's Sixth Assessment Report. The study published in Nature Communications elaborates
on why this is bad news for the Amazon rainforest. The study shows that
tall trees in Central Amazonia are impacted by maximum temperatures of
the understory above 35 degrees.

August and September usually register very high maximum temperatures above
35 degrees in many regions in the Amazon. The canopies of old-growth,
intact forests usually buffer the high temperatures observed in the
understory to some extent. However, when the temperatures in these
underlying layers reach 35 degrees, the tall trees then shed their leaves
and branches.

"If the number of days registering these very high temperatures inside
the forests also increases, we might see that the tall trees will suffer considerably," says postdoctoral researcher Matheus Nunes, the lead
author of the study.

The "breath" of the Earth is in flux In tropical forests, there are still
a lot of uncertainties in the timing and causes of seasonal events, such
as leaf shedding and burst. Understanding these patterns is crucial to understanding how tropical ecosystems will respond to climate change.



==========================================================================
"We designed an experiment using repeated surveys using a modern laser
scanner to investigate the seasonal dynamics of Amazonian forests," says Eduardo Maeda, the project coordinator funded by the Academy of Finland.

In the past decades, there has been a debate whether plants in the Amazon
are more limited by light or by water. This study provides evidence that
the problem is more complex, as it demonstrated a high variability across
the forest vertical layers. In other words, trees occupying the lower
layers, or strata, were more light-limited while tall trees occupying
the upper strata were mostly affected by climatic variations.

Forest fragmentation To complicate matters further, the study shows that deforestation in the region exacerbates the negative warming effects.

"The small, fragmented remaining forests tend to have hotter temperatures
in the understory, because of more light penetrating the forest,"
says Jose' Lui's Camargo, co-author of the study and director of
the "Biological Dynamics of Forest Fragments Project," the world's longest-running study of habitat fragmentation in Central Amazonia.

The hotter temperatures in these remaining forest fragments will add
further pressure on the tall trees, which caused trees to shed their
leaves and branches for a prolonged time. Currently, it is estimated
that 176,555 km2 of Amazonian forests are under the influence of edge
effects. If deforestation continue and forests become more fragmented,
we are likely to see severe consequences and a large-scale shift in the
way tropical ecosystems breathe.

========================================================================== Story Source: Materials provided by University_of_Helsinki. Note:
Content may be edited for style and length.


========================================================================== Related Multimedia:
* Tall_trees_of_fragmented_forests ========================================================================== Journal Reference:
1. Matheus Henrique Nunes, Jose' Lui's Campana Camargo, Gre'goire
Vincent,
Kim Calders, Rafael S. Oliveira, Alfredo Huete, Yhasmin Mendes de
Moura, Bruce Nelson, Marielle N. Smith, Scott C. Stark, Eduardo
Eiji Maeda.

Forest fragmentation impacts the seasonality of Amazonian
evergreen canopies. Nature Communications, 2022; 13 (1) DOI:
10.1038/s41467-022- 28490-7 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220217141223.htm

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