Effect of changing vegetation and precipitation on denudation – Part 1: Predicted vegetation composition and cover over the last 21 thousand years along the Coastal Cordillera of Chile
<p>Vegetation is crucial for modulating rates of denudation and landscape evolution, as it stabilizes and protects hillslopes and intercepts rainfall. Climate conditions and the atmospheric CO<sub>2</sub> concentration, hereafter [CO<sub>2</sub>], influence the estab...
Main Authors: | , , , , , , , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2018-10-01
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Series: | Earth Surface Dynamics |
Online Access: | https://www.earth-surf-dynam.net/6/829/2018/esurf-6-829-2018.pdf |
Summary: | <p>Vegetation is crucial for modulating rates of denudation and landscape
evolution, as it stabilizes and protects hillslopes and intercepts rainfall.
Climate conditions and the atmospheric CO<sub>2</sub> concentration, hereafter
[CO<sub>2</sub>], influence the establishment and performance of plants; thus, these factors have a direct
influence on vegetation cover. In addition, vegetation dynamics (competition
for space, light, nutrients, and water) and stochastic events (mortality and
fires) determine the state of vegetation, response times to environmental
perturbations and successional development. In spite of this,
state-of-the-art reconstructions of past transient vegetation changes have not
been accounted for in landscape evolution models. Here, a widely used dynamic
vegetation model (LPJ-GUESS) was used to simulate vegetation composition/cover
and surface runoff in Chile for the Last Glacial Maximum (LGM), the mid-Holocene (MH) and the present day (PD).
In addition, transient vegetation simulations were carried out from the LGM to PD for four sites in the Coastal
Cordillera of Chile at a spatial and temporal resolution adequate for
coupling with landscape evolution models.</p><p>A new landform mode was introduced to LPJ-GUESS to enable a better
simulation of vegetation dynamics and state at a sub-pixel resolution and to
allow for future coupling with landscape evolution models operating at
different spatial scales. Using a regionally adapted parameterization,
LPJ-GUESS was capable of reproducing PD potential natural
vegetation along the strong climatic gradients of Chile, and simulated
vegetation cover was also in line with satellite-based observations.
Simulated vegetation during the LGM differed markedly from PD conditions.
Coastal cold temperate rainforests were displaced northward by about
5° and the tree line and vegetation zones were at lower elevations
than PD. Transient vegetation simulations indicate a marked shift in
vegetation composition starting with the past glacial warming that coincides
with a rise in [CO<sub>2</sub>]. Vegetation cover between the sites ranged from
13 % (LGM: 8 %) to 81 % (LGM: 73 %) for the northern Pan de
Azúcar and southern Nahuelbuta sites, respectively, but did not vary by
more than 10 % over the 21 000 year simulation. A sensitivity study suggests
that [CO<sub>2</sub>] is an important driver of vegetation changes and, thereby,
potentially landscape evolution. Comparisons with other paleoclimate model
drivers highlight the importance of model input on simulated vegetation.</p><p>In the near future, we will directly couple LPJ-GUESS to a landscape
evolution model (see companion paper) to build a fully coupled
dynamic-vegetation/landscape evolution model that is forced with
paleoclimate data from atmospheric general circulation models.</p> |
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ISSN: | 2196-6311 2196-632X |