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Shifts within the carbon cycle in response to the absence of keystone herbivore Ovibos moschatus in a high arctic mire

White, Joel LU (2017) In Student thesis series INES NGEM01 20171
Dept of Physical Geography and Ecosystem Science
Abstract
Tundra ecosystems are generally recognized as globally important carbon sinks, yet the knowledge on threats to such ecosystems is narrow. Climate change is predicted to reduce the number of muskox (Ovibos moschatus) in the arctic, it is therefore essential to understand the effect herbivores induce on the arctic ecosystem. The muskox is known as a keystone species in the arctic tundra. Such keystone herbivores can induce strong top-down control, resulting in a transformed landscape when not present. Little is known about how herbivores impact the terrestrial carbon cycle, especially in arctic mires. Within this study, I evaluate whether the absence of grazing and trampling by the large herbivore muskox influences vegetation density and... (More)
Tundra ecosystems are generally recognized as globally important carbon sinks, yet the knowledge on threats to such ecosystems is narrow. Climate change is predicted to reduce the number of muskox (Ovibos moschatus) in the arctic, it is therefore essential to understand the effect herbivores induce on the arctic ecosystem. The muskox is known as a keystone species in the arctic tundra. Such keystone herbivores can induce strong top-down control, resulting in a transformed landscape when not present. Little is known about how herbivores impact the terrestrial carbon cycle, especially in arctic mires. Within this study, I evaluate whether the absence of grazing and trampling by the large herbivore muskox influences vegetation density and composition, subsequently altering the exchange of greenhouse gases between the atmosphere and tundra. During July 2016, CO2 and CH4 fluxes were measured in experimental muskox exclosure and control plots at Zackenberg, north-east Greenland. Vegetation and core samples were analysed for variances in composition and density. Furthermore, environmental parameters including soil temperature, water table depth, active layer and photosynthetic active radiation were measured. A significant change in the composition of vascular plants occurred and lower number of tillers of Eriophorum scheuchzeri and Dupontia psilosantha were recorded in exclosure plots. This change in vegetation resulted in no significant difference between net ecosystem exchange, gross primary production and ecosystem respiration with no below-ground root biomass variance. However, significantly lower CH4 fluxes were recorded within the exclosure plots. I speculate that the difference between treatments is an ongoing divergence from a vascular plant community towards a less diverse moss dominated layer. As time goes on more structural differences below ground are predicted to occur. While it is uncertain if herbivory in the arctic will increase or decrease, this experiment indicates potentially significant effects on the vegetation composition and its subsequent impact on fluxes of the greenhouse gas CH4. (Less)
Popular Abstract
Tundra ecosystems are generally recognized as globally important carbon sinks, yet the knowledge on threats to such ecosystems is narrow. Climate change is predicted to reduce the number of muskox (Ovibos moschatus) in the arctic, it is therefore essential to understand the effect herbivores induce on the arctic ecosystem. Such keystone herbivores can induce strong top-down control, resulting in a transformed landscape when not present. Little is known about how herbivores impact the terrestrial carbon cycle, especially in arctic mires.

Within this study, I evaluate whether the absence of grazing and trampling by the large muskox influences vegetation density and composition, subsequently altering the exchange of greenhouse gases... (More)
Tundra ecosystems are generally recognized as globally important carbon sinks, yet the knowledge on threats to such ecosystems is narrow. Climate change is predicted to reduce the number of muskox (Ovibos moschatus) in the arctic, it is therefore essential to understand the effect herbivores induce on the arctic ecosystem. Such keystone herbivores can induce strong top-down control, resulting in a transformed landscape when not present. Little is known about how herbivores impact the terrestrial carbon cycle, especially in arctic mires.

Within this study, I evaluate whether the absence of grazing and trampling by the large muskox influences vegetation density and composition, subsequently altering the exchange of greenhouse gases between the atmosphere and tundra.

During July 2016, CO2 and CH4 fluxes were measured in experimental muskox exclosure and control plots at Zackenberg, north-east Greenland. Vegetation and core samples were analysed for variances in composition and density.
A significant change in the composition of vascular plants occurred and lower number of tillers were recorded in exclosure plots. Surprising this change in vegetation resulted in no significant difference between the system productivity and below-ground root biomass. However, significantly lower CH4 fluxes were recorded within the exclosure plots.

I speculate that the difference between treatments is an on-going divergence from a vascular plant community towards a less diverse moss dominated layer. While it is uncertain if muskox populations will change, this experiment indicates potentially significant effects on the vegetation composition and its subsequent impact on fluxes of the greenhouse gas CH4. (Less)
Please use this url to cite or link to this publication:
author
White, Joel LU
supervisor
organization
alternative title
Do herbivores alter arctic carbon cycles?
course
NGEM01 20171
year
type
H2 - Master's Degree (Two Years)
subject
keywords
vegetation, carbon, wetland., methane, Arctic, Physical Geography & Ecosystem Science, herbivory
publication/series
Student thesis series INES
report number
413
language
English
id
8906399
date added to LUP
2017-05-03 15:56:48
date last changed
2017-05-03 15:56:48
@misc{8906399,
  abstract     = {Tundra ecosystems are generally recognized as globally important carbon sinks, yet the knowledge on threats to such ecosystems is narrow. Climate change is predicted to reduce the number of muskox (Ovibos moschatus) in the arctic, it is therefore essential to understand the effect herbivores induce on the arctic ecosystem. The muskox is known as a keystone species in the arctic tundra. Such keystone herbivores can induce strong top-down control, resulting in a transformed landscape when not present. Little is known about how herbivores impact the terrestrial carbon cycle, especially in arctic mires. Within this study, I evaluate whether the absence of grazing and trampling by the large herbivore muskox influences vegetation density and composition, subsequently altering the exchange of greenhouse gases between the atmosphere and tundra. During July 2016, CO2 and CH4 fluxes were measured in experimental muskox exclosure and control plots at Zackenberg, north-east Greenland. Vegetation and core samples were analysed for variances in composition and density. Furthermore, environmental parameters including soil temperature, water table depth, active layer and photosynthetic active radiation were measured. A significant change in the composition of vascular plants occurred and lower number of tillers of Eriophorum scheuchzeri and Dupontia psilosantha were recorded in exclosure plots. This change in vegetation resulted in no significant difference between net ecosystem exchange, gross primary production and ecosystem respiration with no below-ground root biomass variance. However, significantly lower CH4 fluxes were recorded within the exclosure plots. I speculate that the difference between treatments is an ongoing divergence from a vascular plant community towards a less diverse moss dominated layer. As time goes on more structural differences below ground are predicted to occur. While it is uncertain if herbivory in the arctic will increase or decrease, this experiment indicates potentially significant effects on the vegetation composition and its subsequent impact on fluxes of the greenhouse gas CH4.},
  author       = {White, Joel},
  keyword      = {vegetation,carbon,wetland.,methane,Arctic,Physical Geography & Ecosystem Science,herbivory},
  language     = {eng},
  note         = {Student Paper},
  series       = {Student thesis series INES},
  title        = {Shifts within the carbon cycle in response to the absence of keystone herbivore Ovibos moschatus in a high arctic mire},
  year         = {2017},
}