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Seasonality and nitrogen supply modify carbon partitioning in understory vegetation of a boreal coniferous forest

Hasselquist, N. J.; Metcalfe, D. B. LU ; Marshall, J. D.; Lucas, R. W. and Högberg, P. (2016) In Ecology 97(3). p.671-683
Abstract

Given the strong coupling between the carbon (C) and nitrogen (N) cycles, there is substantial interest in understanding how N availability affects C cycling in terrestrial ecosystems, especially in ecosystems limited by N. However, most studies in temperate and boreal forests have focused on the effects of N addition on tree growth. By comparison, less is known about the effects of N availability on the cycling of C in understory vegetation despite some evidence that dwarf shrubs, mosses, and lichens play an important role in the forest C balance. In this study, we used an in situ 13CO2 pulse-labeling technique to examine the short-term dynamics of C partitioning in understory vegetation in three boreal Pinus... (More)

Given the strong coupling between the carbon (C) and nitrogen (N) cycles, there is substantial interest in understanding how N availability affects C cycling in terrestrial ecosystems, especially in ecosystems limited by N. However, most studies in temperate and boreal forests have focused on the effects of N addition on tree growth. By comparison, less is known about the effects of N availability on the cycling of C in understory vegetation despite some evidence that dwarf shrubs, mosses, and lichens play an important role in the forest C balance. In this study, we used an in situ 13CO2 pulse-labeling technique to examine the short-term dynamics of C partitioning in understory vegetation in three boreal Pinus sylvestris forest stands exposed to different rates of N addition: a low and high N addition that receive annual additions of NH4NO3 of 20 and 100 kg N/ha, respectively, and this is a typo. It should be an unfertilized control. Labeling was conducted at two distinct periods (early vs. late growing season), which provided a seasonal picture of how N addition affects C dynamics in understory vegetation. In contrast to what has been found in trees, there was no obvious trend in belowground C partitioning in ericaceous plants in response to N additions or seasonality. Increasing N addition led to a greater percentage of 13C being incorporated into ericaceous leaves with a high turnover, whereas high rates of N addition strongly reduced the incorporation of 13C into less degradable moss tissues. Addition of N also resulted in a greater percentage of the 13C label being respired back to the atmosphere and an overall reduction in total understory carbon use efficiency. Taken together, our results suggest a faster cycling of C in understory vegetation with increasing N additions; yet the magnitude of this general response was strongly dependent on the amount of N added and varied seasonally. These results provide some of the first in situ C and N partitioning estimates for plants growing under the complex web of resource limitations in the boreal understory.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
C, Biomass allocation, Boreal forest, Carbon cycling, Ericaceous shrubs, Isotopes, Mosses, Nitrogen availability, Pulse-chase labeling, Seasonality
in
Ecology
volume
97
issue
3
pages
13 pages
publisher
Ecological Society of America
external identifiers
  • Scopus:84962129343
ISSN
0012-9658
language
English
LU publication?
yes
id
e2bd2829-c486-487b-844d-d935259c661e
date added to LUP
2016-07-14 10:38:32
date last changed
2016-07-14 10:38:32
@misc{e2bd2829-c486-487b-844d-d935259c661e,
  abstract     = {<p>Given the strong coupling between the carbon (C) and nitrogen (N) cycles, there is substantial interest in understanding how N availability affects C cycling in terrestrial ecosystems, especially in ecosystems limited by N. However, most studies in temperate and boreal forests have focused on the effects of N addition on tree growth. By comparison, less is known about the effects of N availability on the cycling of C in understory vegetation despite some evidence that dwarf shrubs, mosses, and lichens play an important role in the forest C balance. In this study, we used an in situ <sup>13</sup>CO<sub>2</sub> pulse-labeling technique to examine the short-term dynamics of C partitioning in understory vegetation in three boreal Pinus sylvestris forest stands exposed to different rates of N addition: a low and high N addition that receive annual additions of NH<sub>4</sub>NO<sub>3</sub> of 20 and 100 kg N/ha, respectively, and this is a typo. It should be an unfertilized control. Labeling was conducted at two distinct periods (early vs. late growing season), which provided a seasonal picture of how N addition affects C dynamics in understory vegetation. In contrast to what has been found in trees, there was no obvious trend in belowground C partitioning in ericaceous plants in response to N additions or seasonality. Increasing N addition led to a greater percentage of <sup>13</sup>C being incorporated into ericaceous leaves with a high turnover, whereas high rates of N addition strongly reduced the incorporation of <sup>13</sup>C into less degradable moss tissues. Addition of N also resulted in a greater percentage of the <sup>13</sup>C label being respired back to the atmosphere and an overall reduction in total understory carbon use efficiency. Taken together, our results suggest a faster cycling of C in understory vegetation with increasing N additions; yet the magnitude of this general response was strongly dependent on the amount of N added and varied seasonally. These results provide some of the first in situ C and N partitioning estimates for plants growing under the complex web of resource limitations in the boreal understory.</p>},
  author       = {Hasselquist, N. J. and Metcalfe, D. B. and Marshall, J. D. and Lucas, R. W. and Högberg, P.},
  issn         = {0012-9658},
  keyword      = {C,Biomass allocation,Boreal forest,Carbon cycling,Ericaceous shrubs,Isotopes,Mosses,Nitrogen availability,Pulse-chase labeling,Seasonality},
  language     = {eng},
  month        = {03},
  number       = {3},
  pages        = {671--683},
  publisher    = {ARRAY(0xabfaba8)},
  series       = {Ecology},
  title        = {Seasonality and nitrogen supply modify carbon partitioning in understory vegetation of a boreal coniferous forest},
  volume       = {97},
  year         = {2016},
}