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Mechanisms behind species-specific water economy responses to water level drawdown in peat mosses

Bengtsson, Fia ; Granath, Gustaf ; Cronberg, Nils LU and Rydin, Håkan (2020) In Annals of Botany 126(2). p.219-230
Abstract
Background and Aims
The ecosystem engineers Sphagnum (peat mosses) are responsible for sequestering a large proportion of carbon in northern peatlands. Species may respond differently to hydrological changes, and water level changes may lead to vegetation shifts in peatlands, causing them to revert from sinks to sources of carbon. We aimed to compare species-specific responses to water level drawdown within Sphagnum, and investigate which traits affect water economy in this genus.
Methods
In a mesocosm experiment, we investigated how water level drawdown affected water content (WC) in the photosynthetically active apex of the moss and maximum quantum yield of photosystem II (i.e. Fv/Fm) of 13 Sphagnum species. Structural traits... (More)
Background and Aims
The ecosystem engineers Sphagnum (peat mosses) are responsible for sequestering a large proportion of carbon in northern peatlands. Species may respond differently to hydrological changes, and water level changes may lead to vegetation shifts in peatlands, causing them to revert from sinks to sources of carbon. We aimed to compare species-specific responses to water level drawdown within Sphagnum, and investigate which traits affect water economy in this genus.
Methods
In a mesocosm experiment, we investigated how water level drawdown affected water content (WC) in the photosynthetically active apex of the moss and maximum quantum yield of photosystem II (i.e. Fv/Fm) of 13 Sphagnum species. Structural traits were measured, and eight anatomical traits were quantified from scanning electron microscopy micrographs.
Key Results
Mixed-effects models indicated that at high water level, large leaves were the most influential predictor of high WC, and at low water level WC was higher in species growing drier in the field, with larger hyaline cell pore sizes and total pore areas associated with higher WC. Higher stem and peat bulk density increased WC, while capitulum mass per area and numerical shoot density did not. We observed a clear positive relationship between Fv/Fm and WC in wet-growing species.
Conclusions
While we found that most hummock species had a relatively high water loss resistance, we propose that some species are able to maintain a high WC at drawdown by storing large amounts of water at a high water level. Our result showing that leaf traits are important warrants further research using advanced morphometric methods. As climate change may lead to more frequent droughts and thereby water level drawdowns in peatlands, a mechanistic understanding of species-specific traits and responses is crucial for predicting future changes in these systems. (Less)
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author
; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Sphagnum, bulk density, moss water content, ecohydrology, hyaline cell, leaf anatomy, pore size, water retention
in
Annals of Botany
volume
126
issue
2
pages
219 - 230
publisher
Oxford University Press
external identifiers
  • pmid:32185391
  • scopus:85088678805
ISSN
0305-7364
DOI
10.1093/aob/mcaa033
language
English
LU publication?
yes
id
3b4347c2-b867-4f1e-8500-b41328b680b0
date added to LUP
2020-12-08 09:25:57
date last changed
2020-12-29 03:10:13
@article{3b4347c2-b867-4f1e-8500-b41328b680b0,
  abstract     = {Background and Aims<br/>The ecosystem engineers Sphagnum (peat mosses) are responsible for sequestering a large proportion of carbon in northern peatlands. Species may respond differently to hydrological changes, and water level changes may lead to vegetation shifts in peatlands, causing them to revert from sinks to sources of carbon. We aimed to compare species-specific responses to water level drawdown within Sphagnum, and investigate which traits affect water economy in this genus.<br/>Methods<br/>In a mesocosm experiment, we investigated how water level drawdown affected water content (WC) in the photosynthetically active apex of the moss and maximum quantum yield of photosystem II (i.e. Fv/Fm) of 13 Sphagnum species. Structural traits were measured, and eight anatomical traits were quantified from scanning electron microscopy micrographs.<br/>Key Results<br/>Mixed-effects models indicated that at high water level, large leaves were the most influential predictor of high WC, and at low water level WC was higher in species growing drier in the field, with larger hyaline cell pore sizes and total pore areas associated with higher WC. Higher stem and peat bulk density increased WC, while capitulum mass per area and numerical shoot density did not. We observed a clear positive relationship between Fv/Fm and WC in wet-growing species.<br/>Conclusions<br/>While we found that most hummock species had a relatively high water loss resistance, we propose that some species are able to maintain a high WC at drawdown by storing large amounts of water at a high water level. Our result showing that leaf traits are important warrants further research using advanced morphometric methods. As climate change may lead to more frequent droughts and thereby water level drawdowns in peatlands, a mechanistic understanding of species-specific traits and responses is crucial for predicting future changes in these systems.},
  author       = {Bengtsson, Fia and Granath, Gustaf and Cronberg, Nils and Rydin, Håkan},
  issn         = {0305-7364},
  language     = {eng},
  month        = {03},
  number       = {2},
  pages        = {219--230},
  publisher    = {Oxford University Press},
  series       = {Annals of Botany},
  title        = {Mechanisms behind species-specific water economy responses to water level drawdown in peat mosses},
  url          = {http://dx.doi.org/10.1093/aob/mcaa033},
  doi          = {10.1093/aob/mcaa033},
  volume       = {126},
  year         = {2020},
}