Impact of dissolved organic carbon (DOC) deposition
on soil solution DOC
Intern(ation)al data evaluation
Arne Verstraeten
ICP Forests combined Expert Panel meeting Zagreb, 27-31 March 2017
Joint session EP on soil and soil solution and EP on deposition
1. Background
•
Atmospheric deposition and canopy leaching are a considerable input of DOC
and DON to the forest floor, according to a study that compiled published data
from case-studies in 42 temperate forest sites: variation in throughfall fluxes
could explain 46% and 65% of the variation in DOC and DON fluxes from the
forest floor, respectively (Michalzik et al. 2001)
•
However, a study on 5 level II plots in Flanders found that deposition fluxes of
DOC were strongly correlated with soil solution fluxes of DOC, but their
seasonal peaks were not simultaneous, suggesting a limited impact of
deposition DOC on soil solution DOC (Verstraeten et al. 2014 AE)
•
The input of canopy-derived DOC and DON is expected to increase because
climate warming increases the length of the growing season and could trigger
more frequent and intense attacks of phytophagous insects (Pitman et al. 2010
STE)
•
More information about the role of DOC and DON deposition on soil solution is
thus needed, with particular attention for seasonality effects
2. Objective
Gain more insight on the relationship between concentrations (and fluxes) of DOC
and DON in deposition and soil solution by studying the link between seasonal
patterns and temporal peaks in open field precipitation, throughfall and different
soil layers
2. Research questions
•
How strong do DOC and DON concentrations in soil solution depend
upon the concentrations in deposition?
•
Are there differences between coniferous and (deciduous) broadleaved
forests?
•
Can we refine our knowledge of the seasonal patterns of DOC and DON
and find links to events in the annual forest cycle (growing season,
bud burst and unfolding of leaves, flowering and pollen distribution,
shedding of leaves, …)?
3. Hypotheses
1)
The concentrations of DOC and DON in throughfall are related to the
concentrations in open field precipitation
2)
The concentrations of DOC and DON in soil solution are influenced by the
concentrations of DOC and DON in stand deposition (throughfall + stemflow)
=> peaks in soil solution coincide with or are preceded by peaks in
stand deposition
3)
The concentrations of DOC and DON in soil solution can be linked to major
seasonal events in the forest, and more particularly in spring (unfolding of
leaves, pollen distribution) and autumn (shedding of leaves)
4. Methods
•
- general analysis (all data)
- coniferous, broadleaved deciduous, (broadleaved evergreen?)
- selected number of individual tree species (Fagus sylvatica, Quercus robur,
Pinus sylvestris, Picea abies, …) (?)
•
Seasonal patterns (expected to be non-linear): general additive mixed models
(gamm’s)
•
Relationship between concentrations in deposition and soil solution: Linear
Mixed Models (LMM’s)?
5. Data requirements
•
Corrected aggregated deposition data (open field and throughfall) (1990-2011)
but: no DOC included yet!
•
Corrected aggregated soil solution data (1991-2013)
Thanks to Peter, Elisabeth, Jim & co.!
zero-tension and tension lysimeters were selected
DOC - Available data (raw)
Soil Layer Type
Organic
Hydromorphic
Mineral
# Countries
# plots
Total
<30 obs.
>100 obs.
10
102
7
68
2
6
0
5
24
222
14
144
=> 145.444 analyses (O horizon: 23.372)
DOC - O horizons
The number of countries with DOC measurements is quite limited, which
restricts the possibilities for translating the result to the European level
DOC - O horizons
But there seem to be quite some plots with sufficient DOC data
DOC - O horizons
DON – available data (raw)
Soil Layer Type
# Countries
# plots
Total
<30 obs.
>100 obs.
Organic
9
84
21
8
Hydromorphic
1
1
0
0
20
146
31
79
Mineral
=> 27.982 analyses (O-horizon: 4.497)
DON - O horizons
Also the number of countries with DON measurements is quite limited, which
restricts the possibilities for translating the result to the European level
DON - O horizons
The number of plots with long data series on DON is limited, but many plots
have at least 3 (but will be reduced to 2!) years of data
DON - O horizons
Main issues:
- Depositions of DOC still need to be calculated
- Deposition dataset is now limited to 2011 (2012-2013 not yet
included)
- Some data cleaning may be still needed:
# small number of plots/countries with high year-to-year variation
~ analytical problems?)
# some negative DON values occur
6. Cooperation
•
Communication of progress via project group ‘Impact of DOC deposition on soil
solution DOC’ on the ICP Forests website.
http://icp-forests.net/group/impact-of-doc-deposition-on-soil-solution-doc
Please join if you would like to contribute! (currently: 15 participants)
•
Participants will be invited for coauthorship
(paper, conference abstracts, …)
•
Meeting via Skype
(~ 1 time per month)
to discuss methods, data issues, results,…
•
Document sharing: google drive, sharepoint, …?
•
Supervision: EP on deposition,
EP on soil and soil solution
7. Timing
•
Update of aggregated deposition dataset: 2017-… (Peter?)
•
Data screening and analysis: 1/1/2018 – 30/9/2018
•
Present first results at 7th ICP Forests Scientific Conference (May 2018)
•
Writing draft paper: 1/10/2018 – 01/03/2019 (to be discussed at next EP
meeting in March 2019?)
•
Submission: April-May 2019
DOC – Seasonal pattern (O horizon)
DOC – Seasonal pattern (O horizon)
DON – Seasonal pattern (O horizon)
Thank you for your attention!
Any questions?