Monthly flash – Svenska hydrologiska rådet (SHR)

Marcus Cheuk Hei Tong, a PostDoc at the Department of Forest Ecology and Management, SLU Umeå, was awarded a travel grant from SHR and attended Hydrologidagarna 2023. Below, Marcus shares a story describing his research about carbon, greenhouse gases, ditch cleaning and rewetted peatland.

When considering significant historical alterations to the regional hydrological systems caused by humans on a large scale, what has come to your mind? Are you thinking of canals or massive dams? In Sweden, up to 970 00 km of ditches (equivalent to 24 times around the world) have been created across the wetlands for agriculture and forestry (Lidberg et al, 2023). This has brought massive changes to the hydrology and possibly the global climate, but it has seldom been brought into the scene.

The regulation of land drainage in Sweden dates back to the Middle Ages, with laws governing the reduction of water surfaces and the drainage of wetlands. These practices have been deemed crucial for expanding cultivable land and, more recently, fostering forest growth. Peatlands, the most prevalent type of wetlands in Fennoscandia (Joosten and Clarke, 2002), play a vital role in long-term carbon sequestration due to a consistent positive balance between carbon input from vegetation biomass development and losses through organic matter decomposition (Clymo, 1984). The drainage of peatlands is likely to accelerate peat decomposition and the associated release of carbon (Laine et al., 1995). In recent years, discussions on hydrological management in forests have intensified, especially regarding the implications of these practices.

Over my previous PhD and my current postdoc projects, I have been exploring different hydrological managements of peatland forests on the carbon balance and greenhouse gas emissions. These include:

The carbon and greenhouse gas balance in a boreal drained peatland forest, with reference to a natural mire (manuscript under peer review process)
The carbon and greenhouse gas balance in response to post-harvest ditch cleaning (Tong et al., 2022a; Tong et al., 2022b)
The carbon and greenhouse gas balance in a recently rewetted boreal peatland, with reference to a natural mire (manuscript in progress)

Methodology

My projects have applied various approaches to quantify the carbon and greenhouse gas balance, including the application of eddy covariance when measuring with an ecosystem scale. Eddy covariance is a micrometeorological technique that enables real-time and continuous assessment of the exchange of gases, such as carbon dioxide (CO₂) and methane (CH₄), between ecosystems and the atmosphere. This approach relies on the precise measurement of fluctuations in wind velocity and gas concentrations to calculate fluxes at high temporal resolution.

In some occasions such as measurement of gas exchange from soil, manual closed chamber measurements have been applied. This is characterised by a sealed chamber being placed over the soil, with gas sampling ports connected to portable analysers to determine gas concentrations. The change in gas concentrations over time indicates the rate of gas fluxes.

Water samples were also collected at the outlet of the study ecosystems to analyse the total amount of dissolved carbon, which includes both organic and inorganic carbon. After coupling with the discharge rate measured from V-notch weirs, the total rate of aquatic carbon discharge could be quantified.

Results

The study results indicate that hydrological drainage activities, including long term forestry drainage and short-term ditch cleaning on clearcuts, did not increase carbon and greenhouse gas emissions. Conversely, a rewetted peatland has recorded an emission of carbon during the initial two years, with reference to a nearby natural mire which was a contemporary carbon sink. CO₂, the predominant gas in carbon and greenhouse gas balances, exhibited enhanced uptake in the historically drained peatland forest compared to the nearby natural mire. CO₂ emissions decreased after the initial cleaning of ditches in a dry and fertile clear-cut. However, negligible alterations were noted following ditch cleaning in the relatively wet and infertile clear-cut. Moreover, the drainage had a consistent effect in mitigating the substantial emission of CH₄ and potentially increasing CH₄ absorption across all scenarios, whereas rewetting has increased CH₄ emission during initial years but remained significantly lower than the natural mire.

Aquatic loss of carbon through dissolved carbon made a significant contribution (>20%) to the total carbon exchange in a natural mire. This indicates that aquatic exchange of carbon should not be neglected when accounting the total carbon balance from boreal peatlands.

It is also notable that beyond water levels, vegetation growth emerged as a crucial factor influencing carbon uptake and the climate-cooling impact at the study sites. This encompassed the development of ground vegetation in clear-cut areas and the growth of both overstory and understory vegetation in peatland forests. Overall, these findings highlight the intricate interplay between carbon dynamics, hydrological drainage effects, and vegetation growth in shaping the carbon balance and environmental cooling potential of peatland ecosystems.

References:

Clymo, R. S. (1984). The limits to peat bog growth. Philosophical Transactions of the Royal Society of London. B, Biological Sciences, 303(1117), 605-654.

Joosten, H., & Clarke, D. (2002). Wise use of mires and peatlands. International mire conservation group and international peat society, 304.

Laine, J., Vasander, H., & Laiho, R. (1995). Long-term effects of water level drawdown on the vegetation of drained pine mires in southern Finland. Journal of Applied Ecology, 785-802.

Lidberg, W., Paul, S. S., Westphal, F., Richter, K. F., Lavesson, N., Melniks, R., … & Ågren, A. M. (2023). Mapping drainage ditches in forested landscapes using deep learning and aerial laser scanning. Journal of irrigation and drainage engineering, 149(3), 04022051.

Tong, C. H. M., Nilsson, M. B., Drott, A., & Peichl, M. (2022a). Drainage ditch cleaning has no impact on the carbon and greenhouse gas balances in a recent Forest clear-cut in boreal Sweden. Forests, 13(6), 842.

Tong, C. H. M., Nilsson, M. B., Sikström, U., Ring, E., Drott, A., Eklöf, K., … & Peichl, M. (2022b). Initial effects of post-harvest ditch cleaning on greenhouse gas fluxes in a hemiboreal peatland forest. Geoderma, 426, 116055.

Skrivet av: Benjamin Fischer

COVID19 caused disruptions in the way we live as society. We were interested to understand how the education of hydrology and water related sciences in Sweden got affected by Covid19 (period March to October 2020). To get an overview we sent a questionnaire to the SHR members and the wider network, all part of the main universities in Sweden.

We received a snapshot overview from nine participants representing the main Universities in water education at bachelor or master level (figure 1).

**Figure 1 Map of Sweden where the water droplet indicates a University with at least one response to the questionnaire.**

All universities reported, that they had to change abruptly from in class teaching to teaching remotely in March 2020. In addition, it was reported that to comply with social distance field trips and some courses were cancelled. Next to teaching in a virtual class room environment, teachers used mixed learning (e.g. pre-recorded lectures and remote question hours), feedback seminars or individual-based field activities, online video material, virtual laboratory or field excursions, reading and discussion exercises, up to do-it-yourself low-tech field experiments.

During the first part of the autumn term distance teaching was continued but to some extend some class room teaching with reduced number of students and more local field trips were held.

The teachers experience and by teachers reported students experience was diverse from positive up to negative (figure 2). From teachers’ point of view, the main challenge reported was the physical distance and loss of contact with students which made it difficult to monitor the student’s performance and build professional relations. Also, the change to novel teaching methods and software was perceived not always easy. Teachers who have not yet made the switch to distance education were uneasy with concerns.

Instead from student feedback it seems that they understood the situation and challenges with current teaching and were largely neutral.

**Figure 2 Teachers experience (left) and by teachers reported students experience (right) in respect of changed teaching due to COVID19 measures.**

To overcome negative experience of education during COVID19, some teachers purposed larger rooms to be able to keep distance during on campus classes, mixed physical/ distance lectures and shorter distance lectures with more brakes.

Open feedback concerning teaching during COVID19 were:

Positive in terms of resources mobilized by University to facilitate distance teaching and minimize students delay
However, it seems unclear if extra working time of teachers will be compensated for
Understanding from students about the challenges in teaching in this situation
Teachers should support each other as much as possible with available resources

Despite only nine responses, the held questionnaire gives only a first indication on how COVID19 affected water education at the different Universities in Sweden. COVID19 caused not only a disruption in society but also water education in Sweden. A large effort and creativity made it possible to keep up the core of water education. However, also important elements in water education such as field excursion were cancelled and contact between teacher student got lost affecting the knowledge transfer. The long-term effect on water education in Sweden and the effect on teachers and students should be investigated more systematically. Next to these negative aspects of COVID19 the abrupt changes in water education provides also opportunities to explore novel forms of teaching to prepare water education in Sweden for the future.

For now, most important is to keep distance and stay healthy!!

Your, SHR-team

Participants and background information

(The author did not contribute to the questionnaire. )

The courses thought by the responders were general hydrology, hydrological modelling, forest management, ecology, biogeochemistry, forestry, sustainability and environmental science, geography, statistics, sustainable development, fluvial geomorphology, GIS, soil science and geology. Class room lectures were the most frequent lecture style, followed by computer labs, field courses and some laboratory exercises (figure 3). Per course the average number of students ranges from 10 up to more than 40 students in which class room teaching (figure 4).

Figure 3 The different responders to the questionnaire indicated which styles of lecture they teach at the Universities of the different responders

Figure 4 the average amount group size per class

Questions asked

At which University do you teach?
What is your background or do you see yourself (e.g. hydrologist, ecology, water manager, sociology …)?
What is your role in teaching? (one option possible)
Which level of courses do you teach? (multiple options possible)
Which courses do you teach (hydrology, ecology …)?
How many students do you on average have in your courses? (one options possible)
With which format do you generally teach? (multiple options possible)
Describe shortly which measures your University took during Covid19
Describe shortly how teaching got affected due to Covid19
Which methods in teaching did you use to continue teaching?
If teaching changed, was this a positive or negative development from a teacher’s point of view?
If teaching changed, was student feedback positive or negative?
In case teachers or students had negative experiences, what could be done to overcome these limitations?
Open feedback (you can write here additional information you want to share concerning teaching during Covid19)