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Dan KouUniversity of Eastern Finland | UEF · Biogeochemistry research group
Dan Kou
Doctor of Philosophy
Permafrost; Peatland; Biogeochemistry; Nitrogen; Carbon; Modelling; Big data analysis
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41
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Introduction
Dan Kou currently works in the Biogeochemistry research group, at the University of Eastern Finland.
Skills and Expertise
Publications
Publications (41)
Significant progress in permafrost carbon science made over the past decades include the identification of vast permafrost carbon stocks, the development of new pan‐Arctic permafrost maps, an increase in terrestrial measurement sites for CO2 and methane fluxes, and important factors affecting carbon cycling, including vegetation changes, periods of...
Peatlands are huge reservoirs of carbon in the terrestrial ecosystem. They are both long-term sinks of organic carbon and a major natural source of atmospheric methane. These carbon-rich ecosystems are at risk of losing their carbon sink capacity and becoming a huge source of carbon dioxide and methane due to ongoing warming. In this study, we exam...
Arctic wetlands are known methane (CH4) emitters but recent studies
suggest that the Arctic CH4 sink strength may be underestimated. Here we
explore the capacity of well-drained Arctic soils to consume atmospheric
CH4 using >40,000 hourly flux observations and spatially distributed flux
measurements from 4 sites and 14 surface types. While consumpt...
Climate warming leads to widespread permafrost thaw with a fraction of the thawed permafrost carbon (C) being released as carbon dioxide (CO2 ), thus triggering a positive permafrost C-climate feedback. However, large uncertainty exists in the size of this model-projected feedback, partly owing to the limited understanding of permafrost CO2 release...
The status of plant and microbial nutrient limitation have profound impacts on ecosystem carbon cycle in permafrost areas, which store large amounts of carbon and experience pronounced climatic warming. Despite the long-term standing paradigm assumes that cold ecosystems primarily have nitrogen deficiency, large-scale empirical tests of microbial n...
Changes in soil nitrogen mineralization can impact nutrient availability, and further affect plant growth. It is unclear, however, how temperature elevation in alpine grassland will affect soil net N mineralization rate (Nmin) across altitudes. At six altitudes (3200 m to 4200 m with an interval of 200 m) along a slope in Lenglong mountain in the n...
Nitrogen regulates multiple aspects of the permafrost climate feedback, including plant growth, organic matter decomposition, and the production of the potent greenhouse gas nitrous oxide. Despite its importance, current estimates of permafrost nitrogen are highly uncertain. Here, we compiled a dataset of >2000 samples to quantify nitrogen stocks i...
Peatlands, with high spatial variability in ecotypes and microforms, constitute a significant part of the boreal landscape and play an important role in the global carbon (C) cycle. However, the effects of this peatland heterogeneity within the boreal landscape are rarely quantified. Here, we use field‐based measurements, high‐resolution land cover...
One of the major uncertainties for projecting permafrost carbon (C)‐climate feedback is a poor representation of the non‐growing season carbon dioxide (CO2) emissions under a changing climate. Here, combining in situ field observations, regional synthesis and a random forest model, we assessed contemporary and future soil respired CO2 (that is, soi...
Effects of permafrost degradation on carbon (C) and nitrogen (N) cycling on the Qinghai‐Tibetan Plateau (QTP) have rarely been analyzed. This study used a revised process‐based biogeochemical model to quantify the effects in the region during the 21st century. We found that permafrost degradation would expose 0.61 ± 0.26 (mean ± SD) and 1.50 ± 0.15...
Atmospheric nitrogen (N) deposition has altered biogeochemical cycles and ecosystem functioning. As a key process involved in carbon and nutrient cycles in terrestrial ecosystems, litter decomposition is sensitive to external N inputs. However, it remains unclear how the interactions of ultraviolet (UV) radiation, soil biodiversity (bacteria, fungi...
Microbial necromass carbon (C) has been considered as an important contributor to persistent soil C pool. However, there still lacks large-scale systematic observations on microbial necromass C in different soil layers, particularly for alpine ecosystems. Besides, it is still unclear whether the relative importance of biotic and abiotic variables s...
Understanding biogeographical patterns and underlying processes of belowground community assembly is crucial for predicting soil functions and their responses to global environmental change. However, little is known about potential differences of belowground community assembly among bacteria, fungi, protists and soil animals, particularly for alpin...
Ecosystem carbon (C) dynamics after permafrost thaw depends on more than just climate change since soil nutrient status may also impact ecosystem C balance. It has been advocated that nitrogen (N) release upon permafrost thaw could promote plant growth and thus offset soil C loss. However, compared with the widely accepted C-N interactions, little...
Temperature sensitivity (Q 10) of permafrost carbon (C) release upon thaw is a vital parameter for projecting permafrost C dynamics under climate warming. However, it remains unclear how mineral protection interacts with microbial properties and intrinsic recalcitrance to affect permafrost C fate. Here, we sampled permafrost soils across a 1000-km...
Elevated reactive nitrogen (N) input could modify soil N transformations, regulating ecosystem functions such as soil N retention and loss. Although multiple hypotheses advocate nonlinear variations in soil N transformations with continuous N input, there still lacks empirical evidences for the responses of soil N transformations to multiple N addi...
Permafrost thaw could trigger the release of greenhouse gases through microbial decomposition of the large quantities of carbon (C) stored within frozen soils. However, accurate evaluation of soil C emissions from thawing permafrost is still a big challenge, partly due to our inadequate understanding about the response of microbial communities and...
Permafrost thaw could induce substantial carbon (C) emissions to the atmosphere, and thus trigger a positive feedback to climate warming. As the engine of biogeochemical cycling, soil microorganisms exert a critical role in mediating the direction and strength of permafrost C‐climate feedback. However, our understanding about the impacts of thermok...
The ecosystem carbon (C) balance in permafrost regions, which has a global significance in understanding the terrestrial C-climate feedback, is significantly regulated by nitrogen (N) dynamics. However, our knowledge on temporal changes in vegetation N limitation (i.e., the supply of N relative to plant N demand) in permafrost ecosystems is still l...
It had been suggested that permafrost thaw could promote frozen nitrogen (N) release and modify microbial N transformation rates, which might alter soil N availability and then regulate ecosystem functions. However, the current understanding of this issue is confined to limited observations in the Arctic permafrost region, without any systematic me...
Microbial stoichiometry and its potential driving factors play crucial roles in understanding the balance of chemical elements in ecological interactions and nutrient limitations along the aridity gradient. However, little is known about the variation in these features along the aridity gradient due to the lack of comprehensive field investigations...
Methane (CH4) dynamics across permafrost regions is critical in determining the magnitude and direction of permafrost carbon (C)-climate feedback. However, current studies are mainly derived from the Arctic area, with limited evidence from other permafrost regions. By combining large-scale laboratory incubation across 51 sampling sites with machine...
Key Points
Dissolved organic carbon (DOC) from thawed permafrost had high biodegradability, with an average of 21.7% loss over a 28‐day incubation
The biodegradability of permafrost‐derived DOC was larger than or equal to that in active‐layer across 72% of sampling sites
Spatial and vertical variations in DOC biodegradability were jointly determine...
Abstract. Microbial stoichiometry and its driving factors play crucial roles in understanding the balance of chemical elements in ecological interactions and nutrient limitations along aridity gradients. However, little is known about the variation in these features along aridity gradients due to the lack of comprehensive field investigations. Addi...
Permafrost thaw, especially thermokarst formation, that is, ground collapse due to thawing of ice‐rich permafrost, is expected to alter soil gross nitrogen (N) transformations, which can regulate plant productivity and ecosystem carbon cycle. However, it remains unclear how thermokarst formation modifies soil N processes in permafrost ecosystems. H...
Aims
Ammonia oxidation and denitrification are crucial for nitrogen (N) availability and nitrous oxide production in N-limited permafrost soils. However, it remains unclear about the relative roles of abiotic and biotic properties in controlling the abundance and activity of ammonia-oxidizing and denitrifying microorganisms in permafrost-affected s...
Abstract Carbon (C) release from thawing permafrost is potentially the largest climate feedback from terrestrial ecosystems. However, the magnitude of this feedback remains highly uncertain, partly due to the limited understanding of how abrupt permafrost thaw (e.g., permafrost collapse) alters soil organic matter (SOM) quality. Here we employed el...
Permafrost soils store a large amount of nitrogen (N) which could be activated under the continuous climate warming. However, compared with carbon (C) stock, little is known about the size and spatial distribution of permafrost N stock. By combining measurements from 519 pedons with two machine learning models (supporting vector machine (SVM) and r...
Permafrost thawing may release nitrous oxide (N2O) due to large N storage in cold environments. However, N2O emissions from permafrost regions have received little attention so far, particularly with respect to the underlying microbial mechanisms. We examined the magnitude of N2O fluxes following upland thermokarst formation along a 20-year thaw se...
Drylands, covering c . 45% of the Earth's terrestrial surface and supporting c . 38% of the global population, play a dominant role in the trend and interannual variability of global land carbon (C) sink. Given that a large proportion of organic C is stored in soils, our knowledge on soil C dynamics in drylands is crucial to evaluate terrestrial C‐...
Aims Soil aggregate is an important component of soil structure, playing an important role in the physical and biological protection mechanism of soil organic carbon (SOC) through isolating SOC from microorganisms. As far as we know, there are few studies, however, on exploring the spatial distribution of soil aggregate at the regional scale. Our o...
Belowground microbial nitrogen (N) processes play key roles in regulating terrestrial ecosystem services such as vegetation production, however, our understanding of their responses to climate change remains limited. We determined patterns and controls of five gross N transformation processes along a typical aridity gradient on the Tibetan Plateau....
Cation exchange capacity (CEC) helps soils hold nutrients and buffer pH, making it vital for maintaining basic function of terrestrial ecosystems. However, little is known about the temporal dynamics of CEC over broad geographical scales. In this study, we used random forest method to compare historical CEC data from the 1980s with new data from th...
AimTo explore large-scale patterns and the drivers of carbon:nitrogen:phosphorus (C:N:P) stoichiometry in heterotrophic microbes. LocationA 3500-km grassland transect on the Tibetan Plateau. Methods
We investigated large-scale C:N:P stoichiometry patterns in the soil microbial biomass and their relationships with abiotic factors and soil microbial...
Our knowledge of fundamental drivers of the temperature sensitivity (Q10) of soil carbon dioxide (CO2) release is crucial for improving the predictability of soil carbon dynamics in Earth System Models. However, patterns and determinants of Q10 over a broad geographic scale are not fully understood, especially in alpine ecosystems. Here, we address...
Subsurface drip irrigation (SDI) and regulated deficit irrigation (RDI) are two of the most water-saving irrigation technologies nowadays. In order to study effects of regulated deficit irrigation on forage water consumption, hay yield and quality of alfalfa under subsurface drip irrigation, a field experiment was carried out in 2012 at Shiyang Riv...