Shrub and sedge plant functional types (PFTs) were incorporated in the land surface component of the Canadian Earth System Model to improve representation of Arctic tundra ecosystems. Evaluated against 14 years of non-winter measurements, the magnitude and seasonality of carbon dioxide and energy fluxes at a Canadian dwarf-shrub tundra site were better captured by the shrub PFTs than by previously used grass and tree PFTs. Model simulations showed the tundra site to be an annual net CO₂ source.

Vegetation optical depth (VOD), which contains information on vegetation water content and biomass, has been previously shown to be related to gross primary production (GPP). In this study, we analyzed the impact of adding temperature as model input and investigated if this can reduce the previously observed overestimation of VOD-derived GPP. In addition, we could show that the relationship between VOD and GPP largely holds true along a gradient of dry or wet conditions.

The drivers of the onset of autumn leaf senescence for several deciduous tree species are still unclear. Therefore, we addressed (i) if drought impacts the timing of autumn leaf senescence and (ii) if the relationship between drought and autumn leaf senescence depends on the tree species. Our study suggests that the timing of autumn leaf senescence is conservative across years and species and even independent of drought stress.

Biological rock crusts (BRCs) are common microbial-based assemblages covering rocks in drylands. BRCs play a crucial role in arid environments because of the limited activity of plants and soil. Nevertheless, BRC development rates have never been dated. Here we integrated archaeological, microbiological and geological methods to provide a first estimation of the growth rate of BRCs under natural conditions. This can serve as an affordable dating tool in archaeological sites in arid regions.

In the light of climate changes in subarctic regions, notable general increase in above-ground biomass for the past 15 years (2000 to 2017) was estimated along a tundra–taiga gradient of central Chukotka (Russian Far East). The greatest increase occurred in the northern taiga in the areas of larch closed-canopy forest expansion with Cajander larch as a main contributor. For the estimations, we used field data (taxa-separated plant biomass, 2018) and upscaled it based on Landsat satellite data.

Living things decay into organic matter, which can dissolve into water (like tea brewing). Tea receives its color by absorbing light. Similarly, this material absorbs light, which can then cause chemical reactions that change it. By measuring changes in these optical properties, we found that materials from some places are more sensitive to light than others. Comparing sensitivity to light helps us understand where these materials come from and what happens as they move through water.

We present an exhaustive comparative survey of eight proximal methods to estimate forest phenology. We focused on methodological aspects and thoroughly assessed deviations between predicted and observed phenological dates and pointed out their main causes. We show that proximal methods provide robust phenological metrics. They can be used to retrieve long-term phenological series at flux measurement sites and help interpret the interannual variability and trends of mass and energy exchanges.

Organic carbon can be protected from microbial degradation in marine sediments through association with iron minerals on 1000-year timescales. Despite the importance of this carbon sink, our spatial and temporal understanding of iron-bound organic carbon interactions globally is poor. Here we show that caution must be applied when comparing quantification of iron-bound organic carbon extracted by different methods as the extraction strength and method specificity can be highly variable.

We measured nutrients and the naturally occurring nitrogen (N) and oxygen (O) stable isotope ratios of nitrate discharged from a New England river over an annual cycle, to monitor N loading and identify dominant sources from the watershed. We uncovered a seasonality to loading and sources of N from the watershed. Seasonality in the nitrate isotope ratios also informed on N cycling, conforming to theoretical expectations of riverine nutrient cycling.

Our incubation experiment shows that flooding of polluted floodplain soils may induce pulses of both mercury (Hg) and methylmercury to the soil solution and threaten downstream ecosystems. We demonstrate that mobilization of Hg bound to manganese oxides is a relevant process in organic-matter-poor soils. Addition of organic amendments accelerates this mobilization but also facilitates the formation of nanoparticulate Hg and the subsequent fixation of Hg from soil solution to the soil.

CO₂ and H₂O fluxes were measured at a newly established eddy covariance site in southern Finland for 2 years from 2018 to 2020. This agricultural grassland site focuses on the conversion from intensive towards more sustainable agricultural management. The first summer experienced prolonged dry periods, and notably larger fluxes were observed in the second summer. The field acted as a net carbon sink during both study years.

Long-term ocean temperature records are needed to fully understand the impact of West Antarctic Ice Sheet collapse. Glycerol dialkyl glycerol tetraethers (GDGTs) are powerful tools for reconstructing ocean temperature but can be difficult to apply to the Southern Ocean. Our results show active GDGT synthesis in relatively warm depths of the ocean. This research improves the application of GDGT palaeoceanographic proxies in the Southern Ocean.

Hydrogen isotopes could be a useful tool to help resolve the geographic distribution of methane emissions from freshwater environments. We analyzed an expanded global dataset of freshwater methane hydrogen isotope ratios and found significant geographic variation linked to water isotopic composition. This geographic variability could be used to resolve changing methane fluxes from freshwater environments and provide more accurate estimates of the relative balance of global methane sources.

At present, data on the influence of asymmetric warming on the GHG flux on a temporal scale are scarce. GHG fluxes were measured using static chambers and a gas chromatograph. Our study showed that the effect of seasonally asymmetrical warming on CO₂ flux was obvious, with the GHG flux being able to adapt to continuous warming. Warming in the non-growing season increased the temperature dependence of GHG flux.