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This study investigated the effects of substrates composed of various ratios of wood fiber and peat (0, 25, 50, 75, and 100% peat (v/v)) mixed with different amounts of lime (0, 2, 4, 6, and 8 g L[sup.−1]) and start fertilizer (0, 2, and 4 g L[sup.−1] Multimix) on the growth and biomass accumulation of petunia (Petunia x hybrida Vilm ‘Finity F1 Purple’) and basil (Ocimum basilicum L. ‘Marian’) in an ebb-and-flow greenhouse system. Growth parameters included plant height, weight, canopy diameter, and chlorosis symptoms for petunia, along with substrate pH and EC measurements. Petunia showed optimal growth in substrates with higher peat content, while basil produced satisfactory biomass across a pH range of 5–7 regardless of substrate type. Optimal petunia cultivation in 100% wood fiber required a significant dose of start fertilizer without lime. Monitoring pH and EC using pour-through and press methods revealed a pH decrease in substrates with added start fertilizer, while substrates with higher wood fiber content were less acidic. Substrates with over 50% (v/v) wood fiber without lime showed a rapid pH increase over five weeks. The pour-through method generally underestimated EC values compared to the press method. These findings contribute to optimizing the wood fiber/peat blends for sustainable horticulture.

Peatland trees are valuable archives of paleoclimatic information; however, gaps persist in understanding the relationships between tree growth, peatland hydrology, and hydroclimate variables. While previous research in peatlands has mainly focused on tree-ring widths (TRW), yielding inconclusive results, the potential of stable carbon ([delta].sup.13 C) and oxygen ([delta].sup.18 O) isotopes in tree rings remains unexplored. In this study, we develop TRW, [delta].sup.13 C, and [delta].sup.18 O chronologies of Scots pine trees located in a Swedish peatland and a reference site on bedrock with a mineral soil layer. We assess their responses to hydroclimate conditions and evaluate their potential for reconstructing hydroclimate variations. Our findings show significant differences in mean TRW and [delta].sup.13 C values between the peatland and reference sites. Moreover, while TRWs do not exhibit distinct common patterns between sites, both [delta].sup.13 C and [delta].sup.18 O site chronologies show uniform year-to-year variations across all sites. Some discrepancies for TRW and [delta].sup.13 C site chronologies emerge, however, regarding multi-decadal trends. While the climate sensitivity of TRW is weak and non-homogenous, the [delta].sup.13 C and [delta].sup.18 O peatland and reference chronologies contain robust and consistent signals, with a maximum sensitivity to water table, precipitation, and vapor pressure deficit (VPD) variations during summer. Both [delta].sup.13 C and [delta].sup.18 O chronologies show stable relationships with three key hydroclimate variables over time. In conclusion, while TRWs from living peatland pines at our sites have limited potential to record high-frequency hydroclimate information, [delta].sup.13 C and [delta].sup.18 O chronologies can serve as excellent proxies for the reconstruction of past hydroclimate changes.

Drainage in tropical peatlands increases CO.sub.2 emissions, the rate of subsidence, and the risk of forest fires. To a certain extent, these effects can be mitigated by raising the water table depth (WTD) using canal or ditch blocks. The performance of canal blocks in raising WTD is, however, poorly understood because the WTD monitoring data are limited and spatially concentrated around canals and canal blocks. This raises the following question: how effective are canal blocks in raising the WTD over large areas? In this work, we composed a process-based hydrological model to assess the peatland restoration performance of 168 canal blocks in a 22 000 ha peatland area in Sumatra, Indonesia. We simulated daily WTD over 1 year using an existing canal block setup and compared it to the situation without blocks. The study was performed across two contrasting weather scenarios representing dry (1997) and wet (2013) years. Our simulations revealed that, while canal blocks had a net positive impact on WTD rise, they lowered WTD in some areas, and the extent of their effect over 1 year was limited to a distance of about 600 m around the canals. We also show that canal blocks are most effective in peatlands with high hydraulic conductivity. Averaging over all modeled scenarios, blocks raised the annual mean WTD by only 1.5 cm. This value was similar in the dry (1.44 cm) and wet (1.57 cm) years, and there was a 2.13 fold difference between the scenarios with large and small hydraulic conductivities (2.05 cm versus 0.96 cm). Using a linear relationship between WTD and CO.sub.2 emissions, we estimated that, averaging over peat hydraulic properties, canal blocks prevented the emission of 1.07 Mg ha.sup.-1 CO.sub.2 in the dry year and 1.17 Mg ha.sup.-1 CO.sub.2 in the wet year. We believe that the modeling tools developed in this work could be adopted by local stakeholders aiming at a more effective and evidence-based approach to canal-block-based peatland restoration.

The carbon (C) dynamics of northern peatlands are sensitive to hydrological changes owing to ecohydrological feedbacks. We quantified and evaluated the impact of water level variations in a beaver pond (BP) on the CO.sub.2 flux dynamics of an adjacent, raised Sphagnum-shrub-dominated bog in southern Canada. We applied the CoupModel to the Mer Bleue bog, where the hydrological, energy and CO.sub.2 fluxes have been measured continuously for over 20 years. The lateral flow of water from the bog to the BP was estimated by the hydraulic gradient between the peatland and the BP's water level and the vertical profile of peat hydraulic conductivity. The model outputs were compared with the measured hydrological components, CO.sub.2 flux and energy flux data (1998-2019). CoupModel was able to reproduce the measured data well. The simulation shows that variation in the BP water level (naturally occurring or due to management) influenced the bog net ecosystem exchange (NEE) of CO.sub.2 . Over 1998-2004, the BP water level was 0.75 to 1.0 m lower than during 2017-2019. Simulated net CO.sub.2 uptake was 55 gCm-2yr-1 lower during 1998-2004 compared to 2017-2019 when there was no BP disturbance, which was similar to the differences in measured NEE between those periods. Peatland annual NEE was well correlated with water table depth (WTD) within the bog, and NEE also shows a linear relation with the water level at the BP, with a slope of -120 gCO2-Cm-2yr-1m-1. The current modelling predicts that the bog may switch from CO.sub.2 sink to source when the BP water levels drop lower than â¼ 1.7 m below the peat surface at the eddy covariance (EC) tower, located on the bog surface 250 m from the BP. This study highlights the importance of natural and human disturbances to adjacent water bodies in regulating the net CO.sub.2 uptake function of northern peatlands.

In this paper, the pathway from peat resources to their various forms of utilization, to their environmental impacts, and to their mitigation is discussed. Overall, research gaps related to various fields of peat studies are identified and recommendations for future research are presented. Global peat reserves are large, but they remain mostly unused. Peat can also be valorized in various less GHG–intensive applications beyond combustion. Heterogenocity of peat may constraint many of these uses, warranting new innovations to support their feasibility. The theme of GHG emissions from peatlands is complex. The future of northern peatlands as carbon sinks remains uncertain. Paludiculture, an emerging research field, and its GHG mitigation potential is also discussed. When discussing peat production, one of its main adverse effects typically disclosed is its impact on the water quality of natural aquatic systems. Thus, different traditional and novel peat bog drainage water treatment methods are extensively compared with each other — a topic not previously presented in the literature. Peatland restoration and its novel applications, as well as economic aspects, are also addressed. Socioeconomic aspects of peat use, closely linked to climate, food, and rural livelihoods, are currently under vigorous research, and are also examined.

Field measurements combined with remotely sensed data reveal the Cuvette Centrale in the central Congo Basin to contain the most extensive peatland complex in the tropics, increasing the best estimate of global tropical peatland carbon stocks by approximately one-third. Carbon storage in tropical peatlands Peatlands store large amounts of carbon. They are mostly located in cool climatic regions, but peat deposits have also been identified in tropical forest regions. This study finds that the Cuvette Centrale depression in the central Congo Basin is home to the most extensive peatland complex in the tropics. The authors estimate that the amount of carbon in these peatlands may increase global tropical peatland carbon stocks by about a third. Peatlands are carbon-rich ecosystems that cover just three per cent of Earth’s land surface 1 , but store one-third of soil carbon 2 . Peat soils are formed by the build-up of partially decomposed organic matter under waterlogged anoxic conditions. Most peat is found in cool climatic regions where unimpeded decomposition is slower, but deposits are also found under some tropical swamp forests 2 , 3 . Here we present field measurements from one of the world’s most extensive regions of swamp forest, the Cuvette Centrale depression in the central Congo Basin 4 . We find extensive peat deposits beneath the swamp forest vegetation (peat defined as material with an organic matter content of at least 65 per cent to a depth of at least 0.3 metres). Radiocarbon dates indicate that peat began accumulating from about 10,600 years ago, coincident with the onset of more humid conditions in central Africa at the beginning of the Holocene 5 . The peatlands occupy large interfluvial basins, and seem to be largely rain-fed and ombrotrophic-like (of low nutrient status) systems. Although the peat layer is relatively shallow (with a maximum depth of 5.9 metres and a median depth of 2.0 metres), by combining in situ and remotely sensed data, we estimate the area of peat to be approximately 145,500 square kilometres (95 per cent confidence interval of 131,900–156,400 square kilometres), making the Cuvette Centrale the most extensive peatland complex in the tropics. This area is more than five times the maximum possible area reported for the Congo Basin in a recent synthesis of pantropical peat extent 2 . We estimate that the peatlands store approximately 30.6 petagrams (30.6 × 10 15  grams) of carbon belowground (95 per cent confidence interval of 6.3–46.8 petagrams of carbon)—a quantity that is similar to the above-ground carbon stocks of the tropical forests of the entire Congo Basin 6 . Our result for the Cuvette Centrale increases the best estimate of global tropical peatland carbon stocks by 36 per cent, to 104.7 petagrams of carbon (minimum estimate of 69.6 petagrams of carbon; maximum estimate of 129.8 petagrams of carbon 2 ). This stored carbon is vulnerable to land-use change and any future reduction in precipitation 7 , 8 .

The function of tropical peatland as a carbon sink is a balance between peat accumulation and peat loss; however, various interacting factors are involved affecting this process. In this study, we collected and intensively radiocarbon dated peat cores from two peat domes, visualized their cross-sectional profiles of geochemical properties, and developed three macrocharcoal records from each peat dome. We find that the young (4500 y calBP) and shallow (6 m) coastal peat has a simple and linear age–depth relationship, showing stable accumulation of carbon during the late Holocene. In contrast, the older (ca. 40,000 y cal BP) and deeper (15 m) inland peat shows a more complex history, where we observed age reversals and hiatuses, likely caused by climate variability from the Last Glacial Maximum (LGM) to the Holocene. The charcoal record reveals a continuous presence of low-severity fire as indicated by charcoal morphotypes, though fire frequency increased after agriculture was established. An age reversal during the LGM was likely caused by a flood. Two periods of hiatuses occurred, each several millennia in length, at the end of the LGM and during the early Holocene. One cause of the hiatuses may have been a climatically halted peat formation from low precipitation and cooler climate during the LGM. Another cause may have been that severe fires consumed thousands of years of accumulated peat. If the hiatuses were entirely due to fire, the carbon released from these paleo-fire events (600 t C ha−1) suggests several times the impact of the most intense modern peat fires.

Nanhermannia coronata is a common and abundant oribatid species in peatlands, but it can be easily mistaken for N. sellnicki as an adult. The identity of adults of N. coronata investigated herein from several sites in Norway and Ireland was supported by the COI sequence data. Based on this material, the morphological ontogeny of N. coronata was investigated, and some characters were found that clearly differentiate N. coronata from N. sellnicki, like the number of setae on femora of adults and tritonymphs, the shape of insertions of prodorsal seta in and all gastronotal and adanal setae of juveniles. Our ecological observations confirm a common occurrence of N. coronata in raised bogs, a high percentage of juvenile stages in populations and a preference of this species for humid microhabitats, whereas N. sellnicki is less common than N. coronata and occurs in drier habitats. Nanhermannia coronata Berlese, 1913, is a common and abundant oribatid species in peatlands but can be easily mistaken for N. sellnicki Forsslund, 1958, as an adult. Therefore, the identity of adults of N. coronata from several sites in Norway and Ireland was supported by the COI sequence data, and based on this material, the morphological ontogeny of this species is described and illustrated to highlight the differences between N. coronata and N. sellnicki. In all juvenile stages of N. coronata, the bothridial seta is absent, but two pairs of exobothridial setae are present, including short exp and exa reduced to its alveolus. In the larva, seta f[sub.1] is setiform, but in the nymphs, it is reduced to its alveolus. Most prodorsal and gastronotal setae of larva are short, and of nymphs they are long. In all instars, the leg segments are oval in cross section and relatively thick, and many setae on tarsi are relatively short, thick and conical, except for longer apical setae. Seta d accompanies solenidion σ on all genua, φ[sub.1] on tibia I and φ on other tibiae. We found some morphological characters that clearly differentiate N. coronata from N. sellnicki, like the number of setae on femora of adults and tritonymphs, the shape of insertions of prodorsal seta in and all gastronotal and adanal setae of juveniles; in N. sellnicki, these setae are inserted in small individual depressions, whereas in N. coronata, these depressions are absent. Our ecological observations confirm a common occurrence of N. coronata in raised bogs, a high percentage of juvenile stages in its populations and a preference of this species for humid microhabitats, whereas N. sellnicki is less common than N. coronata and occurs in drier habitats.

We investigated recent changes in spatial patterning of fen and bog zones in five boreal aapa mire complexes (mixed peatlands with patterned fen and bog parts) in a multiproxy study. Comparison of old (1940–1970s) and new aerial images revealed decrease of flarks (wet hollows) in patterned fens by 33–63% in middle boreal and 16–42% in northern boreal sites, as lawns of bog Sphagnum mosses expanded over fens. Peat core transects across transformed areas were used to verify the remote sensing inference with stratigraphic analyses of macrofossils, hyperspectral imaging, and age-depth profiles derived from 14C AMS dating and pine pollen density. The transect data revealed that the changes observed by remote sensing during past decades originated already from the end of the Little Ice Age (LIA) between 1700–1850 CE in bog zones and later in the flarks of fen zones. The average lateral expansion rate of bogs over fen zones was 0.77 m y−1 (range 0.19–1.66) as estimated by remote sensing, and 0.71 m y−1 (range 0.13–1.76) based on peat transects. The contemporary plant communities conformed to the macrofossil communities, and distinct vegetation zones were recognized as representing recently changed areas. The fen-bog transition increased the apparent carbon accumulation, but it can potentially threaten fen species and habitats. These observations indicate that rapid lateral bog expansion over aapa mires may be in progress, but more research is needed to reveal if ongoing fen-bog transitions are a commonplace phenomenon in northern mires.

Peatlands are a significant component of the global carbon (C) cycle, yet despite their role as a long-term C sink throughout the Holocene, they are increasingly vulnerable to destabilization. Nowhere is this shift from sink to source happening more rapidly than in Southeast Asia, and nowhere else are the combined pressures of land-use change and fire on peatland ecosystem C dynamics more evident nor the consequences more apparent. This review focuses on the peatlands of this region, tracing the link between deforestation and drainage and accelerating C emissions arising from peat mineralization and fire. It focuses on the implications of the recent increase in fire occurrence for air quality, human health, ecosystem resilience and the global C cycle. The scale and controls on peat-driven C emissions are addressed, noting that although fires cause large, temporary peaks in C flux to the atmosphere, year-round emissions from peat mineralization are of a similar magnitude. The review concludes by advocating land management options to reduce future fire risk as part of wider peatland management strategies, while also proposing that this region's peat fire dynamic could become increasingly relevant to northern peatlands in a warming world. This article is part of the themed issue ‘The interaction of fire and mankind’.