Unearthing fine root production by plant functional groups in drained peatlands through in-growth cores

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Responses of fine-root biomass and production to drying depend on wetness and site nutrient regime in boreal forested peatland

IntroductionPeatlands are terrestrial-carbon hotspots, where changes in carbon pools and fluxes potentially caused by drying or warming may have significant feedbacks to climate change. In forested peatlands, fine-root biomass (FRB), and production (FRP) are important carbon pools and fluxes, but they and their depth distribution and plant functional type (PFT) composition are poorly known.MethodsWe studied the effects of persistent water-table level (WTL) drawdown on these characteristics in four forested boreal peatland site types that varied in soil nutrient and WTL regimes, ground vegetation and tree stand characteristics. Each site type was represented by a pair of one undrained and one drained site. Two pairs were nutrient-poor, Scots pine dominated sites, one very wet and one relatively dry in their undrained condition. The other two pairs were nutrient-rich, Norway spruce dominated sites, again one wetter and one drier in the undrained condition. FRB was estimated by separating and visually identifying roots from soil cores extending down to 50 cm depth. FRP was estimated using ingrowth cores covering the same depth, and the separated roots were identified using infrared spectroscopy.Results and discussionBoth FRB and FRP varied widely both within and among the different types of boreal forested peatland. In FRB, the clearest differences were seen in the two originally wettest sites, nutrient-poor tall-sedge pine fen and nutrient-rich herb-rich spruce swamp: FRB was smaller in the drained site compared to the undrained site in the pine fen, but the opposite was true in the spruce swamp. FRP was generally higher in the nutrient-poor, pine-dominated sites than the nutrient-rich, spruce-dominates sites. The depth distribution of FRB was more superficial than that of FRP, except for the most nutrient-rich spruce swamp. Tree and shrub roots dominated both FRB and FRP, except for the undrained pine fen, where graminoids and forbs dominated. Even there, these PFTs were replaced by trees and shrubs at the drained site. Site wetness and nutrient regime both thus clearly regulated FRB and FRP of the forested peatland site types studied, and both need to be considered when making any generalizations

Responses of fine-root biomass and production to drying depend on wetness and site nutrient regime in boreal forested peatland

Introduction: Peatlands are terrestrial-carbon hotspots, where changes in carbon pools and fluxes potentially caused by drying or warming may have significant feedbacks to climate change. In forested peatlands, fine-root biomass (FRB), and production (FRP) are important carbon pools and fluxes, but they and their depth distribution and plant functional type (PFT) composition are poorly known. Methods: We studied the effects of persistent water-table level (WTL) drawdown on these characteristics in four forested boreal peatland site types that varied in soil nutrient and WTL regimes, ground vegetation and tree stand characteristics. Each site type was represented by a pair of one undrained and one drained site. Two pairs were nutrient-poor, Scots pine dominated sites, one very wet and one relatively dry in their undrained condition. The other two pairs were nutrient-rich, Norway spruce dominated sites, again one wetter and one drier in the undrained condition. FRB was estimated by separating and visually identifying roots from soil cores extending down to 50 cm depth. FRP was estimated using ingrowth cores covering the same depth, and the separated roots were identified using infrared spectroscopy. Results and discussion: Both FRB and FRP varied widely both within and among the different types of boreal forested peatland. In FRB, the clearest differences were seen in the two originally wettest sites, nutrient-poor tall-sedge pine fen and nutrient-rich herb-rich spruce swamp: FRB was smaller in the drained site compared to the undrained site in the pine fen, but the opposite was true in the spruce swamp. FRP was generally higher in the nutrient-poor, pine-dominated sites than the nutrient-rich, spruce-dominates sites. The depth distribution of FRB was more superficial than that of FRP, except for the most nutrient-rich spruce swamp. Tree and shrub roots dominated both FRB and FRP, except for the undrained pine fen, where graminoids and forbs dominated. Even there, these PFTs were replaced by trees and shrubs at the drained site. Site wetness and nutrient regime both thus clearly regulated FRB and FRP of the forested peatland site types studied, and both need to be considered when making any generalizations

Fine-root biomass production and its contribution to organic matter accumulation in sedge fens under changing climate

Climate change may affect the carbon sink function of peatlands through warming and drying. Fine-root biomass pro-duction (FRBP) of sedge fens, a widespread peatland habitat, is important in this context, since most of the biomass is below ground in these ecosystems.We examined the response of fine-root biomass production, depth distribution (10 cm intervals down to 60 cm), chem-ical characteristics, and decomposition along with other main litter types (sedge leaves, Sphagnum moss shoots) to an average May-to-October warming of 1.7 degrees C above ambient daily mean temperature and drying of 2-8 cm below ambi-ent soil water-table level (WL) in two sedge fens situated in Northern and Southern Boreal zones. Warming was in-duced with open top chambers and drying with shallow ditching. Finally, we simulated short-term organic matter (OM) accumulation using net primary production and mass loss data. Total FRBP, and FRBP in deeper layers, was clearly higher in southern than northern fen. Drying significantly in-creased, and warming marginally increased,total FRBP, while warming significantly increased, and drying marginally increased, the proportional share of FRBP in deeper layers. Drying, especially, modified root chemistry as the relative proportions of fats, wax, lipids, lignin and other aromatics increased while the proportion of polysaccharides decreased. Warming did not affect the decomposition of any litter types, while drying reduced the decomposition of sedge leaf litter. Although drying increased OM accumulation from root litter at both fens, total OM accumulation decreased at the southern fen, while the northern fen with overall lower values showed no such pattern.Our results suggest that in warmer and/or modestly drier conditions, sedge fen FRBP will increase and/or be allocated to deeper soil layers. These changes along with the altered litter inputs may sustain the soil carbon sink function through OM accumulation, unless the WL falls below a tipping point.Peer reviewe

Fine-root production in boreal peatland forests: Effects of stand and environmental factors

Fine roots are an important component of ecosystem carbon (C) cycling in boreal forests and peatlands. We aimed to estimate fine-root production (FRP) for a range of peatland forests, examine the patterns in, and develop models for estimating, the relationships between FRP and tree stand characteristics as well as environmental conditions. Fine-root production of 28 drained boreal peatland forest sites in Finland, representing different site types and soil water-table conditions, was measured using the ingrowth-core method. Total FRP and FRP of conifers decreased from south to north but long-term mean annual temperature sum and precipitation alone did not significantly explain this trend. Tree stand basal area predicted FRP better than any other stand variable alone, explaining 16 % of the variation in stand-level total FRP. Basal areas of pine and spruce correlated positively with the FRP of conifers. Total FRP varied considerably among the site types and, with the exception of the most fertile site type, decreased with decreasing fertility. A model that included stand basal area and site type accounted for 47% of the variation in stand-level total FRP. Total FRP was generally higher with a deeper water-table level (WT). Together, WT and basal area explained 25 % of the variation in stand-level total FRP. Most FRP occurred in the top 20-cm layer comprising 76–95% of total FRP. The most fertile site type showed lower FRP in deeper layers than the other site types. These results can be used for estimation of FRP with forest inventory data

Estimating fine-root production by tree species and understorey functional groups in two contrasting peatland forests

Background and aims Estimation of root-mediated carbon fluxes in forested peatlands is needed for understanding ecosystem functioning and supporting greenhouse gas inventories. Here, we aim to determine the optimal methodology for utilizing ingrowth cores in estimating annual fine-root production (FRP) and its vertical distribution in trees, shrubs and herbs. Methods We used 3-year data obtained with modified ingrowth core method and tested two calculation methods: 'ingrowth-dividing' and `ingrowth-subtracting'. Results The ingrowth-dividing method combined with a 2-year incubation of ingrowth cores can be used for the 'best estimate' of FRP. The FRP in the nutrient-rich fen forest (561 g m(-2)) was more than twice that in the nutrient-poor bog forest (244 g m(-2)). Most FRP occurred in the top 20-cm layer (76-82 %). Tree FRP accounted for 71 % of total FRP in the bog and 94 % in the fen forests, respectively, following the aboveground vegetation patterns; however, in fen forest the proportions of spruce and birch in FRP were higher than their proportions in stand basal area. Conclusions Our methodology may be used to study peatland FRP patterns more widely and will reduce the volume of labour-intensive work, but will benefit from verification with other methods, as is the case in all in situ FRP studies.Peer reviewe

Examination of air pollutant concentrations in Smart City Helsinki using data exploration and deep learning methods

Air quality has become a major concern for most of the cities around Europe due to rapid urbanization and industrialization. Smart City is an initiative to solve such problems by integrating information and communication technology with citizens. Smart City, through smart computing technologies, allows capturing of huge data and the real picture of the domain problem. Provided by huge sensor data, air quality can be considered an essential component of the Smart City concept. The current thesis utilized the data from the Horizon 2020 mySMARTLife project, in which pollution detection sensors were deployed on public transport vehicles (trams) for continuous monitoring of pollution concentrations such as NO, NO2, CO, and O3 throughout the day. The study applied widely used several deep learning methods such as Convolutional Neural network (CNN), Recurrent Neural Network (RNN), Long Short-Term Memory (LSTM), and Gated Recurrent Unit (GRU) for predicting hourly pollutant concentration based on spatial and meteorological information. The study also proposed an evaluation of features selection with different combinations of features for the model’s performance and showed the accuracy is increased by fusing meteorological variables and temporal feature engineering data. To figure out the best model performance, four evaluation measures such as coefficient of determination (r2), Mean Square Error (MSE), Root Mean Square Error (RMSE), and Mean Absolute Error (MAE) along with model parameter optimization were applied. It is observed that all the models performed comparatively well in prediction at 24-hour window horizons. Particularly, LSTM architecture outperforms all the models in prediction quality having lower MAE values of 0.09, 0.056, 0.096, and 0.114 for NO, NO2, CO, and O3 respectively. Nevertheless, given the computational efficiency of the CNN algorithm, it can substitute deep feedbackward networks such as RNN, LSTM, and GRU models to predict pollutants rapidly and accurately in case of big data

How to estimate fine root production in peat soils?

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Estimating fine-root production by tree species and understorey functional groups in peatland forests

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