Metsänhoidon keinot käyttöön ilmastonmuutoksen hillinnässä ja siihen sopeutumisessa

Non peer reviewe

Identifying Nutrient Export Hotspots Using a Spatially Distributed Model in Boreal-Forested Catchments

The implementation of the Water Framework Directive (WFD) aimed to reduce nutrient export from catchments to water courses. Forest operations cause diffuse loading, which challenges the efficient targeting of water protection measures. We formed 100 equally probable clear-cut scenarios, to investigate how the location of the clear-cuts influenced the total nitrogen (TN) and phosphorous (TP) export on different scales. The nutrient export was calculated by using a distributed nutrient export model (NutSpaFHy). The clear-cut-induced excess TN and TP exports varied by 4.2%–5.5% and 5.0%–6.5%, respectively, between the clear-cut scenarios. We analyzed how the sub-catchment characteristics regulated the background export. The results also suggested that there was no single sub-catchment feature, which explained the variation in the TN and TP exports. There were clear differences in the background export and in the clear-cut-induced export between the sub-catchments. We also found that only 5% of the forest area could contribute up to half of the total nutrient export. Based on our results, we presented a conceptual planning framework, which applied the model results to finding areas where the nutrient export was high. Application of this information could improve the overall effectiveness of the water protection measures used in forestry

NutSpaFHy : A Distributed Nutrient Balance Model to Predict Nutrient Export from Managed Boreal Headwater Catchments

Responsible forest management requires accounting for adverse environmental effects, such as increased nutrient export to water courses. We constructed a spatially-distributed nutrient balance model NutSpaFHy that extends the hydrological model SpaFHy by introducing a grid-based nutrient balance sub-model and a conceptual solute transport routine to approximate total nitrogen (N) and phosphorus (P) export to streams. NutSpaFHy uses openly-available Multi-Source National Forest Inventory data, soil maps, topographic databases, location of water bodies, and meteorological variables as input, and computes nutrient processes in monthly time-steps. NutSpaFHy contains two calibrated parameters both for N and P, which were optimized against measured N and P concentrations in runoff from twelve forested catchments distributed across Finland. NutSpaFHy was independently tested against six catchments. The model produced realistic nutrient exports. For one catchment, we simulated 25 scenarios, where clear-cuts were located differently with respect to distance to water body, location on mineral or peat soil, and on sites with different fertility. Results indicate that NutSpaFHy can be used to identify current and future nutrient export hot spots, allowing comparison of logging scenarios with variable harvesting area, location and harvest techniques, and to identify acceptable scenarios that preserve the wood supply whilst maintaining acceptable level of nutrient export

Forest chip drying in self-heating piles during storage as affected by temperature and relative humidity conditions

Storing is an important part in the value chain of the energy use of forest chips as severe losses of dry mass and energy content and increases in greenhouse gas emissions may occur. During the storage the temperature in the biomass increases affecting the dry mass loss and the material drying. In a field-scale experiment, we monitored temperature inside two uncovered wood chip piles for 175 days and measured the chip gravimetric moisture content at the beginning and end of the experiment. In the laboratory the drying rate of the wood chips under different temperature and relative humidity conditions was determined. We constructed a new two-dimensional simulation model where water vapor diffusion within the pile, and chip moisture change was solved using a finite volume method. The determined chip drying rate was used as a source term in the simulation. The simulation model results were in close agreement with the experimental data in the middle sections of the pile, whereas the model was not able to describe the chip moisture redistribution in the pile tails. Modeling revealed that the pile size and porosity were important factors in determining the chip drying, which indicates that chip drying can be controlled by management, such as planning of pile dimensions and compaction.Peer reviewe

Peat macropore networks – new insights into episodic and hotspot methane emission

Peatlands are important natural sources of atmospheric methane (CH4) emissions. The production and emission of CH4 are strongly influenced by the diffusion of oxygen into the soil and of CH4 from the soil to the atmosphere, respectively. This diffusion, in turn, is controlled by the structure of macropore networks. The characterization of peat pore structure and connectivity through complex network theory approaches can give conceptual insight into how the relationship between the microscale pore space properties and CH4 emissions on a macroscopic scale is shaped. The evolution of the pore space that is connected to the atmosphere can also be conceptualized through a pore network modeling approach. Pore regions isolated from the atmosphere may further develop into anaerobic pockets, which are local hotspots of CH4 production in unsaturated peat. In this study, we extracted interconnecting macropore networks from three-dimensional X-ray micro-computed tomography (µCT) images of peat samples and evaluated local and global connectivity metrics for the networks. We also simulated the water retention characteristics of the peat samples using a pore network modeling approach and compared the simulation results with measured water retention characteristics. The results showed large differences in peat macropore structure and pore network connectivity between vertical soil layers. The macropore space was more connected and the flow paths through the peat matrix were less tortuous near the soil surface than at deeper depths. In addition, macroporosity, structural anisotropy, and average pore throat diameter decreased with depth. Narrower and more winding air-filled diffusion channels may reduce the rate of gas transport as the distance from the peat layer to the soil–air interface increases. The network analysis also suggests that both local and global network connectivity metrics, such as the network average clustering coefficient and closeness centrality, might serve as proxies for assessing the efficiency of gas diffusion in air-filled pore networks. However, the applicability of the network metrics was restricted to the high-porosity near-surface layer. The spatial extent and continuity of the pore network and the spatial distribution of the pores may be reflected in different network metrics in contrasting ways. The hysteresis of peat water content between wetting and drying was found to affect the evolution of the volume of connected air-filled pore space in unsaturated peat. Thus, the formation of anaerobic pockets may occur in a smaller soil volume and methanogenesis may be slower when the peat is wetting compared to in drying conditions. This hysteretic behavior might explain the hotspots and episodic spikes of CH4 emissions, and therefore, it should be taken into account in biogeochemical models.Peer reviewe

Exploring the Role of Weather and Forest Management on Nutrient Export in Boreal Forested Catchments Using Spatially Distributed Model

Weather-driven hydrological variability and forest management influence the nutrient export from terrestrial to aquatic systems. We quantified the effect and range of variation in total nitrogen and phosphorus export in Vehka-Kuonanjärvi catchment located in southeastern Finland. A distributed model NutSpaFHy was used with varying weather scenarios (compiled from observed extreme years of dry, wet and wet & mild) and forest management scenarios (including no additional management and intensive clear-cutting of all mature stands in the existing forest structure). Nutrient exports by scenario combinations were compared to modeled baseline export in observed weather. The results showed that the increase in nutrient export by wet & mild weather (over 55%) exceeded the increase caused by the clear-cutting scenario (23 %). Dry weather decreased the exports to tenth of the baseline, which was per hectare 2.22 kg for N, 0.08 kg for P). The results suggest that in future maintaining a good ecological status in aquatic systems can be challenging if extreme wet years with mild winters occur more frequently. Certain catchment characteristics, e.g., deciduous tree percentage, open area percentage and site fertility, influence the export increase induced by the extreme weather. Hotspot analysis enabled identifying areas with currently high nutrient export and areas with high increase induced by the extreme weather. This helps targeting water protection efficiently

Impact of Forest Harvesting Intensity and Water Table on Biodegradability of Dissolved Organic Carbon in Boreal Peat in an Incubation Experiment

Boreal peatlands are vast carbon (C) stores but also major sources of dissolved organic C (DOC) and nutrients to surface waters. Drainage and forest harvesting accelerates DOC leaching. Continuous cover forestry (CCF) is considered to cause fewer adverse environmental effects. Yet, the effects of CCF on DOC processes are unrecognised. We study DOC production and quality in unharvested, CCF, and clear-cut drained peatland forests and in a non-forested alluvial sedge fen. Parallel replicate peat columns with ground vegetation are collected from the uppermost 50 cm at each site, and the water table (WT) is set to −20 or −40 cm depths on the columns. During the eight-month ex situ incubation experiment, the soil water samples are extracted monthly or bi-monthly. The samples are incubated at 15 °C for multiple 72 h incubation cycles to study pore water quality and biodegradation of DOC. The CO2 production occurs during the first three days. The DOC concentrations and the CO2 release per volume of water are significantly lower in the sedge fen than in the drained peatland forests. The WT has a negligible effect on DOC concentrations and no effect on DOC quality, but the higher WT has generally higher CO2 production per DOC than the lower WT. The results suggest that peat in the drained peatlands is not vulnerable to changes per se but that forest management alters biotic and abiotic factors that control the production, transport, and biodegradation of DOC

Impact of Forest Harvesting Intensity and Water Table on Biodegradability of Dissolved Organic Carbon in Boreal Peat in an Incubation Experiment

Boreal peatlands are vast carbon (C) stores but also major sources of dissolved organic C (DOC) and nutrients to surface waters. Drainage and forest harvesting accelerates DOC leaching. Continuous cover forestry (CCF) is considered to cause fewer adverse environmental effects. Yet, the effects of CCF on DOC processes are unrecognised. We study DOC production and quality in unharvested, CCF, and clear-cut drained peatland forests and in a non-forested alluvial sedge fen. Parallel replicate peat columns with ground vegetation are collected from the uppermost 50 cm at each site, and the water table (WT) is set to −20 or −40 cm depths on the columns. During the eight-month ex situ incubation experiment, the soil water samples are extracted monthly or bi-monthly. The samples are incubated at 15 °C for multiple 72 h incubation cycles to study pore water quality and biodegradation of DOC. The CO2 production occurs during the first three days. The DOC concentrations and the CO2 release per volume of water are significantly lower in the sedge fen than in the drained peatland forests. The WT has a negligible effect on DOC concentrations and no effect on DOC quality, but the higher WT has generally higher CO2 production per DOC than the lower WT. The results suggest that peat in the drained peatlands is not vulnerable to changes per se but that forest management alters biotic and abiotic factors that control the production, transport, and biodegradation of DOC

Impact of Forest Harvesting Intensity and Water Table on Biodegradability of Dissolved Organic Carbon in Boreal Peat in an Incubation Experiment

Boreal peatlands are vast carbon (C) stores but also major sources of dissolved organic C (DOC) and nutrients to surface waters. Drainage and forest harvesting accelerates DOC leaching. Continuous cover forestry (CCF) is considered to cause fewer adverse environmental effects. Yet, the effects of CCF on DOC processes are unrecognised. We study DOC production and quality in unharvested, CCF, and clear-cut drained peatland forests and in a non-forested alluvial sedge fen. Parallel replicate peat columns with ground vegetation are collected from the uppermost 50 cm at each site, and the water table (WT) is set to -20 or -40 cm depths on the columns. During the eight-month ex situ incubation experiment, the soil water samples are extracted monthly or bi-monthly. The samples are incubated at 15 degrees C for multiple 72 h incubation cycles to study pore water quality and biodegradation of DOC. The CO2 production occurs during the first three days. The DOC concentrations and the CO2 release per volume of water are significantly lower in the sedge fen than in the drained peatland forests. The WT has a negligible effect on DOC concentrations and no effect on DOC quality, but the higher WT has generally higher CO2 production per DOC than the lower WT. The results suggest that peat in the drained peatlands is not vulnerable to changes per se but that forest management alters biotic and abiotic factors that control the production, transport, and biodegradation of DOC.Peer reviewe

Exploring the Role of Weather and Forest Management on Nutrient Export in Boreal Forested Catchments Using Spatially Distributed Model

Weather-driven hydrological variability and forest management influence the nutrient export from terrestrial to aquatic systems. We quantified the effect and range of variation in total nitrogen and phosphorus export in Vehka-Kuonanjärvi catchment located in southeastern Finland. A distributed model NutSpaFHy was used with varying weather scenarios (compiled from observed extreme years of dry, wet and wet & mild) and forest management scenarios (including no additional management and intensive clear-cutting of all mature stands in the existing forest structure). Nutrient exports by scenario combinations were compared to modeled baseline export in observed weather. The results showed that the increase in nutrient export by wet & mild weather (over 55%) exceeded the increase caused by the clear-cutting scenario (23 %). Dry weather decreased the exports to tenth of the baseline, which was per hectare 2.22 kg for N, 0.08 kg for P). The results suggest that in future maintaining a good ecological status in aquatic systems can be challenging if extreme wet years with mild winters occur more frequently. Certain catchment characteristics, e.g., deciduous tree percentage, open area percentage and site fertility, influence the export increase induced by the extreme weather. Hotspot analysis enabled identifying areas with currently high nutrient export and areas with high increase induced by the extreme weather. This helps targeting water protection efficiently