Browsing by Subject "nitrogen"

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  • Grennfelt, Peringe; Engleryd, Anna; Forsius, Martin; Hov, Oystein; Rodhe, Henning; Cowling, Ellis (Springer Nature, 2020)
    Because of its serious large-scale effects on ecosystems and its transboundary nature, acid rain received for a few decades at the end of the last century wide scientific and public interest, leading to coordinated policy actions in Europe and North America. Through these actions, in particular those under the UNECE Convention on Long-range Transboundary Air Pollution, air emissions were substantially reduced, and ecosystem impacts decreased. Widespread scientific research, long-term monitoring, and integrated assessment modelling formed the basis for the policy agreements. In this paper, which is based on an international symposium organised to commemorate 50 years of successful integration of air pollution research and policy, we briefly describe the scientific findings that provided the foundation for the policy development. We also discuss important characteristics of the science–policy interactions, such as the critical loads concept and the large-scale ecosystem field studies. Finally, acid rain and air pollution are set in the context of future societal developments and needs, e.g. the UN’s Sustainable Development Goals. We also highlight the need to maintain and develop supporting scientific infrastructures.
  • Paczkowska, J.; Rowe, Owen; Schluster, L.; Legrand, C.; Karlson, B.; Andersson, A. (2017)
    It is well-known that nutrients shape phytoplankton communities in marine systems, but in coastal waters allochthonous dissolved organic matter (ADOM) may also be of central importance. We studied how humic substances (proxy of ADOM) and other variables influenced the nutritional strategies, size structure and pigment content of the phytoplankton community along a south-north gradient in the Baltic Sea. During the summer, the proportion of mixotrophs increased gradually from the phosphorus-rich south to the ADOM-rich north, probably due to ADOM-fueled microbes. The opposite trend was observed for autotrophs. The chlorophyll a (Chl a): carbon (C) ratio increased while the levels of photoprotective pigments decreased from south to north, indicating adaptation to the darker humic-rich water in the north. Picocyanobacteria dominated in phosphorusrich areas while nanoplankton increased in ADOM- rich areas. During the winter-spring the phytoplankton biomass and concentrations of photoprotective pigments were low, and no trends with respect to autotrophs and mixotrophs were observed. Microplankton was the dominant size group in the entire study area. We conclude that changes in the size structure of the phytoplankton community, the Chl a: C ratio and the concentrations of photoprotective pigments are indicative of changes in ADOM, a factor of particular importance in a changing climate.
  • Grönroos, Juha; Munther, Joonas; Luostarinen, Sari (Finnish Environment Institute, 2017)
    Reports of the Finnish Environment Institute 37/2017
    Agricultural gaseous nitrogen emissions are mostly related to manure management, grazing and fertilisation. These emissions include ammonia (NH3), nitrous oxide (N2O), nitric oxide (NO) and di-nitrogen (N2). Most of the non-methane volatile organic compounds (NMVOC) emissions originate from livestock farming, but also from cultivated crops. All these emissions are inventoried and reported for the UN Convention on Long-range Transboundary Air Pollution (CLRTAP), EU National Emission Ceilings Directive (2001/81/EC) and the UN Framework on Climate Change (UNFCC). In Finland, a specific national model for gaseous nitrogen emissions from agriculture has been used for the inventory since 1998. The revised calculation model documented here is tied to the Finnish Normative Manure System, which provides data on manure quality and quantity for various livestock categories. The emission calculation follows the flow of total ammoniacal nitrogen (TAN) and total nitrogen (N) through the manure management systems, starting from excretion and ending at manure spreading. The main manure management phases considered in the calculation are livestock housing, manure storing and manure field application. The calculation also embeds estimations on emissions from grazing and outdoor yards, as well as emissions from the use of mineral fertilisers. The nitrogen calculation model provides data for the calculation of agricultural NMVOC emissions. All calculations are constructed in compliance with the Tier 2 method of the EMEP/EEA emission inventory guidebook (2016).
  • Khan, Uzair Akbar; Postila, Heini; Kujala, Katharina; Heiderscheidt, Elisangela; Ronkanen, Anna-Kaisa (Elsevier, 2022)
    Ecological Engineering
    The HYDRUS wetland module is widely used together with the biokinetic model CWM1 to simulate reactive transport of contaminants in constructed wetlands. However, this approach has not been used previously to simulate processes in peat-based wetlands operating in cold climates and treating mining-influenced water. In this study, the goal was to clarify changes in flow, transport, and nitrogen removal processes in cold climate treatment peatlands by assessing the performance of HYDRUS-CWM1. Flow and non-reactive transport of tracer, and reactive transport of ammonium, nitrite, and nitrate, in two pilot wetlands operated under controlled conditions representing frozen (winter) and frost-free (summer) periods were simulated. Model simulation outputs were compared against data obtained from the pilot wetlands and from a full-scale treatment peatland treating mining-influenced water in an Arctic region. Initial peaks in tracer concentration were simulated satisfactorily, but transformation and transport of nitrogen species in treatment peatlands, especially under partially frozen conditions, were modeled with only limited success. Limitations of the model and the assumptions made for the simulations have been discussed to highlight the challenges in modeling of treatment peatlands. Highlights • Initial peaks in tracer concentration were simulated satisfactorily. • Transport of nitrogen especially in winter was modeled with limited success. • Limitations of the model and possibilities for improvement are discussed. • Possibility to use multiple HYDRUS add-ons simultaneously may be critical.
  • Aaltonen, Heidi; Tuukkanen, Tapio; Palviainen, Marjo; Laurén, Annamari (Ari); Tattari, Sirkka; Piirainen, Sirpa; Mattsson, Tuija; Ojala, Anne; Launiainen, Samuli; Finér, Leena (2021)
    Understanding the anthropogenic and natural factors that affect runoff water quality is essential for proper planning of water protection and forest management, particularly in the changing climate. We measured water quality and runoff from 10 unmanaged and 20 managed forested headwater catchments (7-12,149 ha) located in Finland. We used linear mixed effect models to test whether the differences in total organic carbon (TOC), total nitrogen (TN) and total phosphorus (TP) export and concentrations observed can be explained by catchment characteristics, land use, forest management, soil fertility, tree volume and hydrometeorological variables. Results show that much of variation in TOC, TN and TP concentrations and export was explained by drainage, temperature sum, peatland percentage and the proportion of arable area in the catchment. These models explained 45-63% of variation in concentrations and exports. Mean annual TOC export in unmanaged catchments was 56.4 +/- 9.6 kg ha(-1) a(-1), while in managed it was 79.3 +/- 3.3 kg ha(-1) a(-1). Same values for TN export were 1.43 +/- 0.2 kg ha(-1) a(-1) and 2.31 +/- 0.2 kg ha(-1) a(-1), while TP export was 0.053 +/- 0.009 kg ha(-1) a(-1) and 0.095 +/- 0.008 kg ha(-1) a(-1) for unmanaged and managed, respectively. Corresponding values for concentrations were: TOC 17.7 +/- 2.1 mg L-1 and 28.7 +/- 1.6 mg L-1, for TN 420 +/- 45 mu g L-1 and 825 +/- 51 mu g L-1 and TP 15.3 +/- 2.3 mu g L-1 and 35.6 +/- 3.3 mu g L-1. Overall concentrations and exports were significantly higher in managed than in unmanaged catchments. Long term temperature sum had an increasing effect on all concentrations and exports, indicating that climate warming may set new challenges to controlling nutrient loads from catchment areas.
  • Allen, John A.; Setälä, Heikki; Kotze, David Johan (2020)
    Urban residents and their pets utilize urban greenspaces daily. As urban dog ownership rates increase globally, urban greenspaces are under mounting pressure even as the benefits and services they provide become more important. The urine of dogs is high in nitrogen (N) and may represent a significant portion of the annual urban N load. We examined the spatial distribution and impact of N deposition from dog urine on soils in three urban greenspace typologies in Finland: Parks, Tree Alleys, and Remnant Forests. We analyzed soil from around trees, lampposts and lawn areas near walking paths, and compared these to soils from lawn areas 8 m away from pathways. Soil nitrate, ammonium, total N concentrations, and electrical conductivity were significantly higher and soil pH significantly lower near path-side trees and poles relative to the 8 m lawn plots. Also, stable isotope analysis indicates that the primary source of path-side N are distinct from those of the 8 m lawn plots, supporting our hypothesis that dogs are a significant source of N in urban greenspaces, but that this deposition occurs in a restricted zone associated with walking paths. Additionally, we found that Remnant Forests were the least impacted of the three typologies analyzed. We recommend that landscape planners acknowledge this impact, and design parks to reduce or isolate this source of N from the wider environment.
  • Macura, Biljana; Piniewski, Mikolaj; Ksiezniak, Marta; Osuch, Pawel; Haddaway, Neal R.; Ek, Filippa; Andersson, Karolin; Tattari, Sirkka (Springer Nature, 2019)
    Environmental Evidence 8, 39 (2019)
    Background Agriculture is the main sector responsible for nutrient emissions in the Baltic Sea Region and there is a growing pressure to identify cost-effective solutions towards reducing nitrogen and phosphorus loads originating from farming activities. Recycling resources from agricultural waste is central to the idea of a circular economy, and has the potential to address the most urgent problems related to nutrients use in the food chain, such as depletion of natural phosphorus reserves, water pollution and waste management. This systematic map examined what evidence exists relating to the effectiveness of ecotechnologies in agriculture for the recovery and reuse of carbon and/or nutrients (nitrogen and phosphorus) in the Baltic Sea region and other comparable boreo-temperate systems. Methods We searched for both academic and grey literature. English language searches were performed in 5 bibliographic databases and search platforms, and Google Scholar. Searches in 36 specialist websites were performed in English, Finnish, Polish and Swedish. The searches were restricted to the period 2013 to 2017. Eligibility screening was conducted at two levels: title and abstract (screened concurrently for efficiency) and full text. Meta-data was extracted from eligible studies including bibliographic details, study location, ecotechnology name and description, type of outcome (i.e. recovered or reused carbon and/or nutrients), type of ecotechnology in terms of recovery source, and type of reuse (in terms of the end-product). Findings are presented here narratively and in a searchable database, and are also visualised in a web-based evidence atlas (an interactive geographical information system). In addition, knowledge gaps and clusters have been identified in the evidence base and described in detail. Results We found 173 articles studying the effectiveness of 177 ecotechnologies. The majority of eligible articles were in English, originated from bibliographic databases and were published in 2016. Most studies with reported locations, and given our boreo-temperate scope, were conducted in Europe and North America. The three most prevalent ecotechnologies in the evidence base (collectively 40.7%) were; soil amendments, anaerobic digestion and (vermi)composting. Manure was the principal waste source used for recovery of nutrients or carbon, making up 55.4% of the all studies in evidence base, followed by a combination of manure and crop residues (22%). There were 51 studies with 14 ecotechnologies that reported on recovery of carbon and nutrients together, predominantly via (vermi)composting and anaerobic digestion. Only 27 studies focused on reuse of recovered nutrients and carbon through soil amendments. Conclusions This systematic map report provides an evidence base that can be useful for researchers and decision-makers in policy and practice working on transformation from linear to circular economy in the agricultural waste sector. Three potential topics for future systematic reviews are: (1) effectiveness of products recovered from different types of agricultural wastes as soil amendments or fertilizers; (2) effectiveness of anaerobic digestion as an ecotechnology used for recovery of nutrients and carbon; (3) effectiveness of composting and/or vermicomposting as ecotechnologies used for recovery of nutrients and carbon.
  • Happel, Elisabeth M.; Trine, Markussen; Teikari, Jonna E.; Huchaiah, Vimala; Alneberg, Johannes; Andersson, Andres F.; Sivonen, Kaarina; Middelboe, Matthias; Kisand, Veljo; Riemann, Lasse (2019)
    Heterotrophic bacteria are important drivers of nitrogen (N) cycling and the processing of dissolved organic matter (DOM). Projected increases in precipitation will potentially cause increased loads of riverine DOM to the Baltic Sea and likely affect the composition and function of bacterioplankton communities. To investigate this, the effects of riverine DOM from two different catchment areas (agricultural and forest) on natural bacterioplankton assemblages from two contrasting sites in the Baltic Sea were examined. Two microcosm experiments were carried out, where the community composition (16S rRNA gene sequencing), the composition of a suite of N-cycling genes (metagenomics) and the abundance and transcription of ammonia monooxygenase (amoA) genes involved in nitrification (quantitative PCR) were investigated. The river water treatments evoked a significant response in bacterial growth, but the effects on overall community composition and the representation of N-cycling genes were limited. Instead, treatment effects were reflected in the prevalence of specific taxonomic families, specific N-related functions and in the transcription of amoA genes. The study suggests that bacterioplankton responses to changes in the DOM pool are constrained to part of the bacterial community, whereas most taxa remain relatively unaffected.
  • Kivela, Jukka; Chen, Lin; Muurinen, Susanna; Kivijarvi, Pirjo; Hintikainen, Veikko; Helenius, Juha (2015)
    Meat and bone meal (MBM) is a by-product of the meat industry and is an important pathway for recycling of N and P. MBM contains about 8% N, 5% P, 1% K and 10% Ca. Field trials compared the effects of MBM and mineral fertilizer on yield and quality of sugar beet (2008-2009) and carrot (2010-2011) in Finland. MBM fertilisation of sugar beet grown on clay loam and sandy clay soil gave 11.4% (2008) and 19.6% (2009) lower yields than mineral fertilizers. The lower root yield in 2008 was compensated by higher extractable sugar content and lower amino-N, K and Na in root but no such compensation in root quality was detected for 2009. Mixing MBM with mineral NPK fertilizers had similar effects as MBM-alone. MBM (80 kg N ha(-1) 2010 and 60 kg N ha(-1) 2011) together with K fertilizer (Patentkali (R), 180 kg K ha(-1)) were applied for carrot to a fine sandy till soil in 2010 and sandy loam in 2011. MBM alone gave 14% lower total and marketable root yield than mineral fertilization. The lower yield was compensated by improved quality, lower NO3- content in the carrot and good storability. Adding extra fertilizer during growth or separating fertilization applications had no effect on root yield or quality. MBM performed in these cases mainly as an organic N fertilizer. The N supply from MBM is not sufficient for achieving same yields as with mineral fertilizers. The relative N efficiency of total N of MBM was 83% that of mineral fertilizers. MBM should be targeted on soils with low P status. We conclude that MBM is a reasonably competitive alternative to mineral fertilizers, and as a recycled fertilizer it is a good option for organic production.
  • Bäcklund, Kirsi (Helsingfors universitet, 2013)
    Boreal forest soil contains large nitrogen resources. Most of the nitrogen is bound to humified material and proteins. However, plants can directly utilize only simple nitrogen compounds as ammonium, nitrate and simple amino acids. The amount of these simple nitrogen compounds is very small in forest soil. Trees form ectomycorrhizal symbiosis with a large number of fungi. Ectomycorrhizal fungi receive carbon compounds from host trees and trees receive nutrients from fungi. Some ectomycorrhizal fungi produce proteases which are enzymes that hydrolyze proteins. This symbiosis might be important in utilizing the large nitrogen resources in forest soils and supplying nitrogen to host plants. The main aim of this study was to measure if ectomycorrhizas produce proteases in the field and to find out if the mycorrhizal protease activities change during the year. The aim was also to find out if proteolytic activity is found in the soil fluid and to see if the activities in soil fluid are related to mycorrhizal activities. Mycorrhizal fungi were isolated to form pure cultures and their protease activities were measured and species were identified. As background information mycorrhizal, nonmycorrhizal and dead root tips were calculated to see how their amounts change during the year. Also different kinds of protease producing mycorrhizal morphotypes were calculated. Samples were taken in Hyytiälä Forestry Field Station in Central Finland monthly from March to October. Fifteen soil cores were collected each month. If possible, eight ectomycorrhizas were randomly picked from the pine roots in the humus layer of each soil core. Protease activities were measured from the ectomycorrhizas and from the soil solution obtained from the homogenized humus layer using Protease Fluorescent Detection Kit (PF0100-1KT, SIGMA). Detection limit of the kit was enzyme activity that is equivalent to 5 ng of trypsin control activity. Results were read from the trypsin standard curve so the protease activities of the samples are equivalent to fluorescence of certain amount of trypsin control. Pure cultures were isolated to Hagem’s agar plates and species were identified by doing PCR from the ITS gene region and sequencing. Root tip and morphotype calculations were done by using a microscope. 12 % of all ectomycorrhizal root tips produced proteases. The smallest activities couldn’t be detected because of the detection limit of the kit. Ectomycorrhizal protease production varied between 0–12 ?g/m2 of soil. Statistically non-significant protease production peaks were observed in spring and autumn. The protease activity of the soil fluid varied mainly between 0–200 ?g/m2 of soil. The highest activity was detected in the frozen soil in March, when the variation was large and an average of 800 ?g of protease was measured per m2 of soil. The protease activities in the soil fluids were not related to the protease activities of the ectomycorrhizas. 17 pure cultures were achieved. Some of them couldn’t be identified to species level. Part of the pure cultures produced proteases. Number of mycorrhizal root tips was large in spring, decreasing in early summer and increasing again towards autumn. About half of the mycorrhizal morphotypes produced proteases. The most important conclusions are that ectomycorrhizal fungi produce proteases in the field and a lot of protease activity is also found in the soil fluid. The used method is sensitive and suitable for measuring protease activities directly from mycorrhizal root tips and soil fluid. Seasonal variation in the protease activities may occur both in mycorrhizas and in soil fluid.
  • Poikane, Sandra; Kelly, Martyn G.; Várbíró, Gábor; Borics, Gábor; Erős, Tibor; Hellsten, Seppo; Kolada, Agnieszka; Lukács, Balázs András; Lyche Solheim, Anne; Pahissa López, José; Willby, Nigel J.; Wolfram, Georg; Phillips, Geoff (Elsevier BV, 2022)
    Science of The Total Environment
    Nutrient targets based on pressure-response models are essential for defining ambitions and managing eutrophication. However, the scale of biogeographical variation in these pressure-response relationships is poorly understood, which may hinder eutrophication management in regions where lake ecology is less intensively studied. In this study, we derive ecology-based nutrient targets for five major ecoregions of Europe: Northern, Central-Baltic, Alpine, Mediterranean and Eastern Continental. As a first step, we developed regressions between nutrient concentrations and ecological quality ratios (EQR) based on phytoplankton and macrophyte communities. Significant relationships were established for 13 major lake types; in most cases, these relationships were stronger for phosphorus than for nitrogen, and stronger for phytoplankton than for macrophytes. Using these regressions, we estimated the total phosphorus (TP) and total nitrogen (TN) concentrations at which lakes of different types are likely to achieve good ecological status. However, in the very shallow lakes of the Eastern Continental region, relations between nutrient and biological communities were weak or non-significant. This can be attributed to high nutrient concentrations (in the asymptotic zone of phosphorus-phytoplankton models) suggesting other factors (light, grazing) limit primary production. However, we also show that fish stocking is a major pressure on Eastern Continental lakes, negatively affecting ecological status: lakes with low fish stocking show low chlorophyll-a concentrations and good ecological status despite high nutrient levels, while the lakes with high fish stocking show high chlorophyll-a and low ecological status. This study highlights the need to better understand lakes in biogeographic regions that have been, for historical reasons, less studied. This, in turn, helps reveal factors that challenge the dominant paradigms of lake assessment and management.
  • Järvinen, Riikka (Helsingin yliopisto, 2022)
    Urban greenspaces are valuable resources for humans and are an integral part of the urban landscape. They are also popular sites for various social and cultural activities, such as dog walking. Dog ownership rates are increasing globally at a rapid rate, hence increasing the dog populations within urban cities. The increasing number of dogs could potentially have negative consequences to the quality of urban parks. Furthermore, there is a lack of research on the impacts of dogs on urban environments. The aim of this study is to gain a better understanding of the impacts of dogs on path-side soils in urban greenspaces. Soil samples were collected from both Helsinki and Lahti. The impact of dog urine was studied by comparing path-side soil samples between areas with high dog activity (i.e., parks) and similar areas with low to no dog activity (i.e., cemeteries). Soil samples were collected three times during the growing season in 2021 at three different treatments: close by 1) an evergreen tree, 2) a lamppost, and 3) a lawn area. The samples were analyzed for soil pH, electrical conductivity, organic matter, soil moisture, NO3--N, and NH4+-N. Net N mineralization and net nitrification rates were also calculated. The results indicated that dog urine is a significant contributor to the input of nitrogen in urban parks. Soil NO3-N and NH4+-N concentrations were significantly higher in parks than in cemeteries and exhibited clear seasonal trends. Soil pH was generally lower and electrical conductivity higher in parks than in cemeteries. Poles and trees exhibited the greatest concentrations, suggesting that the impact of dog urine is highly localized around path-side objects. None of the treatments in cemeteries showed little to no changes throughout the growing season. Lastly, the net nitrification rates were significantly higher in parks during spring and summer. In contrast, net mineralization rates were generally higher in cemeteries than parks. These results confirm that urban planners need to take into consideration the impact of dogs to mitigate any potential negative consequences to the quality of urban parks.
  • Seppälä, J.; Tamminen, T.; Kaitala, S. (Elsevier Science B.V., 1999)
    Phytoplankton nutrient limitation was studied in the Gulf of Riga during spring bloom April 1995., early summer stage June 1994., cyanobacterial bloom July 1994. and post cyanobacterial bloom August 1993.. Each year six factorial nutrient enrichment experiments were carried out in various locations in the Gulf; including outer Irbe Strait, northern Gulf and southern Gulf. The responses of natural phytoplankton communities to the nutrient additions 80 mg NH4-N ly1, 20 mg PO4-P ly1 and two levels of combined additions. were followed for 3 days using 6 l experimental units. To evaluate the nutrient limitation patterns, time series of chlorophyll a were analysed using polynomial regression models and ranking method, taking advantage of the relatively constant experimental error. Apparent nutrient depletion rates and ratios were estimated, and compared with the changes in particulate nutrient ratios. During the spring diatom bloom in 1995, ambient inorganic nutrient concentrations were still high, and thus phytoplankton biomass did not respond to additions of nutrients. Chlorophyll a specific nutrient depletion rates were low 0.01-0.12 mg Nmg chl a.y1 hy1 and 0.002-0.016 mg P mg chl a.y1 hy1. and linear over time, thus also revealing that phytoplankton was not limited by these nutrients in that time. In June 1994, there was an areal shift from N limitation in the outer Irbe Strait towards co-limitation in the southern Gulf. Later in July 1994, during the bloom of N-fixing Aphanizomenon flos-aquae, the N limitation was obvious for the whole study area. For this period chlorophyll a specific nutrient depletion rates were high 0.360.67 mg N mg chl a.y1 hy1 and 0.089-0.135 mg Pmg chl a.y1 hy1., and added nutrients were almost totally depleted during the first light period. After the collapse of cyanobacterial bloom in August 1993, the experiment carried out in the southern Gulf indicated P limitation of phytoplankton. The central Gulf was obviously co-limited, while the area between northern Gulf and outer Irbe Strait was N-limited. Our results indicate that phytoplankton in the Gulf of Riga, earlier considered strictly as P-limited, is at least until late-summer period N- or co-limited. It seems also obvious that there exists a spatial tendency in the phytoplankton limitation patterns, generally from more P- or co-limited southern Gulf towards more N-limited northern basin.
  • Sokka, L.; Antikainen, R.; Kauppi, P.E. (Inderscience Enterprises, 2004)
    Nitrogen (N) and phosphorus (P) are two nutrients contributing to several environmental problems, particularly eutrophication of surface waters. Leakages of these nutrients occur through human activity. In this study, the flows of N and P in the Finnish municipal waste system in 1952–1999 were determined and analysed using substance flow analysis (SFA). Nutrient flows in both wastewaters and solid waste peaked in 1990, after which they declined until 1994 but thereafter increased again although remaining lower than in 1990. At the end of the 1990s the wastewater and solid waste from municipalities and rural households contained ca. 7.0 kg N person–1 a–1 and 1.1 kg P person–1 a–1. Untreated wastewater contained three times more N and four times more P than solid waste. The amounts of N and P involved in recycling increased over the study period being 10% for N and 50% for P at the end of the 1990s.
  • Costello, David M.; Tiegs, Scott D.; Boyero, Luz; Canhoto, Cristina; Capps, Krista A.; Danger, Michael; Frost, Paul C.; Gessner, Mark O.; Griffiths, Natalie A.; Halvorson, Halvor M.; Kuehn, Kevin A.; Marcarelli, Amy M.; Royer, Todd V.; Mathie, Devan M.; Albariño, Ricardo J.; Arango, Clay P.; Aroviita, Jukka; Baxter, Colden V.; Bellinger, Brent J.; Bruder, Andreas; Burdon, Francis J.; Callisto, Marcos; Camacho, Antonio; Colas, Fanny; Cornut, Julien; Crespo‐Pérez, Verónica; Cross, Wyatt F.; Derry, Alison M.; Douglas, Michael M.; Elosegi, Arturo; Eyto, Elvira; Ferreira, Verónica; Ferriol, Carmen; Fleituch, Tadeusz; Follstad Shah, Jennifer J.; Frainer, André; Garcia, Erica A.; García, Liliana; García, Pavel E.; Giling, Darren P.; Gonzales‐Pomar, R. Karina; Graça, Manuel A. S.; Grossart, Hans‐Peter; Guérold, François; Hepp, Luiz U.; Higgins, Scott N.; Hishi, Takuo; Iñiguez‐Armijos, Carlos; Iwata, Tomoya; Kirkwood, Andrea E.; Koning, Aaron A.; Kosten, Sarian; Laudon, Hjalmar; Leavitt, Peter R.; Lemes da Silva, Aurea L.; Leroux, Shawn J.; LeRoy, Carri J.; Lisi, Peter J.; Masese, Frank O.; McIntyre, Peter B.; McKie, Brendan G.; Medeiros, Adriana O.; Miliša, Marko; Miyake, Yo; Mooney, Robert J.; Muotka, Timo; Nimptsch, Jorge; Paavola, Riku; Pardo, Isabel; Parnikoza, Ivan Y.; Patrick, Christopher J.; Peeters, Edwin T. H. M.; Pozo, Jesus; Reid, Brian; Richardson, John S.; Rincón, José; Risnoveanu, Geta; Robinson, Christopher T.; Santamans, Anna C.; Simiyu, Gelas M.; Skuja, Agnija; Smykla, Jerzy; Sponseller, Ryan A.; Teixeira‐de Mello, Franco; Vilbaste, Sirje; Villanueva, Verónica D.; Webster, Jackson R.; Woelfl, Stefan; Xenopoulos, Marguerite A.; Yates, Adam G.; Yule, Catherine M.; Zhang, Yixin; Zwart, Jacob A. (American Geophysical Union (AGU), 2022)
    Global Biogeochemical Cycles
    Microbes play a critical role in plant litter decomposition and influence the fate of carbon in rivers and riparian zones. When decomposing low-nutrient plant litter, microbes acquire nitrogen (N) and phosphorus (P) from the environment (i.e., nutrient immobilization), and this process is potentially sensitive to nutrient loading and changing climate. Nonetheless, environmental controls on immobilization are poorly understood because rates are also influenced by plant litter chemistry, which is coupled to the same environmental factors. Here we used a standardized, low-nutrient organic matter substrate (cotton strips) to quantify nutrient immobilization at 100 paired stream and riparian sites representing 11 biomes worldwide. Immobilization rates varied by three orders of magnitude, were greater in rivers than riparian zones, and were strongly correlated to decomposition rates. In rivers, P immobilization rates were controlled by surface water phosphate concentrations, but N immobilization rates were not related to inorganic N. The N:P of immobilized nutrients was tightly constrained to a molar ratio of 10:1 despite wide variation in surface water N:P. Immobilization rates were temperature-dependent in riparian zones but not related to temperature in rivers. However, in rivers nutrient supply ultimately controlled whether microbes could achieve the maximum expected decomposition rate at a given temperature. Collectively, we demonstrated that exogenous nutrient supply and immobilization are critical control points for decomposition of organic matter. Key Points • Nitrogen (N) and phosphorus (P) immobilization was measured on organic matter (cotton) in 100 rivers and riparian zones representing 11 biomes • Elevated temperature in riparian zones and phosphate in rivers increased immobilization, and consequently accelerated decomposition • N and P immobilization was strongly linked by microbial stoichiometry despite widely varied surface-water nutrient ratios Plain Language Summary Bacteria and fungi contribute to the breakdown of leaf litter in rivers and floodplains. To break down leaf litter, these microbes need the nutrients nitrogen and phosphorus (P), and microbes can get nutrients either from the leaf litter itself or from the environment. Most leaf litter has low nutrient content and microbes must rely on the environment to supply nutrients. We studied microbial nutrient uptake from the environment during litter breakdown to determine whether it varies predictably across the globe and how it is influenced by changing climate and nutrient pollution. In 100 rivers and floodplains in 11 of Earth's major biomes we placed small strips of cotton as stand-ins for leaf litter. Nutrient uptake was consistently greater on cotton strips that were submerged in the river compared to cotton on the floodplain. For microbes in the river, nutrient uptake was faster in instances where there was more P in the water. For microbes in the floodplain, nutrient uptake was faster where temperatures were warmer. Faster nutrient uptake by microbes was linked with faster cotton breakdown in rivers and floodplains. Our study shows that climate change and nutrient pollution can alter the activity of microbes in rivers and floodplains.
  • Wymore, Adam S.; Johnes, Penny J.; Bernal, Susana; Brookshire, E. N. Jack; Fazekas, Hannah M.; Helton, Ashley M.; Argerich, Alba; Barnes, Rebecca T.; Coble, Ashley A.; Dodds, Walter K.; Haq, Shahan; Johnson, Sherri L.; Jones, Jeremy B.; Kaushal, Sujay S.; Kortelainen, Pirkko; López-Lloreda, Carla; Rodríguez-Cardona, Bianca M.; Spencer, Robert G. M.; Sullivan, Pamela L.; Yates, Christopher A.; McDowell, William H. (American Geophysical Union, 2021)
    Global Biogeochemical Cycles, 35(8), e2021GB006953
    A comprehensive cross-biome assessment of major nitrogen (N) species that includes dissolved organic N (DON) is central to understanding interactions between inorganic nutrients and organic matter in running waters. Here, we synthesize stream water N chemistry across biomes and find that the composition of the dissolved N pool shifts from highly heterogeneous to primarily comprised of inorganic N, in tandem with dissolved organic matter (DOM) becoming more N-rich, in response to nutrient enrichment from human disturbances. We identify two critical thresholds of total dissolved N (TDN) concentrations where the proportions of organic and inorganic N shift. With low TDN concentrations (0–1.3 mg/L N), the dominant form of N is highly variable, and DON ranges from 0% to 100% of TDN. At TDN concentrations above 2.8 mg/L, inorganic N dominates the N pool and DON rarely exceeds 25% of TDN. This transition to inorganic N dominance coincides with a shift in the stoichiometry of the DOM pool, where DOM becomes progressively enriched in N and DON concentrations are less tightly associated with concentrations of dissolved organic carbon (DOC). This shift in DOM stoichiometry (defined as DOC:DON ratios) suggests that fundamental changes in the biogeochemical cycles of C and N in freshwater ecosystems are occurring across the globe as human activity alters inorganic N and DOM sources and availability. Alterations to DOM stoichiometry are likely to have important implications for both the fate of DOM and its role as a source of N as it is transported downstream to the coastal ocean.
  • Marttinen, Eeva (Helsingfors universitet, 2010)
    Nitrogen is usually the growth limiting nutrient in boreal forest soils. Most of the nitrogen is bound to organic fraction, and low bioavailability of nitrogen delimits plant growth in boreal forest soils. Amino acids are easily available nitrogen compounds and thus they are important nitrogen sources for soil microorganisms. Almost all boreal forest trees form mycorrhizal assoociations with fungi. Mycorrhizal fungi produce wide variety of enzymes which break down organic nitrogen compounds. So far there is little knowledge of amino acid mineralization mechanisms of ectomycorrhizal fungi. L-amino acid oxidase (LAO) catalyses the mineralization of amino acids to ammonium. The ectomycorrhizal fungi Hebeloma spp. and Laccaria spp. have been shown to possess LAO enzyme activities. It has been proposed that LAO is one of the nitrogen mineralization mechanisms in ectomycorrhizal fungi, but so far no LAO genes have been described from basidiomycete fungi. In this study the first LAO gene sequences from the basidiomycete fungus Hebeloma cylindrosporum was described. The RACE-PCR -method was used to determine the 3´ and 5´ end sequences of the cDNA of the LAO1 gene. Based on the obtained sequences, primers to isolate the genomic DNA and cDNA sequences of the LAO1 gene were designed. The structure of the LAO1 gene, which is composed of five exons and four introns, was determined. Binding site of nitrogen regulating protein was found from upstream region of LAO1-gene. The partial genomic DNA sequence of gene adjacent to LAO1-gene was also measured. In the L. bicolor genome the gene preceding the LAO1 gene has been annotated as a putative pyruvate decarboxylase. In this study the partial cDNA sequence of another LAO-homolog of H. cylindrosporum was also determined. The LAO gene from another basidiomycete fungus, Laccaria bicolor, was also recognised. The gene model of LAO gene of L. bicolor was unannotated in the NCBI database. Based on the phylogenetic tree of LAO-related protein sequences, the ancestral form of LAO gene has been duplicated. This study provides molecular biological information on the catabolic mechanisms of amino acids in ectomycorrhizal fungi. Ammonium ions, produced by ectomycorrhizal fungi, might be a significant source of nitrogen for plants and other soil microbes. It is possible that LAO is an important factor of nitrogen cycle in soils of boreal forests.
  • Kauppi, Katja; Rajala, Ari; Huusela, Erja; Kaseva, Janne; Ruuttunen, Pentti; Jalli, Heikki; Alakukku, Laura; Jalli, Marja (2021)
    The effect of weeds, plant diseases and insect pests on spring barley (Hordeum vulgare) and spring wheat (Triticum aestivum) grain and nutrient yield was examined. Long-term field trial data was used to assess the impact of different pests on grain yield. In the absence of pesticides, fungal diseases caused the largest annual yield-reduction in spring wheat and spring barley, 500 kg ha(-1) on average. Converting yield loss to nutrient yield loss this represented reductions of 8.1 and 9.2 kg ha(-1) in nitrogen and 1.5 and 1.6 kg ha(-1) in phosphorus, respectively. Likewise, it was estimated that weeds decrease the yield of spring barley and spring wheat for 200 kg ha(-1), which means reductions of 3.7 and 3.2 kg ha(-1) in nitrogen and 0.6 kg ha(-1) in phosphorus, respectively. For insect pests yield-reduction in spring barley and spring wheat varied between 418 and 745 kg ha(-1) respectively. However, because bird cherry-oat aphid (Rhopalosiphum padi L.) incidence data was limited, and aphids are highly variable annually, nutrient yield losses caused by insect pests were not included. Based on the current study, the management of weeds, plant diseases and insects maintain cereal crop yield and may thus decrease the environmental risks caused by unutilized nutrients.
  • Jokinen, Henri (Helsingin yliopisto, 2019)
    Dead wood includes everything between small branches and large trunks. Dead wood is created by abiotic and biotic factors like wind, lightning, competition and diseases. The amount of dead wood in Finland varies significantly between managed and natural forests. Approximately 50 % of the biomass of dead wood is carbon and thus dead wood is a notable carbon storage. Carbon may remain in dead wood for decades after the tree death. The amount of nitrogen in dead wood is small and it increases when the decay process proceeds. The aim of this study was to research the amount and quality of dead wood near the SMEAR II -station. The study also examined how the amount of carbon and nitrogen in dead wood varies between tree species and decay classes. Dead wood measurements were done at the ICOS-plots (24 pcs.) near the SMEAR II -station. At every plot there was a measurement area of 60 m2 where every piece of dead wood at the diameter of 2 cm or more was measured. Only dead wood inside the measurement area was measured. The length and top and down diameters of downed dead wood were measured. In case of standing dead wood the length and diameter at breast height were measured. The height and top diameter of stumps were measured as well. The decay class and appearance of dead wood were determined according to national forest inventory´s criteria. Based on the measurements the amount of dead wood at the plots and the whole area was calculated. Dead wood samples were taken from the plots. The samples were dried, milled and their carbon and nitrogen concentrations were analysed. The study revealed that the amount of dead wood in the study area is larger than in managed forests on average. Downed dead wood was the most common dead wood type while standing dead wood was the rarest type. The number of stumps was quite large. The most common species were Scots pine, Norway spruce and birch. The amount of dead wood varied significantly between the plots. The concentration of carbon in dead wood was on average 49 % and there were no differences between tree species and decay classes. The concentration of nitrogen was on average 0,8 % which is relatively high compared to other studies, and the concentration increased with increased decaying. There was a significant variation on nitrogen concentration between decay classes but not between tree species. This study supports other studies´ results that dead wood has an important role on carbon and nitrogen cycling in the forest.
  • Wade, Andrew J.; Skeffington, Richard A.; Couture, Raoul-Marie; Erlandsson Lampa, Martin; Groot, Simon; Halliday, Sarah J.; Harezlak, Valesca; Hejzlar, Josef; Jackson-Blake, Leah A.; Lepistö, Ahti; Papastergiadou, Eva; Riera, Joan Lluís; Rankinen, Katri; Shahgedanova, Maria; Trolle, Dennis; Whitehead, Paul G.; Psaltopoulos, Demetris; Skuras, Dimitris (MDPI AG, 2022)
    Recent studies have demonstrated that projected climate change will likely enhance nitrogen (N) and phosphorus (P) loss from farms and farmland, with the potential to worsen freshwater eutrophication. Here, we investigate the relative importance of the climate and land use drivers of nutrient loss in nine study catchments in Europe and a neighboring country (Turkey), ranging in area from 50 to 12,000 km2. The aim was to quantify whether planned large-scale, land use change aimed at N and P loss reduction would be effective given projected climate change. To this end, catchment-scale biophysical models were applied within a common framework to quantify the integrated effects of projected changes in climate, land use (including wastewater inputs), N deposition, and water use on river and lake water quantity and quality for the mid-21st century. The proposed land use changes were derived from catchment stakeholder workshops, and the assessment quantified changes in mean annual N and P concentrations and loads. At most of the sites, the projected effects of climate change alone on nutrient concentrations and loads were small, whilst land use changes had a larger effect and were of sufficient magnitude that, overall, a move to more environmentally focused farming achieved a reduction in N and P concentrations and loads despite projected climate change. However, at Beyşehir lake in Turkey, increased temperatures and lower precipitation reduced water flows considerably, making climate change, rather than more intensive nutrient usage, the greatest threat to the freshwater ecosystem. Individual site responses did however vary and were dependent on the balance of diffuse and point source inputs. Simulated lake chlorophyll-a changes were not generally proportional to changes in nutrient loading. Further work is required to accurately simulate the flow and water quality extremes and determine how reductions in freshwater N and P translate into an aquatic ecosystem response.