1,142 research outputs found
Dynamic simulation of management events for assessing impacts of climate change on pre-alpine grassland productivity
The productivity of permanent temperate cut grasslands is mainly driven by weather, soil characteristics, botanical composition and management. To adapt management to climate change, adjusting the cutting dates to reflect earlier onset of growth and expansion of the vegetation period is particularly important. Simulations of cut grassland productivity under climate change scenarios demands management settings to be dynamically derived from actual plant development rather than using static values derived from current management operations. This is even more important in the alpine region, where the predicted temperature increase is twice as high as compared to the global or Northern Hemispheric average. For this purpose, we developed a dynamic management module that provides timing of cutting and manuring events when running the biogeochemical model LandscapeDNDC. We derived the dynamic management rules from long-term harvest measurements and monitoring data collected at pre-alpine grassland sites located in S Germany and belonging to the TERENO monitoring network. We applied the management module for simulations of two grassland sites covering the period 2011â2100 and driven by scenarios that reflect the two representative concentration pathways (RCP) 4.5 and 8.5 and evaluated yield developments of different management regimes. The management module was able to represent timing of current management operations in high agreement with several years of field observations (r2 > 0.88). Even more, the shift of the first cutting dates scaled to a +1 âŠC temperature increase simulated with the climate change scenarios (â 9.1 to â 17.1 days) compared well to the shift recorded by the German Weather Service (DWD) in the study area from 1991â 2016 (â 9.4 to â 14.0 days). In total, the shift in cutting dates and expansion of the growing season resulted in 1â 2 additional cuts per year until 2100. Thereby, climate change increased yields of up to 6 % and 15 % in the RCP 4.5 and 8.5 scenarios with highest increases mainly found for dynamically adapted grassland management going along with increasing fertilization rates. In contrast, no or only minor yield increases were associated with simulations restricted to fertilization rates of 170 kg N haâ 1 yrâ 1 as required by national legislations. Our study also shows that yields significantly decreased in drought years, when soil moisture is limiting plant growth but due to comparable high precipitation and water holding capacity of soils, this was observed mainly in the RCP 8.5 scenario in the last decades of the century
Dinitrogen emissions: an overlooked key component of the N balance of montane grasslands
While emissions of nitric oxide (NO), ammonia (NHâ) and nitrous oxide (NâO) from grassland soils have been increasingly well constrained, soil dinitrogen (Nâ) emissions are poorly understood. However, Nâ losses might dominate total gaseous nitrogen (N) losses. Knowledge on N losses is key for the development of climate-adapted management that balances agronomic and environmental needs. Hence, we quantified all gaseous N losses from a montane grassland in Southern Germany both for ambient climatic conditions and for a climate change treatment (+ 2°C MAT, - 300 mm MAP). Monthly measurements of soil Nâ emissions of intact soil cores revealed that those exceeded by far soil NâO emissions and averaged at 350 ± 101 (ambient climate) and 738 ± 197 lg N mÂŻÂČhÂŻÂč (climate change). Because these measurements did not allow to quantify emission peaks after fertilization, an additional laboratory experiment was deployed to quantify the response of NHâ, NO, NâO, and Nâ emissions in sub daily temporal resolution to a typical slurry fertilization event (51 kg N haÂŻÂč). Our results revealed that total N gas losses amounted to roughly half of applied slurry-N. Surprisingly, Nâ but not NHâ dominated fertilizer N losses, with Nâ emissions accounting for 16â21 kg or 31â42% of the applied slurry-N, while NHâ volatilization (3.5 kg), N2O (0.2â0.5 kg) and NO losses (0â0.2 kg) were of minor importance. Though constraining annual Nâ loss remained uncertain due to high spatiotemporal variability of fluxes, we show that Nâ losses are a so far overlooked key component of the N balance in montane grasslands, which needs to be considered for developing improved grassland management strategies targeted at increasing N use efficiency
Quantification of C and N trace gas fluxes from a drained peatland forest in Finland using different measuring techniques
Precursors of Cytochrome Oxidase in Cytochrome-Oxidase-Deficient Cells of Neurospora crassa
Three different cell types of Neurospora crassa deficient in cytochrome oxidase were studied: the nuclear mutant cni-1, the cytoplasmic mutant mi-1 and copper-depleted wild-type cells.
* 1.
The enzyme-deficient cells have retained a functioning mitochondrial protein synthesis. It accounted for 12â16% of the total protein synthesis of the cell. However, the analysis of mitochondrial translation products by gel electrophoresis revealed that different amounts of individual membrane proteins were synthesized. Especially mutant cni-1 produced large amounts of a small molecular weight translation product, which is barely detectable in wild-type.
* 2.
Mitochondrial preparations of cytochrome-oxidase-deficient cells were examined for precursors of cytochrome oxidase. The presence of polypeptide components of cytochrome oxidase in the mitochondria was established with specific antibodies. On the other hand, no significant amounts of heme a could be extracted.
* 3.
Radioactively labelled components of cytochrome oxidase were isolated by immunoprecipitation and analysed by gel electrophoresis. All three cell types contained the enzyme components 4â7, which are translated on cytoplasmic ribosomes. The mitochondrially synthesized components 1â3 were present in mi-1 mutant and in copper-depleted wild-type cells. In contrast, components 2 and 3 were not detectable in the nuclear mutant cni-1. Both relative and absolute amounts of these polypeptides in the enzyme-deficient cells were quite different from those in wild-type cells.
* 4.
The components of cytochrome oxidase found in the enzyme-deficient cells were tightly associated with the mitochondrial membranes.
* 5.
Processes, which affect and may control the production of enzyme precursors or their assembly to a functional cytochrome oxidase are discussed
Wirkung von LuftschadstoffeintrÀgen und Klimawandel auf Stoffumsetzungen in Waldökosystemen sowie auf die VitalitÀt und Vielfalt der Waldvegetation
Global Research Alliance N2O chamber methodology guidelines: considerations for automated flux measurement
Nitrous oxide (N2O) emissions are highly episodic in response to nitrogen additions and changes in soil moisture. Automated gas sampling provides the necessary high temporal frequency to capture these emission events in real time, ensuring the development of accurate N2O inventories and effective mitigation strategies to reduce global warming. This paper outlines the design and operational considerations of automated chamber systems including chamber design and deployment, frequency of gas sampling, and options in terms of the analysis of gas samples. The basic hardware and software requirements for automated chambers are described, including the major challenges and obstacles in their implementation and operation in a wide range of environments. Detailed descriptions are provided of automated systems that have been deployed to assess the impacts of agronomy on the emissions of N2O and other significant greenhouse gases. This information will assist researchers across the world in the successful deployment and operation of automated N2O chamber systems
Disentangling gross NâO production and consumption in soil
The difficulty of measuring gross NâO production and consumption in soil impedes our ability to predict NâO dynamics across the soil-atmosphere interface. Our study aimed to disentangle these processes by comparing measurements from gas-flow soil core (GFSC) and NâO pool dilution (NâOPD) methods. GFSC directly measures soil NâO and Nâ fluxes, with their sum as the gross NâO production, whereas NâOPD involves addition of NâO into a chamber headspace and measuring its isotopic dilution over time. Measurements were conducted on intact soil cores from grassland, cropland, beech and pine forests. Across sites, gross NâO production and consumption measured by NâOPD were only 10% and 6%, respectively, of those measured by GFSC. However, NâOPD remains the only method that can be used under field conditions to measure atmospheric NâO uptake in soil. We propose to use different terminologies for the gross NâO fluxes that these two methods quantified. For NâOPD, we suggest using âgross NâO emission and uptakeâ, which encompass gas exchange within the NâO-labelled, soil air-filled pores. For GFSC, âgross NâO production and consumptionâ can be used, which includes both NâO emitted into the soil air-filled pores and NâO directly consumed, forming Nâ, in soil anaerobic microsites
Identifying landscape hot and cold spots of soil greenhouse gas fluxes by combining field measurements and remote sensing data
Upscaling chamber measurements of soil greenhouse gas (GHG) fluxes from point scale to landscape scale remain challenging due to the high variability in the fluxes in space and time. This study measured GHG fluxes and soil parameters at selected point locations (n=268), thereby implementing a stratified sampling approach on a mixed-land-use landscape (âŒ5.8âkm2). Based on these field-based measurements and remotely sensed data on landscape and vegetation properties, we used random forest (RF) models to predict GHG fluxes at a landscape scale (1âm resolution) in summer and autumn. The RF models, combining field-measured soil parameters and remotely sensed data, outperformed those with field-measured predictors or remotely sensed data alone. Available satellite data products from Sentinel-2 on vegetation cover and water content played a more significant role than those attributes derived from a digital elevation model, possibly due to their ability to capture both spatial and seasonal changes in the ecosystem parameters within the landscape. Similar seasonal patterns of higher soil/ecosystem respiration (SR/ERâCO2) and nitrous oxide (N2O) fluxes in summer and higher methane (CH4) uptake in autumn were observed in both the measured and predicted landscape fluxes. Based on the upscaled fluxes, we also assessed the contribution of hot spots to the total landscape fluxes. The identified emission hot spots occupied a small landscape area (7â% to 16â%) but accounted for up to 42â% of the landscape GHG fluxes. Our study showed that combining remotely sensed data with chamber measurements and soil properties is a promising approach for identifying spatial patterns and hot spots of GHG fluxes across heterogeneous landscapes. Such information may be used to inform targeted mitigation strategies at the landscape scale.</p
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