Nitrogen fertilization increases N2O emission but does not offset the reduced radiative forcing caused by the increased carbon uptake in boreal forests

Net primary production in boreal coniferous forests is generally severely limited by N deficiency. Nitrogen fertilization has thus the potential to strongly increase forest tree biomass production in the boreal region and consequently increase the biosphere uptake of atmospheric CO2. Increased N availability may though increase the production and emission of soil N2O, counteracting the climate mitigation potential from increased forest biomass production. Studies in the boreal region on the net effect on the climate mitigation potential from N fertilization are scarcer than in other biomes. Therefore, we explored how N affected soil GHG fluxes in two boreal field N-loading experiments, of which one is a long-term experiment (40 years), and the other established 6 years before investigation. We also estimated whether the increased soil N2O emission could offset the N-driven increased C sequestration by the trees. Nitrogen additions affected the soil GHG fluxes in both stands. Soil N2O emission was enhanced by N addition at every fertilization rate, though marginally compared to the reduced soil CO2 emission and the increased atmospheric CO2 uptake and biomass production. The estimated annual uptake of CH4 by soil under long-term N addition increased. The magnitude of soil CH4 uptake was on the same order of magnitude as the increase in soil N2O emissions caused by N addition, when compared as CO2 equivalents. In conclusion, forest N fertilization in boreal areas increased the GHG net uptake and, thus, provides a means to mitigate increasing atmospheric concentrations of GHG

Ditches show systematic impacts on soil and vegetation properties across the Swedish forest landscape

Novel mapping methods using AI have led to improved mapping of the extent of drainage systems, but the full scope of the effects of drainage on ecosystems has yet to be understood. By combining ditches mapped with remote sensing and AI methods with soil data from the Swedish Forest Soil Inventory, and vegetation data from the National Forest Inventory we identified 4 126 survey plots within 100 m of a ditch. The inventory data span across three biomes; the northern boreal zone, the hemiboreal zone, and the temperate zone. We explored if soils and vegetation close to ditches were indeed different from the surrounding landscape. The large number of plots spread widely across the Swedish forest landscape spanning different physiographic regions, climates, topography, soils, and vegetation made it possible to identify the general effect of drainage on soil properties, tree productivity, and plant species composition. We found a surprisingly large amount of ditches on mineral soils (50-70%, depending on the definition of peatlands). Forest growth was affected, with higher growth rates of trees closer to ditches, particularly Norway spruce. Sphagnum mosses - a key indicator of wet soils - were less common near ditches, where they were replaced by feather mosses. The soil bulk density was higher closer to ditches, as was the concentration of metals that are typically associated with organic matter (Al), while concentrations of metals with a lower affinity for organic material decreased toward ditches (Na, K, Mg). The results from mineral soils and peat soils often differed. For example, N and tree volume increased toward ditches, but on different levels for peat and mineral soils, while the thickness of the humus layer and Pleurozium schreberi cover showed opposite patterns for the different soils. Clearly, ditches have affected the entire Swedish forest landscape, driving it towards a drier, more spruce-dominated productive forested ecosystem and away from wetland ecosystems like mires and littoral areas along streams. Furthermore, the biogeochemistry of the soils and understory species cover near ditches have changed, potentially irreversibly, at least within human time frames, and have implications for restoration goals and the future of forestry

Cloning of the β-phycocyanin gene from Anacystis nidulans

AbstractThe β-phycocyanin gene, pcyB, of Anacystis nidulans was isolated from an Escherichia coli λ-phage bank by the use of synthetic oligonucleotides derived from the 170 amino acid sequence of the β-phycocyanin protein. Two positive, overlapping λ-clones were found. Partial DNA sequencing of one of the clones gave a deduced amino acid sequence which was in full agreement with a portion of the published sequence of A. nidulans β-phycocyanin. A comparison with the published DNA sequence for β-phycocyanin from Agmenellum quadruplicatum shows a DNA sequence homology of 70.4% over the sequenced region

Topography and Time Shape Mire Morphometry and Large-Scale Mire Distribution Patterns in the Northern Boreal Landscape

Peatlands are major terrestrial soil carbon stores, and open mires in boreal landscapes hold a considerable fraction of the global peat carbon. Despite decades of study, large-scale spatiotemporal analyses of mire arrangement have been scarce, which has limited our ability to scale-up mire properties, such as carbon accumulation to the landscape level. Here, we use a land-uplift mire chronosequence in northern Sweden spanning 9,000 years to quantify controls on mire distribution patterns. Our objectives include assessing changes in the spatial arrangement of mires with land surface age, and understanding modifications by upland hydrotopography. Characterizing over 3,000 mires along a 30 km transect, we found that the time since land emergence from the sea was the dominant control over mire coverage, especially for the establishment of large mire complexes. Mires at the youngest end of the chronosequence were small with heterogenous morphometry (shape, slope, and catchment-to-mire areal ratios), while mires on the oldest surfaces were variable in size, but included larger mires with more complex shapes and smaller catchment-to-mire ratios. In general, complex topography fragmented mires by constraining the lateral expansion, resulting in a greater number of mires, but reduced total mire area regardless of landscape age. Mires in this study area occurred on slopes up to 4%, indicating a hydrological boundary to peatland expansion under local climatic conditions. The consistency in mire responses to spatiotemporal controls illustrates how temporal limitation in peat initiation and accumulation, and topographic constraints to mire expansion together have shaped present day mire distribution patterns

Landscape constraints on mire lateral expansion

Little is known about the long-term expansion of mire ecosystems, despite their importance in the globalcarbon and hydrogeochemical cycles. It has been firmly established that mires do not expand linearlyover time. Despite this, mires are often assumed to have expanded at a constant rate after initiationsimply for lack of a better understanding. There has not yet been a serious attempt to determine the rateand drivers of mire expansion at the regional, or larger spatial scales. Here we make use of a naturalchronosequence, spanning the Holocene, which is provided by the retreating coastline of NorthernSweden. By studying an isostatic rebound area we can infer mire expansion dynamics by looking at theportion of the landscape where mires become progressively scarce as the land becomes younger. Ourresults confirms that mires expanded non-linearly across the landscape and that their expansion isrelated to the availability of suitably wet areas, which, in our case, depends primarily on the hydro-edaphic properties of the landscape. Importantly, we found that mires occupied the wettest locationsin the landscape within only one to two thousand years, while it took mires three to four thousand yearsto expand into slightly drier areas. Our results imply that the lateral expansion of mires, and thus peataccumulation is a non-linear process, occurring at different rates depending, above all else, on thewetness of the landscape

Catchment characteristics control boreal mire nutrient regime and vegetation patterns over ~5000 years of landscape development

Vegetation holds the key to many properties that make natural mires unique, such as surface microtopography, high biodiversity values, effective carbon sequestration and regulation of water and nutrient fluxes across the landscape. Despite this, landscape controls behind mire vegetation patterns have previously been poorly described at large spatial scales, which limits the understanding of basic drivers underpinning mire ecosystem services. We studied catchment controls on mire nutrient regimes and vegetation patterns using a geographically constrained natural mire chronosequence along the isostatically rising coastline in Northern Sweden. By comparing mires of different ages, we can partition vegetation patterns caused by long-term mire succession