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

Global CO2 fertilization of Sphagnum peat mosses via suppression of photorespiration during the twentieth century

Natural peatlands contribute significantly to global carbon sequestration and storage of biomass, most of which derives from Sphagnum peat mosses. Atmospheric CO2 levels have increased dramatically during the twentieth century, from 280 to > 400 ppm, which has affected plant carbon dynamics. Net carbon assimilation is strongly reduced by photorespiration, a process that depends on the CO2 to O-2 ratio. Here we investigate the response of the photorespiration to photosynthesis ratio in Sphagnum mosses to recent CO2 increases by comparing deuterium isotopomers of historical and contemporary Sphagnum tissues collected from 36 peat cores from five continents. Rising CO2 levels generally suppressed photorespiration relative to photosynthesis but the magnitude of suppression depended on the current water table depth. By estimating the changes in water table depth, temperature, and precipitation during the twentieth century, we excluded potential effects of these climate parameters on the observed isotopomer responses. Further, we showed that the photorespiration to photosynthesis ratio varied between Sphagnum subgenera, indicating differences in their photosynthetic capacity. The global suppression of photorespiration in Sphagnum suggests an increased net primary production potential in response to the ongoing rise in atmospheric CO2, in particular for mire structures with intermediate water table depths

Status for miljøet i norske havområder - Rapport fra Overvåkingsgruppen 2023

I denne rapporten gir Overvåkingsgruppen, for første gang, en felles vurdering av miljøtilstanden i Barentshavet og havområdene utenfor Lofoten, Norskehavet og Nordsjøen med Skagerrak. Det er også første rapport som bruker resultater fra det nylig utviklede fagsystemet for vurdering av økologisk tilstand. I denne rapporten dekkes to hovedtemaer: (1) Dominerende trekk i status og utvikling i økosystemet i alle tre havområdene, basert på vurderingene av økologisk tilstand, Overvåkingsgruppens rapport om forurensning fra 2022, indikatorer fra Overvåkingsgruppen som ikke er dekket under vurdering av økologisk tilstand, samt rapporter og annen relevant informasjon fra forskning, og (2) en vurdering av karbonbinding i marint plankton, marine vegetasjonstyper og marine sedimenter. I tillegg er det gitt en oppsummering for endringer i ytre påvirkning, vurdering av kunnskapsbehov samt en vurdering av indikatorverdier i forhold til referanseverdier og tiltaksgrenser. Vurderingen av dominerende trekk i utvikling og tilstand av miljøet som er gitt i kapittel 2, utgjør Overvåkingsgruppens bidrag til Faglig forums samlerapport om det faglige grunnlaget for revisjon og oppdatering av de helhetlige forvaltningsplanene for norske havområder.Status for miljøet i norske havområder - Rapport fra Overvåkingsgruppen 2023publishedVersio

Phylogenetic or environmental control on the elemental and organo-chemical composition of Sphagnum mosses?

Background and aims: Plant litter chemistry is a key driver of decomposition in peatlands. This study explored the relative contributions of phylogeny and environment to litter chemistry of peat mosses (Sphagnum), the key peat-forming plants on earth. Methods: Fifteen Sphagnum species, representing three taxonomic sections ACUTIFOLIA, CUSPIDATA and SPHAGNUM, were sampled across a wide range of hydro-geochemical conditions. For all species we characterised chemical composition within (i) inorganic elements, (ii) carbohydrate polymers (iii) non-carbohydrates. Results: The variation in carbohydrates was mostly explained by taxonomic section, suggesting phylogenetic conservation of carbohydrate composition. ACUTIFOLIA species invested relatively more in pectins, whereas CUSPIDATA and SPHAGNUM species invested more in hemicellulose. The composition of non-carbohydrates was mainly influenced by environment, except for some constituents for which the variation was more correlated to phylogeny. Finally, the variation in inorganic element concentrations mostly reflected hydro-geochemical conditions within and between peatlands. Conclusions: The separation into an environmentally independent, phylogenetically conserved group of compounds (structural carbohydrates) and an environmentally dependent, variable group of compounds (inorganic elements, non-carbohydrates) has important implications both for understanding patterns in and for upscaling of spatially variable ecosystem processes associated with peat decomposition such as carbon sequestration, nutrient cycling and greenhouse gas emissions

Information States and Dialogues Move Engines

We explore the notion of information state in relation to dialogue systems, and in particular to the part of a dialogue system we call the dialogue move engine. We use a framework for experimenting with information states and dialogue move engines, and show how an experimental dialogue system currently being developed in Gteborg within the framework can be provided with rules to handle accommodation of questions and plans in dialogue

Landscape constraints on mire lateral expansion

Little is known about the long-term expansion of mire ecosystems, despite their importance in the global carbon and hydrogeochemical cycles. It has been firmly established that mires do not expand linearly over time. Despite this, mires are often assumed to have expanded at a constant rate after initiation simply for lack of a better understanding. There has not yet been a serious attempt to determine the rate and drivers of mire expansion at the regional, or larger spatial scales. Here we make use of a natural chronosequence, spanning the Holocene, which is provided by the retreating coastline of Northern Sweden. By studying an isostatic rebound area we can infer mire expansion dynamics by looking at the portion of the landscape where mires become progressively scarce as the land becomes younger. Our results confirms that mires expanded non-linearly across the landscape and that their expansion is related 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 locations in the landscape within only one to two thousand years, while it took mires three to four thousand years to expand into slightly drier areas. Our results imply that the lateral expansion of mires, and thus peat accumulation is a non-linear process, occurring at different rates depending, above all else, on the wetness of the landscape

Global CO2 fertilization of Sphagnum peat mosses via suppression of photorespiration during the twentieth century

Natural peatlands contribute signifcantly to global carbon sequestration and storage of biomass, most of which derives from Sphagnum peat mosses. Atmospheric CO2 levels have increased dramatically during the twentieth century, from 280 to> 400 ppm, which has afected plant carbon dynamics. Net carbon assimilation is strongly reduced by photorespiration, a process that depends on the CO2 to O2 ratio. Here we investigate the response of the photorespiration to photosynthesis ratio in Sphagnum mosses to recent CO2 increases by comparing deuterium isotopomers of historical and contemporary Sphagnum tissues collected from 36 peat cores from fve continents. Rising CO2 levels generally suppressed photorespiration relative to photosynthesis but the magnitude of suppression depended on the current water table depth. By estimating the changes in water table depth, temperature, and precipitation during the twentieth century, we excluded potential efects of these climate parameters on the observed isotopomer responses. Further, we showed that the photorespiration to photosynthesis ratio varied between Sphagnum subgenera, indicating diferences in their photosynthetic capacity. The global suppression of photorespiration in Sphagnum suggests an increased net primary production potential in response to the ongoing rise in atmospheric CO2, in particular for mire structures with intermediate water table depths