Summary1. Climate change in the subarctic is expected to influence vegetation composition, specifically bryophyte and lichen communities, thereby modifying litter decomposition rates and carbon (C) dynamics of these systems with possible feedbacks to climate. 2. In a 2-year experiment, we investigated decomposition rates and chemical traits of 27 bryophytes, 17 lichens and 5 vascular plants in litter beds in subarctic Sweden. The majority of the sampled cryptogam species are widespread at higher northern latitudes. 3. Average 2-year litter decomposition rates (exponential mass loss constant k) of lichen (0.44 ± 0.01) and vascular plant (0.56 ± 0.03) species were higher than that of bryophytes (0.11 ± 0.01), while within main cryptogam taxa, species identity was an important determinant of mass loss rates. At cryptogam group level, 2-year litter mass loss of Sphagnum was significantly lower than for non-Sphagnum mosses and liverworts. Within lichens, N 2 -fixing versus non-N 2 -fixing lichens showed no variation in decomposability. 4. In a subset of the large species set, mass loss differed both among incubation environments (reflecting nutrient-rich and poor birch forest and Sphagnum peatlands, respectively) and species. The pattern of mass loss across incubation environments was not consistent among cryptogam species. N 2 -fixing, in contrast to non-N 2 -fixing lichens with lower nitrogen (N) levels displayed similar decomposition rates across incubation environments. Mass loss of non-Sphagnum mosses was correlated with initial N irrespective of incubation environment. 5. Litter mass loss of cryptogam taxa could be predicted very well from infrared spectra of the initial chemical composition of the species, by application of Fourier transform infrared using an attenuated total reflectance probe. The initial macronutrient concentrations (N, phosphorus, C and cations) and initial litter pH correlated less well. 6. Synthesis. We showed comprehensively that decomposition rates of bryophytes are generally lower than those of lichens and vascular plants. Among bryophyte or lichen species there is also great variation in litter decomposability which depends strongly on species-specific chemistry. Our data will help predict changing land surface feedback to C cycles and climate in cold biomes by understanding long-term climate effects on litter decomposability through shifting vegetation composition.

A procedure is described for successfully benchmarking different inline spectroscopic techniques in a microreaction plant. The objective was to identify the highest calibration precision for the real-time quantification of the main product. Investigated methods were Raman-, near infrared-, and visible spectroscopy. Besides microreaction technology, the procedure comprises chemometric approaches using statistical experimental design tools and multivariate calibration methods. A calibration model was set up and validated within a defined parameter space (temperature, stoichiometry, and flow rate). The experimental basis was the investigation of toluene nitration using two different nitrating agents. The first reaction was a homogeneous nitration with pure nitric acid as the nitrating agent. It was found that Raman-spectroscopy generates the highest precision. In the second reaction, a heterogeneous liquid-liquid system was obtained using mixed acids. In this case, the precision is very similar for all methods with no preferences for a specific method. As well as investigating the calibration model, additional testing of the observed flow patterns was undertaken for the latter reaction, using the sensitive and very fast AOTF-NIR-spectroscopy.

Nutrient resorption from senescing photosynthetic organs is a powerful mechanism for conserving nitrogen (N) and phosphorus (P) in infertile environments. Evolution has resulted in enhanced differentiation of conducting tissues to facilitate transport of photosynthate to other plant parts, ultimately leading to phloem. Such tissues may also serve to translocate N and P to other plant parts upon their senescence. Therefore, we hypothesize that nutrient resorption efficiency (RE, % of nutrient pool exported) should correspond with the degree of specialization of these conducting tissues across the autotrophic branches of the Tree of Life. To test this hypothesis, we had to compare members of different plant clades and lichens within a climatic region, to minimize confounding effects of climatic drivers on nutrient resorption. Thus, we compared RE among wide-ranging basal clades from the principally N-limited subarctic region, employing a novel method to correct for mass loss during senescence. Even with the limited numbers of species available for certain clades in this region, we found some consistent patterns. Mosses, lichens, and lycophytes generally showed low REN (<20%), liverworts and conifers intermediate (40%) and monilophytes, eudicots, and monocots high (>70%). REP appeared higher in eudicots and liverworts than in mosses. Within mosses, taxa with more efficient conductance also showed higher REN. The differences in REN among clades broadly matched the degree of specialization of conducting tissues. This novel mapping of a physiological process onto the Tree of Life broadly supports the idea that the evolution of conducting tissues toward specialized phloem has aided land plants to optimize their internal nitrogen recycling. The generality of evolutionary lines in conducting tissues and nutrient resorption efficiency needs to be tested across different floras in different climatic regions with different levels of N versus P availability.

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