Dynamics of alpine plant litter decomposition in a changing climate

Climatic changes resulting from anthropogenic activities over the passed century are repeatedly reported to alter the functioning of pristine ecosystems worldwide, and especially those in cold biomes. Available literature on the process of plant leaf litter decomposition in the temperate Alpine zone is reviewed here, with emphasis on both direct and indirect effects of climate change phenomena on rates of litter decay. Weighing the impact of biotic and abiotic processes governing litter mass loss, it appears that an immediate intensification of decomposition rates due to temperature rise can be retarded by decreased soil moisture, insufficient snow cover insulation, and shrub expansion in the Alpine zone. This tentative conclusion, remains speculative unless empirically tested, but it has profound implications for understanding the biogeochemical cycling in the Alpine vegetation belt, and its potential role as a buffering mechanism to climate chang

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Extraction-Spectrophotometric Studies on the Ion-Pairing Between Some 2,3,5-Substituted Monotetrazolium Cations and Anions Deriving from 4-(2-Thiazolylazo)resorcinol or 4-(2-Pyridylazo)resorcinol

The ion-pairing between some 2,3,5-substituted monotetrazolium cations (T+) and anions deriving from 4-(2-pyridylazo)resorcinol (PAR) or 4-(2-thiazolylazo)resorcinol (TAR) was studied by water-chloroform extraction and spectrophotometry. The following tetrazolium salts (TS) were used as a source of T+: i) 2,3,5-triphenyl-2H-tetrazolium chloride (TTC); ii) 3-(4,5-dimethyl-2-thiazol)-2,5-diphenyl-2H-tetrazolium bromide (MTT); iii) 3-(2-naphtyl)-2,5-diphenyl-2H-tetrazolium chloride (Tetrazolium violet, TV); and iv) 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyl-2H-tetrazolium chloride (INT). The spectral characteristics of the extracted species were established at different pH and TS concentration. The composition and stability of the ion-pairs were determined at pH 9, where the extraction of neutral PAR (H2PAR) and TAR (H2TAR) species was negligible. The results showed that the ion-pairs can be expressed with the following formulae (T+)(HTAR–) (where T+ = TT+, MTT+, TV+ or INT+), (T+)(HPAR–) (where T+ = TT+, MTT+ or TV+) and [(INT+)(HPAR–)]2. Relationships involving the molecular masses of the ion-pairs (MIP) or T+ (MT+) and the values of the constants of association (b) or conditional molar absorptivities (e’) were examined, namely Log b = f(Log MIP) and e’ = f(Log MT+). Some practical aspects concerning the investigation of metal complexes with TS-PAR/TS-TAR were discussed

LIQUID-LIQUID EXTRACTION-SPECTROPHOTOMETRIC DETERMINATION OF MOLYBDENUM USING o-HYDROXYTHIOPHENOLS

27 liquid-liquid extraction-chromogenic systems containing Mo(VI), o-hydroxythiophenol derivative {HTPDs: 2-hydroxy-5-chlorothiophenol (HCTP), 2-hydroxy-5-bromothiophenol (HBTP) or 2-hydroxy-5-iodothiophenol (HITP)} and aromatic amine (AA) were studied. Aniline (An), N-methylaniline (mAn), N,N-dimethylaniline (dAn), o-toluidine (o-Tol), m-toluidine (m-Tol), p-toluidine (p-Tol), 3,4-xylidine (o-Xyl), 2,4-xylidine (m-Xyl), and 2,5-xylidine (p-Xyl) were the examined AAs. Optimization experiments for molybdenum extraction-spectrophotometric determination were performed and the following parameters were found for each of the systems: organic solvent (opt), pH (opt), CHTPD (opt), CAA (opt), shaking time (opt), l (max) and e (max). Under the optimum conditions, the molar ratio of the reacting Mo(V), HTPD and AA was 1:2:2 and the degrees of Mo extraction were R³98.4%. Linear relationships involving the spectral characteristics of the extracted complexes (lmax or emax) and some fundamental properties of the halogen substituent in the HTPD were discussed. The effect of foreign ions was examined and two sensitive, selective and precise procedures for extraction-spectrophotometric determination of molybdenum were proposed. The relative standard deviations for Mo content of (3-5)´10–4 mass % were 4% (HCTP-An procedure) and 3% (HBTP-An procedure)

Subalpine Pasture-Woodlands in a Changing Climate:the Role of Land Use Type in Ecosystem Resistance to Simulated Climate Change

Climate change in temperate mountain systems and associated increase in temperature and decrease in precipitation are expected to have strong implications for vegetation productivity, species diversity and carbon turnover in subalpine grasslands. Little is known, however, about the interaction between the effects of climate change and those of local land use management and possible changes in landscape structure. Pasture woodlands in the Swiss Jura Mountains are a traditional landscape, resulting from a long-lived sustainable use of grasslands and woodlands, and as such provide a suite of important ecosystem services to human society. These range from carbon sequestration and biodiversity preservation, to provision of timber and forage for livestock, and last but not least an aesthetic value, much appreciated by tourism. In this thesis various aspects of ecosystem functioning have been studied, investigating the combined effects of experimental climate change and land use on structurally different wooded pastures. An altitudinal gradient method has been used to simulate future climate change conditions, by imposing warmer and drier climate on subalpine turfs transplanted at lower elevation. The resulting gradient in mean annual temperature and precipitation – ranging from cold and wet in the subalpine zone, to warm and dry in the colline zone – has allowed for the detection of tipping points and altered states of ecosystem functioning in response to the treatments. The method employed provided also the possibility for a direct comparison of three land use types: unwooded pastures, sparsely wooded pastures, and densely wooded pastures (the result of pasture management intensity), in their response to climate perturbation. During the four years of experimental work, a series of observations have been made at the plot scale (square metre) in terms of plant performance and biogeochemical cycles, as well as at the landscape scale (hectare) in terms of forage production. A general threshold level for ecosystem resistance to experimental climate change was detected between the moderate IPCC scenario (+2 K mean annual temperature; -20 % annual precipitation) and the intensive IPCC scenario (+4 K mean annual temperature; -40 % annual precipitation). A concomitant gradient in ecosystem response to climate change was observed across the three land use types. The intensively managed unwooded pasture type was consistently more affected by the experimental treatment and rarely exhibited signs of resistance, especially under the intense climate change scenario. A drastic loss of plant species diversity, reduction of herbaceous biomass, impaired litter decomposition and soil microbial metabolic activity have all contributed to the altered state of ecosystem functioning. In contrast, the two extensively managed wooded pasture types showed considerable resistance to climate perturbation in terms of both above and belowground ecosystem processes. The reported inter-annual variation in herbaceous diversity and biomass production within these land use types demonstrated their resilience (recovery) potential too. Using a modelling approach for upscaling these results to the heterogeneous landscape of pasture woodlands in the Swiss Jura Mountains, has proven that extensively used wooded pastures could grant sustainable ecosystem services in terms of forage provision for cattle under climate change. Considering that the two experimental climate change intensities implemented this study are the projected ‘best’ and ‘worst’ case scenarios for the coming decades, the reported resistance of wooded pastures to climate change has to be embraced, and sustainable land use set as a goal in high altitude mountain pastures

Dynamics of alpine plant litter decomposition in a changing climate

Climatic changes resulting from anthropogenic activities over the passed century are repeatedly reported to alter the functioning of pristine ecosystems worldwide, and especially those in cold biomes. Available literature on the process of plant leaf litter decomposition in the temperate Alpine zone is reviewed here, with emphasis on both direct and indirect effects of climate change phenomena on rates of litter decay. Weighing the impact of biotic and abiotic processes governing litter mass loss, it appears that an immediate intensification of decomposition rates due to temperature rise can be retarded by decreased soil moisture, insufficient snow cover insulation, and shrub expansion in the Alpine zone. This tentative conclusion, remains speculative unless empirically tested, but it has profound implications for understanding the biogeochemical cycling in the Alpine vegetation belt, and its potential role as a buffering mechanism to climate change

Isotopic analysis of cyanobacterial nitrogen fixation associated with subarctic lichen and bryophyte species

Dinitrogen fixation by cyanobacteria is of particular importance for the nutrient economy of cold biomes, constituting the main pathway for new N supplies to tundra ecosystems. It is prevalent in cyanobacterial colonies on bryophytes and in obligate associations within cyanolichens. Recent studies, applying interspecific variation in plant functional traits to upscale species effects on ecosystems, have all but neglected cryptogams and their association with cyanobacteria. Here we looked for species-specific patterns that determine cryptogam-mediated rates of N2 fixation in the Subarctic. We hypothesised a contrast in N2 fixation rates (1) between the structurally and physiologically different lichens and bryophytes, and (2) within bryophytes based on their respective plant functional types. Throughout the survey we supplied 15N-labelled N2 gas to quantify fixation rates for monospecific moss, liverwort and lichen turfs. We sampled fifteen species in a design that captures spatial and temporal variations during the growing season in Abisko region, Sweden. We measured N2 fixation potential of each turf in a common environment and in its field sampling site, in order to embrace both comparativeness and realism. Cyanolichens and bryophytes differed significantly in their cyanobacterial N2 fixation capacity, which was not driven by microhabitat characteristics, but rather by morphology and physiology. Cyanolichens were much more prominent fixers than bryophytes per unit dry weight, but not per unit area due to their low specific thallus weight. Mosses did not exhibit consistent differences in N2 fixation rates across species and functional types. Liverworts did not fix detectable amounts of N2. Despite the very high rates of N2 fixation associated with cyanolichens, large cover of mosses per unit area at the landscape scale compensates for their lower fixation rates, thereby probably making them the primary regional atmospheric nitrogen sin

Extraction of Gallium(III) with a New Azo Dye in The Presence or Absence of Xylometazoline Hydrochloride

Complex formation between Ga(III) and 6-hexyl-4-(2-thiazolylazo)resorcinol (HTAR, H2L) was studied in a water-chloroform medium, in the presence or absence of xylometazoline hydrochloride (XMH). Optimum conditions for the extraction of Ga(III) were found. In the presence of XMH, the extracted ion-associate has the formula (XMH+)[GaIIIL2], where HTAR is in its deprotonated form L2–. Some key extraction-spectrophotometric characteristics were determined: absorption maximum (521 nm), apparent molar absorptivity (5.8 × 104 dm3 mol–1 cm–1), limit of detection (18 ng cm–3), limit of quantitation (60 ng cm–3), extraction constant (LogK = 4.44), distribution ratio (LogD = 2.2) and fraction extracted (99.3 %). In the absence of XMH, the extracted chelate contains one deprotonated and one monoprotonated HTAR: [GaIII(HL–)(L2–)]. It has an absorption maximum at 523 nm and a shoulder at 580–590 nm. The pKa of HTAR (H2L ⇄ H+ + HL– equilibrium) was calculated (5.4) and the effect of foreign ions was studied. This work is licensed under a Creative Commons Attribution 4.0 International License

Liquid-Liquid Extraction-Spectrophotometric Investigations of Three Ternary Complexes of Vanadium(V)

Complex formation and liquid-liquid extraction (LLE) were studied in systems containing vanadi-um(V), 5-methyl-4-(2-thiazolylazo)resorcinol (TAO), tetrazolium salt (TZS), water and chloroform. The following three TZSs were used: 3-(4,5-dimethyl-2-thiazol)-2,5-diphenyl-2H-tetrazolium bromide (MTT), 3-(2-naphtyl)-2,5-diphenyl-2H-tetrazolium chloride (Tetrazolium violet, TV), and 2-(4-iodophenyl)-3-(4-nitrophenyl)-5-phenyl-2H-tetrazolium chloride (INT). Concentration of the reagents (TAO and TZS), pH of the aqueous medium, and shaking time were subjects of optimization experi-ments. Formation of ternary complexes with a composition of 2:2:2 was demonstrated by a set of dif-ferent methods. Some key characteristics concerning the analytical application of the studied LLE-chromogenic systems were established as well

Diminished soil functions occur under simulated climate change in a sup-alpine pasture, but heterotrophic temperature sensitivity indicates microbial resilience

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