Global Change Abstracts The Swiss Contribution - SCNAT

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78 Switzerland, Germany, Australia Forestry, Plant Sciences, Agriculture, Soil Sciences , Ecology Anthropogenic fires affected the temperate deciduous forests of Central Europe over millennia. Biomass burning releases carbon to the atmosphere and produces charcoal, which potentially contributes to the stable soil carbon pools and is an important archive of environmental history. The fate of charcoal in soils of temperate deciduous forests, i.e. the processes of charcoal incorporation and transportation and the effects on soil organic matter are still not clear. We investigated the effects of slash-and-burn at a longterm experimental burning site and determined soil organic carbon and charcoal carbon concentrations as well as the soil lightness of colour (L*) in the topmost soil material (0-1, 1-2.5 and 2.5-5 cm depths) before, immediately after the fire and one year later. The main results are that (i) only a few of the charcoal particles from the forest floor were incorporated into the soil matrix, presumably by soil mixing animals. In the 0-1 cm layer, during one year, the charcoal C concentration increased only by 0.4 g kg(-1) and the proportion of charcoal C to SOC concentration increased from 2.8 to 3.4%; (ii) the SOC concentrations did not show any significant differences; (iii) soil lightness decreased significantly in the topmost soil layer and correlated well with the concentrations of charcoal C (r=-0.87**) and SOC (r=-0.94**) in the samples from the 0-5 cm layer. We concluded that Holocene biomass burning could have influenced soil charcoal concentrations and soil colour. Biogeosciences, 2007, V4, N3, pp 377-383. 08.1-110 Conversion of biomass to charcoal and the carbon mass balance from a slash-and-burn experiment in a temperate deciduous forest Eckmeier E, Rosch M, Ehrmann O, Schmidt M W I, Schier W, Gerlach R Switzerland, Germany Forestry , Plant Sciences , History Anthropogenic burning, including slash-andburn, was deliberately used in (pre)historic Central Europe. Biomass burning has affected the global carbon cycle since, presumably, the early Holocene. The understanding of processes and rates of charcoal formation in temperate deciduous forests is limited, as is the extent of prehistoric human impact on the environment. We took advantage of an experimental burning to simulate Neolithic slash-and-burn, and we quantified the biomass fuel and charcoal produced, determined the resulting distribution of the charcoal Global Change Abstracts – The Swiss Contribution | Terrestrial Ecosystems size fractions and calculated the carbon mass balance. Two-thirds of the charcoal particles (6.71 t / ha) were larger than 2000 Rm and the spatial distribution of charcoal was highly variable (15-90% per m(2)). The conversion rate of the biomass fuel to charcoal mass was 4.8%, or 8.1% for the conversion of biomass carbon to charcoal. Holocene, 2007, V17, N4, MAY, pp 539-542. 08.1-111 Simulating future changes in Arctic and subarctic vegetation Epstein H E, Yu Qin, Kaplan J O, Lischke H USA, Switzerland Modelling , Meteorology & Atmospheric Sciences , Ecology The Arctic is a sensitive system undergoing dramatic changes related to recent warming trends. Vegetation dynamics-increases in the quantity of green vegetation and a northward migration of trees into the arctic tundra-are a component of this change. Although field studies over long time periods can be logistically problematic, simulation modeling provides a means for projecting changes in arctic and subarctic vegetation caused by environmental variations. Computing in Science Engineering, 2007, V9, N4, JUL-AUG, pp 12-23. 08.1-112 Response of soil microbial biomass and community structures to conventional and organic farming systems under identical crop rotations Esperschuetz J, Gattinger A, Mäder P, Schloter M, Fliessbach A Germany, Switzerland Microbiology , Agriculture, Soil Sciences , Plant Sciences , Biodiversity , Ecology In this study the influence of different farming systems on microbial community structure was analyzed using soil samples from the DOK long-term field experiment in Switzerland, which comprises organic (BIODYN and BIOORG) and conventional (CONFYM and CONMIN) farming systems as well as an unfertilized control (NOFERT). We examined microbial communities in winter wheat plots at two different points in the crop rotation (after potatoes and after maize). Employing extended polar lipid analysis up to 244 different phospholipid fatty acids (PLFA) and phospholipid ether lipids (PLEL) were detected. Higher concentrations of PLFA and PLEL in BIODYN and BIOORG indicated a significant influence of organic agriculture on microbial biomass. Farmyard manure (FYM) application consistently revealed the strongest, and the preceding crop the weakest, influence on domain-
Global Change Abstracts – The Swiss Contribution | Terrestrial Ecosystems 79 specific biomass, diversity indices and microbial community structures. Esterlinked PLFA from slowly growing bacteria (k- strategists) showed the strongest responses to long-term organic fertilization. Although the highest fungal biomass was found in the two organic systems of the DOK field trial, their contribution to the differentiation of community structures according to the management regime was relatively low. Prokaryotic communities responded most strongly to either conventional or organic farming management. Fems Microbiology Ecology, 2007, V61, N1, JUL, pp 26-37. 08.1-113 Methodical study of nitrous oxide eddy covariance measurements using quantum cascade laser spectrometery over a Swiss forest Eugster W, Zeyer K, Zeeman M, Michna P, Zingg A, Buchmann N, Emmenegger L Switzerland Forestry , Plant Sciences , Ecology Nitrous oxide fluxes were measured at the Lageren CarboEurope IP flux site over the multi-species mixed forest dominated by European beech and Norway spruce. Measurements were carried out during a four-week period in October-November 2005 during leaf senescence. Fluxes were measured with a standard ultrasonic anemometer in combination with a quantum cascade laser absorption spectrometer that measured N 2O, CO 2, and H 2O mixing ratios simultaneously at 5 Hz time resolution. To distinguish insignificant fluxes from significant ones it is proposed to use a new approach based on the significance of the correlation coefficient between vertical wind speed and mixing ratio fluctuations. This procedure eliminated roughly 56% of our half- hourly fluxes. Based on the remaining, quality checked N 2O fluxes we quantified the mean efflux at 0.8 +/- 0.4 µmol m(-2) h(-1) (mean + /- standard error). Most of the contribution to the N 2O flux occurred during a 6.5-h period starting 4.5 h before each precipitation event. No relation with precipitation amount could be found. Visibility data representing fog density and duration at the site indicate that wetting of the canopy may have as strong an effect on N 2O effluxes as does below-ground microbial activity. It is speculated that above- ground N 2O production from the senescing leaves at high moisture (fog, drizzle, onset of precipitation event) may be responsible for part of the measured flux. Biogeosciences, 2007, V4, N5, pp 927-939. 08.1-114 Improving predictive mapping in Swiss mire ecosystems through re- calibration of indicator values Feldmeyer C E, Ecker K, Kuechler M, Graf U, Waser L Switzerland Ecology , Plant Sciences , Modelling , Forestry Question: How may Landolt indicator values be recalibrated to improve the performance of predictive models? Location: Mires Gross Moos Schwandital (1250 m a.s.l.) in the Prealps, Burgymoos (465 m. a.s.l.) on the Central Plateau and La Burtigniere (1000 m a.s.l.) in the Jura, Switzerland. Methods: Habitat distribution models based on high resolution remotely sensed data and vegetation field data are applied to monitor 130 mires. Instead of plant species or communities we used mean indicator values of vegetation records as response variables. To improve the differential power of indicator values for wetland habitat conditions, we calibrated these values using field data. Different methods were tested with our predictive models in three mires to see which calibration method is best in enhancing model performance. To assess the effect of the uneven distribution of vegetation records along environmental gradients. calibrations based on random and evenly distributed samples were compared. As a test of the predictive power of the models we used r(2) between ground truth and model prediction. This approach is illustrated through an application with nutrient indicator values in the mire La Burtigniere. Results: Model performances were not the same for the three mires. The predictive power was better for the nutrient values, soil reaction and humus values than for light and moisture values. 2000 records were sufficient as basis for re-calibration. Models based on original Landolt indicator values were overall the weakest compared with re-calibrated values. By comparing the predictive power of Models based on randomly or evenly selected records were about equally predictive. Conclusions: 1. A habitat-specific re-calibration of the Landolt indicator values enhances the predictive mapping of the Swiss mire ecosystems. 2. The re-calibration based on weighted averaging gives a better performance than the one based on Gaussian logistic regression. 3. The uneven distribution of indicator values due to the over-representation of mire habitats does not hamper model performance. 4. 2000 vegetation records are a sufficient basis for an optimal re-calibration of the vegetation types. An illustration of the method is given by using the soil fertility pattern of the mire La Burtigniere. Applied Vegetation Science, 2007, V10, N2, AUG, pp 183-192.
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