TY  - JOUR
A1  - Tötzke, Christian
A1  - Cermak, Jan
A1  - Nadezhdina, Nadezhda
A1  - Tributsch, Helmut
T1  - Electrochemical in-situ studies of solar mediated oxygen transport and turnover dynamics in a tree trunk of Tilia cordata
JF  - iForest - Biogeosciences and Forestry
N2  - Platinum electrodes were implanted into the xylem of a lime tree (Tilia cordata) stem and solar- induced electrochemical potential differences of up to 120 mV were measured during the vegetative period and up to 30 mV in winter. The time dependent curves were found to be delayed with respect to solar radiation, sap flow activity, temperature and vapor pressure deficit. A general equation for the potential difference was derived and simplified by analyzing the effect of temperature and tensile strength. The potential determining influence of oxygen concentration on the respective location of the platinum electrode was identified as the principal phenomenon measured. A systematic analysis and investigation of the observed periodic oxygen concentration signals promises new information on sap flow, oxygen diffusion through tree tissues and on oxygen consumption related to the energy turnover in tree tissues.
KW  - Tree Stems
KW  - Oxygen Transport
KW  - Xylem
KW  - Sap Flow
KW  - Tree Metabolism
KW  - Electrical Potential
Y1  - 2017
U6  - https://doi.org/10.3832/ifor1681-010
SN  - 1971-7458
VL  - 10
IS  - 2
SP  - 355
EP  - 361
PB  - SISEF - The Italian Society of Silviculture and Forest Ecology
CY  - Potenza
ER  - 
TY  - JOUR
A1  - Frieler, Katja
A1  - Schauberger, Bernhard
A1  - Arneth, Almut
A1  - Balkovic, Juraj
A1  - Chryssanthacopoulos, James
A1  - Deryng, Delphine
A1  - Elliott, Joshua
A1  - Folberth, Christian
A1  - Khabarov, Nikolay
A1  - Müller, Christoph
A1  - Olin, Stefan
A1  - Pugh, Thomas A. M.
A1  - Schaphoff, Sibyll
A1  - Schewe, Jacob
A1  - Schmid, Erwin
A1  - Warszawski, Lila
A1  - Levermann, Anders
T1  - Understanding the weather signal in national crop-yield variability
JF  - Earths future
N2  - Year-to-year variations in crop yields can have major impacts on the livelihoods of subsistence farmers and may trigger significant global price fluctuations, with severe consequences for people in developing countries. Fluctuations can be induced by weather conditions, management decisions, weeds, diseases, and pests. Although an explicit quantification and deeper understanding of weather-induced crop-yield variability is essential for adaptation strategies, so far it has only been addressed by empirical models. Here, we provide conservative estimates of the fraction of reported national yield variabilities that can be attributed to weather by state-of-the-art, process-based crop model simulations. We find that observed weather variations can explain more than 50% of the variability in wheat yields in Australia, Canada, Spain, Hungary, and Romania. For maize, weather sensitivities exceed 50% in seven countries, including the United States. The explained variance exceeds 50% for rice in Japan and South Korea and for soy in Argentina. Avoiding water stress by simulating yields assuming full irrigation shows that water limitation is a major driver of the observed variations in most of these countries. Identifying the mechanisms leading to crop-yield fluctuations is not only fundamental for dampening fluctuations, but is also important in the context of the debate on the attribution of loss and damage to climate change. Since process-based crop models not only account for weather influences on crop yields, but also provide options to represent human-management measures, they could become essential tools for differentiating these drivers, and for exploring options to reduce future yield fluctuations.
Y1  - 2017
U6  - https://doi.org/10.1002/2016EF000525
SN  - 2328-4277
VL  - 5
SP  - 605
EP  - 616
PB  - Wiley
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Hodgkins, Suzanne B.
A1  - Richardson, Curtis J.
A1  - Dommain, Rene
A1  - Wang, Hongjun
A1  - Glaser, Paul H.
A1  - Verbeke, Brittany
A1  - Winkler, B. Rose
A1  - Cobb, Alexander R.
A1  - Rich, Virginia I.
A1  - Missilmani, Malak
A1  - Flanagan, Neal
A1  - Ho, Mengchi
A1  - Hoyt, Alison M.
A1  - Harvey, Charles F.
A1  - Vining, S. Rose
A1  - Hough, Moira A.
A1  - Moore, Tim R.
A1  - Richard, Pierre J. H.
A1  - De la Cruz, Florentino B.
A1  - Toufaily, Joumana
A1  - Hamdan, Rasha
A1  - Cooper, William T.
A1  - Chanton, Jeffrey P.
T1  - Tropical peatland carbon storage linked to global latitudinal trends in peat recalcitrance
JF  - Nature Communications
N2  - Peatlands represent large terrestrial carbon banks. Given that most peat accumulates in boreal regions, where low temperatures and water saturation preserve organic matter, the existence of peat in (sub)tropical regions remains enigmatic. Here we examined peat and plant chemistry across a latitudinal transect from the Arctic to the tropics. Near-surface low-latitude peat has lower carbohydrate and greater aromatic content than near-surface high-latitude peat, creating a reduced oxidation state and resulting recalcitrance. This recalcitrance allows peat to persist in the (sub)tropics despite warm temperatures. Because we observed similar declines in carbohydrate content with depth in high-latitude peat, our data explain recent field-scale deep peat warming experiments in which catotelm (deeper) peat remained stable despite temperature increases up to 9 degrees C. We suggest that high-latitude deep peat reservoirs may be stabilized in the face of climate change by their ultimately lower carbohydrate and higher aromatic composition, similar to tropical peats.
Y1  - 2018
U6  - https://doi.org/10.1038/s41467-018-06050-2
SN  - 2041-1723
VL  - 9
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Graf, Lukas
A1  - Moreno-de-las-Heras, Mariano
A1  - Ruiz, Maurici
A1  - Calsamiglia, Aleix
A1  - García-Comendador, Julián
A1  - Fortesa, Josep
A1  - López-Tarazón, José A.
A1  - Estrany, Joan
T1  - Accuracy assessment of digital terrain model dataset sources for hydrogeomorphological modelling in small mediterranean catchments
JF  - Remote sensing
N2  - Digital terrain models (DTMs) are a fundamental source of information in Earth sciences. DTM-based studies, however, can contain remarkable biases if limitations and inaccuracies in these models are disregarded. In this work, four freely available datasets, including Shuttle Radar Topography Mission C-Band Synthetic Aperture Radar (SRTM C-SAR V3 DEM), Advanced Spaceborne Thermal Emission and Reflection Radiometer Global Digital Elevation Map (ASTER GDEM V2), and two nationwide airborne light detection and ranging (LiDAR)-derived DTMs (at 5-m and 1-m spatial resolution, respectively) were analysed in three geomorphologically contrasting, small (3–5 km2) catchments located in Mediterranean landscapes under intensive human influence (Mallorca Island, Spain). Vertical accuracy as well as the influence of each dataset’s characteristics on hydrological and geomorphological modelling applicability were assessed by using ground-truth data, classic geometric and morphometric parameters, and a recently proposed index of sediment connectivity. Overall vertical accuracy—expressed as the root mean squared error (RMSE) and normalised median deviation (NMAD)—revealed the highest accuracy for the 1-m (RMSE = 1.55 m; NMAD = 0.44 m) and 5-m LiDAR DTMs (RMSE = 1.73 m; NMAD = 0.84 m). Vertical accuracy of the SRTM data was lower (RMSE = 6.98 m; NMAD = 5.27 m), but considerably higher than for the ASTER data (RMSE = 16.10 m; NMAD = 11.23 m). All datasets were affected by systematic distortions. Propagation of these errors and coarse horizontal resolution caused negative impacts on flow routing, stream network, and catchment delineation, and to a lower extent, on the distribution of slope values. These limitations should be carefully considered when applying DTMs for catchment hydrogeomorphological modelling.
KW  - digital terrain models
KW  - DTM vertical accuracy
KW  - DTM comparison
KW  - hydrogeomorphological modelling
KW  - Mediterranean catchments
Y1  - 2018
U6  - https://doi.org/10.3390/rs10122014
SN  - 2072-4292
VL  - 10
IS  - 12
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Skinner, Christopher J.
A1  - Coulthard, Tom J.
A1  - Schwanghart, Wolfgang
A1  - Van De Wiel, Marco J.
A1  - Hancock, Greg
T1  - Global sensitivity analysis of parameter uncertainty in landscape evolution models
JF  - Geoscientific model development : an interactive open access journal of the European Geosciences Union
N2  - The evaluation and verification of landscape evolution models (LEMs) has long been limited by a lack of suitable observational data and statistical measures which can fully capture the complexity of landscape changes. This lack of data limits the use of objective function based evaluation prolific in other modelling fields, and restricts the application of sensitivity analyses in the models and the consequent assessment of model uncertainties. To overcome this deficiency, a novel model function approach has been developed, with each model function representing an aspect of model behaviour, which allows for the application of sensitivity analyses. The model function approach is used to assess the relative sensitivity of the CAESAR-Lisflood LEM to a set of model parameters by applying the Morris method sensitivity analysis for two contrasting catchments. The test revealed that the model was most sensitive to the choice of the sediment transport formula for both catchments, and that each parameter influenced model behaviours differently, with model functions relating to internal geomorphic changes responding in a different way to those relating to the sediment yields from the catchment outlet. The model functions proved useful for providing a way of evaluating the sensitivity of LEMs in the absence of data and methods for an objective function approach.
Y1  - 2018
U6  - https://doi.org/10.5194/gmd-11-4873-2018
SN  - 1991-959X
SN  - 1991-9603
VL  - 11
IS  - 12
SP  - 4873
EP  - 4888
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Marrucci, Monica
A1  - Zeilinger, Gerold
A1  - Ribolini, Adriano
A1  - Schwanghart, Wolfgang
T1  - Origin of Knickpoints in an Alpine Context Subject to Different Perturbing Factors, Stura Valley, Maritime Alps (North-Western Italy)
JF  - Geosciences
N2  - Natural catchments are likely to show the existence of knickpoints in their river networks. The origin and genesis of the knickpoints can be manifold, considering that the present morphology is the result of the interactions of different factors such as tectonic movements, quaternary glaciations, river captures, variable lithology, and base-level changes. We analyzed the longitudinal profiles of the river channels in the Stura di Demonte Valley (Maritime Alps) to identify the knickpoints of such an alpine setting and to characterize their origins. The distribution and the geometry of stream profiles were used to identify the possible causes of the changes in stream gradients and to define zones with genetically linked knickpoints. Knickpoints are key geomorphological features for reconstructing the evolution of fluvial dissected basins, when the different perturbing factors affecting the ideally graded fluvial system have been detected. This study shows that even in a regionally small area, perturbations of river profiles are caused by multiple factors. Thus, attributing (automatically)-extracted knickpoints solely to one factor, can potentially lead to incomplete interpretations of catchment evolution.
KW  - knickpoint
KW  - river longitudinal profile
KW  - Maritime Alps
Y1  - 2018
U6  - https://doi.org/10.3390/geosciences8120443
SN  - 2076-3263
VL  - 8
IS  - 12
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Bormann, Helge
A1  - de Brito, Mariana Madruga
A1  - Charchousi, Despoina
A1  - Chatzistratis, Dimitris
A1  - David, Amrei
A1  - Grosser, Paula Farina
A1  - Kebschull, Jenny
A1  - Konis, Alexandros
A1  - Koutalakis, Paschalis
A1  - Korali, Alkistis
A1  - Krauzig, Naomi
A1  - Meier, Jessica
A1  - Meliadou, Varvara
A1  - Meinhardt, Markus
A1  - Munnelly, Kieran
A1  - Stephan, Christiane
A1  - de Vos, Leon Frederik
A1  - Dietrich, Jörg
A1  - Tzoraki, Ourania
T1  - Impact of Hydrological Modellers’ Decisions and Attitude on the Performance of a Calibrated Conceptual Catchment Model
BT  - Results from a ‘Modelling Contest’
JF  - Hydrology
N2  - In this study, 17 hydrologists with different experience in hydrological modelling applied the same conceptual catchment model (HBV) to a Greek catchment, using identical data and model code. Calibration was performed manually. Subsequently, the modellers were asked for their experience, their calibration strategy, and whether they enjoyed the exercise. The exercise revealed that there is considerable modellers’ uncertainty even among the experienced modellers. It seemed to be equally important whether the modellers followed a good calibration strategy, and whether they enjoyed modelling. The exercise confirmed previous studies about the benefit of model ensembles: Different combinations of the simulation results (median, mean) outperformed the individual model simulations, while filtering the simulations even improved the quality of the model ensembles. Modellers’ experience, decisions, and attitude, therefore, have an impact on the hydrological model application and should be considered as part of hydrological modelling uncertainty.
Y1  - 2018
U6  - https://doi.org/10.3390/hydrology5040064
SN  - 2306-5338
VL  - 5
IS  - 4
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Puppe, Daniel
A1  - Wanner, Manfred
A1  - Sommer, Michael
T1  - Data on euglyphid testate amoeba densities, corresponding protozoic silicon pools, and selected soil parameters of initial and forested biogeosystems
JF  - Data in brief
N2  - The dataset in the present article provides information on protozoic silicon (Si) pools represented by euglyphid testate amoebae (TA) in soils of initial and forested biogeosystems. Protozoic Si pools were calculated from densities of euglyphid TA shells and corresponding Si contents. The article also includes data on potential annual biosilicification rates of euglyphid TA at the examined sites. Furthermore, data on selected soil parameters (e.g., readily-available Si, soil pH) and site characteristics (e.g., soil groups, climate data) can be found. The data might be interesting for researchers focusing on biological processes in Si cycling in general and euglyphid TA and corresponding protozoic Si pools in particular.
KW  - Silicon cycling
KW  - Biogenic silica
KW  - Terrestrial biogeosystems
KW  - Biosilicification
KW  - Euglyphida
Y1  - 2018
U6  - https://doi.org/10.1016/j.dib.2018.10.164
SN  - 2352-3409
VL  - 21
SP  - 1697
EP  - 1703
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Hellwig, Niels
A1  - Tatti, Dylan
A1  - Sartori, Giacomo
A1  - Anschlag, Kerstin
A1  - Graefe, Ulfert
A1  - Egli, Markus
A1  - Gobat, Jean-Michel
A1  - Broll, Gabriele
T1  - Modeling spatial patterns of humus forms in montane and subalpine forests
BT  - implications of local variability for upscaling
JF  - Sustainability
N2  - Humus forms are a distinctive morphological indicator of soil organic matter decomposition. The spatial distribution of humus forms depends on environmental factors such as topography, climate and vegetation. In montane and subalpine forests, environmental influences show a high spatial heterogeneity, which is reflected by a high spatial variability of humus forms. This study aims at examining spatial patterns of humus forms and their dependence on the spatial scale in a high mountain forest environment (Val di Sole/Val di Rabbi, Trentino, Italian Alps). On the basis of the distributions of environmental covariates across the study area, we described humus forms at the local scale (six sampling sites), slope scale (60 sampling sites) and landscape scale (30 additional sampling sites). The local variability of humus forms was analyzed with regard to the ground cover type. At the slope and landscape scale, spatial patterns of humus forms were modeled applying random forests and ordinary kriging of the model residuals. The results indicate that the occurrence of the humus form classes Mull, Mullmoder, Moder, Amphi and Eroded Moder generally depends on the topographical position. Local-scale patterns are mostly related to micro-topography (local accumulation and erosion sites) and ground cover, whereas slope-scale patterns are mainly connected with slope exposure and elevation. Patterns at the landscape scale show a rather irregular distribution, as spatial models at this scale do not account for local to slope-scale variations of humus forms. Moreover, models at the slope scale perform distinctly better than at the landscape scale. In conclusion, the results of this study highlight that landscape-scale predictions of humus forms should be accompanied by local- and slope-scale studies in order to enhance the general understanding of humus form patterns.
KW  - soil organic matter decomposition
KW  - spatial modeling
KW  - random forest
KW  - multi-scale analysis
KW  - forest soils
KW  - Italian Alps
Y1  - 2018
U6  - https://doi.org/10.3390/su11010048
SN  - 2071-1050
VL  - 11
IS  - 1
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Rusak, James A.
A1  - Tanentzap, Andrew J.
A1  - Klug, Jennifer L.
A1  - Rose, Kevin C.
A1  - Hendricks, Susan P.
A1  - Jennings, Eleanor
A1  - Laas, Alo
A1  - Pierson, Donald C.
A1  - Ryder, Elizabeth
A1  - Smyth, Robyn L.
A1  - White, D. S.
A1  - Winslow, Luke A.
A1  - Adrian, Rita
A1  - Arvola, Lauri
A1  - de Eyto, Elvira
A1  - Feuchtmayr, Heidrun
A1  - Honti, Mark
A1  - Istvanovics, Vera
A1  - Jones, Ian D.
A1  - McBride, Chris G.
A1  - Schmidt, Silke Regina
A1  - Seekell, David
A1  - Staehr, Peter A.
A1  - Guangwei, Zhu
T1  - Wind and trophic status explain within and among-lake variability of algal biomass
JF  - Limnology and oceanography letters / ASLO, Association for the Sciences of Limnology and Oceanography
N2  - Phytoplankton biomass and production regulates key aspects of freshwater ecosystems yet its variability and subsequent predictability is poorly understood. We estimated within-lake variation in biomass using high-frequency chlorophyll fluorescence data from 18 globally distributed lakes. We tested how variation in fluorescence at monthly, daily, and hourly scales was related to high-frequency variability of wind, water temperature, and radiation within lakes as well as productivity and physical attributes among lakes. Within lakes, monthly variation dominated, but combined daily and hourly variation were equivalent to that expressed monthly. Among lakes, biomass variability increased with trophic status while, within-lake biomass variation increased with increasing variability in wind speed. Our results highlight the benefits of high-frequency chlorophyll monitoring and suggest that predicted changes associated with climate, as well as ongoing cultural eutrophication, are likely to substantially increase the temporal variability of algal biomass and thus the predictability of the services it provides.
Y1  - 2018
U6  - https://doi.org/10.1002/lol2.10093
SN  - 2378-2242
VL  - 3
IS  - 6
SP  - 409
EP  - 418
PB  - Wiley
CY  - Hoboken
ER  -