@misc{McGrathSadlerFlemingetal., author = {McGrath, Gavan S. and Sadler, R. and Fleming, K. and Tregoning, P. and Hinz, Christoph and Veneklaas, Erik J.}, title = {Tropical cyclones and the ecohydrology of Australia's recent continental-scale drought}, issn = {0094-8276}, doi = {10.1029/2011GL050263}, language = {en} } @misc{DjajadiHinz, author = {Djajadi, Lynette K. Abbott and Hinz, Christoph}, title = {Synergistic impacts of clay and organic matter on structural and biological properties of a sandy soil}, series = {Geoderma}, volume = {183-184}, journal = {Geoderma}, issn = {0016-7061}, doi = {10.1016/j.geoderma.2012.03.012}, pages = {19 -- 24}, abstract = {Clay and organic matter, when incorporated together in a sandy soil, improved soil aggregation in association with both microbial activity and soil strength. Incorporation of clay into sandy agricultural soils in south-western Australia is a practice used to overcome water repellence, but the addition of high levels of clay can cause hardsetting. We investigated the extent to which addition of clay and organic matter would improve aggregate stability of a sandy agricultural soil from Meckering, Western Australia without negatively affecting soil strength. Four levels of subsoil clay and three levels of lucerne hay were compared in topsoil incubated for up to 42 days at two temperatures. Addition of both clay and lucerne hay together increased stable aggregation and the longer the period of incubation, the greater the macroaggregate stability. A decrease in soil respiration associated with increasing level of clay added may be related to protection of organic matter. Soil strength increased when the amount of clay alone was increased, but addition of both clay and organic matter decreased soil strength. Soil amelioration with 5\% clay and 0.8\% organic matter was most effective at improving the stability of macroaggregates without hardsetting. The non-linear relationships observed demonstrate the importance of understanding interactions between biological and physical components of soil fertility in relation to the sustainability of land management practices.}, language = {en} } @misc{GwenziVeneklaasBlebyetal., author = {Gwenzi, Willis and Veneklaas, Erik J. and Bleby, Timothy M. and Yunusa, Isa A.M. and Hinz, Christoph}, title = {Transpiration and plant water relations of evergreen woody vegetation on a recently constructed artificial ecosystem under seasonally dry conditions in Western Australia}, series = {Hydrological Processes}, volume = {26}, journal = {Hydrological Processes}, number = {21}, issn = {1099-1085}, doi = {10.1002/hyp.8330}, pages = {3281 -- 3292}, abstract = {Understanding transpiration and plant physiological responses to environmental conditions is crucial for the design and management of vegetated engineered covers. Engineered covers rely on sustained transpiration to reduce the risk of deep drainage into potentially hazardous wastes, thereby minimizing contamination of water resources. This study quantified temporal trends of plant water potential (ψp), stomatal conductance (gs), and transpiration in a 4-year-old evergreen woody vegetation growing on an artificial sandy substrate at a mine waste disposal facility. Transpiration averaged 0.7 mm day-1 in winter, when rainfall was frequent, but declined to 0.2 mm day-1 in the dry summer, when the plants were quite stressed. In winter, the mean ψp was -0.6 MPa at predawn and -1.5 MPa at midday, which were much higher than the corresponding summer values of -2.0 MPa and -4.8 MPa, respectively. The gs was also higher in winter (72.1-95.0 mmol m-2 s-1) than in summer (<30 mmol m-2 s-1), and negatively correlated with ψp (p < 0.05, r2 = 0.71-0.75), indicating strong stomatal control of transpiration in response to moisture stress. Total annual transpiration (147.2 mm) accounted for only 22\% of the annual rainfall (673 mm), compared with 77\% to 99\% for woody vegetation in Western Australia. The low annual transpiration was attributed to the collective effects of a sparse and young vegetation, low moisture retention of the sandy substrate, and a superficial root system constrained by high subsoil pH. Amending the substrate with fine-textured materials should improve water storage of the substrate and enhance canopy growth and deep rooting, while further reducing the risk of deep drainage during the early stages of vegetation establishment and in the long term. Overall, this study highlights the need to understand substrate properties, vegetation characteristics, and rainfall patterns when designing artificial ecosystems to achieve specific hydrological functions. Copyright © 2011 John Wiley \& Sons, Ltd.}, language = {en} } @misc{McGrathPaikHinz, author = {McGrath, Gavan S. and Paik, Kyungrock and Hinz, Christoph}, title = {Microtopography alters self-organized vegetation patterns in water-limited ecosystems}, series = {Journal of Geophysical Research}, volume = {117}, journal = {Journal of Geophysical Research}, number = {G03021}, issn = {0148-0227}, doi = {10.1029/2011JG001870}, pages = {1 -- 19}, abstract = {In terrestrial systems limited by water availability the spatial distribution of vegetation can self-organize into a mosaic of vegetated patches and bare soil. Spatially extensive competition for water and short-range facilitation underpin many models that describe the process of vegetation pattern formation. Earlier studies investigating this self-organized patchiness have largely considered smooth landscapes. However, topographic variations can significantly alter the redistribution of surface water flow and therefore the pattern-forming process. Here, we consider how microtopographic variations, at the scale of individual plants, alters self-organized vegetation patterns with the use of a simple ecohydrological model. We show that increasing microtopography can induce a change from banded vegetation, oriented across the slope, to irregular drainage patterns, oriented in the downslope direction. The mechanism responsible is shown to be a change in the spatial redistribution of infiltration around plants and plant patches. Only small increases in microtopography are required to cause banded systems with weak facilitation to change to downslope-oriented patterns. When non-periodic boundary conditions were considered, band orientation tended to become oblique to the topographic contour and in some circumstances their migration upslope ceased. These results suggest that diffusive sediment transport processes may be essential for the maintenance of regular periodic vegetation patterns, which implies that erosion may be critical for understanding the susceptibility of these ecosystems to catastrophic shifts.}, language = {en} } @misc{ColettiHinzVogwilletal., author = {Coletti, Janaine Z. and Hinz, Christoph and Vogwill, Ryan and Hipsey, Matthew R.}, title = {Hydrological controls on carbon metabolism in wetlands}, series = {Ecological Modelling}, volume = {249}, journal = {Ecological Modelling}, issn = {0304-3800}, doi = {10.1016/j.ecolmodel.2012.07.010}, pages = {3 -- 18}, abstract = {Governed by a series of non-linear feedback mechanisms among water, vegetation and decomposers, carbon storage within wetlands is important on a global scale. However, the effect that climatic fluctuations have on those mechanisms is not well documented. In this study, we introduce a mechanistic model connecting hydrology, vegetation and microbial biomass to investigate how changes in the climate signal propagate through wetland ecosystems, via vegetation and microbial dynamics, and attempt to quantify how net rates of wetland carbon metabolism change in response to a changing climate. Our particular focus is the dryland-wetland systems found in south-west Western Australia (SWWA), as they are expected to be sensitive to projected climatic changes due to their close linkage to the seasonal water delivery pattern. The model simulations investigate wetland carbon retention under different hydro-climatological conditions ranging across a regional gradient in the dryness index. The results indicate that short term and long term vegetation responses may be counter-intuitive due to adaptability in the water uptake strategy of the vegetation community partially decoupling biomass from water availability. Furthermore, changes in water delivery are not a good indicator for overall changes in wetland metabolism, defined as the net rate of carbon assimilation, due to the dominance of the soil carbon storages and their sensitivity to heightened bacterial metabolism rates with increasing temperatures. The results highlight that an optimum combination of water supply and vegetation leads to a higher percentage of carbon being stored in soils, therefore increasing the resistance of the carbon storage to changes in precipitation. The model presented here provides a first step to explain how changing patterns of rainfall, temperature and evapotranspiration can change carbon cycling characteristics and the carbon retention efficiency of dryland-wetlands.}, language = {en} } @misc{McGrathNieDyskinetal., author = {McGrath, Gavan S. and Nie, Zhengyao and Dyskin, Arcady and Byrd, Tia and Jenner, Rowan and Holbeche, Georgina and Hinz, Christoph}, title = {In situ fragmentation and rock particle sorting on arid hills}, series = {Journal of Geophysical Research: Earth Surface}, volume = {118}, journal = {Journal of Geophysical Research: Earth Surface}, number = {1}, issn = {2169-9011}, doi = {10.1029/2012JF002402}, pages = {17 -- 28}, abstract = {Transport processes are often proposed to explain the sorting of rock particles on arid hillslopes, where mean rock particle size often decreases in the downslope direction. Here we show that in situ fragmentation of rock particles can also produce similar patterns. A total of 93,414 rock particles were digitized from 880 photographs of the surface of three mesa hills in the Great Sandy Desert, Australia. Rock particles were characterized by the projected Feret's diameter and circularity. Distance from the duricrust cap was found to be a more robust explanatory variable for diameter than the local hillslope gradient. Mean diameter decreased exponentially downslope, while the fractional area covered by rock particles decreased linearly. Rock particle diameters were distributed lognormally, with both the location and scale parameters decreasing approximately linearly downslope. Rock particle circularity distributions showed little change; only a slight shift in the mode to more circular particles was noted to occur downslope. A dynamic fragmentation model was used to assess whether in situ weathering alone could reproduce the observed downslope fining of diameters. Modeled and observed size distributions agreed well and both displayed a preferential loss of relatively large rock particles and an apparent approach to a terminal size distribution of the rocks downslope. We show this is consistent with a size effect in material strength, where large rocks are more susceptible to fatigue failure under stress than smaller rocks. In situ fragmentation therefore produces qualitatively similar patterns to those that would be expected to arise from selective transport.}, language = {en} } @misc{GwenziHinzBlebyetal., author = {Gwenzi, Willis and Hinz, Christoph and Bleby, Timothy M. and Veneklaas, Erik J.}, title = {Transpiration and water relations of evergreen shrub species on an artificial landform for mine waste storage versus an adjacent natural site in semi-arid Western Australia}, series = {Ecohydrology}, volume = {7}, journal = {Ecohydrology}, number = {3}, issn = {1936-0592}, doi = {10.1002/eco.1422}, pages = {965 -- 981}, abstract = {In water-limited environments, transpiration may minimize deep drainage on engi-neered covers used for hazardous waste disposal. However, comparative studies investigating plant ecophysiology and water use on engineered covers and natural sites are limited. Water use patterns and plant-water relations of evergreen shrubs were monitored in semi-arid Western Australia to (1) investigate the response of plant-water relations and shrub transpiration to soil moisture changes and (2) quan-tify stand transpiration and its contribution to the water balance. The shrubs showed conservative (<20 cm hr-1) but persistent transpiration. Differential response to rainfall pulses was evident among species; sap velocity for Acacia bivenosa and Acacia inaequilatera increased by 20-103\% (p < 0•05) after rainfall events ex-ceeding 15 mm but declined rapidly to pre-storm levels. On the contrary, sap veloc-ity for Acacia pruinocarpa increased by 61\% after large pulse (83 and 127 mm) as-sociated with cyclonic activity and remained high (10-15 cm hr-1) thereafter. These transpiration patterns suggested contrasting rooting patterns among the spe-cies. Sap velocity was low (<20 mm hr-1) for all species, even when moisture was readily available. Annual shrub transpiration was 65 (engineered cover) and 81 mm (natural shrubland), accounting for 16 and 20\% of annual rainfall (395 mm). Stand characteristics, plant ecophysiology and shrub transpiration were comparable for both sites, demonstrating the importance of using topsoil as a growth medium and seedbank in revegetation. Overall, the study provided insights on ecophysiological behaviour of artificial landforms, and the first empirical evidence suggesting rapid and successful restoration of mined lands can be achieved under semi-arid conditions.}, language = {en} } @misc{SalmonRateRengeletal., author = {Salmon, S. Ursula and Rate, Andrew W. and Rengel, Zed and Appleyard, Steven and Prommer, Henning and Hinz, Christoph}, title = {Reactive transport controls on sandy acid sulfate soils and impacts on shallow groundwater quality}, series = {Water Resources Research}, volume = {50}, journal = {Water Resources Research}, number = {6}, issn = {1944-7973}, doi = {10.1002/2013WR014404}, pages = {4924 -- 4952}, abstract = {Disturbance or drainage of potential acid sulfate soils (PASS) can result in the release of acidity and degradation of infrastructure, water resources, and the environment. Soil processes affecting shallow groundwater quality have been investigated using a numerical code that integrates (bio)geochemical processes with water, solute, and gas transport. The patterns of severe and persistent acidification (pH < 4) in the sandy, carbonate-depleted podzols of a coastal plain could be reproduced without calibration, based on oxidation of microcrystalline pyrite after groundwater level decrease and/or residual groundwater acidity, due to slow vertical solute transport rates. The rate of acidification was limited by gas phase diffusion of oxygen and hence was sensitive to soil water retention properties and in some cases also to oxygen con-sumption by organic matter mineralization. Despite diffusion limitation, the rate of oxidation in sandy soils was rapid once pyrite-bearing horizons were exposed, even to a depth of 7.5 m. Groundwater level movement was thus identified as an important control on acidification, as well as the initial pyrite content. Increase in the rate of Fe(II) oxidation lead to slightly lower pH and greater accumulation of Fe(III) phases, but had little effect on the overall amount of pyrite oxidized. Aluminosilicate (kaolinite) dissolution had a small pH-buffering effect but lead to the release of Al and associated acidity. Simulated dewatering scenarios highlighted the potential of the model for risk assessment of (bio)geochemical impacts on soil and groundwater over a range of temporal and spatial scales.}, language = {en} } @inproceedings{Hinz, author = {Hinz, Christoph}, title = {Competing feedbacks as a driver for ecosystems development and restoration success}, series = {5th World Conference on Ecological Restoration, Book of Abstracts, October 6-11, 2013, Madison, Wisconsin, USA}, booktitle = {5th World Conference on Ecological Restoration, Book of Abstracts, October 6-11, 2013, Madison, Wisconsin, USA}, publisher = {Society for Ecological Restoration}, address = {Washington, DC}, pages = {86 -- 87}, language = {en} } @inproceedings{MaurerSchappBuechneretal., author = {Maurer, Thomas and Schapp, Andrea and B{\"u}chner, Steffen and Menzel, Hannes and Hinz, Christoph}, title = {Measurement of rainfall distribution on a small catchment for the evaluation of canopy interception effects}, series = {European Geosciences Union, General Assembly 2014, Vienna, Austria, 27 April - 02 May 2014}, booktitle = {European Geosciences Union, General Assembly 2014, Vienna, Austria, 27 April - 02 May 2014}, publisher = {European Geophysical Society}, address = {Katlenburg-Lindau}, abstract = {Variability of rainfall and throughfall is an essential characteristic of the water balance at spatial scales ranging from meters to hundreds of meters or even kilometers. The amount of throughfall is governed by the characteristics of the vegetation canopy and the involved interception and stemflow effects. In initial, developing ecosystems, distinct patterns of the growing vegetation (e.g. patchiness) supposedly govern the spatial distribution of water in the system, thereby initiating and supporting hydro-ecological feedback processes. Questions are i) is the spatial variability of vegetation relevant for the system as a whole, and ii) how does the distribution of the effective precipitation (i.e. the infiltration) change over time in dependency of vegetation succession? We present the first results of a spatially distributed measurement approach of surface-near precipitation on the constructed catchment "H{\"u}hnerwasser" ("Chicken Creek"). The 6-ha site is located in the recultivation area of the lignite open-cast mine "Welzow-S{\"u}d" in Lower Lusatia, Brandenburg, Germany. Here, the free development of an initial ecosystem is investigated since September 2005. After eight years of succession, the spatial distribution of plant species is highly heterogeneous, and gains increasing influence on throughfall patterns, thus impacting the distribution of soil humidity and possibly even surface runoff. For spatially distributed precipitation measurement, 47 tipping bucket rain gauges were installed in heights of 0.5 m and 1.0 m along two transects on the catchment. Rain gauge data were collected by a wireless sensor node network provided by the Sens4U joint research project. The transects run NW-SE and NE-SW and cover the range of plant communities presently existing in the ecosystem: locust copses, dense sallow thorn bushes and reeds, base herbaceous and medium-rise small-reed vegetation, and open areas covered by moss and lichens. The raw measurement data were temporally aggregated using a VBA script in order to characterize interception for various types of precipitation events on different time scales. First results from the measurement period 17th July - 3rd September 2013 widely exhibit a good accordance with reference data from on-site weather stations for sites on open ground, while canopy sites show more heterogeneous values, either due to interception or due to canopy collection effects. However, it was found that the explanation of the differences between comparable sites requires an additional inclusion of other relevant parameters, e.g. wind speed and direction, screening effects, and specific canopy characteristics. Moreover, extreme precipitation events sometimes seemed to lead to incorrect measurements either by the sensor and / or node, which required supplementary quality controls of equipment and data. Results from future long-term measurements on the "H{\"u}hnerwasser" catchment will be used to identify possible plant-soil feedback mechanisms and to parameterize models that simulate the behavior of initial eco-hydrological systems}, language = {de} } @inproceedings{FrechenHinzMcGrath, author = {Frechen, Tobias Nanu and Hinz, Christoph and McGrath, Gavan S.}, title = {Relating biomass and vegetation structure in water limited ecosystems using a celluar automata based model}, series = {European Geosciences Union, General Assembly 2015, Vienna, Austria, 13 April - 17 May 2015}, booktitle = {European Geosciences Union, General Assembly 2015, Vienna, Austria, 13 April - 17 May 2015}, publisher = {European Geophysical Society}, address = {Katlenburg-Lindau}, language = {en} } @inproceedings{JozefikFrechenHinzetal., author = {Jozefik, Zoltan and Frechen, Tobias Nanu and Hinz, Christoph and Schmidt, Heiko}, title = {A cellular automata approach for modeling surface water runoff}, series = {European Geosciences Union, General Assembly 2015, Vienna, Austria, 13 April - 17 May 2015}, booktitle = {European Geosciences Union, General Assembly 2015, Vienna, Austria, 13 April - 17 May 2015}, publisher = {European Geophysical Society}, address = {Katlenburg-Lindau}, language = {en} } @misc{PohleKochGaedekeetal., author = {Pohle, Ina and Koch, Hagen and G{\"a}deke, Anne and Hinz, Christoph and Gr{\"u}newald, Uwe}, title = {Does water management reduce the uncertainty of projected climate change impacts on river discharge?}, publisher = {AGU Fall Meeting}, address = {San Francisco}, language = {en} } @misc{MuellerSchalkHildebrandtetal., author = {M{\"u}ller, Eva Nora and Schalk, Loes von and Hildebrandt, Anke and Hinz, Christoph}, title = {Wasserforschung vor neuen Herausforderungen: {\"O}kohydrologisches Monitoring und Verfahrensentwicklung von innovativen Feldmethoden an terrestrischen und aquatischen Schnittstellen : Positionspapier des Open Space Workshops der 6. Water Research Horizon Conference, 17.-18. Juni 2015, Berlin}, series = {Hydrologie und Wasserbewirtschaftung}, volume = {59}, journal = {Hydrologie und Wasserbewirtschaftung}, number = {6}, issn = {1439-1783}, pages = {431 -- 432}, language = {de} } @inproceedings{BrueckPohleKeuleretal., author = {Br{\"u}ck, Yasemine and Pohle, Ina and Keuler, Klaus and Schaller, Eberhard and Hinz, Christoph}, title = {Do mining lakes in the Lusatian Lignite mining region (Eastern Germany) affect regional precipitation patterns?}, series = {European Geosciences Union, General Assembly 2016, Vienna, Austria}, booktitle = {European Geosciences Union, General Assembly 2016, Vienna, Austria}, publisher = {European Geophysical Society}, address = {Katlenburg-Lindau}, abstract = {Due to the flooding of former open-pit mines, Europe's largest artificial lake district is created in Eastern Germany. Between 1990 and 2006 more than 80 km² of new lakes have already been formed. These large-scale land cover changes may impact regional meteorological characteristics, therefore it is of interest, whether effects of the mining lakes can already be observed. We especially focus on whether the evaporation from the mining pit lakes leads to a higher precipitation on their lee side. To detect changes in the precipitation patterns, we analysed daily precipitation data (1980-2014) of 25 stations in an area of 10 000 km² widely around the lake district. Under the assumption that the influences of the lakes should be detectable either directly as trends in the observed data or as a deviation from a general measure for precipitation we combined statistical tests and principal component analysis (PCA). We applied pre-whitening Mann-Kendall tests to detect precipitation trends and Mann-Whitney tests to detect differences between split samples (before and after the flooding of most of the lakes). The PCA was applied based on the correlation matrix of daily precipitation at the different stations. As the daily precipitation can sufficiently be explained by the first five principal components, the recombination of these five principal components was used as a general measure of precipitation in the region. By regression trees (random forests) a relation between the eigenvectors of the first five principal components and physiogeographic characteristics of the stations (e.g. altitude) was shown. Both the observed data and the deviations between the measurements and the recombination of the first five principal components showed divergent trends with high spatial variability and also interannual variability, but a pattern consistent with the lee side of the lake could not be detected. Therefore, it has been demonstrated that the emerging lakes had no influence on the daily precipitation at the stations considered in this study. This may be explained by the coarse spatial and also temporal resolution of precipitation measurements. Still, the approach presented here can be applied to (i) detect changes in the spatial pattern of climate variables by a combination of statistical tests and PCA and (ii) to analyse the relationships between such changes and physiogeographic characteristics by regression trees.}, language = {en} } @inproceedings{HinzSchuembergKubitzetal., author = {Hinz, Christoph and Sch{\"u}mberg, Sabine and Kubitz, Anita and Frank, Franzi and Cheng, Zhang and Frechen, Tobias Nanu and Pohle, Ina}, title = {Dynamic effects of wet-dry cycles and crust formation on the saturated hydraulic conductivity of surface soils in the constructed H{\"u}hnerwasser ("Chicken Creek") catchment}, series = {European Geosciences Union, General Assembly 2016, Vienna, Austria}, booktitle = {European Geosciences Union, General Assembly 2016, Vienna, Austria}, publisher = {European Geophysical Society}, address = {Katlenburg-Lindau}, abstract = {Highly disturbed soils and substrates used in land rehabilitation undergo rapid changes after the first wetting events which in turn can lead to ecosystem degradation. Such changes were detected during the early development of the constructed H{\"u}hnerwasser ("Chicken Creek") catchment in Lusatia, Germany. Surface substrates consisting of quaternary sandy sediments formed surface seals during the first rainfall events leading to reduced infiltration and substantially increased surface runoff. Subsequently biological soil crusts formed and stabilised the surface. The aim of this study is to investigate the factors that cause the hydraulic conductivity to decrease using undisturbed and disturbed soil samples. Based on the hypothesis that physical and biological crusts lower the hydraulic conductivity, the first set of experiments with undisturbed soil cores from the H{\"u}hnerwasser catchment were carried out to measure the saturated hydraulic conductivity using the constant head method. Measurements were done with intact cores and repeated after the surface crust was removed. As the quaternary glacial sediments tend to display hard setting behaviour, we further hypothesised that the mobilisation of fine particles within the cores lead to pore clogging and that wet-dry cycles will therefore decrease hydraulic conductivity. A second set of experiments using the same methodology consisted of five repeated measurements of hydraulic conductivity after each drying cycle. These measurements were done with undisturbed core samples as well as repacked cores in order to assess how dry packing affects the dynamics of the hydraulic conductivity somewhat similar to the situation during the first wetting after completion of the catchment construction. For all experiments, the temporal evolution of hydraulic conductivity was measured and the turbidity of the effluent was recorded. The results clearly demonstrated that the substrate is highly unstable. The first set of experiments showed that the removal of the crust lead generally to a decrease in hydraulic conductivity. The process of crust removal represented a severe disturbance of the surface soil which to our understanding causes particle mobilisation and subsequent pore clogging. The first hypothesis could neither be rejected nor accepted. The second set of experiments showed that the hydraulic conductivity significantly dropped in particular after the first drying event. This was observed for both undisturbed and repacked samples. The following drying cycles further decreased the hydraulic conductivity in the repacked samples. The decrease in hydraulic conductivity was positively correlated to turbidity values in the effluent of the samples, indicating particle mobilisation in all samples. The results imply that hydraulic properties in such substrates undergo rapid changes that depend on the temporal dynamics of atmospheric drivers, precipitation and evaporative demand, controlling the degree of wetness and the rate and degree of drying during the very early stage after placement. Associated with the dynamics of the atmospheric drivers are the biological changes due to the formation of biological soil crusts and the establishment of vegetation, both of them contributing to the stabilisation of hydraulic properties.}, language = {en} } @inproceedings{ZaplataVestePohleetal., author = {Zaplata, Markus K. and Veste, Maik and Pohle, Ina and Sch{\"u}mberg, Sabine and Abreu Schonert, Iballa and Hinz, Christoph}, title = {Experimental investigation of the early interaction between cyanobacterial soil crusts and vascular plants}, series = {European Geosciences Union, General Assembly 2016, Vienna, Austria}, booktitle = {European Geosciences Union, General Assembly 2016, Vienna, Austria}, publisher = {European Geophysical Society}, address = {Katlenburg-Lindau}, abstract = {While there are hints that biological soil crusts (BSCs) can constitute physical barriers for the emergence of vascular plants, a conceptual approach for the quantitative evaluation of these effects is still missing. Here we present an experimental design to test the emergence of seedlings in situ with (i) capping natural intact, (ii) destroyed and (iii) removed BSC. The selected field site is directly adjacent to the constructed H{\"u}hnerwasser catchment (Lusatia, Germany). This site exists since the end of 2008 and consists of loamy sand. Serving as proxy for seedling thrust, we inserted pre-germinated seeds of three confamiliar plant species with different seed masses (members of the Fabaceae family: Lotus corniculatus L., Ornithopus sativus Brot., and Glycine max (L.) Merr.). In each treatment as well as in the control group planting depths were 10 mm. We took care that experimental plots had identical crust thickness, slightly less than 4 mm, serving as proxy for mechanical resistance. A plot became established as follows: Firstly, the pristine crusted surface was vertically cut. To the windward side the BSC remained intact (i: "with BSC" stripe). To the downwind side soil material was temporarily excavated for laterally inserting the seeds beneath the surface of the first stripe. Then at the thereby disturbed second stripe pulverised BSC material became filled as a top layer (ii: "BSC mix" stripe). From the next stripe the BSC was removed (iii : "no BSC" stripe). Thus each plot had each experimental group in spatial contiguity (within 50 cm * 50 cm). The overall 50 plots were distributed across an area of 40 m * 12 m. When individuals of a species either emerged at all stripes, "XXX", or at no stripe of a plot, "- - -", there was no reason to suppose any effect of a crust. The "-XX" emergence pattern (depicting the appearance of seedlings in both stripes possessing manipulated surfaces) points towards hindrance more clearly than "-X-" or "- - X". Altogether eight possible combinations exist. Combinatorial analysis turned out that seedling emergence had been notably impeded for light-weighted seeds but little for heavy seeds. Repeated recordings enable to account for adaptable emergence of seedlings according to varying crust conditions - in spatial as well as temporal terms. The proposed experimental procedure hence is highly recommended as a viable instrument to further investigate filter and facilitation processes between BSCs and vascular plants.}, language = {en} } @inproceedings{MaurerTrujilloSiliezarOeseretal., author = {Maurer, Thomas and Trujillo Sili{\´e}zar, Carlos Gustavos and Oeser, Anne and Pohle, Ina and Hinz, Christoph}, title = {A methodology for investigating interdependencies between measured throughfall, meteorological variables and canopy structure on a small catchment}, series = {European Geosciences Union, General Assembly 2016, Vienna, Austria}, booktitle = {European Geosciences Union, General Assembly 2016, Vienna, Austria}, publisher = {European Geophysical Society}, address = {Katlenburg-Lindau}, abstract = {In evolving initial landscapes, vegetation development depends on a variety of feedback effects. One of the less understood feedback loops is the interaction between throughfall and plant canopy development. The amount of throughfall is governed by the characteristics of the vegetation canopy, whereas vegetation pattern evolution may in turn depend on the spatio-temporal distribution of throughfall. Meteorological factors that may influence throughfall, while at the same time interacting with the canopy, are e.g. wind speed, wind direction and rainfall intensity. Our objective is to investigate how throughfall, vegetation canopy and meteorological variables interact in an exemplary eco-hydrological system in its initial development phase, in which the canopy is very heterogeneous and rapidly changing. For that purpose, we developed a methodological approach combining field methods, raster image analysis and multivariate statistics. The research area for this study is the H{\"u}hnerwasser ('Chicken Creek') catchment in Lower Lusatia, Brandenburg, Germany, where after eight years of succession, the spatial distribution of plant species is highly heterogeneous, leading to increasingly differentiated throughfall patterns. The constructed 6-ha catchment offers ideal conditions for our study due to the rapidly changing vegetation structure and the availability of complementary monitoring data.Throughfall data were obtained by 50 tipping bucket rain gauges arranged in two transects and connected via a wireless sensor network that cover the predominant vegetation types on the catchment (locust copses, dense sallow thorn bushes and reeds, base herbaceous and medium-rise small-reed vegetation, and open areas covered by moss and lichens). The spatial configuration of the vegetation canopy for each measurement site was described via digital image analysis of hemispheric photographs of the canopy using the ArcGIS Spatial Analyst, GapLight and ImageJ software. Meteorological data from two on-site weather stations (wind direction, wind speed, air temperature, air humidity, insolation, soil temperature, precipitation) were provided by the 'Research Platform Chicken Creek'. Data were combined and multivariate statistical analysis (PCA, cluster analysis, regression trees) were conducted using the R-software to i) obtain statistical indices describing the relevant characteristics of the data and ii) to identify the determining factors for throughfall intensity. The methodology is currently tested and results will be presented. Preliminary evaluation of the image analysis approach showed only marginal, systematic deviation of results for the different software tools applied, which makes the developed workflow a viable tool for canopy characterization. Results from this study will have a broad spectrum of possible applications, for instance the development / calibration of rainfall interception models, the incorporation into eco-hydrological models, or to test the fault tolerance of wireless rainfall sensor networks.}, language = {en} } @inproceedings{BrueckSchulteOverbergPohleetal., author = {Br{\"u}ck, Yasemine and Schulte-Overberg, Philipp and Pohle, Ina and Hinz, Christoph}, title = {NDVI (Normalized Difference Vegetation Index) signatures of transient ecohydrological systems: The case of post-mining landscapes}, series = {European Geosciences Union, General Assembly 2017, Vienna, Austria}, booktitle = {European Geosciences Union, General Assembly 2017, Vienna, Austria}, publisher = {European Geophysical Society}, address = {Katlenburg-Lindau}, abstract = {Assessing ecohydrological systems that undergo state transitions due to environmental change is becoming increasingly important. One system that can be used to study severe disturbances are post-mining landscapes as they usually are associated with complete removal of vegetation and afterwards subsequent ecosystem restoration or spontaneous rehabilitation in line with natural succession. Within this context it is of interest, whether and how (fast) the land cover in these areas returns to conditions comparable to those in the undisturbed surrounding or those prior mining. Many aspects of mine site rehabilitation depend on climatic, geomorphic and ecological settings, which determine at which rate vegetation may be reestablished. In order to identify general patterns of vegetation establishment, we propose to use NDVI (Normalized Difference Vegetation Index) time series for mine affected land to estimate rate of recovery across climate regions and ecoregions. In this study we analysed the MODIS Terra Satellite 8 day-composite NDVI for areas influenced by surface mining in different climates from 2001 to 2015. The locations have been chosen based on their extent and the data availability of mining and rehabilitation activities. We selected coal extraction as a case study as strip mining generates well-defined chronosequences of disturbance. The selected mining areas are located in equatorial, arid, warm temperate or snow climates with different precipitation and temperature conditions according to the K{\"o}ppen-Geiger classification. We analysed the NDVI time series regarding significant characteristics of the re-vegetation phase. We applied hierarchical cluster analysis to capture the spatial heterogeneity between different pixels (ca. 250 * 250 m2 each) in and around each open cast mine. We disentangled seasonality, trend and residual components in the NDVI time series by Seasonal and Trend decomposition using LOESS. As expected the time of the removal of vegetation can be clearly identified from the NDVI time series and provides the starting point of disturbance. The cluster analysis allowed us to distinguish between the non-mining land, the mine and the restored land of different ages. Based on these clusters, the time series decomposition revealed the dominance of the trend of increasing NDVI in areas undergoing the restoration process as well as the prevailing seasonality of the oldest restored sites. The determined phase of a dominant trend component, lasting until the NDVI is in the range of the surrounding landscape or the pre-mining conditions, is in the scale of a decade. The impacts of different hydroclimatic regimes and different rehabilitation strategies on long term NDVI development are currently being investigated. Furthermore, coherence analysis will be applied to quantify short term influences of hydrometeorological variables on vegetation development.}, language = {en} } @inproceedings{CaviedesVoulliemeJozefikHinz, author = {Caviedes-Voulli{\`e}me, Daniel and Jozefik, Zoltan and Hinz, Christoph}, title = {Towards a physically-based multi-scale ecohydrological simulator for semi-arid regions}, series = {European Geosciences Union General Assembly 2017 Vienna, Austria, 23-28 April 2017}, booktitle = {European Geosciences Union General Assembly 2017 Vienna, Austria, 23-28 April 2017}, publisher = {European Geophysical Society}, address = {Katlenburg-Lindau}, abstract = {The use of numerical models as tools for describing and understanding complex ecohydrological systems has enabled to test hypothesis and propose fundamental, process-based explanations of the system system behaviour as a whole as well as its internal dynamics. Reaction-diffusion equations have been used to describe and generate organized pattern such as bands, spots, and labyrinths using simple feedback mechanisms and boundary conditions. Alternatively, pattern-matching cellular automaton models have been used to generate vegetation self-organization in arid and semi-arid regions also using simple description of surface hydrological processes. A key question is: How much physical realism is needed in order to adequately capture the pattern formation processes in semi-arid regions while reliably representing the water balance dynamics at the relevant time scales? In fact, redistribution of water by surface runoff at the hillslope scale occurs at temporal resolution of minutes while the vegetation development requires much lower temporal resolution and longer times spans. This generates a fundamental spatio-temporal multi-scale problem to be solved, for which high resolution rainfall and surface topography are required. Accordingly, the objective of this contribution is to provide proof-of-concept that governing processes can be described numerically at those multiple scales. The requirements for a simulating ecohydrological processes and pattern formation with increased physical realism are, amongst others: i. high resolution rainfall that adequately captures the triggers of growth as vegetation dynamics of arid regions respond as pulsed systems. ii. complex, natural topography in order to accurately model drainage patterns, as surface water redistribution is highly sensitive to topographic features. iii. microtopography and hydraulic roughness, as small scale variations do impact on large scale hillslope behaviour iv. moisture dependent infiltration as temporal dynamics of infiltration affects water storage under vegetation and in bare soil Despite the volume of research in this field, fundamental limitations still exist in the models regarding the aforementioned issues. Topography and hydrodynamics have been strongly simplified. Infiltration has been modelled as dependent on depth but independent of soil moisture. Temporal rainfall variability has only been addressed for seasonal rain. Spatial heterogenity of the topography as well as roughness and infiltration properties, has not been fully and explicitly represented. We hypothesize that physical processes must be robustly modelled and the drivers of complexity must be present with as much resolution as possible in order to provide the necessary realism to improve transient simulations, perhaps leading the way to virtual laboratories and, arguably, predictive tools. This work provides a first approach into a model with explicit hydrological processes represented by physicallybased hydrodynamic models, coupled with well-accepted vegetation models. The model aims to enable new possibilities relating to spatiotemporal variability, arbitrary topography and representation of spatial heterogeneity, including sub-daily (in fact, arbitrary) temporal variability of rain as the main forcing of the model, explicit representation of infiltration processes, and various feedback mechanisms between the hydrodynamics and the vegetation. Preliminary testing strongly suggests that the model is viable, has the potential of producing new information of internal dynamics of the system, and allows to successfully aggregate many of the sources of complexity. Initial benchmarking of the model also reveals strengths to be exploited, thus providing an interesting research outlook, as well as weaknesses to be addressed in the immediate future.}, language = {en} }