@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} }