TY - JOUR A1 - Haßler, Sibylle Kathrin A1 - Lark, R. M. A1 - Zimmermann, Beate A1 - Elsenbeer, Helmut T1 - Which sampling design to monitor saturated hydraulic conductivity? JF - European journal of soil science N2 - Soil in a changing world is subject to both anthropogenic and environmental stresses. Soil monitoring is essential to assess the magnitude of changes in soil variables and how they affect ecosystem processes and human livelihoods. However, we cannot always be sure which sampling design is best for a given monitoring task. We employed a rotational stratified simple random sampling (rotStRS) for the estimation of temporal changes in the spatial mean of saturated hydraulic conductivity (K-s) at three sites in central Panama in 2009, 2010 and 2011. To assess this design's efficiency we compared the resulting estimates of the spatial mean and variance for 2009 with those gained from stratified simple random sampling (StRS), which was effectively the data obtained on the first sampling time, and with an equivalent unexecuted simple random sampling (SRS). The poor performance of geometrical stratification and the weak predictive relationship between measurements of successive years yielded no advantage of sampling designs more complex than SRS. The failure of stratification may be attributed to the small large-scale variability of K-s. Revisiting previously sampled locations was not beneficial because of the large small-scale variability in combination with destructive sampling, resulting in poor consistency between revisited samples. We conclude that for our K-s monitoring scheme, repeated SRS is equally effective as rotStRS. Some problems of small-scale variability might be overcome by collecting several samples at close range to reduce the effect of small-scale variation. Finally, we give recommendations on the key factors to consider when deciding whether to use stratification and rotation in a soil monitoring scheme. Y1 - 2014 U6 - https://doi.org/10.1111/ejss.12174 SN - 1351-0754 SN - 1365-2389 VL - 65 IS - 6 SP - 792 EP - 802 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Neill, Christopher A1 - Coe, Michael T. A1 - Riskin, Shelby H. A1 - Krusche, Alex V. A1 - Elsenbeer, Helmut A1 - Macedo, Marcia N. A1 - McHorney, Richard A1 - Lefebvre, Paul A1 - Davidson, Eric A. A1 - Scheffler, Raphael A1 - Figueira, Adelaine Michela e Silva A1 - Porder, Stephen A1 - Deegan, Linda A. T1 - Watershed responses to Amazon soya bean cropland expansion and intensification JF - Philosophical transactions of the Royal Society of London : B, Biological sciences N2 - The expansion and intensification of soya bean agriculture in southeastern Amazonia can alter watershed hydrology and biogeochemistry by changing the land cover, water balance and nutrient inputs. Several new insights on the responses of watershed hydrology and biogeochemistry to deforestation in Mato Grosso have emerged from recent intensive field campaigns in this region. Because of reduced evapotranspiration, total water export increases threefold to fourfold in soya bean watersheds compared with forest. However, the deep and highly permeable soils on the broad plateaus on which much of the soya bean cultivation has expanded buffer small soya bean watersheds against increased stormflows. Concentrations of nitrate and phosphate do not differ between forest or soya bean watersheds because fixation of phosphorus fertilizer by iron and aluminium oxides and anion exchange of nitrate in deep soils restrict nutrient movement. Despite resistance to biogeochemical change, streams in soya bean watersheds have higher temperatures caused by impoundments and reduction of bordering riparian forest. In larger rivers, increased water flow, current velocities and sediment flux following deforestation can reshape stream morphology, suggesting that cumulative impacts of deforestation in small watersheds will occur at larger scales. KW - soya beans KW - watersheds KW - nitrogen KW - phosphorus KW - soil Y1 - 2013 U6 - https://doi.org/10.1098/rstb.2012.0425 SN - 0962-8436 SN - 1471-2970 VL - 368 IS - 1619 PB - Royal Society CY - London ER - TY - JOUR A1 - Zimmermann, Alexander A1 - Schinn, Dustin S. A1 - Francke, Till A1 - Elsenbeer, Helmut A1 - Zimmermann, Beate T1 - Uncovering patterns of near-surface saturated hydraulic conductivity in an overland flow-controlled landscape JF - Geoderma : an international journal of soil science N2 - Saturated hydraulic conductivity (K-s) is an important soil characteristic affecting soil water storage, runoff generation and erosion processes. In some areas where high-intensity rainfall coincides with low K-s values at shallow soil depths, frequent overland flow entails dense drainage networks. Consequently, linear structures such as flowlines alternate with inter-flowline areas. So far, investigations of the spatial variability of K-s mainly relied on isotropic covariance models which are unsuitable to reveal patterns resulting from linear structures. In the present study, we applied two sampling approaches so as to adequately characterize K-s spatial variability in a tropical forest catchment that features a high density of flowlines: A classical nested sampling survey and a purposive sampling strategy adapted to the presence of flowlines. The nested sampling approach revealed the dominance of small-scale variability, which is in line with previous findings. Our purposive sampling, however, detected a strong spatial gradient: surface K-s increased substantially as a function of distance to flowline; 10 m off flowlines, values were similar to the spatial mean of K-s. This deterministic trend can be included as a fixed effect in a linear mixed modeling framework to obtain realistic spatial fields of K-s. In a next step we used probability maps based on those fields and prevailing rainfall intensities to assess the hydrological relevance of the detected pattern. This approach suggests a particularly good agreement between the probability statements of K-s exceedance and observed overland flow occurrence during wet stages of the rainy season. KW - Soil hydrology KW - Saturated hydraulic conductivity KW - Overland flow generation KW - Spatial patterns KW - Drainage network Y1 - 2013 U6 - https://doi.org/10.1016/j.geoderma.2012.11.002 SN - 0016-7061 VL - 195 IS - 169 SP - 1 EP - 11 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Loos, Martin A1 - Elsenbeer, Helmut T1 - Topographic controls on overland flow generation in a forest - An ensemble tree approach JF - Journal of hydrology N2 - Overland flow is an important hydrological pathway in many forests of the humid tropics. Its generation is subject to topographic controls at differing spatial scales. Our objective was to identify such controls on the occurrence of overland flow in a lowland tropical rainforest. To this end, we installed 95 overland flow detectors (OFDs) in four nested subcatchments of the Lutzito catchment on Barro Colorado Island, Panama, and monitored the frequency of overland flow occurrence during 18 rainfall events at each OFD location temporal frequency. For each such location, we derived three non-digital terrain attributes and 17 digital ones, of which 15 were based on Digital Elevation Models (DEMs) of three different resolutions. These attributes then served as input into a Random Forest ensemble tree model to elucidate the importance and partial and joint dependencies of topographic controls for overland flow occurrence. Lutzito features a high median temporal frequency in overland flow occurrence of 0.421 among OFD locations. However, spatial temporal frequencies of overland flow occurrence vary strongly among these locations and the subcatchments of Lutzito catchment. This variability is best explained by (1) microtopography, (2) coarse terrain sloping and (3) various measures of distance-to-channel, with the contribution of all other terrain attributes being small. Microtopographic features such as concentrated flowlines and wash areas produce highest temporal frequencies, whereas the occurrence of overland flow drops sharply for flow distances and terrain sloping beyond certain threshold values. Our study contributes to understanding both the spatial controls on overland flow generation and the limitations of terrain attributes for the spatially explicit prediction of overland flow frequencies. KW - Overland Bow KW - Tropical rainforest KW - Random Forest KW - Spatial scale KW - Digital Elevation Model KW - Topography Y1 - 2011 U6 - https://doi.org/10.1016/j.jhydrol.2011.08.002 SN - 0022-1694 VL - 409 IS - 1-2 SP - 94 EP - 103 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Germer, Sonja A1 - Elsenbeer, Helmut A1 - de Moraes, Jorge M. T1 - Throughfall and temporal trends of rainfall redistribution in an open tropical rainforest, south-western Amazonia (Rondônia, Brazil) Y1 - 2006 UR - http://www.hydrology-and-earth-system-sciences.net/index.html U6 - https://doi.org/10.5194/hess-10-383-2006 SN - 1027-5606 ER - TY - JOUR A1 - Zimmermann, Beate A1 - Elsenbeer, Helmut T1 - The near-surface hydrological consequences of disturbance and recovery : a simulation study N2 - Changes in soil hydraulic properties following ecosystem disturbances can become relevant for regional water cycles depending on the prevailing rainfall regime. In a tropical montane rainforest ecosystem in southern Ecuador, plot- scale investigations revealed that man-made disturbances were accompanied by a decrease in mean saturated hydraulic conductivity (Ks), whereas mean Ks of two different aged landslides was undistinguishable from the reference forest. Ks spatial structure weakened after disturbances in the topsoil. We used this spatial-temporal information combined with local rain intensities to assess the probability of impermeable soil layers under undisturbed, disturbed, and regenerating land-cover types. We furthermore compared the Ecuadorian man-made disturbance cycle with a similar land-use sequence in a tropical lowland rainforest region in Brazil. The studied montane rainforest is characterized by prevailing vertical flowpaths in the topsoil, whereas larger rainstorms in the study area potentially result in impermeable layers below 20 cm depth. In spite of the low frequency of such higher-intensity events, they transport a high portion of the annual runoff and may therefore significant for the regional water cycle. Hydrological flowpaths under two studied landslides are similar to the natural forest except for a somewhat higher probability of impermeable layer formation in the topsoil of the 2-year-old landslide. In contrast, human disturbances likely affect near-surface hydrology. Under a pasture and a young fallow, impermeable layers potentially develop already in the topsoil for larger rain events. A 10-year-old fallow indicates regeneration towards the original vertical flowpaths, though the land-use signal was still detectable. The consequences of land-cover change on near-surface hydrological behaviour are of similar magnitude in the tropical montane and the lowland rainforest region. This similarity can be explained by a more pronounced drop of soil permeability after pasture establishment in the montane rainforest region in spite of the prevailing much lower rain intensities. Y1 - 2009 UR - http://www.sciencedirect.com/science/journal/00221694 U6 - https://doi.org/10.1016/j.jhydrol.2008.10.016 SN - 0022-1694 ER - TY - JOUR A1 - Zimmermann, Beate A1 - Elsenbeer, Helmut A1 - de Moraes, Jorge M. T1 - The influence of land-use changes on soil hydraulic properties : implications for runoff generation Y1 - 2006 U6 - https://doi.org/10.1016/j.foreco.2005.10.070 SN - 0378-1127 ER - TY - JOUR A1 - Neill, Christopher A1 - Jankowski, KathiJo A1 - Brando, Paulo M. A1 - Coe, Michael T. A1 - Deegan, Linda A. A1 - Macedo, Marcia N. A1 - Riskin, Shelby H. A1 - Porder, Stephen A1 - Elsenbeer, Helmut A1 - Krusche, Alex V. T1 - Surprisingly Modest Water Quality Impacts From Expansion and Intensification of Large-Sscale Commercial Agriculture in the Brazilian Amazon-Cerrado Region JF - Tropical conservation science N2 - Large-scale commercial cropping of soybeans expanded in the tropical Amazon and Cerrado biomes of Brazil after 1990. More recently, cropping intensified from single-cropping of soybeans to double-cropping of soybeans with corn or cotton. Cropland expansion and intensification, and the accompanying use of mineral fertilizers, raise concerns about whether nutrient runoff and impacts to surface waters will be similar to those experienced in commercial cropland regions at temperate latitudes. We quantified water infiltration through soils, water yield, and streamwater chemistry in watersheds draining native tropical forest and single-and double-cropped areas on the level, deep, highly weathered soils where cropland expansion and intensification typically occurs. Although water yield increased four-fold from croplands, streamwater chemistry remained largely unchanged. Soil characteristics exerted important control over the movement of nitrogen (N) and phosphorus (P) into streams. High soil infiltration rates prevented surface erosion and movement of particulate P, while P fixation in surface soils restricted P movement to deeper soil layers. Nitrogen retention in deep soils, likely by anion exchange, also appeared to limit N leaching and export in streamwater from both single-and double-cropped watersheds that received nitrogen fertilizer. These mechanisms led to lower streamwater P and N concentrations and lower watershed N and P export than would be expected, based on studies from temperate croplands with similar cropping and fertilizer application practices. KW - water KW - quality KW - agriculture KW - intensification KW - impact Y1 - 2017 U6 - https://doi.org/10.1177/1940082917720669 SN - 1940-0829 VL - 10 PB - Sage Publ. CY - Thousand Oaks ER - TY - JOUR A1 - Zimmermann, Alexander A1 - Germer, Sonja A1 - Neill, Christopher A1 - Krusche, Alex V. A1 - Elsenbeer, Helmut T1 - Spatio-temporal patterns of throughfall and solute deposition in an open tropical rain forest Y1 - 2008 UR - http://www.sciencedirect.com/science/journal/00221694 U6 - https://doi.org/10.1016/j.jhydrol.2008.07.028 SN - 0022-1694 ER - TY - JOUR A1 - Zimmermann, Beate A1 - Elsenbeer, Helmut T1 - Spatial and temporal variability of soil saturated hydraulic conductivity in gradients of disturbance Y1 - 2008 UR - http://www.sciencedirect.com/science/journal/00221694 U6 - https://doi.org/10.1016/j.jhydrol.2008.07.027 SN - 0022-1694 ER -