Spatial and temporal occurrence of preferential flow in a forested headwater catchment

The highly dynamic nature of preferential flow in time and space makes it challenging to identify and analyze its occurrence at the catchment scale. Novel analysis methods using soil moisture sensor response times offer an opportunity to investigate catchment-wide controls on preferential flow. The aim of this study was to identify factors that control preferential flow occurrence based on 3-year soil moisture monitoring using a wireless sensor network in the Wüstebach catchment, Germany. At 101 locations, the sensor response times at three depths (5, 20, and 50 cm) were classified into one of four classes: (1) non-sequential preferential flow, (2) velocity-based preferential flow, (3) sequential flow, and (4) no response. A conceptual model, postulating that preferential flow in the Wüstebach catchment is dominated by differences in soil type, landscape position, and rainfall input, was proposed for hypothesis testing. To test the conceptual model, the classification results were combined with spatial and event-based data to understand and identify controlling factors. Spatial parameters consisted of hydrological, topographical, and soil physical and chemical parameters. Temporal factors included precipitation characteristics and antecedent soil moisture conditions. The conceptual model as proposed could only be partly confirmed. Event-based occurrence of preferential flow was highly affected by precipitation amount, with a nearly catchment-wide preferential response during large storm events. During intermediate events, preferential flow was controlled by small-scale heterogeneity, instead of showing catchment-wide patterns. The effect of antecedent catchment wetness on the occurrence of preferential flow was generally less profound, although a clear negative relationship was found for precipitation events with more than 25 mm. It was found that spatial occurrence of preferential flow was however governed by small-scale soil and biological features and local processes, and showed no obvious relationship with any of the selected spatial parameters. Overall, the results demonstrate that sensor response time analysis can offer innovative insights into the spatial–temporal interrelationship of preferential flow occurrence

Changes in measured spatiotemporal patterns of hydrological response after partial deforestation in a headwater catchment

Although the hydrological effects of land use change have been studied extensively, only few datasets are available to accurately describe, model, and predict detailed changes in spatiotemporal patterns of hydrological fluxes and states due to land use change. The Wüstebach catchment within the TERENO (TERrestrial Environmental Observatories) network in Germany provides a unique monitoring setup to measure the major components of the water balance (evapotranspiration, discharge, precipitation) and the spatiotemporal distribution of soil moisture before and after a partial deforestation. Here, we present five years of measured hydrological data, including all major water budget components three years before and two years after a partial deforestation. A data-driven approach was used to understand changes and related feedback mechanisms in spatiotemporal hydrological response patterns. As expected from earlier studies, the partial deforestation caused a decrease in evapotranspiration and an increase in discharge. A closer look at the high resolution datasets revealed new insights in the intra-annual variability and relationship between the water balance components. The overall decrease in evapotranspiration caused a large increase in soil water storage in the deforested region, especially during the summer period, which in turn caused an increase in the frequency of high discharge in the same period. Although the evapotranspiration in the forested region was larger on average, the deforested region showed a higher evapotranspiration during part of the summer period. This could be related to wetter conditions in the deforested area, accompanied with the emergence of grass vegetation. At the same time, wetter soil moisture conditions in the deforested area increased the spatial variance of soil moisture in the summer and therewith altered the relationship between spatial mean and variance. Altogether, this study illustrates that detailed spatiotemporal monitoring can provide new insights into the hydrological effects of partial deforestation

A Dataset for Three-Dimensional Distribution of 39 Elements Including Plant Nutrients and Other Metals and Metalloids in the Soils of a Forested Headwater Catchment

Quantification and evaluation of elemental distribution in forested ecosystems are key requirements to understand element fluxes and their relationship with hydrological and biogeochemical processes in the system. However, datasets supporting such a study on the catchment scale are still limited. Here we provide a dataset comprising spatially highly resolved distributions of 39 elements in soil profiles of a small forested headwater catchment in western Germany (http://teodoor.icg.kfa-juelich.de/ibg3searchportal2/dispatch?searchparams=freetext-Wuestebach&metadata.detail.view.id=7d37ae00-20f6-408e-8660-33bfba07c869) to gain a holistic picture of the state and fluxes of elements in the catchment. The elements include both plant nutrients and other metals and metalloids that were predominately derived from lithospheric or anthropogenic inputs, thereby allowing us to not only capture the nutrient status of the catchment but to also estimate the functional development of the ecosystem. Soil samples were collected at high lateral resolution (≤60 m), and element concentrations were determined vertically for four soil horizons (L/Of, Oh, A, B). From this, a three-dimensional view of the distribution of these elements could be established with high spatial resolution on the catchment scale in a temperate natural forested ecosystem. The dataset can be combined with other datasets and studies of the TERENO (Terrestrial Environmental Observatories) Data Discovery Portal (http://teodoor.icg.kfa-juelich.de/ibg3searchportal2/index.jsp) to reveal elemental fluxes, establish relations between elements and other soil properties, and/or as input for modeling elemental cycling in temperate forested ecosystems

A terrestrial observatory approach to the integrated investigation of the effects of deforestation on water, energy, and matter fluxes

Integrated observation platforms have been set up to investigate consequences of global change within a terrestrial network of observatories (TERENO) in Germany. The aim of TERENO is to foster the understanding of water, energy, and matter fluxes in terrestrial systems, as well as their biological and physical drivers. Part of the Lower Rhine Valley-Eifel observatory of TERENO is located within the Eifel National Park. Recently, the National Park forest management started to promote the natural regeneration of near-natural beech forest by removing a significant proportion of the spruce forest that was established for timber production after World War II. Within this context, the effects of such a disturbance on forest ecosystem functioning are currently investigated in a deforestation experiment in the Wüstebach catchment, which is one of the key experimental research sites within the Lower Rhine Valley-Eifel observatory. Here, we present the integrated observation system of the Wüstebach test site to exemplarily demonstrate the terrestrial observatory concept of TERENO that allows for a detailed monitoring of changes in hydrological and biogeochemical states and fluxes triggered by environmental disturbances. We present the observation platforms and the soil sampling campaign, as well as preliminary results including an analysis of data consistency. We specifically highlight the capability of integrated datasets to enable improved process understanding of the post-deforestation changes in ecosystem functioning