@article{BrandtGlemnitzSchroeder2017, author = {Brandt, Karoline and Glemnitz, M. and Schroeder, Boris}, title = {The impact of crop parameters and surrounding habitats on different pollinator group abundance on agricultural fields}, series = {Agriculture, ecosystems \& environment : an international journal for scientific research on the relationship of agriculture and food production to the biosphere}, volume = {243}, journal = {Agriculture, ecosystems \& environment : an international journal for scientific research on the relationship of agriculture and food production to the biosphere}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0167-8809}, doi = {10.1016/j.agee.2017.03.009}, pages = {55 -- 66}, year = {2017}, abstract = {Pollination is a key ecosystem service. Pollinators, however, are in decline and their service is increasingly threatened. The decline is driven by several factors, most of which are related to agricultural management. However, the complexity of the landscape system, consisting of both cropped and non cropped areas, makes it difficult to address or even quantify the role of farming practices in pollinator abundance. Therefore, the aim of this paper is to improve our understanding of the relationships between pollinator abundance and their habitat use. We intend to identify and quantify the driving environmental factors that determine pollinator abundance in agricultural landscapes on the crop and landscape scale. These information helps us to design algorithms that can be used as a basis for predicting pollinator abundance on agricultural fields. To integrate varying environmental conditions data sampling was performed on farms in three different regions in Germany. Pollinators were classified into different groups with three aggregation levels. We observed crop parameters as well as landscape parameters in the areas surrounding fields in addition to temporal aspects. Generalized linear models (GLMs) were then calculated. Our results showed that both crop and landscape parameters affect pollinator abundance on agricultural fields. However, the explanatory power of the included parameters varied strongly among the particular pollinator groups and between aggregation levels. Furthermore, differentiation between species groups improves the explanatory power compared to models that are more aggregated. We also found that the temporal match between main activity periods of the particular pollinator groups and resource supply by the crop species is a key factor when analysing pollinator abundance. In conclusion, we demonstrated that the assessment and support of pollination services should be carried out with regard to individual pollinator groups. When studying pollinator abundance, the crop as well as the landscape scale should be addressed. A range of different habitat requirements and different activity periods of the pollinator groups must be covered to maintain pollination services, and therefore both diverse landscapes and diverse crop rotations are of crucial importance. (C) 2017 Elsevier B.V. All rights reserved.}, language = {en} } @article{CarusPaulSchroeder2016, author = {Carus, Jana and Paul, Maike and Schroeder, Boris}, title = {Vegetation as self-adaptive coastal protection: Reduction of current velocity and morphologic plasticity of a brackish marsh pioneer}, series = {Ecology and evolution}, volume = {6}, journal = {Ecology and evolution}, publisher = {Wiley}, address = {Hoboken}, issn = {2045-7758}, doi = {10.1002/ece3.1904}, pages = {1579 -- 1589}, year = {2016}, abstract = {By reducing current velocity, tidal marsh vegetation can diminish storm surges and storm waves. Conversely, currents often exert high mechanical stresses onto the plants and hence affect vegetation structure and plant characteristics. In our study, we aim at analysing this interaction from both angles. On the one hand, we quantify the reduction of current velocity by Bolboschoenus maritimus, and on the other hand, we identify functional traits of B. maritimus' ramets along environmental gradients. Our results show that tidal marsh vegetation is able to buffer a large proportion of the flow velocity at currents under normal conditions. Cross-shore current velocity decreased with distance from the marsh edge and was reduced by more than 50\% after 15 m of vegetation. We were furthermore able to show that plants growing at the marsh edge had a significantly larger diameter than plants from inside the vegetation. We found a positive correlation between plant thickness and cross-shore current which could provide an adaptive value in habitats with high mechanical stress. With the adapted morphology of plants growing at the highly exposed marsh edge, the entire vegetation belt is able to better resist the mechanical stress of high current velocities. This self-adaptive effect thus increases the ability of B. maritimus to grow and persist in the pioneer zone and may hence better contribute to ecosystem-based coastal protection by reducing current velocity.}, language = {en} } @article{vanSchaikPalmKlausetal.2016, author = {van Schaik, Loes and Palm, Juliane and Klaus, Julian and Zehe, Erwin and Schroeder, Boris}, title = {Potential effects of tillage and field borders on within-field spatial distribution patterns of earthworms}, series = {Biological chemistry}, volume = {228}, journal = {Biological chemistry}, publisher = {De Gruyter}, address = {Berlin}, issn = {0167-8809}, doi = {10.1016/j.agee.2016.05.015}, pages = {82 -- 90}, year = {2016}, abstract = {Earthworms play a key role in regulating soil ecosystem functions and services. The small scale variability in earthworm abundance is often found to be very high, which is a problem for representative sampling of earthworm abundance at larger scales. In agricultural fields, soil tillage may influence both the average earthworm abundance as well as the spatial distribution of earthworms. Therefore we studied the abundance and spatial pattern of the different ecological earthworm types, i.e. endogeic, epigeic and anecic earthworms, in four agricultural fields differing in soil tillage (two fields with regular tillage and two fields with conservation tillage) and surrounding land use (other cropped fields or apple orchard and forest). To this aim we sampled earthworms on a total number of 430 plots (50 x 50 cm(2)) using a combination of extraction with mustard solution and hand sorting. The results exhibit large differences in average earthworm abundance between the four fields. Only one of the two fields with conservation tillage had a comparatively very high overall abundance of earthworms. Furthermore, we found a high spatial variability of earthworms within the field scale often exhibiting a patchy distribution. We detected a trend of decreasing earthworm abundances from the field border into the field for different earthworm groups on each of the fields. In three fields with low total earthworm abundance (and only very few epigeic earthworms) there was a short scale autocorrelation with ranges varying strongly for the endogeic earthworms (37.9 m, 62.6 m, and 85.2 m) compared to anecic earthworms (19.8 m, 22.8 m, and 27.4 m). In the field with high abundance, after trend removal, the variogram models for anecic and endogeic earthworms were rejected based on their negative explained variances. On this field, we found only a short scale autocorrelation for the epigeic earthworms with a range of 143 m. Based on these results it seems that ploughing alone cannot explain the differences in abundance and range of autocorrelation found on the four fields. The trend of strongly decreasing earthworm abundance from the field border into the field in the one field with high abundance does indicate that the field border or surrounding land use may also influence the recolonization of fields, but more research is required to provide further evidence for this hypothesis. Due to the very different patterns of earthworm distributions in the fields it remains difficult to recommend an optimal number and distance of samples to obtain a representative earthworm abundance for the field scale. (C) 2016 Elsevier B.V. All rights reserved.}, language = {en} } @article{ZeheEhretPfisteretal.2014, author = {Zehe, E. and Ehret, U. and Pfister, L. and Blume, Theresa and Schroeder, Boris and Westhoff, M. and Jackisch, C. and Schymanski, Stanislauv J. and Weiler, M. and Schulz, K. and Allroggen, Niklas and Tronicke, Jens and van Schaik, Loes and Dietrich, Peter and Scherer, U. and Eccard, Jana and Wulfmeyer, Volker and Kleidon, Axel}, title = {HESS Opinions: From response units to functional units: a thermodynamic reinterpretation of the HRU concept to link spatial organization and functioning of intermediate scale catchments}, series = {Hydrology and earth system sciences : HESS}, volume = {18}, journal = {Hydrology and earth system sciences : HESS}, number = {11}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1027-5606}, doi = {10.5194/hess-18-4635-2014}, pages = {4635 -- 4655}, year = {2014}, abstract = {According to Dooge (1986) intermediate-scale catchments are systems of organized complexity, being too organized and yet too small to be characterized on a statistical/conceptual basis, but too large and too heterogeneous to be characterized in a deterministic manner. A key requirement for building structurally adequate models precisely for this intermediate scale is a better understanding of how different forms of spatial organization affect storage and release of water and energy. Here, we propose that a combination of the concept of hydrological response units (HRUs) and thermodynamics offers several helpful and partly novel perspectives for gaining this improved understanding. Our key idea is to define functional similarity based on similarity of the terrestrial controls of gradients and resistance terms controlling the land surface energy balance, rainfall runoff transformation, and groundwater storage and release. This might imply that functional similarity with respect to these specific forms of water release emerges at different scales, namely the small field scale, the hillslope, and the catchment scale. We thus propose three different types of "functional units" - specialized HRUs, so to speak - which behave similarly with respect to one specific form of water release and with a characteristic extent equal to one of those three scale levels. We furthermore discuss an experimental strategy based on exemplary learning and replicate experiments to identify and delineate these functional units, and as a promising strategy for characterizing the interplay and organization of water and energy fluxes across scales. We believe the thermodynamic perspective to be well suited to unmask equifinality as inherent in the equations governing water, momentum, and energy fluxes: this is because several combinations of gradients and resistance terms yield the same mass or energy flux and the terrestrial controls of gradients and resistance terms are largely independent. We propose that structurally adequate models at this scale should consequently disentangle driving gradients and resistance terms, because this optionally allow sequifinality to be partly reduced by including available observations, e. g., on driving gradients. Most importantly, the thermodynamic perspective yields an energy-centered perspective on rainfall-runoff transformation and evapotranspiration, including fundamental limits for energy fluxes associated with these processes. This might additionally reduce equifinality and opens up opportunities for testing thermodynamic optimality principles within independent predictions of rainfall-runoff or land surface energy exchange. This is pivotal to finding out whether or not spatial organization in catchments is in accordance with a fundamental organizing principle.}, language = {en} } @article{SchibalskiLehtonenSchroeder2014, author = {Schibalski, Anett and Lehtonen, Aleksi and Schroeder, Boris}, title = {Climate change shifts environmental space and limits transferability of treeline models}, series = {Ecography : pattern and diversity in ecology ; research papers forum}, volume = {37}, journal = {Ecography : pattern and diversity in ecology ; research papers forum}, number = {4}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {0906-7590}, doi = {10.1111/j.1600-0587.2013.00368.x}, pages = {321 -- 335}, year = {2014}, abstract = {Our study aims at gaining insights into the processes determining the current treeline dynamics in Finnish Lapland. Using forest surveys conducted in 1978 and 2003 we modelled the occurrence and abundance of three dominant tree species in Finnish Lapland, i.e. Pinus sylvestris, Picea abies and Betula pubescens, with boosted regression trees. We assessed the importance of climatic, biotic and topographic variables in predicting tree occurrence and abundance based on their relative importance and response curves. We compared temporal and spatial transferability by using an extended transferability index. Site fertility, the abundance of co-occurring species and growing degree days were generally the most important predictors for both occurrence and abundance across all species and datasets. Climatic predictors were more important for modelling occurrences than for modelling abundances. Occurrence models were able to reproduce the observed treeline pattern within one time period or region. Abundance models underestimated basal area but captured the general pattern of low and high values. Model performance as well as transferability differed considerably between species and datasets. Pinus sylvestris was modelled more successfully than P. abies and B. pubescens. Generally, spatial transferability was greater than temporal transferability. Comparing the environmental space between datasets revealed that transferring models means extrapolating to novel environments, providing a plausible explanation for limited transferability. Our study illustrates how climate change can shift the environmental space and lead to limited model transferability. We identified non-climatic factors to be important in predicting the distribution of dominant tree species, contesting the widespread assumption of climatically induced range expansion.}, language = {en} } @article{vanSchaikPalmKlausetal.2014, author = {van Schaik, Loes and Palm, Juliane and Klaus, Julian and Zehe, Erwin and Schroeder, Boris}, title = {Linking spatial earthworm distribution to macropore numbers and hydrological effectiveness}, series = {Ecohydrology : ecosystems, land and water process interactions, ecohydrogeomorphology}, volume = {7}, journal = {Ecohydrology : ecosystems, land and water process interactions, ecohydrogeomorphology}, number = {2}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {1936-0584}, doi = {10.1002/eco.1358}, pages = {401 -- 408}, year = {2014}, abstract = {Due to its high spatial and temporal variability, preferential flow is difficult to measure and quantify. Earthworms create macropores that provide common pathways for preferential flow. Therefore in this article, we link earthworm abundance to macropore numbers and hydrological effectiveness, with the future aim to use species distribution models of earthworms for the spatial parameterization of preferential flow. Earthworms are generally categorized into three ecological types with varying burrowing behaviour, resulting in a different impact on soil hydrological processes. Therefore, we studied the relationships between the abundance of the earthworm ecological types and macropores of different size classes and in different soil depths. The abundance and biomass of earthworms were well correlated to different sizes of macropores in different soil depths. This is mainly the case for the larger, vertically oriented macropores (>6mm diameter), which are generally connected to the soil surface and hydrologically most effective. The correlation of total earthworm biomass and macropores ranges from 072 to 089 for different soil depths. Although there is quite some variation in infiltration patterns, infiltration from macropores into the matrix is profile-specific, as it varies strongly between profiles, but not within one profile. Macropore coating seems to have a larger effect on this macropore matrix interaction than the soil physical properties of the matrix. Although the amount of macropores and their effectiveness are clearly related to the earthworm distribution, the variation in infiltration from macropores to soil matrix should be further studied.}, language = {en} } @article{KlausZeheElsneretal.2014, author = {Klaus, Julian and Zehe, Erwin and Elsner, Martin and Palm, Juliane and Schneider, Dorothee and Schroeder, Boris and Steinbeiss, Sibylle and van Schaik, Loes and West, Stephanie}, title = {Controls of event-based pesticide leaching in natural soils: A systematic study based on replicated field scale irrigation experiments}, series = {Journal of hydrology}, volume = {512}, journal = {Journal of hydrology}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0022-1694}, doi = {10.1016/j.jhydrol.2014.03.020}, pages = {528 -- 539}, year = {2014}, abstract = {Tile drains strongly influence the water cycle in agricultural catchment in terms of water quantity and quality. The connectivity of preferential flow to tile drains can create shortcuts for rapid transport of solutes into surface waters. The leaching of pesticides can be linked to a set of main factors including, rainfall characteristics, soil moisture, chemical properties of the pesticides, soil properties, and preferential flow paths. The connectivity of the macropore system to the tile drain is crucial for pesticide leaching. Concurring influences of the main factors, threshold responses and the role of flow paths are still poorly understood. The objective of this study is to investigate these influences by a replica series of three irrigation experiments on a tile drain field site using natural and artificial tracers together with applied pesticides. We found a clear threshold behavior in the initialization of pesticide transport that was different between the replica experiments. Pre-event soil water contributed significantly to the tile drain flow, and creates a flow path for stored pesticides from the soil matrix to the tile drain. This threshold is controlled by antecedent soil moisture and precipitation characteristics, and the interaction between the soil matrix and preferential flow system. Fast transport of pesticides without retardation and the remobilization could be attributed to this threshold and the interaction between the soil matrix and the preferential flow system. Thus, understanding of the detailed preferential flow processes clearly enhances the understanding of pesticide leaching on event and long term scale, and can further improve risk assessment and modeling approaches. (C) 2014 Elsevier B.V. All rights reserved.}, language = {en} } @article{KrauseBuseMaternetal.2011, author = {Krause, Rolf Harald and Buse, Joern and Matern, Andrea and Schroeder, Boris and Haerdtle, Werner and Assmann, Thorsten}, title = {Eresus kollari (Araneae: Eresidae) calls for heathland management}, series = {The Journal of arachnology}, volume = {39}, journal = {The Journal of arachnology}, number = {3}, publisher = {American Arachnological Society}, address = {College Park}, issn = {0161-8202}, pages = {384 -- 392}, year = {2011}, abstract = {Northwest Europe's largest heather-dominated sandy habitats are located in the nature reserve Luneburger Heide, Germany. Yet, even these appear to be losing their ability to support some of their stenotopic species such as the ladybird spider, Eresus kollari Rossi 1846, and are thus becoming increasingly important for the preservation of these species. The habitat requirements of this endangered spider species were investigated in order to obtain data that will help stabilize the last remnants of the species' population in northwest Germany. Several heathland habitats were surveyed by pitfall trapping during the mate-search period of the males. Two statistical methods were applied: logistic regression and boosted regression trees (BRT). Both methods showed that three habitat variables are of prime relevance in predicting the occurrence of E. kollari: a) thickness of the organic layer (a negative effect), b) soil temperature at a depth of 10 cm, and c) Calluna cover in the herb layer (both have positive effect). Our results show that choppering (removing above-ground biomass and most of O-layer) and burning are likely appropriate heathland management measures for the conservation of E. kollari. Such measures improve the species' habitat quality by creating a heterogenic (small-scaled) heathland structure with suitable microhabitats. As Calluna heathlands show a clear senescence of the dominant heather, it is essential that those habitat patches be conserved. Further measures, such as transfer experiments, are recommended.}, language = {en} } @article{MaerkerPelacaniSchroeder2011, author = {Maerker, Michael and Pelacani, Samanta and Schroeder, Boris}, title = {A functional entity approach to predict soil erosion processes in a small Plio-Pleistocene Mediterranean catchment in Northern Chianti, Italy}, series = {Geomorphology : an international journal on pure and applied geomorphology}, volume = {125}, journal = {Geomorphology : an international journal on pure and applied geomorphology}, number = {4}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0169-555X}, doi = {10.1016/j.geomorph.2010.10.022}, pages = {530 -- 540}, year = {2011}, abstract = {In this paper we evaluate different methods to predict soil erosion processes. We derived different layers of predictor variables for the study area in the Northern Chianti, Italy, describing the soil-lithologic complex, land use, and topographic characteristics. For a subcatchment of the Orme River, we mapped erosion processes by interpreting aerial photographs and field observations. These were classified as erosional response units (ERU), i.e. spatial areas of homogeneous erosion processes. The ERU were used as the response variable in the soil erosion modelling process. We applied two models i) bootstrap aggregation (Random Forest: RF), and ii) stochastic gradient boosting (TreeNet: TN) to predict the potential spatial distribution of erosion processes for the entire Orme River catchment. The models are statistically evaluated using training data and a set of performance parameters such as the area under the receiver operating characteristic curve (AUC), Cohen's Kappa, and pseudo R2. Variable importance and response curves provide further insight into controlling factors of erosion. Both models provided good performance in terms of classification and calibration; however, TN outperformed RF. Similar classes such as active and inactive landslides can be discriminated and well interpreted by considering response curves and relative variable importance. The spatial distribution of the predicted erosion susceptibilities generally follows topographic constraints and is similar for both models. Hence, the model-based delineation of ERU on the basis of soil and terrain information is a valuable tool in geomorphology; it provides insights into factors controlling erosion processes and may allow the extrapolation and prediction of erosion processes in unsurveyed areas.}, language = {en} } @article{LoefflerAnschlagBakeretal.2011, author = {Loeffler, J{\"o}rg and Anschlag, Kerstin and Baker, Barry and Finch, Oliver-D. and Diekkrueger, Bernd and Wundram, Dirk and Schroeder, Boris and Pape, Roland and Lundberg, Anders}, title = {Mountain ecosystem response to global change}, series = {Erdkunde : archive for scientific geography}, volume = {65}, journal = {Erdkunde : archive for scientific geography}, number = {2}, publisher = {Geographisches Inst., Univ. Bonn}, address = {Goch}, issn = {0014-0015}, doi = {10.3112/erdkunde.2011.02.06}, pages = {189 -- 213}, year = {2011}, abstract = {Mountain ecosystems are commonly regarded as being highly sensitive to global change. Due to the system complexity and multifaceted interacting drivers, however, understanding current responses and predicting future changes in these ecosystems is extremely difficult. We aim to discuss potential effects of global change on mountain ecosystems and give examples of the underlying response mechanisms as they are understood at present. Based on the development of scientific global change research in mountains and its recent structures, we identify future research needs, highlighting the major lack and the importance of integrated studies that implement multi-factor, multi-method, multi-scale, and interdisciplinary research.}, language = {en} }